WorldWideScience

Sample records for thermal neutron absorption

  1. Volumetric Heat Generation and Consequence Raise in Temperature Due to Absorption of Neutrons from Thermal up to 14.9 MeV Energies

    CERN Document Server

    Massoud, E

    2003-01-01

    In this work, the heat generation rate and the consequence rise in temperature due to absorption of all neutrons from thermal energies (E<0.025) up to 14.9 MeV in water, paraffin wax, ordinary concrete and heavy concrete and heavy concrete as some selected hydrogenous materials are investigated. The neutron flux distributions are calculated by both ANISN-code and three group method in which the fast neutrons are expressed by the removal cross section concept while the other two groups (epithermal and thermal) are treated by the diffusion equation. The heat generation can be calculated from the neutron macroscopic absorption of each material or mixture multiplied by the corresponding neutron fluxes. The rise in temperature is then calculated by using both of the heat generation and the thermal conductivity of the selected materials. Some results are compared with the available experimental and theoretical data and a good agreement is achieved.

  2. Accuracy of the thermal neutron absorption cross section measurements (based on examples of selected pulsed beam methods); Dokladnosc pomiarow przekroju czynnego absorpcji neutronow termicznych (na przykladzie wybranych metod impulsowych)

    Energy Technology Data Exchange (ETDEWEB)

    Krynicka, E. [The H. Niewodniczanski Inst. of Nuclear Physics, Cracow (Poland)

    1997-12-31

    The problem of accuracy of the thermal neutron macroscopic absorption cross section determination is discussed on examples of selected measurement methods which use non-stationary neutron fields. The computer simulation method elaborated by the author is presented as a procedure for estimating the standard deviation of the measured absorption cross section. The computer simulation method presented can be easily utilized to estimate the accuracy of measurement of various physical magnitudes. (author) 46 refs, 3 figs, 1 tab

  3. THERMAL NEUTRONIC REACTOR

    Science.gov (United States)

    Spinrad, B.I.

    1960-01-12

    A novel thermal reactor was designed in which a first reflector formed from a high atomic weight, nonmoderating material is disposed immediately adjacent to the reactor core. A second reflector composed of a moderating material is disposed outwardly of the first reflector. The advantage of this novel reflector arrangement is that the first reflector provides a high slow neutron flux in the second reflector, where irradiation experiments may be conducted with a small effect on reactor reactivity.

  4. A proposal on evaluation method of neutron absorption performance to substitute conventional neutron attenuation test

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Je Hyun; Shim, Chang Ho [Dept. of Nuclear Engineering, Hanyang University, Seoul (Korea, Republic of); Kim, Sung Hyun [Nuclear Fuel Cycle Waste Treatment Research Division, Research Reactor Institute, Kyoto University, Osaka (Japan); Choe, Jung Hun; Cho, In Hak; Park, Hwan Seo [Ionizing Radiation Center, Nuclear Fuel Cycle Waste Treatment Research Division, Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of); Park, Hyun Seo; Kim, Jung Ho; Kim, Yoon Ho [Ionizing Radiation Center, Korea Research Institute of Standards and Science, Daejeon (Korea, Republic of)

    2016-12-15

    For a verification of newly-developed neutron absorbers, one of guidelines on the qualification and acceptance of neutron absorbers is the neutron attenuation test. However, this approach can cause a problem for the qualifications that it cannot distinguish how the neutron attenuates from materials. In this study, an estimation method of neutron absorption performances for materials is proposed to detect both direct penetration and back-scattering neutrons. For the verification of the proposed method, MCNP simulations with the experimental system designed in this study were pursued using the polyethylene, iron, normal glass and the vitrified form. The results show that it can easily test neutron absorption ability using single absorber model. Also, from simulation results of single absorber and double absorbers model, it is verified that the proposed method can evaluate not only the direct thermal neutrons passing through materials, but also the scattered neutrons reflected to the materials. Therefore, the neutron absorption performances can be accurately estimated using the proposed method comparing with the conventional neutron attenuation test. It is expected that the proposed method can contribute to increase the reliability of the performance of neutron absorbers.

  5. Neutron absorption constraints on the composition of 4 Vesta

    Science.gov (United States)

    Prettyman, Thomas H.; Mittlefehldt, David W.; Yamashita, Naoyuki; Beck, Andrew W.; Feldman, William C.; Hendricks, John S.; Lawrence, David J.; McCoy, Timothy J.; McSween, Harry Y.; Paplowski, Patrick N.; Reedy, Robert C.; Toplis, Michael J.; Le Corre, Lucille; Mizzon, Hugau; Reddy, Vishnu; Titus, Timothy N.; Raymond, Carol A.; Russell, Christopher T.

    2013-01-01

    Global maps of the macroscopic thermal neutron absorption cross section of Vesta's regolith by the Gamma Ray and Neutron Detector (GRaND) on board the NASA Dawn spacecraft provide constraints on the abundance and distribution of Fe, Ca, Al, Mg, and other rock-forming elements. From a circular, polar low-altitude mapping orbit, GRaND sampled the regolith to decimeter depths with a spatial resolution of about 300 km. At this spatial scale, the variation in neutron absorption is about seven times lower than that of the Moon. The observed variation is consistent with the range of absorption for howardite whole-rock compositions, which further supports the connection between Vesta and the howardite, eucrite, and diogenite meteorites. We find a strong correlation between neutron absorption and the percentage of eucritic materials in howardites and polymict breccias, which enables petrologic mapping of Vesta's surface. The distribution of basaltic eucrite and diogenite determined from neutron absorption measurements is qualitatively similar to that indicated by visible and near infrared spectroscopy. The Rheasilvia basin and ejecta blanket has relatively low absorption, consistent with Mg-rich orthopyroxene. Based on a combination of Fe and neutron absorption measurements, olivine-rich lithologies are not detected on the spatial scales sampled by GRaND. The sensitivity of GRaND to the presence of mantle material is described and implications for the absence of an olivine signature are discussed. High absorption values found in Vesta's “dark” hemisphere, where exogenic hydrogen has accumulated, indicate that this region is richer in basaltic eucrite, representative of Vesta's ancient upper crust.

  6. High-dose neutron irradiation of MgAl{sub 2}O{sub 4} spinel: effects of post-irradiation thermal annealing on EPR and optical absorption

    Energy Technology Data Exchange (ETDEWEB)

    Ibarra, A. [EURATOM/CIEMAT Fusion Association, Inst. Investigacion Basica, Av. Complutense, 22, E-28040 Madrid (Spain)]. E-mail: angel.ibarra@ciemat.es; Bravo, D. [Departamento de Fisica de Materiales, Facultad de Ciencias (C-IV), Universidad Autonoma de Madrid, Cantoblanco, E-28049 Madrid (Spain); Lopez, F.J. [Departamento de Fisica de Materiales, Facultad de Ciencias (C-IV), Universidad Autonoma de Madrid, Cantoblanco, E-28049 Madrid (Spain); Garner, F.A. [Pacific Northwest National Laboratory, Richland, WA (United States)

    2005-02-01

    Electron paramagnetic resonance (EPR) and optical absorption spectra were measured during thermal annealing of stoichiometric MgAl{sub 2}O{sub 4} spinel that was previously irradiated in the Materials Open Test Assembly in the Fast Flux Test Facility (FFTF/MOTA) at {approx}680 K to {approx}50 dpa. Both F and F{sup +} centres are to persist up to very high temperatures (over 1000 K) suggesting the operation of an annealing mechanism controlled by the thermal stability of extended defects. Using X-ray irradiation following the different annealing steps it was shown that an optical absorption band at 37,000 cm{sup -1} is related to a sharp EPR band at g = 2.0005 and that the defect causing these effects is the F{sup +} centre.

  7. Thermal neutron scattering evaluation framework

    Science.gov (United States)

    Chapman, Chris; Leal, Luiz; Rahnema, Farzad; Danon, Yaron; Arbanas, Goran

    2017-09-01

    A neutron scattering kernel data evaluation framework for computation of model-dependent predictions and their uncertainties is outlined. In this framework, model parameters are fitted to double-differential cross section measurements and their uncertainties. For convenience, the initial implementation of this framework uses the molecular dynamics model implemented in the GROMACS code. It is applied to light water using the TIP4P/2005f interaction model. These trajectories computed by GROMACS are then processed using nMOLDYN to compute the density of states, which is then used to calculate the scattering kernel using the Gaussian approximation. Double differential cross sections computed from the scattering kernel are then fitted to double-differential scattering data measured at the Spallation Neutron Source detector at Oak Ridge National Laboratory. The fitting procedure is designed to yield optimized model-parameters and their uncertainties in the form of a covariance matrix, from which new evaluations of thermal neutron scattering kernel will be generated. The Unified Monte Carlo method will be used to fit the simulation data to the experimental data.

  8. 6Li foil thermal neutron detector

    Energy Technology Data Exchange (ETDEWEB)

    Ianakiev, Kiril D [Los Alamos National Laboratory; Swinhoe, Martyn T [Los Alamos National Laboratory; Favalli, Andrea [Los Alamos National Laboratory; Chung, Kiwhan [Los Alamos National Laboratory; Macarthur, Duncan W [Los Alamos National Laboratory

    2010-01-01

    In this paper we report on the design of a multilayer thermal neutron detector based on {sup 6}Li reactive foil and thin film plastic scintillators. The {sup 6}Li foils have about twice the intrinsic efficiency of {sup 10}B films and about four times higher light output due to a unique combination of high energy of reaction particles, low self absorption, and low ionization density of tritons. The design configuration provides for double sided readout of the lithium foil resulting in a doubling of the efficiency relative to a classical reactive film detector and generating a pulse height distribution with a valley between neutron and gamma signals similar to {sup 3}He tubes. The tens of microns thickness of plastic scintillator limits the energy deposited by gamma rays, which provides the necessary neutron/gamma discrimination. We used MCNPX to model a multilayer Li foil detector design and compared it with the standard HLNCC-II (18 {sup 3}He tubes operated at 4 atm). The preliminary results of the {sup 6}Li configuration show higher efficiency and one third of the die-away time. These properties, combined with the very short dead time of the plastic scintillator, offer the potential of a very high performance detector.

  9. Thermal neutron shield and method of manufacture

    Science.gov (United States)

    Brindza, Paul Daniel; Metzger, Bert Clayton

    2013-05-28

    A thermal neutron shield comprising concrete with a high percentage of the element Boron. The concrete is least 54% Boron by weight which maximizes the effectiveness of the shielding against thermal neutrons. The accompanying method discloses the manufacture of Boron loaded concrete which includes enriching the concrete mixture with varying grit sizes of Boron Carbide.

  10. Instrumentation to handle thermal polarized neutron beams

    OpenAIRE

    Kraan, W.H.

    2004-01-01

    In this thesis we investigate devices needed to handle the polarization of thermal neutron beams: Ï/2-flippers (to start/stop Larmor precession) and Ï-flippers (to reverse polarization/precession direction) and illustrate how these devices are used to investigate the properties of matter and of the neutron. The central theme is: demonstration - for the full thermal spectrum - of a special mode of Larmor precession (called "zero-field"-precession) over the neutron beam path length between two ...

  11. The thermal neutron facility HOTNES: theoretical design.

    Science.gov (United States)

    Bedogni, R; Pietropaolo, A; Gomez-Ros, J M

    2017-09-01

    HOTNES (HOmogeneous Thermal NEutron Source) is a thermal neutron irradiation facility with extended and very uniform irradiation area. A (241)Am-B radionuclide neutron source with nominal strenght 3.5×10(6) s(-1) is located on bottom of a large cylindrical cavity (30cm diameter, 70cm in height) delimited by polyethylene walls. The upper part of this volume (30cm diameter, 40cm in height) is used to irradiate samples. A polyethylene cylinder, acting as shadowing object, prevents fast neutrons to directly reach the irradiation volume. Indeed neutrons can only reach the irradiation volume after multiple scattering with the cavity walls. The facility was designed trough extensive calculations with MCNPX. Irradiation planes are disks with 30cm diameter, centred on the cavity axis, and parallel to the cavity bottom. The value of thermal fluence in a given irradiation plane is as uniform as 1-2%. The value of thermal fluence rate simply depends on the height from the cavity bottom. Values of thermal fluence rate in the range 700-1000cm(-2)s(-1) are available, depending on the irradiation plane chosen. The fraction of thermal neutrons is in the order of 90%, also depending on the irradiation plane. The angular distribution of thermal neutrons is roughly isotropic. Taking advantage of the HOTNES design, even large devices can be uniformly irradiated. This work presents HOTNES's design and describes the neutron field in the irradiation volume in terms of spatial, energy and direction distributions. Copyright © 2017 Elsevier Ltd. All rights reserved.

  12. Compound Refractive Lenses for Thermal Neutron Applications

    Energy Technology Data Exchange (ETDEWEB)

    Gary, Charles K.

    2013-11-12

    This project designed and built compound refractive lenses (CRLs) that are able to focus, collimate and image using thermal neutrons. Neutrons are difficult to manipulate compared to visible light or even x rays; however, CRLs can provide a powerful tool for focusing, collimating and imaging neutrons. Previous neutron CRLs were limited to long focal lengths, small fields of view and poor resolution due to the materials available and manufacturing techniques. By demonstrating a fabrication method that can produce accurate, small features, we have already dramatically improved the focal length of thermal neutron CRLs, and the manufacture of Fresnel lens CRLs that greatly increases the collection area, and thus efficiency, of neutron CRLs. Unlike a single lens, a compound lens is a row of N lenslets that combine to produce an N-fold increase in the refraction of neutrons. While CRLs can be made from a variety of materials, we have chosen to mold Teflon lenses. Teflon has excellent neutron refraction, yet can be molded into nearly arbitrary shapes. We designed, fabricated and tested Teflon CRLs for neutrons. We demonstrated imaging at wavelengths as short as 1.26 ? with large fields of view and achieved resolution finer than 250 μm which is better than has been previously shown. We have also determined designs for Fresnel CRLs that will greatly improve performance.

  13. Flat Panel Imaging of Thermal Neutrons

    Energy Technology Data Exchange (ETDEWEB)

    Gibbs, K.

    1999-09-14

    An initial investigation for the use of an amorphous silicon flat panel as an imaging detector for thermal neutrons is described. A dpiX Model SS2200 imaging panel was used with a Li-6 enriched, LiF-ZnS(Ag) scintillator screen for a thermal neutron imaging investigation using the Breazeale Nuclear Reactor and the neutron radiography facility at Penn State University''s Radiation Science and Engineering Center. Good quality thermal neutron images were obtained at exposures in the range of 106 to 107n/cm2, values that compare favorably with those normally required for a medium-speed film result. Spatial resolution observed was in the order of 2 line pairs/mm, a value consistent with the resolution limitation of the imaging screen. The neutron images showed excellent quality, as determined with radiographs of the modified Type A gage test piece, often used to evaluate thermal neutron radioscopic images. Fourteen consecutive holes in the ''A'' gage test piece were observed, an excellent result as compared to typical neutron radioscopic systems.

  14. Spatially resolved remote measurement of temperature by neutron resonance absorption

    Energy Technology Data Exchange (ETDEWEB)

    Tremsin, A.S., E-mail: ast@ssl.berkeley.edu [Space Sciences Laboratory, University of California at Berkeley, 7 Gauss Way, Berkeley, CA 94720 (United States); Kockelmann, W.; Pooley, D.E. [STFC, Rutherford Appleton Laboratory, ISIS Facility, Didcot OX11 0QX (United Kingdom); Feller, W.B. [NOVA Scientific, Inc., 10 Picker Road, Sturbridge, MA 01566 (United States)

    2015-12-11

    Deep penetration of neutrons into most engineering materials enables non-destructive studies of their bulk properties. The existence of sharp resonances in neutron absorption spectra enables isotopically-resolved imaging of elements present in a sample, as demonstrated by previous studies. At the same time the Doppler broadening of resonance peaks provides a method of remote measurement of temperature distributions within the same sample. This technique can be implemented at a pulsed neutron source with a short initial pulse allowing for the measurement of the energy of each registered neutron by the time of flight technique. A neutron counting detector with relatively high timing and spatial resolution is used to demonstrate the possibility to obtain temperature distributions across a 100 µm Ta foil with ~millimeter spatial resolution. Moreover, a neutron transmission measurement over a wide energy range can provide spatially resolved sample information such as temperature, elemental composition and microstructure properties simultaneously.

  15. THERMAL NEUTRON INTENSITIES IN SOILS IRRADIATED BY FAST NEUTRONS FROM POINT SOURCES. (R825549C054)

    Science.gov (United States)

    Thermal-neutron fluences in soil are reported for selected fast-neutron sources, selected soil types, and selected irradiation geometries. Sources include 14 MeV neutrons from accelerators, neutrons from spontaneously fissioning 252Cf, and neutrons produced from alp...

  16. High precision thermal neutron detectors

    Energy Technology Data Exchange (ETDEWEB)

    Radeka, V.; Schaknowski, N.A.; Smith, G.C.; Yu, B. [Brookhaven National Laboratory, Upton, NY (United States)

    1994-12-31

    Two-dimensional position sensitive detectors are indispensable in neutron diffraction experiments for determination of molecular and crystal structures in biology, solid-state physics and polymer chemistry. Some performance characteristics of these detectors are elementary and obvious, such as the position resolution, number of resolution elements, neutron detection efficiency, counting rate and sensitivity to gamma-ray background. High performance detectors are distinguished by more subtle characteristics such as the stability of the response (efficiency) versus position, stability of the recorded neutron positions, dynamic range, blooming or halo effects. While relatively few of them are needed around the world, these high performance devices are sophisticated and fairly complex, their development requires very specialized efforts. In this context, we describe here a program of detector development, based on {sup 3}He filled proportional chambers, which has been underway for some years at the Brookhaven National Laboratory. Fundamental approaches and practical considerations are outlined that have resulted in a series of high performance detectors with the best known position resolution, position stability, uniformity of response and reliability over time, for devices of this type.

  17. Thermal annealing in neutron-irradiated tribromobenzenes

    DEFF Research Database (Denmark)

    Siekierska, K.E.; Halpern, A.; Maddock, A. G.

    1968-01-01

    The distribution of 82Br among various products in neutron-irradiated isomers of tribromobenzene has been investigated, and the effect of thermal annealing examined. Reversed-phase partition chromatography was employed for the determination of radioactive organic products, and atomic bromine...

  18. Instrumentation to handle thermal polarized neutron beams

    NARCIS (Netherlands)

    Kraan, W.H.

    2004-01-01

    In this thesis we investigate devices needed to handle the polarization of thermal neutron beams: Ï/2-flippers (to start/stop Larmor precession) and Ï-flippers (to reverse polarization/precession direction) and illustrate how these devices are used to investigate the properties of matter and of the

  19. The Absorption Refrigerator as a Thermal Transformer

    Science.gov (United States)

    Herrmann, F.

    2009-01-01

    The absorption refrigerator can be considered a thermal transformer, that is, a device that is analogous to the electric transformer. The analogy is based on the correspondence between the extensive quantities, entropy and electric charge and the intensive variables, temperature and electric potential. (Contains 1 footnote and 6 figures.)

  20. Storage phosphors for thermal neutron detection

    Energy Technology Data Exchange (ETDEWEB)

    Sidorenko, A.V. E-mail: asidore@iri.tudelft.nl; Bos, A.J.J.; Dorenbos, P.; Le Masson, N.J.M.; Rodnyi, P.A.; Eijk, C.W.E. van; Berezovskaya, I.V.; Dotsenko, V.P

    2002-06-21

    The commercial BaFBr:Eu{sup 2+}{center_dot}Gd{sub 2}O{sub 3} image plate (IP) is used nowadays for thermal neutron detection. However, it is rather sensitive to {gamma}-ray background, which can deteriorate the image quality. We focused our research on the development of new types of storage phosphors with the general formula M{sub 2}B{sub 5}O{sub 9}Br:Ce{sup 3+} (M=Sr, Ca). Neutron detection is based on the {sup 10}B(n,{alpha}) reaction. The advantages of this system are the low Z{sub eff}, and the 40 times higher energy deposition resulting from the neutron capture reaction in comparison with that in the commercial IP. Here we present storage and spectroscopic properties of a series of newly synthesized haloborates. Comparative measurements with commercial IPs were done under neutron and {beta} irradiation. A satisfying light output of optically stimulated luminescence was achieved upon neutron irradiation.

  1. Storage phosphors for thermal neutron detection

    CERN Document Server

    Sidorenko, A V; Dorenbos, P; Le Masson, N J M; Rodnyi, P A; Eijk, C W E; Berezovskaya, I V; Dotsenko, V P

    2002-01-01

    The commercial BaFBr:Eu sup 2 sup +centre dot Gd sub 2 O sub 3 image plate (IP) is used nowadays for thermal neutron detection. However, it is rather sensitive to gamma-ray background, which can deteriorate the image quality. We focused our research on the development of new types of storage phosphors with the general formula M sub 2 B sub 5 O sub 9 Br:Ce sup 3 sup + (M=Sr, Ca). Neutron detection is based on the sup 1 sup 0 B(n,alpha) reaction. The advantages of this system are the low Z sub e sub f sub f , and the 40 times higher energy deposition resulting from the neutron capture reaction in comparison with that in the commercial IP. Here we present storage and spectroscopic properties of a series of newly synthesized haloborates. Comparative measurements with commercial IPs were done under neutron and beta irradiation. A satisfying light output of optically stimulated luminescence was achieved upon neutron irradiation.

  2. Thermal neutron diffusion cooling in wet quartz

    Energy Technology Data Exchange (ETDEWEB)

    Drozdowicz, K. [Henryk Niewodniczanski Institute of Nuclear Physics, Polish Academy of Sciences, ul. Radzikowskiego 152, PL-31-342 Cracow (Poland)]. E-mail: krzysztof.drozdowicz@ifj.edu.pl; Krynicka, E. [Henryk Niewodniczanski Institute of Nuclear Physics, Polish Academy of Sciences, ul. Radzikowskiego 152, PL-31-342 Crakcw (Poland); Dabrowska, J. [Henryk Niewodniczanski Institute of Nuclear Physics, Polish Academy of Sciences, ul. Radzikowskiego 152, PL-31-342 Cracow (Poland)

    2007-07-15

    The thermal neutron diffusion parameters of a rock material depend on the rock matrix itself and on the water content. The effect has been studied in quartz by Monte Carlo (MC) simulations of the variable buckling experiment for nine series of samples. A hyperbolic dependence of the density-removed diffusion cooling coefficient on the water content shows a variability of this parameter by two orders of magnitude. The function obtained for wet quartz is compared with the analogous dependence for wet dolomite.

  3. The measurements of thermal neutron flux distribution in a paraffin ...

    Indian Academy of Sciences (India)

    The term `thermal flux' implies a Maxwellian distribution of velocity and energy corresponding to the most probable velocity of 2200 ms-1 at 293.4 K. In order to measure the thermal neutron flux density, the foil activation method was used. Thermal neutron flux determination in paraffin phantom by counting the emitted rays of ...

  4. Thermalization of monoenergetic neutrons in a concrete room

    Energy Technology Data Exchange (ETDEWEB)

    Vega C, H.R.; Manzanares A, E.; Hernandez D, V.M.; Mercado, G.A. [UAZ, A.P. 336, 98000 Zacatecas (Mexico); Iniguez, M.P.; Martin M, A. [Universidad de Valladolid, (Spain)

    2006-07-01

    The thermalization of neutrons from monoenergetic neutron sources in a concrete room has been studied. During calibration of neutron detectors it is mandatory to make corrections due to neutron scattering produced by the room walls, therefore this factor must be known in advance. The scattered neutrons are thermalized and produce a neutron field that is directly proportional to source strength and inversely proportional to room total wall-surfaces, the proportional coefficient has been calculated for neutrons whose energy goes from 1 eV to 20 MeV. This coefficient was calculated using Monte Carlo methods for 150, 200 and 300 cm-radius spherical cavity, where monoenergetic neutrons were located at the center, along the spherical cavity radius neutron spectra were calculated at several source-to-detector distances inside the cavity. The obtained coefficient is almost three times larger than the factor normally utilized. (Author)

  5. Geant4 Analysis of a Thermal Neutron Real-Time Imaging System

    Science.gov (United States)

    Datta, Arka; Hawari, Ayman I.

    2017-07-01

    Thermal neutron imaging is a technique for nondestructive testing providing complementary information to X-ray imaging for a wide range of applications in science and engineering. Advancement of electronic imaging systems makes it possible to obtain neutron radiographs in real time. This method requires a scintillator to convert neutrons to optical photons and a charge-coupled device (CCD) camera to detect those photons. Alongside, a well collimated beam which reduces geometrical blurriness, the use of a thin scintillator can improve the spatial resolution significantly. A representative scintillator that has been applied widely for thermal neutron imaging is 6LiF:ZnS (Ag). In this paper, a multiphysics simulation approach for designing thermal neutron imaging system is investigated. The Geant4 code is used to investigate the performance of a thermal neutron imaging system starting with a neutron source and including the production of charged particles and optical photons in the scintillator and their transport for image formation in the detector. The simulation geometry includes the neutron beam collimator and sapphire filter. The 6LiF:ZnS (Ag) scintillator is modeled along with a pixelated detector for image recording. The spatial resolution of the system was obtained as the thickness of the scintillator screen was varied between 50 and 400 μm. The results of the simulation were compared to experimental results, including measurements performed using the PULSTAR nuclear reactor imaging beam, showing good agreement. Using the established model, further examination showed that the resolution contribution of the scintillator screen is correlated with its thickness and the range of the neutron absorption reaction products (i.e., the alpha and triton particles). Consequently, thinner screens exhibit improved spatial resolution. However, this will compromise detection efficiency due to the reduced probability of neutron absorption.

  6. Thermal neutron capture gamma-rays

    Energy Technology Data Exchange (ETDEWEB)

    Tuli, J.K.

    1983-01-01

    The energy and intensity of gamma rays as seen in thermal neutron capture are presented. Only those (n,..cap alpha..), E = thermal, reactions for which the residual nucleus mass number is greater than or equal to 45 are included. These correspond to evaluations published in Nuclear Data Sheets. The publication source data are contained in the Evaluated Nuclear Structure Data File (ENSDF). The data presented here do not involve any additional evaluation. Appendix I lists all the residual nuclides for which the data are included here. Appendix II gives a cumulated index to A-chain evaluations including the year of publication. The capture gamma ray data are given in two tables - the Table 1 is the list of all gamma rays seen in (n,..gamma..) reaction given in the order of increasing energy; the Table II lists the gamma rays according to the nuclide.

  7. Alternative method for thermal neutron flux measurements based on common boric acid as converter and Lr-15 detectors

    Energy Technology Data Exchange (ETDEWEB)

    Palacios, D.; Greaves, E. D.; Sajo B, L.; Barros, H. [Universidad Simon Bolivar, Laboratorio de Fisica Nuclear, Apdo. Postal 89000, Caracas (Venezuela, Bolivarian Republic of); Ingles, R. [Universidad Nacional de San Antonio Abad del Cusco, Av. de la Cultura No. 733, Cusco (Peru)

    2010-02-15

    A method to determine the flux and angular distribution of thermal neutrons with the use of Lr-115 detectors was developed. The use of the Lr-115 detector involves the exposure of a pressed boric acid sample (tablet) as a target, in tight contact with the track detector, to a flux of thermalized neutrons. The self-absorption effects in thin films or foil type thermal neutron detectors can be neglected by using the Lr-115 detector and boric acid tablet setup to operate via backside irradiation. The energy window and the critical angle-residual energy curve were determined by comparisons between the experimental and simulated track parameters. A computer program was developed to calculate the detector registration efficiency, so that the thermal neutron flux can be calculated from the track densities induced in the Lr-115 detector using the derived empirical formula. The proposed setup can serves as directional detector of thermal neutrons. (Author)

  8. Magneto–Thermal Evolution of Neutron Stars with Emphasis to ...

    Indian Academy of Sciences (India)

    The magnetic and thermal evolution of neutron stars is a very complex process with many non-linear interactions. For a decent understanding of neutron star physics, these evolutions cannot be considered isolated. A brief overview is presented, which describes the main magneto–thermal interactions that determine the fate ...

  9. Thermal Evaluation of Storage Rack with an Advanced Neutron Absorber during Normal Operation

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Hee-Jae; Kim, Mi-Jin; Sohn, Dong-Seong [UNIST, Ulsan (Korea, Republic of)

    2016-10-15

    The storage capacity of the domestic wet storage site is expected to reach saturation from Hanbit in 2024 to Sin-wolseong in 2038 and accordingly management alternatives are urgently taken. Since installation of the dense rack is considered in the short term, it is necessary to urgently develop an advanced neutron absorber which can be applied to a spent nuclear fuel storage facility. Neutron absorber is the material for controlling the reactivity. A material which has excellent thermal neutron absorption ability, high strength and corrosion resistance must be selected as the neutron absorber. Existing neutron absorbers are made of boron which has a good thermal absorption ability such as BORAL and METAMIC. However, possible problems have been reported in using the boron-based neutron absorber for wet storage facility. Gadolinium is known to have higher neutron absorption cross-section than that of boron. And the strength of duplex stainless steel is about 1.5 times higher than stainless steel 304 which has been frequently used as a structural material. Therefore, duplex stainless steel which contains gadolinium is in consideration as an advanced neutron absorber. Temperature distribution is shown in figure 4. In pool bottom region near the inlet shows a relatively low tendency and heat generated from the fuel assemblies is transmitted to the pool upper region by the vertical flow. Also, temperature gradient appear in rack structures for the axial direction and temperature is uniformly distributed in the pool upper region. Table 1 presents the calculated results. The maximum temperature is 306.63K and does not exceed the 333.15K (60℃). The maximum temperature of the neutron absorber is 306.48K.

  10. On sound absorption and thermal properties of non-wovens

    OpenAIRE

    Chen Jin-Jing; Yu Hong-Qin; Guo Zheng; You Jin-Zhang; Song Wen-Fang

    2015-01-01

    Non-woven is widely used as auxiliary materials of automobile industry due to its excellent sound absorption capability and good thermal property. The paper concludes that its density greatly affects sound absorption and thermal resistance, and an aluminum evaporated film can enhance the thermal resistance.

  11. On sound absorption and thermal properties of non-wovens

    Directory of Open Access Journals (Sweden)

    Chen Jin-Jing

    2015-01-01

    Full Text Available Non-woven is widely used as auxiliary materials of automobile industry due to its excellent sound absorption capability and good thermal property. The paper concludes that its density greatly affects sound absorption and thermal resistance, and an aluminum evaporated film can enhance the thermal resistance.

  12. UCN Source at an External Beam of Thermal Neutrons

    Directory of Open Access Journals (Sweden)

    E. V. Lychagin

    2015-01-01

    Full Text Available We propose a new method for production of ultracold neutrons (UCNs in superfluid helium. The principal idea consists in installing a helium UCN source into an external beam of thermal or cold neutrons and in surrounding this source with a solid methane moderator/reflector cooled down to ~4 K. The moderator plays the role of an external source of cold neutrons needed to produce UCNs. The flux of accumulated neutrons could exceed the flux of incident neutrons due to their numerous reflections from methane; also the source size could be significantly larger than the incident beam diameter. We provide preliminary calculations of cooling of neutrons. These calculations show that such a source being installed at an intense source of thermal or cold neutrons like the ILL or PIK reactor or the ESS spallation source could provide the UCN density 105 cm−3, the production rate 107 UCN/s−1. Main advantages of such an UCN source include its low radiative and thermal load, relatively low cost, and convenient accessibility for any maintenance. We have carried out an experiment on cooling of thermal neutrons in a methane cavity. The data confirm the results of our calculations of the spectrum and flux of neutrons in the methane cavity.

  13. Stereoscopic radiographic images with thermal neutrons

    Science.gov (United States)

    Silvani, M. I.; Almeida, G. L.; Rogers, J. D.; Lopes, R. T.

    2011-10-01

    Spatial structure of an object can be perceived by the stereoscopic vision provided by eyes or by the parallax produced by movement of the object with regard to the observer. For an opaque object, a technique to render it transparent should be used, in order to make visible the spatial distribution of its inner structure, for any of the two approaches used. In this work, a beam of thermal neutrons at the main port of the Argonauta research reactor of the Instituto de Engenharia Nuclear in Rio de Janeiro/Brazil has been used as radiation to render the inspected objects partially transparent. A neutron sensitive Imaging Plate has been employed as a detector and after exposure it has been developed by a reader using a 0.5 μm laser beam, which defines the finest achievable spatial resolution of the acquired digital image. This image, a radiographic attenuation map of the object, does not represent any specific cross-section but a convoluted projection for each specific attitude of the object with regard to the detector. After taking two of these projections at different object attitudes, they are properly processed and the final image is viewed by a red and green eyeglass. For monochromatic images this processing involves transformation of black and white radiographies into red and white and green and white ones, which are afterwards merged to yield a single image. All the processes are carried out with the software ImageJ. Divergence of the neutron beam unfortunately spoils both spatial and contrast resolutions, which become poorer as object-detector distance increases. Therefore, in order to evaluate the range of spatial resolution corresponding to the 3D image being observed, a curve expressing spatial resolution against object-detector gap has been deduced from the Modulation Transfer Functions experimentally. Typical exposure times, under a reactor power of 170 W, were 6 min for both quantitative and qualitative measurements. In spite of its intrinsic constraints

  14. NEUTRON RADIOGRAPHY MEASUREMENT OF SALT SOLUTION ABSORPTION IN MORTAR.

    Science.gov (United States)

    Lucero, Catherine L; Spragg, Robert P; Bentz, Dale P; Hussey, Daniel S; Jacobson, David L; Weiss, W Jason

    2017-01-01

    Some concrete pavements in the US have recently exhibited premature joint deterioration. It is hypothesized that one component of this damage can be attributed to a reaction that occurs when salt-laden water is absorbed in the concrete and reacts with the matrix. This study examines the absorption of CaCl2 solution in mortar via neutron imaging. Mortar specimens were prepared with water to cement ratios, (w/c), of 0.36, 0.42 and 0.50 by mass and exposed to chloride solutions with concentrations ranging from 0 % to 29.8 % by mass. Depth of fluid penetration and moisture content along the specimen length were determined for 96 h after exposure. At high salt concentration (29.8 %), the sorption rate decreased by over 80 % in all samples. Along with changes in surface tension and viscosity, CaCl2 reacts with the cement paste to produce products (Friedel's salt, Kuzel's salt, or calcium oxychloride) that block pores and reduce absorption.

  15. Thermal neutron counts and derivated charts | Odusote | Journal of ...

    African Journals Online (AJOL)

    thermal neutrons)” approximation. The resulting equation was applied with a mixing index, , for various formation matrices and porosities. The ratio of counts from two different detectors was plotted as a function of porosity for these formations.

  16. Thermal-neutron capture for A=36-44

    CERN Document Server

    Chunmei, Z

    2003-01-01

    A new evaluation has been undertaken of the level properties, prompt gamma rays and decay scheme properties of thermal neutron capture for nuclides with mass number A=36-44. The cutoff date is March 2002. This evaluation is effectively an update of the data table of the Prompt Gamma Rays from Thermal Neutron Capture as published in Atomic Data and Nuclear Data Tables 26, 511, (1981).

  17. Lithium-containing scintillators for thermal neutron, fast neutron, and gamma detection

    Energy Technology Data Exchange (ETDEWEB)

    Zaitseva, Natalia P.; Carman, M. Leslie; Faust, Michelle A.

    2016-03-01

    In one embodiment, a scintillator includes a scintillator material; a primary fluor, and a Li-containing compound, where the Li-containing compound is soluble in the primary fluor, and where the scintillator exhibits an optical response signature for thermal neutrons that is different than an optical response signature for fast neutrons and gamma rays.

  18. Response of six neutron survey meters in mixed fields of fast and thermal neutrons.

    Science.gov (United States)

    Kim, S I; Kim, B H; Chang, I; Lee, J I; Kim, J L; Pradhan, A S

    2013-10-01

    Calibration neutron fields have been developed at KAERI (Korea Atomic Energy Research Institute) to study the responses of commonly used neutron survey meters in the presence of fast neutrons of energy around 10 MeV. The neutron fields were produced by using neutrons from the (241)Am-Be sources held in a graphite pile and a DT neutron generator. The spectral details and the ambient dose equivalent rates of the calibration fields were established, and the responses of six neutron survey meters were evaluated. Four single-moderator-based survey meters exhibited an under-responses ranging from ∼9 to 55 %. DINEUTRUN, commonly used in fields around nuclear reactors, exhibited an over-response by a factor of three in the thermal neutron field and an under-response of ∼85 % in the mixed fields. REM-500 (tissue-equivalent proportional counter) exhibited a response close to 1.0 in the fast neutron fields and an under-response of ∼50 % in the thermal neutron field.

  19. Characterization of thermal neutron beam monitors

    Directory of Open Access Journals (Sweden)

    F. Issa

    2017-09-01

    Full Text Available Neutron beam monitors with a wide range of efficiencies, low γ sensitivity, and high time and space resolution are required in neutron beam experiments to continuously diagnose the delivered beam. In this work, commercially available neutron beam monitors have been characterized using the R2D2 beamline at IFE (Norway and using a Be-based neutron source. For the γ sensitivity measurements different γ sources have been used. The evaluation of the monitors includes, the study of their efficiency, attenuation, scattering, and sensitivity to γ. In this work we report the results of this characterization.

  20. Neutron moderation theory with thermal motion of the moderator nuclei

    Science.gov (United States)

    Rusov, V. D.; Tarasov, V. A.; Chernezhenko, S. A.; Kakaev, A. A.; Smolyar, V. P.

    2017-09-01

    In this paper we present the analytical expression for the neutron scattering law for an isotropic source of neutrons, obtained within the framework of the gas model with the temperature of the moderating medium as a parameter. The obtained scattering law is based on the solution of the general kinematic problem of elastic scattering of neutrons on nuclei in the L-system. Both the neutron and the nucleus possess arbitrary velocities in the L-system. For the new scattering law we obtain the flux densities and neutron moderation spectra as functions of temperature for the reactor fissile medium. The expressions for the moderating neutrons spectra allow reinterpreting the physical nature of the underlying processes in the thermal region.

  1. Neutron moderation theory with thermal motion of the moderator nuclei

    Energy Technology Data Exchange (ETDEWEB)

    Rusov, V.D.; Tarasov, V.A.; Chernezhenko, S.A.; Kakaev, A.A.; Smolyar, V.P. [Odessa National Polytechnic University, Department of Theoretical and Experimental Nuclear Physics, Odessa (Ukraine)

    2017-09-15

    In this paper we present the analytical expression for the neutron scattering law for an isotropic source of neutrons, obtained within the framework of the gas model with the temperature of the moderating medium as a parameter. The obtained scattering law is based on the solution of the general kinematic problem of elastic scattering of neutrons on nuclei in the L-system. Both the neutron and the nucleus possess arbitrary velocities in the L-system. For the new scattering law we obtain the flux densities and neutron moderation spectra as functions of temperature for the reactor fissile medium. The expressions for the moderating neutrons spectra allow reinterpreting the physical nature of the underlying processes in the thermal region. (orig.)

  2. Experimental characterization of semiconductor-based thermal neutron detectors

    Energy Technology Data Exchange (ETDEWEB)

    Bedogni, R., E-mail: roberto.bedogni@lnf.infn.it [IFNF—LNF, via E. Fermi n. 40, 00044 Frascati, Roma (Italy); Bortot, D.; Pola, A.; Introini, M.V.; Lorenzoli, M. [Politecnico di Milano, Dipartimento di Energia, via La Masa 34, 20156 Milano (Italy); INFN—Milano, Via Celoria 16, 20133 Milano (Italy); Gómez-Ros, J.M. [IFNF—LNF, via E. Fermi n. 40, 00044 Frascati, Roma (Italy); CIEMAT, Av. Complutense 40, 28040 Madrid (Spain); Sacco, D. [IFNF—LNF, via E. Fermi n. 40, 00044 Frascati, Roma (Italy); INAIL—DIT, Via di Fontana Candida 1, 00040 Monteporzio Catone (Italy); Esposito, A.; Gentile, A.; Buonomo, B. [IFNF—LNF, via E. Fermi n. 40, 00044 Frascati, Roma (Italy); Palomba, M.; Grossi, A. [ENEA Triga RC-1C.R. Casaccia, via Anguillarese 301, 00060 S. Maria di Galeria, Roma (Italy)

    2015-04-21

    In the framework of NESCOFI@BTF and NEURAPID projects, active thermal neutron detectors were manufactured by depositing appropriate thickness of {sup 6}LiF on commercially available windowless p–i–n diodes. Detectors with different radiator thickness, ranging from 5 to 62 μm, were manufactured by evaporation-based deposition technique and exposed to known values of thermal neutron fluence in two thermal neutron facilities exhibiting different irradiation geometries. The following properties of the detector response were investigated and presented in this work: thickness dependence, impact of parasitic effects (photons and epithermal neutrons), linearity, isotropy, and radiation damage following exposure to large fluence (in the order of 10{sup 12} cm{sup −2})

  3. Two-dimensional thermometry by using neutron resonance absorption spectrometer DOG

    Energy Technology Data Exchange (ETDEWEB)

    Kamiyama, T.; Noda, H.; Kiyanagi, Y. [Department of Quantum Energy Engineering, Graduate School of Engineering, Hokkaido Univ., Sapporo (Japan); Ikeda, S. [Institute of Materials Structure Science, High Energy Accelerator Research Organization, Tsukuba, Ibaraki (Japan)

    2001-03-01

    We applied the neutron resonance absorption spectroscopy to thermometry of a bulk object. The measurement was done by using the neutron resonance absorption spectrometer, DOG, installed at KENS, High Energy Accelerator Research Organization Neutron Source, which enables us to investigate effective temperature of a particular element by analyzing line width of resonance absorption spectrum. The effective temperature becomes consistence with the sample temperature above room temperature. For the analysis we applied the computed tomography method to reconstruct the temperature distribution on the object cross section. The results and the calculated distribution by the heat conducting equation are well agreed on the temperature difference inside the object. (author)

  4. Boron neutron capture therapy (BNCT). Recent aspect, a change from thermal neutron to epithermal neutron beam and a new protocol

    Energy Technology Data Exchange (ETDEWEB)

    Nakagawa, Yoshinobu [Dept. of Neurosurgery National Kagawa Children' s Hospital, Zentsuji, Kagawa (Japan)

    1999-08-01

    Since 1968, One-hundred seventy three patients with glioblastoma (n=81), anaplastic astrocytoma (n=44), low grade astrocytoma (n=16) or other types of tumor (n=32) were treated by boron-neutron capture therapy (BNCT) using a combination of thermal neutron and BSH in 5 reactors (HTR n=13, JRR-3 n=1, MuITR n=98, KUR n=28, JRR-2 n=33). Out of 101 patients with glioma treated by BNCT under the recent protocol, 33 (10 glioblastoma, 14 anaplastic astrocytoma, 9 low grade astrocytoma) patients lived or have lived longer than 3 years. Nine of these 33 lived or have lived longer than 10 years. According to the retrospective analysis, the important factors related to the clinical results were tumor dose radiation dose and maximum radiation dose in thermal brain cortex. The result was not satisfied as it was expected. Then, we decided to introduce mixed beams which contain thermal neutron and epithermal neutron beams. KUR was reconstructed in 1996 and developed to be available to use mixed beams. Following the shutdown of the JRR-2, JRR-4 was renewed for medical use in 1998. Both reactors have capacity to yield thermal neutron beam, epithermal neutron beam and mixed beams. The development of the neutron source lead us to make a new protocol. (author)

  5. Optimization of thermal neutron shield concrete mixture using artificial neural network

    Energy Technology Data Exchange (ETDEWEB)

    Yadollahi, A. [Engineering Department, Shahid Beheshti University, G.C., P.O. Box: 1983963113, Tehran (Iran, Islamic Republic of); Nazemi, E., E-mail: nazemi.ehsan@yahoo.com [Young Researchers and Elite Club, Kermanshah Branch, Islamic Azad University, Kermanshah (Iran, Islamic Republic of); Zolfaghari, A. [Engineering Department, Shahid Beheshti University, G.C., P.O. Box: 1983963113, Tehran (Iran, Islamic Republic of); Ajorloo, A.M. [Water and Environmental Engineering Department, Shahid Beheshti University, P.O. Box: 167651719, Tehran (Iran, Islamic Republic of)

    2016-08-15

    Highlights: • Colemanite was used in fabricating of thermal neutron shield concrete. • The Taguchi method was implemented to obtain the data set required for training the ANN. • Trained ANN predicted quality characteristics of thermal neutron shield. - Abstract: Colemanite is the most convenient boron mineral which has been widely used in construction of radiation shielding concrete in order to improve the capture of thermal neutrons. But utilization of Colemanite in radiation shielding concrete has a deleterious effect on both physical and mechanical properties. In the present work, Taguchi method and artificial neural network (ANN) were employed to find an optimal mixture of Colemanite based concrete in order to improve the boron content of concrete and increase thermal neutron absorption without violating the standards for physical and mechanical properties. Using Taguchi method for experimental design, 27 concrete samples with different mixtures were fabricated and tested. Water/cement ratio, cement quantity, volume fraction of Colemanite aggregate and silica fume quantity were selected as control factors, and compressive strength, ultrasonic pulse velocity and thermal neutron transmission ratio were considered as the quality responses. Obtained data from 27 experiments were used to train 3 ANNs. Four control factors were utilized as the inputs of 3 ANNs and 3 quality responses were used as the outputs, separately (each ANN for one quality response). After training the ANNs, 1024 different mixtures with different quality responses were predicted. At the final, optimum mixture was obtained among the predicted different mixtures. Results demonstrated that the optimal mixture of thermal neutron shielding concrete has a water–cement ratio of 0.38, cement content of 400 kg/m{sup 3}, a volume fraction Colemanite aggregate of 50% and silica fume–cement ratio of 0.15.

  6. Biomembranes research using thermal and cold neutrons.

    Science.gov (United States)

    Heberle, F A; Myles, D A A; Katsaras, J

    2015-11-01

    In 1932 James Chadwick discovered the neutron using a polonium source and a beryllium target (Chadwick, 1932). In a letter to Niels Bohr dated February 24, 1932, Chadwick wrote: "whatever the radiation from Be may be, it has most remarkable properties." Where it concerns hydrogen-rich biological materials, the "most remarkable" property is the neutron's differential sensitivity for hydrogen and its isotope deuterium. Such differential sensitivity is unique to neutron scattering, which unlike X-ray scattering, arises from nuclear forces. Consequently, the coherent neutron scattering length can experience a dramatic change in magnitude and phase as a result of resonance scattering, imparting sensitivity to both light and heavy atoms, and in favorable cases to their isotopic variants. This article describes recent biomembranes research using a variety of neutron scattering techniques. Published by Elsevier Ireland Ltd.

  7. Enhanced plastic neutron shielding for thermal and epithermal neutrons

    Energy Technology Data Exchange (ETDEWEB)

    Palomino, L A RodrIguez; Blostein, J J; Dawidowski, J [Consejo Nacional de Investigaciones CientIficas y Tecnicas, Centro Atomico Bariloche and Instituto Balseiro, Comision Nacional de EnergIa Atomica, Universidad Nacional de Cuyo, (8400) Bariloche, Av. Bustillo 9500, S. C. de Bariloche, RIo Negro (Argentina); Cuello, G J [Institut Laue Langevin, 6, rue Jules Horowitz, F-38042 Grenoble Cedex 9 (France)], E-mail: javier@cab.cnea.gov.ar

    2008-06-15

    We describe a compound made of paraffin and boron carbide (boraffin) deviced to enhance epithermal neutron shielding. The compound is easily prepared and is specially suited to be adapted to particular surfaces. Transmission experiments show a favourable comparison with a commercial rubber-boron carbide compound in the epithermal range. A detector shielding built with this material is described and the achieved background reduction experimentally determined is shown.

  8. A method for measuring macroscopic cross-sections for thermal neutrons.

    Science.gov (United States)

    El Abd, A; Taha, G; Ellithi, A Y

    2017-10-01

    A method was proposed for measuring macroscopic absorption and scattering cross-sections for thermal neutrons. It is based on a Pu-Be neutron source and He-3 neutron detectors assembly. A beam of neutrons was obtained from the source imbedded in a water tank. The He-3 detectors oriented inside the sample and at 180° and 0° with respect to the incident neutron beam were used to register neutrons after interaction with the samples. Neutron count rates (detectors responses) were obtained for large (5.5l) as well as small (1.3l) volumes of standard samples. Sensitivities of the results obtained for the large and small samples were compared. A semi-empirical model was proposed to fit the results. It describes the relative detector responses in terms of a dimensionless variable which depends on the geometrical parameters and cross section of the standard samples used. The model successfully fits the results obtained. Advantages and limitations of the method were discussed. Copyright © 2017 Elsevier Ltd. All rights reserved.

  9. Study of a neutron irradiated reactor pressure vessel steel by X-ray absorption spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Cammelli, S. [LWV, NES, Paul Scherrer Institute, 5232 Villigen PSI (Switzerland)], E-mail: sebastiano.cammelli@psi.ch; Degueldre, C.; Kuri, G.; Bertsch, J. [LWV, NES, Paul Scherrer Institute, 5232 Villigen PSI (Switzerland)

    2008-11-15

    Reactor pressure vessel (RPV) reference steel samples submitted to neutron irradiations followed by thermal annealing were investigated by X-ray absorption fine structure (XAFS) spectroscopy. Several studies revealed that Cu and Ni impurities can form nanoclusters. In the unirradiated sample and in the only-irradiated sample no significant clustering is detected. In all irradiated and subsequently annealed samples increases of Cu and Ni atom densities are recorded around the absorber. Furthermore, the density of Cu and Ni atoms determined in the first and second shells around the absorber is found to be affected by the irradiation and annealing treatment. The comparison of the XAFS data at Cu and Ni K-edges shows that these elements reside in arrangements similar to bcc Fe. However, the local irradiation damage yields vacancy fractions which were determined from the analysis of XAFS data with a precision of {approx}5%.

  10. Thermal neutron equivalent doses assessment around KFUPM neutron source storage area using NTDs

    Energy Technology Data Exchange (ETDEWEB)

    Abu-Jarad, F.; Fazal-ur-Rehman; Al-Haddad, M.N.; Al-Jarrallah, M.I.; Nassar, R

    2002-07-01

    Area passive neutron dosemeters based on nuclear track detectors (NTDs) have been used for 13 days to assess accumulated low doses of thermal neutrons around neutron source storage area of the King Fahd University of Petroleum and Minerals (KFUPM). Moreover, the aim of this study is to check the effectiveness of shielding of the storage area. NTDs were mounted with the boron converter on their surface as one compressed unit. The converter is a lithium tetraborate (Li{sub 2}B{sub 4}O{sub 7}) layer for thermal neutron detection via {sup 10}B(N,{alpha}){sup 7}Li and {sup 6}Li(n,{alpha}){sup 3}H nuclear reactions. The area passive dosemeters were installed on 26 different locations around the source storage area and adjacent rooms. The calibration factor for NTD-based area passive neutron dosemeters was found to be 8.3 alpha tracks.cm{sup -2}.{mu}Sv{sup -1} using active snoopy neutron dosemeters in the KFUPM neutron irradiation facility. The results show the variation of accumulated dose with locations around the storage area. The range of dose rates varied from as low as 40 nSv.h{sup -1} up to 11 {mu}Sv.h{sup -1}. The study indicates that the area passive neutron dosemeter was able to detect accumulated doses as low as 40 nSv.h{sup -1}, which could not be detected with the available active neutron dosemeters. The results of the study also indicate that an additional shielding is required to bring the dose rates down to background level. The present investigation suggests extending this study to find the contribution of doses from fast neutrons around the neutron source storage area using NTDs through proton recoil. The significance of this passive technique is that it is highly sensitive and does not require any electronics or power supplies, as is the case in active systems. (author)

  11. The measurements of thermal neutron flux distribution in a paraffin ...

    Indian Academy of Sciences (India)

    perturbation causes flux depression in its interior [2]. Four indium foils were placed in ... times of its half life, with 0.4% error, the activity will be equal to saturation activity. Before counting and with respect to the ... cadmium thickness will cause a decrease in epithermal neutron absorption [16]. Pramana – J. Phys., Vol. 80, No.

  12. Thermal neutron scintillators using unenriched boron nitride and zinc sulfide

    Science.gov (United States)

    McMillan, J. E.; Cole, A. J.; Kirby, A.; Marsden, E.

    2015-06-01

    Thermal neutron detectors based on powdered zinc sulfide intimately mixed with a neutron capture compound have a history as long as scintillation technique itself. We show that using unenriched boron nitride powder, rather than the more commonly used enriched lithium fluoride, results in detection screens which produce less light but which are very considerably cheaper. Methods of fabricating large areas of this material are presented. The screens are intended for the production of large area low cost neutron detectors as a replacement for helium-3 proportional tubes.

  13. Dosimetry in Thermal Neutron Irradiation Facility at BMRR

    Science.gov (United States)

    Hu, J.-P.; Holden, N. E.; Reciniello, R. N.

    2016-02-01

    Radiation dosimetry for Neutron Capture Therapy (NCT) has been performed since 1959 at Thermal Neutron Irradiation Facility (TNIF) of the three-megawatt light-water cooled Brookhaven Medical Research Reactor (BMRR). In the early 1990s when more effective drug carriers were developed for NCT, in which the eye melanoma and brain tumors in rats were irradiated in situ, extensive clinical trials of small animals began using a focused thermal neutron beam. To improve the dosimetry at irradiation facility, a series of innovative designs and major modifications made to enhance the beam intensity and to ease the experimental sampling at BMRR were performed; including (1) in-core fuel addition to increase source strength and balance flux of neutrons towards two ports, (2) out of core moderator remodeling, done by replacing thicker D2O tanks at graphite-shutter interfacial areas, to expedite neutron thermalization, (3) beam shutter upgrade to reduce strayed neutrons and gamma dose, (4) beam collimator redesign to optimize the beam flux versus dose for animal treatment, (5) beam port shielding installation around the shutter opening area (lithium-6 enriched polyester-resin in boxes, attached with polyethylene plates) to reduce prompt gamma and fast neutron doses, (6) sample holder repositioning to optimize angle versus distance for a single organ or whole body irradiation, and (7) holder wall buildup with neutron reflector materials to increase dose and dose rate from scattered thermal neutrons. During the facility upgrade, reactor dosimetry was conducted using thermoluminescent dosimeters TLD for gamma dose estimate, using ion chambers to confirm fast neutron and gamma dose rate, and by the activation of gold-foils with and without cadmium-covers, for fast and thermal neutron flux determination. Based on the combined effect from the size and depth of tumor cells and the location and geometry of dosimeters, the measured flux from cadmium-difference method was 4-7% lower than

  14. Dosimetry in Thermal Neutron Irradiation Facility at BMRR

    Energy Technology Data Exchange (ETDEWEB)

    Hu, J. P. [Brookhaven National Lab. (BNL), Upton, NY (United States); Holden, N. E. [Brookhaven National Lab. (BNL), Upton, NY (United States); Reciniello, R. N.

    2014-05-23

    Radiation dosimetry for Neutron Capture Therapy (NCT) has been performed since 1959 at Thermal Neutron Irradiation Facility (TNIF) of the three-megawatt light-water cooled Brookhaven Medical Research Reactor (BMRR). In the early 1990s when more effective drug carriers were developed for NCT, in which the eye melanoma and brain tumors in rats were irradiated in situ, extensive clinical trials of small animals began using a focused thermal neutron beam. To improve the dosimetry at irradiation facility, a series of innovative designs and major modifications made to enhance the beam intensity and to ease the experimental sampling at BMRR were performed; including (1) in-core fuel addition to increase source strength and balance flux of neutrons towards two ports, (2) out of core moderator remodeling, done by replacing thicker D2O tanks at graphite-shutter interfacial areas, to expedite neutron thermalization, (3) beam shutter upgrade to reduce strayed neutrons and gamma dose, (4) beam collimator redesign to optimize the beam flux versus dose for animal treatment, (5) beam port shielding installation around the shutter opening area (lithium-6 enriched polyester-resin in boxes, attached with polyethylene plates) to reduce prompt gamma and fast neutron doses, (6) sample holder repositioning to optimize angle versus distance for a single organ or whole body irradiation, and (7) holder wall buildup with neutron reflector materials to increase dose and dose rate from scattered thermal neutrons. During the facility upgrade, reactor dosimetry was conducted using thermoluminescent dosimeters TLD for gamma dose estimate, using ion chambers to confirm fast neutron and gamma dose rate, and by the activation of gold-foils with and without cadmium-covers, for fast and thermal neutron flux determination. Based on the combined effect from the size and depth of tumor cells and the location and geometry of dosimeters, the measured flux from cadmium-difference method was 4 - 7

  15. Introduction to the theory of thermal neutron scattering

    CERN Document Server

    Squires, G L

    2012-01-01

    Since the advent of the nuclear reactor, thermal neutron scattering has proved a valuable tool for studying many properties of solids and liquids, and research workers are active in the field at reactor centres and universities throughout the world. This classic text provides the basic quantum theory of thermal neutron scattering and applies the concepts to scattering by crystals, liquids and magnetic systems. Other topics discussed are the relation of the scattering to correlation functions in the scattering system, the dynamical theory of scattering and polarisation analysis. No previous knowledge of the theory of thermal neutron scattering is assumed, but basic knowledge of quantum mechanics and solid state physics is required. The book is intended for experimenters rather than theoreticians, and the discussion is kept as informal as possible. A number of examples, with worked solutions, are included as an aid to the understanding of the text.

  16. Targets for bulk hydrogen analysis using thermal neutrons

    CERN Document Server

    Csikai, J; Buczko, C M

    2002-01-01

    The reflection property of substances can be characterized by the reflection cross-section of thermal neutrons, sigma subbeta. A combination of the targets with thin polyethylene foils allowed an estimation of the flux depression of thermal neutrons caused by a bulk sample containing highly absorbing elements or compounds. Some new and more accurate sigma subbeta values were determined by using the combined target arrangement. For the ratio, R of the reflection and the elastic scattering cross-sections of thermal neutrons, R=sigma subbeta/sigma sub E sub L a value of 0.60+-0.02 was found on the basis of the data obtained for a number of elements from H to Pb. Using this correlation factor, and the sigma sub E sub L values, the unknown sigma subbeta data can be deduced. The equivalent thicknesses, to polyethylene or hydrogen, of the different target materials were determined from the sigma subbeta values.

  17. Fabrication of Pillar-Structured Thermal Neutron Detectors

    Energy Technology Data Exchange (ETDEWEB)

    Nikolic, R J; Conway, A M; Reinhardt, C E; Graff, R T; Wang, T F; Deo, N; Cheung, C L

    2007-11-19

    Pillar detector is an innovative solid state device structure that leverages advanced semiconductor fabrication technology to produce a device for thermal neutron detection. State-of-the-art thermal neutron detectors have shortcomings in achieving simultaneously high efficiency, low operating voltage while maintaining adequate fieldability performance. By using a 3-dimensional silicon PIN diode pillar array filled with isotopic boron 10, ({sup 10}B) a high efficiency device is theoretically possible. The fabricated pillar structures reported in this work are composed of 2 {micro}m diameter silicon pillars with a 4 {micro}m pitch and pillar heights of 6 and 12 {micro}m. The pillar detector with a 12 {micro}m height achieved a thermal neutron detection efficiency of 7.3% at 2V.

  18. System and plastic scintillator for discrimination of thermal neutron, fast neutron, and gamma radiation

    Science.gov (United States)

    Zaitseva, Natalia P.; Carman, M. Leslie; Faust, Michelle A.; Glenn, Andrew M.; Martinez, H. Paul; Pawelczak, Iwona A.; Payne, Stephen A.

    2017-05-16

    A scintillator material according to one embodiment includes a polymer matrix; a primary dye in the polymer matrix, the primary dye being a fluorescent dye, the primary dye being present in an amount of 3 wt % or more; and at least one component in the polymer matrix, the component being selected from a group consisting of B, Li, Gd, a B-containing compound, a Li-containing compound and a Gd-containing compound, wherein the scintillator material exhibits an optical response signature for thermal neutrons that is different than an optical response signature for fast neutrons and gamma rays. A system according to one embodiment includes a scintillator material as disclosed herein and a photodetector for detecting the response of the material to fast neutron, thermal neutron and gamma ray irradiation.

  19. Thermal-neutron capture for A=36-44

    OpenAIRE

    Chunmei, Z.; Firestone, R. B.

    2003-01-01

    The prompt gamma-ray data of thermal- neutron captures for nuclear mass number A=26-35 had been evaluated and published in "ATOMIC DATA AND NUCLEAR DATA TABLES, 26, 511 (1981)". Since that time the many experimental data of the thermal-neutron captures have been measured and published. The update of the evaluated prompt gamma-ray data is very necessary for use in PGAA of high-resolution analytical prompt gamma-ray spectroscopy. Besides, the evaluation is also very needed in the Evaluated...

  20. Evaluation of thermal neutron irradiation field using a cyclotron-based neutron source for alpha autoradiography.

    Science.gov (United States)

    Tanaka, H; Sakurai, Y; Suzuki, M; Masunaga, S; Mitsumoto, T; Kinashi, Y; Kondo, N; Narabayashi, M; Nakagawa, Y; Watanabe, T; Fujimoto, N; Maruhashi, A; Ono, K

    2014-06-01

    It is important to measure the microdistribution of (10)B in a cell to predict the cell-killing effect of new boron compounds in the field of boron neutron capture therapy. Alpha autoradiography has generally been used to detect the microdistribution of (10)B in a cell. Although it has been performed using a reactor-based neutron source, the realization of an accelerator-based thermal neutron irradiation field is anticipated because of its easy installation at any location and stable operation. Therefore, we propose a method using a cyclotron-based epithermal neutron source in combination with a water phantom to produce a thermal neutron irradiation field for alpha autoradiography. This system can supply a uniform thermal neutron field with an intensity of 1.7×10(9) (cm(-2)s(-1)) and an area of 40mm in diameter. In this paper, we give an overview of our proposed system and describe a demonstration test using a mouse liver sample injected with 500mg/kg of boronophenyl-alanine. Copyright © 2014. Published by Elsevier Ltd.

  1. Neutronics Study on LEU Nuclear Thermal Rocket Fuel Options

    Energy Technology Data Exchange (ETDEWEB)

    Venneri, Paolo; Kim, Yong Hee [KAIST, Daejeon (Korea, Republic of); Howe, Steven [CSNR, Idaho (United States)

    2014-10-15

    This has resulted in a non-trivial simplification of the tasks needed to develop such an engine and the quick initial development of the concept. There are, however, a series of key core-design choices that are currently under scrutiny in the field that have to be resolved in order for the LEU-NTR to be fully developed. The most important of these is the choice of fuel: carbide composite or tungsten cermet. This study presents a first comparison of the two fuel types specifically in the neutronic application to the LEU-NTR, keeping in mind the unique neutronic environment and the system requirements of the system. The scope of the study itself is limited to a neutronics study of the two fuels and only a cursory overview of the material properties of the fuels themselves... The results of this study have led to two major conclusions. First of all is that the carbide composite fuel is, from a neutronics standpoint, a much better fuel. It has a low absorption cross-section, is inherently a strong moderator, is able to achieve a higher reactivity using smaller amounts of fissile material, and can potentially enable a smaller reactor. Second is that despite its neutronic difficulties (high absorption, inferior moderating abilities, and lower k-infinity values) the tungsten cermet fuel is still able to perform satisfactorily in an LEU-NTR, largely due to its ability to have an extremely high fuel loading.

  2. Development of An Epi-thermal Neutron Field for Fundamental Researches for BNCT with A DT Neutron Source

    Science.gov (United States)

    Osawa, Yuta; Imoto, Shoichi; Kusaka, Sachie; Sato, Fuminobu; Tanoshita, Masahiro; Murata, Isao

    2017-09-01

    Boron Neutron Capture Therapy (BNCT) is known to be a new promising cancer therapy suppressing influence against normal cells. In Japan, Accelerator Based Neutron Sources (ABNS) are being developed for BNCT. For the spread of ABNS based BNCT, we should characterize the neutron field beforehand. For this purpose, we have been developing a low-energy neutron spectrometer based on 3He position sensitive proportional counter. In this study, a new intense epi-thermal neutron field was developed with a DT neutron source for verification of validity of the spectrometer. After the development, the neutron field characteristics were experimentally evaluated by using activation foils. As a result, we confirmed that an epi-thermal neutron field was successfully developed suppressing fast neutrons substantially. Thereafter, the neutron spectrometer was verified experimentally. In the verification, although a measured detection depth distribution agreed well with the calculated distribution by MCNP, the unfolded spectrum was significantly different from the calculated neutron spectrum due to contribution of the side neutron incidence. Therefore, we designed a new neutron collimator consisting of a polyethylene pre-collimator and boron carbide neutron absorber and confirmed numerically that it could suppress the side incident neutrons and shape the neutron flux to be like a pencil beam.

  3. Development of An Epi-thermal Neutron Field for Fundamental Researches for BNCT with A DT Neutron Source

    Directory of Open Access Journals (Sweden)

    Osawa Yuta

    2017-01-01

    Full Text Available Boron Neutron Capture Therapy (BNCT is known to be a new promising cancer therapy suppressing influence against normal cells. In Japan, Accelerator Based Neutron Sources (ABNS are being developed for BNCT. For the spread of ABNS based BNCT, we should characterize the neutron field beforehand. For this purpose, we have been developing a low-energy neutron spectrometer based on 3He position sensitive proportional counter. In this study, a new intense epi-thermal neutron field was developed with a DT neutron source for verification of validity of the spectrometer. After the development, the neutron field characteristics were experimentally evaluated by using activation foils. As a result, we confirmed that an epi-thermal neutron field was successfully developed suppressing fast neutrons substantially. Thereafter, the neutron spectrometer was verified experimentally. In the verification, although a measured detection depth distribution agreed well with the calculated distribution by MCNP, the unfolded spectrum was significantly different from the calculated neutron spectrum due to contribution of the side neutron incidence. Therefore, we designed a new neutron collimator consisting of a polyethylene pre-collimator and boron carbide neutron absorber and confirmed numerically that it could suppress the side incident neutrons and shape the neutron flux to be like a pencil beam.

  4. Computational characterization and experimental validation of the thermal neutron source for neutron capture therapy research at the University of Missouri

    Energy Technology Data Exchange (ETDEWEB)

    Broekman, J. D. [University of Missouri, Research Reactor Center, 1513 Research Park Drive, Columbia, MO 65211-3400 (United States); Nigg, D. W. [Idaho National Laboratory, PO Box 1625, Idaho Falls, ID 83415 (United States); Hawthorne, M. F. [University of Missouri, International Institute of Nano and Molecular Medicine, 1514 Research Park Dr., Columbia, MO 65211-3450 (United States)

    2013-07-01

    Parameter studies, design calculations and neutronic performance measurements have been completed for a new thermal neutron beamline constructed for neutron capture therapy cell and small-animal radiobiology studies at the University of Missouri Research Reactor. The beamline features the use of single-crystal silicon and bismuth sections for neutron filtering and for reduction of incident gamma radiation. The computational models used for the final beam design and performance evaluation are based on coupled discrete-ordinates and Monte Carlo techniques that permit detailed modeling of the neutron transmission properties of the filtering crystals with very few approximations. Validation protocols based on neutron activation spectrometry measurements and rigorous least-square adjustment techniques show that the beam produces a neutron spectrum that has the anticipated level of thermal neutron flux and a somewhat higher than expected, but radio-biologically insignificant, epithermal neutron flux component. (authors)

  5. Standard Practice for Evaluating Solar Absorptive Materials for Thermal Applications

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    2007-01-01

    1.1 This practice covers a testing methodology for evaluating absorptive materials used in flat plate or concentrating collectors, with concentrating ratios not to exceed five, for solar thermal applications. This practice is not intended to be used for the evaluation of absorptive surfaces that are (1) used in direct contact with, or suspended in, a heat-transfer liquid, (that is, trickle collectors, direct absorption fluids, etc.); (2) used in evacuated collectors; or (3) used in collectors without cover plate(s). 1.2 Test methods included in this practice are property measurement tests and aging tests. Property measurement tests provide for the determination of various properties of absorptive materials, for example, absorptance, emittance, and appearance. Aging tests provide for exposure of absorptive materials to environments that may induce changes in the properties of test specimens. Measuring properties before and after an aging test provides a means of determining the effect of the exposure. 1.3 Th...

  6. Distribution of thermal neutron flux around a PET cyclotron.

    Science.gov (United States)

    Ogata, Yoshimune; Ishigure, Nobuhito; Mochizuki, Shingo; Ito, Kengo; Hatano, Kentaro; Abe, Junichiro; Miyahara, Hiroshi; Masumoto, Kazuyoshi; Nakamura, Hajime

    2011-05-01

    The number of positron emission tomography (PET) examinations has greatly increased world-wide. Since positron emission nuclides for the PET examinations have short half-lives, they are mainly produced using on-site cyclotrons. During the production of the nuclides, significant quantities of neutrons are generated from the cyclotrons. Neutrons have potential to activate the materials around the cyclotrons and cause exposure to the staff. To investigate quantities and distribution of the thermal neutrons, thermal neutron fluxes were measured around a PET cyclotron in a laboratory associating with a hospital. The cyclotron accelerates protons up to 18 MeV, and the mean particle current is 20 μA. The neutron fluxes were measured during both 18F production and C production. Gold foils and thermoluminescent dosimeter (TLD) badges were used to measure the neutron fluxes. The neutron fluxes in the target box averaged 9.3 × 10(6) cm(-2) s(-1) and 1.7 × 10(6) cm(-2) s(-1) during 18F and 11C production, respectively. Those in the cyclotron room averaged 4.1 × 10(5) cm(-2) s(-1) and 1.2 × 10(5) cm(-2) s(-1), respectively. Those outside the concrete wall shielding were estimated as being equal to or less than ∼3 cm s, which corresponded to 0.1 μSv h(-1) in effective dose. The neutron fluxes outside the concrete shielding were confirmed to be quite low compared to the legal limit.

  7. Magneto–Thermal Evolution of Neutron Stars with Emphasis to ...

    Indian Academy of Sciences (India)

    U. Geppert

    2017-09-12

    Sep 12, 2017 ... ties by building up enormous magnetic stresses in the crystallized crust (Perna & Pons 2011; Lyutikov 2015;. Gourgouliatoset al.2015). It provides also by its ..... of neutron stars relies on the fact that electric charges are carriers of both thermal and elec- tric currents, it depends crucially on the maintenance ...

  8. Shape Isomer in 236U Populated by Thermal Neutron Capture

    DEFF Research Database (Denmark)

    Andersen, Verner; Christensen, Carl Jørgen; Borggreen, J.

    1976-01-01

    The 116 ns shape isomer in 236U was populated by thermal neutron capture. Conversion electrons and X-rays were detected simultaneously in delayed coincidence with fission. The ratio of delayed to prompt fission was measured with the result, σIIf/σf = (1.0±0.2) × 10−5. A branching of the isomeric...

  9. Thermalization time in a model of neutron star

    OpenAIRE

    Ducomet, B.; Nečasová, Š. (Šárka)

    2011-01-01

    We consider an initial boundary value problem for the equation describing heat conduction in a spherical model of neutron star considered by Lattimer et al. We estimate the asymptotic decay of the solution, which provides a plausible estimate for a "thermalization time" for the system.

  10. Damage formation and optical absorption in neutron irradiated SiC

    Energy Technology Data Exchange (ETDEWEB)

    Wendler, E., E-mail: elke.wendler@uni-jena.de [Institut fuer Festkoerperphysik, Friedrich-Schiller-Universitaet Jena, Max-Wien-Platz 1, 07743 Jena (Germany); Bierschenk, Th.; Felgentraeger, F.; Sommerfeld, J.; Wesch, W. [Institut fuer Festkoerperphysik, Friedrich-Schiller-Universitaet Jena, Max-Wien-Platz 1, 07743 Jena (Germany); Alber, D.; Bukalis, G. [Campus Lise-Meitner, Abteilung F-A1, Elementanalytik, Helmholtz-Zentrum Berlin fuer Materialien und Energie GmbH, Hahn-Meitner-Platz 1, 14109 Berlin (Germany); Prinsloo, L.C.; Berg, N. van der; Friedland, E.; Malherbe, J.B. [Department of Physics, University of Pretoria, 0002 Pretoria (South Africa)

    2012-09-01

    The defect formation in neutron irradiated SiC was investigated by means of Rutherford backscattering spectrometry in channelling mode (RBS), optical absorption and Raman spectroscopy. The relative defect concentration determined by RBS increases linearly with the neutron fluence without any saturation in the investigated fluence region. The spectral dependence of the absorption coefficient {alpha} at photon energies below 3.2 eV is independent of the neutron fluence and corresponds to that observed in low-fluence ion implanted SiC. An increase of the defect concentration exhibits only in an increase of the absolute value of {alpha}. For photon energies above 3.3 eV again an exponential increase of the absorption coefficient is found but with a slope increasing with rising defect concentration. This absorption is assumed to be of the Urbach type. Around 1.56 eV a broad absorption band is observed which is most probably caused by divacancies V{sub Si}V{sub C}. The defects produced by the neutron irradiation of SiC result in a decrease of the peak intensity and a shift of the position of TO and LO Raman peaks towards lower wave numbers. The latter can be explained by tensile stress due to defects and mass increase of lattice atoms due to neutron capturing.

  11. Using lamb waves tomonitor moisture absorption thermally fatigues composite laminates

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Jae Sun; Cho, Youn Ho [School of Mechanical Engineering, Pusan National University, Busan (Korea, Republic of)

    2016-06-15

    Nondestructive evaluation for material health monitoring is important in aerospace industries. Composite laminates are exposed to heat cyclic loading and humid environment depending on flight conditions. Cyclic heat loading and moisture absorption may lead to material degradation such as matrix breaking, debonding, and delamination. In this paper, the moisture absorption ratio was investigated by measuring the Lamb wave velocity. The composite laminates were manufactured and subjected to different thermal aging cycles and moisture absorption. For various conditions of these cycles, not only changes in weight and also ultrasonic wave velocity were measured, and the Lamb wave velocity at various levels of moisture on a carbon-epoxy plate was investigated. Results from the experiment show a linear correlation between moisture absorption ratio and Lamb wave velocity at different thermal fatigue stages. The presented method can be applied as an alternative solution in the online monitoring of composite laminate moisture levels in commercial flights.

  12. Method for manufacturing solid-state thermal neutron detectors with simultaneous high thermal neutron detection efficiency (>50%) and neutron to gamma discrimination (>1.0E4)

    Science.gov (United States)

    Nikolic, Rebecca J.; Conway, Adam M.; Heineck, Daniel; Voss, Lars F.; Wang, Tzu Fang; Shao, Qinghui

    2013-10-15

    Methods for manufacturing solid-state thermal neutron detectors with simultaneous high thermal neutron detection efficiency (>50%) and neutron to gamma discrimination (>10.sup.4) are provided. A structure is provided that includes a p+ region on a first side of an intrinsic region and an n+ region on a second side of the intrinsic region. The thickness of the intrinsic region is minimized to achieve a desired gamma discrimination factor of at least 1.0E+04. Material is removed from one of the p+ region or the n+ region and into the intrinsic layer to produce pillars with open space between each pillar. The open space is filed with a neutron sensitive material. An electrode is placed in contact with the pillars and another electrode is placed in contact with the side that is opposite of the intrinsic layer with respect to the first electrode.

  13. Effects of high thermal neutron fluences on Type 6061 aluminum

    Energy Technology Data Exchange (ETDEWEB)

    Weeks, J.R.; Czajkowski, C.J. (Brookhaven National Lab., Upton, NY (United States)); Farrell, K. (Oak Ridge National Lab., TN (United States))

    1992-01-01

    The control rod drive follower tubes of the High Flux Beam Reactor are contructed from precipitation-hardened 6061-T6 aluminum alloy and they operate in the high thermal neutron flux regions of the core. It is shown that large thermal neutron fluences up to {approximately}4 {times} 10{sup 23} n/cm{sup 2} at 333K cause large increases in tensile strength and relatively modest decreases in tensile elongation while significantly reducing the notch impact toughness at room temperature. These changes are attributed to the development of a fine distribution of precipitates of amorphous silicon of which about 8% is produced radiogenically. A proposed role of thermal-to-fast flux ratio is discussed.

  14. Effects of high thermal neutron fluences on Type 6061 aluminum

    Energy Technology Data Exchange (ETDEWEB)

    Weeks, J.R.; Czajkowski, C.J. [Brookhaven National Lab., Upton, NY (United States); Farrell, K. [Oak Ridge National Lab., TN (United States)

    1992-09-01

    The control rod drive follower tubes of the High Flux Beam Reactor are contructed from precipitation-hardened 6061-T6 aluminum alloy and they operate in the high thermal neutron flux regions of the core. It is shown that large thermal neutron fluences up to {approximately}4 {times} 10{sup 23} n/cm{sup 2} at 333K cause large increases in tensile strength and relatively modest decreases in tensile elongation while significantly reducing the notch impact toughness at room temperature. These changes are attributed to the development of a fine distribution of precipitates of amorphous silicon of which about 8% is produced radiogenically. A proposed role of thermal-to-fast flux ratio is discussed.

  15. New thermal neutron calibration channel at LNMRI/IRD

    Energy Technology Data Exchange (ETDEWEB)

    Astuto, A.; Lopes, R.T., E-mail: achillesbr@gmail.com [Coordenacao dos Programas de Pos-Graduacao em Engenharia (COPPE/UFRJ), Rio de Janeiro, RJ (Brazil); Patrao, K.C.S.; Fonseca, E.S.; Pereira, W.W. [Instituto de Radioprotecao e Dosimetria (IRD/CNEN-RJ/LNMRI), Rio de Janeiro, RJ (Brazil). Lab. Nacional de Metrologia das Radiacoes Ionizantes

    2015-07-01

    A new standard thermal neutron flux unit was designed in the National Ionizing Radiation Metrology Laboratory (LNMRI) for calibration of neutron detectors. Fluence is achieved by moderation of four {sup 241}Am-Be sources with 596 GBq each, in a facility built with graphite and paraffin blocks. The study was divided into two stages. First, simulations were performed using MCNPX code in different geometric arrangements, seeking the best performance in terms of fluence and their uncertainties. Last, the system was assembled based on the results obtained on the simulations. The simulation results indicate quasi-homogeneous fluence (less than 1%) in the central chamber. (author)

  16. Thermal Neutron Capture Cross Sections of the PalladiumIsotopes

    Energy Technology Data Exchange (ETDEWEB)

    Firestone, R.B.; Krticka, M.; McNabb, D.P.; Sleaford, B.; Agvaanluvsan, U.; Belgya, T.; Revay, Zs.

    2006-07-17

    Precise gamma-ray thermal neutron capture cross sectionshave been measured at the Budapest Reactor for all elements withZ=1-83,92 except for He and Pm. These measurements and additional datafrom the literature been compiled to generate the Evaluated Gamma-rayActivation File (EGAF), which is disseminated by LBNL and the IAEA. Thesedata are nearly complete for most isotopes with Z<20 so the totalradiative thermal neutron capture cross sections can be determineddirectly from the decay scheme. For light isotopes agreement with therecommended values is generally satisfactory although large discrepanciesexist for 11B, 12,13C, 15N, 28,30Si, 34S, 37Cl, and 40,41K. Neutroncapture decay data for heavier isotopes are typically incomplete due tothe contribution of unresolved continuum transitions so only partialradiative thermal neutron capture cross sections can be determined. Thecontribution of the continuum to theneutron capture decay scheme arisesfrom a large number of unresolved levels and transitions and can becalculated by assuming that the fluctuations in level densities andtransition probabilities are statistical. We have calculated thecontinuum contribution to neutron capture decay for the palladiumisotopes with the Monte Carlo code DICEBOX. These calculations werenormalized to the experimental cross sections deexciting low excitationlevels to determine the total radiative thermal neutron capture crosssection. The resulting palladium cross sections values were determinedwith a precision comparable to the recommended values even when only onegamma-ray cross section was measured. The calculated and experimentallevel feedings could also be compared to determine spin and parityassignments for low-lying levels.

  17. Diffusion cooling of thermal neutrons in basic rock minerals by Monte Carlo simulation of the pulsed neutron experiments

    Energy Technology Data Exchange (ETDEWEB)

    Drozdowicz, K. E-mail: Krzysztof.Drozdowicz@ifj.edu.pl; Krynicka, E.; Dabrowska, J

    2003-06-01

    The pulsed neutron experiment (the variable geometric buckling experiment) in spherical geometry has been simulated using the MCNP code. The time decay of the thermal neutron flux has been observed as a function of the sample size. The thermal neutron diffusion cooling coefficient C with the correction F has been determined for three basic rock minerals (quartz, calcite, dolomite) at the given specific densities. The corresponding density-removed parameters have also been obtained.

  18. Standard Test Method for Determining Thermal Neutron Reaction Rates and Thermal Neutron Fluence Rates by Radioactivation Techniques

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    2008-01-01

    1.1 The purpose of this test method is to define a general procedure for determining an unknown thermal-neutron fluence rate by neutron activation techniques. It is not practicable to describe completely a technique applicable to the large number of experimental situations that require the measurement of a thermal-neutron fluence rate. Therefore, this method is presented so that the user may adapt to his particular situation the fundamental procedures of the following techniques. 1.1.1 Radiometric counting technique using pure cobalt, pure gold, pure indium, cobalt-aluminum, alloy, gold-aluminum alloy, or indium-aluminum alloy. 1.1.2 Standard comparison technique using pure gold, or gold-aluminum alloy, and 1.1.3 Secondary standard comparison techniques using pure indium, indium-aluminum alloy, pure dysprosium, or dysprosium-aluminum alloy. 1.2 The techniques presented are limited to measurements at room temperatures. However, special problems when making thermal-neutron fluence rate measurements in high-...

  19. Handheld dual thermal neutron detector and gamma-ray spectrometer

    Science.gov (United States)

    Stowe, Ashley C.; Burger, Arnold; Bhattacharya, Pijush; Tupitsyn, Yevgeniy

    2017-05-02

    A combined thermal neutron detector and gamma-ray spectrometer system, including: a first detection medium including a lithium chalcopyrite crystal operable for detecting neutrons; a gamma ray shielding material disposed adjacent to the first detection medium; a second detection medium including one of a doped metal halide, an elpasolite, and a high Z semiconductor scintillator crystal operable for detecting gamma rays; a neutron shielding material disposed adjacent to the second detection medium; and a photodetector coupled to the second detection medium also operable for detecting the gamma rays; wherein the first detection medium and the second detection medium do not overlap in an orthogonal plane to a radiation flux. Optionally, the first detection medium includes a .sup.6LiInSe.sub.2 crystal. Optionally, the second detection medium includes a SrI.sub.2(Eu) scintillation crystal.

  20. Thermal properties of carbon black aqueous nanofluids for solar absorption

    Directory of Open Access Journals (Sweden)

    Han Dongxiao

    2011-01-01

    Full Text Available Abstract In this article, carbon black nanofluids were prepared by dispersing the pretreated carbon black powder into distilled water. The size and morphology of the nanoparticles were explored. The photothermal properties, optical properties, rheological behaviors, and thermal conductivities of the nanofluids were also investigated. The results showed that the nanofluids of high-volume fraction had better photothermal properties. Both carbon black powder and nanofluids had good absorption in the whole wavelength ranging from 200 to 2,500 nm. The nanofluids exhibited a shear thinning behavior. The shear viscosity increased with the increasing volume fraction and decreased with the increasing temperature at the same shear rate. The thermal conductivity of carbon black nanofluids increased with the increase of volume fraction and temperature. Carbon black nanofluids had good absorption ability of solar energy and can effectively enhance the solar absorption efficiency.

  1. Optical absorption of neutron-irradiated silica fibers

    Energy Technology Data Exchange (ETDEWEB)

    Cooke, D.W.; Farnum, E.H.; Bennett, B.L. [Los Alamos National Lab., NM (United States)

    1996-10-01

    Induced-loss spectra of silica-based optical fibers exposed to high (10{sup 23} n-m{sup {minus}2}) and low (10{sup 21} n-m{sup {minus}2}) fluences of neutrons at the Los Alamos Spallation Radiation Effects Facility (LASREF) have been measured. Two types of fibers consisting of a pure fused silica core with fluorine-doped ({approximately}4 mole %) cladding were obtained from Fiberguide Industries and used in the as-received condition. Anhydroguide{trademark} and superguide{trademark} fibers contained less than 1 ppm, and 600 to 800 ppm of OH, respectively. The data suggest that presently available silica fibers can be used in plasma diagnostics, but the choice and suitability depends upon the spectral region of interest. Low-OH content fibers can be used for diagnostic purposes in the interval {approximately}800 to 1400 mn if the exposure is to high-fluence neutrons. For low-fluence neutron exposures, the low-OH content fibers are best suited for use in the interval {approximately}800 to 2000 nm, and the high-OH content fibers are the choice for the interval {approximately}400 to 800 nm.

  2. The PTB thermal neutron reference field at GeNF

    Energy Technology Data Exchange (ETDEWEB)

    Boettger, R.; Friedrich, H.; Janssen, H.

    2004-07-01

    The experimental setup and procedure for the characterization of the thermal neutron reference field established at the Geesthacht neutron facility (GeNF) of the GKSS is described. The neutron beam, free in air, with a maximum flux of 10{sup 6} s{sup -1}, can easily be reduced to less than 10{sup 4} s{sup -1} by using a diaphragm variable in size and without changing the beam divergence. Also, the spectral distribution with a mean energy of 45 meV, measured by time-of-flight over a 6.6 m long flight path, is independent of the beam current chosen. In the 2002/2003 experiments reported here, a {sup 6}Li glass detector was employed to determine the absolute beam current and to calibrate the {sup 3}He transmission beam monitor. In addition, activation measurements of gold foils were carried out at a reduced beam divergence. The results agree within {+-}2%. Furthermore, the beam is characterized by a low gamma background intensity and a negligible fraction of epithermal neutrons. Irradiations in combination with a scanner device to achieve a homogeneously illuminated scan field have shown that the thermal beam is well suited for dosemeter development and for the calibration of radiation protection instruments. (orig.)

  3. Physics of epi-thermal boron neutron capture therapy (epi-thermal BNCT).

    Science.gov (United States)

    Seki, Ryoichi; Wakisaka, Yushi; Morimoto, Nami; Takashina, Masaaki; Koizumi, Masahiko; Toki, Hiroshi; Fukuda, Mitsuhiro

    2017-12-01

    The physics of epi-thermal neutrons in the human body is discussed in the effort to clarify the nature of the unique radiologic properties of boron neutron capture therapy (BNCT). This discussion leads to the computational method of Monte Carlo simulation in BNCT. The method is discussed through two examples based on model phantoms. The physics is kept at an introductory level in the discussion in this tutorial review.

  4. A novel detector assembly for detecting thermal neutrons, fast neutrons and gamma rays

    Energy Technology Data Exchange (ETDEWEB)

    Cester, D., E-mail: davide.cester@gmail.com [Dipartimento di Fisica ed Astronomia dell' Università di Padova, Via Marzolo 8, I-35131 Padova (Italy); Lunardon, M.; Moretto, S. [Dipartimento di Fisica ed Astronomia dell' Università di Padova, Via Marzolo 8, I-35131 Padova (Italy); INFN Sezione di Padova, Via Marzolo 8, I-35131 Padova (Italy); Nebbia, G. [INFN Sezione di Padova, Via Marzolo 8, I-35131 Padova (Italy); Pino, F. [Dipartimento di Fisica ed Astronomia dell' Università di Padova, Via Marzolo 8, I-35131 Padova (Italy); Sajo-Bohus, L. [Dipartimento di Fisica ed Astronomia dell' Università di Padova, Via Marzolo 8, I-35131 Padova (Italy); Laboratorio de Fisica Nuclear, Universidad Simon Bolivar, Apartado 89000, 1080 A Caracas (Venezuela, Bolivarian Republic of); Stevanato, L.; Bonesso, I.; Turato, F. [Dipartimento di Fisica ed Astronomia dell' Università di Padova, Via Marzolo 8, I-35131 Padova (Italy)

    2016-09-11

    A new composite detector has been developed by combining two different commercial scintillators. The device has the capability to detect gamma rays as well as thermal and fast neutrons; the signal discrimination between the three types is performed on-line by means of waveform digitizers and PSD algorithms. This work describes the assembled detector and its discrimination performance to be employed in the applied field.

  5. The thermal neutron scattering cross section of {sup 86}Kr

    Energy Technology Data Exchange (ETDEWEB)

    Terburg, B.P.

    1992-05-01

    The availability of 27 1 STP krypton-86 gas, an isotope with unknown thermal neutron scattering cross section, was an excellent occasion to determine the (bound atom) scattering cross section and its coherent part by application of the neutron transmission method and neutron interferometry. The transmission method was applied in a diffractometer, a Larmor spectrometer and a TOF-spectrometer. In addition to {sup 86}Kr also natural krypton ({sup n}Kr) was used for sample in the diffractometer. The diffractometer measurements result in bound atom scattering cross sections {sigma}{sub s}=8.92(46) b for {sup 86}Kr and {sigma}{sub s}=7.08(95) b for {sup n}Kr. The Larmor transmission measurements lead to a final result {sigma}{sub s}=8.44(9) b for {sup 86}Kr. In the TOF-spectrometer the wavelength-dependent total cross section of water was determined. Coherent neutron scattering lengths were determined using the neutron interferometry method with a skew symmetric neutron interferometer. Scans with {sup 86}Kr and {sup n}Kr led to b{sub c}=8.07(26) fm for {sup 86}Kr and 7.72(33) fm for {sup n}Kr, corresponding to coherent scattering cross sections {sigma}{sub c}=8.18(53) b and 7.49(64) b respectively. Due to the large errors in the bound atom scattering cross section and coherent scattering cross section of {sup 86}Kr and {sup n}Kr, the incoherent cross section of both gases, {sigma}{sub i} = 0 within its inaccuracy, {sigma}{sub i}=0.26(54) b for {sup 86}Kr and {sigma}{sub i}=0.41(1.15) b for {sup n}Kr. (orig.).

  6. A militarily fielded thermal neutron activation sensor for landmine detection

    Energy Technology Data Exchange (ETDEWEB)

    Clifford, E.T.H. [Bubble Technology Industries, Chalk River (Canada); McFee, J.E. [Defence R and D Canada-Suffield, Medicine Hat (Canada)], E-mail: john.mcfee@drdc-rddc.gc.ca; Ing, H.; Andrews, H.R.; Tennant, D.; Harper, E. [Bubble Technology Industries, Chalk River (Canada); Faust, A.A. [Defence R and D Canada-Suffield, Medicine Hat (Canada)

    2007-08-21

    The Canadian Department of National Defence has developed a teleoperated, vehicle-mounted, multi-sensor system to detect anti-tank landmines on roads and tracks in peacekeeping operations. A key part of the system is a thermal neutron activation (TNA) sensor which is placed above a suspect location to within a 30 cm radius and confirms the presence of explosives via detection of the 10.835 MeV gamma ray associated with thermal neutron capture on {sup 14}N. The TNA uses a 100{mu}g{sup 252}Cf neutron source surrounded by four 7.62cmx7.62cm NaI(Tl) detectors. The system, consisting of the TNA sensor head, including source, detectors and shielding, the high-rate, fast pulse processing electronics and the data processing methodology are described. Results of experiments to characterize detection performance are also described. The experiments have shown that anti-tank mines buried 10 cm or less can be detected in roughly a minute or less, but deeper mines and mines significantly displaced horizontally take considerably longer time. Mines as deep as 30 cm can be detected for long count times (1000 s). Four TNA detectors are now in service with the Canadian Forces as part of the four multi-sensor systems, making it the first militarily fielded TNA sensor and the first militarily fielded confirmation sensor for landmines. The ability to function well in adverse climatic conditions has been demonstrated, both in trials and operations.

  7. Measurements of the thermal neutron flux for an accelerator-based photoneutron source.

    Science.gov (United States)

    Taheri, Ali; Pazirandeh, Ali

    2016-12-01

    To have access to an appropriate neutron source is one of the most demanding requirements for neutron studies. This is important specially in laboratory and clinical applications, which need more compact and accessible sources. The most known neutron sources are fission reactors and natural isotopes, but there is an increasing interest for using accelerator based neutron sources because of their advantages. In this paper, we shall present a photo-neutron source prototype which is designed and fabricated to be used for different neutron researches including in-laboratory neutron activation analysis and neutron imaging, and also preliminary studies in boron neutron capture therapy (BNCT). Series of experimental tests were conducted to examine the intensity and quality of the neutron field produced by this source. Monte-Carlo simulations were also utilized to provide more detailed evaluation of the neutron spectrum, and determine the accuracy of the experiments. The experiments demonstrated a thermal neutron flux in the order of 10(7) (n/cm(2).s), while simulations affirmed this flux and showed a neutron spectrum with a sharp peak at thermal energy region. According to the results, about 60 % of produced neutrons are in the range of thermal to epithermal neutrons.

  8. Large solid-angle polarisation analysis at thermal neutron wavelengths using a sup 3 He spin filter

    CERN Document Server

    Heil, W; Cywinski, R; Humblot, H; Ritter, C; Roberts, T W; Stewart, J R

    2002-01-01

    The strongly spin-dependent absorption of neutrons in nuclear spin-polarised sup 3 He opens up the possibility of polarising neutrons from reactors and spallation sources over the full kinematical range of cold, thermal and hot neutrons. In this paper we describe the first large solid-angle polarisation analysis measurement using a sup 3 He neutron spin filter at thermal neutron wavelengths (lambda=2.5 A). This experiment was performed on the two-axis diffractometer D1B at the Institut Laue-Langevin using a banana-shaped filter cell (530 cm sup 3 ) filled with sup 3 He gas with a polarisation of P=52% at a pressure of 2.7 bar. A comparison is made with a previous measurement on D7 using a cold neutron beam on the same sample, i.e. amorphous ErY sub 6 Ni sub 3. Using uniaxial polarisation analysis both the nuclear and magnetic cross-sections could be extracted over the range of scattering-vectors [0.5<=Q(A sup - sup 1)<=3.5]. The results are in qualitative and quantitative agreement with the D7-data, whe...

  9. Thermal noise reduction and absorption optimization via multimaterial coatings

    Science.gov (United States)

    Steinlechner, Jessica; Martin, Iain W.; Hough, Jim; Krüger, Christoph; Rowan, Sheila; Schnabel, Roman

    2015-02-01

    Future gravitational wave detectors (GWDs) such as Advanced LIGO upgrades and the Einstein Telescope are planned to operate at cryogenic temperatures using crystalline silicon (cSi) test-mass mirrors at an operation wavelength of 1550 nm. The reduction in temperature in principle provides a direct reduction in coating thermal noise, but the presently used coating stacks which are composed of silica (SiO2) and tantala (Ta2O5) show cryogenic loss peaks which results in less thermal noise improvement than might be expected. Due to low mechanical loss at low temperature amorphous silicon (aSi) is a very promising candidate material for dielectric mirror coatings and could replace Ta2O5. Unfortunately, such an aSi /SiO2 coating is not suitable for use in GWDs due to high optical absorption in aSi coatings. We explore the use of a three material based coating stack. In this multimaterial design the low absorbing Ta2O5 in the outermost coating layers significantly reduces the incident light power, while aSi is used only in the lower bilayers to maintain low optical absorption. Such a coating design would enable a reduction of Brownian thermal noise by 25%. We show experimentally that an optical absorption of only (5.3 ±0.4 ) ppm at 1550 nm should be achievable.

  10. Thermal stability of Co Ti multilayered neutron polarizers

    Science.gov (United States)

    Mâaza, M.; Spegel, M.; Sella, C.; Pardo, B.; Menelle, A.; Corno, J.; Gaziel, R.

    1999-09-01

    Thermal stability of multilayered Co-Ti neutron optic polarizers with a period of the order of 103 Å is investigated. The diffusion kinetics is determined by using the Du Mond and Youtz's method with grazing angle neutron reflectometry in the temperature range of 293-723 K. It was found that the diffusion is mainly directed from Co-layers towards the Ti-layers. The effective interdiffusion coefficient Deff of cobalt into titanium is calculated from the rate of decrease of the first reflected Bragg peak related to the artificial periodicity of the multilayer with the annealing temperature T. The temperature dependence of Deff is found to be described approximately by Deff≈( D0 exp (-0.25 eV/k BT)) cm 2 s -1.

  11. Optimization of Thermal Neutron Converter in SiC Sensors for Spectral Radiation Measurements

    Energy Technology Data Exchange (ETDEWEB)

    Krolikowski, Igor; Cetnar, Jerzy [Department of Nuclear Energy, Faculty of Energy and Fuels at AGH University of Science and Technology, Al. Mickiewicza 30, 30-059 Cracow (Poland); Issa, Fatima; Ferrone, Raffaello; Ottaviani, Laurent [IM2NP, UMR CNRS 7334, Aix-Marseille University, Case 231, 13397 Marseille Cedex 20 (France); Szalkai, Dora; Klix, Axel [KIT- Karlsruhe Institute of Technology, Institute of Neutron Physics and Reactor Technology, Karlsruhe 76344 (Germany); Vermeeren, Ludo [SCK-CEN, Boeretang 200, B-2400 Mol (Belgium); Lyoussi, Abdalla [CEA, DEN, DER, Instrumentation Sensors and Dosimetry Laboratory, Cadarache, F-13108 St-Paul-Lez-Durance (France); Saenger, Richard [Etudes et Productions Schlumberger, Clamart (France)

    2015-07-01

    Optimization of the neutron converter in SiC sensors is presented. The sensors are used for spectral radiation measurements of thermal and fast neutrons and optionally gamma ray at elevated temperature in harsh radiation environment. The neutron converter, which is based on 10B, allows to detect thermal neutrons by means of neutron capture reaction. Two construction of the sensors were used to measure radiation in experiments. Sensor responses collected in experiments have been reproduced by the computer tool created by authors, it allows to validate the tool. The tool creates the response matrix function describing the characteristic of the sensors and it was used for detailed analyses of the sensor responses. Obtained results help to optimize the neutron converter in order to increase thermal neutron detection. Several enhanced construction of the sensors, which includes the neutron converter based on {sup 10}B or {sup 6}Li, were proposed. (authors)

  12. The n{sub T}OF Total Absorption Calorimeter for neutron capture measurements at CERN

    Energy Technology Data Exchange (ETDEWEB)

    Guerrero, C. [Centro de Investigaciones Energeticas Medioambientales y Tecnologicas, Madrid (Spain)], E-mail: carlos.guerrero@ciemat.es; Abbondanno, U. [Istituto Nazionale di Fisica Nucleare, Trieste (Italy); Aerts, G. [CEA/Saclay - DSM/DAPNIA, Gif-sur-Yvette (France); Alvarez, H. [Universidade de Santiago de Compostela (Spain); Alvarez-Velarde, F. [Centro de Investigaciones Energeticas Medioambientales y Tecnologicas, Madrid (Spain); Andriamonje, S. [CEA/Saclay - DSM/DAPNIA, Gif-sur-Yvette (France); Andrzejewski, J. [University of Lodz, Lodz (Poland); Assimakopoulos, P. [University of Ioannina (Greece); Audouin, L. [Centre National de la Recherche Scientifique/IN2P3-IReS, Strasbourg (France); Badurek, G. [Atominstitut der Osterreichischen Universitaeten, Technische Universitaet Wien (Austria); Baumann, P. [Centre National de la Recherche Scientifique/IN2P3-IReS, Strasbourg (France); Becvar, F. [Charles University, Prague (Czech Republic); Berthoumieux, E. [CEA/Saclay - DSM/DAPNIA, Gif-sur-Yvette (France); Calvino, F. [Universidad Politecnica de Catalunya (Spain); Calviani, M. [Istituto Nazionale di Fisica Nucleare (INFN), Laboratori Nazionali di Legnaro (Italy); Cano-Ott, D. [Centro de Investigaciones Energeticas Medioambientales y Tecnologicas, Madrid (Spain); Capote, R. [International Atomic Energy Agency (IAEA), Nuclear Data Section, Vienna (Austria); Universidad de Sevilla (Spain); Carrapico, C. [CEA/Saclay - DSM/DAPNIA, Gif-sur-Yvette (France); Instituto Tecnologico e Nuclear(ITN), Lisbon (Portugal); Cennini, P. [CERN, Geneva (Switzerland); Chepel, V. [LIP - Coimbra and Departamento de Fisica da Universidade de Coimbra (Portugal)] (and others)

    2009-09-21

    The n{sub T}OF Collaboration has built and commissioned a high-performance detector for (n,{gamma}) measurements called the Total Absorption Calorimeter (TAC). The TAC was especially designed for measuring neutron capture cross-sections of low-mass and/or radioactive samples with the accuracy required for nuclear technology and stellar nucleosynthesis. We present a detailed description of the TAC and discuss its overall performance in terms of energy and time resolution, background discrimination, detection efficiency and neutron sensitivity.

  13. Assessment of fast and thermal neutron ambient dose equivalents around the KFUPM neutron source storage area using nuclear track detectors

    Energy Technology Data Exchange (ETDEWEB)

    Fazal-ur-Rehman [Physics Department, King Fahd University of Petroleum and Minerals, Dhahran 31261 (Saudi Arabia)]. E-mail: fazalr@kfupm.edu.sa; Al-Jarallah, M.I. [Physics Department, King Fahd University of Petroleum and Minerals, Dhahran 31261 (Saudi Arabia); Abu-Jarad, F. [Radiation Protection Unit, Environmental Protection Department, Saudi Aramco, P. O. Box 13027, Dhahran 31311 (Saudi Arabia); Qureshi, M.A. [Center for Applied Physical Sciences, King Fahd University of Petroleum and Minerals, Dhahran 31261 (Saudi Arabia)

    2005-11-15

    A set of five {sup 241}Am-Be neutron sources are utilized in research and teaching at King Fahd University of Petroleum and Minerals (KFUPM). Three of these sources have an activity of 16Ci each and the other two are of 5Ci each. A well-shielded storage area was designed for these sources. The aim of the study is to check the effectiveness of shielding of the KFUPM neutron source storage area. Poly allyl diglycol carbonate (PADC) Nuclear track detectors (NTDs) based fast and thermal neutron area passive dosimeters have been utilized side by side for 33 days to assess accumulated low ambient dose equivalents of fast and thermal neutrons at 30 different locations around the source storage area and adjacent rooms. Fast neutron measurements have been carried out using bare NTDs, which register fast neutrons through recoils of protons, in the detector material. NTDs were mounted with lithium tetra borate (Li{sub 2}B{sub 4}O{sub 7}) converters on their surfaces for thermal neutron detection via B10(n,{alpha})Li6 and Li6(n,{alpha})H3 nuclear reactions. The calibration factors of NTD both for fast and thermal neutron area passive dosimeters were determined using thermoluminescent dosimeters (TLD) with and without a polyethylene moderator. The calibration factors for fast and thermal neutron area passive dosimeters were found to be 1.33 proton tracks cm{sup -2}{mu}Sv{sup -1} and 31.5 alpha tracks cm{sup -2}{mu}Sv{sup -1}, respectively. The results show variations of accumulated dose with the locations around the storage area. The fast neutron dose equivalents rates varied from as low as 182nSvh{sup -1} up to 10.4{mu}Svh{sup -1} whereas those for thermal neutron ranged from as low as 7nSvh{sup -1} up to 9.3{mu}Svh{sup -1}. The study indicates that the area passive neutron dosimeter was able to detect dose rates as low as 7 and 182nSvh{sup -1} from accumulated dose for thermal and fast neutrons, respectively, which were not possible to detect with the available active neutron

  14. ESR-dosimetry in thermal and epithermal neutron fields for application in boron neutron capture therapy

    Energy Technology Data Exchange (ETDEWEB)

    Schmitz, Tobias

    2016-01-22

    Dosimetry is essential for every form of radiotherapy. In Boron Neutron Capture Therapy (BNCT) mixed neutron and gamma fields have to be considered. Dose is deposited in different neutron interactions with elements in the penetrated tissue and by gamma particles, which are always part of a neutron field. The therapeutic dose in BNCT is deposited by densely ionising particles, originating from the fragmentation of the isotope boron-10 after capture of a thermal neutron. Despite being investigated for decades, dosimetry in neutron beams or fields for BNCT remains complex, due to the variety in type and energy of the secondary particles. Today usually ionisation chambers combined with metal foils are used. The applied techniques require extensive effort and are time consuming, while the resulting uncertainties remain high. Consequently, the investigation of more effective techniques or alternative dosimeters is an important field of research. In this work the possibilities of ESR-dosimeters in those fields have been investigated. Certain materials, such as alanine, generate stable radicals upon irradiation. Using Electron Spin Resonance (ESR) spectrometry the amount of radicals, which is proportional to absorbed dose, can be quantified. Different ESR detector materials have been irradiated in the thermal neutron field of the research reactor TRIGA research reactor in Mainz, Germany, with five setups, generating different secondary particle spectra. Further irradiations have been conducted in two epithermal neutron beams. The detector response, however, strongly depends on the dose depositing particle type and energy. It is hence necessary to accompany measurements by computational modelling and simulation. In this work the Monte Carlo code FLUKA was used to calculate absorbed doses and dose components. The relative effectiveness (RE), linking absorbed dose and detector response, has been calculated using amorphous track models. For the simulation, detailed models of

  15. Detection of thermal neutrons using ZnS(Ag):6LiF neutron scintillator read out with WLS fibers and SiPMs

    Science.gov (United States)

    Hildebrandt, M.; Stoykov, A.; Mosset, J.-B.; Greuter, U.; Schlumpf, N.

    2016-07-01

    In this paper we present the development of a one-dimensional multi-channel thermal neutron detection system for the application in neutron scattering instrumentation, e.g. strain-scanning diffractometers. The detection system is based on ZnS(Ag):6LiF neutron scintillator with embedded WLS fibers which are read out with a SiPM. A dedicated signal processing system allows us to suppress the SiPM dark counts and to extract the signals from the neutron absorption events. For a single-channel detection unit which represents the elementary building block of this detection system we achieved a neutron detection efficiency of 65% at 1.2 Å, a background count rate <10-3 Hz and a gamma-sensitivity <10-6 (measured with a 60Co source), while the dead time is 20 μs and the multi-count ratio is < 1 %. This performance was achieved even for SiPM dark count rates of up to 2 MHz.

  16. Study and development of new dosemeters for thermal neutrons; Estudio y desarrollo de nuevos dosimetros para neutrones termicos

    Energy Technology Data Exchange (ETDEWEB)

    Urena N, F

    1998-12-31

    An alanine-boron compound, alanine hydroborate, was synthesized and chemically characterized to be used for thermal neutrons fluence measurements. The synthesis of the compound was made by reacting the amino acid alanine with boric acid in three different media: acidic, neutral and alkaline. Physicochemical analysis showed that the alkaline medium is favorable for the synthesis of the alanine hydroborate. The compound was evaluated as a thermal neutron fluence detector by the detection of the free radical yield upon neutron thermal irradiation by Electron Paramagnetic Resonance (EPR). The present work also studies the EPR-signal response of the three preparations to thermal neutron irradiation ({phi} = 5 x 10{sup 7} n/cm{sup 2} -s). The following EPR signal parameters of the samples were investigated: peak-to-peak signal intensity vs. thermal neutron fluence {Phi} = {phi} {Delta}t ; where {Delta}t = 1, 5, 10, 20, 40, 60, 80, 90, 100, 110 and 120 h. , peak-to-peak signal intensity vs. microwave power, signal fading; repeatability, batch homogeneity, stability and zero dose response. It is concluded that these new products could be used in thermal neutron fluence estimations. (Author)

  17. Double helix boron-10 powder thermal neutron detector

    Science.gov (United States)

    Wang, Zhehui; Morris, Christopher L.; Bacon, Jeffrey D.

    2015-06-02

    A double-helix Boron-10 powder detector having intrinsic thermal neutron detection efficiency comparable to 36'' long, 2-in diameter, 2-bar Helium-3 detectors, and which can be used to replace such detectors for use in portal monitoring, is described. An embodiment of the detector includes a metallic plate coated with Boron-10 powder for generating alpha and Lithium-7 particles responsive to neutrons impinging thereon supported by insulators affixed to at least two opposing edges; a grounded first wire wound in a helical manner around two opposing insulators; and a second wire having a smaller diameter than that of the first wire, wound in a helical manner around the same insulators and spaced apart from the first wire, the second wire being positively biased. A gas, disposed within a gas-tight container enclosing the plate, insulators and wires, and capable of stopping alpha and Lithium-7 particles and generating electrons produces a signal on the second wire which is detected and subsequently related to the number of neutrons impinging on the plate.

  18. Determination of the thermal and epithermal neutron sensitivities of an LBO chamber

    Energy Technology Data Exchange (ETDEWEB)

    Endo, Satoru; Kotani, Kei; Kajimoto, Tsuyoshi; Tanaka, Kenichi [Hiroshima University, Quantum Energy Applications, Graduate School of Engineering, Higashi-Hiroshima (Japan); Sato, Hitoshi; Nakajima, Erika [Ibaraki Prefectural University of Health Science, Radiological Sciences, Ibaraki (Japan); Shimazaki, Takuto [Hiroshima University, Quantum Energy Applications, Graduate School of Engineering, Higashi-Hiroshima (Japan); Delta Kogyo Co., Ltd., Hiroshima (Japan); Suda, Mitsuru; Hamano, Tsuyoshi [National Institute of Radiological Sciences, Chiba-Shi, Chiba (Japan); Hoshi, Masaharu [Hiroshima University, Institute for Peace Science, Hiroshima (Japan)

    2017-08-15

    An LBO (Li{sub 2}B{sub 4}O{sub 7}) walled ionization chamber was designed to monitor the epithermal neutron fluence in boron neutron capture therapy clinical irradiation. The thermal and epithermal neutron sensitivities of the device were evaluated using accelerator neutrons from the {sup 9}Be(d, n) reaction at a deuteron energy of 4 MeV (4 MeV d-Be neutrons). The response of the chamber in terms of the electric charge induced in the LBO chamber was compared with the thermal and epithermal neutron fluences measured using the gold-foil activation method. The thermal and epithermal neutron sensitivities obtained were expressed in units of pC cm{sup 2}, i.e., from the chamber response divided by neutron fluence (cm{sup -2}). The measured LBO chamber sensitivities were 2.23 x 10{sup -7} ± 0.34 x 10{sup -7} (pC cm{sup 2}) for thermal neutrons and 2.00 x 10{sup -5} ± 0.12 x 10{sup -5} (pC cm{sup 2}) for epithermal neutrons. This shows that the LBO chamber is sufficiently sensitive to epithermal neutrons to be useful for epithermal neutron monitoring in BNCT irradiation. (orig.)

  19. Determination of the thermal and epithermal neutron sensitivities of an LBO chamber.

    Science.gov (United States)

    Endo, Satoru; Sato, Hitoshi; Shimazaki, Takuto; Nakajima, Erika; Kotani, Kei; Suda, Mitsuru; Hamano, Tsuyoshi; Kajimoto, Tsuyoshi; Tanaka, Kenichi; Hoshi, Masaharu

    2017-08-01

    An LBO (Li2B4O7) walled ionization chamber was designed to monitor the epithermal neutron fluence in boron neutron capture therapy clinical irradiation. The thermal and epithermal neutron sensitivities of the device were evaluated using accelerator neutrons from the (9)Be(d, n) reaction at a deuteron energy of 4 MeV (4 MeV d-Be neutrons). The response of the chamber in terms of the electric charge induced in the LBO chamber was compared with the thermal and epithermal neutron fluences measured using the gold-foil activation method. The thermal and epithermal neutron sensitivities obtained were expressed in units of pC cm(2), i.e., from the chamber response divided by neutron fluence (cm(-2)). The measured LBO chamber sensitivities were 2.23 × 10(-7) ± 0.34 × 10(-7) (pC cm(2)) for thermal neutrons and 2.00 × 10(-5) ± 0.12 × 10(-5) (pC cm(2)) for epithermal neutrons. This shows that the LBO chamber is sufficiently sensitive to epithermal neutrons to be useful for epithermal neutron monitoring in BNCT irradiation.

  20. A generalized interpretation of buckling experiments for thermal neutrons

    Energy Technology Data Exchange (ETDEWEB)

    Woznicka, Urszula E-mail: urszula.woznicka@ifj.edu.pl; Drozdowicz, Krzysztof; Dabrowska, Joanna

    2000-12-11

    The buckling experiment is a well-known pulsed measurement method used to determine the thermal neutron diffusion parameters of a medium. In the classic form of the method, a dependence between the geometric buckling B{sup 2} (in cm{sup -2}) and the thermal neutron time decay constant {lambda} (in s{sup -1}) are involved. In the present paper, dimensionless values for the decay constant and for the buckling are introduced. This unification offers a method to generalize the description of the buckling experiment and makes it possible to compare experiments made for different media. The application of this procedure is exemplified on results for polyethylene of two different densities (from a Monte-Carlo-simulated experiment) and for Plexiglas (from a real laboratory experiment). The conclusion is that the buckling experiment is relatively easy for interpretation in the dimensionless buckling range which does not exceed 0.2. It corresponds, for example, to the geometric buckling B{sup 2}=1.1 cm{sup -2} for polyethylene of density 0.57 g cm{sup -3} or to B{sup 2}=3.0 cm{sup -2} for polyethylene of density 0.95 g cm{sup -3}.

  1. Gravitationally redshifted absorption lines in the X-ray burst spectra of a neutron star.

    Science.gov (United States)

    Cottam, J; Paerels, F; Mendez, M

    2002-11-07

    The fundamental properties of neutron stars provide a direct test of the equation of state of cold nuclear matter, a relationship between pressure and density that is determined by the physics of the strong interactions between the particles that constitute the star. The most straightforward method of determining these properties is by measuring the gravitational redshift of spectral lines produced in the neutron star photosphere. The equation of state implies a mass-radius relation, while a measurement of the gravitational redshift at the surface of a neutron star provides a direct constraint on the mass-to-radius ratio. Here we report the discovery of significant absorption lines in the spectra of 28 bursts of the low-mass X-ray binary EXO0748-676. We identify the most significant features with the Fe XXVI and XXV n = 2-3 and O VIII n = 1-2 transitions, all with a redshift of z = 0.35, identical within small uncertainties for the respective transitions. For an astrophysically plausible range of masses (M approximately 1.3-2.0 solar masses; refs 2-5), this value is completely consistent with models of neutron stars composed of normal nuclear matter, while it excludes some models in which the neutron stars are made of more exotic matter.

  2. The study of the thermal neutron flux in the deep underground laboratory DULB-4900

    Science.gov (United States)

    Alekseenko, V. V.; Gavrilyuk, Yu. M.; Gangapshev, A. M.; Gezhaev, A. M.; Dzhappuev, D. D.; Kazalov, V. V.; Kudzhaev, A. U.; Kuzminov, V. V.; Panasenko, S. I.; Ratkevich, S. S.; Tekueva, D. A.; Yakimenko, S. P.

    2017-01-01

    We report on the study of thermal neutron flux using monitors based on mixture of ZnS(Ag) and LiF enriched with a lithium-6 isotope at the deep underground laboratory DULB-4900 at the Baksan Neutrino Observatory. An annual modulation of thermal neutron flux in DULB-4900 is observed. Experimental evidences were obtained of correlation between the long-term thermal neutron flux variations and the absolute humidity of the air in laboratory. The amplitude of the modulation exceed 5% of total neutron flux.

  3. High efficiency event-counting thermal neutron imaging using Gd doped micro channel plate

    OpenAIRE

    Tian, Yang; Yang, Yigang; Pan, Jingsheng; Li, Yulan; Li, Yuanjing

    2013-01-01

    An event-counting thermal neutron imaging detector based on 3 mol % natGd2O3 doped micro channel plate (MCP) has been developed and tested. Thermal neutron imaging experiment was carried out with a low flux neutron beam. Detection efficiency of 33 % was achieved with only one doped MCP. The spatial resolution of 72 {\\mu}m RMS is currently limited by the readout anode. A detector with larger area and improved readout method is now being developed.

  4. A time-of-flight detector for thermal neutrons from radiotherapy Linacs

    Energy Technology Data Exchange (ETDEWEB)

    Conti, V. [Universita degli Studi di Milano and INFN di Milano (Italy)], E-mail: conti.Valentina@gmail.com; Bartesaghi, G. [Universita degli Studi di Milano and INFN di Milano (Italy); Bolognini, D.; Mascagna, V.; Perboni, C.; Prest, M.; Scazzi, S. [Universita dell' Insubria, Como and INFN di Milano (Italy); Mozzanica, A. [Universita degli Studi di Brescia and INFN sezione di Pavia (Italy); Cappelletti, P.; Frigerio, M.; Gelosa, S.; Monti, A.; Ostinelli, A. [Fisica Sanitaria, Ospedale S. Anna di Como (Italy); Giannini, G.; Vallazza, E. [INFN, sezione di Trieste and Universita degli Studi di Trieste (Italy)

    2007-10-21

    Boron Neutron Capture Therapy (BNCT) is a therapeutic technique exploiting the release of dose inside the tumour cell after a fission of a {sup 10}B nucleus following the capture of a thermal neutron. BNCT could be the treatment for extended tumors (liver, stomach, lung), radio-resistant ones (melanoma) or tumours surrounded by vital organs (brain). The application of BNCT requires a high thermal neutron flux (>5x10{sup 8}ncm{sup -2}s{sup -1}) with the correct energy spectrum (neutron energy <10keV), two requirements that for the moment are fulfilled only by nuclear reactors. The INFN PhoNeS (Photo Neutron Source) project is trying to produce such a neutron beam with standard radiotherapy Linacs, maximizing with a dedicated photo-neutron converter the neutrons produced by Giant Dipole Resonance by a high energy (>8MeV) photon beam. In this framework, we have developed a real-time detector to measure the thermal neutron time-of -flight to compute the flux and the energy spectrum. Given the pulsed nature of Linac beams, the detector is a single neutron counting system made of a scintillator detecting the photon emitted after the neutron capture by the hydrogen nuclei. The scintillator signal is sampled by a dedicated FPGA clock thus obtaining the exact arrival time of the neutron itself. The paper will present the detector and its electronics, the feasibility measurements with a Varian Clinac 1800/2100CD and comparison with a Monte Carlo simulation.

  5. Design of the thermal neutron detection system for CJPL-II

    Science.gov (United States)

    Zeng, Zhao-Ming; Gong, Hui; Li, Jian-Min; Yue, Qian; Zeng, Zhi; Cheng, Jian-Ping

    2017-05-01

    A low background thermal neutron flux detection system has been designed to measure the ambient thermal neutron flux of the second phase of the China Jinping Underground Laboratory (CJPL-II), right after completion of the rock bolting work. A 3He proportional counter tube combined with an identical 4He proportional counter tube was employed as the thermal neutron detector, which has been optimised in energy resolution, wall effect and radioactivity of construction materials for low background performance. The readout electronics were specially designed for long-term stable operation and easy maintenance in an underground laboratory under construction. The system was installed in Lab Hall No. 3 of CJPL-II and accumulated data for about 80 days. The ambient thermal neutron flux was determined under the assumption that the neutron field is fully thermalized, uniform and isotropic at the measurement position. Supported by National Natural Science Foundation of China (11475094)

  6. The CLYC-6 and CLYC-7 response to γ-rays, fast and thermal neutrons

    Science.gov (United States)

    Giaz, A.; Pellegri, L.; Camera, F.; Blasi, N.; Brambilla, S.; Ceruti, S.; Million, B.; Riboldi, S.; Cazzaniga, C.; Gorini, G.; Nocente, M.; Pietropaolo, A.; Pillon, M.; Rebai, M.; Tardocchi, M.

    2016-02-01

    The crystal Cs2LiYCl6:Ce (CLYC) is a very interesting scintillator material because of its good energy resolution and its capability to identify γ-rays and fast/thermal neutrons. The crystal Cs2LiYCl6:Ce contains 6Li and 35Cl isotopes, therefore, it is possible to detect thermal neutrons through the reaction 6Li(n, α)t while 35Cl ions allow to measure fast neutrons through the reactions 35Cl(n, p)35S and 35Cl(n, α)32P. In this work two CLYC 1″×1″ crystals were used: the first crystal, enriched with 6Li at 95% (CLYC-6) is ideal for thermal neutron measurements while the second one, enriched with 7Li at >99% (CLYC-7) is suitable for fast neutron measurements. The response of CLYC scintillators was measured with different PMT models: timing or spectroscopic, with borosilicate glass or quartz window. The energy resolution, the neutron-γ discrimination and the internal activity are discussed. The capability of CLYC scintillators to discriminate γ rays from neutrons was tested with both thermal and fast neutrons. The thermal neutrons were measured with both detectors, using an AmBe source. The measurements of fast neutrons were performed at the Frascati Neutron Generator facility (Italy) where a deuterium beam was accelerated on a deuterium or on a tritium target, providing neutrons of 2.5 MeV or 14.1 MeV, respectively. The different sensitivity to thermal and fast neutrons of a CLYC-6 and of a CLYC-7 was additionally studied.

  7. Coupled neutronics - thermal-hydraulics programs for SCWRS

    Energy Technology Data Exchange (ETDEWEB)

    Reiss, T. [Institute of Nuclear Techniques, Budapest University of Technology and Economics, Muegyetem rkp. 9., 1111 Budapest (Hungary)

    2010-07-01

    The Supercritical Water Cooled Reactor (SCWR) was chosen as one of the Generation IV reactors by GIF. At the moment, a number of concepts - thermal as well as fast ones - exist. The reference parameters for a thermal SCWR have been taken from the European High Performance Light Water Reactor (HPLWR). Since the pressure is higher than the critical pressure (22.1 MPa) there is no change in the phase of the water in the core. On the other hand, due to the significant changes in the physical properties of water at supercritical pressure, the system is susceptible to local temperature, density and power oscillations. This inclination is increased by the pseudo-critical transformation of the water used as coolant. Thus, for modelling a system of this type coupled neutronics - thermal-hydraulics programs are required. Such a program system has been developed with the following main features: great modularity which allows for easy modifications, thus several SCWR concepts can be studied; detailed assembly calculations (with MCNP) and full-core analysis (with SCALE) are supported; the differential equations of xenon poisoning are implemented to study xenon oscillations. The program system was used to examine the assembly of the HPLWR, to design the assembly and the core of the Simplified Supercritical Water Cooled Reactor (SSCWR) and to model xenon oscillations in SCWRs. (authors)

  8. The fluctuating ribosome: thermal molecular dynamics characterized by neutron scattering

    Science.gov (United States)

    Zaccai, Giuseppe; Natali, Francesca; Peters, Judith; Řihová, Martina; Zimmerman, Ella; Ollivier, J.; Combet, J.; Maurel, Marie-Christine; Bashan, Anat; Yonath, Ada

    2016-11-01

    Conformational changes associated with ribosome function have been identified by X-ray crystallography and cryo-electron microscopy. These methods, however, inform poorly on timescales. Neutron scattering is well adapted for direct measurements of thermal molecular dynamics, the ‘lubricant’ for the conformational fluctuations required for biological activity. The method was applied to compare water dynamics and conformational fluctuations in the 30 S and 50 S ribosomal subunits from Haloarcula marismortui, under high salt, stable conditions. Similar free and hydration water diffusion parameters are found for both subunits. With respect to the 50 S subunit, the 30 S is characterized by a softer force constant and larger mean square displacements (MSD), which would facilitate conformational adjustments required for messenger and transfer RNA binding. It has been shown previously that systems from mesophiles and extremophiles are adapted to have similar MSD under their respective physiological conditions. This suggests that the results presented are not specific to halophiles in high salt but a general property of ribosome dynamics under corresponding, active conditions. The current study opens new perspectives for neutron scattering characterization of component functional molecular dynamics within the ribosome.

  9. IMPROVED COMPUTATIONAL CHARACTERIZATION OF THE THERMAL NEUTRON SOURCE FOR NEUTRON CAPTURE THERAPY RESEARCH AT THE UNIVERSITY OF MISSOURI

    Energy Technology Data Exchange (ETDEWEB)

    Stuart R. Slattery; David W. Nigg; John D. Brockman; M. Frederick Hawthorne

    2010-05-01

    Parameter studies, design calculations and initial neutronic performance measurements have been completed for a new thermal neutron beamline to be used for neutron capture therapy cell and small-animal radiobiology studies at the University of Missouri Research Reactor. The beamline features the use of single-crystal silicon and bismuth sections for neutron filtering and for reduction of incident gamma radiation. The computational models used for the final beam design and performance evaluation are based on coupled discrete-ordinates and Monte Carlo techniques that permit detailed modeling of the neutron transmission properties of the filtering crystals with very few approximations. This is essential for detailed dosimetric studies required for the anticipated research program.

  10. Fully self-consistent thermal evolution studies of rotating neutron stars

    Science.gov (United States)

    Negreiros, Rodrigo; Schramm, Stefan; Weber, Fridolin

    2017-07-01

    In this work we study the thermal evolution of rotating, axis-symmetric neutron stars, which are subjected to structural and compositional changes during spin-down. Our aim is to go beyond standard thermal evolution calculations where neutron stars are considered spherically-symmetric and with a static, "frozen-in" composition. Building on previous work, we carry out fully self-consistent thermal evolution calculations where the neutron star has an axis-symmetric, time-dependent structure. Such an approach allows us to consider, during the thermal evolution, changes of the star's geometry as well as its microscopic particle population. As a proof-of-concept, we study the thermal evolution of a neutron star subjected to magnetic braking spin-down. We show that the spin-evolution, combined with the accompanying structural and compositional changes lead to a substantially distinct thermal evolution scenario.

  11. Improved thermal neutron activation sensor for detection of bulk explosives

    Science.gov (United States)

    McFee, John E.; Faust, Anthony A.; Andrews, H. Robert; Clifford, Edward T. H.; Mosquera, Cristian M.

    2012-06-01

    Defence R&D Canada - Suffield and Bubble Technology Industries have been developing thermal neutron activation (TNA) sensors for detection of buried bulk explosives since 1994. First generation sensors, employing an isotopic source and NaI(Tl) gamma ray detectors, were deployed by Canadian Forces in 2002 as confirmation sensors on the ILDS teleoperated, vehicle-mounted, multi-sensor anti-tank landmine detection systems. The first generation TNA could detect anti-tank mines buried 10 cm or less in no more than a minute, but deeper mines and those significantly displaced horizontally required considerably longer times. Mines as deep as 30 cm could be detected with long counting times (1000 s). The second generation TNA detector is being developed with a number of improvements aimed at increasing sensitivity and facilitating ease of operation. Among these are an electronic neutron generator to increase sensitivity for deeper and horizontally displaced explosives; LaBr3(Ce) scintillators, to improve time response and energy resolution; improved thermal and electronic stability; improved sensor head geometry to minimize spatial response nonuniformity; and more robust data processing. This improved sensitivity can translate to either decreased counting times, decreased minimum detectable explosive quantities, increased maximum sensor-to-target displacement, or a trade off among all three. Experiments to characterize the performance of the latest generation TNA in detecting buried landmines and IEDs hidden in culverts were conducted during 2011. This paper describes the second generation system. The experimental setup and methodology are detailed and preliminary comparisons between the performance of first and second generation systems are presented.

  12. Dependence of the thermal neutron fluence at the size installations radiotherapy bunker; Dependencia de la fluencia termica de neutrones en el tamano del bunquer en instalaciones de radioterapia

    Energy Technology Data Exchange (ETDEWEB)

    Gonzalez-Soto, X.; Amgarou, K.; Langares, J. L.; Exposito, M. R.; Gomez, F.; Domingo, C.; Sanchez-Doblado, F.

    2011-07-01

    The project aims to infer the dose deposited by neutrons in the patient treated by radiation therapy, from a measurement of the thermal neutron fluence at a selected point within the treatment room. These thermal neutrons are created when fast neutrons produced in the linac head are moderate, mainly in the walls of the bunker, and its yield depends on both the volume of the room and its geometry.

  13. Determination of thermal neutrons diffusion length in graphite; Determinacion de la Longitud de Difusion de los Neutrones Termicos en Grafito

    Energy Technology Data Exchange (ETDEWEB)

    Garcia Fite, J.

    1959-07-01

    The diffusion length of thermal neutrons in graphite using the less possible quantity of material has been determined. The proceeding used was the measurement in a graphite pile which has a punctual source of rapid neutrons inside surrounded by a reflector medium (paraffin or water). The measurement was done in the following conditions: a) introducing an aluminium plate between both materials. b) Introducing a cadmium plate between both materials. (Author) 91 refs.

  14. Neutron activation analysis and atomic absorption spectrophotometry for the analysis of fresh, pasteurised and powder milk

    Energy Technology Data Exchange (ETDEWEB)

    Wasim, M.; Rehman, S.; Arif, M.; Fatima, I.; Zaidi, J.H. [Pakistan Inst. of Nuclear Science and Technology, Islamabad (Pakistan). Chemistry Div.

    2012-07-01

    This study shows the application of semi-absolute k{sub 0} instrumental neutron activation analysis (k{sub 0}-INAA), epithermal neutron activation analysis (ENAA) and atomic absorption spectrophotometry (AAS) for the determination of 21 elements (Br, Ca, Cl, Co, Cr, Cs, Cu, Fe, Hf, I, K, Mg, Mn, Na, Ni, P, Pb, Rb, Sc Sr, and Zn) in different types of milk samples. The ENAA was required for the determination of iodine, AAS for Cu, Ni and Pb and the rest of the elements were measured by k{sub 0}-INAA. Thirteen elements (Br, Ca, Cl, Cs, Cu, Fe, K, Mg, Na, P, Rb, Sr and Zn) were identified in all milk samples. Ni was detected in eleven and Pb in two samples. Concentrations of most of the elements were within the ranges of the world reported data. The data was further explored by principal component analysis to find relationships between samples and elements. (orig.)

  15. Thermal neutron imaging through XRQA2 GAFCHROMIC films coupled with a cadmium radiator

    Energy Technology Data Exchange (ETDEWEB)

    Sacco, D. [INFN – LNF, Via E. Fermi n.40, Frascati, 00044 Roma (Italy); INAIL – DIT, Via di Fontana Candida n.1, 00040 Monteporzio Catone (Italy); Bedogni, R., E-mail: roberto.bedogni@lnf.infn.it [INFN – LNF, Via E. Fermi n.40, Frascati, 00044 Roma (Italy); Bortot, D. [Politecnico di Milano, Dipartimento di Energia, Via La Masa 34, 20156 Milano (Italy); INFN – Milano, Via Celoria16, 20133 Milano (Italy); Palomba, M. [ENEA Casaccia, Via Anguillarese, 301, S. Maria di Galeria, 00123 Roma (Italy); Pola, A. [Politecnico di Milano, Dipartimento di Energia, Via La Masa 34, 20156 Milano (Italy); INFN – Milano, Via Celoria16, 20133 Milano (Italy); Introini, M.V.; Lorenzoli, M. [Politecnico di Milano, Dipartimento di Energia, Via La Masa 34, 20156 Milano (Italy); Gentile, A. [INFN – LNF, Via E. Fermi n.40, Frascati, 00044 Roma (Italy); Strigari, L. [Laboratory of Medical Physics, Regina Elena National Cancer Institute, Via E. Chianesi 53, 00144 Roma (Italy); Pressello, C. [Department of Medical Physics, Azienda Ospedaliera San Camillo Forlanini, Circonvallazione Gianicolense 87, 00152 Roma (Italy); Soriani, A. [Laboratory of Medical Physics, Regina Elena National Cancer Institute, Via E. Chianesi 53, 00144 Roma (Italy); Gómez-Ros, J.M. [INFN – LNF, Via E. Fermi n.40, Frascati, 00044 Roma (Italy); CIEMAT, Av. Complutense 40, 28040 Madrid (Spain)

    2015-10-21

    A simple and inexpensive method to perform passive thermal neutron imaging on large areas was developed on the basis of XRQA2 GAFCHROMIC films, commonly employed for quality assurance in radiology. To enhance their thermal neutron response, the sensitive face of film was coupled with a 1 mm thick cadmium radiator, forming a sandwich. By exchanging the order of Cd filter and sensitive film with respect to the incident neutron beam direction, two different configurations (beam-Cd-film and beam-film-Cd) were identified. These configurations were tested at thermal neutrons fluence values in the range 10{sup 9}–10{sup 10} cm{sup −2}, using the ex-core radial thermal neutron column of the ENEA Casaccia – TRIGA reactor. The results are presented in this work.

  16. Monte Carlo simulation of thermal neutron flux of americium-beryllium source used in neutron activation analysis

    Science.gov (United States)

    Didi, Abdessamad; Dadouch, Ahmed; Bencheikh, Mohamed; Jai, Otman

    2017-09-01

    The neutron activation analysis is a method of exclusively elemental analysis. Its implementation of irradiates the sample which can be analyzed by a high neutron flux, this method is widely used in developed countries with nuclear reactors or accelerators of particle. The purpose of this study is to develop a prototype to increase the neutron flux such as americium-beryllium and have the opportunity to produce radioisotopes. Americium-beryllium is a mobile source of neutron activity of 20 curie, and gives a thermal neutron flux of (1.8 ± 0.0007) × 106 n/cm2 s when using water as moderator, when using the paraffin, the thermal neutron flux increases to (2.2 ± 0.0008) × 106 n/cm2 s, in the case of adding two solid beryllium barriers, the distance between them is 24 cm, parallel and symmetrical about the source, the thermal flux is increased to (2.5 ± 0.0008) × 106 n/cm2 s and in the case of multi-source (6 sources), with-out barriers, increases to (1.17 ± 0.0008) × 107 n/cm2 s with a rate of increase equal to 4.3 and with the both barriers flux increased to (1.37 ± 0.0008) × 107 n/cm2 s.

  17. Thermally induced nonlinear optical absorption in metamaterial perfect absorbers

    Energy Technology Data Exchange (ETDEWEB)

    Guddala, Sriram, E-mail: sguddala@iitk.ac.in; Kumar, Raghwendra; Ramakrishna, S. Anantha [Department of Physics, Indian Institute of Technology Kanpur, Kanpur 208016 (India)

    2015-03-16

    A metamaterial perfect absorber consisting of a tri-layer (Al/ZnS/Al) metal-dielectric-metal system with top aluminium nano-disks was fabricated by laser-interference lithography and lift-off processing. The metamaterial absorber had peak resonant absorbance at 1090 nm and showed nonlinear absorption for 600ps laser pulses at 1064 nm wavelength. A nonlinear saturation of reflectance was measured to be dependent on the average laser power incident and not the peak laser intensity. The nonlinear behaviour is shown to arise from the heating due to the absorbed radiation and photo-thermal changes in the dielectric properties of aluminium. The metamaterial absorber is seen to be damage resistant at large laser intensities of 25 MW/cm{sup 2}.

  18. Neutron Absorption Measurements Constrain Eucrite-Diogenite Mixing in Vesta's Regolith

    Science.gov (United States)

    Prettyman, T. H.; Mittlefehldt, D. W.; Feldman, W. C.; Hendricks, J. S.; Lawrence, D. J.; Peplowski, P. N.; Toplis, M. J.; Yamashita, N.; Beck, A.; LeCorre, L.; hide

    2013-01-01

    The NASA Dawn Mission s Gamma Ray and Neutron Detector (GRaND) [1] acquired mapping data during 5 months in a polar, low altitude mapping orbit (LAMO) with approx.460-km mean radius around main-belt asteroid Vesta (264-km mean radius) [2]. Neutrons and gamma rays are produced by galactic cosmic ray interactions and by the decay of natural radioelements (K, Th, U), providing information about the elemental composition of Vesta s regolith to depths of a few decimeters beneath the surface. From the data acquired in LAMO, maps of vestan neutron and gamma ray signatures were determined with a spatial resolution of approx.300 km full-width-at-half-maximum (FWHM), comparable in scale to the Rheasilvia impact basin (approx.500 km diameter). The data from Vesta encounter are available from the NASA Planetary Data System. Based on an analysis of gamma-ray spectra, Vesta s global-average regolith composition was found to be consistent with the Howardite, Eucrite, and Diogenite (HED) meteorites, reinforcing the HED-Vesta connection [2-7]. Further, an analysis of epithermal neutrons revealed variations in the abundance of hydrogen on Vesta s surface, reaching values up to 400 micro-g/g [2]. The association of high concentrations of hydrogen with equatorial, low-albedo surface regions indicated exogenic delivery of hydrogen by the infall of carbonaceous chondrite (CC) materials. This finding was buttressed by the presence of minimally-altered CC clasts in howardites, with inferred bulk hydrogen abundances similar to that found by GRaND, and by studies using data from Dawn s Framing Camera (FC) and VIR instruments [8-10]. In addition, from an analysis of neutron absorption, spatial-variations in the abundance of elements other than hydrogen were detected [2].

  19. Cascade γ rays following capture of thermal neutrons on 113Cd

    Science.gov (United States)

    Rusev, G.; Jandel, M.; Krtička, M.; Arnold, C. W.; Bredeweg, T. A.; Couture, A.; Moody, W. A.; Mosby, S. M.; Ullmann, J. L.

    2013-11-01

    Intensity distributions of cascade γ-ray transitions following the capture of thermal neutrons by 113Cd have been measured at the Los Alamos Neutron Science Center for various γ-ray multiplicities. The experiment was carried out at the highly segmented 4π γ-ray calorimeter—Detector for Advanced Neutron Capture Experiments (DANCE). A measured two-dimensional spectrum of counts versus γ-ray energy versus γ-ray multiplicity, from the strongest resonance in the 113Cd(n,γ) reaction at 0.178 eV has been compared to predictions from the statistical model. The best representation of the γ-ray cascades following the capture of thermal neutrons on 113Cd is presented. The intensity distribution of these cascades is of great importance for estimates of response to thermal neutrons of devices that use natural or enriched cadmium.

  20. Thermal states of neutron stars with a consistent model of interior

    Science.gov (United States)

    Fortin, M.; Taranto, G.; Burgio, G. F.; Haensel, P.; Schulze, H.-J.; Zdunik, J. L.

    2018-01-01

    We model the thermal states of both isolated neutron stars and accreting neutron stars in X-ray transients in quiescence and confront them with observations. We use an equation of state calculated using realistic two-body and three-body nucleon interactions, and superfluid nucleon gaps obtained using the same microscopic approach in the BCS approximation. Consistency with low-luminous accreting neutron stars is obtained, as the direct Urca process is operating in neutron stars with mass larger than 1.1M⊙ for the employed equation of state. In addition, proton superfluidity and sufficiently weak neutron superfluidity, obtained using a scaling factor for the gaps, are necessary to explain the cooling of middle-aged neutron stars and to obtain a realistic distribution of neutron star masses.

  1. Identification of the fast and thermal neutron characteristics of transuranic waste drums

    Energy Technology Data Exchange (ETDEWEB)

    Storm, B.H. Jr.; Bramblett, R.L. [Lockheed Martin Specialty Components, Largo, FL (United States); Hensley, C. [Oak Ridge National Lab., TN (United States)

    1997-11-01

    Fissile and spontaneously fissioning material in transuranic waste drums can be most sensitively assayed using an active and passive neutron assay system such as the Active Passive Neutron Examination and Assay. Both the active and the passive assays are distorted by the presence of the waste matrix and containerization. For accurate assaying, this distortion must be characterized and accounted for. An External Matrix Probe technique has been developed that accomplishes this task. Correlations between in-drum neutron flux measurements and monitors in the Active Passive Neutron Examination and Assay chamber with various matrix materials provide a non-invasive means of predicting the thermal neutron flux in waste drums. Similarly, measures of the transmission of fast neutrons emitted from sources in the drum. Results obtained using the Lockheed Martin Specialty Components Active Passive Neutron Examination and Assay system are discussed. 12 figs., 1 tab.

  2. Simultaneous measurement of fission fragments and prompt neutrons for thermal neutron-induced fission of U-235

    Energy Technology Data Exchange (ETDEWEB)

    Nishio, Katsuhisa; Yamamoto, Hideki; Kimura, Itsuro; Nakagome, Yoshihiro [Kyoto Univ. (Japan)

    1997-03-01

    Simultaneous measurement of fission fragments and prompt neutrons following the thermal neutron induced fission of U-235 has been performed in order to obtain the neutron multiplicity (v) and its emission energy ({eta}) against the specified mass (m{sup *}) and the total kinetic energy (TKE). The obtained value of -dv/dTKE(m{sup *}) showed a saw-tooth distribution. The average neutron energy <{eta}>(m{sup *}) had a distribution with a reflection symmetry around the half mass division. The measurement also gave the level density parameters of the specified fragment, a(m{sup *}), and this parameters showed a saw-tooth trend too. The analysis by a phenomenological description of this parameters including the shell and collective effects suggested the existence of a collective motion of the fission fragments. (author)

  3. Evaluating the 239Pu Prompt Fission Neutron Spectrum Induced by Thermal to 30 MeV Neutrons

    Directory of Open Access Journals (Sweden)

    Neudecker D.

    2016-01-01

    Full Text Available We present a new evaluation of the 239Pu prompt fission neutron spectrum (PFNS induced by thermal to 30 MeV neutrons. Compared to the ENDF/B-VII.1 evaluation, this one includes recently published experimental data as well as an improved and extended model description to predict PFNS. For instance, the pre-equilibrium neutron emission component to the PFNS is considered and the incident energy dependence of model parameters is parametrized more realistically. Experimental and model parameter uncertainties and covariances are estimated in detail. Also, evaluated covariances are provided between all PFNS at different incident neutron energies. Selected evaluation results and first benchmark calculations using this evaluation are briefly discussed.

  4. Limits on thermal variations in a dozen quiescent neutron stars over a decade

    NARCIS (Netherlands)

    Bahramian, A.; Heinke, C.O.; Degenaar, N.; Chomiuk, L.; Wijnands, R.; Strader, J.; Ho, W.C.G.; Pooley, D.

    2015-01-01

    n quiescent low-mass X-ray binaries (qLMXBs) containing neutron stars, the origin of the thermal X-ray component may be either release of heat from the core of the neutron star, or continuing low-level accretion. In general, heat from the core should be stable on time-scales <104 yr, while

  5. Neutron spectroscopy by thermalization light yield measurement in a composite heterogeneous scintillator

    Energy Technology Data Exchange (ETDEWEB)

    Shi, T.; Nattress, J.; Mayer, Michael F.; Lin, M-W; Jovanovic, Igor

    2016-12-11

    An exothermic neutron capture reaction can be used to uniquely identify neutrons in particle detectors. With the use of a capture-gated coincidence technique, the sequence of scatter events that lead to neutron thermalization prior to the neutron capture can also be used to measure neutron energy. We report on the measurement of thermalization light yield via a time-of-flight technique in a polyvinyl toluene-based scintillator EJ-290 within a heterogeneous composite detector that also includes 6Li-doped glass scintillator. The thermalization light output exhibits a strong correlation with neutron energy because of the preference for near-complete energy deposition prior to the 6Li(n,t)4He neutron capture reaction. The nonproportionality of the light yield from nuclear recoils contributes to the observed broadening of the distribution of thermalization light output. The nonproportional dependence of the scintillation light output in the EJ-290 scintillator as a function of proton recoil energy has been characterized in the range of 0.3–14.1 MeV via the Birks parametrization through a combination of time-of-flight measurement and previously conducted measurements with Monoenergetic neutron sources.

  6. Neutron spectroscopy by thermalization light yield measurement in a composite heterogeneous scintillator

    Energy Technology Data Exchange (ETDEWEB)

    Shi, T., E-mail: tan.shi0122@gmail.com [Department of Mechanical and Nuclear Engineering, Pennsylvania State University, University Park, PA 16802 (United States); Nattress, J. [Department of Nuclear Engineering and Radiological Sciences, University of Michigan, Ann Arbor, MI 48109 (United States); Mayer, M. [Department of Mechanical and Nuclear Engineering, Pennsylvania State University, University Park, PA 16802 (United States); Pacific Northwest National Laboratory, Richland, WA 99354 (United States); Lin, M.-W. [Department of Mechanical and Nuclear Engineering, Pennsylvania State University, University Park, PA 16802 (United States); Jovanovic, I. [Department of Mechanical and Nuclear Engineering, Pennsylvania State University, University Park, PA 16802 (United States); Department of Nuclear Engineering and Radiological Sciences, University of Michigan, Ann Arbor, MI 48109 (United States)

    2016-12-11

    An exothermic neutron capture reaction can be used to uniquely identify neutrons in particle detectors. With the use of a capture-gated coincidence technique, the sequence of scatter events that lead to neutron thermalization prior to the neutron capture can also be used to measure neutron energy. We report on the measurement of thermalization light yield via a time-of-flight technique in a polyvinyl toluene-based scintillator EJ-290 within a heterogeneous composite detector that also includes {sup 6}Li-doped glass scintillator. The thermalization light output exhibits a strong correlation with neutron energy because of the preference for near-complete energy deposition prior to the {sup 6}Li(n,t){sup 4}He neutron capture reaction. The nonproportionality of the light yield from nuclear recoils contributes to the observed broadening of the distribution of thermalization light output. The nonproportional dependence of the scintillation light output in the EJ-290 scintillator as a function of proton recoil energy has been characterized in the range of 0.3–14.1 MeV via the Birks parametrization through a combination of time-of-flight measurement and previously conducted measurements with monoenergetic neutron sources.

  7. Neutron spectroscopy by thermalization light yield measurement in a composite heterogeneous scintillator

    Science.gov (United States)

    Shi, T.; Nattress, J.; Mayer, M.; Lin, M.-W.; Jovanovic, I.

    2016-12-01

    An exothermic neutron capture reaction can be used to uniquely identify neutrons in particle detectors. With the use of a capture-gated coincidence technique, the sequence of scatter events that lead to neutron thermalization prior to the neutron capture can also be used to measure neutron energy. We report on the measurement of thermalization light yield via a time-of-flight technique in a polyvinyl toluene-based scintillator EJ-290 within a heterogeneous composite detector that also includes 6Li-doped glass scintillator. The thermalization light output exhibits a strong correlation with neutron energy because of the preference for near-complete energy deposition prior to the 6Li(n,t)4He neutron capture reaction. The nonproportionality of the light yield from nuclear recoils contributes to the observed broadening of the distribution of thermalization light output. The nonproportional dependence of the scintillation light output in the EJ-290 scintillator as a function of proton recoil energy has been characterized in the range of 0.3-14.1 MeV via the Birks parametrization through a combination of time-of-flight measurement and previously conducted measurements with monoenergetic neutron sources.

  8. Neutronic and thermal-hydraulic coupling for 3D reactor core modeling combining MCB and fluent

    Directory of Open Access Journals (Sweden)

    Królikowski Igor P.

    2015-09-01

    Full Text Available Three-dimensional simulations of neutronics and thermal hydraulics of nuclear reactors are a tool used to design nuclear reactors. The coupling of MCB and FLUENT is presented, MCB allows to simulate neutronics, whereas FLUENT is computational fluid dynamics (CFD code. The main purpose of the coupling is to exchange data such as temperature and power profile between both codes. Temperature required as an input parameter for neutronics is significant since cross sections of nuclear reactions depend on temperature. Temperature may be calculated in thermal hydraulics, but this analysis needs as an input the power profile, which is a result from neutronic simulations. Exchange of data between both analyses is required to solve this problem. The coupling is a better solution compared to the assumption of estimated values of the temperatures or the power profiles; therefore the coupled analysis was created. This analysis includes single transient neutronic simulation and several steady-state thermal simulations. The power profile is generated in defined points in time during the neutronic simulation for the thermal analysis to calculate temperature. The coupled simulation gives information about thermal behavior of the reactor, nuclear reactions in the core, and the fuel evolution in time. Results show that there is strong influence of neutronics on thermal hydraulics. This impact is stronger than the impact of thermal hydraulics on neutronics. Influence of the coupling on temperature and neutron multiplication factor is presented. The analysis has been performed for the ELECTRA reactor, which is lead-cooled fast reactor concept, where the coolant fl ow is generated only by natural convection

  9. Neutron Capture by Cadmium: Thermal Cross Sections and Resonance Integrals of ^106,108,110,112,114,116Cd

    Science.gov (United States)

    Gicking, Allison M.; Krane, Kenneth S.

    2011-10-01

    The neutron capture cross sections of the stable, even-mass Cd isotopes (A = 106, 108, 110, 112, 114, and 116) have been previously measured in sources of natural abundance or low enrichment, often making the results uncertain owing to the large absorption cross section of naturally occurring ^113Cd. Ambiguities in values of the isomeric branching ratios have also contributed to uncertainties in previous results. We have remeasured the Cd neutron capture cross sections using samples of greater than 90% isotopic enrichment irradiated in the OSU TRIGA reactor. Gamma-ray emission spectra were analyzed to determine the effective resonance integrals and thermal cross sections leading to eight radioactive ground and isomeric states in the Cd isotopes.

  10. Search for sp-interference effect in emission of prompt neutrons of sup 2 sup 3 sup 5 U fission by thermal polarized neutrons

    CERN Document Server

    Danilyan, G V; Pavlov, V S; Fedorov, A V

    2001-01-01

    The results of the experiment for the search of the sp-interference effect in the distribution of the prompt neutrons of the sup 2 sup 3 sup 5 U fission by thermal polarized neutrons are presented. The experiment is carried out on the polarized neutrons beam of the MIFI reactor. The scheme of the installation and the flight time spectrum are presented

  11. Feasibility of fiber-optic radiation sensor using Cerenkov effect for detecting thermal neutrons.

    Science.gov (United States)

    Jang, Kyoung Won; Yagi, Takahiro; Pyeon, Cheol Ho; Yoo, Wook Jae; Shin, Sang Hun; Misawa, Tsuyoshi; Lee, Bongsoo

    2013-06-17

    In this research, we propose a novel method for detecting thermal neutrons with a fiber-optic radiation sensor using the Cerenkov effect. We fabricate a fiber-optic radiation sensor that detects thermal neutrons with a Gd-foil, a rutile crystal, and a plastic optical fiber. The relationship between the fluxes of electrons inducing Cerenkov radiation in the sensor probe of the fiber-optic radiation sensor and thermal neutron fluxes is determined using the Monte Carlo N-particle transport code simulations. To evaluate the fiber-optic radiation sensor, the Cerenkov radiation generated in the fiber-optic radiation sensor by irradiation of pure thermal neutron beams is measured according to the depths of polyethylene.

  12. Impact of thermal and intermediate energy neutrons on the semiconductor memories for the CERN accelerators

    CERN Document Server

    Cecchetto, Matteo; Gerardin, Simone

    A wide quantity of SRAM memories are employed along the Large Hadron Collider (LHC), the main CERN accelerator, and they are subjected to high levels of ionizing radiations which compromise the reliability of these devices. The Single Event Effect (SEE) qualification for components to be used in the complex high-energy accelerator at CERN relies on the characterization of two cross sections: 200-MeV protons and thermal neutrons. However, due to cost and time constraints, it is not always possible to characterize the SEE response of components to thermal neutrons, which is often regarded as negligible for components without borophosphosilicate glass (BPSG). Nevertheless, as recent studies show, the sensitivity of deep sub-micron technologies to thermal neutrons has increased owing to the presence of Boron 10 as a dopant and contact contaminant. The very large thermal neutron fluxes relative to high-energy hadron fluxes in some of the heavily shielded accelerator areas imply that even comparatively small therm...

  13. Design of 6 Mev linear accelerator based pulsed thermal neutron source: FLUKA simulation and experiment

    Energy Technology Data Exchange (ETDEWEB)

    Patil, B.J., E-mail: bjp@physics.unipune.ac.in [Department of Physics, University of Pune, Pune 411 007 (India); Chavan, S.T.; Pethe, S.N.; Krishnan, R. [SAMEER, IIT Powai Campus, Mumbai 400 076 (India); Bhoraskar, V.N. [Department of Physics, University of Pune, Pune 411 007 (India); Dhole, S.D., E-mail: sanjay@physics.unipune.ac.in [Department of Physics, University of Pune, Pune 411 007 (India)

    2012-01-15

    The 6 MeV LINAC based pulsed thermal neutron source has been designed for bulk materials analysis. The design was optimized by varying different parameters of the target and materials for each region using FLUKA code. The optimized design of thermal neutron source gives flux of 3 Multiplication-Sign 10{sup 6}ncm{sup -2}s{sup -1} with more than 80% of thermal neutrons and neutron to gamma ratio was 1 Multiplication-Sign 10{sup 4}ncm{sup -2}mR{sup -1}. The results of prototype experiment and simulation are found to be in good agreement with each other. - Highlights: Black-Right-Pointing-Pointer The optimized 6 eV linear accelerator based thermal neutron source using FLUKA simulation. Black-Right-Pointing-Pointer Beryllium as a photonuclear target and reflector, polyethylene as a filter and shield, graphite as a moderator. Black-Right-Pointing-Pointer Optimized pulsed thermal neutron source gives neutron flux of 3 Multiplication-Sign 10{sup 6} n cm{sup -2} s{sup -1}. Black-Right-Pointing-Pointer Results of the prototype experiment were compared with simulations and are found to be in good agreement. Black-Right-Pointing-Pointer This source can effectively be used for the study of bulk material analysis and activation products.

  14. Tables for simplifying calculations of activities produced by thermal neutrons

    Science.gov (United States)

    Senftle, F.E.; Champion, W.R.

    1954-01-01

    The method of calculation described is useful for the types of work of which examples are given. It is also useful in making rapid comparison of the activities that might be expected from several different elements. For instance, suppose it is desired to know which of the three elements, cobalt, nickel, or vanadium is, under similar conditions, activated to the greatest extent by thermal neutrons. If reference is made to a cross-section table only, the values may be misleading unless properly interpreted by a suitable comparison of half-lives and abundances. In this table all the variables have been combined and the desired information can be obtained directly from the values of A 3??, the activity produced per gram per second of irradiation, under the stated conditions. Hence, it is easily seen that, under similar circumstances of irradiation, vanadium is most easily activated even though the cross section of one of the cobalt isotopes is nearly five times that of vanadium and the cross section of one of the nickel isotopes is three times that of vanadium. ?? 1954 Societa?? Italiana di Fisica.

  15. Feasibility of culvert IED detection using thermal neutron activation

    Science.gov (United States)

    Faust, Anthony A.; McFee, John E.; Clifford, Edward T. H.; Andrews, Hugh Robert; Mosquera, Cristian; Roberts, William C.

    2012-06-01

    Bulk explosives hidden in culverts pose a serious threat to the Canadian and allied armies. Culverts provide an opportunity to conceal insurgent activity, avoid the need for detectable surface disturbances, and limit the applicability of conventional sub-surface sensing techniques. Further, in spite of the large masses of explosives that can be employed, the large sensor{target separation makes detection of the bulk explosive content challeng- ing. Defence R&D Canada { Sueld and Bubble Technology Industries have been developing thermal neutron activation (TNA) sensors for detection of buried bulk explosives for over 15 years. The next generation TNA sensor, known as TNA2, incorporates a number of improvements that allow for increased sensor-to-target dis- tances, making it potentially feasible to detect large improvised explosive devices (IEDs) in culverts using TNA. Experiments to determine the ability of TNA2 to detect improvised explosive devices in culverts are described, and the resulting signal levels observed for relevant quantities of explosives are presented. Observations conrm that bulk explosives detection using TNA against a culvert-IED is possible, with large charges posing a detection challenge at least as dicult as that of a deeply buried anti-tank landmine. Because of the prototype nature of the TNA sensor used, it is not yet possible to make denitive statements about the absolute sensitivity or detection time. Further investigation is warranted.

  16. Transport calculation of thermal and cold neutrons using NMTC/JAERI-MCNP4A code system

    Energy Technology Data Exchange (ETDEWEB)

    Iga, Kiminori [Kyushu Univ., Fukuoka (Japan); Takada, Hiroshi; Nagao, Tadashi

    1998-01-01

    In order to investigate the applicability of the NMTC/JAERI-MCNP4A code system to the neutronics design study in the neutron science research project of JAERI, transport calculations of thermal and cold neutrons are performed with the code system on a spallation neutron source composed of light water cooled tantalum target with a moderator and a reflector system. The following neutronic characteristics are studied in the calculation : the variation of the intensity of neutrons emitted from a light water moderator or a liquid hydrogen with/without the B{sub 4}C decoupler, which are installed to produce sharp pulse, and that dependent on the position of external source neutrons in the tantalum target. The calculated neutron energy spectra are reproduced well by the semi-empirical formula with the parameter values reliable in physical meanings. It is found to be necessary to employ proper importance sampling technique in the statistics. It is confirmed from this work that the NMTC/JAERI-MCNP4A code system is applicable to the neutronics design study of spallation neutron sources proposed for the neutron science research project. (author)

  17. "m=1" coatings for neutron guides

    DEFF Research Database (Denmark)

    Cooper-Jensen, C.P.; Vorobiev, A.; Klinkby, Esben Bryndt

    2014-01-01

    the critical angle of Ni is needed one has used Ni58 or Ni/Ti multilayer coatings. Ni has one of the highest neutron scattering density but it also has a fairly high absorption cross section for cold and thermal neutrons and when a neutron is absorbed it emits a lot of gamma rays, some with energies above 9 MeV...

  18. Thermal Analysis of a Solar Powered Absorption Cooling System with Fully Mixed Thermal Storage at Startup

    Directory of Open Access Journals (Sweden)

    Camelia Stanciu

    2017-01-01

    Full Text Available A simple effect one stage ammonia-water absorption cooling system fueled by solar energy is analyzed. The considered system is composed by a parabolic trough collector concentrating solar energy into a tubular receiver for heating water. This is stored in a fully mixed thermal storage tank and used in the vapor generator of the absorption cooling system. Time dependent cooling load is considered for the air conditioning of a residential two-storey house. A parametric study is performed to analyze the operation stability of the cooling system with respect to solar collector and storage tank dimensions. The results emphasized that there is a specific storage tank dimension associated to a specific solar collector dimension that could ensure the longest continuous startup operation of the cooling system when constant mass flow rates inside the system are assumed.

  19. Studies on thermal neutron perturbation factor needed for bulk sample activation analysis

    CERN Document Server

    Csikai, J; Sanami, T; Michikawa, T

    2002-01-01

    The spatial distribution of thermal neutrons produced by an Am-Be source in a graphite pile was measured via the activation foil method. The results obtained agree well with calculated data using the MCNP-4B code. A previous method used for the determination of the average neutron flux within thin absorbing samples has been improved and extended for a graphite moderator. A procedure developed for the determination of the flux perturbation factor renders the thermal neutron activation analysis of bulky samples of unknown composition possible both in hydrogenous and graphite moderators.

  20. The MCNP code in planning and interpretation of thermal neutron pulsed experiments

    Energy Technology Data Exchange (ETDEWEB)

    Dabrowska, J.; Drozdowicz, K.; Woznicka, U. [The Henryk Niewodniczanski Inst. of Nuclear Physics, Krakow (Poland)

    2001-07-01

    A possibility to use the MCNP code to support planning and interpretation of the neutron pulsed experiments is discussed. Example of the simulated experiments for polyethylene are shown and compared to the real experimental results. A usefulness of the MCNP code for consideration of the time-dependent thermal neutron fields is stated. There are indicated some properties of the code and cross-section libraries which create problems or make impossible its using for many hydrogenous materials when the thermal neutron transport has to be considered with a high accuracy. (orig.)

  1. Thermal neutron scattering law calculations using ab initio molecular dynamics

    Science.gov (United States)

    Wormald, Jonathan; Hawari, Ayman I.

    2017-09-01

    In recent years, methods for the calculation of the thermal scattering law (i.e. S(α,β), where α and β are dimensionless momentum and energy transfer variables, respectively) were developed based on ab initio lattice dynamics (AILD) and/or classical molecular dynamics (CMD). While these methods are now mature and efficient, further advancement in the application of such atomistic techniques is possible using ab initio molecular dynamics (AIMD) methods. In this case, temperature effects are inherently included in the calculation, e.g. phonon density of states (DOS), while using ab initio force fields that eliminate the need for parameterized semi-empirical force fields. In this work, AIMD simulations were performed to predict the phonon spectra as a function of temperature for beryllium and graphite, which are representative nuclear reactor moderator and reflector materials. Subsequently, the calculated phonon spectra were utilized to predict S(α,β) using the LEAPR module of the NJOY code. The AIMD models of beryllium and graphite were 5 × 5 × 5 crystal unit cells (250 atoms and 500 atoms respectively). Electronic structure calculations for the prediction of Hellman-Feynman forces were performed using density functional theory with a GGA exchange correlation functional and corresponding core electron pseudopotentials. AIMD simulations of 1000-10,000 time-steps were performed with the canonical ensemble (NVT thermostat) for several temperatures between 300 K and 900 K. The phonon DOS were calculated as the power spectrum of the AIMD predicted velocity autocorrelation functions. The resulting AIMD phonon DOS and corresponding inelastic thermal neutron scattering cross sections at 300 K, where anharmonic effects are expected to be small, were found to be in reasonable agreement with the results generated using traditional AILD. This illustrated the validity of the AIMD approach. However, since the impact of the temperature on the phonon DOS (e.g. broadening of

  2. EAS thermal neutron detection with the PRISMA-LHAASO-16 experiment

    Science.gov (United States)

    Li, B.-B.; Alekseenko, V. V.; Cui, S.-w.; Chen, T.-L.; Dangzengluobu; Feng, S.-H.; Gao, Q.; Liu, Y.; Huang, Q.-C.; He, Y.-Y.; Liu, M.-Y.; Ma, X.-H.; Pozdnyakov, E. I.; Shchegolev, O. B.; Shen, F.-Z.; Stenkin, Yu. V.; Stepanov, V. I.; Yanin, Ya. V.; Yao, J.-D.; Zhou, R.

    2017-12-01

    EAS (extensive air shower) thermal neutron measurement gives advantages to study energy and mass composition of primary cosmic rays especially in the knee region. After the success of the PRISMA-YBJ experiment, we build a new EAS thermal neutron detection array at Tibet University, Lhasa, China (3700 m a.s.l.) in March, 2017. This prototype array so called "PRISMA-LHAASO-16" consists of 16 EAS EN-detectors ("EN" is abbreviation for electron and neutron) measuring two main EAS components: hadronic and electromagnetic ones. Different from PRISMA-YBJ, these detectors use a thin layer of a novel type of ZnS(Ag) scintillator alloyed with natural boron compound for thermal neutron capture. PRISMA-LHAASO-16 will be moved to the LHAASO site in the near future. In this paper, we introduce principle of the detection technique, deployment of the array, and the test results of the array.

  3. INTENSE THERMAL NEUTRON FIELDS FROM A MEDICAL-TYPE LINAC: THE E_LIBANS PROJECT.

    Science.gov (United States)

    Costa, M; Durisi, E; Ferrero, M; Monti, V; Visca, L; Anglesio, S; Bedogni, R; Gomez-Ros, J M; Romano, M; Planell, O Sans; Treccani, M; Bortot, D; Pola, A; Alikaniotis, K; Giannini, G

    2017-12-22

    The e_LiBANS project aims at producing intense thermal neutron fields for diverse interdisciplinary irradiation purposes. It makes use of a reconditioned medical electron LINAC, recently installed at the Physics Department and INFN in Torino, coupled to a dedicated photo-converter, developed within this collaboration, that uses (γ,n) reaction within high Z targets. Produced neutrons are then moderated to thermal energies and concentrated in an irradiation volume. To measure and to characterize in real time the intense field inside the cavity new thermal neutron detectors were designed with high radiation resistance, low noise and very high neutron-to-photon discrimination capability. This article offers an overview of the e_LiBANS project and describes the results of the benchmark experiment. © The Author(s) 2017. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

  4. Optimizing Neutron Thermal Scattering Effects in very High Temperature Reactors. Final Report

    Energy Technology Data Exchange (ETDEWEB)

    Hawari, Ayman [North Carolina State Univ., Raleigh, NC (United States). Dept. of Nuclear Engineering; Ougouag, Abderrafi [Idaho National Lab. (INL), Idaho Falls, ID (United States)

    2014-07-08

    This project aims to develop a holistic understanding of the phenomenon of neutron thermalization in the VHTR. Neutron thermalization is dependent on the type and structure of the moderating material. The fact that the moderator (and reflector) in the VHTR is a solid material will introduce new and interesting considerations that do not apply in other (e.g. light water) reactors. The moderator structure is expected to undergo radiation induced changes as the irradiation (or burnup) history progresses. In this case, the induced changes in structure will have a direct impact on many properties including the neutronic behavior. This can be easily anticipated if one recognizes the dependence of neutron thermalization on the scattering law of the moderator. For the pebble bed reactor, it is anticipated that the moderating behavior can be tailored, e.g. using moderators that consist of composite materials, which could allow improved optimization of the moderator-to-fuel ratio.

  5. Improved Neutron Capture Cross Section Measurements with the n_TOF Total Absorption Calorimeter

    CERN Document Server

    Mendoza, E; Perkowski, J; Andriamonje, S; Carrapico, C; Moinul, M; Vannini, G; Quesada, J M; Harrisopulos, S; Milazzo, P M; Berthier, B; Lozano, M; Krticka, M; Domingo-Pardo, C; Nolte, R; Chiaveri, E; Saarmento, H; Jericha, E; Ferrari, A; Massimi, C; Giubrone, G; Avrigeanu, V; Martinez, T; Guerrero, C; Andrzejewski, J; Karadimos, D; Mengoni, A; Ganesan, S; Vlachoudis, V; Becares, V; Cortes, G; Variale, V; Losito, H; Calvino, F; Kappeler, F; Gunsing, F; Gramegna, F; Colonna, N; Marrone, S; Pavlik, A; Berthoumieux, E; Paradela, C; Mastinu, P F; Vaz, P; Tassan-Got, L; Kadi, Y; Tarrio, D; Cano-Ott, D; Brugger, M; Wallner, A; Audouin, L; Fernandez-Ordonez, M; Becvar, F; Goncalves, I F; Cerutti, F; Ventura, A; Mosconi, M; Tagliente, G; Duran, I; Casado, A; Ioannides, K; Weiss, C; Mirea, M; Gomez-Hornillos, M B; Vlastou, R; Calviani, M; Lederer, C; Gonzalez-Romero, E; Marganiec, J; Vidriales, J J; Lebbos, E; Leeb, H; Heil, M; Dillmann, I; Tain, J L; Belloni, F

    2011-01-01

    The n\\_TOF collaboration operates a Total Absorption Calorimeter (TAC) {[}1] for measuring neutron capture cross-sections of low-mass and/or radioactive samples. The results obtained with the TAC have led to a substantial improvement of the capture cross sections of (237)Np and (240)Pu {[}2]. The experience acquired during the first measurements has allowed us to optimize the performance of the TAC and to improve the capture signal to background ratio, thus opening the way to more complex and demanding measurements on rare radioactive materials. The new design has been reached by a series of detailed Monte Carlo simulations of complete experiments and dedicated test measurements. The new capture setup will be presented and the main achievements highlighted.

  6. Fast and thermal neutron intensity measurements at the KFUPM PGNAA setup

    CERN Document Server

    Al-Jarallah, M I; Fazal-Ur-Rehman; Abu-Jarad, F A

    2002-01-01

    Fast and thermal neutron intensity distributions have been measured at an accelerator based prompt gamma ray neutron activation analysis (PGNAA) setup. The setup is built at the 350 keV accelerator laboratory of King Fahd University of Petroleum and Minerals (KFUPM). The setup is mainly designed to carry out PGNAA elemental analysis via thermal neutron capture. In this study relative intensity of fast and thermal neutrons was measured as a function of the PGNAA moderator assembly parameters using nuclear track detectors (NTDs). The relative intensity of the neutrons was measured inside the sample region as a function of front moderator thickness as well as sample length. Measurements were carried out at the KFUPM 350 keV accelerator using 2.8 MeV pulsed neutron beam from D(d,n) reaction. The pulsed deuteron beam with 5 ns pulse width and 30 kHz frequency was used to produce neutrons. Experimental results were compared with results of Monte Carlo design calculations of the PGNAA setup. A good agreement has bee...

  7. Fast and thermal neutron intensity measurements at the KFUPM PGNAA setup

    Energy Technology Data Exchange (ETDEWEB)

    Al-Jarallah, M.I.; Naqvi, A.A. E-mail: aanaqvi@kfupm.edu.sa; Fazal-ur-Rehman; Abu-jarad, F

    2002-10-01

    Fast and thermal neutron intensity distributions have been measured at an accelerator based prompt gamma ray neutron activation analysis (PGNAA) setup. The setup is built at the 350 keV accelerator laboratory of King Fahd University of Petroleum and Minerals (KFUPM). The setup is mainly designed to carry out PGNAA elemental analysis via thermal neutron capture. In this study relative intensity of fast and thermal neutrons was measured as a function of the PGNAA moderator assembly parameters using nuclear track detectors (NTDs). The relative intensity of the neutrons was measured inside the sample region as a function of front moderator thickness as well as sample length. Measurements were carried out at the KFUPM 350 keV accelerator using 2.8 MeV pulsed neutron beam from D(d,n) reaction. The pulsed deuteron beam with 5 ns pulse width and 30 kHz frequency was used to produce neutrons. Experimental results were compared with results of Monte Carlo design calculations of the PGNAA setup. A good agreement has been found between the experimental results and the calculations.

  8. RBE of thermal neutrons for induction of chromosome aberrations in human lymphocytes.

    Science.gov (United States)

    Schmid, E; Wagner, F M; Canella, L; Romm, H; Schmid, T E

    2013-03-01

    The induction of chromosome aberrations in human lymphocytes irradiated in vitro with slow neutrons was examined to assess the maximum low-dose RBE (RBE(M)) relative to (60)Co γ-rays. For the blood irradiations, cold neutron beam available at the prompt gamma activation analysis facility at the Munich research reactor FRM II was used. The given flux of cold neutrons can be converted into a thermally equivalent one. Since blood was taken from the same donor whose blood had been used for previous irradiation experiments using widely varying neutron energies, the greatest possible accuracy was available for such an estimation of the RBE(M) avoiding the inter-individual variations or differences in methodology usually associated with inter-laboratory comparisons. The magnitude of the coefficient α of the linear dose-response relationship (α = 0.400 ± 0.018 Gy(-1)) and the derived RBE(M) of 36.4 ± 13.3 obtained for the production of dicentrics by thermal neutrons confirm our earlier observations of a strong decrease in α and RBE(M) with decreasing neutron energy lower than 0.385 MeV (RBE(M) = 94.4 ± 38.9). The magnitude of the presently estimated RBE(M) of thermal neutrons is-with some restrictions-not significantly different to previously reported RBE(M) values of two laboratories.

  9. Study of neutron migration ion a multiplying medium according to the intensity and distribution of absorptions; Etude de la migration des neutrons dans un milieu multiplicateur en fonction de l'intensite et de la distribution des captures

    Energy Technology Data Exchange (ETDEWEB)

    Naudet, R. [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1964-07-01

    The calculation of the neutron migration area assumes a simple form in two limiting cases: the case of pure slowing down and the case of purely thermal diffusion. In a thermal reactor, through these two schemes can be more or less applied at the start and finish of the life of the neutron, we must also consider a transition zone, in which the phenomena are obviously far more complex. How is the link to be made, and in what way does it depend on the distribution law of the captures? Two different methods have been developed to solve this problem. In the first one, the neutron is tracked through successive collisions, and attention is particularly concentrated on the variation of the absorption probability; in the second one, the spectrum is considered as a whole, the balance of neutrons arriving and disappearing at each velocity being written down. It is proved, moreover, that the two methods are based on the same formulation. The first one gives rise to interesting interpretations which permit a deep understanding of the physical phenomena; the second produces easier calculation, through the new thermalization operators developed at Saclay, The parameters of the problem are being studied successively (thermalization model, absorption law, variation law of the diffusion coefficient, geometrical parameters of the cell, relative importance of the leakages) For each of then, numerical applications are presented. (author) [French] Le calcul de l'aire de migration des neutrons se formule simplement dans deux cas limites: celui du ralentissement pur, et celui de la diffusion purement thermique. Dans un reacteur thermique, si on peut a la rigueur utiliser ces deux schemas au debut et a la fin de la vie des neutrons, il faut bien aussi considerer une zone de transition ou les phenomenes sont visiblement plus complexes. Comment effectuer le raccordement, et comment depend-il de la loi de repartition des captures? Deux methodes differentes ont ete etudiees pour resoudre

  10. Variation of the thermal neutron diffusion cooling properties of wet rock material (Monte Carlo simulations of the pulsed neutron experiments)

    Energy Technology Data Exchange (ETDEWEB)

    Drozdowicz, K. [Henryk Niewodniczanski Institute of Nuclear Physics, Polish Academy of Sciences, ul. Radzikowskiego 152, PL-31-342 Cracow (Poland)]. E-mail: krzysztof.drozdowicz@ifj.edu.pl; Krynicka, E. [Henryk Niewodniczanski Institute of Nuclear Physics, Polish Academy of Sciences, ul. Radzikowskiego 152, PL-31-342 Cracow (Poland); Dabrowska, J. [Henryk Niewodniczanski Institute of Nuclear Physics, Polish Academy of Sciences, ul. Radzikowskiego 152, PL-31-342 Cracow (Poland)

    2005-03-01

    The water content in a rock material can significantly change the thermal neutron diffusion parameters with respect to those of the dry medium. The effect has been studied for dolomite, CaMg(CO{sub 3}){sub 2}, by Monte Carlo simulations of the variable buckling experiments for 10 series of samples. The density-removed diffusion cooling coefficient C{sup M} varies hyperbolically by two orders of magnitude with water content in the range of 0-20%.

  11. Numerical Simulations of Pillar Structured Solid State Thermal Neutron Detector Efficiency and Gamma Discrimination

    Energy Technology Data Exchange (ETDEWEB)

    Conway, A; Wang, T; Deo, N; Cheung, C; Nikolic, R

    2008-06-24

    This work reports numerical simulations of a novel three-dimensionally integrated, {sup 10}boron ({sup 10}B) and silicon p+, intrinsic, n+ (PIN) diode micropillar array for thermal neutron detection. The inter-digitated device structure has a high probability of interaction between the Si PIN pillars and the charged particles (alpha and {sup 7}Li) created from the neutron - {sup 10}B reaction. In this work, the effect of both the 3-D geometry (including pillar diameter, separation and height) and energy loss mechanisms are investigated via simulations to predict the neutron detection efficiency and gamma discrimination of this structure. The simulation results are demonstrated to compare well with the measurement results. This indicates that upon scaling the pillar height, a high efficiency thermal neutron detector is possible.

  12. Enhancement of thermal neutron shielding of cement mortar by using borosilicate glass powder.

    Science.gov (United States)

    Jang, Bo-Kil; Lee, Jun-Cheol; Kim, Ji-Hyun; Chung, Chul-Woo

    2017-05-01

    Concrete has been used as a traditional biological shielding material. High hydrogen content in concrete also effectively attenuates high-energy fast neutrons. However, concrete does not have strong protection against thermal neutrons because of the lack of boron compound. In this research, boron was added in the form of borosilicate glass powder to increase the neutron shielding property of cement mortar. Borosilicate glass powder was chosen in order to have beneficial pozzolanic activity and to avoid deleterious expansion caused by an alkali-silica reaction. According to the experimental results, borosilicate glass powder with an average particle size of 13µm showed pozzolanic activity. The replacement of borosilicate glass powder with cement caused a slight increase in the 28-day compressive strength. However, the incorporation of borosilicate glass powder resulted in higher thermal neutron shielding capability. Thus, borosilicate glass powder can be used as a good mineral additive for various radiation shielding purposes. Copyright © 2017 Elsevier Ltd. All rights reserved.

  13. Non-destructive assay of mechanical components using gamma-rays and thermal neutrons

    Science.gov (United States)

    Souza, Erica Silvani; de Almeida, Gevaldo L.; Souza, Maria Ines S.; Avelino, Mila R.

    2013-05-01

    This work presents the results obtained in the inspection of several mechanical components through neutron and gamma-ray transmission radiography. The 4.46 × 105 n.cm-2.s-1 thermal neutron flux available at the main port of the Argonauta research reactor in Instituto de Engenharia Nuclear has been used as source for the neutron radiographic imaging. The 412 keV γ-ray emitted by 198Au, also produced in that reactor, has been used as interrogation agent for the gamma radiography. Imaging Plates - IP specifically designed to operate with thermal neutrons or with X-rays have been employed as detectors and storage devices for each of these radiations.

  14. Underground physics and the barometric pumping effect observed for thermal neutron flux underground

    Science.gov (United States)

    Stenkin, Yu. V.; Alekseenko, V. V.; Gromushkin, D. M.; Sulakov, V. P.; Shchegolev, O. B.

    2017-05-01

    It is known that neutron background is a major problem for low-background experiments carrying out underground, such as dark matter search, double-beta decay searches and other experiments known as Underground Physics. We present here some results obtained with the en-detector of 0.75 m2, which is running for more than 4 years underground at a depth of 25 m water equivalent in Skobeltsyn Institute of Nuclear Physics, Moscow State University. Some spontaneous increases in thermal neutron flux up to a factor of 3 were observed in delayed anti-correlation with barometric pressure. The phenomenon can be explained by the radon barometric pumping effect resulting in similar effect in neutron flux being produced in (α, n)-reactions by alpha-decays of radon and its daughters in surrounding rock. This is the first demonstration of the barometric pumping effect observed in thermal neutron flux underground.

  15. Real-time detection of fast and thermal neutrons in radiotherapy with CMOS sensors.

    Science.gov (United States)

    Arbor, Nicolas; Higueret, Stephane; Elazhar, Halima; Combe, Rodolphe; Meyer, Philippe; Dehaynin, Nicolas; Taupin, Florence; Husson, Daniel

    2017-03-07

    The peripheral dose distribution is a growing concern for the improvement of new external radiation modalities. Secondary particles, especially photo-neutrons produced by the accelerator, irradiate the patient more than tens of centimeters away from the tumor volume. However the out-of-field dose is still not estimated accurately by the treatment planning softwares. This study demonstrates the possibility of using a specially designed CMOS sensor for fast and thermal neutron monitoring in radiotherapy. The 14 microns-thick sensitive layer and the integrated electronic chain of the CMOS are particularly suitable for real-time measurements in γ/n mixed fields. An experimental field size dependency of the fast neutron production rate, supported by Monte Carlo simulations and CR-39 data, has been observed. This dependency points out the potential benefits of a real-time monitoring of fast and thermal neutron during beam intensity modulated radiation therapies.

  16. Methodology of measurement of thermal neutron time decay constant in Canberra 35+ MCA system

    Energy Technology Data Exchange (ETDEWEB)

    Drozdowicz, K.; Gabanska, B.; Igielski, A.; Krynicka, E.; Woznicka, U. [Institute of Nuclear Physics, Cracow (Poland)

    1993-12-31

    A method of the thermal neutron time decay constant measurement in small bounded media is presented. A 14 MeV pulsed neutron generator is the neutron source. The system of recording of a die-away curve of thermal neutrons consists of a {sup 3}He detector and of a multichannel time analyzer based on analyzer Canberra 35+ with multi scaler module MCS 7880 (microsecond range). Optimum parameters for the measuring system are considered. Experimental verification of a dead time of the instrumentation system is made and a count-loss correction is incorporated into the data treatment. An attention is paid to evaluate with a high accuracy the fundamental mode decay constant of the registered decaying curve. A new procedure of the determination of the decay constant by a multiple recording of the die-away curve is presented and results of test measurements are shown. (author). 11 refs, 12 figs, 4 tabs.

  17. Thermal Neutron Capture Branching Ratio of 209BI Using a Gamma-Ray Technique

    Science.gov (United States)

    Letourneau, A.; Berthoumieux, E.; Deruelle, O.; Fadil, M.; Fioni, G.; Gunsing, F.; Marie, F.; Perrot, L.; Ridikas, D.; Boerner, H.; Faust, H.; Mutti, P.; Simpson, G.; Schillebeeckx, P.

    2003-06-01

    A new experimental program concerning the measurement of the neutron capture branching ratio of 209Bi as a function of neutron energy has been proposed recently. The preliminary results obtained at the high neutron flux reactor of ILL with a thermal neutron flux are presented in this paper. The neutron capture cross section and the corresponding branching ratio are measured with an on-line gamma-ray spectroscopy method. We find for the capture cross section 35±1.75 mb, what is in a good agreement with existing results. For the partial cross sections we get σ210gs = 17.9±2 mb and σ210m =17.1±2 mb giving a branching ratio of 51%±5%. This value is by 25% smaller than values from evaluated libraries.

  18. Development of MCATHAS system of coupled neutronics/thermal-hydraulics in supercritical water reactor

    Energy Technology Data Exchange (ETDEWEB)

    An, P.; Yao, D. [Science and Tech. on Reactor System Design Tech. Laboratory, Chengdu (China)

    2011-07-01

    The MCATHAS system of coupled neutronics/Thermal-hydraulics in supercritical water reactor is described, which considers the mutual influence between the obvious axial and radial evolution of material temperature, water density and the relative power distribution. This system can obtain the main neutronics and thermal parameters along with burn-up. MCATHAS system is parallel processing coupling. The MCNP code is used for neutronics analysis with the continuous cross section library at any temperature calculated by interpolation algorithm; The sub-channel code ATHAS is for thermal-hydraulics analysis and the ORIGEN Code for burn-up calculation. We validate the code with the assembly of HPLWR and analyze the assembly SCLWR- H. (author)

  19. Geant4 and MCNPX simulations of thermal neutron detection with planar silicon detectors

    Energy Technology Data Exchange (ETDEWEB)

    Guardiola, C; Fleta, C; Quirion, D; Lozano, M [Instituto de Microelectronica de Barcelona, (IMB-CNM), CSIC, 08193 Bellaterra, Barcelona (Spain); Amgarou, K [Departamento de FIsica, Universidad Autonoma de Barcelona, 08193 Bellaterra, Barcelona (Spain); GarcIa, F, E-mail: Consuelo.Guardiola@imb-cnm.csic.es [Helsinki Institute of Physics, University of Helsinki, 00014 Helsinki (Finland)

    2011-09-15

    We used Geant4 and MCNPX codes to evaluate the detection efficiency of planar silicon detectors coupled to different Boron-based converters with varied compositions and thicknesses that detect thermal neutrons via the {sup 10}B(n,{alpha}){sup 7}Li nuclear reaction. Few studies about the thermal neutron transport in Geant4 have been reported so far and it is becoming increasingly difficult to ignore its discrepancies with MCNPX in this neutron energy range. In the thermal energy range, Geant4 shows high discrepancies with MCNPX giving a maximum efficiency of about 3.3% in the {sup 10}B case whereas that obtained with MCNPX was 5%. Disagreements obtained between both codes in this energy range are analyzed and discussed.

  20. Measured Thermal and Fast Neutron Fluence Rates for ATF-1 Holders During ATR Cycle 157D

    Energy Technology Data Exchange (ETDEWEB)

    Smith, Larry Don [Idaho National Lab. (INL), Idaho Falls, ID (United States); Miller, David Torbet [Idaho National Lab. (INL), Idaho Falls, ID (United States)

    2016-03-01

    This report contains the thermal (2200 m/s) and fast (E>1MeV) neutron fluence rate data for the ATF-1 holders located in core for ATR Cycle 157D which were measured by the Radiation Measurements Laboratory (RML) as requested by the Power Reactor Programs (ATR Experiments) Radiation Measurements Work Order. This report contains measurements of the fluence rates corresponding to the particular elevations relative to the 80-ft. core elevation. The data in this report consist of (1) a table of the ATR power history and distribution, (2) a hard copy listing of all thermal and fast neutron fluence rates, and (3) plots of both the thermal and fast neutron fluence rates. The fluence rates reported are for the average power levels given in the table of power history and distribution.

  1. Error corrections for quantitative thermal neutron computed tomography

    Science.gov (United States)

    Shi, Liang

    A state-of-the art, two mirror reflection, combination of a Li-6 scintillation screen and a cooled CCD camera high spatial resolution neutron radioscopy imaging system was designed and developed in the RSEC at Penn State. Radiation shielding was applied to the imaging system to achieve a higher spatial resolution. Modulation Transfer Function (MTF) analysis shows that a spatial resolution of 116 microns was achieved. The imaging system was successfully applied for diagnostic measurements of hydrogen fuel cells. A quantitative neutron computed tomography NCT model was developed which confirmed the fundamental computed tomography theory. The model justified the partial volume neutron computed tomography water/ice mass evaluation technique which was designed and tested by Heller. The evaluation results of the water/ice mass using the NCT method was very close to the theoretical value. Sample and background neutron scattering effects were considered as one of the errors that influenced the accuracy of the quantitative measurement using the NCT method. The neutron scattering effect induced cupping artifacts that also contributed to the error in the measurement of water/ice mass using NCT. One method was developed to reduce the cupping artifacts in the reconstruction slice of the water/ice column. The geometric unsharpness, Ug, was demonstrated as the predominant source of error for the accuracy of the 3-D water/ice mass evaluation technique. A unique method was established to reduce the divergence neutron beam associated geometric unsharpness Ug. Compared to the de-convolution algorithm used in de-blurring the image projection, the method has the advantage of minimizing the unsharpness while keeping the degree of cupping through the water column the same. For the 3-D water/ice mass evaluation purpose, this method is a better choice for the water quantification technique error correction.

  2. Parity non-conservation in the capture of polarized thermal neutrons

    DEFF Research Database (Denmark)

    Warming, Inge Elisabeth

    1969-01-01

    The asymmetry in the intensity of γ-radiation following the capture of polarized thermal neutrons in 113Cd has been measured with Ge(Li) detectors. The result, A = (−0.6±1.8)×10−4, like that previously reported [1], gives no evidence for a non-zero effect.......The asymmetry in the intensity of γ-radiation following the capture of polarized thermal neutrons in 113Cd has been measured with Ge(Li) detectors. The result, A = (−0.6±1.8)×10−4, like that previously reported [1], gives no evidence for a non-zero effect....

  3. Neutronic and thermal hydraulic analysis for production of fission molybdenum-99 at Pakistan Research Reactor-1

    Energy Technology Data Exchange (ETDEWEB)

    Mushtaq, A. [Isotope Production Division, Pakistan Institute of Nuclear Science and Technology, P.O. Nilore, Islamabad (Pakistan)], E-mail: mushtaqa@pinstech.org.pk; Iqbal, Massod; Bokhari, Ishtiaq Hussain; Mahmood, Tariq; Mahmood, Tayyab; Ahmad, Zahoor; Zaman, Qamar [Nuclear Engineering Division, Pakistan Institute of Nuclear Science and Technology, P.O. Nilore, Islamabad (Pakistan)

    2008-02-15

    Neutronic and thermal hydraulic analysis for the fission molybdenum-99 production at PARR-1 has been performed. Low enriched uranium foil (<20% {sup 235}U) will be used as target material. Annular target designed by ANL (USA) will be irradiated in PARR-1 for the production of 100 Ci of molybdenum-99 at the end of irradiation, which will be sufficient to prepare required {sup 99}Mo/{sup 99m}Tc generators at PINSTECH and its supply in the country. Neutronic and thermal hydraulic analysis were performed using various codes. Data shows that annular targets can be safely irradiated in PARR-1 for production of required amount of fission molybdenum-99.

  4. Thermal neutron capture and resonance integral cross sections of {sup 45}Sc

    Energy Technology Data Exchange (ETDEWEB)

    Van Do, Nguyen; Duc Khue, Pham; Tien Thanh, Kim [Institute of Physics, Vietnam Academy of Science and Technology, 10 Dao Tan, Hanoi (Viet Nam); Thi Hien, Nguyen [Institute of Physics, Vietnam Academy of Science and Technology, 10 Dao Tan, Hanoi (Viet Nam); Department of Physics and Center for High Energy Physics, Kyungpook National University, Daegu 702-701 (Korea, Republic of); Kim, Guinyun, E-mail: gnkim@knu.ac.kr [Department of Physics and Center for High Energy Physics, Kyungpook National University, Daegu 702-701 (Korea, Republic of); Kim, Kwangsoo [Department of Physics and Center for High Energy Physics, Kyungpook National University, Daegu 702-701 (Korea, Republic of); Shin, Sung-Gyun; Cho, Moo-Hyun [Department of Advanced Nuclear Engineering, Pohang University of Science and Technology, Pohang 790-784 (Korea, Republic of); Lee, Manwoo [Research Center, Dongnam Institute of Radiological and Medical Science, Busan 619-953 (Korea, Republic of)

    2015-11-01

    The thermal neutron cross section (σ{sub 0}) and resonance integral (I{sub 0}) of the {sup 45}Sc(n,γ){sup 46}Sc reaction have been measured relative to that of the {sup 197}Au(n,γ){sup 198}Au reaction by means of the activation method. High-purity natural scandium and gold foils without and with a cadmium cover of 0.5 mm thickness were irradiated with moderated pulsed neutrons produced from the Pohang Neutron Facility (PNF). The induced activities in the activated foils were measured with a high purity germanium (HPGe) detector. In order to improve the accuracy of the experimental results the counting losses caused by the thermal (G{sub th}) and resonance (G{sub epi}) neutron self-shielding, the γ-ray attenuation (F{sub g}) and the true γ-ray coincidence summing effects were made. In addition, the effect of non-ideal epithermal spectrum was also taken into account by determining the neutron spectrum shape factor (α). The thermal neutron cross-section and resonance integral of the {sup 45}Sc(n,γ){sup 46}Sc reaction have been determined relative to the reference values of the {sup 197}Au(n,γ){sup 198}Au reaction, with σ{sub o,Au} = 98.65 ± 0.09 barn and I{sub o,Au} = 1550 ± 28 barn. The present thermal neutron cross section has been determined to be σ{sub o,Sc} = 27.5 ± 0.8 barn. According to the definition of cadmium cut-off energy at 0.55 eV, the present resonance integral cross section has been determined to be I{sub o,Sc} = 12.4 ± 0.7 barn. The present results are compared with literature values and discussed.

  5. Thermal neutron capture and resonance integral cross sections of 45Sc

    Science.gov (United States)

    Van Do, Nguyen; Duc Khue, Pham; Tien Thanh, Kim; Thi Hien, Nguyen; Kim, Guinyun; Kim, Kwangsoo; Shin, Sung-Gyun; Cho, Moo-Hyun; Lee, Manwoo

    2015-11-01

    The thermal neutron cross section (σ0) and resonance integral (I0) of the 45Sc(n,γ)46Sc reaction have been measured relative to that of the 197Au(n,γ)198Au reaction by means of the activation method. High-purity natural scandium and gold foils without and with a cadmium cover of 0.5 mm thickness were irradiated with moderated pulsed neutrons produced from the Pohang Neutron Facility (PNF). The induced activities in the activated foils were measured with a high purity germanium (HPGe) detector. In order to improve the accuracy of the experimental results the counting losses caused by the thermal (Gth) and resonance (Gepi) neutron self-shielding, the γ-ray attenuation (Fg) and the true γ-ray coincidence summing effects were made. In addition, the effect of non-ideal epithermal spectrum was also taken into account by determining the neutron spectrum shape factor (α). The thermal neutron cross-section and resonance integral of the 45Sc(n,γ)46Sc reaction have been determined relative to the reference values of the 197Au(n,γ)198Au reaction, with σo,Au = 98.65 ± 0.09 barn and Io,Au = 1550 ± 28 barn. The present thermal neutron cross section has been determined to be σo,Sc = 27.5 ± 0.8 barn. According to the definition of cadmium cut-off energy at 0.55 eV, the present resonance integral cross section has been determined to be Io,Sc = 12.4 ± 0.7 barn. The present results are compared with literature values and discussed.

  6. Neutronic reactor

    Science.gov (United States)

    Wende, Charles W. J.; Babcock, Dale F.; Menegus, Robert L.

    1983-01-01

    A nuclear reactor includes an active portion with fissionable fuel and neutron moderating material surrounded by neutron reflecting material. A control element in the active portion includes a group of movable rods constructed of neutron-absorbing material. Each rod is movable with respect to the other rods to vary the absorption of neutrons and effect control over neutron flux.

  7. Neutronic reactor

    Energy Technology Data Exchange (ETDEWEB)

    Babcock, D.F.; Menegus, R.L.; Wende, C.W.

    1983-01-04

    A nuclear reactor includes an active portion with fissionable fuel and neutron moderating material surrounded by neutron reflecting material. A control element in the active portion includes a group of movable rods constructed of neutron-absorbing material. Each rod is movable with respect to the other rods to vary the absorption of neutrons and effect control over neutron flux.

  8. Absorption coefficient of nearly transparent liquids measured using thermal lens spectrometry

    Directory of Open Access Journals (Sweden)

    H.Cabrera

    2006-01-01

    Full Text Available We use an optimized pump-probe mode-mismatched thermal lens scheme to determine the optical absorption coefficient and thermal diffusivity of ethanol, benzene, acetone, methanol, toluene and chloroform. In this scheme the excitation beam is focused in the presence of a collimated probe beam. The agreement between experimentally obtained results and values reported in the literature is good.

  9. Compensated gadolinium-loaded plastic scintillators for thermal neutron detection (and counting)

    Energy Technology Data Exchange (ETDEWEB)

    Dumazert, Jonathan; Coulon, Romain; Bertrand, Guillaume H. V.; Hamel, Matthieu; Sguerra, Fabien; Dehe-Pittance, Chrystele; Normand, Stephane [CEA, LIST, Laboratoire Capteurs Architectures Electroniques, 99 Gif-sur-Yvette, (France); Mechin, Laurence [CNRS, UCBN, Groupe de Recherche en Informatique, Image, Automatique et Instrumentation de Caen, 4050 Caen, (France)

    2015-07-01

    Plastic scintillator loading with gadolinium-rich organometallic complexes shows a high potential for the deployment of efficient and cost-effective neutron detectors. Due to the low-energy photon and electron signature of thermal neutron capture by gadolinium-155 and gadolinium-157, alternative treatment to Pulse Shape Discrimination has to be proposed in order to display a trustable count rate. This paper discloses the principle of a compensation method applied to a two-scintillator system: a detection scintillator interacts with photon radiation and is loaded with gadolinium organometallic compound to become a thermal neutron absorber, while a non-gadolinium loaded compensation scintillator solely interacts with the photon part of the incident radiation. Posterior to the nonlinear smoothing of the counting signals, a hypothesis test determines whether the resulting count rate after photon response compensation falls into statistical fluctuations or provides a robust image of a neutron activity. A laboratory prototype is tested under both photon and neutron irradiations, allowing us to investigate the performance of the overall compensation system in terms of neutron detection, especially with regards to a commercial helium-3 counter. The study reveals satisfactory results in terms of sensitivity and orientates future investigation toward promising axes. (authors)

  10. Hydrogen Absorption in Metal Thin Films and Heterostructures Investigated in Situ with Neutron and X-ray Scattering

    Directory of Open Access Journals (Sweden)

    Sara J. Callori

    2016-05-01

    Full Text Available Due to hydrogen possessing a relatively large neutron scattering length, hydrogen absorption and desorption behaviors in metal thin films can straightforwardly be investigated by neutron reflectometry. However, to further elucidate the chemical structure of the hydrogen absorbing materials, complementary techniques such as high resolution X-ray reflectometry and diffraction remain important too. Examples of work on such systems include Nb- and Pd-based multilayers, where Nb and Pd both have strong affinity to hydrogen. W/Nb and Fe/Nb multilayers were measured in situ with unpolarized and polarized neutron reflectometry under hydrogen gas charging conditions. The gas-pressure/hydrogen-concentration dependence, the hydrogen-induced macroscopic film swelling as well as the increase in crystal lattice plane distances of the films were determined. Ferromagnetic-Co/Pd multilayers were studied with polarized neutron reflectometry and in situ ferromagnetic resonance measurements to understand the effect of hydrogen absorption on the magnetic properties of the system. This electronic effect enables a novel approach for hydrogen sensing using a magnetic readout scheme.

  11. Determination of the 243,246,248Cm thermal neutron induced fission cross sections

    Science.gov (United States)

    Serot, O.; Wagemans, C.; Vermote, S.; Heyse, J.; Soldner, T.; Geltenbort, P.

    2005-11-01

    The minor actinide waste produced in nuclear power plants contains various Cm-isotopes, and transmutation scenarios require improved fission cross section data. The available thermal neutron induced fission cross section data for 243Cm, 246Cm and 248Cm are not very accurate, so new cross section measurements have been performed at the high flux reactor of the ILL in Grenoble (France) under better experimental conditions (highly enriched samples, very intense and clean neutron beam). The measurements were performed at a neutron energy of 5.38 meV, yielding fission cross section values of (1240±28)b for 243Cm, (25±47)mb for 246Cm and (685±84)mb for 248Cm. From these results, thermal fission cross section values of (572±14)b; (12±25)mb and (316±43)mb have been deduced for 243Cm, 246Cm and 248Cm, respectively.

  12. Determination of rare earths and thorium in apatites by thermal and epithermal neutron-activation analysis.

    Science.gov (United States)

    Brunfelt, A O; Roelandts, I

    1974-06-01

    A procedure is described for the non-destructive determination of Na, Mn, La, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Yb, Lu and Th in apatites by thermal and epithermal neutron-activation of independent portions of the material. The method was applied to three apatites with different contents. The precision obtained was better than +/-5% for La, Ce, Sm, Eu, Gd, Tb and Dy and +/-20% for Yb, Nd, Ho, Er and Lu for an apatite with a total rare-earth oxide content of the order of 1%. Determination of Ce, Tb and Yb could only be carried out with thermal neutron-activation analysis, while Gd, Ho and Er could only be determined after irradiation with epithermal neutrons.

  13. Negative Thermal Expansion in ZrW2O8: Mechanisms, Rigid Unit Modes, and Neutron Total Scattering

    Science.gov (United States)

    Tucker, Matthew G.; Goodwin, Andrew L.; Dove, Martin T.; Keen, David A.; Wells, Stephen A.; Evans, John S. O.

    2005-12-01

    The local structure of the low-temperature ordered phase of the negative thermal expansion (NTE) material ZrW2O8 has been investigated by reverse Monte Carlo (RMC) modeling of neutron total scattering data. We obtain, for the first time, quantitative measurements of the extent to which the WO4 and ZrO6 polyhedra move as rigid units, and we show that these values are consistent with the predictions of rigid unit mode theory. We suggest that rigid unit modes are associated with the NTE. Our results do not support a recent interpretation of x-ray-absorption fine structure spectroscopy data in terms of a larger rigid structural component involving the Zr-O-W linkage.

  14. {sup 6}LiF oleic acid capped nanoparticles entrapment in siloxanes for thermal neutron detection

    Energy Technology Data Exchange (ETDEWEB)

    Carturan, S., E-mail: sara.carturan@lnl.infn.it; Maggioni, G., E-mail: Gianluigi.maggioni@lnl.infn.it [Department of Physics and Astronomy, University of Padova, Via Marzolo 8, 35100 Padova (Italy); INFN, Laboratori Nazionali di Legnaro, Viale dell’Università 2, 35020 Legnaro (Italy); Marchi, T.; Gramegna, F.; Cinausero, M. [INFN, Laboratori Nazionali di Legnaro, Viale dell’Università 2, 35020 Legnaro (Italy); Quaranta, A. [Department of Industrial Engineering, University of Trento, Trento (Italy); INFN, Tifpa, Trento (Italy); Palma, M. Dalla [INFN, Laboratori Nazionali di Legnaro, Viale dell’Università 2, 35020 Legnaro (Italy); Department of Industrial Engineering, University of Trento, Trento (Italy)

    2016-07-07

    The good light output of siloxane based scintillators as displayed under γ-rays and α particles has been exploited here to obtain clear and reliable response toward thermal neutrons. Sensitization towards thermal neutrons has been pursued by adding {sup 6}LiF, in form of nanoparticles. Aiming at the enhancement of compatibility between the inorganic nanoparticles and the low polarity, siloxane based surrounding medium, oleic acid-capped {sup 6}LiF nanoparticles have been synthesized by thermal decomposition of Li trifluoroacetate. Thin pellets siloxane scintillator maintained their optical transmittance up to weight load of 2% of {sup 6}Li. Thin samples with increasing {sup 6}Li concentration and thicker ones with fixed {sup 6}Li amount have been prepared and tested with several sources (α, γ-rays, moderated neutrons). Light output as high as 80% of EJ212 under α irradiation was measured with thin samples, and negligible changes have been observed as a result of {sup 6}LiF addition. In case of thick samples, severe light loss has been observed, as induced by opacity. Nevertheless, thermal neutrons detection has been assessed and the data have been compared with GS20, based on Li glass, taken as a reference material.

  15. Monte Carlo simulations to advance characterisation of landmines by pulsed fast/thermal neutron analysis

    NARCIS (Netherlands)

    Maucec, M.; Rigollet, C.

    The performance of a detection system based on the pulsed fast/thermal neutron analysis technique was assessed using Monte Carlo simulations. The aim was to develop and implement simulation methods, to support and advance the data analysis techniques of the characteristic gamma-ray spectra,

  16. Measured thermal and fast neutron fluence rates for ATF-1 holders during ATR cycle 160A

    Energy Technology Data Exchange (ETDEWEB)

    Walker, B. J. [Idaho National Lab. (INL), Idaho Falls, ID (United States); Miller, D. T. [Idaho National Lab. (INL), Idaho Falls, ID (United States)

    2017-06-06

    This report contains the thermal (2200 m/s) and fast (E>1MeV) neutron fluence rate data for the ATF-1 holders located in core for ATR Cycle 160A which were measured by the Radiation Measurements Laboratory (RML).

  17. Advances in thermal hydraulic and neutronic simulation for reactor analysis and safety

    Energy Technology Data Exchange (ETDEWEB)

    Tentner, A.M.; Blomquist, R.N.; Canfield, T.R.; Ewing, T.F.; Garner, P.L.; Gelbard, E.M.; Gross, K.C.; Minkoff, M.; Valentin, R.A.

    1993-03-01

    This paper describes several large-scale computational models developed at Argonne National Laboratory for the simulation and analysis of thermal-hydraulic and neutronic events in nuclear reactors and nuclear power plants. The impact of advanced parallel computing technologies on these computational models is emphasized.

  18. Electrically and thermally conductive underwater acoustically absorptive graphene/rubber nanocomposites for multifunctional applications.

    Science.gov (United States)

    Li, Ying; Xu, Fan; Lin, Zaishan; Sun, Xianxian; Peng, Qingyu; Yuan, Ye; Wang, Shasha; Yang, Zhiyu; He, Xiaodong; Li, Yibin

    2017-10-05

    Graphene is ideal filler in nanocomposites due to its unique mechanical, electrical and thermal properties. However, it is challenging to uniformly distribute the large fraction of graphene fillers into a polymer matrix because graphene is not easily functionalized. We report a novel method to introduce a large fraction of graphene into a styrene-butadiene rubber (SBR) matrix. The obtained graphene/rubber nanocomposites were mechanically enhanced, acoustically absorptive under water, and electrically and thermally conductive. The Young's modulus of the nanocomposites was enhanced by over 30 times over that for rubber. The electrical conductivity of nanocomposites was ≤219 S m-1 with 15% volume fraction of graphene content, and exhibited remarkable electromagnetic shielding efficiency of 45 dB at 8-12 GHz. The thermal conductivity of the nanocomposites was ≤2.922 W m-1 k-1, which was superior to the values of thermally conductive silicone rubber thermal interface materials. Moreover, the nanocomposites exhibited excellent underwater sound absorption (average absorption coefficient >0.8 at 6-30 kHz). Notably, the absorption performance of graphene/SBR nanocomposites increased with increasing water pressure. These multifunctional graphene/SBR nanocomposites have promising applications in electronics, thermal management and marine engineering.

  19. Determination of gamma dose and thermal neutron fluence in BNCT beams from the TLD-700 glow curve shape

    Energy Technology Data Exchange (ETDEWEB)

    Gambarini, G., E-mail: grazia.gambarini@mi.infn.i [Universita degli Studi di Milano, Dipartimento di Fisica, via Celoria 16, 20133 Milano (Italy); Istituto Nazionale di Fisica Nucleare (INFN), Sezione di Milano, via Celoria 16, 20133 Milano (Italy); Bartesaghi, G. [Universita degli Studi di Milano, Dipartimento di Fisica, via Celoria 16, 20133 Milano (Italy); Istituto Nazionale di Fisica Nucleare (INFN), Sezione di Milano, via Celoria 16, 20133 Milano (Italy); Agosteo, S.; Vanossi, E. [Politecnico di Milano, Dipartimento di Energia, via Ponzio 34/3, 20133 Milano (Italy); Istituto Nazionale di Fisica Nucleare (INFN), Sezione di Milano, via Celoria 16, 20133 Milano (Italy); Carrara, M.; Borroni, M. [Fondazione IRCCS, Istituto Nazionale dei Tumori, Medical Physics Unit, via Venezian 1, 20133 Milano (Italy)

    2010-03-15

    The measurement of both gamma dose and thermal neutron fluence in a BNCT gamma-neutron mixed-field can be achieved by means of a single thermoluminescence dosimeter (TLD-700), exploiting the shape of the glow-curve (GC). The method is based on simple algorithms containing parameters obtained from the TLD-700 GC and requires the gamma calibration GC (for gamma dose measurement) or the thermal neutron calibration GC (for neutron fluence measurement) and moreover the GC of a TLD-600 exposed to a BNCT field, uncalibrated. Some results are reported, showing the potentiality of the method.

  20. Experimental determination of gamma-ray discrimination in pillar-structured thermal neutron detectors under high gamma-ray flux

    Energy Technology Data Exchange (ETDEWEB)

    Shao, Qinghui [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Conway, Adam M. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Voss, Lars F. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Radev, Radoslav P. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Nikolić, Rebecca J. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Dar, Mushtaq A. [King Saud Univ., Riyadh (Saudi Arabia); Cheung, Chin L. [Univ. of Nebraska, Lincoln, NE (United States). Dept. of Chemistry

    2015-08-04

    Silicon pillar structures filled with a neutron converter material (10B) are designed to have high thermal neutron detection efficiency with specific dimensions of 50 μm pillar height, 2 μm pillar diameter and 2 μm spacing between adjacent pillars. In this paper, we have demonstrated such a detector has a high neutron-to-gamma discrimination of 106 with a high thermal neutron detection efficiency of 39% when exposed to a high gamma-ray field of 109 photons/cm2s.

  1. Experimental determination of gamma-ray discrimination in pillar-structured thermal neutron detectors under high gamma-ray flux

    Energy Technology Data Exchange (ETDEWEB)

    Shao, Qinghui; Conway, Adam M.; Voss, Lars F.; Radev, Radoslav P. [Lawrence Livermore National Laboratory, 7000 East Ave., Livermore, CA 94550 (United States); Nikolić, Rebecca J., E-mail: nikolic1@llnl.gov [Lawrence Livermore National Laboratory, 7000 East Ave., Livermore, CA 94550 (United States); Dar, Mushtaq A. [King Saud University, Riyadh 11421 (Saudi Arabia); Cheung, Chin L. [Department of Chemistry, University of Nebraska–Lincoln, Lincoln, NE 68588 (United States)

    2015-11-01

    In this paper, we demonstrate a detector that has a high neutron-to-gamma discrimination of 8.5×10{sup 5} with a high thermal neutron detection efficiency of 39% when exposed to a high gamma-ray field of 10{sup 9} photons/cm{sup 2}s. The detector is based on a silicon pillar structure filled with a neutron converter material ({sup 10}B) designed to have high thermal neutron detection efficiency. The pillar dimensions are 50 µm pillar height, 2 µm pillar diameter and 2 µm spacing between adjacent pillars.

  2. New XMM-Newton observation of the thermally emitting isolated neutron star 2XMM J104608.7-594306

    Science.gov (United States)

    Pires, A. M.; Motch, C.; Turolla, R.; Popov, S. B.; Schwope, A. D.; Treves, A.

    2015-11-01

    Context. The isolated neutron star (INS) 2XMM J104608.7-594306 is one of the only two to be discovered through their thermal emission since the ROSAT era. Possibly a remnant of a former generation of massive stars in the Carina nebula, the exact nature of the source is unclear, and it might be unique amongst the several classes of Galactic INSs. Aims: In a first dedicated XMM-Newton observation of the source, we found intriguing evidence of a very fast spin period of P ~ 18.6 ms at the 4σ confidence level. Moreover, spectral features in absorption have also been identified. We re-observed 2XMM J104608.7-594306 with XMM-Newton to better characterise the spectral energy distribution of the source, confirm the candidate spin period, and possibly constrain the pulsar spin-down. Methods: We used the two XMM-Newton observations of 2XMM J104608.7-594306 to perform detailed timing and spectral X-ray analysis. Both the spin-down rate and the energy of the spectral features provide estimates on the neutron star magnetic field, which are crucial for investigating the evolutionary state of the neutron star. Results: Statistically acceptable spectral fits and meaningful physical parameters for the source are only obtained when the residuals at energies 0.55 keV and 1.35 keV are taken into account by the spectral modelling. While the former can result from the inhomogeneous temperature distribution on the surface of the neutron star or can be related to a local overabundance of oxygen in the Carina nebula, the one at 1.35 keV is only satisfactorily accounted for by invoking a line in absorption. In this case, the best-fit neutron star atmosphere models constrain the hydrogen column density, the effective temperature, and the luminosity of the source within NH = (2.5-3.3) × 1021 cm-2, Teff = (6-10) × 105 K, and LX = (1.1-7.4) × 1032 erg s-1. The implied distance is consistent with a location in (or in front of) the Carina nebula, and radiation radii are compatible with

  3. Microfabrication of a gadolinium-derived solid-state sensor for thermal neutrons.

    Science.gov (United States)

    Pfeifer, Kent B; Achyuthan, Komandoor E; Allen, Matthew; Denton, Michele L B; Siegal, Michael P; Manginell, Ronald P

    2017-07-01

    Neutron sensing is critical in civilian and military applications. Conventional neutron sensors are limited by size, weight, cost, portability and helium supply. Here the microfabrication of gadolinium (Gd) conversion material-based heterojunction diodes for detecting thermal neutrons using electrical signals produced by internal conversion electrons (ICEs) is described. Films with negligible stress were produced at the tensile-compressive crossover point, enabling Gd coatings of any desired thickness by controlling the radiofrequency sputtering power and using the zero-point near p(Ar) of 50 mTorr at 100 W. Post-deposition Gd oxidation-induced spallation was eliminated by growing a residual stress-free 50 nm neodymium-doped aluminum cap layer atop Gd. The resultant coatings were stable for at least 6 years, demonstrating excellent stability and product shelf-life. Depositing Gd directly on the diode surface eliminated the air gap, leading to a 200-fold increase in electron capture efficiency and facilitating monolithic microfabrication. The conversion electron spectrum was dominated by ICEs with energies of 72, 132 and 174 keV. Results are reported for neutron reflection and moderation by polyethylene for enhanced sensitivity, and γ- and X-ray elimination for improved specificity. The optimal Gd thickness was 10.4 μm for a 300 μm-thick partially depleted diode of 300 mm2 active surface area. Fast detection (within 10 min) at a neutron source-to-diode distance of 11.7 cm was achieved with this configuration. All ICE energies along with γ-ray and Kα,β X-rays were modeled to emphasize correlations between experiment and theory. Semi-conductor thermal neutron detectors offer advantages for field-sensing of radioactive neutron sources. © The Author 2017. Published by Oxford University Press on behalf of The Japan Radiation Research Society and Japanese Society for Radiation Oncology.

  4. Microfabrication of a gadolinium-derived solid-state sensor for thermal neutrons

    Science.gov (United States)

    Achyuthan, Komandoor E.; Allen, Matthew; Denton, Michele L. B.; Siegal, Michael P.; Manginell, Ronald P.

    2017-01-01

    Abstract Neutron sensing is critical in civilian and military applications. Conventional neutron sensors are limited by size, weight, cost, portability and helium supply. Here the microfabrication of gadolinium (Gd) conversion material–based heterojunction diodes for detecting thermal neutrons using electrical signals produced by internal conversion electrons (ICEs) is described. Films with negligible stress were produced at the tensile-compressive crossover point, enabling Gd coatings of any desired thickness by controlling the radiofrequency sputtering power and using the zero-point near p(Ar) of 50 mTorr at 100 W. Post-deposition Gd oxidation–induced spallation was eliminated by growing a residual stress-free 50 nm neodymium-doped aluminum cap layer atop Gd. The resultant coatings were stable for at least 6 years, demonstrating excellent stability and product shelf-life. Depositing Gd directly on the diode surface eliminated the air gap, leading to a 200-fold increase in electron capture efficiency and facilitating monolithic microfabrication. The conversion electron spectrum was dominated by ICEs with energies of 72, 132 and 174 keV. Results are reported for neutron reflection and moderation by polyethylene for enhanced sensitivity, and γ- and X-ray elimination for improved specificity. The optimal Gd thickness was 10.4 μm for a 300 μm-thick partially depleted diode of 300 mm2 active surface area. Fast detection (within 10 min) at a neutron source-to-diode distance of 11.7 cm was achieved with this configuration. All ICE energies along with γ-ray and Kα,β X-rays were modeled to emphasize correlations between experiment and theory. Semi-conductor thermal neutron detectors offer advantages for field-sensing of radioactive neutron sources. PMID:28369631

  5. Development of coupled neutronics/thermal-hydraulics test case for HPLWR

    Science.gov (United States)

    Pham, P.; Gamtsemlidze, I. D.; Bahdanovich, R. B.; Nikonov, S. P.; Smirnov, A. D.

    2017-01-01

    The High-Performance Light Water Reactor (HPLWR) is the European concept of a supercritical water reactor (SCWR) which is one of the most promising and innovative designs of the Generation IV nuclear reactor concepts. The thermal-hydraulics behavior of supercritical water is significantly different from water at sub-critical pressure because of the difference in the specific heat value. Coupled analysis of HPLWR assembly neutronics and thermal-hydraulics has become important because of the strong influence of the water density on the neutron spectrum and power distribution. Programs MCU (Monte-Carlo Universal) and ATHLET (Analysis of Thermal-hydraulics of Leaks and Transients) were used for better estimation of power and temperature distribution in HPLWR assembly.

  6. Improving Neutron Kinetics and Thermal Hydraulics coupled tools for BEPU calculations

    Energy Technology Data Exchange (ETDEWEB)

    Pericas, R.; Reventós, F.; Batet, Il.

    2015-07-01

    The BEPU methodology is capable of providing a solution in terms of increasing the nuclear power production without compromising the safety margins. This study presents different improvements performed using tools available at UPC in the field of Neutron Kinetics and Thermal Hydraulics coupled systems. The paper describes a comparison between the BEPU methodology and the Conservative Bounding methodology within the framework of the Neutron Kinetics and Thermal Hydraulics coupled systems. To perform such comparison the following tools have been selected: TRACE for thermal-hydraulic system calculations, PARCS for reactor kinetics core simulator code. A Main Steam Line Break (MSLB) in a Pressurized Water Reactor (PWR) is the selected simulated transient to show the improvements performed. (Author)

  7. Thermal insulating barrier and neutron shield providing integrated protection for a nuclear reactor vessel

    Science.gov (United States)

    Schreiber, Roger B.; Fero, Arnold H.; Sejvar, James

    1997-01-01

    The reactor vessel of a nuclear reactor installation which is suspended from the cold leg nozzles in a reactor cavity is provided with a lower thermal insulating barrier spaced from the reactor vessel to form a chamber which can be flooded with cooling water through passive valving to directly cool the reactor vessel in the event of a severe accident. The passive valving also includes bistable vents at the upper end of the thermal insulating barrier for releasing steam. A removable, modular neutron shield extending around the upper end of the reactor cavity below the nozzles forms with the upwardly and outwardly tapered transition on the outer surface of the reactor vessel, a labyrinthine channel which reduces neutron streaming while providing a passage for the escape of steam during a severe accident, and for the cooling air which is circulated along the reactor cavity walls outside the thermal insulating barrier during normal operation of the reactor.

  8. Systematic Analysis of the Effects of Mode Conversion on Thermal Radiation from Neutron Stars

    Science.gov (United States)

    Yatabe, Akihiro; Yamada, Shoichi

    2017-12-01

    In this paper, we systematically calculate the polarization in soft X-rays emitted from magnetized neutron stars, which are expected to be observed by next-generation X-ray satellites. Magnetars are one of the targets for these observations. This is because thermal radiation is normally observed in the soft X-ray band, and it is thought to be linearly polarized because of different opacities for two polarization modes of photons in the magnetized atmosphere of neutron stars and the dielectric properties of the vacuum in strong magnetic fields. In their study, Taverna et al. illustrated how strong magnetic fields influence the behavior of the polarization observables for radiation propagating in vacuo without addressing a precise, physical emission model. In this paper, we pay attention to the conversion of photon polarization modes that can occur in the presence of an atmospheric layer above the neutron star surface, computing the polarization angle and fraction and systematically changing the magnetic field strength, radii of the emission region, temperature, mass, and radii of the neutron stars. We confirmed that if plasma is present, the effects of mode conversion cannot be neglected when the magnetic field is relatively weak, B∼ {10}13 {{G}}. Our results indicate that strongly magnetized (B≳ {10}14 {{G}}) neutron stars are suitable to detect polarizations, but not-so-strongly magnetized (B∼ {10}13 {{G}}) neutron stars will be the ones to confirm the mode conversion.

  9. New applications and developments in the neutron shielding

    Science.gov (United States)

    Uğur, Fatma Aysun

    2017-09-01

    Shielding neutrons involve three steps that are slowing neutrons, absorption of neutrons, and impregnation of gamma rays. Neutrons slow down with thermal energy by hydrogen, water, paraffin, plastic. Hydrogenated materials are also very effective for the absorption of neutrons. Gamma rays are produced by neutron (radiation) retention on the neutron shield, inelastic scattering, and degradation of activation products. If a source emits gamma rays at various energies, high-energy gamma rays sometimes specify shielding requirements. Multipurpose Materials for Neutron Shields; Concrete, especially with barium mixed in, can slow and absorb the neutrons, and shield the gamma rays. Plastic with boron is also a good multipurpose shielding material. In this study; new applications and developments in the area of neutron shielding will be discussed in terms of different materials.

  10. Apparatus for nuclear transmutation and power production using an intense accelerator-generated thermal neutron flux

    Science.gov (United States)

    Bowman, C.D.

    1992-11-03

    Apparatus for nuclear transmutation and power production using an intense accelerator-generated thermal neutron flux. High thermal neutron fluxes generated from the action of a high power proton accelerator on a spallation target allows the efficient burn-up of higher actinide nuclear waste by a two-step process. Additionally, rapid burn-up of fission product waste for nuclides having small thermal neutron cross sections, and the practicality of small material inventories while achieving significant throughput derive from employment of such high fluxes. Several nuclear technology problems are addressed including 1. nuclear energy production without a waste stream requiring storage on a geological timescale, 2. the burn-up of defense and commercial nuclear waste, and 3. the production of defense nuclear material. The apparatus includes an accelerator, a target for neutron production surrounded by a blanket region for transmutation, a turbine for electric power production, and a chemical processing facility. In all applications, the accelerator power may be generated internally from fission and the waste produced thereby is transmuted internally so that waste management might not be required beyond the human lifespan.

  11. Neutronics - thermal-hydraulics coupling: application to the helium-cooled fast reactor; Couplage neutronique - thermohydraulique: application au reacteur a neutrons rapides refroidi a l'helium

    Energy Technology Data Exchange (ETDEWEB)

    Vaiana, F.

    2009-11-15

    This thesis focuses on the study of interactions between neutron-kinetics and thermal-hydraulics. Neutron-kinetics allow to calculate the power in a nuclear reactor and the temperature evolution of materials where this power is deposited is known thanks to thermal-hydraulics. Moreover, when the temperatures evolve, the densities and cross sections change. These two disciplines are thus coupled. The first part of this work corresponds to the study and development of a method which allows to simulate transients in nuclear reactors and especially with a Monte-Carlo code for neutron-kinetics. An algorithm for the resolution of the neutron transport equation has been established and validated with a benchmark. In thermal-hydraulics, a porous media approach, based on another thesis, is considered. This gives the opportunity to solve the equations on the whole core without unconscionable computation time. Finally, a theoretical study has been performed on the statistical uncertainties which result from the use of a Monte-Carlo code and which spread from the reactivity to the power and from the power to the temperatures. The second part deals with the study of a misplaced control rod withdrawing in a GFR (helium-cooled fast reactor), a fourth generation reactor. Some models allowing to calculate neutron-kinetics and thermal-hydraulics in the core (which contains assemblies built up with fuel plates) were defined. In thermal-hydraulics, a model for the core based on the porous media approach and a fuel plate homogenization model have been set up. A similar homogenization model has been studied for neutron-kinetics. Finally, the control rod withdrawing transient where we can observe the power raising and the stabilisation by thermal feedback has been performed with the Monte-Carlo code Tripoli for neutron-kinetics and the code Trio-U for thermal-hydraulics. (author)

  12. Thermal neutron capture γ-ray spectroscopy of59Ni and61Ni

    Science.gov (United States)

    Harder, A.; Michaelsen, S.; Lieb, K. P.; Williams, A. P.

    1993-06-01

    The γ-radiation emitted after thermal neutron capture in isotopically enriched58Ni and60Ni was measured at the ILL high flux reactor by means of Ge/NaI detectors operated in Compton suppression and pair spectrometer mode. The neutron binding energies were determined as B n (59Ni)=8999.15(23) keV and Bn(61Ni)=7820.07(20) keV; some 95% of the total γ-ray fluxes through59,61Ni were assigned. The γ-ray strength functions of the primary transitions and the level densities are discussed.

  13. The alanine detector in BNCT dosimetry: Dose response in thermal and epithermal neutron fields

    Energy Technology Data Exchange (ETDEWEB)

    Schmitz, T., E-mail: schmito@uni-mainz.de [Institute for nuclear chemistry, Johannes Gutenberg-University, Mainz D-55128 (Germany); Bassler, N. [Department of Physics and Astronomy, Aarhus University, Ny Munkegade 120, Aarhus C, Aarhus 8000 (Denmark); Blaickner, M. [AIT Austrian Institute of Technology GmbH, Vienna A-1220 (Austria); Ziegner, M. [AIT Austrian Institute of Technology GmbH, Vienna A-1220, Austria and TU Wien, Vienna University of Technology, Vienna A-1020 (Austria); Hsiao, M. C. [Insitute of Nuclear Engineering and Science, National Tsing Hua University, Hsinchu 30013, Taiwan (China); Liu, Y. H. [Nuclear Science and Technology Development Center, National Tsing Hua University, Hsinchu 30013, Taiwan (China); Koivunoro, H. [Department of Physics, University of Helsinki, POB 64, FI-00014, Finland and HUS Medical Imaging Center, Helsinki University Central Hospital, FI-00029 HUS (Finland); Auterinen, I.; Serén, T.; Kotiluoto, P. [VTT Technical Research Centre of Finland, Espoo (Finland); Palmans, H. [National Physical Laboratory, Acoustics and Ionising Radiation Division, Teddington TW11 0LW, United Kingdom and Medical Physics Group, EBG MedAustron GmbH, Wiener Neustadt A-2700 (Austria); Sharpe, P. [National Physical Laboratory, Acoustics and Ionising Radiation Division, Teddington TW11 0LW (United Kingdom); Langguth, P. [Department of Pharmacy and Toxicology, University of Mainz, Mainz D-55128 (Germany); Hampel, G. [Institut für Kernchemie, Johannes Gutenberg-Universität, Mainz D-55128 (Germany)

    2015-01-15

    Purpose: The response of alanine solid state dosimeters to ionizing radiation strongly depends on particle type and energy. Due to nuclear interactions, neutron fields usually also consist of secondary particles such as photons and protons of diverse energies. Various experiments have been carried out in three different neutron beams to explore the alanine dose response behavior and to validate model predictions. Additionally, application in medical neutron fields for boron neutron capture therapy is discussed. Methods: Alanine detectors have been irradiated in the thermal neutron field of the research reactor TRIGA Mainz, Germany, in five experimental conditions, generating different secondary particle spectra. Further irradiations have been made in the epithermal neutron beams at the research reactors FiR 1 in Helsinki, Finland, and Tsing Hua open pool reactor in HsinChu, Taiwan ROC. Readout has been performed with electron spin resonance spectrometry with reference to an absorbed dose standard in a {sup 60}Co gamma ray beam. Absorbed doses and dose components have been calculated using the Monte Carlo codes FLUKA and MCNP. The relative effectiveness (RE), linking absorbed dose and detector response, has been calculated using the Hansen and Olsen alanine response model. Results: The measured dose response of the alanine detector in the different experiments has been evaluated and compared to model predictions. Therefore, a relative effectiveness has been calculated for each dose component, accounting for its dependence on particle type and energy. Agreement within 5% between model and measurement has been achieved for most irradiated detectors. Significant differences have been observed in response behavior between thermal and epithermal neutron fields, especially regarding dose composition and depth dose curves. The calculated dose components could be verified with the experimental results in the different primary and secondary particle fields. Conclusions: The

  14. Cryogenic Thermal Absorptance Measurements on Small-Diameter Stainless Steel Tubing

    Science.gov (United States)

    Tuttle, James; Jahromi, Amir; Canavan, Edgar; DiPirro, Michael

    2015-01-01

    The Mid Infrared Instrument (MIRI) on the James Webb Space Telescope includes a mechanical cryocooler which cools its detectors to their 6 Kelvin operating temperature. The coolant gas flows through several meters of small-diameter stainless steel tubing, which is exposed to thermal radiation from its environment. Over much of its length this tubing is gold-plated to minimize the absorption of this radiant heat. In order to confirm that the cryocooler will meet MIRI's requirements, the thermal absorptance of this tubing was measured as a function of its environment temperature. We describe the measurement technique and present the results.

  15. Thermal neutron equivalent dose assessment around the KFUPM neutron source storage area using NTDs. King Fahd University of Petroleum and Minerals.

    Science.gov (United States)

    Abu-Jarad, F; Fazal-ur-Rehman; Al-Haddad, M N; Al-jarallah, M I

    2002-01-01

    Area passive neutron dosemeters based on nuclear track detectors (NTDs) have been used for 13 days to assess accumulated low doses of thermal neutrons around neutron source storage area of the King Fahd University of Petroleum and Minerals (KFUPM). Moreover, the aim of this study is to check the effectiveness of shielding of the storage area. NTDs were mounted with the boron converter on their surface as one compressed unit. The converter is a lithium tetraborate (Li2B4O7) layer for thermal neutron detection via 10B(n,alpha)7Li and 6Li(n,alpha)3H nuclear reactions. The area passive dosemeters were installed on 26 different locations around the source storage area and adjacent rooms. The calibration factor for NTD-based area passive neutron dosemeters was found to be 8.3 alpha tracks x cm(-2) x microSv(-1) using active snoopy neutron dosemeters in the KFUPM neutron irradiation facility. The results show the variation of accumulated dose with locations around the storage area. The range of dose rates varied from as low as 40 nSvx h(-1) up to 11 microSv x h(-1). The study indicates that the area passive neutron dosemeter was able to detect accumulated doses as low as 40 nSv x h(-1), which could not be detected with the available active neutron dosemeters. The results of the study also indicate that an additional shielding is required to bring the dose rates down to background level. The present investigation suggests extending this study to find the contribution of doses from fast neutrons around the neutron source storage area using NTDs through proton recoil. The significance of this passive technique is that it is highly sensitive and does not require any electronics or power supplies, as is the case in active systems.

  16. Using Thermal Infrared Absorption and Emission to Determine Trace Gases

    Science.gov (United States)

    Clerbaux, Cathy; Drummond, James R.; Flaud, Jean-Marie; Orphal, Johannes

    The light emerging from the top of the atmosphere in the greater part of the infrared region is thermal radiation from the Earth's surface. The resultant spectra obtained depend on the temperature difference between the emitting feature and absorbing gas. In this region the greenhouse gases, carbon dioxide, CO2, methane, CH4, ozone, O3, and water, H2O, are observed as well as carbon monoxide, CO, a product indicative of fossil fuel combustion, methanol, CH3OH, from biomass burning, and ammonia, NH3, from agriclulture. Chapter 3 describes the techniques for retrieving atmospheric abundances of these and other species from a number of satellite instruments, and concludes with suggestions for future developments.

  17. {sup 3}He spin filters for a thermal neutron triple axis spectrometer

    Energy Technology Data Exchange (ETDEWEB)

    Chen, W.C. [National Institute of Standards and Technology, Gaithersburg, MD 20899 (United States) and Indiana University, Bloomington, IN 47408 (United States)]. E-mail: cchen@nist.gov; Armstrong, G. [Hamilton College, Clinton, NY 13323 (United States); Chen, Y. [National Institute of Standards and Technology, Gaithersburg, MD 20899 (United States); University of Maryland at College Park, College Park, Maryland (United States); Collett, B. [Hamilton College, Clinton, NY 13323 (United States); Erwin, R. [National Institute of Standards and Technology, Gaithersburg, MD 20899 (United States); Gentile, T.R. [National Institute of Standards and Technology, Gaithersburg, MD 20899 (United States); Jones, G.L. [Hamilton College, Clinton, NY 13323 (United States); Lynn, J.W. [National Institute of Standards and Technology, Gaithersburg, MD 20899 (United States); McKenney, S. [National Institute of Standards and Technology, Gaithersburg, MD 20899 (United States); Steinberg, J.E. [Hamilton College, Clinton, NY 13323 (United States)

    2007-07-15

    We have tested two {sup 3}He neutron spin filters (NSF), one for the polarizer and one for the analyzer, in conjunction with a doubly focusing pyrolytic graphite (PG) monochromator on the state-of-the-art BT-7 thermal triple axis spectrometer (TAS) at the National Institute of Standards and Technology (NIST) Center for Neutron Research (NCNR). This system will provide significantly better neutronic performance for polarization analysis over a conventional TAS with Heusler crystals. We discuss the scheme for employing NSFs on the TAS instrument, including the {sup 3}He cell design, spin-exchange optical pumping (SEOP) of these large {sup 3}He cells, and the holding fields on the spectrometer. Using Rb/K hybrid SEOP, we have produced 75% {sup 3}He polarization for the 11 cm diameter cells for TAS in less than two days.

  18. Measurements of thermal neutron fluence in the bunker of a cyclotron for PET isotope production; Medidas de fluencia de neutrones termicos en el bunker de un ciclotron de produccion de isotopos para PET

    Energy Technology Data Exchange (ETDEWEB)

    Mendez Villafane, R.; Sansoloni florit, F.; Lagares gonzalez, J. L.; Llop Roig, J.; Guerrero Araque, J. E.; Muniz Gutierrez, J. L.; Perez Morales, J. M.

    2011-07-01

    To measure the neutron spectrum has been used spectrometry system based on Bonner spheres with Au flakes as thermal neutron detector at its center while the results are still pending and will be analyzing another job.

  19. A new type of thermal-neutron detector based on ZnS(Ag)/LiF scintillator and avalanche photodiodes

    Science.gov (United States)

    Marin, V. N.; Sadykov, R. A.; Trunov, D. N.; Litvin, V. S.; Aksenov, S. N.; Stolyarov, A. A.

    2015-09-01

    A high-efficiency thermal-neutron detector based on ZnS(Ag)/LiF scintillator is described, which employs a new technique of signal pick-up with the aid of a light guide and avalanche photodiodes instead of optical fibers and photomultipliers. Results of tests on the RADEX pulsed neutron source are presented, in which neutron diffraction patterns of test objects have been obtained.

  20. Absorptance measurements of transmissive optical components by the surface thermal lensing technique

    Energy Technology Data Exchange (ETDEWEB)

    Chow, R.; Taylor, J.R.; Wu, Z.L.; Han, Y.; Tian, L.Y.

    1997-09-24

    The surface thermal lensing technique (STL) successfully resolved and measured the absorptance of transmissive optical components: near- normal angle-of-incidence anti-reflectors and beam splatters. The STL system uses an Ar ion laser to pump the components at 514.5 mn. The absorptance-induced surface deformation diffracts the HeNe probe beam into a photo-detector. The signal intensity was calibrated with a sample of known absorptance. The optical components were designed to function in a copper vapor laser (CVL) transport system, and were previously tested for absorptance with a high power CVL system at 511 rtm. To assure proper absorptance data from the STL system, the pump laser power densities were set at the operational level of the coatings, absorptance time trends were monitored, and absorptance area scans were made. Both types of transmissive optics are more stable than the CVL high reflectors that were measured in another study. Parameter studies based on Fresnel diffraction theory were also performed to optimize experimental condition. The STL system was assessed to have 10 ppb sensitivity for absorption measurement given 2 W of pump power.

  1. Neutron Shielding Calculation of a Beam Stopper for the Thermal-TAS at HANARO using MCNP6

    Energy Technology Data Exchange (ETDEWEB)

    Jeon, Byoungil; Kim, Jongsoon [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2016-10-15

    It can be classified as a virtual source, neutron optics components, Monochromator Shielding Unit (MSU), Sample table and Analyzer and Detector bank. At a monochromator, specific wavelength of neutron beam is selected by the Bragg scattering theory. Because the neutron beam comes from reactor source has high intensity, massive shielding units are placed around monochromator. After monochromator, selected neutron beam goes toward sample table. This is a brief account of the Thermal-TAS experiment. To achieve high quality experimental results, signal noise should be controlled. Signal noise can come from not only electronic hardware system but also un-necessary neutron background. To reduce background, proper shielding components should be placed around optical components. Monochromator, analyzer and detector have their own shielding components but sample table doesn't in current status of Thermal-TAS. To reduce background occurred on sample table, direct neutron beam that comes from monochromator should be blocked. In this paper, basic design and radiation shielding calculation of direct beam stopper shielding component have been conducted. A conceptual design and shielding calculation of a neutron beam stopper for the thermal-TAS at HANARO has been conducted. With this result, a beam stopper segment will be fabricated. After further procedures such as mechanical, electronic design and fabrication of a driving part of the stopper, a neutron beam stopper system will be installed on the thermal-TAS at HANARO.

  2. Correlated γ rays following capture of thermal neutrons on 113Cd

    Science.gov (United States)

    Rusev, G.; Jandel, M.; Arnold, C. W.; Bredeweg, T. A.; Couture, A.; Mosby, S. M.; Ullmann, J. L.; Krtička, M.

    2013-10-01

    Natural cadmium is often used as the shielding against thermal neutrons and component in detectors sensitive to neutrons, because of the large cross section of 113Cd for capture of neutrons with energies below 1 eV. Investigation of the neutron-capture γ rays from the 113Cd (n , γ) reaction is of importance for these applications. We report the intensity distributions of these cascade γ-ray transitions. The neutron-capture experiment on 113Cd has been carried out at LANL's LANSCE using the 4 π BaF2 DANCE array. The measured two-dimensional spectrum of counts vs. γ-ray energy vs. γ-ray multiplicity from the strongest resonance in the 113Cd (n , γ) reaction at 0.178 eV has been compared with predictions from the statistical model using the code DICEBOX. Work supported by the NNSA Office of Nonproliferation and Verification Research and Development performed under the Department of Energy contract DE-AC52-06NA25396.

  3. New evaluation of thermal neutron scattering libraries for light and heavy water

    Directory of Open Access Journals (Sweden)

    Marquez Damian Jose Ignacio

    2017-01-01

    Full Text Available In order to improve the design and safety of thermal nuclear reactors and for verification of criticality safety conditions on systems with significant amount of fissile materials and water, it is necessary to perform high-precision neutron transport calculations and estimate uncertainties of the results. These calculations are based on neutron interaction data distributed in evaluated nuclear data libraries. To improve the evaluations of thermal scattering sub-libraries, we developed a set of thermal neutron scattering cross sections (scattering kernels for hydrogen bound in light water, and deuterium and oxygen bound in heavy water, in the ENDF-6 format from room temperature up to the critical temperatures of molecular liquids. The new evaluations were generated and processable with NJOY99 and also with NJOY-2012 with minor modifications (updates, and with the new version of NJOY-2016. The new TSL libraries are based on molecular dynamics simulations with GROMACS and recent experimental data, and result in an improvement of the calculation of single neutron scattering quantities. In this work, we discuss the importance of taking into account self-diffusion in liquids to accurately describe the neutron scattering at low neutron energies (quasi-elastic peak problem. To improve modeling of heavy water, it is important to take into account temperature-dependent static structure factors and apply Sköld approximation to the coherent inelastic components of the scattering matrix. The usage of the new set of scattering matrices and cross-sections improves the calculation of thermal critical systems moderated and/or reflected with light/heavy water obtained from the International Criticality Safety Benchmark Evaluation Project (ICSBEP handbook. For example, the use of the new thermal scattering library for heavy water, combined with the ROSFOND-2010 evaluation of the cross sections for deuterium, results in an improvement of the C/E ratio in 48 out of

  4. New evaluation of thermal neutron scattering libraries for light and heavy water

    Science.gov (United States)

    Marquez Damian, Jose Ignacio; Granada, Jose Rolando; Cantargi, Florencia; Roubtsov, Danila

    2017-09-01

    In order to improve the design and safety of thermal nuclear reactors and for verification of criticality safety conditions on systems with significant amount of fissile materials and water, it is necessary to perform high-precision neutron transport calculations and estimate uncertainties of the results. These calculations are based on neutron interaction data distributed in evaluated nuclear data libraries. To improve the evaluations of thermal scattering sub-libraries, we developed a set of thermal neutron scattering cross sections (scattering kernels) for hydrogen bound in light water, and deuterium and oxygen bound in heavy water, in the ENDF-6 format from room temperature up to the critical temperatures of molecular liquids. The new evaluations were generated and processable with NJOY99 and also with NJOY-2012 with minor modifications (updates), and with the new version of NJOY-2016. The new TSL libraries are based on molecular dynamics simulations with GROMACS and recent experimental data, and result in an improvement of the calculation of single neutron scattering quantities. In this work, we discuss the importance of taking into account self-diffusion in liquids to accurately describe the neutron scattering at low neutron energies (quasi-elastic peak problem). To improve modeling of heavy water, it is important to take into account temperature-dependent static structure factors and apply Sköld approximation to the coherent inelastic components of the scattering matrix. The usage of the new set of scattering matrices and cross-sections improves the calculation of thermal critical systems moderated and/or reflected with light/heavy water obtained from the International Criticality Safety Benchmark Evaluation Project (ICSBEP) handbook. For example, the use of the new thermal scattering library for heavy water, combined with the ROSFOND-2010 evaluation of the cross sections for deuterium, results in an improvement of the C/E ratio in 48 out of 65

  5. Thermal conductivity and phase separation of the crust of accreting neutron stars.

    Science.gov (United States)

    Horowitz, C J; Caballero, O L; Berry, D K

    2009-02-01

    Recently, crust cooling times have been measured for neutron stars after extended outbursts. These observations are very sensitive to the thermal conductivity kappa of the crust and strongly suggest that kappa is large. We perform molecular dynamics simulations of the structure of the crust of an accreting neutron star using a complex composition that includes many impurities. The composition comes from simulations of rapid proton capture nucleosynthesis followed by electron captures. We find that the thermal conductivity is reduced by impurity scattering. In addition, we find phase separation. Some impurities with low atomic number Z are concentrated in a subregion of the simulation volume. For our composition, the solid crust must separate into regions of different compositions. This could lead to an asymmetric star with a quadrupole deformation. Observations of crust cooling can constrain impurity concentrations.

  6. Thermal neutron detector and gamma-ray spectrometer utilizing a single material

    Science.gov (United States)

    Stowe, Ashley; Burger, Arnold; Lukosi, Eric

    2017-05-02

    A combined thermal neutron detector and gamma-ray spectrometer system, including: a detection medium including a lithium chalcopyrite crystal operable for detecting thermal neutrons in a semiconductor mode and gamma-rays in a scintillator mode; and a photodetector coupled to the detection medium also operable for detecting the gamma rays. Optionally, the detection medium includes a .sup.6LiInSe.sub.2 crystal. Optionally, the detection medium comprises a compound formed by the process of: melting a Group III element; adding a Group I element to the melted Group III element at a rate that allows the Group I and Group III elements to react thereby providing a single phase I-III compound; and adding a Group VI element to the single phase I-III compound and heating; wherein the Group I element includes lithium.

  7. Method of assaying uranium with prompt fission and thermal neutron borehole logging adjusted by borehole physical characteristics

    Science.gov (United States)

    Barnard, Ralston W.; Jensen, Dal H.

    1982-01-01

    Uranium formations are assayed by prompt fission neutron logging techniques. The uranium in the formation is proportional to the ratio of epithermal counts to thermal or eqithermal dieaway. Various calibration factors enhance the accuracy of the measurement.

  8. Method of assaying uranium with prompt fission and thermal neutron borehole logging adjusted by borehole physical characteristics. [Patient application

    Science.gov (United States)

    Barnard, R.W.; Jensen, D.H.

    1980-11-05

    Uranium formations are assayed by prompt fission neutron logging techniques. The uranium in the formation is proportional to the ratio of epithermal counts to thermal or epithermal dieaway. Various calibration factors enhance the accuracy of the measurement.

  9. Measurement of two-dimensional thermal neutron flux in a water phantom and evaluation of dose distribution characteristics

    Energy Technology Data Exchange (ETDEWEB)

    Yamamoto, Kazuyoshi; Kumada, Hiroaki; Kishi, Toshiaki; Torii, Yoshiya; Horiguchi, Yoji [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment

    2001-03-01

    To evaluate nitrogen dose, boron dose and gamma-ray dose occurred by neutron capture reaction of the hydrogen at the medical irradiation, two-dimensional distribution of the thermal neutron flux is very important because these doses are proportional to the thermal neutron distribution. This report describes the measurement of the two-dimensional thermal neutron distribution in a head water phantom by neutron beams of the JRR-4 and evaluation of the dose distribution characteristic. Thermal neutron flux in the phantom was measured by gold wire placed in the spokewise of every 30 degrees in order to avoid the interaction. Distribution of the thermal neutron flux was also calculated using two-dimensional Lagrange's interpolation program (radius, angle direction) developed this time. As a result of the analysis, it was confirmed to become distorted distribution which has annular peak at outside of the void, though improved dose profile of the deep direction was confirmed in the case which the radiation field in the phantom contains void. (author)

  10. Thermal-neutron scintillator : Ce3+ activated Rb2LiYBr6

    NARCIS (Netherlands)

    Birowosuto, M.D.; Dorenbos, P.; De Haas, J.T.M.; Van Eijk, C.W.E.; Krämer, K.W.; Güdel, H.U.

    2007-01-01

    Scintillation and luminescence characteristics of Rb2LiYBr6 doped with 0.1%, 0.5%, 1%, and 5%?Ce3+ are presented. Under optical and x-ray excitation, Ce3+ doublet emission is observed at 385 and 420 nm. Rb2LiYBr6:0.5%?Ce3+ shows very high thermal neutron scintillation light output of 83?000

  11. Neutronic and thermal-hydraulic studies of aqueous homogeneous reactor for medical isotopes production

    Energy Technology Data Exchange (ETDEWEB)

    Perez, Daniel Milian; Lorenzo, Daniel E. Milian; Lira, Carlos A. Brayner de Oliveira; Garcia, Lorena P. Rodríguez, E-mail: milianperez89@gmail.com, E-mail: dmilian@instec.cu, E-mail: lorenapilar1109@gmail.com, E-mail: cabol@ufpe.br [Higher Institute of Technologies and Applied Sciences (InSTEC), Havana (Cuba); Universidade Federal de Pernambuco (UFPE), Recife, PE (Brazil). Departamento de Energia Nuclear

    2017-11-01

    The use of Aqueous Homogenous Reactors (AHR) is one of the most promissory alternatives to produce medical isotopes, mainly {sup 99}Mo. Compare to multipurpose research reactors, an AHR dedicated for {sup 99}Mo production has advantages because of their low cost, small critical mass, inherent passive safety, and simplified fuel handling, processing, and purification characteristics. This article presents the current state of research in our working group on this topic. Are presented and discussed the group validation efforts with benchmarking exercises that include neutronic and thermal-hydraulic results of two solution reactors, the SUPO and ARGUS reactors. Neutronic and thermal-hydraulic results of 75 kWth AHR based on the ARGUS reactor LEU configuration are presented. The neutronic studies included the determination of parameters such as reflector thickness, critical height, medical isotopes production and others. Thermal-hydraulics studies were focused on demonstrating that sufficient cooling capacity exists to prevent fuel overheating. In addition, the effects of some calculation parameters on the computational modeling of temperature, velocity and gas volume fraction during steady-state operation of an AHR are discussed. The neutronic and thermal-hydraulics studies have been performed with the MCNPX version 2.6e computational code and the version 14 of ANSYS CFX respectively. Our group studies and the results obtained contribute to demonstrate the feasibility of using AHR for the production of medical isotopes, however additional studies are still necessary to confirm these results and contribute to development and demonstration of their technical, safety, and economic viability. (author)

  12. A CONCEPTUAL DESIGN OF NEUTRON COLLIMATOR IN THE THERMAL COLUMN OF KARTINI RESEARCH REACTOR FOR IN VITRO AND IN VIVO TEST OF BORON NEUTRON CAPTURE THERAPY

    Directory of Open Access Journals (Sweden)

    Nina Fauziah

    2015-03-01

    Full Text Available Studies were carried out to design a collimator which results in epithermal neutron beam for IN VITRO and IN VIVO of Boron Neutron Capture Therapy (BNCT at the Kartini research reactor by means of Monte Carlo N-Particle (MCNP codes. Reactor within 100 kW of thermal power was used as the neutron source. The design criteria were based on recommendation from the International Atomic Energy Agency (IAEA. All materials used were varied in size, according to the value of mean free path for each material. MCNP simulations indicated that by using 5 cm thick of Ni as collimator wall, 60 cm thick of Al as moderator, 15 cm thick of 60Ni as filter, 2 cm thick of Bi as γ-ray shielding, 3 cm thick of 6Li2CO3-polyethylene as beam delimiter, with 1 to 5 cm varied aperture size, epithermal neutron beam with maximum flux of 7.65 x 108 n.cm-2.s-1 could be produced. The beam has minimum fast neutron and γ-ray components of, respectively, 1.76 x 10-13 Gy.cm2.n-1 and 1.32 x 10-13 Gy.cm2.n-1, minimum thermal neutron per epithermal neutron ratio of 0.008, and maximum directionality of 0.73. It did not fully pass the IAEA’s criteria, since the epithermal neutron flux was below the recommended value, 1.0 x 109 n.cm-2.s-1. Nonetheless, it was still usable with epithermal neutron flux exceeding 5.0 x 108 n.cm-2.s-1. When it was assumed that the graphite inside the thermal column was not discharged but only the part which was going to be replaced by the collimator, the performance of the collimator became better within the positive effect from the surrounding graphite that the beam resulted passed all criteria with epithermal neutron flux up to 1.68 x 109 n.cm-2.s-1. Keywords: design, collimator, epithermal neutron beam, BNCT, MCNP, criteria   Telah dilakukan penelitian tentang desain kolimator yang menghasilkan radiasi netron epitermal untuk uji in vitro dan in vivo pada Boron Neutron Capture Therapy (BNCT di Reaktor Riset Kartini dengan menggunakan program Monte

  13. Measurement of the Slowing-Down and Thermalization Time of Neutrons in Water

    Energy Technology Data Exchange (ETDEWEB)

    Moeller, E. [AB Atomenergi, Nykoeping (Sweden); Sjoestrand, N.G. [Chalmers Univ. of Technology, Goeteborg (Sweden)

    1963-11-15

    The experimental equipment for the study of the time behaviour of neutrons during slowing-down and thermalization in a moderator by the use of a pulsed van de Graaff accelerator as a neutron source is described. Information on the change with time of the neutron spectrum is obtained from its reaction with spectrum indicators, the reaction rate being observed by the detection of capture gamma rays. The time resolution may be chosen in the range 0.01 to 5 {mu}s. Measurements have been made for water with cadmium, gadolinium and samarium as indicators dissolved in the medium. A slowing- down time to 0.2 eV of 2.7 {+-} 0.4 {mu}s and a total thermalization time of 25 - 30 {mu}s were obtained. From 9 {mu}s after the injection, the results are well described by the assumption of the flux as a Maxwell distribution cooling down to the moderator temperature with a thermalization time constant of 4.1 {+-} 0.4 {mu}s.

  14. Application of the linear extended diffusion theory in the modeling of thermal neutron flux in a plane plate; Aplicacion de la teoria de difusion lineal extendida en el modelamiento del flujo de neutrones termicos en una placa plana

    Energy Technology Data Exchange (ETDEWEB)

    Garcia B, F. B.; Arreola V, G.; Vazquez R, R.; Espinosa P, G. [Universidad Autonoma Metropolitana, Unidad Iztapalapa, Area de Ingenieria en Recursos Energeticos, Av. San Rafael Atlixco 186, Col. Vicentina, 09340 Mexico D. F. (Mexico)], e-mail: rvr@xanum.uam.mx

    2009-10-15

    In this work the thermal neutrons diffusion is studied with interfacial effects in a fuel-moderator arrangement that consist of an infinite series of plane fuel plates and of moderator willing so that each plate of multiplicative material has in each end a moderator plate. The developed pattern is an unidimensional model for the thermal group obtained of equation of volumetric diffusion average. One analysis of parametric sensibility was realized to find the correction constants for the diffusion coefficient, the absorption term and the new transfer or current term in the fuel-moderator interface. The obtained results are compared against the classic theory, being obtained a good agreement among both theories. (Author)

  15. Radiation injury of boron neutron capture therapy using mixed epithermal- and thermal neutron beams in patients with malignant glioma

    Energy Technology Data Exchange (ETDEWEB)

    Kageji, T. E-mail: kageji@clin.med.tokushima-u.ac.jp; Nagahiro, S.; Mizobuchi, Y.; Toi, H.; Nakagawa, Y.; Kumada, H

    2004-11-01

    The purpose of this study was to clarify the radiation injury in acute or delayed stage after boron neutron capture therapy (BNCT) using mixed epithermal- and thermal neutron beams in patients with malignant glioma. Eighteen patients with malignant glioma underwent mixed epithermal- and thermal neutron beam and sodium borocaptate between 1998 and 2004. The radiation dose (i.e. physical dose of boron n-alpha reaction) in the protocol used between 1998 and 2000 (Protocol A, n=8) prescribed a maximum tumor volume dose of 15 Gy. In 2001, a new dose-escalated protocol was introduced (Protocol B, n=4); it prescribes a minimum tumor volume dose of 18 Gy or, alternatively, a minimum target volume dose of 15 Gy. Since 2002, the radiation dose was reduced to 80-90% dose of Protocol B because of acute radiation injury. A new Protocol was applied to 6 glioblastoma patients (Protocol C, n=6). The average values of the maximum vascular dose of brain surface in Protocol A, B and C were 11.4{+-}4.2 Gy, 15.7{+-}1.2 and 13.9{+-}3.6 Gy, respectively. Acute radiation injury such as a generalized convulsion within 1 week after BNCT was recognized in three patients of Protocol B. Delayed radiation injury such as a neurological deterioration appeared 3-6 months after BNCT, and it was recognized in 1 patient in Protocol A, 5 patients in Protocol B. According to acute radiation injury, the maximum vascular dose was 15.8{+-}1.3 Gy in positive and was 12.6{+-}4.3 Gy in negative. There was no significant difference between them. According to the delayed radiation injury, the maximum vascular dose was 13.8{+-}3.8 Gy in positive and was 13.6{+-}4.9 Gy in negative. There was no significant difference between them. The dose escalation is limited because most patients in Protocol B suffered from acute radiation injury. We conclude that the maximum vascular dose does not exceed over 12 Gy to avoid the delayed radiation injury, especially, it should be limited under 10 Gy in the case that tumor

  16. Thermally Activated Post-glitch Response of the Neutron Star Inner Crust and Core. I. Theory

    Science.gov (United States)

    Link, Bennett

    2014-07-01

    Pinning of superfluid vortices is predicted to prevail throughout much of a neutron star. Based on the idea of Alpar et al., I develop a description of the coupling between the solid and liquid components of a neutron star through thermally activated vortex slippage, and calculate the response to a spin glitch. The treatment begins with a derivation of the vortex velocity from the vorticity equations of motion. The activation energy for vortex slippage is obtained from a detailed study of the mechanics and energetics of vortex motion. I show that the "linear creep" regime introduced by Alpar et al. and invoked in fits to post-glitch response is not realized for physically reasonable parameters, a conclusion that strongly constrains the physics of a post-glitch response through thermal activation. Moreover, a regime of "superweak pinning," crucial to the theory of Alpar et al. and its extensions, is probably precluded by thermal fluctuations. The theory given here has a robust conclusion that can be tested by observations: for a glitch in the spin rate of magnitude Δν, pinning introduces a delay in the post-glitch response time. The delay time is td = 7(t sd/104 yr)((Δν/ν)/10-6) d, where t sd is the spin-down age; td is typically weeks for the Vela pulsar and months in older pulsars, and is independent of the details of vortex pinning. Post-glitch response through thermal activation cannot occur more quickly than this timescale. Quicker components of post-glitch response, as have been observed in some pulsars, notably, the Vela pulsar, cannot be due to thermally activated vortex motion but must represent a different process, such as drag on vortices in regions where there is no pinning. I also derive the mutual friction force for a pinned superfluid at finite temperature for use in other studies of neutron star hydrodynamics.

  17. On the Influence of the Sample Absorptivity when Studying the Thermal Degradation of Materials

    Directory of Open Access Journals (Sweden)

    Pascal Boulet

    2015-08-01

    Full Text Available The change in absorptivity during the degradation process of materials is discussed, and its influence as one of the involved parameters in the degradation models is studied. Three materials with very different behaviors are used for the demonstration of its role: a carbon composite material, which is opaque, almost grey, a plywood slab, which is opaque and spectral-dependent and a clear PMMA slab, which is semitransparent. Data are analyzed for virgin and degraded materials at different steps of thermal degradation. It is seen that absorptivity and emissivity often reach high values in the range of 0.90–0.95 with a near-grey behavior after significant thermal aggression, but depending on the materials of interest, some significant evolution may be first observed, especially during the early stages of the degradation. Supplementary inaccuracy can come from the heterogeneity of the incident flux on the slab. As a whole, discrepancies up to 20% can be observed on the absorbed flux depending on the degradation time, mainly because of the spectral variations of the absorption and up to 10% more, depending on the position on the slab. Simple models with a constant and unique value of absorptivity may then lead to inaccuracies in the evaluation of the radiative flux absorption, with possible consequences on the pyrolysis analysis, especially for properties related to the early step of the degradation process, like the time to ignition, for example.

  18. On the Influence of the Sample Absorptivity when Studying the Thermal Degradation of Materials.

    Science.gov (United States)

    Boulet, Pascal; Brissinger, Damien; Collin, Anthony; Acem, Zoubir; Parent, Gilles

    2015-08-21

    The change in absorptivity during the degradation process of materials is discussed, and its influence as one of the involved parameters in the degradation models is studied. Three materials with very different behaviors are used for the demonstration of its role: a carbon composite material, which is opaque, almost grey, a plywood slab, which is opaque and spectral-dependent and a clear PMMA slab, which is semitransparent. Data are analyzed for virgin and degraded materials at different steps of thermal degradation. It is seen that absorptivity and emissivity often reach high values in the range of 0.90-0.95 with a near-grey behavior after significant thermal aggression, but depending on the materials of interest, some significant evolution may be first observed, especially during the early stages of the degradation. Supplementary inaccuracy can come from the heterogeneity of the incident flux on the slab. As a whole, discrepancies up to 20% can be observed on the absorbed flux depending on the degradation time, mainly because of the spectral variations of the absorption and up to 10% more, depending on the position on the slab. Simple models with a constant and unique value of absorptivity may then lead to inaccuracies in the evaluation of the radiative flux absorption, with possible consequences on the pyrolysis analysis, especially for properties related to the early step of the degradation process, like the time to ignition, for example.

  19. Methods for absorbing neutrons

    Science.gov (United States)

    Guillen, Donna P [Idaho Falls, ID; Longhurst, Glen R [Idaho Falls, ID; Porter, Douglas L [Idaho Falls, ID; Parry, James R [Idaho Falls, ID

    2012-07-24

    A conduction cooled neutron absorber may include a metal matrix composite that comprises a metal having a thermal neutron cross-section of at least about 50 barns and a metal having a thermal conductivity of at least about 1 W/cmK. Apparatus for providing a neutron flux having a high fast-to-thermal neutron ratio may include a source of neutrons that produces fast neutrons and thermal neutrons. A neutron absorber positioned adjacent the neutron source absorbs at least some of the thermal neutrons so that a region adjacent the neutron absorber has a fast-to-thermal neutron ratio of at least about 15. A coolant in thermal contact with the neutron absorber removes heat from the neutron absorber.

  20. Diaryl-substituted norbornadienes with red-shifted absorption for molecular solar thermal energy storage.

    Science.gov (United States)

    Gray, Victor; Lennartson, Anders; Ratanalert, Phasin; Börjesson, Karl; Moth-Poulsen, Kasper

    2014-05-25

    Red-shifting the absorption of norbornadienes (NBDs), into the visible region, enables the photo-isomerization of NBDs to quadricyclanes (QCs) to be driven by sunlight. This is necessary in order to utilize the NBD-QC system for molecular solar thermal (MOST) energy storage. Reported here is a study on five diaryl-substituted norbornadienes. The introduced aryl-groups induce a significant red-shift of the UV/vis absorption spectrum of the norbornadienes, and device experiments using a solar-simulator set-up demonstrate the potential use of these compounds for MOST energy storage.

  1. Consistent neutron-physical and thermal-physical calculations of fuel rods of VVER type reactors

    Directory of Open Access Journals (Sweden)

    Tikhomirov Georgy

    2017-01-01

    Full Text Available For modeling the isotopic composition of fuel, and maximum temperatures at different moments of time, one can use different algorithms and codes. In connection with the development of new types of fuel assemblies and progress in computer technology, the task makes important to increase accuracy in modeling of the above characteristics of fuel assemblies during the operation. Calculations of neutronphysical characteristics of fuel rods are mainly based on models using averaged temperature, thermal conductivity factors, and heat power density. In this paper, complex approach is presented, based on modern algorithms, methods and codes to solve separate tasks of thermal conductivity, neutron transport, and nuclide transformation kinetics. It allows to perform neutron-physical and thermal-physical calculation of the reactor with detailed temperature distribution, with account of temperature-depending thermal conductivity and other characteristics. It was applied to studies of fuel cell of the VVER-1000 reactor. When developing new algorithms and programs, which should improve the accuracy of modeling the isotopic composition and maximum temperature in the fuel rod, it is necessary to have a set of test tasks for verification. The proposed approach can be used for development of such verification base for testing calculation of fuel rods of VVER type reactors

  2. Benchmarking a first-principles thermal neutron scattering law for water ice with a diffusion experiment

    Science.gov (United States)

    Holmes, Jesse; Zerkle, Michael; Heinrichs, David

    2017-09-01

    The neutron scattering properties of water ice are of interest to the nuclear criticality safety community for the transport and storage of nuclear materials in cold environments. The common hexagonal phase ice Ih has locally ordered, but globally disordered, H2O molecular orientations. A 96-molecule supercell is modeled using the VASP ab initio density functional theory code and PHONON lattice dynamics code to calculate the phonon vibrational spectra of H and O in ice Ih. These spectra are supplied to the LEAPR module of the NJOY2012 nuclear data processing code to generate thermal neutron scattering laws for H and O in ice Ih in the incoherent approximation. The predicted vibrational spectra are optimized to be representative of the globally averaged ice Ih structure by comparing theoretically calculated and experimentally measured total cross sections and inelastic neutron scattering spectra. The resulting scattering kernel is then supplied to the MC21 Monte Carlo transport code to calculate time eigenvalues for the fundamental mode decay in ice cylinders at various temperatures. Results are compared to experimental flux decay measurements for a pulsed-neutron die-away diffusion benchmark.

  3. Thermal-hydraulic simulation of mercury target concepts for a pulsed spallation neutron source

    Energy Technology Data Exchange (ETDEWEB)

    Siman-Tov, M.; Wendel, M.; Haines, J. [Oak Ridge National Lab., TN (United States)

    1996-06-01

    The Oak Ridge Spallation Neutron Source (ORSNS) is a high-power, accelerator-based pulsed spallation neutron source being designed by a multi-laboratory team led by Oak Ridge National Laboratory to achieve very high fluxes of neutrons for scientific experiments. The ORSNS is projected to have a 1 MW proton beam upgradable to 5 MW. About 60% of the beam power (1-5 MW, 17-83 kJ/pulse in 0.5 microsec at 60 cps) is deposited in the liquid metal (mercury) target having the dimensions of 65x30x10 cm (about 19.5 liter). Peak steady state power density is about 150 and 785 MW/m{sup 3} for 1 MW and 5 MW beam respectively, whereas peak pulsed power density is as high as 5.2 and 26.1 GW/m{sup 3}, respectively. The peak pulse temperature rise rate is 14 million C/s (for 5 MW beam) whereas the total pulse temperature rise is only 7 C. In addition to thermal shock and materials compatibility, key feasibility issues for the target are related to its thermal-hydraulic performance. This includes proper flow distribution, flow reversals, possible {open_quotes}hot spots{close_quotes} and the challenge of mitigating the effects of thermal shock through possible injection of helium bubbles throughout the mercury volume or other concepts. The general computational fluid dynamics (CFD) code CFDS-FLOW3D was used to simulate the thermal and flow distribution in three preliminary concepts of the mercury target. Very initial CFD simulation of He bubbles injection demonstrates some potential for simulating behavior of He bubbles in flowing mercury. Much study and development will be required to be able to `predict`, even in a crude way, such a complex phenomena. Future direction in both design and R&D is outlined.

  4. ITHNA.SYS: An Integrated Thermal Hydraulic and Neutronic Analyzer SYStem for NUR research reactor

    Energy Technology Data Exchange (ETDEWEB)

    Mazidi, S., E-mail: samirmazidi@gmail.com [Division Physique et Applications Nucléaires, Centre de Recherche Nucléaire de Draria (CRND), BP 43 Sebala, Draria, Alger (Algeria); Meftah, B., E-mail: b_meftah@yahoo.com [Division Physique et Applications Nucléaires, Centre de Recherche Nucléaire de Draria (CRND), BP 43 Sebala, Draria, Alger (Algeria); Belgaid, M., E-mail: belgaidm@yahoo.com [Faculté de Physique, Université Houari Boumediene, USTHB, BP 31, Bab Ezzouar, Alger (Algeria); Letaim, F., E-mail: fletaim@yahoo.fr [Faculté des Sciences et Technologies, Université d’El-oued, PO Box 789, El-oued (Algeria); Halilou, A., E-mail: hal_rane@yahoo.fr [Division Réacteur NUR, Centre de Recherche Nucléaire de Draria, BP 43 Sebala, Draria, Alger (Algeria)

    2015-08-15

    Highlights: • We develop a neutronic and thermal hydraulic MTR reactor analyzer. • The analyzer allows a rapid determination of the reactor core parameters. • Some NUR reactor parameters have been analyzed. - Abstract: This paper introduces the Integrated Thermal Hydraulic and Neutronic Analyzer SYStem (ITHNA.SYS) that has been developed for the Algerian research reactor NUR. It is used both as an operating aid tool and as a core physics engineering analysis tool. The system embeds three modules of the MTR-PC software package developed by INVAP SE: the cell calculation code WIMSD, the core calculation code CITVAP and the program TERMIC for thermal hydraulic analysis of a material testing reactor (MTR) core in forced convection. ITHNA.SYS operates both in on-line and off-line modes. In the on-line mode, the system is linked, via the computer parallel port, to the data acquisition console of the reactor control room and allows a real time monitoring of major physical and safety parameters of the NUR core. PC-based ITHNA.SYS provides a viable and convenient way of using an accumulated and often complex reactor physics stock of knowledge and frees the user from the intricacy of adequate reactor core modeling. This guaranties an accurate, though rapid, determination of a variety of neutronic and thermal hydraulic parameters of importance for the operation and safety analysis of the NUR research reactor. Instead of the several hours usually required, the processing time for the determination of such parameters is now reduced to few seconds. Validation of the system was performed with respect to experimental measurements and to calculations using reference codes. ITHNA.SYS can be easily adapted to accommodate other kinds of MTR reactors.

  5. Thermal changes in the absorption spectra of blood with supravascular infrared laser irradiation in vivo

    Science.gov (United States)

    Zalesskaya, G. A.; Astaf'eva, L. G.; Batai, L. E.

    2011-09-01

    We have studied the effect of laser radiation (λ = 1960 nm, power density from 6 to 25 W/cm2) on the absorption spectra of rat blood with supravascular irradiation. We have established that absorption of laser radiation leads to a decrease in the degree of oxygen saturation of mixed venous blood due to its heating. We have estimated the initial heating temperatures of venous blood and the surface of the irradiated tissue using an optothermal model, taking into account the characteristics of the laser radiation and the optical and thermal characteristics of the biological tissue. We consider the effect of radiation-induced thermal dissociation of oxyhemoglobin on the oxygen transport characteristics of the blood and metabolic processes.

  6. Use of thermal neutron reflection method for chemical analysis of bulk samples

    Energy Technology Data Exchange (ETDEWEB)

    Papp, A., E-mail: papppa@atomki.hu [Institute of Nuclear Research of the Hungarian Academy of Sciences, (ATOMKI), 4001 Debrecen, Pf. 51 (Hungary); Csikai, J. [Institute of Nuclear Research of the Hungarian Academy of Sciences, (ATOMKI), 4001 Debrecen, Pf. 51 (Hungary); Institute of Experimental Physics, University Debrecen (IEP), 4010 Debrecen-10, Pf. 105 (Hungary)

    2014-09-11

    Microscopic, σ{sub β}, and macroscopic, Σ{sub β}, reflection cross-sections of thermal neutrons averaged over bulk samples as a function of thickness (z) are given. The σ{sub β} values are additive even for bulk samples in the z=0.5–8 cm interval and so the σ{sub βmol}(z) function could be given for hydrogenous substances, including some illicit drugs, explosives and hiding materials of ∼1000 cm{sup 3} dimensions. The calculated excess counts agree with the measured R(z) values. For the identification of concealed objects and chemical analysis of bulky samples, different neutron methods need to be used simultaneously. - Highlights: • Check the proposed analytical expression for the description of the flux. • Determination of the reflection cross-sections averaged over bulk samples. • Data rendered to estimate the excess counts for various materials.

  7. Thermal Neutron Detection by Entrapping 6LiF Nanodiamonds in Siloxane Scintillators

    Science.gov (United States)

    Degerlier, M.; Carturan, S.; Marchi, T.; Dalla Palma, M.; Gramegna, F.; Maggioni, G.; Cinausero, M.; Quaranta, A.

    Exploiting the long experience in design and production of scintillating mixtures based on siloxane matrices with combinations of primary dye and waveshifter, a first set of 6LiF loaded scintillator disks have been produced and the involved steps for their preparation are herein described. Preliminary results as for their light response towards thermal neutrons are reported as well. The preservation of transparency and mechanical integrity of the scintillator material is challenging when introducing the inorganic salt LiF, which is a "foreign body" to the organic polysiloxane host matrix. Different strategies such as synthesis of nanoparticles and surface functionalization have been pursued to succeed in the entrapment of the neutron converter whilst maintaining moderate light output, optical clarity and flexibility of the base scintillator.

  8. Thermal neutron detection by entrapping 6LiF nanocrystals in siloxane scintillators

    Science.gov (United States)

    Carturan, S. M.; Marchi, T.; Maggioni, G.; Gramegna, F.; Degerlier, M.; Cinausero, M.; Dalla Palma, M.; Quaranta, A.

    2015-06-01

    Exploiting the long experience in design and production of scintillating mixtures based on siloxane matrices with combinations of primary dye and waveshifter, a first set of 6LiF loaded scintillator disks has been produced. The synthesis is herein described and reported, as well as preliminary results on their light response towards thermal neutrons. The preservation of transparency and mechanical integrity of the scintillator material is challenging when introducing the inorganic salt LiF which is a "foreign body" to the organic polysiloxane host matrix Different strategies such as synthesis of nanoparticles and surface functionalization have been pursued to succeed in the entrapment of the neutron converter whilst maintaining moderate light output, optical transparency and flexibility of the base scintillator.

  9. Position sensitive detection of thermal neutrons with solid state detectors (Gd Si planar detectors)

    CERN Document Server

    Bruckner, G; Rauch, H; Weilhammer, P

    1999-01-01

    Recent advances in the technology of position sensitive silicon detectors and the corresponding electronics allow the construction of fast time response thermal neutron detectors. These detectors also exhibit excellent position resolution by combination of silicon detectors with thin Gd converter foils. We constructed several one- and two-dimensional prototype detectors, using DC and AC coupled silicon strip detectors, pad detectors and different VLSI readout electronics. The position resolution and the detector efficiency for different converters at wavelengths from 1.1 to 3.3 A were determined at the TRIGA reactor in Vienna and at the ILL in Grenoble. Spatial resolutions of less than 100 mu m and efficiencies up to 40% have been achieved. The results of these measurements are compared with a Monte Carlo simulation of the detector operation. These detectors can also be used for phase topography experiments using perfect crystal neutron interferometers. In certain cases an increase of the sensitivity in the o...

  10. 10B enriched plastic scintillators for application in thermal neutron detection

    Science.gov (United States)

    Mahl, Adam; Yemam, Henok A.; Fernando, Roshan; Koubek, Joshua T.; Sellinger, Alan; Greife, Uwe

    2018-02-01

    We report here on the synthesis and characterization of a novel 10B enriched aromatic molecule that can be incorporated into common poly(vinyltoluene) (PVT) based plastic scintillators to achieve enhanced thermal neutron detection. Starting from relatively inexpensive 10B enriched boric acid, we have prepared 4,4,5,5-tetramethyl-2-phenyl-1,3,2-dioxaborolane (MBB) in three high yield steps. MBB is soluble and compatible with PVT based formulations and results in stable plastic scintillators. Chemical synthesis, solubility limit in PVT, and the physical properties of the dopant were explored. The relevant response properties of the resulting scintillators when exposed to neutron and gamma radiation, including light yield and pulse shape discrimination properties were measured and analyzed.

  11. A LiBr-H2O Absorption Refrigerator Incorporating a Thermally Activated Solution Pumping Mechanism

    OpenAIRE

    Ian W. Eames

    2017-01-01

    This paper provides an illustrated description of a proposed LiBr-H2O vapour absorption refrigerator which uses a thermally activated solution pumping mechanism that combines controlled variations in generator vapour pressure with changes it produces in static-head pressure difference to circulate the absorbent solution between the generator and absorber vessels. The proposed system is different and potentially more efficient than a bubble pump system previously proposed and avoids the need f...

  12. Iron interference in arsenic absorption by different plant species, analysed by neutron activation, k{sub 0}-method

    Energy Technology Data Exchange (ETDEWEB)

    Uemura, George; Matos, Ludmila Vieira da Silva; Silva, Maria Aparecida da; Menezes, Maria Angela de Barros Correia [Centro de Desenvolvimento da Tecnologia Nuclear (CDTN-CNEN/MG), Belo Horizonte, MG (Brazil)], e-mail: george@cdtn.br, e-mail: menezes@cdtn.br

    2009-07-01

    Natural arsenic contamination is a cause for concern in many countries of the world including Argentina, Bangladesh, Chile, China, India, Mexico, Thailand, United States of America and also in Brazil, specially in the Iron Quadrangle area, where mining activities have been contributing to aggravate natural contamination. Among other elements, iron is capable to interfere with the arsenic absorption by plants; iron ore has been proposed to remediate areas contaminated by the mentioned metalloid. In order to verify if iron can interfere with arsenic absorption by different taxa of plants, specimens of Brassicacea and Equisetaceae were kept in a 1/4 Murashige and Skoog basal salt solution (M and S), with 10 {mu}gL{sup -1} of arsenic acid. And varying concentrations of iron. The specimens were analysed by neutron activation analysis, k{sub 0}-method, a routine technique in CDTN, and also very appropriate for arsenic studies. The preliminary results were quite surprising, showing that iron can interfere with arsenic absorption by plants, but in different ways, according to the species studied. (author)

  13. The influence of low dose neutron irradiation on the thermal conductivity of Allcomp carbon foam

    Energy Technology Data Exchange (ETDEWEB)

    Burchell, Timothy D. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Porter, Wallace D. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); McDuffee, Joel Lee [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

    2016-03-01

    Oak Ridge National Laboratory was contracted via a Work for Others Agreement with Allcomp Inc. (NFE-14-05011-MSOF: Carbon Foam for Beam Stop Applications ) to determine the influence of low irradiation dose on the thermal conductivity of Allcomp Carbon Foam. Samples (6 mm dia. x 5 mm thick) were successfully irradiated in a rabbit capsule in a hydraulic tube in the target region of the High Flux Isotope Reactor at the Oak Ridge National Laboratory. The specimens were irradiated at Tirr = 747.5 C to a neutron damage dose of 0.2 dpa. There is a small dimensional and volume shrinkage and the mass and density appear reduced (we would expect density to increase as volume reduces at constant mass). The small changes in density, dimensions or volume are not of concern. At 0.2 dpa the irradiation shrinkage rate difference between the glassy carbon skeleton and the CVD coating was not sufficient to cause a large enough irradiation-induced strain to create any mechanical degradation. Similarly differential thermal expansion was not a problem. It appears that only the thermal conductivity was affected by 0.2 dpa. For the intended application conditions, i.e. @ 400 C and 0 DPA (start- up) the foam thermal conductivity is about 57 W/m.K and at 700 C and 0.2 DPA (end of life) the foam thermal conductivity is approx. 30.7 W/m.K. The room temp thermal conductivity drops from 100-120 W/m.K to approximately 30 W/m.K after 0.2 dpa of neutron irradiation.

  14. On the Thermal Conductivity Change of Matrix Graphite Materials after Neutron Irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Young-Woo; Yeo, Seunghwan; Kim, Eung-Seon; Sah, Injin; Park, Daegyu; Kim, Youngjun; Cho, Moon Sung [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2016-10-15

    In this work, the variations of the thermal conductivity of the A3-3 matrix graphite after neutron irradiation is discussed as well as of the IG-110 graphite for comparison. Neutron irradiation of the graphite specimens was carried out as a part of the first irradiation test of KAERI's coated particle fuel specimens by use of Hanaro research reactor. This work can be summarized as follows: 1) In the evaluation of the specific heat of the graphite materials, various literature data were used and the variations of the specific heat data of all the graphite specimens are observed well agreed, irrespectively of the difference in specimens (graphite and matrix graphite and irradiated and un-irradiated). 2) This implies that it should be reasonable that for both structural graphite and fuel matrix graphite, and even for the neuron-irradiated graphite, any of these specific heat data set be used in the calculation of the thermal conductivity. 3) For the irradiated A3-3 matrix graphite specimens, the thermal conductivity decreased on both directions. On the radial direction, the tendency of variation upon temperature is similar to that of unirradiated specimen, i.e., decreasing as the temperature increases. 4) In the German irradiation experiments with A3-27 matrix graphite specimens, the thermal conductivity of the un-irradiated specimen shows a decrease and that of irradiated specimen is nearly constant as the temperature increases. 5) The thermal conductivity of the irradiated IG-110 was considerably decreased compared with that of un-irradiated specimens The difference of the thermal conductivity of un-irradiated and irradiated IG-110 graphite specimens is much larger than that of un-irradiated and irradiated A3-3 matrix graphite specimens.

  15. Measurement of Insulation Compaction in the Cryogenic Fuel Tanks at Kennedy Space Center by Fast/Thermal Neutron Techniques

    Science.gov (United States)

    Livingston, R. A.; Schweitzer, J. S.; Parsons, Ann M.; Arens, Ellen E.

    2010-01-01

    The liquid hydrogen and oxygen cryogenic storage tanks at John F. Kennedy Space Center (KSC) use expanded perlite as thermal insulation. Th ere is evidence that some of the perlite has compacted over time, com promising the thermal performance and possibly also structural integr ity of the tanks. Therefore an Non-destructive Testing (NDT) method for measuring the perlite density or void fraction is urgently needed. Methods based on neutrons are good candidates because they can readil y penetrate through the 1.75 cm outer steel shell and through the ent ire 120 cm thickness of the perlite zone. Neutrons interact with the nuclei of materials to produce characteristic gamma rays which are the n detected. The gamma ray signal strength is proportional to the atom ic number density. Consequently, if the perlite is compacted then the count rates in the individual peaks in the gamma ray spectrum will i ncrease. Perlite is a feldspathic volcanic rock made up of the major elements Si, AI, Na, K and 0 along with some water. With commercially available portable neutron generators it is possible to produce simul taneously fluxes of neutrons in two energy ranges: fast (14 MeV) and thermal (25 meV). Fast neutrons produce gamma rays by inelastic scatt ering which is sensitive to Fe and O. Thermal neutrons produce gamma rays by radiative capture in prompt gamma neutron activation (PGNA) and this is sensitive to Si, AI, Na, Kand H. Thus the two energy ranges produce complementary information. The R&D program has three phases: numerical simulations of neutron and gamma ray transport with MCNP s oftware, evaluation of the system in the laboratory on test articles and finally mapping of the perlite density in the cryogenic tanks at KSC. The preliminary MCNP calculations have shown that the fast/therma l neutron NDT method is capable of distinguishing between expanded an d compacted perlite with excellent statistics.

  16. Neutronic and thermal-hydraulic analysis of fission molybdenum-99 production at Tehran Research Reactor using LEU plate targets.

    Science.gov (United States)

    Abedi, Ebrahim; Ebrahimkhani, Marzieh; Davari, Amin; Mirvakili, Seyed Mohammad; Tabasi, Mohsen; Maragheh, Mohammad Ghannadi

    2016-12-01

    Efficient and safe production of molybdenum-99 ( 99 Mo) radiopharmaceutical at Tehran Research Reactor (TRR) via fission of LEU targets is studied. Neutronic calculations are performed to evaluate produced 99 Mo activity, core neutronic safety parameters and also the power deposition values in target plates during a 7 days irradiation interval. Thermal-hydraulic analysis has been also carried out to obtain thermal behavior of these plates. Using Thermal-hydraulic analysis, it can be concluded that the safety parameters are satisfied in the current study. Consequently, the present neutronic and thermal-hydraulic calculations show efficient 99 Mo production is accessible at significant activity values in TRR current core configuration. Copyright © 2016 Elsevier Ltd. All rights reserved.

  17. Neutron-pair emission following pi /sup -/ absorption on some light nuclei

    CERN Document Server

    Furic, M; Engelhardt, H D; Klotz, W D; Takeutchi, F; Ullrich, H

    1977-01-01

    Large-area position-sensitive neutron counters with subnanosecond time resolution have been used to study the ( pi /sup -/,2n) reaction with a resolution comparable to or better than the existing ( pi /sup + /,2p) data. The measurement of the momenta of both neutrons enabled a determination of the excitation energy spectra of the residual nuclei to be made. The momentum distributions for the absorbing nucleon pair were also extracted assuming the quasifree mechanism for the ( pi /sup -/,2n) process. The pi /sup -/ beam obtained from the CERN SC II was brought to rest in the targets of /sup 9/Be, /sup 10/B, /sup 12/C and /sup 14/N. The excitation spectra of the residual nuclei were compared with the predictions based on the coefficients of fractional parentage for the removal of the two nucleons. The data and the predictions are in good agreement within the experimental resolution. (4 refs).

  18. Dancoff factors of unit cells in cluster geometry with partial absorption of neutrons; Fatores de Dancoff de celulas unitarias em geometria cluster com absorcao parcial de neutrons

    Energy Technology Data Exchange (ETDEWEB)

    Rodrigues, Leticia Jenisch

    2011-01-15

    In its classical formulation, the Dancoff factor for a perfectly absorbing fuel rod is defined as the relative reduction in the incurrent of resonance neutrons into the rod in the presence of neighboring rods, as compared to the incurrent into a single fuel rod immersed in an infinite moderator. Alternatively, this factor can be viewed as the probability that a neutron emerging from the surface of a fuel rod will enter another fuel rod without any collision in the moderator or cladding. For perfectly absorbing fuel these definitions are equivalent. In the last years, several works appeared in literature reporting improvements in the calculation of Dancoff factors, using both the classical and the collision probability definitions. In this work, we step further reporting Dancoff factors for perfectly absorbing (Black) and partially absorbing (Grey) fuel rods calculated by the collision probability method, in cluster cells with square outer boundaries. In order to validate the results, comparisons are made with the equivalent cylindricalized cell in hypothetical test cases. The calculation is performed considering specularly reflecting boundary conditions, for the square lattice, and diffusive reflecting boundary conditions, for the cylindrical geometry. The results show the expected asymptotic behavior of the solution with increasing cell sizes. In addition, Dancoff factors are computed for the Canadian cells CANDU-37 and CANFLEX by the Monte Carlo and Direct methods. Finally, the effective multiplication factors, k{sub eff}, for these cells (cluster cell with square outer boundaries and the equivalent cylindricalized cell) are also computed, and the differences reported for the cases using the perfect and partial absorption assumptions. (author)

  19. Whole core pin-by-pin coupled neutronic-thermal-hydraulic steady state and transient calculations using COBAYA3 code

    Energy Technology Data Exchange (ETDEWEB)

    Jimenez, J.; Herrero, J. J.; Cuervo, D.; Aragones, J. M., E-mail: jimenez@din.upm.e [Universidad Politecnica de Madrid, Departamento de Ingenieria Nuclear, Jose Gutierrez Abascal No. 2, 28006 Madrid (Spain)

    2010-10-15

    Nowadays coupled 3-dimensional neutron kinetics and thermal-hydraulic core calculations are performed by applying a radial average channel approach using a meshing of one quarter of assembly in the best case. This approach does not take into account the subchannels effects due to the averaging of the physical fields and the loose of heterogeneity in the thermal-hydraulic model. Therefore the models do not have enough resolution to predict those subchannels effects which are important for the fuel design safety margins, because it is in the local scale, where we can search the hottest pellet or the maximum heat flux. The Polytechnic University of Madrid advanced multi-scale neutron-kinetics and thermal-hydraulics methodologies being implemented in COBAYA3 include domain decomposition by alternate core dissections for the local 3-dimensional fine-mesh scale problems (pin cells/subchannels) and an analytical nodal diffusion solver for the coarse mesh scale coupled with the thermal-hydraulic using a model of one channel per assembly or per quarter of assembly. In this work, we address the domain decomposition by the alternate core dissections methodology applied to solve coupled 3-dimensional neutronic-thermal-hydraulic problems at the fine-mesh scale. The neutronic-thermal-hydraulic coupling at the cell-subchannel scale allows the treatment of the effects of the detailed thermal-hydraulic feedbacks on cross-sections, thus resulting in better estimates of the local safety margins at the pin level. (Author)

  20. Application of radiochemical neutron activation and atomic absorption spectrometry methods for the study of nutrition-pollution interactions in children

    Energy Technology Data Exchange (ETDEWEB)

    Tran Bang Diep [Institute for Nuclear Science and Technique, VAEC, P.O. Box 5T-160, Hanoi (Viet Nam)]. E-mail: tranfbangdiepj@yahoo.com; Tran Dai Nghiep [Institute for Nuclear Science and Technique, VAEC, P.O. Box 5T-160, Hanoi (Viet Nam)]. E-mail: tdnghiep@vaec.gov.vn

    2005-07-01

    The application of radiochemical neutron activation analysis (RNAA) and atomic absorption spectrometry (AAS) is expected to aid in understanding and evaluating the effects of environmental pollution on the nutritional status of children already exposed to marginal malnutrition. Samples of placenta, of low-weight and control newborns groups, were collected for determination of nutritional elements and pollutants. The mean ratios of pollutants and nutrients such as Cd/Zn, Hg/Se and Pb/Ca were evaluated for both groups. All these ratios in the placenta of the low-weight newborns are higher than that of the healthy group. The degree of the nutrient-pollutant interaction is evaluated by quantity R, with mercury considered as the most active pollutant while calcium the most active nutrient among the involved elements in process of the interaction. (author)

  1. Coupled neutronic and thermal-hydraulic code benchmark activities at the International Nuclear Safety Center.

    Energy Technology Data Exchange (ETDEWEB)

    Podlazov, L. N.

    1998-07-29

    Two realistic benchmark problems are defined and used to assess the performance of coupled thermal-hydraulic and neutronic codes used in simulating dynamic processes in VVER-1000 and RBMK reactor systems. One of the problems simulates a design basis accident involving the ejection of three control and protection system rods from a VVER-1000 reactor. The other is based on a postulated rod withdrawal from an operating RBMK reactor. Preliminary results calculated by various codes are compared. While these results show significant differences, the intercomparisons performed so far provide a basis for further evaluation of code limitations and modeling assumptions.

  2. Basic performance of a pressurized backgammon-type position-sensitive proportional counter for thermal neutrons

    Energy Technology Data Exchange (ETDEWEB)

    Horiguchi, T.; Itoh, T.; Ito, S. E-mail: shinito@msa.kindai.ac.jp; Yamamoto, T.; Miyasaka, T.; Sakai, J.; Shibata, K.; Masuda, Y.; Okumura, A.; Niwa, T

    2004-08-21

    A position-sensitive proportional counter with the backgammon position-reading method has been developed for thermal neutron detection. The use of a thin solid layer of {sup 10}B and a high-pressure counting gas of 6-atm Ar+10%CH{sub 4} has enabled us to obtain the position resolution well below 1.0 mm. Moreover, it was clearly revealed that the deterioration and/or the splitting of position-peak structure, observed in some conditions, originated in the strong correlational behavior between position information and avalanche size. It is explained qualitatively that this phenomenon is caused by the effect of self-induced space charge.

  3. Total Absorption Gamma-Ray Spectroscopy of 87Br, 88Br and 94Rb Beta-Delayed Neutron Emitters

    CERN Document Server

    Valencia, E; Algora, A; Agramunt, J; Rubio, B; Rice, S; Gelletly, W; Regan, P; Zakari-Issoufou, A -A; Fallot, M; Porta, A; Rissanen, J; Eronen, T; Aysto, J; Batist, L; Bowry, M; Bui, V M; Caballero-Folch, R; Cano-Ott, D; Elomaa, V -V; Estevez, E; Farrelly, G F; Garcia, A R; Gomez-Hornillos, B; Gorlychev, V; Hakala, J; Jordan, M D; Jokinen, A; Kolhinen, V S; Kondev, F G; Martinez, T; Mendoza, E; Moore, I; Penttila, H; Podolyak, Zs; Reponen, M; Sonnenschein, V; Sonzogni, A A

    2016-01-01

    We investigate the decay of 87Br, 88Br and 94Rb using total absorption gamma-ray spectroscopy. These important fission products are beta-delayed neutron emitters. Our data show considerable gamma-intensity, so far unobserved in high-resolution gamma-ray spectroscopy, from states at high excitation energy. We also find significant differences with the beta intensity that can be deduced from existing measurements of the beta spectrum. We evaluate the impact of the present data on reactor decay heat using summation calculations. Although the effect is relatively small it helps to reduce the discrepancy between calculations and integral measurements of the photon component for 235U fission at cooling times in the range 1 to 100 s. We also use summation calculations to evaluate the impact of present data on reactor antineutrino spectra. We find a significant effect at antineutrino energies in the range of 5 to 9 MeV. In addition, we observe an unexpected strong probability for gamma emission from neutron unbound s...

  4. Thermal neutron cross-section and resonance integral of the 152Sm(n,γ)153Sm reaction induced by pulsed neutrons

    Science.gov (United States)

    Van Do, Nguyen; Khue, Pham Duc; Thanh, Kim Tien; Hien, Nguyen Thi; Kim, Guinyun; Kim, Kwangsoo; Shin, Sung-Gyun; Kye, Yong-Uk; Cho, Moo-Hyun

    2017-10-01

    We measured the thermal neutron cross-section (σ0) and resonance integral (I0) of the 152Sm(n,γ)153Sm reaction relative to that of the 197Au(n,γ)198Au reaction. Sm and Au foils with and without a cadmium cover of 0.5 mm were irradiated with moderated pulsed neutrons produced from the electron linac. The induced activities of the reaction products were determined via high energy resolution HPGe detector. The present results: σ0,Sm =212±8 b and I0,Sm =3.02±0.19 kb are consistent with most of the existing reference data.

  5. Measurement of thermal neutron cross section for {sup 241}Am(n,f) reaction

    Energy Technology Data Exchange (ETDEWEB)

    Kobayashi, Katsuhei; Yamamoto, Shuji; Fujita, Yoshiaki [Kyoto Univ., Kumatori, Osaka (Japan). Research Reactor Inst.; Miyoshi, Mitsuharu; Kimura, Itsuro; Kanno, Ikuo; Shinohara, Nobuo

    1997-03-01

    Making use of a standard neutron spectrum field with a pure Maxwellian distribution, the thermal neutron cross section for the {sup 241}Am(n,f) reaction has been measured relative to the reference value of 586.2b for the {sup 235U}(n,f) reaction. For the present measurement, electrodeposited layers of {sup 241}Am and {sup 235}U have been employed as back-to-back type double fission chambers. The present result at neutron energy of 0.0253 eV is 3.15 {+-} 0.097b. The ENDF/B-VI data is in good agreement with the present value, while the JENDL-3.2 data is lower by 4.2%. The evaluated data in JEF-2.2 and by Mughabghab are higher by 0.9% and 1.6%, respectively than the present result. The ratios of the earlier experimental data to the present value are distributed between 0.89 and 1.02. (author)

  6. Computed tomography with thermal neutrons and gaseous position sensitive detector; Tomografia computadorizada com neutrons termicos e detetor a gas sensivel a posicao

    Energy Technology Data Exchange (ETDEWEB)

    Souza, Maria Ines Silvani

    2001-12-01

    A third generation tomographic system using a parallel thermal neutron beam and gaseous position sensitive detector has been developed along three discrete phases. At the first one, X-ray tomographic images of several objects, using a position sensitive detector designed and constructed for this purpose have been obtained. The second phase involved the conversion of that detector for thermal neutron detection, by using materials capable to convert neutrons into detectable charged particles, testing afterwards its performance in a tomographic system by evaluation the quality of the image arising from several test-objects containing materials applicable in the engineering field. High enriched {sup 3} He, replacing the argon-methane otherwise used as filling gas for the X-ray detection, as well as, a gadolinium foil, have been utilized as converters. Besides the pure enriched {sup 3} He, its mixture with argon-methane and later on with propane, have been also tested, in order to evaluate the detector efficiency and resolution. After each gas change, the overall performance of the tomographic system using the modified detector, has been analyzed through measurements of the related parameters. This was done by analyzing the images produced by test-objects containing several materials having well known attenuation coefficients for both thermal neutrons and X-rays. In order to compare the performance of the position sensitive detector as modified to detect thermal neutrons, with that of a conventional BF{sub 3} detector, additional tomographs have been conducted using the last one. The results have been compared in terms of advantages, handicaps and complementary aspects for different kinds of radiation and materials. (author)

  7. 3D neutronic codes coupled with thermal-hydraulic system codes for PWR, and BWR and VVER reactors

    Energy Technology Data Exchange (ETDEWEB)

    Langenbuch, S.; Velkov, K. [GRS, Garching (Germany); Lizorkin, M. [Kurchatov-Institute, Moscow (Russian Federation)] [and others

    1997-07-01

    This paper describes the objectives of code development for coupling 3D neutronics codes with thermal-hydraulic system codes. The present status of coupling ATHLET with three 3D neutronics codes for VVER- and LWR-reactors is presented. After describing the basic features of the 3D neutronic codes BIPR-8 from Kurchatov-Institute, DYN3D from Research Center Rossendorf and QUABOX/CUBBOX from GRS, first applications of coupled codes for different transient and accident scenarios are presented. The need of further investigations is discussed.

  8. Constraints on Thermal X-Ray Radiation from SAX J1808.4-3658 and Implications for Neutron Star Neutrino Emission

    NARCIS (Netherlands)

    Heinke, C.O.; Jonker, P.G.; Wijnands, R.; Taam, R.E.

    2007-01-01

    Thermal X-ray radiation from neutron star soft X-ray transients in quiescence provides the strongest constraints on the cooling rates of neutron stars and thus on the interior composition and properties of matter in the cores of neutron stars. We analyze new (2006) and archival (2001) XMM-Newton

  9. Thermal-hydraulic design concept of the solid-target system of spallation neutron source

    Energy Technology Data Exchange (ETDEWEB)

    Tanaka, F.; Hibiki, T.; Saito, Y.; Takeda, T.; Mishima, K. [Kyoto Univ., Research Reactor Institute (Japan)

    2001-07-01

    In relation to thermal-hydraulic design of the N-Arena solid-target system of the JHF project, heat transfer experiments were performed to obtain experimental data systematically on heat transfer coefficient and CHF for vertical upward and horizontal flows in a thin rectangular channel simulating a coolant channel of the proposed spallation neutron source. Thermal-hydraulic correlations which can be used for design calculations were proposed based on the obtained data. Finally tentative results of feasibility study on maximum beam power which could be attained with a solid target were presented. The result indicated that the condition for the onset of nucleate boiling is the most significant limiting factor to the maximum beam power. (author)

  10. Measurement of the thermal and fast neutron flux in a research reactor with a Li and Th loaded optical fibre detector

    CERN Document Server

    Yamane, Y; Misawa, T; Karlsson, J K H; Pázsit, I

    1999-01-01

    The spatial dependence of thermal and fast neutron flux was measured axially in the core of a 1 MW research reactor. The measurements were made by a thin optical fibre detector with a neutron sensitive ZnS(Ag) scintillation tip. For thermal neutrons sup 6 Li was used, whereas for fast neutrons sup 2 sup 3 sup 2 Th was used as neutron converter. The spatial dependence was measured by moving the fibre axially with a uniform speed. The measurement takes a few minutes, compared to up to 10 h with the conventional wire activation method. Comparison with traditional measurements shows a good agreement. (author)

  11. Measurement of the thermal and fast neutron flux in a research reactor with a Li and Th loaded optical fibre detector

    Science.gov (United States)

    Yamane, Y.; Uritani, A.; Misawa, T.; Karlsson, J. K.-H. J. K.-H.; Pázsit, I.

    1999-08-01

    The spatial dependence of thermal and fast neutron flux was measured axially in the core of a 1 MW research reactor. The measurements were made by a thin optical fibre detector with a neutron sensitive ZnS(Ag) scintillation tip. For thermal neutrons 6Li was used, whereas for fast neutrons 232Th was used as neutron converter. The spatial dependence was measured by moving the fibre axially with a uniform speed. The measurement takes a few minutes, compared to up to 10 h with the conventional wire activation method. Comparison with traditional measurements shows a good agreement.

  12. Coupled neutronic-thermal-hydraulics analysis in a coolant subchannel of a PWR using CFD techniques

    Energy Technology Data Exchange (ETDEWEB)

    Ribeiro, Felipe P.; Su, Jian, E-mail: sujian@nuclear.ufrj.br [Coordenacao de Pos-Graduacao e Pesquisa de Engenharia (COPPE/UFRJ), Rio de Janeiro, RJ (Brazil). Programa de Engenharia Nuclear

    2017-07-01

    The high capacity of Computational Fluid Dynamics code to predict multi-dimensional thermal-hydraulics behaviour and the increased availability of capable computer systems are making that method a good tool to simulate phenomena of thermal-hydraulics nature in nuclear reactors. However, since there are no neutron kinetics models available in commercial CFD codes to the present day, the application of CFD in the nuclear reactor safety analyses is still limited. The present work proposes the implementation of the point kinetics model (PKM) in ANSYS - Fluent to predict the neutronic behaviour in a Westinghouse Sequoyah nuclear reactor, coupling with the phenomena of heat conduction in the rod and thermal-hydraulics in the cooling fluid, via the reactivity feedback. Firstly, a mesh convergence and turbulence model study was performed, using the Reynolds-Average Navier-Stokes method, with square arrayed rod bundle featuring pitch to diameter ratio of 1:32. Secondly, simulations using the k-! SST turbulence model were performed with an axial distribution of the power generation in the fuel to analyse the heat transfer through the gap and cladding, and its in fluence on the thermal-hydraulics behaviour of the cooling fluid. The wall shear stress distribution for the centre-line rods and the dimensionless velocity were evaluated to validate the model, as well as the in fluence of the mass flow rate variation on the friction factor. The coupled model enabled to perform a dynamic analysis of the nuclear reactor during events of insertion of reactivity and shutdown of primary coolant pumps. (author)

  13. UCN sources at external beams of thermal neutrons. An example of PIK reactor

    Energy Technology Data Exchange (ETDEWEB)

    Lychagin, E.V., E-mail: lychag@nf.jinr.ru [Joint Institute for Nuclear Research, 6 Joliot-Curie, Dubna 141980 (Russian Federation); Mityukhlyaev, V.A., E-mail: victim@pnpi.spb.ru [Petersburg Nuclear Physics Institute, Orlova Roscha, Gatchina 188300 (Russian Federation); Muzychka, A.Yu., E-mail: muz@nf.jinr.ru [Joint Institute for Nuclear Research, 6 Joliot-Curie, Dubna 141980 (Russian Federation); Nekhaev, G.V., E-mail: grigorijnekhaev@yandex.ru [Joint Institute for Nuclear Research, 6 Joliot-Curie, Dubna 141980 (Russian Federation); Nesvizhevsky, V.V., E-mail: nesvizhevsky@ill.eu [Institut Max von Laue – Paul Langevin, 71 Avenue des Martyrs, Grenoble 38042 (France); Onegin, M.S., E-mail: oneginm@gmail.com [Petersburg Nuclear Physics Institute, Orlova Roscha, Gatchina 188300 (Russian Federation); Sharapov, E.I., E-mail: sharapov@nf.jinr.ru [Joint Institute for Nuclear Research, 6 Joliot-Curie, Dubna 141980 (Russian Federation); Strelkov, A.V., E-mail: str@jinr.ru [Joint Institute for Nuclear Research, 6 Joliot-Curie, Dubna 141980 (Russian Federation)

    2016-07-01

    We consider ultracold neutron (UCN) sources based on a new method of UCN production in superfluid helium ({sup 4}He). The PIK reactor is chosen as a perspective example of application of this idea, which consists of installing {sup 4}He UCN source in the beam of thermal or cold neutrons and surrounding the source with moderator-reflector, which plays the role of cold neutron (CN) source feeding the UCN source. CN flux in the source can be several times larger than the incident flux, due to multiple neutron reflections from the moderator–reflector. We show that such a source at the PIK reactor would provide an order of magnitude larger density and production rate than an analogous source at the ILL reactor. We estimate parameters of {sup 4}He source with solid methane (CH{sub 4}) or/and liquid deuterium (D{sub 2}) moderator–reflector. We show that such a source with CH{sub 4} moderator–reflector at the PIK reactor would provide the UCN density of ~1·10{sup 5} cm{sup −3}, and the UCN production rate of ~2·10{sup 7} s{sup −1}. These values are respectively 1000 and 20 times larger than those for the most intense UCN user source. The UCN density in a source with D{sub 2} moderator-reflector would reach the value of ~2·10{sup 5} cm{sup −3}, and the UCN production rate would be equal ~8·10{sup 7} s{sup −1}. Installation of such a source in a beam of CNs would slightly increase the density and production rate.

  14. Reduced contribution of thermally-labile sugar lesions to DNA double-strand break formation after exposure to neutrons.

    Science.gov (United States)

    Singh, Satyendra K; Wu, Wenqi; Stuschke, Martin; Bockisch, Andreas; Iliakis, George

    2012-12-01

    In cells exposed to ionizing radiation, double-strand breaks (DSBs) form within clustered damage sites from lesions disrupting the DNA sugar-phosphate backbone. It is commonly assumed that DSBs form promptly and are immediately detected and processed by the cellular DNA damage response apparatus. However, DSBs also form by delayed chemical conversion of thermally-labile sugar lesions (TLSL) to breaks. We recently reported that conversion of thermally-labile sugar lesions to breaks occurs in cells maintained at physiological temperatures. Here, we investigate the influence of radiation quality on the formation of thermally-labile sugar lesions dependent DSBs. We show that, although the yields of total DSBs are very similar after exposure to neutrons and X rays, the yields of thermally-labile sugar lesions dependent DSBs from neutrons are decreased in comparison to that from X rays. Thus, the yields of prompt DSBs for neutrons are greater than for X rays. Notably, after neutron irradiation the decreased yield of thermally-labile sugar lesion dependent DSBs is strongly cell line dependent, likely reflecting subtle differences in DNA organization. We propose that the higher ionization density of neutrons generates with higher probability prompt DSBs within ionization clusters and renders the ensuing chemical evolution of thermally-labile sugar lesions inconsequential to DNA integrity. Modification of thermally-labile sugar lesion evolution may define novel radiation protection strategies aiming at decreasing DSB formation by chemically preserving thermally-labile sugar lesions until other DSB contributing lesions within the clustered damage site are removed by non-DSB repair pathways.

  15. Neutronic and Thermal-hydraulic Modelling of High Performance Light Water Reactor

    Energy Technology Data Exchange (ETDEWEB)

    Seppaelae, Malla [VTT Technical Research Centre of Finland, P.O.Box 1000, FI02044 VTT (Finland)

    2008-07-01

    High Performance Light Water Reactor (HPLWR), which is studied in EU project 'HPLWR2', uses water at supercritical pressures as coolant and moderator to achieve higher core outlet temperature and thus higher efficiency compared to present reactors. At VTT Technical Research Centre of Finland, functionality of the thermal-hydraulics in the coupled reactor dynamics code TRAB3D/ SMABRE was extended to supercritical pressures for the analyses of HPLWR. Input models for neutronics and thermal-hydraulics were made for TRAB3D/ SMABRE according to the latest HPLWR design. A preliminary analysis was performed in which the capability of SMABRE in the transition from supercritical pressures to subcritical pressures was demonstrated. Parameterized two-group cross sections for TRAB3D neutronics were received from Hungarian Academy of Sciences KFKI Atomic Energy Research Institute together with a subroutine for handling them. PSG, a new Monte Carlo transport code developed at VTT, was also used to generate two-group constants for HPLWR and comparisons were made with the KFKI cross sections and MCNP calculations. (author)

  16. Development of an integrated thermal-hydraulics capability incorporating RELAP5 and PANTHER neutronics code

    Energy Technology Data Exchange (ETDEWEB)

    Page, R.; Jones, J.R.

    1997-07-01

    Ensuring that safety analysis needs are met in the future is likely to lead to the development of new codes and the further development of existing codes. It is therefore advantageous to define standards for data interfaces and to develop software interfacing techniques which can readily accommodate changes when they are made. Defining interface standards is beneficial but is necessarily restricted in application if future requirements are not known in detail. Code interfacing methods are of particular relevance with the move towards automatic grid frequency response operation where the integration of plant dynamic, core follow and fault study calculation tools is considered advantageous. This paper describes the background and features of a new code TALINK (Transient Analysis code LINKage program) used to provide a flexible interface to link the RELAP5 thermal hydraulics code with the PANTHER neutron kinetics and the SIBDYM whole plant dynamic modelling codes used by Nuclear Electric. The complete package enables the codes to be executed in parallel and provides an integrated whole plant thermal-hydraulics and neutron kinetics model. In addition the paper discusses the capabilities and pedigree of the component codes used to form the integrated transient analysis package and the details of the calculation of a postulated Sizewell `B` Loss of offsite power fault transient.

  17. A neutron scattering study on the stability of trehalose mycolates under thermal stress

    Energy Technology Data Exchange (ETDEWEB)

    Migliardo, F., E-mail: fmigliardo@unime.it [Department of Physics, University of Messina, Viale D’Alcontres 31, 98166 Messina (Italy); Salmeron, C.; Bayan, N. [Laboratoire de Microbiologie Moléculaire et Cellulaire, IBBMC, Bat 430, Université de Paris Sud XI, 15 rue Georges Clémenceau, 91405 Orsay Cedex (France)

    2013-10-16

    Highlights: ► Neutron scattering measurements have been performed on mycolate water mixtures. ► A comparison with lecithin lipid water mixtures has been carried out. ► Mycolates show a lower mobility and flexibility compared to lecithin. ► The observed peculiarities of mycolic acids could be ascribed to trehalose. ► The results could justify the high resistance to thermal stress of mycobacteria. - Abstract: The present paper is focused on the study of the dynamics of mycolic acids, which are fundamental components of the outer membrane (mycomembrane) of Mycobacterium tuberculosis. An elastic neutron scattering study of mycolic acid/H{sub 2}O and lecithin/H{sub 2}O mixtures as a function of temperature and exchanged wavevector Q has been carried out. This study provides an effective way for characterizing the dynamical properties, furnishing a set of parameters characterizing the different flexibility and rigidity of the investigated lipids. The behavior of the elastically scattered intensity profiles and the derived mean square displacements as a function of temperature shows a more marked temperature dependence for lecithin lipids in comparison with mycolic acids, so revealing a higher thermal stability of these latter. These findings could be useful for understanding the dynamics-function relation in the mycomembrane and then to relate it to the low permeability and high resistance of mycobacteria to many antibiotics.

  18. Properties of the lithium carbonate for to be used as thermal neutrons detector; Propiedades del carbonato de litio para ser usado como detector de neutrones termicos

    Energy Technology Data Exchange (ETDEWEB)

    Herrera A, E.; Urena N, F. [ININ, 52045 Ocoyoacac, Estado de Mexico (Mexico)

    2003-07-01

    In this work the dosimetric properties of the lithium carbonate used as detecting of thermal neutrons and by means of free radicals is evaluated and presented. The studied parameters that were carried out for this detector were: intensity of the Electron paramagnetic resonance signal (EPR); reproducibility, fading of the signal to ambient temperature, stability of the signal to low temperature (0 degrees); answer of zero dose and homogeneity or reliability of the data of the detector, humidity, solar light, temperature and radio sensitivity. These parameters indicate the utility that have the detectors for the estimation of fields of neutron fluences that are applicable to capture therapies by neutron-boron and, nuclear reactors. (Author)

  19. Theoretical Simulation of 87Rb Absorption Spectrum in a Thermal Cell

    CERN Document Server

    Cheng, Hong; Xin, Pei-Pei; Yuan, Cheng; Liu, Hong-Ping

    2016-01-01

    In this paper, we present a theoretical simulation of 87Rb absorption spectrum in a thermal cm-cell which is adaptive to the experimental observation. In experiment, the coupling and probe beams are configured to copropagate but perpendicular polarized, making up to five velocity selective optical pumping (VSOP) absorption dips able to be identified. A $\\Lambda$-type electromagnetically induced transparency (EIT) is also observed for each group of velocity-selected atoms. The spectrum by only sweeping the probe beam can be decomposed into a combination of Doppler-broadened background and three VSOP dips for each group of velocity-selected atoms, companied by an EIT peak. This proposed theoretical model can be used to simulate the spectrum adaptive to the experimental observation by non-linear least-square fit method. The fit for high quality of experimental observation can determine valuable transition parameters such as decaying rates and coupling beam power accurately.

  20. Coupled neutronics and thermal hydraulics of high density cores for FRM II

    Energy Technology Data Exchange (ETDEWEB)

    Breitkreutz, Harald

    2011-03-04

    According to the 'Verwaltungsvereinbarung zwischen Bund und Land vom 30.5.2003' and its updating on 13.11.2010, the Forschungs-Neutronenquelle Heinz Maier-Leibnitz, Frm II, has to convert its fuel element to an uranium enrichment which is significantly lower than the current 93%, in case this is economically reasonable and doesn't impact the reactor performance immoderate. In the framework of this conversion, new calculations regarding neutronics and thermal hydraulics for the anticipated core configurations have to be made. The computational power available nowadays allows for detailed 3D calculations, on the neutronic as well as on the thermal hydraulic side. In this context, a new program system, 'X{sup 2}', was developed. It couples the Monte Carlo code McnpX, the computational fluid dynamics code Cfx and the burn-up code sequence MonteBurns. The codes were modified and extended to meet the requirements of the coupled calculation concept. To verify the new program system, highly detailed calculations for the current fuel element were made and compared to simulations and measurements that were performed in the past. The results strengthen the works performed so far and show that the original, conservative approach overestimates all critical thermal hydraulic values. Using the CFD software, effects like the impact of the combs that fix the fuel plates and the pressure drop at the edges of the fuel plates were studied in great detail for the first time. Afterwards, a number of possible new fuel elements with lower enrichment, based on disperse and monolithic UMo (uranium with 8 wt.-% Mo) were analysed. A number of straight-forward conversion scenarios was discussed, showing that a further compaction of the fuel element, an extended cycle length or an increased reactor power is needed to compensate the flux loss, which is caused by the lower enrichment. This flux loss is in excess of 7%. The discussed new fuel elements include a 50

  1. Proceedings of the OECD/CSNI workshop on transient thermal-hydraulic and neutronic codes requirements

    Energy Technology Data Exchange (ETDEWEB)

    Ebert, D.

    1997-07-01

    This is a report on the CSNI Workshop on Transient Thermal-Hydraulic and Neutronic Codes Requirements held at Annapolis, Maryland, USA November 5-8, 1996. This experts` meeting consisted of 140 participants from 21 countries; 65 invited papers were presented. The meeting was divided into five areas: (1) current and prospective plans of thermal hydraulic codes development; (2) current and anticipated uses of thermal-hydraulic codes; (3) advances in modeling of thermal-hydraulic phenomena and associated additional experimental needs; (4) numerical methods in multi-phase flows; and (5) programming language, code architectures and user interfaces. The workshop consensus identified the following important action items to be addressed by the international community in order to maintain and improve the calculational capability: (a) preserve current code expertise and institutional memory, (b) preserve the ability to use the existing investment in plant transient analysis codes, (c) maintain essential experimental capabilities, (d) develop advanced measurement capabilities to support future code validation work, (e) integrate existing analytical capabilities so as to improve performance and reduce operating costs, (f) exploit the proven advances in code architecture, numerics, graphical user interfaces, and modularization in order to improve code performance and scrutibility, and (g) more effectively utilize user experience in modifying and improving the codes.

  2. EFFECTS OF IRRADIATION ON THERMAL CONDUCTIVITY OF ALLOY 690 AT LOW NEUTRON FLUENCE

    Directory of Open Access Journals (Sweden)

    WOO SEOG RYU

    2013-04-01

    Full Text Available Alloy 690 has been selected as a steam generator tubing material for SMART owing to a near immunity to primary water stress corrosion cracking. The steam generators of SMART are faced with a neutron flux due to the integrated arrangement inside a reactor vessel, and thus it is important to know the irradiation effects of the thermal conductivity of Alloy 690. Alloy 690 was irradiated at HANARO to fluences of (0.7−28 × 1019n/cm2 (E>0.1MeV at 250°C, and its thermal conductivity was measured using the laser-flash equipment in the IMEF. The thermal conductivity of Alloy 690 was dependent on temperature, and it was a good fit to the Smith-Palmer equation, which modified the Wiedemann-Franz law. The irradiation at 250°C did not degrade the thermal conductivity of Alloy 690, and even showed a small increase (1% at fluences of (0.7∼28 × 1019n/cm2 (E>0.1MeV.

  3. Thermal-hydraulically corrected neutron cross-sections for PWR reactors

    Energy Technology Data Exchange (ETDEWEB)

    Santiago, Daniela M.N.; Alvim, Antonio C.M.; Silva, Fernando C., E-mail: dsantiago@con.ufrj.b, E-mail: alvim@con.ufrj.b, E-mail: fernando@con.ufrj.b [Universidade Federal do Rio de Janeiro (PEN/COPPE/UFRJ), RJ (Brazil). Coordenacao dos Programas de Pos-Graduacao de Engenharia. Programa de Engenharia Nuclear

    2011-07-01

    Reactor core simulation codes ought to have a thermal-hydraulics feedback module. This module calculates, among other effects, the fuel temperature thermal-hydraulics feedback, that corrects neutron cross sections. In the nodal code developed at PEN/COPPE/UFRJ, the fuel temperature is obtained through an empirical model. This work presents a physical model to calculate this temperature. A finite volume technique was used to discretize the equation for temperature distribution, while the moderator coefficient of heat transfer was calculated using ASME routines, appended to the developed code. This model allows calculation of an average radial temperature per node, since the thermal-hydraulic feedback must follow the conditions imposed by the nodal code. The results obtained were compared with the ones obtained by the empirical model. The results show that, for fuel elements near core periphery, the empirical model overestimates the temperature in the fuel, as compared to our model, which may indicate that the physical model is more appropriate to calculate the thermal-hydraulic feedback temperatures. (author)

  4. Some features and results of thermal neutron background measurements with the [ZnS(Ag)+6LiF] scintillation detector

    Science.gov (United States)

    Kuzminov, V. V.; Alekseenko, V. V.; Barabanov, I. R.; Etezov, R. A.; Gangapshev, A. M.; Gavrilyuk, Yu. M.; Gezhaev, A. M.; Kazalov, V. V.; Khokonov, A. Kh.; Panasenko, S. I.; Ratkevich, S. S.

    2017-01-01

    Features of a thermal neutron test detector with thin scintillator [ZnS(Ag)+6LiF] are described. Background of the detector and its registration efficiency were defined as a result of measurements. The thermal neutron flux at different locations, and for different conditions around the Baksan Neutrino Observatory are reported.

  5. Effect of drying method on mechanical, thermal and water absorption properties of enzymatically crosslinked gelatin hydrogels

    Directory of Open Access Journals (Sweden)

    RAYSSA C. SIMONI

    Full Text Available ABSTRACT Enzymatically crossliked gelatin hydrogel was submitted to two different drying methods: air drying and freeze drying. The resulting polymeric tridimensional arrangement (compact or porous, respectively led to different thermal and swelling properties. Significant differences (p < 0.05 on thermal and mechanical characteristics as well as swelling in non-enzymatic gastric and intestinal simulated fluids (37 ºC were detected. Water absorption data in such media was modelled according to Higuchi, Korsmeyer-Peppas, and Peppas-Sahlin equations. Freeze dried hydrogel showed Fickian diffusion behavior while air dried hydrogels presented poor adjustment to Higuchi model suggesting the importance of the relaxation mechanism at the beginning of swelling process. It was possible to conclude that the same gelatin hydrogel may be suitable to different applications depending on the drying process used.

  6. Validation of coupled neutronic / thermal-hydraulic codes for VVER reactors. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Mittag, S.; Grundmann, U.; Kliem, S.; Kozmenkov, Y.; Rindelhardt, U.; Rohde, U.; Weiss, F.-P.; Langenbuch, S.; Krzykacz-Hausmann, B.; Schmidt, K.-D.; Vanttola, T.; Haemaelaeinen, A.; Kaloinen, E.; Kereszturi, A.; Hegyi, G.; Panka, I.; Hadek, J.; Strmensky, C.; Darilek, P.; Petkov, P.; Stefanova, S.; Kuchin, A.; Khalimonchuk, V.; Hlbocky, P.; Sico, D.; Danilin, S.; Ionov, V.; Nikonov, S.; Powney, D.

    2004-08-01

    In recent years, the simulation methods for the safety analysis of nuclear power plants have been continuously improved to perform realistic calculations. Therefore in VALCO work package 2 (WP 2), the usual application of coupled neutron-kinetic / thermal-hydraulic codes to VVER has been supplemented by systematic uncertainty and sensitivity analyses. A comprehensive uncertainty analysis has been carried out. The GRS uncertainty and sensitivity method based on the statistical code package SUSA was applied to the two transients studied earlier in SRR-1/95: A load drop of one turbo-generator in Loviisa-1 (VVER-440), and a switch-off of one feed water pump in Balakovo-4 (VVER-1000). The main steps of these analyses and the results obtained by applying different coupled code systems (SMABRE - HEXTRAN, ATHLET - DYN3D, ATHLET - KIKO3D, ATHLET - BIPR-8) are described in this report. The application of this method is only based on variations of input parameter values. No internal code adjustments are needed. An essential result of the analysis using the GRS SUSA methodology is the identification of the input parameters, such as the secondary-circuit pressure, the control-assembly position (as a function of time), and the control-assembly efficiency, that most sensitively affect safety-relevant output parameters, like reactor power, coolant heat-up, and primary pressure. Uncertainty bands for these output parameters have been derived. The variation of potentially uncertain input parameter values as a consequence of uncertain knowledge can activate system actions causing quite different transient evolutions. This gives indications about possible plant conditions that might be reached from the initiating event assuming only small disturbances. In this way, the uncertainty and sensitivity analysis reveals the spectrum of possible transient evolutions. Deviations of SRR-1/95 coupled code calculations from measurements also led to the objective to separate neutron kinetics from

  7. Accumulation of GdCl3 in the feed of a reverse osmosis system during desalination as determined by neutron absorption

    Science.gov (United States)

    Schwahn, D.; Pipich, V.; Kasher, R.; Oren, Y.

    2016-09-01

    This article deals with the application of in-situ small-angle neutron scattering to investigate wastewater desalination by reverse osmosis. In a first series of experiments we take advantage of the strong neutron absorption of gadolinium (Gd) and use 0.50 g/L GdCl3 in the feed as an indicator for concentration polarization and scaling at the membrane surface. The continuous decline of scattering during the process of desalination indicates an increase of GdCl3 salt concentration which after 15 hours has achieved nearly 100% enhancement with respect to its initial concentration.

  8. Production of a faithful realistic phantom to human head and thermal neutron flux measurement on the brain surface. Cooperative research

    CERN Document Server

    Yamamoto, K; Kishi, T; Kumada, H; Matsumura, A; Nose, T; Torii, Y; Uchiyama, J; Yamamoto, T

    2002-01-01

    Thermal neutron flux is determined using the gold wires in current BNCT irradiation, so evaluation of arbitrary points after the irradiation is limited in the quantity of these detectors. In order to make up for the weakness, dose estimation of a patient is simulated by a computational dose calculation supporting system. In another way without computer simulation, a medical irradiation condition can be replicate experimentally using of realistic phantom which was produced from CT images by rapid prototyping technique. This phantom was irradiated at a same JRR-4 neutron beam as clinical irradiation condition of the patient and the thermal neutron distribution on the brain surface was measured in detail. This experimental evaluation technique using a realistic phantom is applicable to in vitro cell irradiation experiments for radiation biological effects as well as in-phantom experiments for dosimetry under the nearly medical irradiation condition of patient.

  9. Production of a faithful realistic phantom to human head and thermal neutron flux measurement on the brain surface. Cooperative research

    Energy Technology Data Exchange (ETDEWEB)

    Yamamoto, Kazuyoshi; Kumada, Hiroaki; Kishi, Toshiaki; Torii, Yoshiya; Uchiyama, Junzo [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment; Endo, Kiyoshi; Yamamoto, Tetsuya; Matsumura, Akira; Nose, Tadao [Tsukuba Univ., Tsukuba, Ibaraki (Japan)

    2002-12-01

    Thermal neutron flux is determined using the gold wires in current BNCT irradiation, so evaluation of arbitrary points after the irradiation is limited in the quantity of these detectors. In order to make up for the weakness, dose estimation of a patient is simulated by a computational dose calculation supporting system. In another way without computer simulation, a medical irradiation condition can be replicate experimentally using of realistic phantom which was produced from CT images by rapid prototyping technique. This phantom was irradiated at a same JRR-4 neutron beam as clinical irradiation condition of the patient and the thermal neutron distribution on the brain surface was measured in detail. This experimental evaluation technique using a realistic phantom is applicable to in vitro cell irradiation experiments for radiation biological effects as well as in-phantom experiments for dosimetry under the nearly medical irradiation condition of patient. (author)

  10. A Monte Carlo simulation of a simplified reactor by decomposition of the neutron spectrum into fission, intermediate and thermal distributions

    Energy Technology Data Exchange (ETDEWEB)

    Barcellos, Luiz Felipe F.C.; Bodmann, Bardo E.J.; Vilhena, Marco T. de, E-mail: luizfelipe.fcb@gmail.com, E-mail: bardo.bodmann@ufrgs.br, E-mail: vilhena@mat.ufrgs.br [Universidade Federal do Rio Grande do Sul (UFRGS), Porto Alegre (Brazil). Grupo de Estudos Nucleares. Escola de Engenharia; Leite, Sergio Q. Bogado, E-mail: sbogado@eletronuclear.gov.br [Eletrobras Termonuclear S.A. (ELETRONUCLEAR), Rio de Janeiro, RJ (Brazil)

    2015-07-01

    In this paper the neutron spectrum of a simulated hypothetical nuclear reactor is decomposed as a sum of three probability distributions. Two of the distributions preserve shape with time but not necessarily the integral. One of the two distributions is due to fission, i.e. high neutron energies and the second a Maxwell-Boltzmann distribution for low (thermal) neutron energies. The third distribution has an a priori unknown and possibly variable shape with time and is determined from parametrizations of Monte Carlo simulation. This procedure is effective in attaining two objectives, the first is to include effects due to up-scattering of neutrons, and the second is to optimize computational time of the stochastic method (tracking and interaction). The simulation of the reactor is done with a Monte Carlo computer code with tracking and using continuous energy dependence. This code so far computes down-scattering, but the computation of up-scattering was ignored, since it increases significantly computational processing time. In order to circumvent this problem, one may recognize that up-scattering is dominant towards the lower energy end of the spectrum, where we assume that thermal equilibrium conditions for neutrons immersed in their environment holds. The optimization may thus be achieved by calculating only the interaction rate for neutron energy gain as well as loss and ignoring tracking, i.e. up-scattering is 'simulated' by a statistical treatment of the neutron population. For the fission and the intermediate part of the neutron spectrum tracking is taken into account explicitly, where according to the criticality condition the integral of the fission spectrum may depend on time. This simulation is performed using continuous energy dependence, and as a rst case to be studied we assume a recurrent regime. The three calculated distributions are then used in the Monte Carlo code to compute the subsequent Monte Carlo steps with subsequent updates

  11. Safety analysis of high pressure 3He-filled micro-channels for thermal neutron detection.

    Energy Technology Data Exchange (ETDEWEB)

    Ferko, Scott M.; Galambos, Paul C.; Derzon, Mark Steven; Renzi, Ronald F.

    2008-11-01

    This document is a safety analysis of a novel neutron detection technology developed by Sandia National Laboratories. This technology is comprised of devices with tiny channels containing high pressure {sup 3}He. These devices are further integrated into large scale neutron sensors. Modeling and preliminary device testing indicates that the time required to detect the presence of special nuclear materials may be reduced under optimal conditions by several orders of magnitude using this approach. Also, these devices make efficient use of our {sup 3}He supply by making individual devices more efficient and/or extending the our limited {sup 3}He supply. The safety of these high pressure devices has been a primary concern. We address these safety concerns for a flat panel configuration intended for thermal neutron detection. Ballistic impact tests using 3 g projectiles were performed on devices made from FR4, Silicon, and Parmax materials. In addition to impact testing, operational limits were determined by pressurizing the devices either to failure or until they unacceptably leaked. We found that (1) sympathetic or parasitic failure does not occur in pressurized FR4 devices (2) the Si devices exhibited benign brittle failure (sympathetic failure under pressure was not tested) and (3) the Parmax devices failed unacceptably. FR4 devices were filled to pressures up to 4000 + 100 psig, and the impacts were captured using a high speed camera. The brittle Si devices shattered, but were completely contained when wrapped in thin tape, while the ductile FR4 devices deformed only. Even at 4000 psi the energy density of the compressed gas appears to be insignificant compared to the impact caused by the incoming projectile. In conclusion, the current FR4 device design pressurized up to 4000 psi does not show evidence of sympathetic failure, and these devices are intrinsically safe.

  12. Thermal fatigue crack nucleation in ferritic-martensitic steels before and after neutron irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Belyaeva, L.A.; Zisman, A.A.; Petersen, C. E-mail: claus.petersen@imf.fzk.de; Potapova, V.A.; Rybin, V.V

    2000-12-01

    Thermal fatigue behaviour of the ferritic-martensitic steels MANET-II, 12Cr-1.5NiMo and F82H-mod. have been investigated in the temperature range from 50 deg. C to 350 deg. C and total strain range {<=}0.33%. Crack appearance has been checked after 3x10{sup 3}, 6x10{sup 3} and 10{sup 4} cycles and has been successively detected in these steels. The thermal fatigue cracks have a transgranular character; sometimes, intergranular cracks are observed in the F82H-mod. steel. A certain correlation of grain size and ferrite content with the thermal fatigue crack peculiarities has been noted. Specimens of MANET-II and 12Cr-1.5NiMo have been irradiated in a WWR-M reactor with a fluence of 1x10{sup 25} n m{sup -2} at a temperature of 300 deg. C and then subjected to thermocyclic loading. It has been established that the neutron irradiation does not significantly affect fatigue crack nucleation in both materials.

  13. Measured thermal and fast neutron fluence rates for ATF-1 holders during ATR cycle 158B/159A

    Energy Technology Data Exchange (ETDEWEB)

    Smith, Larry Don [Idaho National Lab. (INL), Idaho Falls, ID (United States); Miller, David Torbet [Idaho National Lab. (INL), Idaho Falls, ID (United States); Walker, Billy Justin [Idaho National Lab. (INL), Idaho Falls, ID (United States)

    2016-11-01

    This report contains the thermal (2200 m/s) and fast (E>1MeV) neutron fluence rate data for the ATF-1 holders located in core for ATR Cycle 158B/159A which were measured by the Radiation Measurements Laboratory (RML).

  14. Thermal-hydraulic design of tungsten rod bundles for the APT 3He neutron spallation target

    Science.gov (United States)

    Willcutt, Gordon J. E.

    1995-01-01

    A preconceptual design has been developed for the 3He Target/Blanket System for the Accelerator Production of Tritium Project. The design use tungsten wire-wrapped rods to produce neutrons when the rods are struck by a proton beam. The rods are contained in bundles inside hexagonal Inconel ducts and cooled by D2O. Rod bundles are grouped in patterns in the proton beam inside a chamber filled with 3He that is transmuted to tritium by the neutrons coming from the tungsten rods. Additional 3He is transmuted in a blanket region surrounding the helium chamber. This paper describes the initial thermal-hydraulic design and testing that has been completed to confirm the designed calculations for pressure drop through the bundle and heat transfer in the bundle. Heat transfer tests were run to verify steady-state operation. These tests were followed by increasing power until nucleate boiling occurs to determine operating margins. Changes that improve the initial design are described.

  15. Spectroscopy of 41K by thermal neutron capture in 40K

    Science.gov (United States)

    Krusche, B.; Lieb, K. P.; Ziegeler, L.; Daniel, H.; Von Egidy, T.; Rascher, R.; Barreau, G.; Börner, H. G.; Warner, D. D.

    1984-04-01

    The γ-ray spectrum emitted after thermal neutron capture in 40K has been studied at the ILL high flux reactor with curved crystal Bragg, pair and Ge(Li) spectometers. 585 transitions were assigned to the reaction 40K(n, γ) 41K and 490 of them were placed into a 41K level scheme; 68 new states are proposed. On the basis of γ-ray branches to states with established spin and parity, many new spin-parity assignments were made. The level energies up to 4 MeV were measured with a precision of 8-50 eV relative to the 411.8 keV 198Au standard, those above 4 MeV with a precision of 50-100 eV. The spin of the capture state was found to be I = {7}/{2}; the neutron binding energy was determined to EB = 10095.25(10) keV. The level density of I π = {5}/{2}±, {7}/{2}±, {9}/{2}± states was analyzed in terms of the constant-temperature Fermi gas model. It was shown that in this spin window the level scheme is almost complete up to an excitation energy of 5 MeV.

  16. A neutron scattering study on the stability of trehalose mycolates under thermal stress

    Science.gov (United States)

    Migliardo, F.; Salmeron, C.; Bayan, N.

    2013-10-01

    The present paper is focused on the study of the dynamics of mycolic acids, which are fundamental components of the outer membrane (mycomembrane) of Mycobacterium tuberculosis. An elastic neutron scattering study of mycolic acid/H2O and lecithin/H2O mixtures as a function of temperature and exchanged wavevector Q has been carried out. This study provides an effective way for characterizing the dynamical properties, furnishing a set of parameters characterizing the different flexibility and rigidity of the investigated lipids. The behavior of the elastically scattered intensity profiles and the derived mean square displacements as a function of temperature shows a more marked temperature dependence for lecithin lipids in comparison with mycolic acids, so revealing a higher thermal stability of these latter. These findings could be useful for understanding the dynamics-function relation in the mycomembrane and then to relate it to the low permeability and high resistance of mycobacteria to many antibiotics.

  17. Dopper shift attenuation lifetime measurement in 54Cr following thermal neutron capture

    Science.gov (United States)

    Lieb, K. P.; Börner, H. G.; Dewey, M. S.; Jolie, J.; Robinson, S. J.; Ulbig, S.; Winter, Ch.

    1988-12-01

    The double crystal spectrometer GAMS4 in combination with the ILL high flux reactor has been used to determine the lifetimes of the 2620 KeV 2 +2, 3074 KeV 2 +3 and 3720 KeV (1, 2) + states in 54Cr. The initial recoil energy of about 0.5 KeV imparted by the primary γ-radiation after thermal neutron capture in 53Cr produces Doppler broadened line shapes of the secondary transitions. The large 2 +3→2 +1 M1 strength of B(M1)=0.39(6) μ2N suggests the 2 +3 state to be mixed symmetry character within the interacting boson model IBM-2.

  18. A tomography system at the thermal neutron column of the ENEA Casaccia TRIGA reactor

    CERN Document Server

    Rosa, R; Santoro, E; Massari, R; Sangiovanni, G; Storelli, L

    2002-01-01

    The developed system is intended for use at a collimated thermal neutron beam with a flux of about 10 sup 6 n/cm sup 2 s. The system works with a cooled CCD array (192 x 165 pixels) and an intensifier for light from a NE426 scintillator with traditional optical coupling. A fine mechanical regulation system allows an accurate positioning of the tomographer, also ensuring the alignment of the CCD array with the rotation and translation axes. The acquisition of 200 projections is carried out in about 30 min with a reconstruction time (40 min max) depending on the reconstruction-matrix order. Radiography and tomography of significant objects are illustrated. The reconstruction algorithm, including spatial and temporal inhomogeneity corrections and filters, was tested with good results for projections up to 512 x 512 pixels. (orig.)

  19. A tomography system at the thermal neutron column of the ENEA Casaccia TRIGA reactor

    Science.gov (United States)

    Rosa, R.; Festinesi, A.; Massari, R.; Sangiovanni, G.; Santoro, E.; Storelli, L.

    The developed system is intended for use at a collimated thermal neutron beam with a flux of about 106 n/cm2s. The system works with a cooled CCD array (192×165 pixels) and an intensifier for light from a NE426 scintillator with traditional optical coupling. A fine mechanical regulation system allows an accurate positioning of the tomographer, also ensuring the alignment of the CCD array with the rotation and translation axes. The acquisition of 200 projections is carried out in about 30min with a reconstruction time (40min max) depending on the reconstruction-matrix order. Radiography and tomography of significant objects are illustrated. The reconstruction algorithm, including spatial and temporal inhomogeneity corrections and filters, was tested with good results for projections up to 512×512 pixels.

  20. Experimental research in neutron physic and thermal-hydraulic at the CDTN Triga reactor

    Energy Technology Data Exchange (ETDEWEB)

    Mesquita, Amir Z.; Souza, Rose Mary G.P.; Ferreira, Andrea V.; Pinto, Antonio J.; Costa, Antonio C.L.; Rezende, Hugo C., E-mail: amir@cdtn.b, E-mail: souzarm@cdtn.b, E-mail: avf@cdtn.b, E-mail: ajp@cdtn.b, E-mail: aclc@cdtn.b, E-mail: hcr@cdtn.b [Centro de Desenvolvimento da Tecnologia Nuclear (CDTN/CNEN-MG), Belo Horizonte, MG (Brazil)

    2011-07-01

    The IPR-R1 TRIGA (Training, Research, Isotopes production, General Atomics) at Nuclear Technology Development Center (CDTN) is a pool type reactor cooled by natural circulation of light water and an open surface. TRIGA reactors, developed by General Atomics (GA), are the most widely used research reactor in the world and characterized by inherent safety. The IPR-R1 is the only Brazilian nuclear research reactor available and able to perform experiments in which interaction between neutronic and thermal-hydraulic areas occurs. The IPR-R1 has started up on November 11th, 1960. At that time the maximum thermal power was 30 kW. The present forced cooling system was built in the 70th and the power was upgraded to 100 kW. Recently the core configuration and instrumentation was upgraded again to 250 kW at steady state, and is awaiting the license of CNEN to operate definitely at this new power. This paper describes the experimental research project carried out in the IPR-R1 reactor that has as objective evaluate the behaviour of the reactor operational parameters, and mainly to investigate the influence of temperature on the neutronic variables. The research was supported by Research Support Foundation of the State of Minas Gerais (FAPEMIG) and Brazilian Council for Scientific and Technological Development (CNPq). The research project meets the recommendations of the IAEA, for safety, modernization and development of strategic plan for research reactors utilization. This work is in line with the strategic objectives of Brazil, which aims to design and construct the Brazilian Multipurpose research Reactor (RMB). (author)

  1. Some features and results of thermal neutron background measurements with the [ZnS(Ag)+{sup 6}LiF] scintillation detector

    Energy Technology Data Exchange (ETDEWEB)

    Kuzminov, V.V.; Alekseenko, V.V.; Barabanov, I.R.; Etezov, R.A.; Gangapshev, A.M.; Gavrilyuk, Yu.M.; Gezhaev, A.M.; Kazalov, V.V. [Institute for Nuclear Research, 117312 Moscow (Russian Federation); Khokonov, A.Kh. [Kh.M. Berbekov Kabardino-Balkarian State University, 360004 (Russian Federation); Panasenko, S.I. [V.N. Karazin Kharkiv National University, 61022 Kharkiv (Ukraine); Ratkevich, S.S., E-mail: ssratk@gmail.com [V.N. Karazin Kharkiv National University, 61022 Kharkiv (Ukraine)

    2017-01-01

    Features of a thermal neutron test detector with thin scintillator [ZnS(Ag)+{sup 6}LiF] are described. Background of the detector and its registration efficiency were defined as a result of measurements. The thermal neutron flux at different locations, and for different conditions around the Baksan Neutrino Observatory are reported. - Highlights: • This paper describes tests of a thermal neutron detector based on a thin scintillator ZnS(Ag) with {sup 6}LiF. • The results are a measurement of the background neutron flux from the detector and the detector's efficiency. • The thermal neutron flux at different locations, and for different conditions around the Baksan Neutrino Observatory are reported.

  2. Optimization of the geometry and composition of a neutron system for treatment by Boron Neutron Capture Therapy

    Directory of Open Access Journals (Sweden)

    Rohollah Gheisari

    2015-01-01

    Full Text Available Background: In the field of the treatment by Boron Neutron Capture Therapy (BNCT, an optimized neutron system was proposed. This study (simulation was conducted to optimize the geometry and composition of neutron system and increase the epithermal neutron flux for the treatment of deep tumors is performed. Materials and Methods: A neutron system for BNCT was proposed. The system included 252Cf neutron source, neutron moderator/reflector arrangement, filter and concrete. To capture fast neutrons, different neutron filters Fe, Pb, Ni and PbF2 with various thicknesses were simulated and studied. Li (with 1 mm thick was used for filtering of thermal neutrons. Bi with thickness of 1 cm was used to minimize the intensity of gamma rays. Monte Carlo simulation code MCNPX 2.4.0 was used for design of the neutron system and calculation of the neutron components at the output port of the system. Results: For different thicknesses of the filters, the fast neutron flux, the epithermal and thermal flux were calculated at the output port of the system. The spatial distribution of the fast neutron flux, the epithermal flux and gamma flux in human head phantom with the presence of 40 ppm of 10B were obtained. The present calculations showed that Pb filter (about 1 cm at the output port is suitable for fast neutron capture. The thickness of Li filter was determined due to its high absorption cross-section in thermal region. Bi was used as a gamma filter by the reason of it is good for shielding gamma rays, while having high transmission epithermal neutrons. Conclusion: The epithermal neutron flux has enhanced about 38 percent at the output port of the present system, compared with recent system proposed by Ghassoun et al. At 2 cm depth inside the head phantom, the neutron flux reaches a maximum value about . At this depth, the ratio of the thermal neutron flux to the epithermal flux is about three times, that suggests such a neutron system to treat tumors in the

  3. Thermal winds in stellar mass black hole and neutron star binary systems

    Science.gov (United States)

    Done, Chris; Tomaru, Ryota; Takahashi, Tadayuki

    2018-01-01

    Black hole binaries show equatorial disc winds at high luminosities, which apparently disappear during the spectral transition to the low/hard state. This is also where the radio jet appears, motivating speculation that both wind and jet are driven by different configurations of the same magnetic field. However, these systems must also have thermal winds, as the outer disc is clearly irradiated. We develop a predictive model of the absorption features from thermal winds, based on pioneering work of Begelman, McKee & Shields. We couple this to a realistic model of the irradiating spectrum as a function of luminosity to predict the entire wind evolution during outbursts. We show that the column density of the thermal wind scales roughly with luminosity, and does not shut off at the spectral transition, though its visibility will be affected by the abrupt change in ionizing spectrum. We re-analyse the data from H1743-322, which most constrains the difference in wind across the spectral transition, and show that these are consistent with the thermal wind models. We include simple corrections for radiation pressure, which allows stronger winds to be launched from smaller radii. These winds become optically thick around Eddington, which may even explain the exceptional wind seen in one observation of GRO J1655-40. These data can instead be fit by magnetic wind models, but similar winds are not seen in this or other systems at similar luminosities. Hence, we conclude that the majority (perhaps all) of current data can be explained by thermal or thermal-radiative winds.

  4. Shock tube study on the thermal decomposition of fluoroethane using infrared laser absorption detection of hydrogen fluoride.

    Science.gov (United States)

    Matsugi, Akira; Shiina, Hiroumi

    2014-08-28

    Motivated by recent shock tube studies on the thermal unimolecular decomposition of fluoroethanes, in which unusual trends have been reported for collisional energy-transfer parameters, the rate constants for the thermal decomposition of fluoroethane were investigated using a shock tube/laser absorption spectroscopy technique. The rate constants were measured behind reflected shock waves by monitoring the formation of HF by IR absorption at the R(1) transition in the fundamental vibrational band near 2476 nm using a distributed-feedback diode laser. The peak absorption cross sections of this absorption line have also been determined and parametrized using the Rautian-Sobel'man line shape function. The rate constant measurements covered a wide temperature range of 1018-1710 K at pressures from 100 to 290 kPa, and the derived rate constants were successfully reproduced by the master equation calculation with an average downward energy transfer, ⟨ΔEdown⟩, of 400 cm(-1).

  5. Enriched Boron-Doped Amorphous Selenium Based Position-Sensitive Solid-State Thermal Neutron Detector for MPACT Applications

    Energy Technology Data Exchange (ETDEWEB)

    Mandal, Krishna [Univ. of South Carolina, Columbia, SC (United States)

    2017-09-29

    High-efficiency thermal neutron detectors with compact size, low power-rating and high spatial, temporal and energy resolution are essential to execute non-proliferation and safeguard protocols. The demands of such detector are not fully covered by the current detection system such as gas proportional counters or scintillator-photomultiplier tube combinations, which are limited by their detection efficiency, stability of response, speed of operation, and physical size. Furthermore, world-wide shortage of 3He gas, required for widely used gas detection method, has further prompted to design an alternative system. Therefore, a solid-state neutron detection system without the requirement of 3He will be very desirable. To address the above technology gap, we had proposed to develop new room temperature solidstate thermal neutron detectors based on enriched boron (10B) and enriched lithium (6Li) doped amorphous Se (As- 0.52%, Cl 5 ppm) semiconductor for MPACT applications. The proposed alloy materials have been identified for its many favorable characteristics - a wide bandgap (~2.2 eV at 300 K) for room temperature operation, high glass transition temperature (tg ~ 85°C), a high thermal neutron cross-section (for boron ~ 3840 barns, for lithium ~ 940 barns, 1 barn = 10-24 cm2), low effective atomic number of Se for small gamma ray sensitivity, and high radiation tolerance due to its amorphous structure.

  6. Somatic mutation and recombination induced with reactor thermal neutrons in Drosophila melanogaster; Mutacion y recombinacion somaticas inducidas con neutrones termicos de reactor en Drosophila melanogaster

    Energy Technology Data Exchange (ETDEWEB)

    Zambrano A, F.; Guzman R, J.; Paredes G, L.; Delfin L, A. [Instituto Nacional de Investigaciones Nucleares, A.P. 18-1027, 11801 Mexico D.F. (Mexico)

    1997-07-01

    The SMART test of Drosophila melanogaster was used to quantify the effect over the somatic mutation and recombination induced by thermal and fast neutrons at the TRIGA Mark III reactor of the ININ at the power of 300 k W for times of 30, 60 and 120 minutes with total equivalent doses respectively of 20.8, 41.6 and 83.2 Sv. A linear relation between the radiation equivalent dose and the frequency of the genetic effects such as mutation and recombination was observed. The obtained results allow to conclude that SMART is a sensitive system to the induced damage by neutrons, so this can be used for studying its biological effects. (Author)

  7. Thermal properties, curing characteristics and water absorption of soybean oil-based thermoset

    Directory of Open Access Journals (Sweden)

    2011-06-01

    Full Text Available Epoxidized soybean oil (ESO was successfully thermal-cured by using methylhexahydrophthalic anhydride (MHHPA curing agent, in the presence of tetraethylammonium bromide (TEAB catalyst of varied concentration (0.3–0.8 phr. The polyesterification process of ESO thermoset was proven and supported by Fourier transforms infrared spectroscopy (FTIR and gas chromatography-mass spectroscopy analysis (GC-MS. A possible chemical reaction of the MHHPA, TEAB and ESO was proposed based on the experimental work. Differential scanning calorimetry (DSC and dynamic mechanical analysis (DMA revealed that there is a positive relationship between the degree of conversion and crosslink density of ESO thermoset with TEAB concentration. The kinetics of water absorption of the ESO thermoset were found to conform to Fickian law behavior.

  8. Covariance generation and uncertainty propagation for thermal and fast neutron induced fission yields

    Science.gov (United States)

    Terranova, Nicholas; Serot, Olivier; Archier, Pascal; De Saint Jean, Cyrille; Sumini, Marco

    2017-09-01

    Fission product yields (FY) are fundamental nuclear data for several applications, including decay heat, shielding, dosimetry, burn-up calculations. To be safe and sustainable, modern and future nuclear systems require accurate knowledge on reactor parameters, with reduced margins of uncertainty. Present nuclear data libraries for FY do not provide consistent and complete uncertainty information which are limited, in many cases, to only variances. In the present work we propose a methodology to evaluate covariance matrices for thermal and fast neutron induced fission yields. The semi-empirical models adopted to evaluate the JEFF-3.1.1 FY library have been used in the Generalized Least Square Method available in CONRAD (COde for Nuclear Reaction Analysis and Data assimilation) to generate covariance matrices for several fissioning systems such as the thermal fission of U235, Pu239 and Pu241 and the fast fission of U238, Pu239 and Pu240. The impact of such covariances on nuclear applications has been estimated using deterministic and Monte Carlo uncertainty propagation techniques. We studied the effects on decay heat and reactivity loss uncertainty estimation for simplified test case geometries, such as PWR and SFR pin-cells. The impact on existing nuclear reactors, such as the Jules Horowitz Reactor under construction at CEA-Cadarache, has also been considered.

  9. Residual stress determination in thermally sprayed metallic deposits by neutron diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Keller, Thomas; Margadant, Nikolaus; Pirling, Thilo; Riegert-Escribano, Maria J.; Wagner, Werner

    2004-05-25

    Neutron diffraction was used to obtain spatially resolved strain and stress profiles in thermally sprayed metallic 'NiCrAlY' deposits (chemical composition 67 wt.% Ni, 22 wt.% Cr, 10 wt.% Al, 1 wt.% Y) and the underlying steel substrates. Samples of four different spray techniques were analyzed: atmospheric and water stabilized plasma spraying (APS and WSP), flame spraying (FS) and wire arc spraying (WAS). The results are quantitatively compared with the average in-plane residual stress determined by complementary bending tests and the hole drilling technique. While the stress profiles from the surface to the interface in the deposits are similar for all investigated spray techniques, their absolute values and gradients vary strongly. This is attributed to different quenching stresses from the impinging particles, different thermal histories the deposit/substrate systems undergo during the spraying and subsequent cooling, and also to different coating properties. In the water stabilized plasma sprayed and the wire arc sprayed deposits, a gradient in the stress-free lattice parameter was observed. Crack formation is found to be a dominant mechanism for stress relaxation in the surface plane.

  10. Thermal neutron capture cross section of gadolinium by pile-oscillation measurements in MINERVE

    Energy Technology Data Exchange (ETDEWEB)

    Leconte, P.; Di-Salvo, J.; Antony, M.; Pepino, A. [CEA, DEN, DER, Cadarache, F-13108 Saint-Paul-Lez-Durance (France); Hentati, A. [International School in Nuclear Engineering, Cadarache, F-13108 Saint-Paul-Lez-Durance (France)

    2012-07-01

    Natural gadolinium is used as a burnable poison in most LWR to account for the excess of reactivity of fresh fuels. For an accurate prediction of the cycle length, its nuclear data and especially its neutron capture cross section needs to be known with a high precision. Recent microscopic measurements at Rensselaer Polytechnic Inst. (RPI) suggest a 11% smaller value for the thermal capture cross section of {sup 157}Gd, compared with most of evaluated nuclear data libraries. To solve this inconsistency, we have analyzed several pile-oscillation experiments, performed in the MINERVE reactor. They consist in the measurement of the reactivity variation involved by the introduction in the reactor of small-samples, containing different mass amounts of natural gadolinium. The analysis of these experiments is done through the exact perturbation theory, using the PIMS calculation tool, in order to link the reactivity effect to the thermal capture cross section. The measurement of reactivity effects is used to deduce the 2200 m.s-1 capture cross section of {sup nat}Gd which is (49360 {+-} 790) b. This result is in good agreement with the JEFF3.1.1 value (48630 b), within 1.6% uncertainty at 1{sigma}, but is strongly inconsistent with the microscopic measurements at RPI which give (44200 {+-} 500) b. (authors)

  11. Thermal-hydraulic criteria for the APT tungsten neutron source design

    Energy Technology Data Exchange (ETDEWEB)

    Pasamehmetoglu, K.

    1998-03-01

    This report presents the thermal-hydraulic design criteria (THDC) developed for the tungsten neutron source (TNS). The THDC are developed for the normal operations, operational transients, and design-basis accidents. The requirements of the safety analyses are incorporated into the design criteria, consistent with the integrated safety management and the safety-by-design philosophy implemented throughout the APT design process. The phenomenology limiting the thermal-hydraulic design and the confidence level requirements for each limit are discussed. The overall philosophy of the uncertainty analyses and the confidence level requirements also are presented. Different sets of criteria are developed for normal operations, operational transients, anticipated accidents, unlikely accidents, extremely unlikely accidents, and accidents during TNS replacement. In general, the philosophy is to use the strictest criteria for the high-frequency events. The criteria is relaxed as the event frequencies become smaller. The THDC must be considered as a guide for the design philosophy and not as a hard limit. When achievable, design margins greater than those required by the THDC must be used. However, if a specific event sequence cannot meet the THDC, expensive design changes are not necessary if the single event sequence results in sufficient margin to safety criteria and does not challenge the plant availability or investment protection considerations.

  12. Thermal expansion and decomposition of jarosite: a high-temperature neutron diffraction study

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Hongwu [Los Alamos National Laboratory; Zhao, Yusheng [Los Alamos National Laboratory; Vogel, Sven C [Los Alamos National Laboratory; Hickmott, Donald D [Los Alamos National Laboratory; Daemen, Luke L [Los Alamos National Laboratory; Hartl, Monika A [Los Alamos National Laboratory

    2009-01-01

    The structure of deuterated jarosite, KFe{sub 3}(SO{sub 4}){sub 2}(OD){sub 6}, was investigated using time-of-flight neutron diffraction up to its dehydroxylation temperature. Rietveld analysis reveals that with increasing temperature, its c dimension expands at a rate {approx}10 times greater than that for a. This anisotropy of thermal expansion is due to rapid increase in the thickness of the (001) sheet of [Fe(O,OH){sub 6}] octahedra and [SO{sub 4}] tetrahedra with increasing temperature. Fitting of the measured cell volumes yields a coefficient of thermal expansion, a = a{sub 0} + a{sub 1} T, where a{sub 0} = 1.01 x 10{sup -4} K{sup -1} and a{sub 1} = -1.15 x 10{sup -7} K{sup -2}. On heating, the hydrogen bonds, O1{hor_ellipsis}D-O3, through which the (001) octahedral-tetrahedral sheets are held together, become weakened, as reflected by an increase in the D{hor_ellipsis}O1 distance and a concomitant decrease in the O3-D distance with increasing temperature. On further heating to 575 K, jarosite starts to decompose into nanocrystalline yavapaiite and hematite (as well as water vapor), a direct result of the breaking of the hydrogen bonds that hold the jarosite structure together.

  13. Infrared absorption spectroscopy of carbon monoxide on nickel films: a low temperature thermal detection technique

    Energy Technology Data Exchange (ETDEWEB)

    Bailey, R.B.

    1978-11-01

    Sensitive vibrational spectra of carbon monoxide molecules adsorbed on evaporated nickel films have been measured by attaching a thermometer to the sample, cooling the assembly to liquid helium temperatures, and recording the temperature changes which occur when infrared radiation is absorbed. The measurements are made in an ultrahigh vacuum chamber in which the sample surface can be cleaned, heated, exposed to gas molecules and cooled to 1.6 K for the infrared measurements. The spectra of chemisorbed CO molecules are interpreted in terms of the linear and bridge adsorption sites on the nickel surface, and they show how the distribution of molecules among these sites changes when the CO coverage increases and intermolecular forces become important. The spectra of physically adsorbed molecules in both monolayer and multilayer films are also reported. Absorptions as small as five parts in 10/sup 5/ of the incident radiation can presently be detected in spectra covering broad bands of infrared frequencies with a resolution of 2 cm/sup -1/. This high sensitivity is attributable to the low noise and reduced background signal of the thermal detection scheme, to the stability of the rapid scan Fourier transform infrared spectrometer, and to the automated computerized data acquisition electronics. Better performance is expected in future experiments on single crystal samples as well as evaporated films. This will make it possible to study molecules with weaker absorptions than CO and to look for evidence of chemical reactions between different adsorbed molecules.

  14. Transient light-induced absorption in thermally reduced, periodically poled lithium niobate doped with yttrium

    Energy Technology Data Exchange (ETDEWEB)

    Schoke, Bettina; Imlau, Mirco [Physics Department, University of Osnabrueck (Germany); Merschjann, Christoph [Helmholtz-Zentrum GmbH, Berlin (Germany); Corradi, Garbor; Polgar, Katalin [Research Institute for Solid State Physics and Optics, Hungarian Academy of Sciences, Budapest (Hungary); Naumova, Inna [Physics Department, Moscow State University (Russian Federation)

    2010-07-01

    Excitation and recombination processes of small polarons are studied in thermally reduced, periodically poled LiNbO{sub 3} doped with Y (PPLN:Y). The reduction treatment creates bipolarons (Nb{sup 4+}{sub Li}:Nb{sup 4+}{sub Nb}) which are stable at room temperature. They may be dissociated optically into small bound (Nb{sub Li}{sup 4+}) and free (Nb{sub Nb}{sup 4+}) polarons (''optical gating''). The light-induced absorption arising from the population and depopulation of these centers is measured time-resolved via transient absorption spectroscopy in the blue and red spectral range after optical excitation with intense laser pulses ({lambda}=532 nm, t=8 ns). Besides dissociation and relaxation of bipolarons the investigations also indicate the presence of photo-induced hole polarons (O{sup -}) with comparatively longer lifetime. The findings can be explained by a periodic spatial modulation of the Nb{sub Li}{sup 5+} antisite concentration and of the degree of reduction. Both modulations most likely result from a periodic incorporation of Y ions on Li sites.

  15. A LiBr-H2O Absorption Refrigerator Incorporating a Thermally Activated Solution Pumping Mechanism

    Directory of Open Access Journals (Sweden)

    Ian W. Eames

    2017-02-01

    Full Text Available This paper provides an illustrated description of a proposed LiBr-H2O vapour absorption refrigerator which uses a thermally activated solution pumping mechanism that combines controlled variations in generator vapour pressure with changes it produces in static-head pressure difference to circulate the absorbent solution between the generator and absorber vessels. The proposed system is different and potentially more efficient than a bubble pump system previously proposed and avoids the need for an electrically powered circulation pump found in most conventional LiBr absorption refrigerators. The paper goes on to provide a sample set of calculations that show that the coefficient of performance values of the proposed cycle are similar to those found for conventional cycles. The theoretical results compare favourably with some preliminary experimental results, which are also presented for the first time in this paper. The paper ends by proposing an outline design for an innovative steam valve, which is a key component needed to control the solution pumping mechanism.

  16. Studies of Microwave Absorption in Liquids by Optical Heterodyne Detection of Thermally Induced Refractive Index Fluctuations.

    Science.gov (United States)

    Swicord, Mays Littleton

    This work describes the development and implementation of an optical detection method for determining the microwave absorption properties of liquids and liquid suspensions. The method employs a Mach-Zehnder interferometer illuminated with a single-frequency laser to detect fluctuations in the index of refraction of a transparent or semi-transparent substance placed in one arm of the interferometer. The fluctuations are induced by pulses of microwave energy which are introduced into the sample by a specially designed waveguide sample holder. The laser beams from the sample and reference arms of the interferometer recombine on a photodetector resulting in a heterodyne signal. This general method is called Phase Fluctuation Optical Heterodyne (PFLOH) spectroscopy. The method is theoretically capable of detecting refractive index changes of two parts in 10('12) in liquids with greater sensitivity for gases; however, experimental performance is somewhat more limited. Although there is an abundance of microwave spectroscopy literature, virtually all of it is devoted to the absorption properties of gases. There are two reasons for the lack of information on nongaseous substances. First, methods most commonly used on gases, such as absorption ratio methods, are not practical for liquids in this frequency range due to the difficulties of making accurate microwave measurements. PFLOH spectroscopy avoids this difficulty. Second, fine structure (or anomalous dispersion) in the microwave absorption spectra of liquids has been considered nonexistant or at best uninteresting. This level of interest is changing, however, due to possible biological effects of microwave radiation. A number of different types of biological responses have recently been observed and reported in animals exposed to microwave radiation. Some of these effects are clearly responses of the organism to increased local or whole body temperature levels. In some cases the response is not so clearly thermal in

  17. Thermal-neutron cross sections and resonance integrals of {sup 138}Ba and {sup 141}Pr using Am-Be neutron source

    Energy Technology Data Exchange (ETDEWEB)

    Panikkath, Priyada; Mohanakrishnan, P. [Manipal University, Manipal Centre for Natural Sciences, Karnataka (India)

    2016-09-15

    The thermal-neutron capture cross sections and resonance integrals of {sup 138}Ba(n, γ){sup 139}Ba and {sup 141}Pr(n, γ){sup 142}Pr were measured by activation method using an isotopic Am-Be neutron source. The estimations were with respect to that of {sup 55}Mn(n, γ){sup 56}Mn and {sup 197}Au(n, γ){sup 198}Au reference monitors. The measured thermal-capture cross section of {sup 138}Ba with respect to {sup 55}Mn is 0.410±0.023 b and with respect to {sup 197}Au is 0.386±0.019 b. The measured thermal-capture cross section of {sup 141}Pr with respect to {sup 55}Mn is 11.36±1.29 b and with respect to {sup 197}Au is 10.43±1.14 b. The resonance integrals for {sup 138}Ba are 0.380±0.033 b ({sup 55}Mn) and 0.364±0.027 b ({sup 197}Au) and for {sup 141}Pr are 21.05±2.88 b ({sup 55}Mn) and 15.27±1.87 b ({sup 197}Au). The comparison between the present measurements and various reported values are discussed. The cross sections corresponding to the selected isotopes are measured using an Am-Be source facility for the first time. (orig.)

  18. Determination of Scattering and Absorption Coefficients for Plasma-Sprayed Yttria-Stabilized Zirconia Thermal Barrier Coatings at Elevated Temperatures

    Science.gov (United States)

    Eldridge, Jeffrey I.; Spuckler, Charles M.; Markham, James R.

    2009-01-01

    The temperature dependence of the scattering and absorption coefficients for a set of freestanding plasma-sprayed 8 wt% yttria-stabilized zirconia (8YSZ) thermal barrier coatings (TBCs) was determined at temperatures up to 1360 C in a wavelength range from 1.2 micrometers up to the 8YSZ absorption edge. The scattering and absorption coefficients were determined by fitting the directional-hemispherical reflectance and transmittance values calculated by a four-flux Kubelka Munk method to the experimentally measured hemispherical-directional reflectance and transmittance values obtained for five 8YSZ thicknesses. The scattering coefficient exhibited a continuous decrease with increasing wavelength and showed no significant temperature dependence. The scattering is primarily attributed to the relatively temperature-insensitive refractive index mismatch between the 8YSZ and its internal voids. The absorption coefficient was very low (less than 1 per centimeter) at wavelengths between 2 micrometers and the absorption edge and showed a definite temperature dependence that consisted of a shift of the absorption edge to shorter wavelengths and an increase in the weak absorption below the absorption edge with increasing temperature. The shift in the absorption edge with temperature is attributed to strongly temperature-dependent multiphonon absorption. While TBC hemispherical transmittance beyond the absorption edge can be predicted by a simple exponential decrease with thickness, below the absorption edge, typical TBC thicknesses are well below the thickness range where a simple exponential decrease in hemispherical transmittance with TBC thickness is expected. [Correction added after online publication August 11, 2009: "edge to a shorter wavelengths" has been updated as edge to shorter wavelengths."

  19. The determination of kinetic parameters of LiF : Mg,Ti from thermal decaying curves of optical absorption bands

    CERN Document Server

    Yazici, A N

    2003-01-01

    In this paper, the thermal bleaching curves (TBCs) of specific optical absorption bands of LiF : Mg,Ti were measured as a function of temperature. The TBCs obtained were analysed to extract the kinetic parameters (the thermal activation energy (E) and the frequency factor (s)) of some TL glow peaks of LiF : Mg,Ti on the basis of the developed first-order kinetic model over a specified temperature region.

  20. Arsenic absorption by members of the Brassicacea family, analysed by neutron activation, k{sub 0}-method - preliminary results

    Energy Technology Data Exchange (ETDEWEB)

    Uemura, George; Matos, Ludmila Vieira da Silva; Silva, Maria Aparecida da; Ferreira, Alexandre Santos Martorano; Menezes, Maria Angela de Barros Correia [Centro de Desenvolvimento da Tecnologia Nuclear (CDTN-CNEN/MG), Belo Horizonte, MG (Brazil)], e-mail: george@cdtn.br, e-mail: menezes@cdtn.br

    2009-07-01

    Natural arsenic contamination is a cause for concern in many countries of the world including Argentina, Bangladesh, Chile, China, India, Mexico, Thailand and the United States of America and also in Brazil, specially in the Iron Quadrangle area, where mining activities has been contributing to aggravate natural contamination. Brassicacea is a plant family with edible species (arugula, cabbage, cauliflower, cress, kale, mustard, radish), ornamental ones (alysssum, field pennycress, ornamental cabbages and kales) and some species are known as metal and metalloid accumulators (Indian mustard, field pennycress), like chromium, nickel, and arsenic. The present work aimed at studying other taxa of the Brassicaceae family to verify their capability in absorbing arsenic, under controlled conditions, for possible utilisation in remediation activities. The analytical method chosen was neutron activation analysis, k{sub 0} method, a routine technique at CDTN, and also very appropriate for arsenic studies. To avoid possible interference from solid substrates, like sand or vermiculite, attempts were carried out to keep the specimens in 1/4 Murashige and Skoog basal salt solution (M and S). Growth was stumped, plants withered and perished, showing that modifications in M and S had to be done. The addition of nickel and silicon allowed normal growth of the plant specimens, for periods longer than usually achieved (more than two months); yielding samples large enough for further studies with other techniques, like ICP-MS, and other targets, like speciation studies. The results of arsenic absorption are presented here and the need of nickel and silicon in the composition of M and S is discussed. (author)

  1. A New On-the-Fly Sampling Method for Incoherent Inelastic Thermal Neutron Scattering Data in MCNP6

    Energy Technology Data Exchange (ETDEWEB)

    Pavlou, Andrew Theodore [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Brown, Forrest B. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Ji, Wei [Rensselaer Polytechnic Inst., Troy, NY (United States)

    2014-09-02

    At thermal energies, the scattering of neutrons in a system is complicated by the comparable velocities of the neutron and target, resulting in competing upscattering and downscattering events. The neutron wavelength is also similar in size to the target's interatomic spacing making the scattering process a quantum mechanical problem. Because of the complicated nature of scattering at low energies, the thermal data files in ACE format used in continuous-energy Monte Carlo codes are quite large { on the order of megabytes for a single temperature and material. In this paper, a new storage and sampling method is introduced that is orders of magnitude less in size and is used to sample scattering parameters at any temperature on-the-fly. In addition to the reduction in storage, the need to pre-generate thermal scattering data tables at fine temperatures has been eliminated. This is advantageous for multiphysics simulations which may involve temperatures not known in advance. A new module was written for MCNP6 that bypasses the current S(α,β) table lookup in favor of the new format. The new on-the-fly sampling method was tested for graphite for two benchmark problems at ten temperatures: 1) an eigenvalue test with a fuel compact of uranium oxycarbide fuel homogenized into a graphite matrix, 2) a surface current test with a \\broomstick" problem with a monoenergetic point source. The largest eigenvalue difference was 152pcm for T= 1200K. For the temperatures and incident energies chosen for the broomstick problem, the secondary neutron spectrum showed good agreement with the traditional S(α,β) sampling method. These preliminary results show that sampling thermal scattering data on-the-fly is a viable option to eliminate both the storage burden of keeping thermal data at discrete temperatures and the need to know temperatures before simulation runtime.

  2. An extension of diffusion theory for thermal neutrons near boundaries; Extension del campo de validez de la teoria de difusion para neutrones termico en las proximidades de bordes

    Energy Technology Data Exchange (ETDEWEB)

    Alvarez Rivas, J. L.

    1963-07-01

    The distribution of thermal neutron flux has been measured inside and outside copper rods of several diameters, immersed in water. It has been found that these distributions can be calculated by means of elemental diffusion theory if the value of the coefficient of diffusion is changed. this parameter is truly a diffusion coefficient, which now also depends on the diameter of the rod. Through a model an expression of this coefficient is introduced which takes account of the measurements of the author and of those reported in PUGC P/928 (1995), ANL-5872 (1959), DEGR 319 (D) (1961). This model could be extended also to plane geometry. (Author) 19 refs.

  3. Thermal and epithermal neutron fluence rate gradient measurements by PADC detectors in LINAC radiotherapy treatments-field

    Energy Technology Data Exchange (ETDEWEB)

    Barrera, M. T., E-mail: mariate9590@gmail.com; Barros, H.; Pino, F.; Sajo-Bohus, L. [Universidad Simón Bolívar, Nuclear Physics Laboratory, Sartenejas, Caracas (Venezuela, Bolivarian Republic of); Dávila, J. [Física Médica C. A. and Universidad Central de Venezuela, Caracas (Venezuela, Bolivarian Republic of)

    2015-07-23

    LINAC VARIAN 2100 is where energetic electrons produce Bremsstrahlung radiation, with energies above the nucleon binding energy (E≈5.5MeV). This radiation induce (γ,n) and (e,e’n) reactions mainly in the natural tungsten target material (its total photoneutron cross section is about 4000 mb in a energy range from 9-17 MeV). These reactions may occur also in other components of the system (e.g. multi leaf collimator). During radiation treatment the human body may receive an additional dose inside and outside the treated volume produced by the mentioned nuclear reactions. We measured the neutron density at the treatment table using nuclear track detectors (PADC-NTD). These covered by a boron-converter are employed, including a cadmium filter, to determine the ratio between two groups of neutron energy, i.e. thermal and epithermal. The PADC-NTD detectors were exposed to the radiation field at the iso-center during regular operation of the accelerator. Neutron are determined indirectly by the converting reaction {sup 10}B(n,α){sup 7}Li the emerging charged particle leave their kinetic energy in the PADC forming a latent nuclear track, enlarged by chemical etching (6N, NaOH, 70°C). Track density provides information on the neutron density through calibration coefficient (∼1.6 10{sup 4} neutrons /track) obtained by a californium source. We report the estimation of the thermal and epithermal neutron field and its gradient for photoneutrons produced in radiotherapy treatments with 18 MV linear accelerators. It was obsered that photoneutron production have higher rate at the iso-center.

  4. Development of a coupled neutronic/thermal-hydraulic tool with multi-scale capabilities and applications to HPLWR core analysis

    Energy Technology Data Exchange (ETDEWEB)

    Monti, Lanfranco, E-mail: lanfranco.monti@gmail.co [Karlsruhe Institute of Technology (KIT), Institute for Nuclear and Energy Technologies (IKET), Hermann-von-Helmholtzplatz 1, 76344 Eggenstein-Leopoldshafen (Germany); Starflinger, Joerg, E-mail: joerg.starflinger@ike.uni-stuttgart.d [Universitaet Stuttgart, Institut fuer Kernenergetik und Energiesysteme, Pfaffenwaldring 31, 70569 Stuttgart (Germany); Schulenberg, Thomas, E-mail: schulenberg@kit.ed [Karlsruhe Institute of Technology (KIT), Institute for Nuclear and Energy Technologies (IKET), Hermann-von-Helmholtzplatz 1, 76344 Eggenstein-Leopoldshafen (Germany)

    2011-05-15

    Highlights: Advanced analysis and design techniques for innovative reactors are addressed. Detailed investigation of a 3 pass core design with a multi-physics-scales tool. Coupled 40-group neutron transport/equivalent channels TH core analyses methods. Multi-scale capabilities: from equivalent channels to sub-channel pin-by-pin study. High fidelity approach: reduction of conservatism involved in core simulations. - Abstract: The High Performance Light Water Reactor (HPLWR) is a thermal spectrum nuclear reactor cooled and moderated with light water operated at supercritical pressure. It is an innovative reactor concept, which requires developing and applying advanced analysis tools as described in the paper. The relevant water density reduction associated with the heat-up, together with the multi-pass core design, results in a pronounced coupling between neutronic and thermal-hydraulic analyses, which takes into account the strong natural influence of the in-core distribution of power generation and water properties. The neutron flux gradients within the multi-pass core, together with the pronounced dependence of water properties on the temperature, require to consider a fine spatial resolution in which the individual fuel pins are resolved to provide precise evaluation of the clad temperature, currently considered as one of the crucial design criteria. These goals have been achieved considering an advanced analysis method based on the usage of existing codes which have been coupled with developed interfaces. Initially neutronic and thermal-hydraulic full core calculations have been iterated until a consistent solution is found to determine the steady state full power condition of the HPLWR core. Results of few group neutronic analyses might be less reliable in case of HPLWR 3-pass core than for conventional LWRs because of considerable changes of the neutron spectrum within the core, hence 40 groups transport theory has been preferred to the usual 2 groups

  5. Feasibility study for measurement of insulation compaction in the cryogenic rocket fuel storage tanks at Kennedy Space Center by fast/thermal neutron techniques

    Energy Technology Data Exchange (ETDEWEB)

    Livingston, R. A. [Materials Science and Engineering Dept., U. of Maryland, College Park, MD (United States); Schweitzer, J. S. [Physics Dept., U. of Connecticut, Storrs (United States); Parsons, A. M. [Goddard Space Flight Center, Greenbelt (United States); Arens, E. E. [John F. Kennedy Space Center, FL (United States)

    2014-02-18

    The liquid hydrogen and oxygen cryogenic storage tanks at John F. Kennedy Space Center (KSC) use expanded perlite as thermal insulation. Some of the perlite may have compacted over time, compromising the thermal performance and also the structural integrity of the tanks. Neutrons can readily penetrate through the 1.75 cm outer steel shell and through the entire 120 cm thick perlite zone. Neutrons interactions with materials produce characteristic gamma rays which are then detected. In compacted perlite the count rates in the individual peaks in the gamma ray spectrum will increase. Portable neutron generators can produce neutron simultaneous fluxes in two energy ranges: fast (14 MeV) and thermal (25 meV). Fast neutrons produce gamma rays by inelastic scattering which is sensitive to Si, Al, Fe and O. Thermal neutrons produce gamma rays by radiative capture in prompt gamma neutron activation (PGNA), which is sensitive to Si, Al, Na, K and H among others. The results of computer simulations using the software MCNP and measurements on a test article suggest that the most promising approach would be to operate the system in time-of-flight mode by pulsing the neutron generator and observing the subsequent die away curve in the PGNA signal.

  6. Feasibility study for measurement of insulation compaction in the cryogenic rocket fuel storage tanks at Kennedy Space Center by fast/thermal neutron techniques

    Science.gov (United States)

    Livingston, R. A.; Schweitzer, J. S.; Parsons, A. M.; Arens, E. E.

    2014-02-01

    The liquid hydrogen and oxygen cryogenic storage tanks at John F. Kennedy Space Center (KSC) use expanded perlite as thermal insulation. Some of the perlite may have compacted over time, compromising the thermal performance and also the structural integrity of the tanks. Neutrons can readily penetrate through the 1.75 cm outer steel shell and through the entire 120 cm thick perlite zone. Neutrons interactions with materials produce characteristic gamma rays which are then detected. In compacted perlite the count rates in the individual peaks in the gamma ray spectrum will increase. Portable neutron generators can produce neutron simultaneous fluxes in two energy ranges: fast (14 MeV) and thermal (25 meV). Fast neutrons produce gamma rays by inelastic scattering which is sensitive to Si, Al, Fe and O. Thermal neutrons produce gamma rays by radiative capture in prompt gamma neutron activation (PGNA), which is sensitive to Si, Al, Na, K and H among others. The results of computer simulations using the software MCNP and measurements on a test article suggest that the most promising approach would be to operate the system in time-of-flight mode by pulsing the neutron generator and observing the subsequent die away curve in the PGNA signal.

  7. Measurement of the thermal neutron capture cross section and the resonance integral of the {sup 109}Ag(n,{gamma}){sup 110m}Ag reaction

    Energy Technology Data Exchange (ETDEWEB)

    Nakamura, S.; Wada, H.; Furutaka, K.; Harada, H.; Katoh, T. [Japan Nuclear Cycle Development Inst., Tokai Works, Tokai, Ibaraki (Japan)

    2001-03-01

    The thermal neutron capture cross section ({sigma}{sub 0}) and the resonance integral (I{sub 0}) of the {sup 109}Ag(n,{gamma}) reaction were measured by the activation and {gamma}-ray spectroscopic methods to develop a neutron flux monitor for the long irradiation. (author)

  8. The effect of fast neutron and gamma irradiation on thermal, structural and colorant properties of 2,6-diaminopyridine.

    Science.gov (United States)

    Mohammadi, Hassangholi; Hassanzadeh, Ali; Khodabakhsh, Rasol

    2010-10-01

    The variation in structural, thermal and colorant properties of 2,6-diaminopyridine were studied using differential scanning calorimetry (DSC), UV-visible, NMR spectroscopies and powder X-ray diffraction techniques, before and after fast neutrons irradiation with 2.12 and 3.50 kGy and gamma irradiation with 136.16 Gy doses. Under fast neutron irradiation, the sample enthalpy values, and melting and boiling temperatures were varied with increase in the irradiation dose. But the variation in boiling temperature was more pronounced than that of the melting point. However, there was no drastic change in these transition temperatures. The kinetic parameters were calculated using free isoconversional and Kissinger analysis methods. Moreover, UV-visible spectra showed that fast neutron and gamma irradiations had destroyed the color of the title compound. The gamma irradiation showed similar effect on structural and thermal properties. Results are also shown where the intensity of XRD patterns strongly depends on the irradiation dose. According to the NMR results, it seems that the collision occurs between para-hydrogen of 2,6-DAP and fast neutrons. Copyright 2010 Elsevier Ltd. All rights reserved.

  9. Development of CFD thermal hydraulics and neutron kinetics coupling methodologies for the prediction of local safety parameters for light water reactors

    Energy Technology Data Exchange (ETDEWEB)

    Perez Manes, Jorge

    2013-02-26

    This dissertation contributes to the development of high-fidelity coupled neutron kinetic and thermal hydraulic simulation tools with high resolution of the spatial discretization of the involved domains for the analysis of Light Water Reactors transient scenarios.

  10. Coincident emission of neutrons and charged particles after π- absorption in 6Li, 7Li, 12C, 59Co and 197Au

    Science.gov (United States)

    Heusi, P.; Isaak, H. P.; Pruys, H. S.; Engfer, R.; Hermes, E. A.; Kozlowski, T.; Sennhauser, U.; Walter, H. K.

    1983-10-01

    Energy spectra d 3W/d E1 d E2 d cos ϑ of neutron-neutron and neutron-charged particle pairs (nn, np, nd, nt) emitted after the absorption of stopped negative pions in 6Li, 7Li, 12C, 59Co and 197Au have been measured for opening angles between 50° and 180°. Particle pairs emitted from light nuclei without energy loss due to final-state interactions were identified by the energy balance. Pion absorption on two nucleons (quasi-deuteron mechanism) was found to be the main process. The yields of nucleon pairs from quasi-free absorption on a quasi-deuteron are 0.52 ± 0.09 per π-stop, 0.57 ± 0.10 per π-stop and 0.19 ± 0.04 per π-stop for 6Li, 7Li and 12C, respectively. The ratio R of np to pp pairs that absorb the pion was determined for quasi-free absorption on p-shell nucleons of 12C: R(p-shell) = 6.3 ± 1.4. For pion absorption on s-shell nucleons of lithium lower limits R(s-shell) > 4.4 for 6Li and R(s-shell) > 7.8 for 7Li were determined. These values are larger than the statistical ratios Rstat = 2 N/( Z - 1) of np to pp pairs in the nucleus. Lower limits for the probability for pion absorption on heavier clusters ( 3He, α) are W(hc) > 0.16 per π-stop for 6Li, W(hc) > 0.11 per π-stop for 7Li and W( α) > 0.01 per π-stop for 12C. The shape of the energy spectra of pairs emitted directly after quasi-free absorption on 2 or 4 nucleons could be explained by a simple model for the momentum distribution of the absorbing nucleons. The results are in agreement with the parameters of the momentum distributions known from other reactions. Energy spectra and opening-angle distributions were compared with the intranuclear cascade calculations of Chiang, Hüfner and Hachenberg. For 59Co and 197Au the spectra are strongly influenced by the final-state interactions; lower limits of R > 1.8 for 59Co and R > 2.5 for 197Au were determined.

  11. Coincident emission of neutrons and charged particles after. pi. /sup -/ absorption in /sup 6/Li, /sup 7/Li, /sup 12/C, /sup 59/Co and /sup 197/Au

    Energy Technology Data Exchange (ETDEWEB)

    Heusi, P.; Isaak, H.P.; Pruys, H.S.; Engfer, R.; Hermes, E.A. (Zurich Univ. (Switzerland). Physik-Institut); Kozlowski, T.; Sennhauser, U.; Walter, H.K. (Eidgenoessische Technische Hochschule, Zurich (Switzerland). Lab. fuer Hochenergiephysik)

    1983-10-17

    Energy spectra d/sup 3/W/dE/sub 1/dE/sub 2/ d cos theta of neutron-neutron and neutron-charged particle pairs (nn, np, nd, nt) emitted after the absorption of stopped negative pions in /sup 6/Li, /sup 7/Li, /sup 12/C, /sup 59/Co and /sup 197/Au have been measured for opening angles between 50/sup 0/ and 180/sup 0/. Particle pairs emitted from light nuclei without energy loss due to final-state interactions were identified by the energy balance. Pion absorption on two nucleons (quasi-deuteron mechanism) was found to be the main process. The yields of nucleon pairs from quasi-free absorption on a quasi-deuteron are 0.52 +- 0.09 per ..pi..-stop, 0,57 +- 0.10 per ..pi..-stop and 0.19 +- 0.04 per ..pi..-stop for /sup 6/Li, /sup 7/Li and /sup 12/C, respectively. The ratio R of np to pp pairs that absorb the pion was determined for quasi-free absorption on p-shell nucleons of /sup 12/C: R(p-shell)=6.3 +- 1.4. For pion absorption on s-shell nucleons of lithium lower limits R(s-shell) > 4.4 for /sup 6/Li and R(s-shell) > 7.8 for /sup 7/Li were determined. These values are larger than the statistical ratios Rsub(stat)=2N/(Z-1) of np to pp pairs in the nucleus. Lower limits for the probability for pion absorption on heavier clusters (/sup 3/He, ..cap alpha..) are W(hc) > 0.16 per ..pi..-stop for /sup 6/Li, W (hc) > 0.11 per ..pi..-stop for /sup 7/Li and W(..cap alpha..) > 0.01 per ..pi..-stop for /sup 12/C. The shape of the energy spectra of pairs emitted directly after quasi-free absorption on 2 or 4 nucleons could be explained by a simple model for the momentum distribution of the absorbing nucleons. The results are in agreement with the parameters of the momentum distributions known from other reactions. Energy spectra and opening-angle distributions were compared with the intranuclear cascade calculations of Chiang, Huefner, and Hachenberg. For /sup 59/Co and /sup 197/ Au the spectra are strongly influenced by the final-state interactions; lower limits of R > 1.8 for /sup

  12. From gold leaf to thermal neutrons: One hundred years of radioactivity and geological exploration (Invited)

    Science.gov (United States)

    Howarth, R. J.

    2010-12-01

    down an oil well to make a down-hole radioactivity profile. Technical advances were rapidly reflected in prospecting on foot, by car, and in the air, with successive adoption of the electrometer (1927); the Geiger-Müller (1945), scintillation (1952) and Hare (1954) counters; and the gamma-spectrometer (1960). The modern era of well-logging began with the patenting by Fearon in 1937 of logs using gamma rays (discovered by Viellard, 1900; named by Rutherford, 1914) and neutrons (discovered by Chadwick, 1932), although the term ‘gamma ray log’ is reported as having first been used on 29 October 1938. A simultaneous gamma and neutron logging device was developed by Sherbatskoy in 1951. Neutron-gamma and gamma-gamma logs followed in the next two years and, by the time it was possible to undertake this with a single instrument (Monaghan 1961), further tools had been developed to attempt detection of both hydrocarbons and salt water in the formations passed through. One-hundred years after Pearce’s discovery, the Thermal Neutron Decay Time Log was introduced; the marriage of radioactivity and geology had truly come of age.

  13. Thermal neutron Die-Away-Time studies for P&DGNAA of large samples at the MEDINA facility

    OpenAIRE

    Mildenberger, Frank; Mauerhofer, Eric

    2015-01-01

    THERMAL NEUTRON DIE-WAY-TIME STUDIES FOR P&DGNAA OF RADIOACTIVE WASTE DRUMS AT THE MEDINA FACILITYFrank Mildenberger*, Eric MauerhoferInstitute of Energy and Climate Research – Nuclear Waste Management and Reactor Safety, Forschungszentrum Juelich GmbH; 52425 Juelich, Germany*Correspondence: (F. Mildenberger)IntroductionIn Germany, radioactive waste with negligible heat production has to pass through a process of quality checking in order to check its conformance ...

  14. Development of Effective Algorithm for Coupled Thermal-Hydraulics – Neutron-Kinetics Analysis of Reactivity Transient

    OpenAIRE

    Peltonen, Joanna

    2009-01-01

    Analyses of nuclear reactor safety have increasingly required coupling of full three dimensional neutron kinetics (NK) core models with system transient thermal-hydraulics (TH) codes. To produce results within a reasonable computing time, the coupled codes use different spatial description of the reactor core. The TH code uses few, typically 5 to 20 TH channels, which represent the core. The NK code uses explicit node for each fuel assembly. Therefore, a spatial mapping of coarse grid TH and ...

  15. Neutronic and thermal-hydraulic analysis of new irradiation channels inside the Moroccan TRIGA Mark II research reactor core.

    Science.gov (United States)

    Chham, E; El Bardouni, T; Benaalilou, K; Boukhal, H; El Bakkari, B; Boulaich, Y; El Younoussi, C; Nacir, B

    2016-10-01

    This study was conducted to improve the capacity of radioisotope production in the Moroccan TRIGA Mark II research reactor, which is considered as one of the most important applications of research reactors. The aim of this study is to enhance the utilization of TRIGA core in the field of neutron activation and ensure an economic use of the fuel. The main idea was to create an additional irradiation channel (IC) inside the core. For this purpose, three new core configurations are proposed, which differ according to the IC position in the core. Thermal neutron flux distribution and other neutronic safety parameters such as power peaking factors, excess reactivity, and control rods worth reactivity were calculated using the Monte Carlo N-Particle Transport (MCNP) code and neutron cross-section library based on ENDF/B-VII evaluation. The calculated thermal flux in the central thimble (CT) and in the added IC for the reconfigured core is compared with the thermal flux in the CT of the existing core, which is taken as a reference. The results show that all the obtained fluxes in CTs are very close to the reference value, while a remarkable difference is observed between the fluxes in the new ICs and reference. This difference depends on the position of IC in the reactor core. To demonstrate that the Moroccan TRIGA reactor could safely operate at 2MW, with new configurations based on new ICs, different safety-related thermal-hydraulic parameters were investigated. The PARET model was used in this study to verify whether the safety margins are met despite the new modifications of the core. The results show that it is possible to introduce new ICs safely in the reactor core, because the obtained values of the parameters are largely far from compromising the safety of the reactor. Copyright © 2016 Elsevier Ltd. All rights reserved.

  16. Effects of thermal aging and neutron irradiation on the mechanical properties of three-wire stainless steel weld overlay cladding

    Energy Technology Data Exchange (ETDEWEB)

    Haggag, F.M.; Nanstad, R.K.

    1997-05-01

    Thermal aging of three-wire series-arc stainless steel weld overlay cladding at 288{degrees}C for 1605 h resulted in an appreciable decrease (16%) in the Charpy V-notch (CVN) upper-shelf energy (USE), but the effect on the 41-J transition temperature shift was very small (3{degrees}C). The combined effect of aging and neutron irradiation at 288{degrees}C to a fluence of 5 x 10{sup 19} neutrons/cm{sup 2} (> 1 MeV) was a 22% reduction in the USE and a 29{degrees}C shift in the 41-J transition temperature. The effect of thermal aging on tensile properties was very small. However, the combined effect of irradiation and aging was an increase in the yield strength (6 to 34% at test temperatures from 288 to {minus}125{degrees}C) but no apparent change in ultimate tensile strength or total elongation. Neutron irradiation reduced the initiation fracture toughness (J{sub Ic}) much more than did thermal aging alone. Irradiation slightly decreased the tearing modulus, but no reduction was caused by thermal aging alone. Other results from tensile, CVN, and fracture toughness specimens showed that the effects of thermal aging at 288 or 343{degrees}C for 20,000 h each were very small and similar to those at 288{degrees}C for 1605 h. The effects of long-term thermal exposure time (50,000 h and greater) at 288{degrees}C will be investigated as the specimens become available in 1996 and beyond.

  17. Experimental Research of the Radiative Capture of Thermal Neutrons in $^{3}$He

    CERN Document Server

    Bystritsky, V M; Enik, T L; Filipowicz, M; Gerasimov, V V; Grebenyuk, V M; Kobzev, A P; Kublikov, R V; Nesvizhevsky, V V; Parzhitskii, S S; Pavlov, V N; Popov, N P; Salamatin, A V; Shvetsov, V N; Slepnev, V M; Strelkov, A V; Wozniak, J; Zamyatin, N I

    2006-01-01

    A project of an experiment on measurement of the cross sections of radiative thermal neutron capture by $^{3}$He nuclei with production of one and two $\\gamma $-quanta ($n_{\\rm th}+^{3}$He $\\to \\alpha + \\gamma $(2$\\gamma $)) is presented. The interest in studying the processes is dictated by the following factors: a possibility of obtaining information on parameters of the nucleon $N$-$N$ potential and structure of exchange meson currents; a possibility of verifying the model of the mechanism for nucleon capture by the nucleus $^{3}$He in the low-energy region; necessity to solve some questions existing in astrophysics. The experiment is planned to be carried out on the PF1B beam of ILL reactor (Grenoble). The target is a hollow cylinder of pure aluminium ($\\varnothing$140$\\times $80~mm) filled with $^{3}$He and $^{4}$He (background experiment) at the pressure 2~atm. Registration of the $\\gamma $-quanta is carried out by four BGO crystal ($\\varnothing$100$\\times $70~mm) detectors. According to the calculation...

  18. Structural, thermal and optical absorption features of heavy metal oxides doped tellurite rich glasses

    Directory of Open Access Journals (Sweden)

    Kawa M. Kaky

    Full Text Available In order to improve tellurite glass stability to be applicable for optical fiber amplifier applications, glasses with the composition of (70 − xTeO2. (10ZnO. (10WO3. (5Na2O. (5TiO2. (xBi2O3 (x = 1, 2, 3, 4, and 5 mol% have been produced and characterized using the related methods. Structural properties were investigated using X-ray diffraction (XRD which confirms the non-crystalline structure and scanning electron microscopy (SEM micrographs also confirm the XRD results. The energy dispersive X-ray (EDX analysis profiles show that all the mentioned elements are present in the prepared glasses. Following the IR spectra, all the tellurium bonds such as stretching vibrations of TeO4 tbp and TeO3/TeO3+1 unit are revealed. Raman spectra confirm the presence of different functional groups, actually, it shows bands mainly in four spectral regions: R1 (65–150 cm−1, R2 (280–550 cm−1, R3 (880–950 cm−1 and R4 (916–926 cm−1 and the identified bands are assigned to respective molecular groups. The thermal study was carried out using Differential scanning calorimetry (DSC which indicates good thermal stability of the synthesized glasses with increasing Bi concentration. From the optical absorption spectra, we evaluated cut-off edge wavelengths and found increasing cutoff wavelength with an increase in Bi2O3 concentration. In the UV–Visible region, optical band gap energy and allowed transitions were investigated using three methods; direct, indirect, and absorption spectrum fitting (ASF, and band gaps from indirect and ASF were matched. Keywords: Tellurite glasses, XRD, FT-IR, Raman, TGA/DSC

  19. Design and spectrum calculation of 4H-SiC thermal neutron detectors using FLUKA and TCAD

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Haili; Tang, Xiaoyan; Guo, Hui, E-mail: guohui@mail.xidian.edu.cn; Zhang, Yimen; Zhang, Yimeng; Zhang, Yuming

    2016-10-11

    SiC is a promising material for neutron detection in a harsh environment due to its wide band gap, high displacement threshold energy and high thermal conductivity. To increase the detection efficiency of SiC, a converter such as {sup 6}LiF or {sup 10}B is introduced. In this paper, pulse-height spectra of a PIN diode with a {sup 6}LiF conversion layer exposed to thermal neutrons (0.026 eV) are calculated using TCAD and Monte Carlo simulations. First, the conversion efficiency of a thermal neutron with respect to the thickness of {sup 6}LiF was calculated by using a FLUKA code, and a maximal efficiency of approximately 5% was achieved. Next, the energy distributions of both {sup 3}H and α induced by the {sup 6}LiF reaction according to different ranges of emission angle are analyzed. Subsequently, transient pulses generated by the bombardment of single {sup 3}H or α-particles are calculated. Finally, pulse height spectra are obtained with a detector efficiency of 4.53%. Comparisons of the simulated result with the experimental data are also presented, and the calculated spectrum shows an acceptable similarity to the experimental data. This work would be useful for radiation-sensing applications, especially for SiC detector design.

  20. Modeling the absorption behavior of solar thermal collector coatings utilizing graded alpha-C:H/TiC layers.

    Science.gov (United States)

    Gruber, D P; Engel, G; Sormann, H; Schüler, A; Papousek, W

    2009-03-10

    Wavelength selective coatings are of common use in order to enhance the efficiency of devices heated by radiation such as solar thermal collectors. The use of suitable materials and the optimization of coating layer thicknesses are advisable ways to maximize the absorption. Further improvement is achievable by embedding particles in certain layers in order to modify material properties. We focus on optimizing the absorption behavior of a solar collector setup using copper as substrate, a layer of amorphous hydrogenated carbon with embedded titanium carbide particles (a-C:H/TiC), and an antireflection coating of amorphous silicon dioxide (aSiO(2)). For the setup utilizing homogeneous particle distribution, a relative absorption of 90.98% was found, while inhomogeneous particle embedding yielded 98.29%. These results are particularly interesting since until now, absorption of more than 95% was found only by using embedded Cr but not by using the more biocompatible Ti.

  1. The effect of incremental gamma-ray doses and incremental neutron fluences upon the performance of self-biased sup 1 sup 0 B-coated high-purity epitaxial GaAs thermal neutron detectors

    CERN Document Server

    Gersch, H K; Simpson, P A

    2002-01-01

    High-purity epitaxial GaAs sup 1 sup 0 B-coated thermal neutron detectors advantageously operate at room temperature without externally applied voltage. Sample detectors were systematically irradiated at fixed grid locations near the core of a 2 MW research reactor to determine their operational neutron dose threshold. Reactor pool locations were assigned so that fast and thermal neutron fluxes to the devices were similar. Neutron fluences ranged between 10 sup 1 sup 1 and 10 sup 1 sup 4 n/cm sup 2. GaAs detectors were exposed to exponential fluences of base ten. Ten detector designs were irradiated and studied, differentiated between p-i-n diodes and Schottky barrier diodes. The irradiated sup 1 sup 0 B-coated detectors were tested for neutron detection sensitivity in a thermalized neutron beam. Little damage was observed for detectors irradiated at neutron fluences of 10 sup 1 sup 2 n/cm sup 2 and below, but signals noticeably degraded at fluences of 10 sup 1 sup 3 n/cm sup 2. Catastrophic damage was appare...

  2. Study of the Li{sub 2}CO{sub 3} as thermal neutrons detector; Estudio del Li{sub 2}CO{sub 3} como detector de neutrones termicos

    Energy Technology Data Exchange (ETDEWEB)

    Herrera A, E.; Urena N, F.; Delfin L, A. [ININ, 52045 Ocoyoacac, Estado de Mexico (Mexico)] e-mail: eha@nuclear.inin.mx

    2003-07-01

    The use every day but it frequents of the thermal neutrons in the treatment of tumours, using the neutron capture therapy technique in boron, there is generated the necessity to develop a dosimetric system that allows to evaluate in a reliable way the fluence and consequently the dose of neutrons that it is given in the tumours of the patients. One of the techniques but employees to determine the neutron fluence sub cadmic and epi cadmic in an indirect way, it is the activation of thin sheets of gold undress and covered with cadmium respectively that when being exposed to a neutron beam to the nuclear reaction {sup 197}Au (n, {gamma} ) {sup 198} Au, emitting gamma radiation with an energy of 0.4118 MeV, being this, a disadvantage to be used as dosemeter. On the other hand, when exposing the lithium carbonate to a thermal neutron beam, free radicals of CO{sub 3} that are quantified by the electron paramagnetic resonance technique are generated. This work analyzes those basic parameters that determine if those made up of Li{sub 2}CO{sub 3} complete with the requirements to be used as detectors and/or dosemeters of thermal neutrons. (Author)

  3. Interface requirements to couple thermal-hydraulic codes to 3D neutronic codes

    Energy Technology Data Exchange (ETDEWEB)

    Langenbuch, S.; Austregesilo, H.; Velkov, K. [GRS, Garching (Germany)] [and others

    1997-07-01

    The present situation of thermalhydraulics codes and 3D neutronics codes is briefly described and general considerations for coupling of these codes are discussed. Two different basic approaches of coupling are identified and their relative advantages and disadvantages are discussed. The implementation of the coupling for 3D neutronics codes in the system ATHLET is presented. Meanwhile, this interface is used for coupling three different 3D neutronics codes.

  4. Thermal neutron radiative capture on cadmium as a counting technique at the INES beam line at ISIS: A preliminary investigation of detector cross-talk.

    Science.gov (United States)

    Festa, G; Grazzi, F; Pietropaolo, A; Scherillo, A; Schooneveld, E M

    2017-12-01

    Experimental tests are presented that assess the cross-talk level among three scintillation detectors used as neutron counters exploiting the thermal neutron radiative capture on Cd. The measurements were done at the INES diffractometer operating at the ISIS spallation neutron source (Rutherford Appleton Laboratory, UK). These tests follow a preliminary set of measurements performed on the same instrument to study the effectiveness of this thermal neutron counting strategy in neutron diffraction measurements, typically performed on INES using squashed 3He filled gas tubes. The experimental data were collected in two different geometrical configurations of the detectors and compared to results of Monte Carlo simulations, performed using the MCNP code. Copyright © 2017 Elsevier Ltd. All rights reserved.

  5. Neutron Stars

    Science.gov (United States)

    Cottam, J.

    2007-01-01

    Neutron stars were discovered almost 40 years ago, and yet many of their most fundamental properties remain mysteries. There have been many attempts to measure the mass and radius of a neutron star and thereby constrain the equation of state of the dense nuclear matter at their cores. These have been complicated by unknown parameters such as the source distance and burning fractions. A clean, straightforward way to access the neutron star parameters is with high-resolution spectroscopy. I will present the results of searches for gravitationally red-shifted absorption lines from the neutron star atmosphere using XMM-Newton and Chandra.

  6. Neutronics and thermal hydraulic analysis of TRIGA Mark II reactor using MCNPX and COOLOD-N2 computer code

    Science.gov (United States)

    Tiyapun, K.; Wetchagarun, S.

    2017-06-01

    The neutronic analysis of TRIGA Mark II reactor has been performed. A detailed model of the reactor core was conducted including standard fuel elements, fuel follower control rods, and irradiation devices. As the approach to safety nuclear design are based on determining the criticality (keff), reactivity worth, reactivity excess, hot rod power factor and power peaking of the reactor, the MCNPX code had been used to calculate the nuclear parameters for different core configuration designs. The thermal-hydraulic model has been developed using COOLOD-N2 for steady state, using the nuclear parameters and power distribution results from MCNPX calculation. The objective of the thermal-hydraulic model is to determine the thermal safety margin and to ensure that the fuel integrity is maintained during steady state as well as during abnormal condition at full power. The hot channel fuel centerline temperature, fuel surface temperature, cladding surface temperature, the departure from nucleate boiling (DNB) and DNB ratio were determined. The good agreement between experimental data and simulation concerning reactor criticality proves the reliability of the methodology of analysis from neutronic and thermal hydraulic perspective.

  7. Thermal hydraulic and neutron kinetic simulation of the Angra 2 reactor using a RELAP5/PARCS coupled model

    Energy Technology Data Exchange (ETDEWEB)

    Reis, Patricia A.L.; Costa, Antonella L.; Hamers, Adolfo R.; Pereira, Claubia; Rodrigues, Thiago D.A.; Mantecon, Javier G.; Veloso, Maria A.F., E-mail: patricialire@yahoo.com.br, E-mail: antonella@nuclear.ufmg.br, E-mail: adolforomerohamers@hotmail.com, E-mail: claubia@nuclear.ufmg.br, E-mail: thiagodanielbh@gmail.com, E-mail: mantecon1987@gmail.com, E-mail: dora@nuclear.ufmg.br [Universidade Federal de Minas Gerais (UFMG), Belo Horizonte, MG (Brazil). Departamento de Engenharia Nuclear; Instituto Nacional de Ciencias e Tecnologia de Reatores Nucleares Inovadores (INCT/CNPq), Belo Horizonte (Brazil); Miro, Rafael; Verdu, Gumersindo, E-mail: rmiro@iqn.upv.es, E-mail: gverdu@iqn.upv.es [Universidad Politecnica de Valencia (Spain). Departamento de Ingenieria Quimica y Nuclear

    2015-07-01

    The computational advances observed in the last two decades have been provided direct impact on the researches related to nuclear simulations, which use several types of computer codes, including coupled between them, allowing representing with very accuracy the behavior of nuclear plants. Studies of complex scenarios in nuclear reactors have been improved by the use of thermal-hydraulic (TH) and neutron kinetics (NK) coupled codes. This technique consists in incorporating three-dimensional (3D) neutron modeling of the reactor core into codes, mainly to simulate transients that involve asymmetric core spatial power distributions and strong feedback effects between neutronics and reactor thermal-hydraulics. Therefore, this work presents preliminary results of TH RELAP5 and the NK PARCS calculations applied to model of the Angra 2 reactor. The WIMSD-5B code has been used to generate the macroscopic cross sections used in the NK code. The results obtained are satisfactory and represent important part of the development of this methodology. The next step is to couple the codes. (author)

  8. Thermal Boundary Layer Effects on Line-of-Sight Tunable Diode Laser Absorption Spectroscopy (TDLAS) Gas Concentration Measurements.

    Science.gov (United States)

    Qu, Zhechao; Werhahn, Olav; Ebert, Volker

    2018-01-01

    The effects of thermal boundary layers on tunable diode laser absorption spectroscopy (TDLAS) measurement results must be quantified when using the line-of-sight (LOS) TDLAS under conditions with spatial temperature gradient. In this paper, a new methodology based on spectral simulation is presented quantifying the LOS TDLAS measurement deviation under conditions with thermal boundary layers. The effects of different temperature gradients and thermal boundary layer thickness on spectral collisional widths and gas concentration measurements are quantified. A CO 2 TDLAS spectrometer, which has two gas cells to generate the spatial temperature gradients, was employed to validate the simulation results. The measured deviations and LOS averaged collisional widths are in very good agreement with the simulated results for conditions with different temperature gradients. We demonstrate quantification of thermal boundary layers' thickness with proposed method by exploitation of the LOS averaged the collisional width of the path-integrated spectrum.

  9. Neutron Imaging at LANSCE—From Cold to Ultrafast

    Directory of Open Access Journals (Sweden)

    Ronald O. Nelson

    2018-02-01

    Full Text Available In recent years, neutron radiography and tomography have been applied at different beam lines at Los Alamos Neutron Science Center (LANSCE, covering a very wide neutron energy range. The field of energy-resolved neutron imaging with epi-thermal neutrons, utilizing neutron absorption resonances for contrast as well as quantitative density measurements, was pioneered at the Target 1 (Lujan center, Flight Path 5 beam line and continues to be refined. Applications include: imaging of metallic and ceramic nuclear fuels, fission gas measurements, tomography of fossils and studies of dopants in scintillators. The technique provides the ability to characterize materials opaque to thermal neutrons and to utilize neutron resonance analysis codes to quantify isotopes to within 0.1 atom %. The latter also allows measuring fuel enrichment levels or the pressure of fission gas remotely. More recently, the cold neutron spectrum at the ASTERIX beam line, also located at Target 1, was used to demonstrate phase contrast imaging with pulsed neutrons. This extends the capabilities for imaging of thin and transparent materials at LANSCE. In contrast, high-energy neutron imaging at LANSCE, using unmoderated fast spallation neutrons from Target 4 [Weapons Neutron Research (WNR facility] has been developed for applications in imaging of dense, thick objects. Using fast (ns, time-of-flight imaging, enables testing and developing imaging at specific, selected MeV neutron energies. The 4FP-60R beam line has been reconfigured with increased shielding and new, larger collimation dedicated to fast neutron imaging. The exploration of ways in which pulsed neutron beams and the time-of-flight method can provide additional benefits is continuing. We will describe the facilities and instruments, present application examples and recent results of all these efforts at LANSCE.

  10. Speciation of methylmercury in market seafood by thermal degradation, amalgamation and atomic absorption spectroscopy.

    Science.gov (United States)

    Ruiz-de-Cenzano, Manuela; Rochina-Marco, Arancha; Cervera, M Luisa; de la Guardia, Miguel

    2014-09-01

    Sample thermal decomposition followed by mercury amalgamation and atomic absorption has been employed for the determination of methylmercury (MeHg) in fish. The method involves HBr leaching of MeHg, extraction into toluene, and back-extraction into an aqueous l-cysteine solution. Preliminary studies were focused on the extraction efficiency, losses, contaminations, and species interconversion prevention. The limit of detection was 0.018µgg(-1) (dry weight). The intraday precision for three replicate analysis at a concentration of 4.2µgg(-1) (dry weight) was 3.5 percent, similar to the interday precision according to analysis of variance (ANOVA). The accuracy was guaranteed by the use of fortified samples involving 83-105 percent recoveries, and certified reference materials TORT-2 (lobster hepatopancreas) and DORM-3 (dogfish liver), providing 107 and 98 percent recovery of certified values. The greenness of the method was also evaluated with the analytical eco-scale being obtained a final score of 73 points which means an acceptable green analysis. The method was applied to fifty-seven market samples of different fish acquired from local markets in several sampling campaigns. The content of MeHg found varied between 0.0311 and 1.24µgg(-1) (wet weight), with values that involve 33-129 percent of the total mercury content. Some considerations about food safety were also done taking into account data about Spanish fish consume and Tolerable Weekly Intake (TWI) established for MeHg. Copyright © 2014 Elsevier Inc. All rights reserved.

  11. Anti mutagenesis of chemical modulators against damage induced by reactor thermal neutrons; Antimutagenesis de moduladores quimicos contra el dano inducido por neutrones termicos de reactor

    Energy Technology Data Exchange (ETDEWEB)

    Zambrano A, F.; Guzman R, J.; Garcia B, A.; Paredes G, L.; Delfin L, A. [Instituto Nacional de Investigaciones Nucleares, Departamentos de Materiales Radiactivos, de Biologia, del Reactor y Gerencia de Aplicaciones Nucleares en la Salud, A.P. 18-1027, 11801 Mexico D.F. (Mexico)

    1999-07-01

    The mutations are changes in the genetic information whether for spontaneous form or induced by the exposure of the genetic material to certain agents, called mutagens: chemical or physical (diverse types of radiations). As well as exist a great variety of mutagens and pro mutagens (these last are agents which transform themselves in mutagens after the metabolic activation). Also several chemical compounds exist which are called antimutagens because they reduce the mutagens effect. The C vitamin or ascorbic acid (A A) presents antimutagenic and anti carcinogenic properties. On the other hand a sodium/copper salt derived from chlorophyll belonging to the porphyrin group (C L) contains a chelated metal ion in the center of molecule. It is also an antioxidant, antimutagenic and anti carcinogenic compound, it is called chlorophyllin. The objective of this work is to establish if the A A or the C L will reduce the damages induced by thermal and fast reactor neutrons. (Author)

  12. Parametric studies by means of uncertainty and sensitivity methods for coupled thermal-hydraulic/neutron-physics application

    Energy Technology Data Exchange (ETDEWEB)

    Jaeger, W.; Sanchez, V.; Cheng, X. [Karlsruhe Institute of Technology (KIT), Eggenstein-Leopoldshafen (Germany). Inst. for Neutron Physics and Reactor Technology; Monti, L. [Karlsruhe Institute of Technology (KIT), Eggenstein-Leopoldshafen (Germany). Inst. for Nuclear and Energy Technologies; Hurtado, A. [Technical Univ. of Dresden (Germany). Inst. of Power Engineering

    2011-07-01

    At the Institute for Neutron Physics and Reactor Technology (INR) at the Karlsruhe Institute of Technology (KIT), the development and validation of coupled codes systems is one major activity. In this paper, a 2-step method is proposed to perform uncertainty and sensitivity analysis of a nuclear fuel bundle. At first, the SUSA package (Software system for Uncertainty and Sensitivity Analysis), 2 is applied to the thermal hydraulic results of the TRACE (TRACE/RELAP Advanced Computational Engine) code to identify crucial thermal hydraulic parameter combinations which are successively used in the TH/NP coupled system TRACEERANOS to account for the neutronic feedbacks. This 2-step method was applied since the TRACE-ERANOS system runs 1 input in approximately 1 day (depending on the computer configurations). Since the uncertainty and sensitivity analysis requires about 100 runs of the thermal hydraulic input (with altered parameters, running within minutes) an integral TRACE-SUSA-ERANOS analysis would need around 100 days. For this analysis a fuel assembly model of the HPLWR (High Performance Light Water Reactor) was selected. Due to the general structure of the coupling and code communication scripts, the system can be used for any kind of reactor/system which can be described with TRACE and ERANOS (e.g., fast systems) while SUSA can be applied to anything. (orig.)

  13. Neutronic and thermal-hydraulic calculations for the AP-1000 NPP with the MCNP6 and SERPENT codes

    Energy Technology Data Exchange (ETDEWEB)

    Stefani, Giovanni Laranjo; Maiorino, Jose R.; Santos, Thiago A., E-mail: giovanni.laranjo@ufabc.edu.br, E-mail: joserubens.maiorino@ufabc.edu.br, E-mail: thiago.santos@ufabc.edu.br [Universidade Federal do ABC (CECS/UFABC), Santo Andre, SP (Brazil). Centro de Engenharia, Modelagem e Ciencias Sociais; Rossi, Pedro R., E-mail: pedro.russorossi@gmail.com [FERMIUM - Tecnologia Nuclear, Sao Paulo, SP (Brazil)

    2015-07-01

    The AP-1000 is an evolutionary PWR reactor designed as an evolution of the AP-600 project. The reactor is already pre-licensed by NRC, and is considered to have achieved high standards of safety, possible short construction time and good economic competitiveness. The core is a 17x17 typical assembly using Zirlo as cladding, 3 different enrichment regions, and is controlled by boron, control banks, and burnable poison. The expected fuel final burnup is 62 MWD/ton U and a cycle of 18 months. In this paper we present results for neutronic and thermal-hydraulic calculations for the AP-1000. We use the MCNP6 and SERPENT codes to calculate the first cycle of operation. The calculated parameters are K{sub eff} at BOL and EOL and its variation with burnup and neutron flux, and reactivity coefficients. The production of transuranic elements such as Pu-239 and Pu-241, and burning fuel are calculated over time. In the work a complete reactor was burned for 450 days with no control elements, boron or burnable poison were considered, these results were compared with data provided by the Westinghouse. The results are compared with those reported in the literature. A simple thermal hydraulic analysis allows verification of thermal limits such as fuel and cladding temperatures, and MDNB. (author)

  14. Neutron Albedo

    CERN Document Server

    Ignatovich, V K

    2005-01-01

    A new, algebraic, method is applied to calculation of neutron albedo from substance to check the claim that use of ultradispersive fuel and moderator of an active core can help to gain in size and mass of the reactor. In a model of isotropic distribution of incident and reflected neutrons it is shown that coherent scattering on separate grains in the case of thermal neutrons increases transport cross section negligibly, however it decreases albedo from a wall of finite thickness because of decrease of substance density. A visible increase of albedo takes place only for neutrons with wave length of the order of the size of a single grain.

  15. Determination of nitrogen in wheat flour through Activation analysis using Fast neutron flux of a Thermal nuclear reactor; Determinacion de nitrogeno en harina de trigo mediante analisis por activacion empleando el flujo de neutrones rapidos de un reactor nuclear termico

    Energy Technology Data Exchange (ETDEWEB)

    Ramirez G, T

    1976-07-01

    In this work is done a technical study for determining Nitrogen (protein) and other elements in wheat flour Activation analysis, with Fast neutrons from a Thermal nuclear reactor. Initially it is given an introduction about the basic principles of the methods of analysis. Equipment used in Activation analysis and a brief description of the neutron source (Thermal nuclear reactor). The realized experiments for determining the flux form in the irradiation site, the half life of N-13 and the interferences due to the sample composition are included too. Finally, the obtained results by Activation and the Kjeldahl method are tabulated. (Author)

  16. Literature survey of chemical analysis by thermal neutron induced capture gamma ray spectrometry

    Energy Technology Data Exchange (ETDEWEB)

    Gladney, E.S.

    1979-09-01

    A brief discussion of the principles and techniques of chemical analysis by neutron capture gamma radiation is presented, and the widely scattered literature is collected into a single table arranged by element measured.

  17. Measurement of very small hydrogen content in zirconium alloys by measuring thermal neutron incoherent scattering

    CERN Document Server

    Choi, Y N; Lee, C H; Oh, H S; Park, S D; Somenkov, V A

    2002-01-01

    In neutron-scattering experiments, the incoherent scattering contributes to the background signal, which is an unwelcome property of matter. Among natural nuclei, the hydrogen nucleus (proton) has a remarkably large value of incoherent neutron scattering cross section. Therefore, a very small amount of hydrogen in a material could be analyzed by measuring the neutron incoherent scattering of the material. The hydrogen content of a metal or semiconductor is a matter of concern because it can affect significantly the physical, mechanical or chemical properties of materials although the amount of hydrogen is very small. In this study, the neutron incoherent scattering was measured using a 1-D position-sensitive detector at 1.835 A. Estimated detection limits are about 5 and 2 mu g/g for 10-min and 1-h measurements, respectively. Using the calibration data obtained by measurement of artificial samples (zircaloy+polypropylene films), the relative amounts of hydrogen in three commercial zircaloy samples were estima...

  18. Total cross section of solid mesitylene, toluene and a mixture of them at thermal neutron energies

    Energy Technology Data Exchange (ETDEWEB)

    Rodriguez Palomino, L.A. [Centro Atomico Bariloche (CNEA), Av. Bustillo 9500, R8402AGP Bariloche, Rio Negro (Argentina); Instituto Balseiro (CNEA/UnCuyo), Av. Bustillo 9500, R8402AGP Bariloche, Rio Negro (Argentina); Consejo Nacional de Investigaciones Cientificas y Tecnicas, Av. Bustillo 9500, R8402AGP Bariloche, Rio Negro (Argentina); Cantargi, F. [Centro Atomico Bariloche (CNEA), Av. Bustillo 9500, R8402AGP Bariloche, Rio Negro (Argentina); Instituto Balseiro (CNEA/UnCuyo), Av. Bustillo 9500, R8402AGP Bariloche, Rio Negro (Argentina)], E-mail: cantargi@cab.cnea.gov.ar; Blostein, J.J. [Instituto Balseiro (CNEA/UnCuyo), Av. Bustillo 9500, R8402AGP Bariloche, Rio Negro (Argentina); Consejo Nacional de Investigaciones Cientificas y Tecnicas, Av. Bustillo 9500, R8402AGP Bariloche, Rio Negro (Argentina); Dawidowski, J.; Granada, J.R. [Centro Atomico Bariloche (CNEA), Av. Bustillo 9500, R8402AGP Bariloche, Rio Negro (Argentina); Instituto Balseiro (CNEA/UnCuyo), Av. Bustillo 9500, R8402AGP Bariloche, Rio Negro (Argentina); Consejo Nacional de Investigaciones Cientificas y Tecnicas, Av. Bustillo 9500, R8402AGP Bariloche, Rio Negro (Argentina)

    2009-01-15

    The total neutron cross sections of mesitylene, toluene and a solution 3:2 by volume of mesitylene and toluene were measured at the electron LINAC based pulsed neutron source of Centro Atomico Bariloche. Measurements were performed at 180 K, 120 K and 31.6 K for mesitylene and at 120 K and 31.6 K for toluene and a solution 3:2 by volume of mesitylene and toluene. The systems are potential moderator materials to be considered in the design of a cold neutron source due to their high resistance to radiation and the richness in low-energy excitations of their frequency spectra, that lead to produce an enhanced cold neutron flux.

  19. MEASUREMENT OF THE CONTRALATERAL BREAST PHOTON AND THERMAL NEUTRON DOSES IN BREAST CANCER RADIOTHERAPY: A COMPARISON BETWEEN PHYSICAL AND DYNAMIC WEDGES.

    Science.gov (United States)

    Bagheri, Hamed; Rabie Mahdavi, Seyed; Shekarchi, Babak; Manouchehri, Farhad; Farhood, Bagher

    2018-01-01

    This research aimed to measure the received photon and thermal neutron doses to contralateral breast (CB) in breast cancer radiotherapy for various field sizes in presence of physical and dynamic wedges. The measurement of photon and thermal neutron doses was carried out on right breast region of RANDO phantom (as CB) for 18 MV photon beams. The dose measurements were performed by thermoluminescent dosimeter chips. These measurements obtained for various field sizes in presence of physical and dynamic wedges. The findings of this study showed that the received doses (both of the photon and thermal neutron) to CB in presence of physical wedge for 11 × 13, 11 × 17 and 11 × 21 cm2 field sizes were 5.92, 6.36 and 6.77% of the prescribed dose, respectively as well as for dynamic wedge were 2.92, 4.63 and 5.60% of the prescribed dose, respectively. The results showed that the received photon and thermal neutron doses to CB increase with increment of field sizes. The received photon and thermal neutron doses to CB in presence of physical wedge were more than dynamic wedge. According to obtained findings, it is suggested that using a dynamic wedge is preferable than physical wedge, especially for medial tangential field. © The Author 2017. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

  20. Encapsulation of paclitaxel into a bio-nanocomposite. A study combining inelastic neutron scattering to thermal analysis and infrared spectroscopy

    Science.gov (United States)

    Martins, Murillo L.; Orecchini, Andrea; Aguilera, Luis; Eckert, Juergen; Embs, Jan; Matic, Aleksander; Saeki, Margarida J.; Bordallo, Heloisa N.

    2015-01-01

    The anticancer drug paclitaxel was encapsulated into a bio-nanocomposite formed by magnetic nanoparticles, chitosan and apatite. The aim of this drug carrier is to provide a new perspective against breast cancer. The dynamics of the pure and encapsulated drug were investigated in order to verify possible molecular changes caused by the encapsulation, as well as to follow which interactions may occur between paclitaxel and the composite. Fourier transformed infrared spectroscopy, thermal analysis, inelastic and quasi-elastic neutron scattering experiments were performed. These very preliminary results suggest the successful encapsulation of the drug.

  1. Methodology for Estimating Thermal and Neutron Embrittlement of Austenitic Stainless Steel Welds During Service in Light Water Reactors

    Energy Technology Data Exchange (ETDEWEB)

    Chopra, O. K.; Rao, A. S.

    2016-04-28

    The effect of thermal aging on the degradation of fracture toughness and Charpy-impact properties of austenitic stainless steel (SS) welds has been characterized at reactor temperatures. The solidification behavior and the distribution and morphology of the ferrite phase in SS welds are described. Thermal aging of the welds results in moderate decreases in Charpy-impact strength and fracture toughness. The upper-shelf Charpy-impact energy of aged welds decreases by 50–80 J/cm2. The decrease in fracture toughness J-R curve, or JIc is relatively small. Thermal aging has minimal effect on the tensile strength. The fracture properties of SS welds are insensitive to filler metal; the welding process has a significant effect. The large variability in the data makes it difficult to establish the effect of the welding process on fracture properties of SS welds. Consequently, the approach used for evaluating thermal and neutron embrittlement of austenitic SS welds relies on establishing a lower-bound fracture toughness J-R curve for unaged and aged, and non-irradiated and irradiated, SS welds. The existing fracture toughness J-R curve data for SS welds have been reviewed and evaluated to define lower-bound J-R curve for submerged arc (SA)/shielded metal arc (SMA)/manual metal arc (MMA) welds and gas tungsten arc (GTA)/tungsten inert gas (TIG) welds in the unaged and aged conditions. At reactor temperatures, the fracture toughness of GTA/TIG welds is a factor of about 2.3 higher than that of SA/SMA/MMA welds. Thermal aging decreases the fracture toughness by about 20%. The potential combined effects of thermal and neutron embrittlement of austenitic SS welds are also described. Lower-bound curves are presented that define the change in coefficient C and exponent n of the power-law J-R curve and the JIc value for SS welds as a function of neutron dose. The potential effects of reactor coolant environment on the fracture toughness of austenitic SS welds are also discussed.

  2. Measurement of the neutron capture cross section of the fissile isotope 235U with the CERN n_TOF total absorption calorimeter and a fission tagging based on micromegas detectors

    Science.gov (United States)

    Balibrea-Correa, J.; Mendoza, E.; Cano-Ott, D.; Krtička, M.; Altstadt, S.; Andrzejewski, J.; Audouin, L.; Bécares, V.; Barbagallo, M.; Bečvář, F.; Belloni, F.; Berthoumieux, E.; Billowes, J.; Boccone, V.; Bosnar, D.; Brugger, M.; Calviño, F.; Calviani, M.; Carrapiço, C.; Cerutti, F.; Chiaveri, E.; Chin, M.; Colonna, N.; Cortés, G.; Cortés-Giraldo, M. A.; Diakaki, M.; Domingo-Pardo, C.; Dressler, R.; Durán, I.; Eleftheriadis, C.; Ferrari, A.; Fraval, K.; Furman, V.; Göbel, K.; Guerrero, C.; Gómez-Hornillos, M. B.; Ganesan, S.; García, A. R.; Giubrone, G.; Gonçalves, I. F.; González, E.; Goverdovski, A.; Griesmayer, E.; Gunsing, F.; Heftrich, T.; Heinitz, S.; Hernández-Prieto, A.; Heyse, J.; Jenkins, D. G.; Jericha, E.; Käppeler, F.; Kadi, Y.; Karadimos, D.; Katabuchi, T.; Ketlerov, V.; Khryachkov, V.; Kivel, N.; Koehler, P.; Kokkoris, M.; Kroll, J.; Lampoudis, C.; Langer, C.; Leal-Cidoncha, E.; Lederer, C.; Leeb, H.; Leong, L. S.; Lerendegui-Marco, J.; Licata, M.; Losito, R.; Mallick, A.; Manousos, A.; Marganiec, J.; Martínez, T.; Massimi, C.; Mastinu, P.; Mastromarco, M.; Mengoni, A.; Milazzo, P. M.; Mingrone, F.; Mirea, M.; Mondelaers, W.; Paradela, C.; Pavlik, A.; Perkowski, J.; Plompen, A. J. M.; Praena, J.; Quesada, J. M.; Rauscher, T.; Reifarth, R.; Riego-Perez, A.; Robles, M.; Rubbia, C.; Ryan, J. A.; Sabaté-Gilarte, M.; Sarmento, R.; Saxena, A.; Schillebeeckx, P.; Schmidt, S.; Schumann, D.; Sedyshev, P.; Tagliente, G.; Tain, J. L.; Tarifeño-Saldivia, A.; Tarrío, D.; Tassan-Got, L.; Tsinganis, A.; Valenta, S.; Vannini, G.; Variale, V.; Vaz, P.; Ventura, A.; Vermeulen, M. J.; Vlachoudis, V.; Vlastou, R.; Wallner, A.; Ware, T.; Weigand, M.; Weiss, C.; Wright, T.; Žugec, P.

    2017-09-01

    The accuracy on neutron capture cross section of fissile isotopes must be improved for the design of future nuclear systems such as Gen-IV reactors and Accelerator Driven Systems. The High Priority Request List of the Nuclear Energy Agency, which lists the most important nuclear data requirements, includes also the neutron capture cross sections of fissile isotopes such as 233,235U and 239,241Pu. A specific experimental setup has been used at the CERN n_TOF facility for the measurement of the neutron capture cross section of 235U by a set of micromegas fission detectors placed inside a segmented BaF2 Total Absorption Calorimeter.

  3. Neutron detector

    Science.gov (United States)

    Stephan, Andrew C [Knoxville, TN; Jardret,; Vincent, D [Powell, TN

    2011-04-05

    A neutron detector has a volume of neutron moderating material and a plurality of individual neutron sensing elements dispersed at selected locations throughout the moderator, and particularly arranged so that some of the detecting elements are closer to the surface of the moderator assembly and others are more deeply embedded. The arrangement captures some thermalized neutrons that might otherwise be scattered away from a single, centrally located detector element. Different geometrical arrangements may be used while preserving its fundamental characteristics. Different types of neutron sensing elements may be used, which may operate on any of a number of physical principles to perform the function of sensing a neutron, either by a capture or a scattering reaction, and converting that reaction to a detectable signal. High detection efficiency, an ability to acquire spectral information, and directional sensitivity may be obtained.

  4. Comparison of best-estimate plus uncertainty and conservative methodologies for a PWR MSLB analysis using a coupled 3-D neutron-kinetics/thermal-hydraulic code

    OpenAIRE

    Pericas Casals, Raimon; Ivanov, K.; Reventós Puigjaner, Francesc; Batet Miracle, Lluís

    2017-01-01

    This paper compares the Best-Estimate Plus Uncertainty (BEPU) methodology with the Conservative Bounding methodology for design-basis-accident analysis. Calculations have been performed with TRACE [for thermal-hydraulic (TH) system calculations] and PARCS [for neutron-kinetics (NK) modeling] under the SNAP platform. DAKOTA is used under the SNAP interface for uncertainty and sensitivity analysis. A simplified three-dimensional (3-D) neutronics model of the Ascó II nuclear power plant is used ...

  5. Characteristics of a thermal neutrons scintillation detector with the [ZnS(Ag)+$^6$LiF] at different conditions of measurements

    OpenAIRE

    Alekseenko, V. V.; Barabanov, I. R.; Etezov, R. A.; Gavrilyuk, Yu. M.; Gangapshev, A. M.; Gezhaev, A. M.; Kazalov, V. V.; Khokonov, A. Kh.; Kuzminov, V. V.; Panasenko, S. I.; Ratkevich, S. S.

    2015-01-01

    A construction of a thermal neutron testing detector with a thin [ZnS(Ag)+$^6$LiF] scintillator is described. Results of an investigation of sources of the detector pulse origin and the pulse features in a ground and underground conditions are presented. Measurements of the scintillator own background, registration efficiency and a neutron flux at different objects of the BNO INR RAS were performed. The results are compared with the ones measured by the $^3$He proportional counter.

  6. Developing a vacuum thermal stripping - acid absorption process for ammonia recovery from anaerobic digester effluent.

    Science.gov (United States)

    Ukwuani, Anayo T; Tao, Wendong

    2016-12-01

    To prevent acetoclastic methanogens from ammonia inhibition in anaerobic digestion of protein-rich substrates, ammonia needs to be removed or recovered from digestate. This paper presents an innovative ammonia recovery process that couples vacuum thermal stripping with acid absorption. Ammonia is stripped out of digestate boiling at a temperature below the normal boiling point due to vacuum. Stripped ammonia is absorbed to a sulfuric acid solution, forming ammonium sulfate crystals as a marketable product. Three common types of digestate were found to have boiling point temperature-vacuum curves similar to water. Seven combinations of boiling temperature and vacuum (50 °C 16.6 kPa, 58 °C 20.0 kPa, 65 °C 25.1 kPa, 70 °C 33.6 kPa, 80 °C 54.0 kPa, 90 °C 74.2 kPa, and 100 °C 101.3 kPa) were tested for batch stripping of ammonia in dairy manure digestate. 93.3-99.9% of ammonia was stripped in 3 h. The Lewis-Whitman model fitted ammonia stripping process well. Ammonia mass transfer coefficient was significantly higher at boiling temperature 65-100 °C and vacuum pressure 25.1-101.3 kPa than 50-58 °C and 16.6-20.0 kPa. The low ammonia saturation concentrations (0-24 mg N/L) suggested a large driving force to strip ammonia. The optimum boiling point temperature - vacuum pressure for ammonia recovery in a recirculation line of a mesophilic digester was 65 °C and 25.1 kPa, at which the ammonia mass transfer coefficient was as high as 37.3 mm/h. Installation of a demister and liquid trap could avoid negative effects of higher stripping temperature and stronger vacuum on formation of ammonium sulfate crystals. Pilot tests demonstrated that high-purity ammonium sulfate crystals could be produced by controlling sulfuric acid content and maintaining acid solution saturated with ammonium sulfate. Although volatile organic compounds such as cyclohexene were found in the final acid solutions, no volatile organic compounds were found in the recovered

  7. The energy spectrum of delayed neutrons from thermal neutron induced fission of sup 2 sup 3 sup 5 U and its analytical approximation

    CERN Document Server

    Doroshenko, A Y; Tarasko, M Z

    2001-01-01

    The energy spectrum of the delayed neutrons is the poorest known of all input data required in the calculation of the effective delayed neutron fractions. In addition to delayed neutron spectra based on the aggregate spectrum measurements there are two different approaches for deriving the delayed neutron energy spectra. Both of them are based on the data related to the delayed neutron spectra from individual precursors of delayed neutrons. In present work these two different data sets were compared with the help of an approximation by gamma-function. The choice of this approximation function instead of the Maxwellian or evaporation type of distribution is substantiated.

  8. Neutron-Induced Failures in Semiconductor Devices

    Energy Technology Data Exchange (ETDEWEB)

    Wender, Stephen Arthur [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2016-04-06

    This slide presentation explores single event effect, environmental neutron flux, system response, the Los Alamos Neutron Science Center (LANSCE) neutron testing facility, examples of SEE measurements, and recent interest in thermal neutrons.

  9. Development of a hybrid MSGC detector for thermal neutron imaging with a MHz data acquisition and histogramming system

    CERN Document Server

    Gebauer, B; Richter, G; Levchanovsky, F V; Nikiforov, A

    2001-01-01

    For thermal neutron imaging at the next generation of high-flux pulsed neutron sources a large area and fourfold segmented, hybrid, low-pressure, two-dimensional position sensitive, microstrip gas chamber detector, fabricated in a multilayer technology on glass substrates, is presently being developed, which utilizes a thin composite sup 1 sup 5 sup 7 Gd/CsI neutron converter. The present article focusses on the readout scheme and the data acquisition (DAQ) system. For position encoding, interpolating and fast multihit delay line based electronics is applied with up to eightfold sub-segmentation per geometrical detector segment. All signals, i.e. position, time-of-flight and pulse-height signals, are fed into deadtime-less 8-channel multihit TDC chips with 120 ps LSB via constant fraction and time-over-threshold discriminators, respectively. The multihit capability is utilized to raise the count rate limit in combination with a sum check algorithm for disentangling pulses from different events. The first vers...

  10. The Verification of Coupled Neutronics Thermal-Hydraulics Code NODAL3 in the PWR Rod Ejection Benchmark

    Directory of Open Access Journals (Sweden)

    Surian Pinem

    2014-01-01

    Full Text Available A coupled neutronics thermal-hydraulics code NODAL3 has been developed based on the few-group neutron diffusion equation in 3-dimensional geometry for typical PWR static and transient analyses. The spatial variables are treated by using a polynomial nodal method while for the neutron dynamic solver the adiabatic and improved quasistatic methods are adopted. In this paper we report the benchmark calculation results of the code against the OECD/NEA CRP PWR rod ejection cases. The objective of this work is to determine the accuracy of NODAL3 code in analysing the reactivity initiated accident due to the control rod ejection. The NEACRP PWR rod ejection cases are chosen since many organizations participated in the NEA project using various methods as well as approximations, so that, in addition to the reference solutions, the calculation results of NODAL3 code can also be compared to other codes’ results. The transient parameters to be verified are time of power peak, power peak, final power, final average Doppler temperature, maximum fuel temperature, and final coolant temperature. The results of NODAL3 code agree well with the PHANTHER reference solutions in 1993 and 1997 (revised. Comparison with other validated codes, DYN3D/R and ANCK, shows also a satisfactory agreement.

  11. Level structure of 89Sr investigated with thermal and fast neutron capture and the (d, p) reaction

    Science.gov (United States)

    Winter, Ch.; Krusche, B.; Lieb, K. P.; Michaelsen, S.; Hlawatsch, G.; Linder, H.; Von Egidy, T.; Hoyler, F.; Casten, R. F.

    1989-01-01

    The γ-ray spectrum emitted after thermal neutron capture in 88Sr was studied at the ILL high flux reactor with a pair-spectrometer and an intrinsic Ge detector. A total of 221 transitions were assigned to the decay 89Sr, and 55 of these, representing 55% of the observed flux, were placed in a level scheme of 19 states. The neutron binding energy was determined as 6358.73 (13) keV. Neutron capture in the 23.6 keV{3}/{2}- resonance was studied at the BNL filtered beam facility. Only seven transitions were attributed to 89Sr, and the decay of the capture state was found to be dominated by the valence process. High resolution (d, p) spectra were recorded at 20 MeV beam energy at the Munich Q3D spectrometer, and 55 states up to 4.5 MeV excitation energy in 89Sr were populated. The density of states observed in (n, γ) and (d, p) is analyzed in the Fermi-gas model, and the distribution of single-particle strengths is discussed from a statistical point of view.

  12. Neutron diffraction and thermal studies of amorphous CS{sub 2} realised by low-temperature vapour deposition

    Energy Technology Data Exchange (ETDEWEB)

    Yamamuro, O.; Matsuo, T. [Osaka Univ., Dept. of Chemistry, Graduate School of Sciences (Japan); Onoda-Yamamuro, N. [Tokyo Denki Univ., College of Sciences and Technology (Japan); Takeda, K. [Naruto Univ., Dept. of Chemistry, Tokushima (Japan); Munemura, H.; Tanaka, S.; Misawa, M. [Niigata Univ. (Japan). Faculty of Science

    2003-08-01

    We have succeeded in preparing amorphous carbon disulphide (CS{sub 2}) by depositing its vapour on a cold substrate at 10 K. Complete formation of the amorphous state has been confirmed by neutron diffraction and differential thermal analysis (DTA). The amorphous sample crystallized at ca. 70 K, which is lower than the hypothetical glass transition temperature (92 K) estimated from the DTA data of the (CS{sub 2}){sub x}(S{sub 2}Cl{sub 2}){sub 1-x} binary mixture. CS{sub 2}, a symmetric linear tri-atomic molecule, is the simplest of the amorphized molecular substances whose structural and thermal information has been reported so far. Comparison of the static structure factors S(Q) has shown that the orientational correlation of CS{sub 2} molecules may be much stronger in the amorphous state than in the liquid state at higher temperature. (authors)

  13. Coupled neutronics/thermal-hydraulics analysis of a high-performance light-water reactor fuel assembly

    Energy Technology Data Exchange (ETDEWEB)

    Waata, C.L.

    2006-07-15

    The use of water at supercritical pressure as coolant and moderator introduces a challenge in the design of a High-Performance Light-Water Reactor (HPLWR) fuel assembly. At supercritical pressure condition (P=25 MPa), the thermal-hydraulics behaviour of water differs strongly from that at sub-critical pressure due to a rapid variation of the thermal-physical properties across the pseudo-critical line. Due of the strong link between the water (moderation) and the neutron spectrum and subsequently the power distribution, a coupling of neutronics and thermal-hydraulics has become a necessity for reactor concepts operating at supercritical pressure condition. The effect of neutron moderation on the local parameters of thermal-hydraulics and vice-verse in a fuel assembly has to be considered for an accurate design analysis. In this study, the Monte Carlo N-Particle code (MCNP) and the sub-channel code STAFAS (Sub-channel Thermal-hydraulics Analysis of a Fuel Assembly under Supercritical conditions) have been coupled for the design analysis of a fuel assembly with supercritical water as coolant and moderator. Both codes are well known for complex geometry modelling. The MCNP code is used for neutronics analyses and for the prediction of power profiles of individual fuel rods. The sub-channel code STAFAS for the thermal-hydraulics analyses takes into account the coolant properties beyond the critical point as well as separate moderator channels. The coupling procedure is realized automatically. MCNP calculates the power distribution in each fuel rod, which is then transferred into STAFAS to obtain the corresponding thermal-hydraulic conditions in each sub-channel. The new thermal-hydraulic conditions are used to generate a new input deck for the next MCNP calculation. This procedure is repeated until a converged state is achieved. The coupled code system was tested on a proposed fuel assembly design of a HPLWR. An under-relaxation was introduced to achieve convergence

  14. Origin of Negative Thermal Expansion in Cubic ZrW2O8 Revealed by High Pressure Inelastic Neutron Scattering

    Science.gov (United States)

    Mittal, R.; Chaplot, S. L.; Schober, H.; Mary, T. A.

    2001-05-01

    Isotropic negative thermal expansion has been reported in cubic ZrW2O8 over a wide range of temperatures (0-1050 K). Here we report the direct experimental determination of the Grüneisen parameters of phonon modes as a function of their energy, averaged over the whole Brillouin zone, by means of high pressure inelastic neutron scattering measurements. We observe a pronounced softening of the phonon spectrum at P = 1.7 kbar compared to that at ambient pressure by about 0.1-0.2 meV for phonons of energy below 8 meV. This unusual phonon softening on compression, corresponding to large negative Grüneisen parameters, is able to account for the observed large negative thermal expansion.

  15. Negative thermal expansion in cubic ZrMo2 O8 : Inelastic neutron scattering and lattice dynamical studies

    Science.gov (United States)

    Mittal, R.; Chaplot, S. L.; Schober, H.; Kolesnikov, A. I.; Loong, C.-K.; Lind, C.; Wilkinson, A. P.

    2004-12-01

    Disordered cubic ZrMo2O8(Pa3¯,Z=4) is known to display isotropic negative thermal expansion (NTE) below 600 K. We report high-pressure inelastic neutron scattering experiments up to 2.5 kbar in this material using the IN6 spectrometer at Institut Laue-Langevin. The observed phonon softening of about 0.1-0.3 meV for phonons below 8 meV is able to account for the NTE below 100 K. The phonon spectrum in the entire energy range up to 150 meV has been measured using the HRMECS spectrometer at Argonne National Laboratory. The ordered phase (space group P213 ) of cubic ZrMo2O8 has not yet been synthesized. However, we have calculated the phonon spectrum and thermal expansion in this phase for comparison with the known ordered phase of cubic ZrW2O8 .

  16. Framing the performance of heat absorption/generation and thermal radiation in chemically reactive Darcy-Forchheimer flow

    Directory of Open Access Journals (Sweden)

    T. Hayat

    Full Text Available The present work aims to report the consequences of heterogeneous-homogeneous reactions in Darcy-Forchheimer flow of Casson material bounded by a nonlinear stretching sheet of variable thickness. Nonlinear stretched surface with variable thickness is the main agent for MHD Darcy-Forchheimer flow. Impact of thermal radiation and non-uniform heat absorption/generation are also considered. Flow in porous space is characterized by Darcy-Forchheimer flow. It is assumed that the homogeneous process in ambient fluid is governed by first order kinetics and the heterogeneous process on the wall surface is given by isothermal cubic autocatalator kinetics. The governing nonlinear ordinary differential equations are solved numerically. Effects of physical variables such as thickness, Hartman number, inertia and porous, radiation, Casson, heat absorption/generation and homogeneous-heterogeneous reactions are investigated. The variations of drag force (skin friction and heat transfer rate (Nusselt numberfor different interesting variables are plotted and discussed. Keywords: Casson fluid, Variable sheet thickness, Darcy-Forchheimer flow, Homogeneous-heterogeneous reactions, Heat generation/absorption, Thermal radiation

  17. MCNP Simulations of Measurement of Insulation Compaction in the Cryogenic Rocket Fuel Tanks at Kennedy Space Center by Fast/Thermal Neutron Techniques

    Science.gov (United States)

    Livingston, R. A.; Schweitzer, J. S.; Parsons, A. M.; Arens, E. E.

    2010-01-01

    MCNP simulations have been run to evaluate the feasibility of using a combination of fast and thermal neutrons as a nondestructive method to measure of the compaction of the perlite insulation in the liquid hydrogen and oxygen cryogenic storage tanks at John F. Kennedy Space Center (KSC). Perlite is a feldspathic volcanic rock made up of the major elements Si, AI, Na, K and 0 along with some water. When heated it expands from four to twenty times its original volume which makes it very useful for thermal insulation. The cryogenic tanks at Kennedy Space Center are spherical with outer diameters of 69-70 feet and lined with a layer of expanded perlite with thicknesses on the order of 120 cm. There is evidence that some of the perlite has compacted over time since the tanks were built 1965, affecting the thermal properties and possibly also the structural integrity of the tanks. With commercially available portable neutron generators it is possible to produce simultaneously fluxes of neutrons in two energy ranges: fast (14 Me V) and thermal (25 me V). The two energy ranges produce complementary information. Fast neutrons produce gamma rays by inelastic scattering, which is sensitive to Fe and O. Thermal neutrons produce gamma rays by prompt gamma neutron activation (PGNA) and this is sensitive to Si, Al, Na, K and H. The compaction of the perlite can be measured by the change in gamma ray signal strength which is proportional to the atomic number densities of the constituent elements. The MCNP simulations were made to determine the magnitude of this change. The tank wall was approximated by a I-dimensional slab geometry with an 11/16" outer carbon steel wall, an inner stainless wall and 120 cm thick perlite zone. Runs were made for cases with expanded perlite, compacted perlite or with various void fractions. Runs were also made to simulate the effect of adding a moderator. Tallies were made for decay-time analysis from t=0 to 10 ms; total detected gamma

  18. A replica technique for extracting precipitates from neutron-irradiated or thermal-aged vanadium alloys for TEM analysis

    Science.gov (United States)

    Fukumoto, K.; Iwasaki, M.

    2014-06-01

    A carbon replica technique has been developed to extract precipitates from vanadium alloys. Using this technique, precipitation phases can be extracted from neutron-irradiated or thermal-aged V-4Cr-4Ti alloys. Precipitate identification using EDS X-ray analysis and electron diffraction was facilitated. Only NaCl type of Ti(OCN) precipitate was formed in the thermal-aged V-4Cr-4Ti alloys at 600 °C for 20 h and cation sub-lattice was only occupied by Ti atoms. However, the thin plate of precipitates with NaCl type of crystallographic structure could be seen in the V-4Cr-4Ti alloys irradiated at 593 °C in the JOYO fast reactor. The precipitate contained chromium and vanadium atoms on the cation sub-lattice as well as titanium atoms. It is considered that the phase of MX type (M = Ti, V, Cr and X = O, N, C) is a metastable phase under neutron irradiation.

  19. Testing and linearity calibration of films of phenol compounds exposed to thermal neutron field for EPR dosimetry.

    Science.gov (United States)

    Gallo, S; Panzeca, S; Longo, A; Altieri, S; Bentivoglio, A; Dondi, D; Marconi, R P; Protti, N; Zeffiro, A; Marrale, M

    2015-12-01

    This paper reports the preliminary results obtained by Electron Paramagnetic Resonance (EPR) measurements on films of IRGANOX® 1076 phenols with and without low content (5% by weight) of gadolinium oxide (Gd2O3) exposed in the thermal column of the Triga Mark II reactor of LENA (Laboratorio Energia Nucleare Applicata) of Pavia (Italy). Thanks to their size, the phenolic films here presented are good devices for the dosimetry of beams with high dose gradient and which require accurate knowledge of the precise dose delivered. The dependence of EPR signal as function of neutron dose was investigated in the fluence range between 10(11) cm(-2) and 10(14) cm(-2). Linearity of EPR response was found and the signal was compared with that of commercial alanine films. Our analysis showed that gadolinium oxide (5% by weight) can enhance the thermal neutron sensitivity more than 18 times. Irradiated dosimetric films of phenolic compound exhibited EPR signal fading of about 4% after 10 days from irradiation. Copyright © 2015 Elsevier Ltd. All rights reserved.

  20. One-step fabrication of submicrostructures by low one-photon absorption direct laser writing technique with local thermal effect

    Science.gov (United States)

    Nguyen, Dam Thuy Trang; Tong, Quang Cong; Ledoux-Rak, Isabelle; Lai, Ngoc Diep

    2016-01-01

    In this work, local thermal effect induced by a continuous-wave laser has been investigated and exploited to optimize the low one-photon absorption (LOPA) direct laser writing (DLW) technique for fabrication of polymer-based microstructures. It was demonstrated that the temperature of excited SU8 photoresist at the focusing area increases to above 100 °C due to high excitation intensity and becomes stable at that temperature thanks to the use of a continuous-wave laser at 532 nm-wavelength. This optically induced thermal effect immediately completes the crosslinking process at the photopolymerized region, allowing obtain desired structures without using the conventional post-exposure bake (PEB) step, which is usually realized after the exposure. Theoretical calculation of the temperature distribution induced by local optical excitation using finite element method confirmed the experimental results. LOPA-based DLW technique combined with optically induced thermal effect (local PEB) shows great advantages over the traditional PEB, such as simple, short fabrication time, high resolution. In particular, it allowed the overcoming of the accumulation effect inherently existed in optical lithography by one-photon absorption process, resulting in small and uniform structures with very short lattice constant.

  1. Neutrons from Antiproton Irradiation

    DEFF Research Database (Denmark)

    Bassler, Niels; Holzscheiter, Michael; Petersen, Jørgen B.B.

    the neutron spectrum. Additionally, we used a cylindrical polystyrene loaded with several pairs of thermoluminescent detectors containing Lithium-6 and Lithium-7, which effectively detects thermalized neutrons. The obtained results are compared with FLUKA imulations. Results: The results obtained...

  2. LHC RadMon SRAM Detectors Used at Different Voltages to Determine the Thermal Neutron to High Energy Hadron Fluence Ratio

    CERN Document Server

    Kramer, D; Pignard, C; Brugger, M; Spiezia, G; Roeed, K; Klupak, V; Wijnands, T

    2011-01-01

    The thermal neutron SEU cross-section of the Toshiba SRAM memory used in the LHC RadMon system was measured at different voltages. A method using the difference in its response compared to mixed particle energy field is proposed to be used as a discriminator between thermal neutron and high-energy hadron fluences. For test purposes, the proposed method was used at the CNGS and CERF facilities to estimate the field composition by counting SEUs at two different voltages and the results were compared to simulations.

  3. Framing the performance of heat absorption/generation and thermal radiation in chemically reactive Darcy-Forchheimer flow

    Science.gov (United States)

    Hayat, T.; Shah, Faisal; Khan, Muhammad Ijaz; Alsaedi, A.

    The present work aims to report the consequences of heterogeneous-homogeneous reactions in Darcy-Forchheimer flow of Casson material bounded by a nonlinear stretching sheet of variable thickness. Nonlinear stretched surface with variable thickness is the main agent for MHD Darcy-Forchheimer flow. Impact of thermal radiation and non-uniform heat absorption/generation are also considered. Flow in porous space is characterized by Darcy-Forchheimer flow. It is assumed that the homogeneous process in ambient fluid is governed by first order kinetics and the heterogeneous process on the wall surface is given by isothermal cubic autocatalator kinetics. The governing nonlinear ordinary differential equations are solved numerically. Effects of physical variables such as thickness, Hartman number, inertia and porous, radiation, Casson, heat absorption/generation and homogeneous-heterogeneous reactions are investigated. The variations of drag force (skin friction) and heat transfer rate (Nusselt number) for different interesting variables are plotted and discussed.

  4. Study of atomic clusters in neutron irradiated reactor pressure vessel surveillance samples by extended X-ray absorption fine structure spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Cammelli, S. [LWV, NES, Paul Scherrer Institute, 5232 Villigen PSI (Switzerland); Fachbereich C - Physik, Bergische Universitaet Wuppertal, Gauss-Str. 20, 42097 Wuppertal (Germany)], E-mail: Sebastiano.cammelli@psi.ch; Degueldre, C.; Kuri, G.; Bertsch, J. [LWV, NES, Paul Scherrer Institute, 5232 Villigen PSI (Switzerland); Luetzenkirchen-Hecht, D.; Frahm, R. [Fachbereich C - Physik, Bergische Universitaet Wuppertal, Gauss-Str. 20, 42097 Wuppertal (Germany)

    2009-03-31

    Copper and nickel impurities in nuclear reactor pressure vessel (RPV) steel can form nano-clusters, which have a strong impact on the ductile-brittle transition temperature of the material. Thus, for control purposes and simulation of long irradiation times, surveillance samples are submitted to enhanced neutron irradiation. In this work, surveillance samples from a Swiss nuclear power plant were investigated by extended X-ray absorption fine structure spectroscopy (EXAFS). The density of Cu and Ni atoms determined in the first and second shells around the absorber is affected by the irradiation and temperature. The comparison of the EXAFS data at Cu and Ni K-edges shows that these elements reside in arrangements similar to bcc Fe. However, the EXAFS analysis reveals local irradiation damage in the form of vacancy fractions, which can be determined with a precision of {approx}5%. There are indications that the formation of Cu and Ni clusters differs significantly.

  5. On the effect of thermal treatment and hydrogen vibrational dynamics in sodium alanates: An inelastic neutron scattering study

    Energy Technology Data Exchange (ETDEWEB)

    Albinati, A., E-mail: Alberto.Albinati@unimi.it [Dipartimento di Chimica Strutturale e Stereochimica Inorganica, Universita degli Studi di Milano, via G. Venezian 21, 20133 Milan (Italy); Colognesi, D. [Consiglio Nazionale delle Ricerche, Istituto di Sistemi Complessi, via Madonna del Piano 10, 50019 Sesto Fiorentino (Finland) (Italy); Georgiev, P.A. [Dipartimento di Chimica Strutturale e Stereochimica Inorganica, Universita degli Studi di Milano, via G. Venezian 21, 20133 Milan (Italy); Jensen, C.M. [Department of Chemistry, University of Hawaii, Honolulu, HI 96822 (United States); Ramirez-Cuesta, A.J. [ISIS facility, Rutherford Appleton Laboratory, Chilton, Didcot OX11 0QX (United Kingdom)

    2012-05-15

    Highlights: Black-Right-Pointing-Pointer High resolution INS spectra of thermally treated NaAlH{sub 4} and Na{sub 3}AlH{sub 6}. Black-Right-Pointing-Pointer Detailed spectral features assignments based on high quality DFT(GGA) calculations. Black-Right-Pointing-Pointer Treated materials spectra are described as sum of the corresponding reactants and products. Black-Right-Pointing-Pointer The existence of AlH{sub 3} and AlH{sub 5}{sup 2-} species is not observed in the bulk, under equilibrium. - Abstract: We have measured inelastic neutron scattering (INS) spectra from Ti-doped polycrystalline alanates (NaAlH{sub 4} and Na{sub 3}AlH{sub 6}), at low temperature, in the energy transfer range 3-500 meV, both for thermally treated and untreated samples. From the spectral range corresponding to the fundamental vibrational bands of these aluminohydrides, accurate one-phonon spectra and hydrogen-projected densities of phonon states have been extracted and analyzed using ab initio lattice dynamics calculations. Satisfactory agreement has been found for the untreated samples. In the case of thermally treated samples, due to thermal decomposition, different ionic species are present and the sample composition could be quantitatively evaluated. No evidence for the existence of intermediate species such as AlH{sub 3} or AlH{sub 5}{sup 2-} has been found.

  6. Thermal stability, swelling behavior and CO 2 absorption properties of Nanoscale Ionic Materials (NIMs)

    KAUST Repository

    Andrew Lin, Kun-Yi

    2014-11-11

    © The Royal Society of Chemistry 2015. Nanoscale Ionic Materials (NIMs) consist of a nanoscale core, a corona of charged brushes tethered on the surface of the core, and a canopy of the oppositely charged species linked to the corona. Unlike conventional polymeric nanocomposites, NIMs can display liquid-like behavior in the absence of solvents, have a negligible vapor pressure and exhibit unique solvation properties. These features enable NIMs to be a promising CO2 capture material. To optimize NIMs for CO2 capture, their structure-property relationships were examined by investigating the roles of the canopy and the core in their thermal stability, and thermally- and CO2-induced swelling behaviors. NIMs with different canopy sizes and core fractions were synthesized and their thermal stability as well as thermally- and CO2-induced swelling behaviors were determined using thermogravimetry, and ATR FT-IR and Raman spectroscopies. It was found that the ionic bonds between the canopy and the corona, as well as covalent bonds between the corona and the core significantly improved the thermal stability compared to pure polymer and polymer/nanofiller mixtures. A smaller canopy size and a larger core fraction led to a greater enhancement in thermal stability. This thermal stability enhancement was responsible for the long-term thermal stability of NIMs over 100 temperature swing cycles. Owing to their ordered structure, NIMs swelled less when heated or when they adsorbed CO2 compared to their corresponding polymers. This journal is

  7. Decay and termite resistance, water absorption and swelling of thermally compressed wood panels

    Science.gov (United States)

    Oner Unsal; S. Nami Kartal; Zeki Candan; Rachel A. Arango; Carol A. Clausen; Frederick Green

    2009-01-01

    This study evaluated decay and termite resistance of thermally compressed pine wood panels under pressure at either 5 or 7 MPa and either 120 or 150 °C for 1 h. Wood specimens from the panels were exposed to laboratory decay resistance by using the wood degrading fungi, Gloeophyllum trabeum and Trametes versicolor. The thermal compression process caused increases in...

  8. Thermal-neutron capture gamma rays from natural magnesium and enriched 25Mg

    NARCIS (Netherlands)

    Spilling, P.; Gruppelaar, H.; Kamp, A.M.F. op den

    1967-01-01

    Gamma rays from neutron capture in natural magnesium and in enriched 25Mg have been studied with Ge(Li) detectors. Altogether 101 γ-rays have been observed. Most of these γ-rays could be fitted into the level schemes of 25Mg, 26Mg and 27Mg. If it is assumed that the capture cross section for

  9. Possibilities of the short-term thermal and epithermal neutron activation for analysis of macromycetes (mushrooms)

    Czech Academy of Sciences Publication Activity Database

    Řanda, Zdeněk; Soukal, Ladislav; Mizera, Jiří

    2005-01-01

    Roč. 264, č. 1 (2005), s. 67-76 ISSN 0236-5731 R&D Projects: GA AV ČR IAA3048201 Institutional research plan: CEZ:AV0Z10480505 Keywords : neutron activation analysis * epithermal NAA * mushrooms * macromycetes Subject RIV: CB - Analytical Chemistry, Separation Impact factor: 0.460, year: 2005

  10. Irreversibility analysis of hydrogen separation schemes in thermochemical cycles. [Condensation, physical absorption, diffusion, physical adsorption, thermal adsorption, and electrochemical separation

    Energy Technology Data Exchange (ETDEWEB)

    Cox, K.E.

    1978-01-01

    Six processes have been evaluated as regards irreversibility generation for hydrogen separation from binary gas mixtures. The results are presented as a series of plots of separation efficiency against the mol fraction hydrogen in the feed gas. Three processes, condensation, physical absorption and electrochemical separation indicate increasing efficiency with hydrogen content. The other processes, physical and thermal adsorption, and diffusion show maxima in efficiency at a hydrogen content of 50 mol percent. Choice of separation process will also depend on such parameters as condition of feed, impurity content and capital investment. For thermochemical cycles, schemes based on low temperature heat availability are preferable to those requiring a work input.

  11. Three-dimensional flow of an oldroyd-B fluid with variable thermal conductivity and heat generation/absorption.

    Directory of Open Access Journals (Sweden)

    Sabir Ali Shehzad

    Full Text Available This paper looks at the series solutions of three dimensional boundary layer flow. An Oldroyd-B fluid with variable thermal conductivity is considered. The flow is induced due to stretching of a surface. Analysis has been carried out in the presence of heat generation/absorption. Homotopy analysis is implemented in developing the series solutions to the governing flow and energy equations. Graphs are presented and discussed for various parameters of interest. Comparison of present study with the existing limiting solution is shown and examined.

  12. Beam neutron energy optimization for boron neutron capture therapy using Monte Carlo method

    Directory of Open Access Journals (Sweden)

    Ali Pazirandeh

    2006-06-01

    Full Text Available  In last two decades the optimal neutron energy for the treatment of deep seated tumors in boron neutron capture therapy in view of neutron physics and chemical compounds of boron carrier has been under thorough study. Although neutron absorption cross section of boron is high (3836b, the treatment of deep seated tumors such as gliobelastoma multiform (GBM requires beam of neutrons of higher energy that can penetrate deeply into the brain and thermalize in the proximity of the tumor. Dosage from recoil proton associated with fast neutrons however poses some constraints on maximum neutron energy that can be used in the treatment. For this reason neutrons in the epithermal energy range of 10eV-10keV are generally to be the most appropriate. The simulation carried out by Monte Carlo methods using MCBNCT and MCNP4C codes along with the cross section library in 290 groups extracted from ENDF/B6 main library. The optimal neutron energy for deep seated tumors depends on the size and depth of tumor. Our estimated optimized energy for the tumor of 5cm wide and 1-2cm thick stands at 5cm depth is in the range of 3-5keV

  13. THERMAL NEUTRON FLUX MAPPING ON A TARGET CAPSULE AT RABBIT FACILITY OF RSG-GAS REACTOR FOR USE IN k0-INAA

    Directory of Open Access Journals (Sweden)

    Sutisna Sutisna

    2015-03-01

    Full Text Available Instrumental neutron activation analysis based on the k0 method (k0-INAA requires the availability of the accurate reactor parameter data, in particular a thermal neutron flux that interact with a targets inside the target capsule. This research aims to determine and map the thermal neutron flux inside the capsule and irradiation channels used for the elemental quantification using the k0-AANI. Mapping of the thermal neutron flux (фth on two type of irradiation capsule have been done for RS01 and RS02 facilities of RSG-GAS reactor. Thermal neutron flux determined using Al-0,1%Au alloy through 197Au(n,g 198Au nuclear reaction, while the flux mapping done using statistics R. Thermal neutron flux are calculated using k0-IAEA software provided by IAEA. The results showed the average thermal neutron flux is (5.6±0.3×10+13 n.cm-2.s-1; (5.6±0.4×10+13 n.cm-2.s-1; (5.2±0.4×10+13 n.cm-2.s-1 and (5.3±0.4×10+13 n.cm-2.s-1 for Polyethylene capsule of 1st , 2nd, 3rd and 4th layer respectively. In the case of Aluminum capsule, the thermal neutron flux was lower compared to that on Polyethylene capsule. There were (3.0±0.2×10+13 n.cm-2.s-1; (2.8±0.1×10+13 n.cm-2.s-1; (3.2±0.3×10+13 n.cm-2.s-1 for 1st, 2nd and 3rd layers respectively. For each layer in the capsule, the thermal neutron flux is not uniform and it was no degradation flux in the axial direction, both for polyethylene and aluminum capsules. Contour map of eight layer on polyethylene capsule and six layers on aluminum capsule for RS01 and RS02 irradiation channels had a similar pattern with a small diversity for all type of the irradiation capsule. Keywords: thermal neutron, flux, capsule, NAA   Analisis aktivasi neutron instrumental berbasis metode k0 (k0-AANI memerlukan ketersediaan data parameter reaktor yang akurat, khususnya data fluks neutron termal yang berinteraksi dengan inti sasaran di dalam kapsul target. Penelitian ini bertujuan menentukan dan memetakan fluks neutron termal

  14. Thermal and resonance neutrons generated by various electron and X-ray therapeutic beams from medical linacs installed in polish oncological centers

    Science.gov (United States)

    Konefał, Adam; Orlef, Andrzej; Łaciak, Marcin; Ciba, Aleksander; Szewczuk, Marek

    2012-01-01

    Background High-energy photon and electron therapeutic beams generated in medical linear accelerators can cause the electronuclear and photonuclear reactions in which neutrons with a broad energy spectrum are produced. A low-energy component of this neutron radiation induces simple capture reactions from which various radioisotopes originate and in which the radioactivity of a linac head and various objects in the treatment room appear. Aim The aim of this paper is to present the results of the thermal/resonance neutron fluence measurements during therapeutic beam emission and exemplary spectra of gamma radiation emitted by medical linac components activated in neutron reactions for four X-ray beams and for four electron beams generated by various manufacturers’ accelerators installed in typical concrete bunkers in Polish oncological centers. Materials and methods The measurements of neutron fluence were performed with the use of the induced activity method, whereas the spectra of gamma radiation from decays of the resulting radioisotopes were measured by means of a portable high-purity germanium detector set for field spectroscopy. Results The fluence of thermal neutrons as well as resonance neutrons connected with the emission of a 20 MV X-ray beam is ∼106 neutrons/cm2 per 1 Gy of a dose in water at a reference depth. It is about one order of magnitude greater than that for the 15 MV X-ray beams and about two orders of magnitude greater than for the 18–22 MeV electron beams regardless of the type of an accelerator. Conclusion The thermal as well as resonance neutron fluence depends strongly on the type and the nominal potential of a therapeutic beam. It is greater for X-ray beams than for electrons. The accelerator accessories and other large objects should not be stored in a treatment room during high-energy therapeutic beam emission to avoid their activation caused by thermal and resonance neutrons. Half-lives of the radioisotopes originating from

  15. High Ultraviolet Absorption in Colloidal Gallium Nanoparticles Prepared from Thermal Evaporation

    Directory of Open Access Journals (Sweden)

    Flavio Nucciarelli

    2017-07-01

    Full Text Available New methods for the production of colloidal Ga nanoparticles (GaNPs are introduced based on the evaporation of gallium on expendable aluminum zinc oxide (AZO layer. The nanoparticles can be prepared in aqueous or organic solvents such as tetrahydrofuran in order to be used in different sensing applications. The particles had a quasi mono-modal distribution with diameters ranging from 10 nm to 80 nm, and their aggregation status depended on the solvent nature. Compared to common chemical synthesis, our method assures higher yield with the possibility of tailoring particles size by adjusting the deposition time. The GaNPs have been studied by spectrophotometry to obtain the absorption spectra. The colloidal solutions exhibit strong plasmonic absorption in the ultra violet (UV region around 280 nm, whose width and intensity mainly depend on the nanoparticles dimensions and their aggregation state. With regard to the colloidal GaNPs flocculate behavior, the water solvent case has been investigated for different pH values, showing UV-visible absorption because of the formation of NPs clusters. Using discrete dipole approximation (DDA method simulations, a close connection between the UV absorption and NPs with a diameter smaller than ~40 nm was observed.

  16. Integrated CO2, humidity and thermal control by membrane gas absorption

    NARCIS (Netherlands)

    Eckhard, F.; Feron, P.H.M.; Jacobs, P.; Savage, Ch.; Witt, J.

    1999-01-01

    In three consecutive studies the use of membrane gas absorption for the recovery of CO2, water vapour and heat has been studied by Stork and the TNO Institute of Environmental Sciences, Energy Research and Process Innovation. This work has financially been supported by ESA and the Dutch national

  17. Edge localized modes of cold neutrons in periodic condensed media

    Science.gov (United States)

    Belyakov, V. A.

    2017-06-01

    It is found that for certain energies of discreet cold neutrons, quasi-stationary eigen solutions of the corresponding Schrodinger equation, which are localized in the layer of a periodic medium, exist. The localization time of these solutions is strongly dependent on the layer thickness, being finite for a finite layer thickness and increasing indefinitely upon a infinite growth of the layer thickness as the third power of the layer thickness. The problem has been solved in the two-wave approximation of the dynamic diffraction theory for the neutron propagation direction coinciding with the periodicity axes (normal incidence of the neutron beam on the layer). The expressions for neutron eigenwave functions in a periodic medium, the reflection and transmission coefficients, and the neutron wavefunction in the layer as a function of the neutron energy incident on the layer have been determined. It turns out that for the certain discrete neutron energies, the amplitudes of the neutron wavefunction in the layer reach sharp maxima. The corresponding energies are just outside of the neutron stop band (energies forbidden for neutron propagation in the layer) and determine the energies of neutron edge modes (NEMs) localized in the layer, which are direct analogs of the optical edge modes for photonic crystals. The dispersion equation for the localized neutron edge modes has been obtained and analytically solved for the case of thick layers. A rough estimate for the localization length L is L ( db N)-1, where b is the neutron scattering length, d is the crystal period, and N is the density of nuclei in the crystal. The estimates of the localized thermal neutron lifetime show that acheaving of a lifetime close to the free neutron lifetime seems nonrealistic due to absorption of thermal neutrons and requires a perfect large size crystal. Nevertheless, acheaving the localized neutron lifetime exceeding by 104 times the neutron time of flight through the layer appears as

  18. Last Improvements of the CALMOS Calorimeter Dedicated to Thermal Neutron Flux and Nuclear Heating Measurements inside the OSIRIS Reactor

    Science.gov (United States)

    Carcreff, H.; Salmon, L.; Lepeltier, V.; Guyot, J. M.; Bouard, E.

    2018-01-01

    Nuclear heating inside an MTR reactor needs to be known in order to design and to run irradiation experiments which have to fulfill target temperature constraints. To improve the nuclear heating knowledge, an innovative calorimetric system CALMOS has been studied, manufactured and tested for the 70MWth OSIRIS reactor operated by CEA. This device is based on a mobile calorimetric probe which can be inserted in any in-core experimental location and can be moved axially from the bottom of the core to 1000 mm above the core mid-plane. Obtained results and advantages brought by the first CALMOS-1 equipment have been already presented. However, some difficulties appeared with this first version. A thermal limitation in cells did not allow to monitor nuclear heating up to the 70 MW nominal power, and some significant discrepancies were observed at high heating rates between results deduced from the calibration and those obtained by the "zero method". Taking this feedback into account, the new CALMOS-2 calorimeter has been designed both for extending the heating range up to 13W.g-1 and for improving the "zero method" measurement thanks to the implementation of a 4-wires technique. In addition, the new calorimeter has been designed as a real operational measurement system, well suited to characterize and to follow the radiation field evolution throughout the reactor cycle. To meet this requirement, a programmable system associated with a specific software allows automatic complete cell mobility in the core, the data acquisition and the measurements processing. This paper presents the analysis of results collected during the 2015 comprehensive measurement campaign. The 4-wires technique was tested up to around a 4 W.g-1 heating level and allowed to quantify discrepancies between "zero" and calibration methods. Thermal neutron flux and nuclear heating measurements from CALMOS-1 and CALMOS-2 are compared. Thermal neutron flux distributions, obtained with the Self-Power Neutron

  19. Last Improvements of the CALMOS Calorimeter Dedicated to Thermal Neutron Flux and Nuclear Heating Measurements inside the OSIRIS Reactor

    Directory of Open Access Journals (Sweden)

    Carcreff H.

    2018-01-01

    Full Text Available Nuclear heating inside an MTR reactor needs to be known in order to design and to run irradiation experiments which have to fulfill target temperature constraints. To improve the nuclear heating knowledge, an innovative calorimetric system CALMOS has been studied, manufactured and tested for the 70MWth OSIRIS reactor operated by CEA. This device is based on a mobile calorimetric probe which can be inserted in any in-core experimental location and can be moved axially from the bottom of the core to 1000 mm above the core mid-plane. Obtained results and advantages brought by the first CALMOS-1 equipment have been already presented. However, some difficulties appeared with this first version. A thermal limitation in cells did not allow to monitor nuclear heating up to the 70 MW nominal power, and some significant discrepancies were observed at high heating rates between results deduced from the calibration and those obtained by the “zero method”. Taking this feedback into account, the new CALMOS-2 calorimeter has been designed both for extending the heating range up to 13W.g-1 and for improving the “zero method” measurement thanks to the implementation of a 4-wires technique. In addition, the new calorimeter has been designed as a real operational measurement system, well suited to characterize and to follow the radiation field evolution throughout the reactor cycle. To meet this requirement, a programmable system associated with a specific software allows automatic complete cell mobility in the core, the data acquisition and the measurements processing. This paper presents the analysis of results collected during the 2015 comprehensive measurement campaign. The 4-wires technique was tested up to around a 4 W.g-1 heating level and allowed to quantify discrepancies between “zero” and calibration methods. Thermal neutron flux and nuclear heating measurements from CALMOS-1 and CALMOS-2 are compared. Thermal neutron flux distributions

  20. Fluence to Hp(3) conversion coefficients for neutrons from thermal to 15 MeV.

    Science.gov (United States)

    Gualdrini, G; Ferrari, P; Tanner, R

    2013-12-01

    The recent statement on tissue reactions issued by the International Commission on Radiological Protection in April 2011 recommends a very significant reduction in the equivalent dose annual limit for the eye lens from 150 to 20 mSv y(-1); this has stimulated a lot of interest in eye lens dosimetry in the radiation protection community. Until now no conversion coefficients were available for the operational quantity Hp(3) for neutrons. The scope of the present work was to extend previous evaluations of H*(10) and Hp(10) performed at the PTB in 1995 to provide also Hp(3) data for neutrons. The present work is also intended to complete the studies carried out on photons during the last 4 y within the European Union-funded ORAMED (optimisation of radiation protection for medical staff) project.

  1. Methodology for Estimating Thermal and Neutron Embrittlement of Cast Austenitic Stainless Steels During Service in Light Water Reactors

    Energy Technology Data Exchange (ETDEWEB)

    Chopra, O. K.; Rao, A. S.

    2016-04-28

    Cast austenitic stainless steel (CASS) materials, which have a duplex structure consisting of austenite and ferrite phases, are susceptible to thermal embrittlement during reactor service. In addition, the prolonged exposure of these materials, which are used in reactor core internals, to neutron irradiation changes their microstructure and microchemistry, and these changes degrade their fracture properties even further. This paper presents a revision of the procedure and correlations presented in NUREG/CR-4513, Rev. 1 (Aug. 1994) for predicting the change in fracture toughness and tensile properties of CASS components due to thermal aging during service in light water reactors (LWRs) at 280–330 °C (535–625 °F). The methodology is applicable to CF-3, CF-3M, CF-8, and CF-8M materials with a ferrite content of up to 40%. The fracture toughness, tensile strength, and Charpy-impact energy of aged CASS materials are estimated from known material information. Embrittlement is characterized in terms of room-temperature (RT) Charpy-impact energy. The extent or degree of thermal embrittlement at “saturation” (i.e., the minimum impact energy that can be achieved for a material after long-term aging) is determined from the chemical composition of the material. Charpy-impact energy as a function of the time and temperature of reactor service is estimated from the kinetics of thermal embrittlement, which are also determined from the chemical composition. The fracture toughness J-R curve for the aged material is then obtained by correlating RT Charpy-impact energy with fracture toughness parameters. A common “predicted lower-bound” J-R curve for CASS materials of unknown chemical composition is also defined for a given grade of material, range of ferrite content, and temperature. In addition, guidance is provided for evaluating the combined effects of thermal and neutron embrittlement of CASS materials used in the reactor core internal components. The correlations

  2. Investigation of thermally induced anion disorder in fluorites using neutron scattering techniques

    DEFF Research Database (Denmark)

    Hutchings, M T; Clausen, Kurt Nørgaard; Dickens, M H

    1984-01-01

    the coherent diffuse quasielastic neutron scattering from single crystals of three such fluorite compounds PbF2, SrCl2 and CaF2, was investigated. The diffuse scattering intensity, and its energy width, increases with temperature into the fast-ion phase, and when integrated over energy transfer the intensity...... anion Frenkel interstitials, anion vacancies and relaxed anions has been developed which satisfactorily accounts for the distribution of intensity....

  3. Thermal neutron capture cross section for Fe-56(n,gamma)

    Czech Academy of Sciences Publication Activity Database

    Firestone, R. B.; Belgya, T.; Krtička, M.; Bečvář, F.; Szentmiklosi, L.; Tomandl, Ivo

    2017-01-01

    Roč. 95, č. 1 (2017), č. článku 014328. ISSN 2469-9985 R&D Projects: GA ČR GA13-07117S; GA MŠk LM2015056 Institutional support: RVO:61389005 Keywords : neutron cross section * gamma gamma-coincidence data Subject RIV: BG - Nuclear, Atomic and Molecular Physics, Colliders Impact factor: 3.820, year: 2016

  4. Application of hydrogel system for neutron attenuation

    CERN Document Server

    Gupta, S C; Gupta, B P

    2000-01-01

    Hydrogel sheets based on poly(vinyl alcohol) (PVA) and poly(vinyl acetate) (PVAc) have been prepared by the technique of acetalization of PVA using formaldehyde and grafting of acrylic acid onto PVAc by gamma irradiation. PVA hydrogel (PVAB) sheets have been prepared in geometrically stable shapes by compression moulding process and characterised for their thermal properties, geometrical stability on water absorption, and neutron shielding efficiency. The effective protection from fast neutrons can be increased by a factor of 18% by swelling the PVAB sheets to 210% in water. The water intake and subsequent retention of water by the sheet can be tailored as per shielding requirements.

  5. Detection of plastic explosives using thermal neutron radiography; Deteccao de explosivos plasticos por neutrongrafia termica

    Energy Technology Data Exchange (ETDEWEB)

    Hacidume, Leo Ryoske

    1999-12-01

    The work aims to demonstrate the potentiality of the neutron radiography technique, allied to the computerized tomography by transmission, to both detect and visualize plastic explosive samples in several hidden conditions, using a simple scanner as a digitalisation instrument. Each tomographic essay was obtained in the J-9 channel of the Argonauta Research Reactor of IEN/CNEN, in groups of six neutron radiographic projections, performed with an angular increment of 30 deg C, in a period of time of 30 minutes for each projection. Two groups of tomographic reconstructions were generated, distinguished by the digitalisation process of the interested lines in the reconstruction plane coming from the projection groups, utilization a scanner and a microdensitometer, respectively. The reconstruction of the bi-dimensional image of the transverse section, in relation to this plane, was processed making use of the Image Reconstruction Algorithmic of an Image based on the Maximum Entropy principle (ARIEM). From the qualitative analysis of the images, we conclude that the neutron radiographic system was able to detect the explosive sample in a satisfactory way while the quantitative analysis confirmed the application effectiveness of a scanner to acquire the projection dates whose objective is only a reconnaissance. (author)

  6. A study of Gd-based parallel plate avalanche counter for thermal neutrons by MC simulation

    Energy Technology Data Exchange (ETDEWEB)

    Rhee, J.T.; Kim, H.G. [IAP, High Energy Physics Lab, Department of Physics, Konkuk University, Seoul 143-701 (Korea, Republic of); Ahmad, Farzana; Jeon, Y.J. [Liquid Crystal Research Center, Department of Chemistry, Konkuk University, Seoul 143-701 (Korea, Republic of); Jamil, M., E-mail: mjamil@konkuk.ac.kr [IAP, High Energy Physics Lab, Department of Physics, Konkuk University, Seoul 143-701 (Korea, Republic of); Division of International Studies, University College, Konkuk University, Seoul 143-701 (Korea, Republic of)

    2013-12-21

    In this work, we demonstrate the feasibility and characteristics of a single-gap parallel plate avalanche counter (PPAC) as a low energy neutron detector, based on Gd-converter coating. Upon falling on the Gd-converter surface, the incident low energy neutrons produce internal conversion electrons which are evaluated and detected. For estimating the performance of the Gd-based PPAC, a simulation study has been performed using GEANT4 Monte Carlo (MC) code. The detector response as a function of incident neutron energies in the range of 25–100 meV has been evaluated with two different physics lists. Using the QGSP{sub B}IC{sub H}P physics list and assuming 5μm converter thickness, 11.8%, 18.48%, and 30.28% detection efficiencies have been achieved for the forward-, the backward-, and the total response of the converter-based PPAC. On the other hand, considering the same converter thickness and detector configuration, with the QGSP{sub B}ERT{sub H}P physics list efficiencies of 12.19%, 18.62%, and 30.81%, respectively, were obtained. These simulation results are briefly discussed.

  7. Inelastic neutron scattering and lattice dynamical calculation of negative thermal expansion in HfW2O8

    Science.gov (United States)

    Mittal, R.; Chaplot, S. L.; Kolesnikov, A. I.; Loong, C.-K.; Mary, T. A.

    2003-08-01

    The compounds ZrW2O8 and HfW2O8 undergo large isotropic negative thermal expansion (NTE) over a wide range of temperatures up to 1443 K and 1050 K, respectively. We have showed previously that large softening of low-energy phonons in ZrW2O8 is responsible for its anomalous thermal expansion behavior. In order to understand the effect of replacing Zr by Hf on NTE behavior we report lattice dynamical calculations and neutron time-of-flight spectroscopic measurements of the phonon density of states for cubic HfW2O8. The calculated phonon spectrum for cubic HfW2O8 is in fair agreement with the experimental data. The phonon spectra in the Zr and Hf compounds differ at low energies largely due to the mass difference. The calculated negative thermal expansion for HfW2O8 is in good agreement with experimental data from the literature. We further report a calculation of the pressure dependence of the detailed phonon dispersion relation which reveals large softening of several phonon branches on compression associated with the NTE.

  8. Numerical research on the neutronic/thermal-hydraulic/mechanical coupling characteristics of the optimized helium cooled solid breeder blanket for CFETR

    Energy Technology Data Exchange (ETDEWEB)

    Cui, Shijie; Zhang, Dalin, E-mail: dlzhang@mail.xjtu.edu.cn; Cheng, Jie; Tian, Wenxi; Su, G.H.

    2017-01-15

    As one of the candidate tritium breeding blankets for Chinese Fusion Engineering Test Reactor (CFETR), a conceptual structure of the helium cooled solid breeder blanket has recently been proposed. The neutronic, thermal-hydraulic and mechanical characteristics of the blanket directly affect its tritium breeding and safety performance. Therefore, neutronic/thermal-hydraulic/mechanical coupling analyses are of vital importance for a reliable blanket design. In this work, first, three-dimensional neutronics analysis and optimization of the typical outboard equatorial blanket module (No. 12) were performed for the comprehensive optimal scheme. Then, thermal and fluid dynamic analyses of the scheme under both normal and critical conditions were performed and coupled with the previous neutronic calculation results. With thermal-hydraulic boundaries, thermo-mechanical analyses of the structure materials under normal, critical and blanket over-pressurization conditions were carried out. In addition, several parametric sensitivity studies were also conducted to investigate the influences of the main parameters on the blanket temperature distributions. In this paper, the coupled analyses verify the reasonability of the optimized conceptual design preliminarily and can provide an important reference for the further analysis and optimization design of the CFETR helium cooled solid breeder blanket.

  9. The Numerical Nuclear Reactor for High-Fidelity Integrated Simulation of Neutronic, Thermal-Hydraulic, and Thermo-Mechanical Phenomena

    Energy Technology Data Exchange (ETDEWEB)

    Kim, K. S.; Ju, H. G.; Jeon, T. H. and others

    2005-03-15

    A comprehensive high fidelity reactor core modeling capability has been developed for detailed analysis of current and advanced reactor designs as part of a US-ROK collaborative I-NERI project. High fidelity was accomplished by integrating highly refined solution modules for the coupled neutronic, thermal-hydraulic, and thermo-mechanical phenomena. Each solution module employs methods and models that are formulated faithfully to the first-principles governing the physics, real geometry, and constituents. Specifically, the critical analysis elements that are incorporated in the coupled code capability are whole-core neutron transport solution, ultra-fine-mesh computational fluid dynamics/heat transfer solution, and finite-element-based thermo-mechanics solution, all obtained with explicit (fuel pin cell level) heterogeneous representations of the components of the core. The vast computational problem resulting from such highly refined modeling is solved on massively parallel computers, and serves as the 'numerical nuclear reactor'. Relaxation of modeling parameters were also pursued to make problems run on clusters of workstations and PCs for smaller scale applications as well.

  10. Transient cases analyses of the TRIGA IPR-R1 using thermal hydraulic and neutron kinetic coupled codes

    Energy Technology Data Exchange (ETDEWEB)

    Reis, Patricia A.L.; Costa, Antonella L.; Pereira, Claubia; Veloso, Maria A.F.; Scari, Maria E., E-mail: patricialire@yahoo.com.br, E-mail: antonella@nuclear.ufmg.br, E-mail: claubia@nuclear.ufmg.br, E-mail: dora@nuclear.ufmg.br, E-mail: melizabethscari@yahoo.com [Universidade Federal de Minas Gerais (UFMG), Belo Horizonte, MG (Brazil). Departamento de Engenharia Nuclear; Instituto Nacional de Ciencias e Tecnologia de Reatores Nucleares Inovadores (INCT/CNPq), Belo Horizonte (Brazil); Miro, Rafael; Verdu, Gumersindo, E-mail: rmiro@iqn.upv.es, E-mail: gverdu@iqn.upv.es [Universidad Politecnica de Valencia (Spain). Departamento de Ingenieria Quimica y Nuclear

    2015-07-01

    Simulations and analyses of nuclear reactors have been improved by utilization of coupled thermal-hydraulic (TH) and neutron kinetics (NK) system codes especially to simulate transients that involve strong feedback effects between NK and TH. The TH-NK coupling technique was initially developed and used to simulate the behavior of power reactors; however, several coupling methodologies are now being applied for research reactors. This work presents the coupling methodology application between RELAP5 and PARCS codes using as a model the TRIGA IPR-R1 research reactor. Analyses of steady state and transient conditions and comparisons with results from simulations using only the RELAP5 code are being presented in this paper. (author)

  11. Zinc absorption from milk is affected by dilution but not by thermal processing, and milk enhances absorption of Zinc from high-phytate rice in young dutch women

    NARCIS (Netherlands)

    Talsma, Elise F.; Moretti, Diego; Ly, Sou Chheng; Dekkers, Renske; Heuvel, van den Ellen G.H.M.; Fitri, Aditia; Boelsma, Esther; Stomph, Tjeerd Jan; Zeder, Christophe; Melse-Boonstra, Alida

    2017-01-01

    Background: Milk has been suggested to increase zinc absorption. The effect of processing and the ability of milk to enhance zinc absorption from other foods has not been measured directly in humans. Objective: We aimed to assess zinc absorption from 1) milk undergoing various processing and

  12. Molybdenum-99-producing 37-element fuel bundle neutronically and thermal-hydraulically equivalent to a standard CANDU fuel bundle

    Energy Technology Data Exchange (ETDEWEB)

    Nichita, E., E-mail: Eleodor.Nichita@uoit.ca; Haroon, J., E-mail: Jawad.Haroon@uoit.ca

    2016-10-15

    Highlights: • A 37-element fuel bundle modified for {sup 99}Mo production in CANDU reactors is presented. • The modified bundle is neutronically and thermal-hydraulically equivalent to the standard bundle. • The modified bundle satisfies all safety criteria satisfied by the standard bundle. - Abstract: {sup 99m}Tc, the most commonly used radioisotope in diagnostic nuclear medicine, results from the radioactive decay of {sup 99}Mo which is currently being produced at various research reactors around the globe. In this study, the potential use of CANDU power reactors for the production of {sup 99}Mo is investigated. A modified 37-element fuel bundle, suitable for the production of {sup 99}Mo in existing CANDU-type reactors is proposed. The new bundle is specifically designed to be neutronically and thermal-hydraulically equivalent to the standard 37-element CANDU fuel bundle in normal, steady-state operation and, at the same time, be able to produce significant quantities of {sup 99}Mo when irradiated in a CANDU reactor. The proposed bundle design uses fuel pins consisting of a depleted-uranium centre surrounded by a thin layer of low-enriched uranium. The new molybdenum-producing bundle is analyzed using the lattice transport code DRAGON and the diffusion code DONJON. The proposed design is shown to produce 4081 six-day Curies of {sup 99}Mo activity per bundle when irradiated in the peak-power channel of a CANDU core, while maintaining the necessary reactivity and power rating limits. The calculated {sup 99}Mo yield corresponds to approximately one third of the world weekly demand. A production rate of ∼3 bundles per week can meet the global demand of {sup 99}Mo.

  13. New fit of thermal neutron constants (TNC for 233,235U, 239,241Pu and 252Cf(sf: Microscopic vs. maxwellian data

    Directory of Open Access Journals (Sweden)

    Pronyaev Vladimir G.

    2017-01-01

    Full Text Available An IAEA project to update the Neutron Standards is near completion. Traditionally, the Thermal Neutron Constants (TNC evaluated data by Axton for thermal-neutron scattering, capture and fission on four fissile nuclei and the total nu-bar of 252Cf(sf are used as input in the combined least-square fit with neutron cross section standards. The evaluation by Axton (1986 was based on a least-square fit of both thermal-spectrum averaged cross sections (Maxwellian data and microscopic cross sections at 2200 m/s. There is a second Axton evaluation based exclusively on measured microscopic cross sections at 2200 m/s (excluding Maxwellian data. Both evaluations disagree within quoted uncertainties for fission and capture cross sections and total multiplicities of uranium isotopes. There are two factors, which may lead to such difference: Westcott g-factors with estimated 0.2% uncertainties used in the Axton's fit, and deviation of the thermal spectra from Maxwellian shape. To exclude or mitigate the impact of these factors, a new combined GMA fit of standards was undertaken with Axton's TNC evaluation based on 2200 m/s data used as a prior. New microscopic data at the thermal point, available since 1986, were added to the combined fit. Additionally, an independent evaluation of TNC was undertaken using CONRAD code. Both GMA and CONRAD results are consistent within quoted uncertainties. New evaluation shows a small increase of fission and capture thermal cross sections, and a corresponding decrease in evaluated thermal nubar for uranium isotopes and 239Pu.

  14. Accuracy and Efficiency of a Coupled Neutronics and Thermal Hydraulics Model

    Energy Technology Data Exchange (ETDEWEB)

    Vincent A. Mousseau; Michael A. Pope

    2007-09-01

    The accuracy requirements for modern nuclear reactor simulation are steadily increasing due to the cost and regulation of relevant experimental facilities. Because of the increase in the cost of experiments and the decrease in the cost of simulation, simulation will play a much larger role in the design and licensing of new nuclear reactors. Fortunately as the work load of simulation increases, there are better physics models, new numerical techniques, and more powerful computer hardware that will enable modern simulation codes to handle the larger workload. This manuscript will discuss a numerical method where the six equations of two-phase flow, the solid conduction equations, and the two equations that describe neutron diffusion and precursor concentration are solved together in a tightly coupled, nonlinear fashion for a simplified model of a nuclear reactor core. This approach has two important advantages. The first advantage is a higher level of accuracy. Because the equations are solved together in a single nonlinear system, the solution is more accurate than the traditional “operator split” approach where the two-phase flow equations are solved first, the heat conduction is solved second and the neutron diffusion is solved third, limiting the temporal accuracy to 1st order because the nonlinear coupling between the physics is handled explicitly. The second advantage of the method described in this manuscript is that the time step control in the fully implicit system can be based on the timescale of the solution rather than a stability-based time step restriction like the material Courant. Results are presented from a simulated control rod movement and a rod ejection that address temporal accuracy for the fully coupled solution and demonstrate how the fastest timescale of the problem can change between the state variables of neutronics, conduction and two-phase flow during the course of a transient.

  15. The nuclear charge distribution of fission products of thermal neutron induced fission of /sup 235/U

    CERN Document Server

    Wollnik, H; Greif, J; Siegert, G

    1976-01-01

    Nuclear charge distributions of mass separated light fission products, 79neutron odd-even effect is found which results in periodical variations of the average nuclear charge, the variance, the skewness, and the excess. The principles of the variations of the nuclear charge distributions due to varying kinetic energies are discussed. (20 refs).

  16. The Development of a Neutron Evaporation Theory Code for the Thermal Fission of Uranium-235

    Science.gov (United States)

    1985-05-03

    Counter i The more recent research on the prompt neutron energy spectrum has been performed by David G. Madland and J. Rayford N1x, at Los ••V-- m u...Coryell, Charles D. and Nathan Sugarman , Editors; McGraw-Hill Book Co., New York, 1951. 5. Friedlander, Gerhart, et al., Nuclear and Radiochemistry...Fission Products, Coryell, Charles D., and Nathan Sugarman , Editors; McGraw-Hill Book co., New York, 1951. 8. Evans, Robley, D., The Atomic Nucleus

  17. Measurement of the effective thermal cross section of {sup 134}Cs by triple neutron capture reaction

    Energy Technology Data Exchange (ETDEWEB)

    Nakamura, Shoji; Harada, Hideo; Katoh, Toshio [Power Reactor and Nuclear Fuel Development Corp., Tokai, Ibaraki (Japan). Tokai Works; Hatsukawa, Yuichi; Shinohara, Nobuo; Hata, Kentaro; Kobayashi, Katsutoshi; Motoishi, Shoji; Tanase, Masakazu

    1998-03-01

    The effective thermal cross section ({sigma}{sub eff}) of the {sup 134}Cs(n,{gamma}){sup 135}Cs reaction was measured by the activation method and the {gamma}-ray spectroscopic method in order to obtain fundamental data for research on the transmutation of nuclear wastes. The effective thermal cross section of the reaction {sup 134}Cs(n,{gamma}){sup 135}Cs was found to be 140.6{+-}8.5 barns. (author)

  18. Dancoff factors with partial neutrons absorption in cluster geometry by the direct method; Calculo dos fatores de Dancoff com absorcao parcial de neutrons em geometria cluster pelo metodo direto

    Energy Technology Data Exchange (ETDEWEB)

    Rodrigues, Leticia Jenisch

    2007-07-01

    Accurate analysis of resonance absorption in heterogeneous systems is essential in problems like criticality, breeding ratios and fuel depletion calculations. In compact arrays of fuel rods, resonance absorption is strongly affected by the Dancoff factor, defined in mis study as the probability that a neutron emitted from the surface of a fuel element, enters another fuel element without any collusion in the moderator or cladding. In fact, in the most practical cases of irregular cells, it is observed that inaccuracies in computing both Grey and Black Dancoff factors, i.e. for partially and perfectly absorbing fuel rods, can lead to considerable errors in the calculated values of such integral quantities. For this reason, much effort has been made in the past decades to further improve the models for calculating Dancoff factors, a task that has been accomplished in connection with the development of faster computers. In the WIMS code, Black Dancoff factors based on the above mentioned collusion probability definition are computed in cluster geometry, for each one of the symmetrically distinct fuel pin positions in the cell. Sets of equally-spaced parallel lines are drawn in subroutine PIJ, at a number of discrete equally-incremented azimuthal angles, covering the whole system and forming a mesh over which the in-plane integrations of the Bickley functions are carried out by simple trapezoidal rule, leading to the first-flight collusion matrices. Although fast, the method in PIJ is inefficient, since the constructed mesh does not depended on the system details, so that regions of small relative volumes are crossed out by relatively few lines, which affects the convergence of the calculated probabilities. A new routine (PIJM) was then created to incorporate a more efficient integration scheme considering each system region individually, minimizing convergence problems and reducing the number of neutron track lines required in the in-plane integrations for any given

  19. Measurement of internal conversion electrons from Gd neutron capture

    Energy Technology Data Exchange (ETDEWEB)

    Kandlakunta, P. [Nuclear Engineering Program, Department of Mechanical and Aerospace Engineering, The Ohio State University, Columbus, OH 43210 (United States); Cao, L.R., E-mail: cao.152@osu.edu [Nuclear Engineering Program, Department of Mechanical and Aerospace Engineering, The Ohio State University, Columbus, OH 43210 (United States); Mulligan, P. [Nuclear Engineering Program, Department of Mechanical and Aerospace Engineering, The Ohio State University, Columbus, OH 43210 (United States)

    2013-03-21

    Gadolinium (Gd) is a suitable material for neutron conversion because of its superior neutron absorption cross-section. However, the principal secondary particles that generate electron-hole pairs in a semiconductor detector after Gd neutron capture are low-energy internal conversion (IC) electrons. We measured the IC electron spectrum due to Gd neutron capture by using a thermal neutron beam and a digitizer-based multidetector spectroscopy. We also discussed the effective use of the IC electrons in the context of a twin-detector design and the associated gamma-ray rejection issues. Extensive simulations of the spectra of IC electrons and gamma rays agreed well with the experimental results; both types of results support the feasibility of the proposed n–γ separation method.

  20. Preparation of palladium impregnated alumina adsorbents: Thermal and neutron activation analysis

    Energy Technology Data Exchange (ETDEWEB)

    Mukherjee, Sumanta; Gupta, N.K.; Roy, S.P.; Dash, S.; Kumar, A.; Bamankar, Y.R.; Rao, T.V. Vittal [Product Development Division, Bhabha Atomic Research Centre, Mumbai 400085 (India); Kumar, N. [Fuel Chemistry Division, Bhabha Atomic Research Centre, Mumbai 400085 (India); Naik, Y., E-mail: ynaik@barc.gov.in [Product Development Division, Bhabha Atomic Research Centre, Mumbai 400085 (India)

    2016-02-10

    Highlights: • Pd/Al{sub 2}O{sub 3} composite microspheres particles with high surface area were prepared sol–gel process. • Scanning electron microscopy (SEM) studies on silver coated particle. • Content of the palladium was determined using Neutron Activation Analysis (NAA). • Decomposition study has been done by quadrupole mass analyser. - Abstract: Pd/Al{sub 2}O{sub 3} composite microspheres particles with high surface area were prepared sol–gel process. The decomposition of dried gel-particles was studied by TGA/DTA and FT-IR technique. TGA studies indicated that formation of palladium is marked by a broad exothermic peak with a loss of water and oxidation of trapped HMTA/Urea nitrate mixture. The main decomposition reaction took place in the temperature range of 660–1250 K in helium and relatively lower temperature of 400 K to 1250 K in oxygen. Optical microscopy indicated that the distribution of palladium is uniform. SEM studies on silver coated particle indicated that there was surface erosion of some gel spheres while in few of them micro cracks were seen at high resolution. Content of the palladium was determined using Neutron Activation Analysis (NAA). Decomposition at various temperatures was studied using Residual gas analyser and decomposition species were identified using quadrupole mass analyser.

  1. PENENTUAN KADAR RADIONUKLIDA PADA LIMBAH CAIR PABRIK GALVANIS DENGAN METODE ANALISIS AKTIVASI NEUTRON THERMAL REAKTOR KARTINI

    Directory of Open Access Journals (Sweden)

    P. Dwijananti

    2016-09-01

    Full Text Available Kadar unsur-unsur pada limbah cair pabrik galvanis perlu diketahui, hal ini penting dilakukan sebelum limbah cair pabrik galvanisdibuang ke lingkungan. MetodeAnalisis Aktivasi Neutron (AAN digunakan untuk analisis kualitatif dan kuantitatif. Metode kualitatifdapat mengetahui unsur yang terkandung, sedangkan analisis kuantitatif untuk mengetahui kadar unsurnya. Sampel limbah cairdiaktivasi menggunakan sumber neutron dari Reaktor Kartini, kemudian dicacah menggunakan spektrometri- , setelah itudianalisis secara kualitatif dan kuantitatif. Hasil analisis kualitatif teridentifikasi 7 unsur pada limbah cair pabrik galvanis. Unsurtersebut adalah Mangan (Mn, Zirkon (Zr, Chlorine (Cl, Seng(Zn, Bromine (Br, Natrium (Na, dan Besi (Fe. Analisis kuantitatifmenunjukkan kadar unsur tersebut yaitu : Mn (1,89 - 1,92.10-9gram/l, Zr (5,65 - 5,66.10-4gram/l, Cl (4,39 - 4,50.10-8 gram/l, Zn(6,47 - 6,65.10-5 gram/l, Br (1,32 -1,35.10-3gram/l, Na (4,18 - 4,19.10-4 gram/l, dan Fe (5,65.10-5 gram/l. Berdasarkanperhitungan dan setelah dibandingkan dengan baku mutu limbah dan baku mutu air, maka limbah cair pabrik galvanis dalam batasaman. The content of elements in liquid waste of galvanise factory are recommeded to be determined first before the waste is expelled intoenvironment. The Neutron Activation Analysis was used to have qualitative and quantitative analysis. The qualitative method wasused to identify the element contained,while the quantitative one was used to measure the decay rate of the element.Tified, thosewere Mangan (Mn, Zirkon (Zr, Chlorine (Cl, Zink (Zn, Bromine (Br, Sodium (Na and Ferrum (Fe. The quantitative analysisshows the content of each elements as follows. Mn (1.89 – 1.92 x 10-9 g/l; Zr (5.65 – 5.66 x 10-4 g/l; Cl (4.39 – 4.50 x 10-8 g/l; Zn(6.47 – 6.65 x 10-5 g/l, Br (1.32 – 1.35 x 10-3 g/l; Na (4.18 – 4.19 x 10-4 g/l, and Fe (5.65 x 10-5 g/l. Based on the calculation andafter comparing it to the

  2. Effect of thermal radiation and suction on convective heat transfer of nanofluid along a wedge in the presence of heat generation/absorption

    Energy Technology Data Exchange (ETDEWEB)

    Kasmani, Ruhaila Md; Bhuvaneswari, M. [Centre for Foundation Studies in Science, University of Malaya, 50603 Kuala Lumpur (Malaysia); Sivasankaran, S.; Siri, Zailan [Institute of Mathematical Science, University of Malaya, 50603 Kuala Lumpur (Malaysia)

    2015-10-22

    An analysis is presented to find the effects of thermal radiation and heat generation/absorption on convection heat transfer of nanofluid past a wedge in the presence of wall suction. The governing partial differential equations are transformed into a system of ordinary differential equations using similarity transformation. The resulting system is solved numerically using a fourth-order Runge–Kutta method with shooting technique. Numerical computations are carried out for different values of dimensionless parameters to predict the effects of wedge angle, thermophoresis, Brownian motion, heat generation/absorption, thermal radiation and suction. It is found that the temperature increases significantly when the value of the heat generation/absorption parameter increases. But the opposite observation is found for the effect of thermal radiation.

  3. The improvement of the energy resolution in epi-thermal neutron region of Bonner sphere using boric acid water solution moderator.

    Science.gov (United States)

    Ueda, H; Tanaka, H; Sakurai, Y

    2015-10-01

    Bonner sphere is useful to evaluate the neutron spectrum in detail. We are improving the energy resolution in epi-thermal neutron region of Bonner sphere, using boric acid water solution as a moderator. Its response function peak is narrower than that for polyethylene moderator and the improvement of the resolution is expected. The resolutions between polyethylene moderator and boric acid water solution moderator were compared by simulation calculation. Also the influence in the uncertainty of Bonner sphere configuration to spectrum estimation was simulated. Copyright © 2015 Elsevier Ltd. All rights reserved.

  4. Seismology of adolescent neutron stars: Accounting for thermal effects and crust elasticity

    CERN Document Server

    Krüger, C J; Andersson, N

    2014-01-01

    We study the oscillations of relativistic stars, incorporating key physics associated with internal composition, thermal gradients and crust elasticity. Our aim is to develop a formalism which is able to account for the state-of-the-art understanding of the complex physics associated with these systems. As a first step, we build models using a modern equation of state including composition gradients and density discontinuities associated with internal phase-transitions (like the crust-core transition and the point where muons first appear in the core). In order to understand the nature of the oscillation spectrum, we carry out cooling simulations to provide realistic snapshots of the temperature distribution in the interior as the star evolves through adolescence. The associated thermal pressure is incorporated in the perturbation analysis, and we discuss the presence of $g$-modes arising as a result of thermal effects. We also consider interface modes due to phase-transitions and the gradual formation of the...

  5. Degradation in Mechanical and Thermal Properties of Partially Aligned CNT/Epoxy Composites due to Seawater Absorption

    Science.gov (United States)

    Saha, Sunirmal; Bal, Smrutisikha

    2017-02-01

    This literature gives an overview of the effect of water uptake on the mechanical and thermal performances of partially aligned carbon nanotube (CNT)/ epoxy (having CNTs wt.%: 0.5, 0.75 and 1) along with pure epoxy composites. Weight change behaviour of all the composites immersed in seawater for a period of six months has been recorded. The state of CNT/matrix interface is believed to be influenced due to water absorption. Reduction in flexural modulus, strength, hardness and glass transition temperature (Tg ) of the specimens have been evaluated as compared to their unexposed counterparts due to adverse effect of water absorption. Results demonstrated 35-46% reduction in flexural modulus, 43-56% decrement in flexural strength, 4-7 MPa reduction in hardness and minor deterioration in Tg values for all the composites. However, the specimen having 0.75 wt.% CNT loading, exhibited minimum reduction in properties in all aspects compared to others. Scanning electron microscopy (SEM) has been employed to study the failure mechanism of the specimens after performing the mechanical tests.

  6. Atlas of neutron resonances

    CERN Document Server

    Mughabghab, Said

    2018-01-01

    Atlas of Neutron Resonances: Resonance Properties and Thermal Cross Sections Z= 1-60, Sixth Edition, contains an extensive list of detailed individual neutron resonance parameters for Z=1-60, as well as thermal cross sections, capture resonance integrals, average resonance parameters and a short survey of the physics of thermal and resonance neutrons. The long introduction contains: nuclear physics formulas aimed at neutron physicists; topics of special interest such as valence neutron capture, nuclear level density parameters, and s-, p-, and d-wave neutron strength functions; and various comparisons of measured quantities with the predictions of nuclear models, such as the optical model. As in the last edition, additional features have been added to appeal to a wider spectrum of users. These include: spin-dependent scattering lengths that are of interest to solid-state physicists, nuclear physicists and neutron evaluators; calculated and measured Maxwellian average 5-keV and 30-keV capture cross sections o...

  7. Determination of essential and toxic elements in commercial baby foods by instrumental neutron activation analysis and atomic absorption spectrometry; Determinacao dos elementos essenciais e toxicos em alimentos comerciais infantis por analise por ativacao com neutrons e espectrometria de absorcao atomica

    Energy Technology Data Exchange (ETDEWEB)

    Vallinoto, Priscila

    2013-08-01

    The World Health Organization recommends that infants should be breast fed exclusively for at least six months after birth. After this period, it is recommended to start introducing complementary foods, in order to meet the child's nutritional, mineral and energy needs. Commercial food products for infants form an important part of the diet for many babies. Thus, it is very important that such food contains sufficient amounts of minerals. Inadequate complementary feeding is a major cause of high rates of infant malnutrition in developing countries. In this study, essential elements: Ca, Cl, Co, Cr, Fe, K, Mg, Mn, Na, Se and Zn and toxic elements: As, Cd, Hg levels were determined in twenty seven different commercial infant food product samples by Instrumental Neutron Activation Analysis (INAA) and Atomic Absorption Spectrometry (AAS). In order to validate both methodologies the reference material: INCT MPH-2 Mixed Polish Herbs and NIST - SRM 1577b Bovine Liver by INAA and NIST - SRM 1548th Typical Diet and NIST - SRM 1547 Peach Leaves by AAS were analyzed. The twenty seven baby food samples were acquired from Sao Paulo city supermarkets and stores. Essential and toxic elements were determined. Most of the essential element concentrations obtained were lower than the World Health Organization requirements, while concentrations of toxic elements were below the tolerable upper limit. These low essential element concentrations in these samples indicate that infants should not be fed only with commercial complementary foods. (author)

  8. Modeling electrical power absorption and thermally-induced biological tissue damage.

    Science.gov (United States)

    Zohdi, T I

    2014-01-01

    This work develops a model for thermally induced damage from high current flow through biological tissue. Using the first law of thermodynamics, the balance of energy produced by the current and the energy absorbed by the tissue are investigated. The tissue damage is correlated with an evolution law that is activated upon exceeding a temperature threshold. As an example, the Fung material model is used. For certain parameter choices, the Fung material law has the ability to absorb relatively significant amounts of energy, due to its inherent exponential response character, thus, to some extent, mitigating possible tissue damage. Numerical examples are provided to illustrate the model's behavior.

  9. Thermal-hydraulic performance of a water-cooled tungsten-rod target for a spallation neutron source

    Energy Technology Data Exchange (ETDEWEB)

    Poston, D.I.

    1997-08-01

    A thermal-hydraulic (T-H) analysis is conducted to determine the feasibility and limitations of a water-cooled tungsten-rod target at powers of 1 MW and above. The target evaluated has a 10-cm x 10-cm cross section perpendicular to the beam axis, which is typical of an experimental spallation neutron source - both for a short-pulse spallation source and long-pulse spallation source. This report describes the T-H model and assumptions that are used to evaluate the target. A 1-MW baseline target is examined, and the results indicate that this target should easily handle the T-H requirements. The possibility of operating at powers >1 MW is also examined. The T-H design is limited by the condition that the coolant does not boil (actual limits are on surface subcooling and wall heat flux); material temperature limits are not approached. Three possible methods of enhancing the target power capability are presented: reducing peak power density, altering pin dimensions, and improving coolant conditions (pressure and temperature). Based on simple calculations, it appears that this target concept should have little trouble reaching the 2-MW range (from a purely T-H standpoint), and possibly much higher powers. However, one must keep in mind that these conclusions are based solely on thermal-hydraulics. It is possible, and perhaps likely, that target performance could be limited by structural issues at higher powers, particularly for a short-pulse spallation source because of thermal shock issues.

  10. Measurement of the neutron capture cross section of the fissile isotope 235U with the CERN n_TOF total absorption calorimeter and a fission tagging based on micromegas detectors

    Directory of Open Access Journals (Sweden)

    Balibrea-Correa J.

    2017-01-01

    Full Text Available The accuracy on neutron capture cross section of fissile isotopes must be improved for the design of future nuclear systems such as Gen-IV reactors and Accelerator Driven Systems. The High Priority Request List of the Nuclear Energy Agency, which lists the most important nuclear data requirements, includes also the neutron capture cross sections of fissile isotopes such as 233,235U and 239,241Pu. A specific experimental setup has been used at the CERN n_TOF facility for the measurement of the neutron capture cross section of 235U by a set of micromegas fission detectors placed inside a segmented BaF2 Total Absorption Calorimeter.

  11. Measuring Neutron Star Mass and Radius with Three Mass-Radius Relations

    OpenAIRE

    Zhang, C. M.; Yin, H. X.; Kojima, Y.; Chang, H. K.; Xu, R. X.; Li, X. D.; Zhang, B.; Kiziltan, B.

    2006-01-01

    We propose to determine the mass and the radius of a neutron star (NS) using three measurable mass-radius relationships, namely the ``apparent'' radius inferred from neutron star thermal emission, the gravitational redshift inferred from the absorption lines, as well as the averaged stellar mass density inferred from the orbital Keplerian frequency derived from the kilohertz quasi periodic oscillation (kHz QPO) data. We apply the method to constrain the NS mass and the radius of the X-ray sou...

  12. Effect of Tube Arrangement on the Thermal Performance of a High Temperature Generator of the Absorption System

    Science.gov (United States)

    Lee, Insong; Cho, Keumnam

    The present study numerically investigated the effect of tube arrangement on the thermal performance of the high temperature generator (HTG) of a double effect LiBr-water absorption system with the cooling capacity of 210 refrigeration tons. The HTG tubes were located behind the pre-mixed surface flame burner. The HTG was consisted with a set of circular tubes and flattened tubes in series. LiBr aqueous weak solution was flowed into the HTG tube, and then turned to strong solution at the exit of the HTG tube. FLUENT, as a commercial code, was used to estimate the thermal performance of the HTG. Standard k-ɛ model was applied for the turbulent flow of combustion gas around the HTG tubes. Key parameters were the diameter of the circular tube and tube pitch ratio of flattened and circular tubes in the HTG. The combustion gas temperature was increased and its heat transfer rate was decreased as the circular tube diameter was increased, and the pitch ratios of both circular and flattened were decreased.

  13. Uncertainty and sensitivity analysis for the modeling of transients with interaction of thermal hydraulics and neutron kinetics

    Energy Technology Data Exchange (ETDEWEB)

    Soeren Kliem; Siegfried Mittag [Forschungszentrum Rossendorf (FZR), Institute of Safety Research, P.O.B. 510119, D-01314 Dresden (Germany); Siegfried Langenbuch [Gesellschaft fuer Anlagen- und Reaktorsicherheit mbH, P.O.B. 13 28, D-85748 Garching (Germany)

    2005-07-01

    Full text of publication follows: The transition from the application of conservative models to the use of best-estimate models raises the question about the uncertainty of the obtained results. This question becomes especially important, if the best-estimate models should be used for safety analyses in the field of nuclear engineering. Different methodologies were developed to assess the uncertainty of the calculation results of computer simulation codes. One of them is the methodology developed by Gesellschaft fuer Anlagenund Reaktorsicherheit (GRS) which uses the statistical code package SUSA. In the past, this methodology was applied to the calculation results of the advanced thermal hydraulic system code ATHLET. In the frame of the recently finished EU FP5 funded research project VALCO, that methodology was extended and successfully applied to different coupled code systems, including the uncertainty analysis for neutronics. These code systems consist of a thermal hydraulic system code and a 3D neutron kinetic core model. One of the code systems applied was ATHLET coupled with the Rossendorf kinetics code DYN3D. Two real transients at NPPs with VVER-type reactors documented within the VALCO project were selected for analyses. One was the load drop of one of two turbines to house load level at the Loviisa-1 NPP (VVER-440), the second was a test with the switching-off of one of two main feed water pumps at the VVER-1000 Balakovo-4 NPP. The current paper is dedicated to the different steps of the use and implementation of the GRS methodology to coupled code systems and to the assessment of the results obtained by the DYN3D/ATHLET code. Based on the relevant physical processes in both transients, lists of possible sources of uncertainties were compiled. They are specific for the two transients. Besides control parameters like control rod movement and thermal hydraulic parameters like secondary side pressure, mass flow rates, pressurizer sprayer and heater

  14. Impact of neutron thermal scattering laws on the burn-up analysis of supercritical LWR's fuel assemblies

    Energy Technology Data Exchange (ETDEWEB)

    Conti, Andrea

    2011-10-15

    This work is a contribution to the HPLWR2 (High Performance Light Water Reactor Phase 2), a research project having the goal to investigate the technical feasibility of the High Performance Light Water Reactor. The basic idea of the HPLWR is that of an LWR working at supercritical pressure, which would allow heating up the coolant to a temperature of about 500 C without having phase transition and sending the coolant directly to the turbine. One issue aroused by this design, deserving to be addressed by research, is the behaviour of thermal neutrons in supercritical water. At thermal energies, the De Broglie wavelength associated with the neutron is comparable to the interatomic distances in crystals and molecules and the scattering is fully governed by the laws of quantum mechanics, according to which the geometry of the aggregates the nuclei are bound to and their intra- and intermolecular dynamics are of crucial importance. It can be shown that there is a certain mathematical relation between the Fourier-transform of the hydrogen atoms' velocity autocorrelation function and their double-differential scattering cross section. This Fourier-transform, called ''generalized frequency distribution'', can be derived from experimental measurements and, effectively, Bernnat et al. of the Institut fuer Kernenergetik und Energiesysteme of the University of Stuttgart derived the generalized frequency distribution for liquid water on the basis of experimental results of Page and Haywood. Unfortunately there exists no experimental facility nowadays to support a thorough work of this type on supercritical water and therefore the scattering kernel for thermal neutrons in supercritical water is unknown. In criticality calculations involving supercritical water one can turn to one of the thermal scattering kernels available nowadays for hydrogen bound to the H{sub 2}O molecule: for liquid water, for vapour or considering the nuclei of hydrogen as unbound

  15. Structure and thermal motion of phosphorylethanolamine at 122 K from neutron diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Weber, H.P.; McMullan, R.K.; Swaminathan, S.; Craven, B.M.

    1984-01-01

    At 122K, the crystalline structure of phosphorylethanolamine is monoclinic and the crystal parameters are reported. Nuclear anisotropic thermal parameters have been analyzed to describe the molecular thermal motion including the non-rigid vibrations. The C-H distances with both harmonic librational and anharmonic stretching-motion corrections range from 1.095(4) to 1.099(4)A. These estimated bond lengths are in satisfactory agreement with values determined for C-H theoretically and by other experimental methods. The configuration of the P-O bonds in the monoester H-O-P-O-C group is (+)-ac, (-)-sc. The terminal O-H and NH3 groups are twisted 40 to 20, respectively, from ideally expected for adjacent OCH3 groups alternating up and down.

  16. GCFR Coupled Neutronic and Thermal-Fluid-Dynamics Analyses for a Core Containing Minor Actinides

    Directory of Open Access Journals (Sweden)

    Diego Castelliti

    2009-01-01

    Full Text Available Problems about future energy availability, climate changes, and air quality seem to play an important role in energy production. While current reactor generations provide a guaranteed and economical energy production, new nuclear power plant generation would increase the ways and purposes in which nuclear energy can be used. To explore these new technological applications, several governments, industries, and research communities decided to contribute to the next reactor generation, called “Generation IV.” Among the six Gen-IV reactor designs, the Gas Cooled Fast Reactor (GCFR uses a direct-cycle helium turbine for electricity generation and for a CO2-free thermochemical production of hydrogen. Additionally, the use of a fast spectrum allows actinides transmutation, minimizing the production of long-lived radioactive waste in an integrated fuel cycle. This paper presents an analysis of GCFR fuel cycle optimization and of a thermal-hydraulic of a GCFR-prototype under steady-state and transient conditions. The fuel cycle optimization was performed to assess the capability of the GCFR to transmute MAs, while the thermal-hydraulic analysis was performed to investigate the reactor and the safety systems behavior during a LOFA. Preliminary results show that limited quantities of MA are not affecting significantly the thermal-fluid-dynamics behavior of a GCFR core.

  17. Seismology of adolescent neutron stars: Accounting for thermal effects and crust elasticity

    Science.gov (United States)

    Krüger, C. J.; Ho, W. C. G.; Andersson, N.

    2015-09-01

    We study the oscillations of relativistic stars, incorporating key physics associated with internal composition, thermal gradients and crust elasticity. Our aim is to develop a formalism which is able to account for the state-of-the-art understanding of the complex physics associated with these systems. As a first step, we build models using a modern equation of state including composition gradients and density discontinuities associated with internal phase transitions (like the crust-core transition and the point where muons first appear in the core). In order to understand the nature of the oscillation spectrum, we carry out cooling simulations to provide realistic snapshots of the temperature distribution in the interior as the star evolves through adolescence. The associated thermal pressure is incorporated in the perturbation analysis, and we discuss the presence of g -modes arising as a result of thermal effects. We also consider interface modes due to phase-transitions and the gradual formation of the star's crust and the emergence of a set of shear modes.

  18. Innovative and Advanced Coupled Neutron Transport and Thermal Hydraulic Method (Tool) for the Design, Analysis and Optimization of VHTR/NGNP Prismatic Reactors

    Energy Technology Data Exchange (ETDEWEB)

    Rahnema, Farzad; Garimeela, Srinivas; Ougouag, Abderrafi; Zhang, Dingkang

    2013-11-29

    This project will develop a 3D, advanced coarse mesh transport method (COMET-Hex) for steady- state and transient analyses in advanced very high-temperature reactors (VHTRs). The project will lead to a coupled neutronics and thermal hydraulic (T/H) core simulation tool with fuel depletion capability. The computational tool will be developed in hexagonal geometry, based solely on transport theory without (spatial) homogenization in complicated 3D geometries. In addition to the hexagonal geometry extension, collaborators will concurrently develop three additional capabilities to increase the code’s versatility as an advanced and robust core simulator for VHTRs. First, the project team will develop and implement a depletion method within the core simulator. Second, the team will develop an elementary (proof-of-concept) 1D time-dependent transport method for efficient transient analyses. The third capability will be a thermal hydraulic method coupled to the neutronics transport module for VHTRs. Current advancements in reactor core design are pushing VHTRs toward greater core and fuel heterogeneity to pursue higher burn-ups, efficiently transmute used fuel, maximize energy production, and improve plant economics and safety. As a result, an accurate and efficient neutron transport, with capabilities to treat heterogeneous burnable poison effects, is highly desirable for predicting VHTR neutronics performance. This research project’s primary objective is to advance the state of the art for reactor analysis.

  19. Solid-state effects on thermal-neutron cross sections and on low-energy resonances

    Energy Technology Data Exchange (ETDEWEB)

    Harvey, J.A.; Mook, H.A.; Hill, N.W.; Shahal, O.

    1982-01-01

    The neutron total cross sections of several single crystals (Si, Cu, sapphire), several polycrystalline samples (Cu, Fe, Be, C, Bi, Ta), and a fine-powder copper sample have been measured from 0.002 to 5 eV. The Cu powder and polycrystalline Fe, Be and C data exhibit the expected abrupt changes in cross section. The cross section of the single crystal of Si is smooth with only small broad fluctuations. The data on two single Cu crystals, the sapphire crystal, cast Bi, and rolled samples of Ta and Cu have many narrow peaks approx. 10/sup -3/ eV wide. High resolution (0.3%) transmission measurements were made on the 1.057-eV resonance in /sup 240/Pu and the 0.433-eV resonance in /sup 180/Ta, both at room and low temperatures to study the effects of crystal binding. Although the changes in Doppler broadening with temperature were apparent, no asymmetries due to a recoilless contribution were observed.

  20. Tritium removal from various lithium aluminates irradiated by fast and thermal neutrons (COMPLIMENT experiment)

    Energy Technology Data Exchange (ETDEWEB)

    Alvani, C. (ENEA CRE Casaccia, INN/NUMA, Rome (Italy)); Carconi, P.L. (ENEA CRE Casaccia, INN/NUMA, Rome (Italy)); Casadio, S. (ENEA CRE Casaccia, INN/NUMA, Rome (Italy)); Moauro, A. (ENEA CRE Casaccia, INN/NUMA, Rome (Italy))

    1994-02-01

    Within the frame of the COMPLIMENT experiment, [gamma]-LiAlO[sub 2] specimens with different microstructures (grain size distributions) were tested in the same environmental conditions to compare the effects caused by [sup 6]Li(n, [alpha])T reaction and by fast neutron scattering, the damaging dose being held at about the same level (1.6-1.8 dpa). The tritium retention times were obtained by the tritium removal of isothermal annealing under He + 0.1% H[sub 2] sweeping gas. In spite of the different Li burnups (2.5% and 0.25%) and the residual tritium concentrations which were found in the irradiated specimens (4.3 Ci/g and 0.09 Ci/g, respectively, for specimens held at 450 C during the irradiations), the kinetics of tritium removal was not found to be discriminated by the two different irradiations. Moreover, the results were found to agree with those previously obtained by the ''in-situ'' TEQUILA experiment, performed on the same type of Li ceramics. Hence, the apparent first order desorption mechanism has been confirmed to control the kinetics of tritium removal from the porous fine grain [gamma]-LiAlO[sub 2] ceramics. (orig.)

  1. Measuring Thermal Conductivity and Moisture Absorption of Cryo-Insulation Materials

    Science.gov (United States)

    Lambert, Michael A.

    1998-01-01

    NASA is seeking to develop thermal insulation material systems suitable for withstanding both extremely high temperatures encountered during atmospheric re-entry heating and aero- braking maneuvers, as well as extremely low temperatures existing in liquid fuel storage tanks. Currently, materials used for the high temperature insulation or Thermal Protection System (TPS) are different from the low temperature, or cryogenic insulation. Dual purpose materials are necessary to the development of reusable launch vehicles (RLV). The present Space Shuttle (or Space Transportation System, STS) employs TPS materials on the orbiter and cryo-insulation materials on the large fuel tank slung under the orbiter. The expensive fuel tank is jettisoned just before orbit is achieved and it burns up while re-entering over the Indian Ocean. A truly completely reusable launch vehicle must store aR cryogenic fuel internally. The fuel tanks will be located close to the outer surface. In fact the outer skin of the craft will probably also serve as the fuel tank enclosure, as in jet airliners. During a normal launch the combined TPS/cryo-insulation system will serve only as a low temperature insulator, since aerodynamic heating is relatively minimal during ascent to orbit. During re-entry, the combined TPS/cryo-insulation system will serve only as a high temperature insulator, since all the cryogenic fuel will have been expended in orbit. However, in the event of an.aborted launch or a forced/emergency early re-entry, the tanks will still contain fuel, and the TPS/cryo-insulation will have to serve as both low and high temperature insulation. Also, on long duration missions, such as to Mars, very effective cryo-insulation materials are needed to reduce bod off of liquid propellants, thereby reducing necessary tankage volume, weight, and cost. The conventional approach to obtaining both low and high temperature insulation, such as is employed for the X-33 and X-34 spacecraft, is to use

  2. New Triplet Sensitization Routes for Photon Upconversion: Thermally Activated Delayed Fluorescence Molecules, Inorganic Nanocrystals, and Singlet-to-Triplet Absorption.

    Science.gov (United States)

    Yanai, Nobuhiro; Kimizuka, Nobuo

    2017-10-17

    Photon upconversion based on triplet-triplet annihilation (TTA-UC) has attracted much interest because of its possible applications to renewable energy production and biological fields. In particular, the UC of near-infrared (NIR) light to visible (vis) light is imperative to overcome the Shockley-Queisser limit of single-junction photovoltaic cells, and the efficiency of photocatalytic hydrogen production from water can also be improved with the aid of vis-to-ultraviolet (UV) UC. However, both processes have met limitations in the wavelength range, efficiency, and sensitivity for weak incident light. This Account describes recent breakthroughs that solve these major problems, new triplet sensitization routes to significantly enlarge the range of conversion wavelength by minimizing the energy loss during intersystem crossing (ISC) of triplet sensitizers or bypassing the ISC process. The photochemical processes of TTA-UC in general start with the absorption of longer wavelength incident light by triplet sensitizers, which generate the triplet states via ISC. This ISC inevitably accompanies the energy loss of hundreds of millielectronvolts, which significantly limits the TTA-UC with large anti-Stokes shifts. The small S1-T1 gap of molecules showing thermally activated delayed fluorescence (TADF) allows the sensitization of emitters with the highest T1 and S1 energy levels ever employed in TTA-UC, which results in efficient vis-to-UV UC. As alternatives to molecular sensitizers in the NIR region, inorganic nanocrystals with broad NIR absorption bands have recently been shown to work as effective sensitizers for NIR-to-vis TTA-UC. Their small exchange splitting minimizes the energy loss during triplet sensitization. The modification of nanocrystal surfaces with organic acceptors via coordination bonds allows efficient energy transfer between the components and succeeding TTA processes. To remove restrictions on the energy loss during ISC, molecules with direct singlet

  3. Effect of AgCl NPs: Physical, thermal, absorption and luminescence properties

    Science.gov (United States)

    Nurhafizah, H.; Rohani, M. S.

    2017-06-01

    Silver nanoparticles (AgCl NPs) are embedded in Er3+/Nd3+ co-doped lithium niobate tellurite glasses of the form (68-x)TeO2-15Li2CO3-15Nb2O5-1Er2O3-1Nd2O3-(x)AgCl with x = 1,2 and 3 mol% via conventional melt-quenching technique. The physical properties such as density, ionic packing density, refractive index and electronic polarizability are computed utilizing the usual method. The existence of AgCl NPs with an average size of 3.7 nm is confirmed using TEM analysis. Moreover, the thermal stability and Hruby criterion of the glass decreases as the AgCl NPs content increases. The direct optical band gap are found decrease as the AgCl NPs content increase, but both indirect optical band gap and Urbach energy are found increases as AgCl NPs content increases. The luminescence spectra shows two strong emission which is the purple emission at 436 nm and red emission at 724 nm which also been observed has strong quenching due to the AgCl NPs, Er3+/Nd3+ dopant and modifier, lithium niobate which possessed magnetic penetration. These glass compositions may be potential for various applications such as solid state devices including laser.

  4. An expression for the atomic fluorescence and thermal-emission intensity under conditions of near saturation and arbitrary self-absorption

    NARCIS (Netherlands)

    Omenetto, N.; Winefordner, J.D.; Alkemade, C.T.J.

    An expression for the effect of self-absorption on the fluorescence and thermal emission intensities is derived by taking into account stimulated emission. A simple, idealized case is considered, consisting of a two level atomic system, in a flame, homogeneous with respect to temperature and

  5. Design of the experimental apparatus to obtain a thermal neutron beam, intermediate-energy neutrons (2-144 keV) and high-energy photons (6 MeV) by means of the TRIGA reactor at the ENEA Casaccia center

    CERN Document Server

    Laitano, R F

    1987-01-01

    Design of the experimental apparatus to obtain a thermal neutron beam, intermediate-energy neutrons (2-144 keV) and high-energy photons (6 MeV) by means of the TRIGA reactor at the ENEA Casaccia center

  6. Development and application of the coupled thermal-hydraulics and neutron-kinetics code ATHLET/BIPR-VVER for safety analysis

    Energy Technology Data Exchange (ETDEWEB)

    Lizorkin, M.; Nikonov, S. [Kurchatov Institute for Atomic Energy, Moscow (Russian Federation); Langenbuch, S.; Velkov, K. [Gesellschaft fur Anlagen- und Reaktorsicherheit (GRS) mbH, Garching (Germany)

    2006-07-01

    The coupled thermal-hydraulics and neutron-kinetics code ATHLET/BIPR-VVER was developed within a co-operation between the RRC Kurchatov Institute (KI) and GRS. The modeling capability of this coupled code as well as the status of validation by benchmark activities and comparison with plant measurements are described. The paper is focused on the modeling of flow mixing in the reactor pressure vessel including its validation and the application for the safety justification of VVER plants. (authors)

  7. Determination of the thermal neutron induced 36Cl(n,p)36S and 36Cl(n,α)33P reaction cross sections

    Science.gov (United States)

    Wagemans, C.; Bieber, R.; Geltenbort, P.

    1996-07-01

    The cross sections of the 36Cl(nth,p) 36S and the 36Cl(nth,α)33P reactions were measured with thermal neutrons at the high flux reactor of the ILL in Grenoble. For the 36Cl(nth,p)36S reaction cross section a precise value of (47+/-2) mb was obtained and for the 36Cl(nth,α)33P reaction a cross section value of (0.59+/-0.07) mb was determined.

  8. Simultaneous measurement of thermal diffusivity and effective infrared absorption coefficient in IR semitransparent and semiconducting n-CdMgSe crystals using photothermal radiometry

    Energy Technology Data Exchange (ETDEWEB)

    Pawlak, M., E-mail: mpawlak@fizyka.umk.pl [Institute of Physics, Faculty of Physics, Astronomy and Informatics, Nicolaus Copernicus University, Grudziądzka 5/7, Toruń (Poland); Maliński, M. [Department of Electronics and Computer Science, Koszalin University of Technology, 2 Śniadeckich St., Koszalin 75-453 (Poland)

    2015-01-10

    Highlights: • The new method of determination of the effective infrared absorption coefficient is presented. • The method can be used for transparent samples for the excitation radiation. • The effect of aluminum foil on the PTR signal in a transmission configuration is discussed. - Abstract: In this paper we propose a new procedure of simultaneous estimation of the effective infrared optical absorption coefficient and the thermal diffusivity of solid state samples using the photothermal infrared radiometry method in the transmission configuration. The proposed procedure relies on the analysis of the frequency dependent signal obtained from the samples covered with thin aluminum foil. This method can be applied for both optically opaque and transparent samples. The proposed method is illustrated with the results of the thermal diffusivity and the effective IR absorption coefficient obtained for several Cd{sub 1−x}Mg{sub x}Se crystals.

  9. 3D thermal modeling of TRISO fuel coupled with neutronic simulation

    Energy Technology Data Exchange (ETDEWEB)

    Hu, Jianwei [Los Alamos National Laboratory; Uddin, Rizwan [UNIV OF ILLINIOS

    2010-01-01

    The Very High Temperature Gas Reactor (VHTR) is widely considered as one of the top candidates identified in the Next Generation Nuclear Power-plant (NGNP) Technology Roadmap under the U.S . Depanment of Energy's Generation IV program. TRlSO particle is a common element among different VHTR designs and its performance is critical to the safety and reliability of the whole reactor. A TRISO particle experiences complex thermo-mechanical changes during reactor operation in high temperature and high burnup conditions. TRISO fuel performance analysis requires evaluation of these changes on micro scale. Since most of these changes are temperature dependent, 3D thermal modeling of TRISO fuel is a crucial step of the whole analysis package. In this paper, a 3D numerical thermal model was developed to calculate temperature distribution inside TRISO and pebble under different scenarios. 3D simulation is required because pebbles or TRISOs are always subjected to asymmetric thermal conditions since they are randomly packed together. The numerical model was developed using finite difference method and it was benchmarked against ID analytical results and also results reported from literature. Monte-Carlo models were set up to calculate radial power density profile. Complex convective boundary condition was applied on the pebble outer surface. Three reactors were simulated using this model to calculate temperature distribution under different power levels. Two asymmetric boundary conditions were applied to the pebble to test the 3D capabilities. A gas bubble was hypothesized inside the TRISO kernel and 3D simulation was also carried out under this scenario. Intuition-coherent results were obtained and reported in this paper.

  10. Supercritical Water Nuclear Steam Supply System: Innovations In Materials, Neutronics & Thermal-Hydraulics

    Energy Technology Data Exchange (ETDEWEB)

    Mark Anderson; M.L. Corradini; K. Sridharan; P. WIlson; D. Cho; T.K. Kim; S. Lomperski

    2004-09-02

    In the 1990's supercritical light-water reactors were considered in conceptual designs. A nuclear reactor cooled by supercritical waster would have a much higher thermal efficiency with a once-through direct power cycle, and could be based on standardized water reactor components (light water or heavy water). The theoretical efficiency could be improved by more than 33% over that of other water reactors and could be simplified with higher reliability; e.g., a boiling water reactor without steam separators or dryers.

  11. Neutronic and thermal hydraulic analysis of the Geological Survey TRIGA Reactor

    Science.gov (United States)

    Shugart, Nicolas

    The United States Geological Survey TRIGA Reactor (GSTR) is a 1 MW reactor located in Lakewood, Colorado. In support of the GSTR's relicensing efforts, this project developed and validated a Monte Carlo N-Particle Version 5 (MCNP5) model of the GSTR reactor. The model provided estimates of the excess reactivity, power distribution and the fuel temperature, water temperature, void, and power reactivity coefficients for the current and limiting core. The MCNP5 model predicts a limiting core excess reactivity of 6.48 with a peak rod power of 22.2 kW. The fuel and void reactivity coefficients for the limiting core are strongly negative, and the core water reactivity coefficient is slightly positive, consistent with other TRIGA analyses. The average fuel temperature reactivity coefficient of the full power limiting core is -0.0135 /K while the average core void coefficient is -0.069 /K from 0-20 % void. The core water temperature reactivity coefficient is +0.012 /K. Following the neutronics analysis, the project developed RELAP5 and PARET-ANL models of the GSTR hot-rod fuel channel under steady state and transient conditions. The GSTR limiting core, determined as part of this analysis, provides a worst case operating scenario for the reactor. During steady state operations, the hot rod of the limiting core has a peak fuel temperature of 829 K and a minimum departure from nucleate boiling ratio of 2.16. After a $3.00 pulse reactivity insertion the fuel reaches a peak temperature is 1070 K. Examining the model results several seconds after a pulse reveals flow instabilities that result from weaknesses in the current two-channel model.

  12. Improvements and applications of neutron activation analysis using the monostandard method

    Energy Technology Data Exchange (ETDEWEB)

    Takeuchi, Takayuki (Kyoto Univ., Kumatori, Osaka (Japan). Research Reactor Inst.)

    1981-11-01

    Neutron activation analysis using the monostandard method is improved for broad application by compiling the necessary data, especially, selecting thermal neutron cross-sections and resonance integrals, and by investigating some sources of errors in neutron activation analysis; neutron flux self-shielding, dead time correction and losses of volatile elements. The self-shielding effects of thermal neutron flux and epithermal neutron flux are examined. The maximum permissible weight is given for each element of which the absorption thermal cross-section or the absorption resonance integral is greater than 100 b. Several correction methods for dead time of a multichannel analyser are checked experimentally and limits of application of those methods are discussed. Volatilization losses of mercury before, during and after neutron irradiation and the losses of chlorine, bromine and iodine during the irradiation are examined. The reagents which should be added to the standard to suppress the volatilization of mercury, are investigated. The monostandard method has been applied to the analyses of biological materials and archaeological samples. The NBS standard reference materials: Orchard Leaves and Bovine Liver are analysed and the results are compared with literature values. Ancient pigments of murals in the Takamatsu-zuka Tumulus are also analysed by the method. Archaeological meanings of those elemental concentrations are discussed.

  13. On the performance of heat absorption/generation and thermal stratification in mixed convective flow of an Oldroyd-B fluid

    Directory of Open Access Journals (Sweden)

    Tasawar Hayat

    2017-12-01

    Full Text Available This investigation explores the thermally stratified stretchable flow of an Oldroyd-B material bounded by a linear stretched surface. Heat transfer characteristics are addressed through thermal stratification and heat generation/absorption. Formulation is arranged for mixed convection. Application of suitable transformations provides ordinary differential systems through partial differential systems. The homotopy concept is adopted for the solution of nonlinear differential systems. The influence of several arising variables on velocity and temperature is addressed. Besides this, the rate of heat transfer is calculated and presented in tabular form. It is noticed that velocity and Nusselt number increase when the thermal buoyancy parameter is enhanced. Moreover, temperature is found to decrease for larger values of Prandtl number and heat absorption parameter. Comparative analysis for limiting study is performed and excellent agreement is found.

  14. The use of a thermal neutron beam for the narcotics and explosives detection using tomography, applied on the national public safety; Uso de um feixe de neutrons termicos para a deteccao de narcoticos e explosivos por tomografia, para aplicacao na seguranca publica nacional

    Energy Technology Data Exchange (ETDEWEB)

    Silva, Ademir Xavier da

    1999-08-01

    Aiming to even more extend the range of the applications, we demonstrate, on this work, the potentialities of neutron radiography, allied to the computerized tomography by transmission, for the detection of drugs and explosives concealed by several materials intending to the National Public Safety. We analysed: thermal neutron radiographs of cocaine samples under both different physics conditions and purity degrees, subjected to hidden conditions by lead, tobacco, iron and cotton cloth; tomographic images using thermal neutron beams obtained from both experimental and simulated dates of drug and explosive samples concealed by light and heavy materials. In the experimental testings, the samples were irradiated using thermal neutron beams coming from the J-9 irradiation channel of the Argonauta reactor of the IEN/CNEN, for 30 minutes, in a flux of 2,5 x 10{sup 5} n.cm{sup -2}.s{sup -1}. The MCNP was utilized either to generate the projection dates used on the simulate tomographs or to realize the moderation, collimation and shielding calculations of a neutron radiography system using {sup 252} Cf as a neutron source. Analysis the images of drug samples, we conclude that the neutron radiography was able to detect them, even hidden by the above cited materials. Using the obtained images, it was possible to demonstrate the potential of a tomography utilizing thermal neutron beams for the same detection. According to the neutronic calculations, we estimate a thermal neutron beam, on the image plane, up to 7x10{sup 5} n.cm{sup -2}..s{sup -1}, considering 50 mg of {sup 252} Cf with a collimation ratio of 7,5. (author)

  15. A comparison of MCNP6-1.0 and GEANT 4-10.1 when evaluating the neutron output of a complex real world nuclear environment: The thermal neutron facility at the Tri Universities Meson facility

    Energy Technology Data Exchange (ETDEWEB)

    Monk, S.D., E-mail: s.monk@lancaster.ac.uk [Department of Engineering, Lancaster University, Lancaster LA1 4YW (United Kingdom); Shippen, B.A. [Department of Engineering, Lancaster University, Lancaster LA1 4YW (United Kingdom); Colling, B.R. [Department of Engineering, Lancaster University, Lancaster LA1 4YW (United Kingdom); Culham Centre for Fusion Energy, Culham Science Centre, Abingdon OX14 3DB (United Kingdom); Cheneler, D.; Al Hamrashdi, H.; Alton, T. [Department of Engineering, Lancaster University, Lancaster LA1 4YW (United Kingdom)

    2017-05-15

    Highlights: • Comparison of the use of MCNP6 and GEANT4 Monte Carlo software when large distances and thicknesses are considered. • The Thermal Neutron Facility (TNF) at TRIUMF used as an example real life example location. • The effects of water, aluminium, iron and lead considered over various thicknesses up to 3 m. - Abstract: A comparison of the Monte Carlo based simulation codes MCNP6-1.0 and GEANT4-10.1 as used for modelling large scale structures is presented here. The high-energy neutron field at the Tri Universities Meson Facility (TRIUMF) in Vancouver, British Columbia is the structure modelled in this work. Work with the emphasis on the modelling of the facility and comparing with experimental results has been published previously, whereas this work is focussed on comparing the performance of the codes over relatively high depths of material rather than the accuracy of the results themselves in comparison to experimental data. Comparisons of three different locations within the neutron facility are modelled and presented using both codes as well as analysis of the transport of typical neutrons fields through large blocks of iron, water, lead and aluminium in order to determine where any deviations are likely to have occurred. Results indicate that over short distances, results from the two codes are in broad agreement – although over greater distances and within more complex geometries, deviation increases dramatically. The conclusions reached are that it is likely the deviations between the codes is caused by both the compounding effect of slight differences between the cross section files used by the two codes to determine the neutron transport through iron, and differences in the processes used by both codes.

  16. Diamond as a solid state micro-fission chamber for thermal neutron detection at the VR-1 research reactor

    Energy Technology Data Exchange (ETDEWEB)

    Pomorski, Michal; Mer-Calfati, Christine [CEA-LIST, Diamond Sensors Laboratory, 91191, Gif-sur-Yvette (France); Foulon, Francois [CEA, National Institute for Nuclear Science and Technology, 91191, Gif-sur-Yvette (France); Sklenka, Lubomir; Rataj, Jan; Bily, Tomas [Department of Nuclear Reactors,Faculty of Nuclear Science and Physical Engineering, Czech Technical University, V. Holesovickach 2, 180 00 PRAHA 8 (Czech Republic)

    2015-07-01

    Diamond exhibits a combination of properties which makes it attractive for neutron detection in hostile conditions. In the particular case of detection in a nuclear reactor, it is resilient to radiation, exhibits a natural low sensitivity to gamma rays, and its small size (as compared with that of gas ionisation chambers) enables fluency monitoring with a high position resolution. We report here on the use of synthetic CVD diamond as a solid state micro-fission chamber with U-235 converting material for in-core thermal neutron monitoring. Two types of thin diamond detectors were developed for this application. The first type of detector is fabricated using thin diamond membrane obtained by etching low-cost commercially available single crystal CVD intrinsic diamond, so called 'optical grade' material. Starting from a few hundred of micrometre thick samples, the sample is sliced with a laser and then plasma etched down to a few tenths of micrometre. Here we report the result obtained with a 17 μm thick device. The detection surface of this detector is equal to 1 mm{sup 2}. Detectors with surfaces up to 1 cm{sup 2} can be fabricated with this technique. The second type of detector is fabricated by growing successively two thin films of diamond, by the microwave enhanced chemical vapour deposition technique, on HPHT single crystal diamond. A first, a film of boron doped (p+) single crystal diamond, a few microns thick, is deposited. Then a second film of intrinsic diamond with a thickness of a few tens of microns is deposited. This results in a P doped, Intrinsic, Metal structure (PIM) structure in which the intrinsic volume id the active part of the detector. Here we report the results obtained with a 20 μm thick intrinsic whose detection surface is equal to 0.5 mm{sup 2}, with the possibility to enlarge the surface of the detector up to 1 cm{sup 2}. These two types of detector were tested at the VR-1 research reactor at the Czech Technical University in

  17. Thermal design of lithium bromide-water solution vapor absorption cooling system for indirect evaporative cooling for IT pod

    Science.gov (United States)

    Sawant, Digvijay Ramkrishna

    Nowadays with increase use of internet, mobile there is increase in heat which ultimately increases the efficient cooling system of server room or IT POD. Use of traditional ways of cooling system has ultimately increased CO2 emission and depletion of CFC's are serious environmental issues which led scientific people to improve cooling techniques and eliminate use of CFC's. To reduce dependency on fossil fuels and 4environmental friendly system needed to be design. For being utilizing low grade energy source such as solar collector and reducing dependency on fossil fuel vapour absorption cooling system has shown a great driving force in today's refrigeration systems. This LiBr-water aabsorption cooling consists of five heat exchanger namely: Evaporator, Absorber, Solution Heat Exchanger, Generator, Condenser. The thermal design was done for a load of 23 kW and the procedure was described in the thesis. There are 120 servers in the IT POD emitting 196 W of heat each on full load and some of the heat was generated by the computer placed inside the IT POD. A detailed procedure has been discussed. A excel spreadsheet was to prepared with varying tube sizes to see the effect on flows and ultimately overall heat transfer coefficient.

  18. Investigation of absorptance and emissivity of thermal control coatings on Mg–Li alloys and OES analysis during PEO process

    Science.gov (United States)

    Yao, Zhongping; Xia, Qixing; Ju, Pengfei; Wang, Jiankang; Su, Peibo; Li, Dongqi; Jiang, Zhaohua

    2016-01-01

    Thermal control ceramic coatings on Mg–Li alloys have been successfully prepared in silicate electrolyte system by plasma electrolytic oxidation (PEO) method. The PEO coatings are mainly composed of crystallized Mg2SiO4 and MgO, which have typical porous structure with some bulges on the surface; OES analysis shows that the plasma temperature, which is influenced by the technique parameters, determines the formation of the coatings with different crystalline phases and morphologies, combined with “quick cooling effect” by the electrolyte; and the electron concentration is constant, which is related to the electric spark breakdown, determined by the nature of the coating and the interface of coating/electrolyte. Technique parameters influence the coating thickness, roughness and surface morphology, but do not change the coating composition in the specific PEO regime, and therefore the absorptance (αS) and emissivity (ε) of the coatings can be adjusted by the technique parameters through changing thickness and roughness in a certain degree. The coating prepared at 10 A/dm2, 50 Hz, 30 min and 14 g/L Na2SiO3 has the minimum value of αS (0.35) and the maximum value of ε (0.82), with the balance temperature of 320 K. PMID:27383569

  19. Ultrafast carrier thermalization and trapping in silicon-germanium alloy probed by extreme ultraviolet transient absorption spectroscopy.

    Science.gov (United States)

    Zürch, Michael; Chang, Hung-Tzu; Kraus, Peter M; Cushing, Scott K; Borja, Lauren J; Gandman, Andrey; Kaplan, Christopher J; Oh, Myoung Hwan; Prell, James S; Prendergast, David; Pemmaraju, Chaitanya D; Neumark, Daniel M; Leone, Stephen R

    2017-07-01

    Semiconductor alloys containing silicon and germanium are of growing importance for compact and highly efficient photonic devices due to their favorable properties for direct integration into silicon platforms and wide tunability of optical parameters. Here, we report the simultaneous direct and energy-resolved probing of ultrafast electron and hole dynamics in a silicon-germanium alloy with the stoichiometry Si0.25Ge0.75 by extreme ultraviolet transient absorption spectroscopy. Probing the photoinduced dynamics of charge carriers at the germanium M4,5-edge (∼30 eV) allows the germanium atoms to be used as reporter atoms for carrier dynamics in the alloy. The photoexcitation of electrons across the direct and indirect band gap into conduction band (CB) valleys and their subsequent hot carrier relaxation are observed and compared to pure germanium, where the Ge direct [Formula: see text] and Si0.25Ge0.75 indirect gaps ([Formula: see text]) are comparable in energy. In the alloy, comparable carrier lifetimes are observed for the X, L, and Γ valleys in the conduction band. A midgap feature associated with electrons accumulating in trap states near the CB edge following intraband thermalization is observed in the Si0.25Ge0.75 alloy. The successful implementation of the reporter atom concept for capturing the dynamics of the electronic bands by site-specific probing in solids opens a route to study carrier dynamics in more complex materials with femtosecond and sub-femtosecond temporal resolution.

  20. Resonance region neutronics of unit cells in fast and thermal reactors

    Energy Technology Data Exchange (ETDEWEB)

    Salehi, A. A.; Driscoll, M. J.; Deutsch, O. L.

    1977-05-01

    A method has been developed for generating resonance-self-shielded cross sections based upon an improved equivalence theorem, which appears to allow extension of the self-shielding-factor (Bondarenko f-factor) method, now mainly applied to fast reactors, to thermal reactors as well. The method is based on the use of simple prescriptions for the ratio of coolant-to-fuel region-averaged fluxes, in the equations defining cell averaged cross sections. Linearization of the dependence of these functions on absorber optical thickness is found to be a necessary and sufficient condition for the existence of an equivalence theorem. Results are given for cylindrical, spherical and slab geometries. The functional form of the flux ratio relations is developed from theoretical considerations, but some of the parameters are adjusted to force-fit numerical results. Good agreement over the entire range of fuel and coolant optical thicknesses is demonstrated with numerical results calculated using the ANISN program in the S/sub 8/P/sub 1/ option.

  1. Thermal neutron capture cross sections resonance integrals and g-factors

    CERN Document Server

    Mughabghab, S F

    2003-01-01

    The thermal radiative capture cross sections and resonance integrals of elements and isotopes with atomic numbers from 1 to 83 (as well as sup 2 sup 3 sup 2 Th and sup 2 sup 3 sup 8 U) have been re-evaluated by taking into consideration all known pertinent data published since 1979. This work has been undertaken as part of an IAEA co-ordinated research project on 'Prompt capture gamma-ray activation analysis'. Westcott g-factors for radiative capture cross sections at a temperature of 300K were computed by utilizing the INTER code and ENDF-B/VI (Release 8) library files. The temperature dependence of the Westcott g-factor is illustrated for sup 1 sup 1 sup 3 Cd, sup 1 sup 2 sup 4 Xe and sup 1 sup 5 sup 7 Gd at temperatures of 150, 294 and 400K. Comparisons have also been made of the newly evaluated capture cross sections of sup 6 Li, sup 7 Li, sup 1 sup 2 C and sup 2 sup 0 sup 7 Pb with those determined by the k sub 0 method.

  2. Neutron scattering. Experiment manuals

    Energy Technology Data Exchange (ETDEWEB)

    Brueckel, Thomas; Heger, Gernot; Richter, Dieter; Roth, Georg; Zorn, Reiner (eds.)

    2010-07-01

    The following topics are dealt with: The thermal triple axis spectrometer PUMA, the high-resolution powder diffractometer SPODI, the hot single-crystal diffractometer HEiDi for structure analysis with neutrons, the backscattering spectrometer SPHERES, neutron polarization analysis with tht time-of-flight spectrometer DNS, the neutron spin-echo spectrometer J-NSE, small-angle neutron scattering with the KWS-1 and KWS-2 diffractometers, the very-small-angle neutron scattering diffractrometer with focusing mirror KWS-3, the resonance spin-echo spectrometer RESEDA, the reflectometer TREFF, the time-of-flight spectrometer TOFTOF. (HSI)

  3. Monte Carlo assessment of soil moisture effect on high-energy thermal neutron capture gamma-ray by {sup 14}N

    Energy Technology Data Exchange (ETDEWEB)

    Pazirandeh, Ali [Physics Department, University of Tehran, Tehran (Iran, Islamic Republic of) and Institute for Theoretical and Applied Physics, Tabriz (Iran, Islamic Republic of)]. E-mail: paziran@ut.ac.ir; Azizi, Maryam [Physics Department, University of Tehran, Tehran (Iran, Islamic Republic of); Institute for Theoretical and Applied Physics, Tabriz (Iran, Islamic Republic of); Farhad Masoudi, S. [Physics Department, University of Tehran, Tehran (Iran, Islamic Republic of); Institute for Theoretical and Applied Physics, Tabriz (Iran, Islamic Republic of)

    2006-01-01

    Among many conventional techniques, nuclear techniques have shown to be faster, more reliable, and more effective in detecting explosives. In the present work, neutrons from a 5 Ci Am-Be neutron source being in water tank are captured by elements of soil and landmine (TNT), namely {sup 14}N, H, C, and O. The prompt capture gamma-ray spectrum taken by a NaI (Tl) scintillation detector indicates the characteristic photo peaks of the elements in soil and landmine. In the high-energy region of the gamma-ray spectrum, besides 10.829 MeV of {sup 15}N, single escape (SE) and double escape (DE) peaks are unmistakable photo peaks, which make the detection of concealed explosive possible. The soil has the property of moderating neutrons as well as diffusing the thermal neutron flux. Among many elements in soil, silicon is more abundant and {sup 29}Si emits 10.607 MeV prompt capture gamma-ray, which makes 10.829 MeV detection difficult. The Monte Carlo simulation was used to adjust source-target-detector distances and soil moisture content to yield the best result. Therefore, we applied MCNP4C for configuration very close to reality of a hidden landmine in soil.

  4. Effect of thermal radiation on free convection flow and heat transfer over a truncated cone in the presence of pressure work and heat generation/absorption

    Directory of Open Access Journals (Sweden)

    Elbashbeshy E.M.A.

    2016-01-01

    Full Text Available Effect of heat generation or absorption and thermal radiation on free convection flow and heat transfer over a truncated cone in the presence of pressure work is considered. The governing boundary layer equations are reduced to non-similarity boundary layer equations and solved numerically by using Mathematica technique. Comparisons with previously published work on special cases of the problem are performed and the results are found to be in excellent agreement. The solutions are presented in terms of local skin friction, local Nusselt number, velocity and temperature profiles for values of Prandtl number, pressure work parameter, radiation parameter and heat generation or absorption parameter.

  5. Preparation and characteristics of epoxy/clay/B4C nanocomposite at high concentration of boron carbide for neutron shielding application

    Science.gov (United States)

    Kiani, Mohammad Amin; Ahmadi, Seyed Javad; Outokesh, Mohammad; Adeli, Ruhollah; Mohammadi, Aghil

    2017-12-01

    In this research, the characteristics of the prepared samples in epoxy matrix by means of X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDS), as well as scanning electron microscope (SEM) are evaluated. Meanwhile, the obtained mechanical properties of the specimen are investigated. Thermogravimetric analysis (TGA) is also employed to evaluate the thermal degradation of manufactured nanocomposites. The thermal neutron absorption properties of nanocomposites containing 3 wt% of montmorillonite nanoclay (closite30B) have been studied experimentally, using an Am-Be point source. Mechanical tests reveal that the higher B4C concentrations, the more tensile strengths, but lower Young's modulus in all samples under consideration. TGA analysis also shows that thermal stability of the nanocomposite, increases in presence of B4C. Finally, neutron absorption analysis shows that increasing the B4C concentration leads to a nonlinearly build-up of neutron absorption cross section.

  6. Modulation of the neutron spectrum for NCTB; Modulacion del espectro de neutrones para TCNB

    Energy Technology Data Exchange (ETDEWEB)

    Medina C, D.; Letechipia de L, C.; Vega C, H. R., E-mail: dmedina_c@hotmail.com [Universidad Autonoma de Zacatecas, Unidad Academica de Estudios Nucleares, Cipres No.10, Fracc. La Penuela, 98068 Zacatecas, Zac. (Mexico)

    2016-09-15

    Cancer is characterized by the uncontrolled growth of differentiated cells in a part of the organism. Currently in the world there are millions of people living with cancer. Glioblastoma multiform e is the most common and most aggressive of brain tumors and is very difficult to treat by conventional surgery, chemotherapy or radiation. The only viable alternative is its treatment through Neutron Capture Therapy in Boron (NCTB), since is a selective therapy that requires a drug with {sup 10}B (a non-radioactive isotope of boron) and a modulated neutron beam. Thermal neutrons are captured by {sup 10}B, because has a large effective section of thermal neutron absorption, in an exothermic reaction forming the nucleus composed of {sup 11}B in an excited state that induces its cleavage in two nuclei: {sup 7}Li and alpha particle ({sup 4}He). This process causes the destruction of cancer cells by direct DNA damage, without damaging normal tissue. One of the problems associated with this therapy is to have a neutron beam with adequate flow and spectrum. The neutron spectrum must be moderated and filtered from the characteristics of the source. To this end, the main sources of neutrons are nuclear research reactors and particle accelerators. The intensity of the flow should be 2 x 10 E{sup 9} n/cm{sup 2}.s, in order to treat the patient in a reasonable time; thus, is interesting to design filters for a radial beam of a TRIGA reactor, where materials such as Cd, Al, Fe and polyethylene are being implemented in the interest of having a spectrum with which the therapy can be implemented. For this design is being played with the position of the materials, to be able to see the behavior of the spectrum and thus choose some arrangement as indicated, of course taking into account the doses of both neutrons and gammas. (Author)

  7. Neutronic Reactor Design to Reduce Neutron Loss

    Science.gov (United States)

    Miles, F. T.

    1961-05-01

    A nuclear reactor construction is described in which an unmoderated layer of the fissionable material is inserted between the moderated portion of the reactor core and the core container steel wall. The wall is surrounded by successive layers of pure fertile material and moderator containing fertile material. The unmoderated layer of the fissionable material will insure that a greater portion of fast neutrons will pass through the steel wall than would thermal neutrons. Since the steel has a smaller capture cross section for the fast neutrons, greater nunnbers of neutrons will pass into the blanket, thereby increasing the over-all efficiency of the reactor. (AEC)

  8. Compact D-D/D-T neutron generators and their applications

    Energy Technology Data Exchange (ETDEWEB)

    Lou, Tak Pui [Univ. of California, Berkeley, CA (United States)

    2003-01-01

    Neutron generators based on the 2H(d,n)3He and 3H(d,n)4He fusion reactions are the most commonly available neutron sources. The applications of current commercial neutron generators are often limited by their low neutron yield and their short operational lifetime. A new generation of D-D/D-T fusion-based neutron generators has been designed at Lawrence Berkeley National Laboratory (LBNL) by using high current ion beams hitting on a self-loading target that has a large surface area to dissipate the heat load. This thesis describes the rationale behind the new designs and their potential applications. A survey of other neutron sources is presented to show their advantages and disadvantages compared to the fusion-based neutron generator. A prototype neutron facility was built at LBNL to test these neutron generators. High current ion beams were extracted from an RF-driven ion source to produce neutrons. With an average deuteron beam current of 24 mA and an energy of 100 keV, a neutron yield of >109 n/s has been obtained with a D-D coaxial neutron source. Several potential applications were investigated by using computer simulations. The computer code used for simulations and the variance reduction techniques employed were discussed. A study was carried out to determine the neutron flux and resolution of a D-T neutron source in thermal neutron scattering applications for condensed matter experiments. An error analysis was performed to validate the scheme used to predict the resolution. With a D-T neutron yield of 1014 n/s, the thermal neutron flux at the sample was predicted to be 7.3 x 105 n/cm2s. It was found that the resolution of cold neutrons was better than that of thermal neutrons when the duty factor is high. This neutron generator could be efficiently used for research and educational purposes at universities. Additional applications studied were positron production and

  9. The axial power distribution validation of the SCWR fuel assembly with coupled neutronics-thermal hydraulics method

    Energy Technology Data Exchange (ETDEWEB)

    Xi, Xi [CNNC Key Laboratory on Nuclear Reactor Thermal Hydraulics Technology, Nuclear Power Institute of China, Chengdu 610041 (China); Xiao, Zejun, E-mail: fabulous_2012@sina.com [CNNC Key Laboratory on Nuclear Reactor Thermal Hydraulics Technology, Nuclear Power Institute of China, Chengdu 610041 (China); Yan, Xiao; Li, Yongliang; Huang, Yanping [CNNC Key Laboratory on Nuclear Reactor Thermal Hydraulics Technology, Nuclear Power Institute of China, Chengdu 610041 (China)

    2013-05-15

    Highlights: ► CFX and MCNP codes are suitable to calculate the axial power profile of the FA. ► The partition method in the calculation will affect the final result. ► The density feedback has little effect on the axial power profile of CSR1000 FA. -- Abstract: SCWR (super critical water reactor) is one of the IV generation nuclear reactors in the world. In a typical SCWR the water enters the reactor from the cold leg with a temperature of 280 °C and then leaves the core with a temperature of 500 °C. Due to the sharp change in temperature, there is a huge density change of the water along the axial direction of the fuel assembly (FA), which will affect the moderating power of the water. So the axial power distribution of the SCWR FA could be different from the traditional PWR FA.In this paper, it is the first time that the thermal hydraulics code CFX and neutronics code MCNP are used to analyze the axial power distribution of the SCWR FA. First, the factors in the coupled method which could affect the result are analyzed such as the initialization value or the partition method especially in the MCNP code. Then the axial power distribution of the Europe HPLWR FA is obtained by the coupled method with the two codes and the result is compared with that obtained by Waata and Reiss. There is a good agreement among the three kinds of results. At last, this method is used to calculate the axial power distribution of the Chinese SCWR (CSR1000) FA. It is found the axial power profile of the CSR1000 FA is not so sensitive to the change of the moderator density.

  10. Measure of thermal neutron flux in the IPEN/MB-01 reactor using {sup 197} Au wire activation detectors; Medida do fluxo de neutrons termicos do reator IPEN/MB-01 com detectores de ativacao de fios de {sup 197} Au

    Energy Technology Data Exchange (ETDEWEB)

    Marques, Andre Luis Ferreira

    1995-12-31

    This dissertation has aimed at developing a neutron flux measurement technique by means of detectors activation analysis. The main task of this work was the implementation of this thermal neutron flux measurement technique, using gold wires as activation detectors in the IPEN/MB-01 reactor core. The neutron thermal flux spatial distribution was obtained by gold wire activation technique, with wire diameters of 0.125 mm and 0.250 mm in seven selected reactor experimental channels. The values of thermal flux were about 10{sup 9} neutrons/cm{sup 2}.s. This experiment has been the first one conducted with gold wires in the IPEN/MB-01 reactor, being this technique implemented for use by experiments in flux mapping of the core 73 refs., 60 figs., 31 tabs.

  11. The potential use of synthetic profiles of thermal neutrons decay time; O potencial de uso de perfis sinteticos de tempo de decaimento de neutrons termais

    Energy Technology Data Exchange (ETDEWEB)

    Tinoco, Franciso Lopes

    1994-12-31

    The Time Lapse Technique used for monitoring the water and gas movement in a reservoir needs a PNC - Pulsed Neutron Capture Log - base log to be matched. However, few wells have this base log run in unchanged water saturation conditions. This paper presents two alternatives to be used a a base log: a synthetic PNC log and the initial gamma ray log. Some examples are presented to illustrate these techniques. (author). 1 ref., 6 figs., 2 tabs.

  12. Evaluation of defects induced by neutron radiation in reactor pressure vessels steels; Evaluacion de los defectos inducidos por la radiacion neutronica en los aceros de vasijas

    Energy Technology Data Exchange (ETDEWEB)

    Lopez Jimenez, J.

    1978-07-01

    We have developed a method for calculating the production of neutron induced defects (depleted zone and crowdions) in ferritic pressure vessel steels for different neutron spectra. They have been analysed both the recoil primary atoms produced by elastic and inelastic collisions with fast neutrons and the ones produced by gamma-ray emission by thermal neutron absorption. Theoretical modelling of increasing in the ductile-brittle transition temperature of ferritic steels has been correlated with experimental data at irradiation temperature up to 400 degree centigree (Author) 15 refs.

  13. High-resolution spectroscopy of 32P . (II). Level density and primary transition strengths observed after thermal neutron capture in 31P

    Science.gov (United States)

    Michaelsen, S.; Winter, Ch.; Lieb, K. P.; Krusche, B.; Robinson, S.; Von Egidy, T.

    1989-09-01

    The -γ-ray spectrum emitted after thermal neutron capture in 31P was studied at the ILL high flux reactor with a pair spectrometer and an intrinsic Ge detector. A total of 212 transitions were assigned to the decay of 32P and 155 of these, representing 96.7% of the observed flux, were placed in a level scheme of 38 states. The neutron binding energy was determined as 7935.74 (16) keV. The densities of states observed in this reaction and in a recent (d, p) study are analyzed in the constant temperature Fermi-gas model. The primary E1 and M1 transition strengths in 32P are discussed and are compared to other sd-shell nuclei.

  14. Ultrafast carrier thermalization and trapping in silicon-germanium alloy probed by extreme ultraviolet transient absorption spectroscopy

    Directory of Open Access Journals (Sweden)

    Michael Zürch

    2017-07-01

    Full Text Available Semiconductor alloys containing silicon and germanium are of growing importance for compact and highly efficient photonic devices due to their favorable properties for direct integration into silicon platforms and wide tunability of optical parameters. Here, we report the simultaneous direct and energy-resolved probing of ultrafast electron and hole dynamics in a silicon-germanium alloy with the stoichiometry Si0.25Ge0.75 by extreme ultraviolet transient absorption spectroscopy. Probing the photoinduced dynamics of charge carriers at the germanium M4,5-edge (∼30 eV allows the germanium atoms to be used as reporter atoms for carrier dynamics in the alloy. The photoexcitation of electrons across the direct and indirect band gap into conduction band (CB valleys and their subsequent hot carrier relaxation are observed and compared to pure germanium, where the Ge direct ( Δ E gap , Ge , direct = 0.8   eV and Si0.25Ge0.75 indirect gaps ( Δ E gap , Si 0.25 Ge 0.75 , indirect = 0.95   eV are comparable in energy. In the alloy, comparable carrier lifetimes are observed for the X, L, and Γ valleys in the conduction band. A midgap feature associated with electrons accumulating in trap states near the CB edge following intraband thermalization is observed in the Si0.25Ge0.75 alloy. The successful implementation of the reporter atom concept for capturing the dynamics of the electronic bands by site-specific probing in solids opens a route to study carrier dynamics in more complex materials with femtosecond and sub-femtosecond temporal resolution.

  15. Thermal radiation and heat generation/absorption effects on viscoelastic double-diffusive convection from an isothermal sphere in porous media

    Directory of Open Access Journals (Sweden)

    S. Abdul Gaffar

    2015-09-01

    Full Text Available Buoyancy-driven convective heat and mass transfer in boundary layer flow of a viscoelastic Jeffrey fluid from a permeable isothermal sphere embedded in a porous medium is studied. Thermal radiation flux and heat generation/absorption are also incorporated in the model. A non-Darcy drag force model is employed to simulate the effects of linear porous media drag and second order Forchheimer drag. The Rosseland diffusion algebraic approximation is utilized to simulate thermal radiation effects. The non-dimensionalized boundary layer equations are solved using implicit, finite-difference scheme. The influence of Darcy number (Da, Deborah number (De, ratio of relaxation to retardation times (λ, radiation parameter (F, Forchheimer inertial parameter (Λ and heat generation/absorption parameter (Δ, on normalized velocity, temperature, concentration, skin friction, heat and mass transfer rates are also studied. The present study has applications in the storage of nuclear waste materials.

  16. Zinc Absorption from Milk Is Affected by Dilution but Not by Thermal Processing, and Milk Enhances Absorption of Zinc from High-Phytate Rice in Young Dutch Women.

    Science.gov (United States)

    Talsma, Elise F; Moretti, Diego; Ly, Sou Chheng; Dekkers, Renske; van den Heuvel, Ellen Ghm; Fitri, Aditia; Boelsma, Esther; Stomph, Tjeerd Jan; Zeder, Christophe; Melse-Boonstra, Alida

    2017-06-01

    Background: Milk has been suggested to increase zinc absorption. The effect of processing and the ability of milk to enhance zinc absorption from other foods has not been measured directly in humans. Objective: We aimed to assess zinc absorption from 1 ) milk undergoing various processing and preparatory steps and 2 ) from intrinsically labeled high-phytate rice consumed with milk or water. Methods: Two randomized crossover studies were conducted in healthy young women [age:18-25 y; body mass index (in kg/m 2 ): 20-25]: 1 ) a milk study ( n = 19) comparing the consumption of 800 mL full-fat ultra-high temperature (UHT) milk [heat-treated milk (HTM)], full-fat UHT milk diluted 1:1 with water [heat-treated milk and water (MW)], water, or unprocessed (raw) milk (UM), each extrinsically labeled with 67 Zn, and 2 ) a rice study ( n = 18) comparing the consumption of 90 g intrinsically 67 Zn-labeled rice with 600 mL of water [rice and water (RW)] or full-fat UHT milk [rice and milk (RM)]. The fractional absorption of zinc (FAZ) was measured with the double-isotope tracer ratio method. In vitro, we assessed zinc extraction from rice blended into water, UM, or HTM with or without phytate. Results: FAZ from HTM was 25.5% (95% CI: 21.6%, 29.4%) and was not different from UM (27.8%; 95% CI: 24.2%, 31.4%). FAZ from water was higher (72.3%; 95% CI: 68.7%, 75.9%), whereas FAZ from MW was lower (19.7%; 95% CI: 17.5%, 21.9%) than HTM and UM (both P Milk enhanced human FAZ from high-phytate rice by 62% compared with water. Diluting milk with water decreases its absorption-enhancing proprieties, whereas UHT processing does not. This trial was registered at the Dutch trial registry as NTR4267 (http://www.trialregister.nl/trialreg/admin/rctview.asp?TC=4267). © 2017 American Society for Nutrition.

  17. Characterization of the physico-chemical properties of polymeric materials for aerospace flight. [differential thermal and atomic absorption spectroscopic analysis of nickel cadmium batteries

    Science.gov (United States)

    Rock, M.

    1981-01-01

    Electrodes and electrolytes of nickel cadmium sealed batteries were analyzed. Different thermal analysis of negative and positive battery electrodes was conducted and the temperature ranges of occurrence of endotherms indicating decomposition of cadmium hydroxide and nickel hydroxide are identified. Atomic absorption spectroscopy was used to analyze electrodes and electrolytes for traces of nickel, cadmium, cobalt, and potassium. Calibration curves and data are given for each sample analyzed. Instrumentation and analytical procedures used for each method are described.

  18. Numerical investigation of MHD free convection flow of a non-Newtonian fluid past an impulsively started vertical plate in the presence of thermal diffusion and radiation absorption

    Directory of Open Access Journals (Sweden)

    M. Umamaheswar

    2016-09-01

    Full Text Available A numerical investigation is carried out on an unsteady MHD free convection flow of a well-known non-Newtonian visco elastic second order Rivlin-Erickson fluid past an impulsively started semi-infinite vertical plate in the presence of homogeneous chemical reaction, thermal radiation, thermal diffusion, radiation absorption and heat absorption with constant mass flux. The presence of viscous dissipation is also considered at the plate under the influence of uniform transverse magnetic field. The flow is governed by a coupled nonlinear system of partial differential equations which are solved numerically by using finite difference method. The effects of various physical parameters on the flow quantities viz. velocity, temperature, concentration, Skin friction, Nusselt number and Sherwood number are studied numerically. The results are discussed with the help of graphs. We observed that the velocity decreases with an increase in magnetic field parameter, Schmidt number, and Prandtl number while it increases with an increase in Grashof number, modified Grashof number, visco-elastic parameter and Soret number. Temperature increases with an increase in radiation absorption parameter, Eckert number and visco-elastic parameter while it decreases with increasing values of radiation parameter, Prandtl number and heat absorption parameter. Concentration increases with increase in Soret number while it decreases with an increase in Schmidt number and chemical reaction parameter.

  19. Measurement of thermal neutron cross-sections and resonance integrals for sup 7 sup 1 Ga(n,gamma) sup 7 sup 2 Ga and sup 7 sup 5 As(n,gamma) sup 7 sup 6 As by using sup 2 sup 4 sup 1 Am-Be isotopic neutron source

    CERN Document Server

    Karadag, M; Tan, M; Oezmen, A

    2003-01-01

    Thermal neutron cross-sections and resonance integrals for the sup 7 sup 1 Ga(n,gamma) sup 7 sup 2 Ga and sup 7 sup 5 As(n,gamma) sup 7 sup 6 As reactions were measured by the activation method. The experimental samples with and without a cylindrical Cd shield case in 1 mm wall thickness were irradiated in an isotropic neutron field of the sup 2 sup 4 sup 1 Am-Be neutron source. The induced activities in the samples were measured by high-resolution gamma-ray spectrometry with a calibrated reverse-electrode germanium detector. Thermal neutron cross-sections for 2200 m/s neutrons and resonance integrals for the sup 7 sup 1 Ga(n,gamma) sup 7 sup 2 Ga and sup 7 sup 5 As(n,gamma) sup 7 sup 6 As reactions have been obtained relative to the reference values, sigma sub 0 =13.3+-0.1 b and I sub 0 =14.0+-0.3 b for the sup 5 sup 5 Mn(n,gamma) sup 5 sup 6 Mn reaction as a single comparator. The necessary correction factors for gamma attenuation, thermal neutron and resonance neutron self-shielding effects were taken into...

  20. Measurement of the neutron capture cross section of the fissile isotope 235U with the CERN n{sub T}OF Total Absorption Calorimeter and fission tagging based on micromegas detectors

    Energy Technology Data Exchange (ETDEWEB)

    Balibrea, J.; Mendoza, E.; Cano-Ott, D.; Berthomieux, E.; Guerrero, C.; TOF Collaboration

    2015-07-01

    The future nuclear technologies require accurate nuclear data on neutron-induced capture cross sections and α ratios of fissile isotopes. The measurement of their cross section present several difficulties, most of them related to the larger fission γ-ray background competing with the weaker γ-ray cascades from the capture reactions used as signal. A specific setup was used for the measurement of 235U capture cross section at the CERN n{sub T}OF facility in 2012. The setup consists of a set of micromegas fission detectors surrounding the 235U samples all placed inside a segmented BaF2 Total Absorption Calorimeter. (Author)

  1. A study on structure defects in irradiated lithium fluoride (thermal neutrons); Etude des imperfections de structure du fluorure de lithium irradie (neutrons thermiques)

    Energy Technology Data Exchange (ETDEWEB)

    Lambert, M

    1958-06-19

    A study was made of the behavior of atomic defects, vacancies and interstitials, generated from the Li{sup 6}(n,{alpha})H{sup 3} reaction in Lip crystals. Defects appear as cavities and platelets around ten angstrom in size and increase both with neutron dose and annealing temperature. For longer irradiations, metallic lithium precipitates out, in epitaxy with LiF lattice, and later, lithium salts appear due to the penetration of atmospheric gases through the cracks present in the damaged crystal. Various x-ray experiments followed the formation and evolution of these imperfections when their atomic concentration reached 10{sup -4}. (author)

  2. Optimization study and neutronic and thermal-hydraulic design calculations of a 75 KWTH aqueous homogeneous reactor for medical isotopes production

    Energy Technology Data Exchange (ETDEWEB)

    Perez, Daniel Milian; Lorenzo, Daniel E. Milian; Garcia, Lorena P. Rodriguez; Llanes, Jesus Salomon; Hernandez, Carlos R. Garcia, E-mail: dperez@instec.cu, E-mail: dmilian@instec.cu, E-mail: lorenapilar@instec.cu, E-mail: cgh@instec.cu [Instituto Superior de Tecnologias y Ciencias Aplicadas (InSTEC), La Habana (Cuba); Lira, Carlos A. Brayner de Oliveira, E-mail: cabol@ufpe.br [Universidade Federal de Pernambuco (UFPE), Recife (Brazil); Rodriguez, Manuel Cadavid, E-mail: mcadavid2001@yahoo.com [Tecnologia Nuclear Medica Spa, TNM (Chile)

    2015-07-01

    {sup 99m}Tc is the most common radioisotope used in nuclear medicine. It is a very useful radioisotope, which is used in about 30-40 million procedures worldwide every year. Medical diagnostic imaging techniques using {sup 99m}Tc represent approximately 80% of all nuclear medicine procedures. Although {sup 99m}Tc can be produced directly on a cyclotron or other type of particle accelerator, currently is almost exclusively produced from the beta-decay of its 66-h parent {sup 99}Mo. {sup 99}Mo production system in an Aqueous Homogeneous Reactor (AHR) is potentially advantageous because of its low cost, small critical mass, inherent passive safety, and simplified fuel handling, processing and purification characteristics. In this paper, an AHR conceptual design using Low Enriched Uranium (LEU) is studied and optimized for the production of {sup 99}Mo. Aspects related with the neutronic behavior such as optimal reflector thickness, critical height, medical isotopes production and the reactivity feedback introduced in the solution by the volumetric expansion of the fuel solution due to thermal expansion of the fuel solution and the void volume generated by radiolytic gas bubbles were evaluated. Thermal-hydraulics studies were carried out in order to show that sufficient cooling capacity exists to prevent fuel overheating. The neutronic and thermal-hydraulics calculations have been performed with the MCNPX computational code and the version 14 of ANSYS CFX respectively. The neutronic calculations demonstrated that the reactor is able to produce 370 six-day curies of {sup 99}Mo in 5 days operation cycles and the CFD simulation demonstrated that the heat removal systems provide sufficient cooling capacity to prevent fuel overheating, the maximum temperature reached by the fuel (89.29 deg C) was smaller to the allowable temperature limit (90 deg C). (author)

  3. Gamma Rossi-alpha, Feynman-alpha and Gamma Differential Die-Away concepts as a potential alternative/complement to the traditional thermal neutron based analysis in Safeguards

    CERN Document Server

    Chernikova, Dina; Trnjanin, Nermin; Axell, Kåre; Nordlund, Anders

    2015-01-01

    A new concept for thermal neutron based correlation and multiplicity measurements is proposed in this paper. The main idea of the concept consists of using 2.223 MeV gammas (or 1.201 MeV, DE) originating in the 1H(n,gamma)2D-reaction instead of using traditional thermal neutron counting. Results of investigations presented in this paper indicate that gammas from thermal neutron capture reaction preserve the information about the correlation characteristics of thermal (fast) neutrons in the same time scale. Therefore, instead of thermal neutron detectors (or as a complement) one may use traditional and inexpensive gamma detectors, such NaI, BGO, CdZnTe or any other gamma detectors. In this work we used D8x8 cm2 NaI scintillator to test the concept. Thus, the new approach helps to address the problem of replacement of 3He-counters and problems related to the specific measurements of spent nuclear fuel directly in the spent fuel pool. It has a particular importance for nuclear safeguards and security. Overall, t...

  4. Development of a thermal neutron-sensitive liposome for a novel drug delivery system aiming for radio-chemo-concurrent cancer therapy

    Energy Technology Data Exchange (ETDEWEB)

    Akamatsu, Ken [Radiation Effect Analysis Group, Nuclear Science and Engineering Directorate, Japan Atomic Energy Agency, 2-4 Shirakatashirane, Tokai, Naka, Ibaraki 319-1195 (Japan)], E-mail: akamatsu.ken@jaea.go.jp

    2009-12-15

    A thermal neutron-sensitive liposome has been developed focusing on irradiation site-specific-controlled release of a medicine. We recommended a {sup 10}B-borocaptate dimer as a detonator of liposome in expectation of effects of low-energy heavy ions produced by {sup 10}B(n, {alpha}){sup 7}Li reaction. As a result, an X-ray-sensitive liposome incorporating the detonator was vulnerable enough to release an anticancer agent, carboplatin, at a dose/dose-rate near clinical use. These results reveal, moreover, that the liposomes are also applicable to a heavy-ion beam.

  5. Digital signal processing for a thermal neutron detector using ZnS(Ag):6LiF scintillating layers read out with WLS fibers and SiPMs

    Science.gov (United States)

    Mosset, J.-B.; Stoykov, A.; Greuter, U.; Hildebrandt, M.; Schlumpf, N.

    2016-07-01

    We present a digital signal processing system based on a photon counting approach which we developed for a thermal neutron detector consisting of ZnS(Ag):6LiF scintillating layers read out with WLS fibers and SiPMs. Three digital filters have been evaluated: a moving sum, a moving sum after differentiation and a digital CR-RC4 filter. The performances of the detector with these filters are presented. A full analog signal processing using a CR-RC4 filter has been emulated digitally. The detector performance obtained with this analog approach is compared with the one obtained with the best performing digital approach.

  6. Analysis of the eigenvalue equations in k, lambda,. gamma. , and. cap alpha. applied to some fast- and thermal-neutron systems

    Energy Technology Data Exchange (ETDEWEB)

    Velarde, G.; Ahnert, C.; Aragones, J.M.

    1978-06-01

    The time-dependent Boltzmann equation for neutron transport is transformed into eigenvalue equations in k, lambda, ..gamma.., and ..cap alpha.., whose general properties are stated as hypotheses. Numerical solutions are obtained with the discrete-ordinates code DTF, where a direct lambda eigenvalue calculation has been added. Eigenvalues and eigenfunctions are analyzed for idealized fast and thermal systems in both bare and reflected configurations. The differences found in these idealized cases provide some useful bases for estimating the behavior of the different eigenvalue solutions in specific applications.

  7. Measurement of the fission cross-section of {sup 235}U and {sup 239}Pu for thermal neutrons; Mesures des sections de fission de {sup 235}U et de {sup 239}Pu en neutrons thermiques

    Energy Technology Data Exchange (ETDEWEB)

    Fraysse, G.; Prosdocimi, A.; Netter, F.; Samour, C. [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1965-07-01

    Improved techniques of fast detection have been applied for determining the fission cross-sections of {sup 235}U and {sup 239}Pu with reference to the absorption cross-section of Boron. Monochromatic neutron beams of 0.0322 eV, 0.0626 eV and 0.275 eV have been employed. Use has been made of a Xe-filled gaseous scintillator and of a low-geometry solid state ion chamber. Both measured alpha and fission rates. The results at the reference energy of 0.0253 eV are: ({sigma}{sub F}){sub 0} {sup 235}U = 588 {+-} 10 barns ({sigma}{sub F}){sub 0} {sup 239}Pu = 738 {+-} 7 barns. (authors) [French] Des techniques avancees de comptage rapide ont ete mise en oeuvre pour determiner la section efficace de fission de {sup 235}U et de {sup 239}Pu par rapport a celle d'absorption du bore. Des faisceaux de neutrons monochromatiques de 0,0322 eV, 0,0626 eV et 0,275 eV ont ete employes. Les detecteurs utilises sont un scintillateur gazeux rempli de xenon et une chambre d'ionisation a etat solide a basse geometrie. Les deux ont mesure les taux des desintegrations alpha et des fissions. Les resultats a l'energie de reference de 0,0253 eV sont: ({sigma}{sub F}){sub 0} {sup 235}U = 588 {+-} 10 barns ({sigma}{sub F}){sub 0} {sup 239}Pu = 738 {+-} 7 barns. (auteurs)

  8. Theoretical Time Dependent Thermal Neutron Spectra and Reaction Rates in H{sub 2}O and D{sub 2}O

    Energy Technology Data Exchange (ETDEWEB)

    Purohit, S.N.

    1966-04-15

    The early theoretical and experimental time dependent neutron thermalization studies were limited to the study of the transient spectrum in the diffusion period. The recent experimental measurements of the time dependent thermal neutron spectra and reaction rates, for a number of moderators, have generated considerable interest in the study of the time dependent Boltzmann equation. In this paper we present detailed results for the time dependent spectra and the reaction rates for resonance detectors using several scattering models of H{sub 2}O and D{sub 2}O. This study has been undertaken in order to interpret the integral time dependent neutron thermalization experiments in liquid moderators which have been performed at the AB Atomenergi. The proton gas and the deuteron gas models are inadequate to explain the measured reaction rates in H{sub 2}O and D{sub 2}O. The bound models of Nelkin for H{sub 2}O and of Butler for D{sub 2}O give much better agreement with the experimental results than the gas models. Nevertheless, some disagreement between theoretical and experimental results still persists. This study also indicates that the bound model of Butler and the effective mass 3. 6 gas model of Brown and St. John give almost identical reaction rates. It is also surprising to note that the calculated reaction rate for Cd for the Butler model appears to be in better agreement with the experimental results of D{sub 2}O than of the Nelkin model with H{sub 2}O experiments. The present reaction rate studies are sensitive enough so as to distinguish between the gas model and the bound model of a moderator. However, to investigate the details of a scattering law (such as the effect of the hindered rotations in H{sub 2}O and D{sub 2}O and the weights of different dynamical modes) with the help of these studies would require further theoretical as well as experimental investigations. Theoretical results can be further improved by improving the source for thermal neutrons, the

  9. Report to the DOE nuclear data committee. [EV RANGE 10-100; CROSS SECTIONS; PHOTONEUTRONS; NEUTRONS; GAMMA RADIATION; COUPLED CHANNEL THEORY; DIFFERENTIAL CROSS SECTIONS; MEV RANGE 01-10; ; CAPTURE; GAMMA SPECTRA; THERMAL NEUTRONS; COMPUTER CALCULATIONS; DECAY; FISSION PRODUCTS; FISSION YIELD; SHELL MODELS; NUCLEAR DATA COLLECTIONS

    Energy Technology Data Exchange (ETDEWEB)

    Struble, G.L.; Haight, R.C.

    1981-03-01

    Topics covered include: studies of (n, charged particle) reactions with 14 to 15 MeV neutrons; photoneutron cross sections for /sup 15/N; neutron radiative capture; Lane-model analysis of (p,p) and (n,n) scattering on the even tin isotopes; neutron scattering cross sections for /sup 181/Ta, /sup 197/Au, /sup 209/Bi, /sup 232/Th, and /sup 238/U inferred from proton scattering and charge exchange cross sections; neutron-induced fission cross sections of /sup 245/Cm and /sup 242/Am; fission neutron multiplicities for /sup 245/Cm and /sup 242/Am; the transport of 14 MeV neutrons through heavy materials 150 < A < 208; /sup 249/Cm energy levels from measurement of thermal neutron capture gamma rays; /sup 231/Th energy levels from neutron capture gamma ray and conversion electron spectroscopy; new measurements of conversion electron binding energies in berkelium and californium; nuclear level densities; relative importance of statistical vs. valence neutron capture in the mass-90 region; determination of properties of short-lived fission products; fission yield of /sup 87/Br and /sup 137/I from 15 nuclei ranging from /sup 232/Th to /sup 249/Cf; evaluation of charged particle data for the ECPL library; evaluation of secondary charged-particle energy and angular distributions for ENDL; and evaluated nuclear structure libraries derived from the table of isotopes. (GHT)

  10. Measurement of thermal neutron cross section and resonance integral of the reaction {sup 135}Cs(n,{gamma}){sup 136}Cs

    Energy Technology Data Exchange (ETDEWEB)

    Katoh, Toshio; Nakamura, Shoji; Harada, Hideo [Power Reactor and Nuclear Fuel Development Corp., Tokyo (Japan); Hatsukawa, Yuichi; Shinohara, Nobuo; Hata, Kentaro; Kobayashi, Katsutoshi; Motoishi, Shoji; Tanase, Masakazu

    1997-03-01

    The thermal neutron(2,200 m/s neutron) capture cross section({sigma}{sub 0}) and the resonance integral(I{sub 0}) of the reaction {sup 135}Cs(n,{gamma}){sup 136}Cs were measured by an activation method. Targets of radioactive cesium, which include {sup 135}Cs, {sup 137}Cs and stable {sup 133}Cs, were irradiated with reactor neutrons within or without a Cd shield case. The ratio of the number of nuclei of {sup 135}Cs to that of {sup 137}Cs was measured with a quadrupole mass spectrometer. This ratio and the ratio of activity of {sup 136}Cs to that of {sup 137}Cs were used for deduction of the {sigma}{sub 0} and the I{sub 0} of {sup 135}Cs. The {sigma}{sub 0} and the I{sub 0} of the reaction {sup 135}Cs(n,{sigma}){sup 136}Cs were 8.3 {+-} 0.3 barn and 38.1 {+-} 2.6 barn, respectively. (author)

  11. Experiments and Simulations of the Use of Time-Correlated Thermal Neutron Counting to Determine the Multiplication of an Assembly of Highly Enriched Uranium

    Energy Technology Data Exchange (ETDEWEB)

    David L. Chichester; Mathew T. Kinlaw; Scott M. Watson; Jeffrey M. Kalter; Eric C. Miller; William A. Noonan

    2014-11-01

    A series of experiments and numerical simulations using thermal-neutron time-correlated measurements has been performed to determine the neutron multiplication, M, of assemblies of highly enriched uranium available at Idaho National Laboratory. The experiments used up to 14.4 kg of highly-enriched uranium, including bare assemblies and assemblies reflected with high-density polyethylene, carbon steel, and tungsten. A small 252Cf source was used to initiate fission chains within the assembly. Both the experiments and the simulations used 6-channel and 8-channel detector systems, each consisting of 3He proportional counters moderated with polyethylene; data was recorded in list mode for analysis. 'True' multiplication values for each assembly were empirically derived using basic neutron production and loss values determined through simulation. A total of one-hundred and sixteen separate measurements were performed using fifty-seven unique measurement scenarios, the multiplication varied from 1.75 to 10.90. This paper presents the results of these comparisons and discusses differences among the various cases.

  12. Neutron irradiation effects on plasma facing materials

    Science.gov (United States)

    Barabash, V.; Federici, G.; Rödig, M.; Snead, L. L.; Wu, C. H.

    2000-12-01

    This paper reviews the effects of neutron irradiation on thermal and mechanical properties and bulk tritium retention of armour materials (beryllium, tungsten and carbon). For each material, the main properties affected by neutron irradiation are described and the specific tests of neutron irradiated armour materials under thermal shock and disruption conditions are summarized. Based on current knowledge, the expected thermal and structural performance of neutron irradiated armour materials in the ITER plasma facing components are analysed.

  13. Measurement of the thermal neutron capture cross section and the resonance integral of the sup 1 sup 0 sup 9 Ag(n, gamma) sup 1 sup 1 sup 0 sup m Ag reaction

    CERN Document Server

    Nakamura, S; Shcherbakov, O A; Furutaka, K; Harada, H; Katoh, T

    2003-01-01

    In order to develop a neutron flux monitor for long-term neutron irradiation, the thermal neutron (2,200 m/s neutron) capture cross section (sigma sub 0) and the resonance integral (I sub 0) of the sup 1 sup 0 sup 9 Ag(n, gamma) sup 1 sup 1 sup 0 sup m Ag reaction were measured by the activation and gamma-ray spectroscopic methods. Silver foils were irradiated with and without a Cd shield capsule at the Rikkyo Research Reactor. The Co/Al and Au/Al alloy wires were irradiated together with silver foils in order to monitor the thermal neutron flux and the fraction of the epi-thermal neutron part (Westcott's index). A high purity Ge detector was used for the gamma-ray measurements of the irradiated samples. The sigma sub 0 and the I sub 0 of the sup 1 sup 0 sup 9 Ag(n, gamma) sup 1 sup 1 sup 0 sup m Ag reaction are 4.12+-0.10 b and 67.9+-3.1 b, respectively. The sigma sub 0 is 12% smaller than the tabulated one (4.7+-0.2 b). On the other hand, the I sub 0 is in agreement with the tabulated one (72.3+-4.0 b) with...

  14. Neutron thermalization in quality control of asphalts content in mixtures for paving. Adaptation of nuclear densimeters for this purpose; La termalizacion de neutrones en el control de calidad de contenido de asfalto en mezclas para pavimentos. Adaptacion de densimetros nucleares para tal fin

    Energy Technology Data Exchange (ETDEWEB)

    Bravo R, T.; Montanez M, P.O. [Instituto de Investigaciones y Formacion Avanzada, Boyaca (Colombia). Facultad de Ciencias. Lab. Nuclear

    1995-12-31

    This paper shows how the neutron source of the nuclear densimeters, used for measure the humidity, can be used for measuring and making the quality control of the asphalt percentage in mixtures used for street paving. The measures are based in the neutronic thermalization processes, because the hydrogen is the main part of chemical composition of the asphalts. A calibration method for the equipment is presented. (author). 6 refs, 3 figs, 3 tabs.

  15. Simultaneous counting of α-, β(γ)-rays and thermal neutrons with phoswich detectors consisting of ZnS(Ag), 6Li-glass and/or NE102A scintillators

    Science.gov (United States)

    Usuda, Shigekazu

    1995-02-01

    Simultaneous counting of α-, β(including γ)-rays and thermal neutrons was realized by combining doubly or triply ZnS(Ag) film, NS8 6Li glass and/or NE102A plastic scintillators with or without Au Mylar (Au-coated Mylar films). The Au Mylar was used as an optical ND filter to discriminate thermal neutrons detected with the NS8 from α-rays detected with the ZnS(Ag) in pulse height by interposing behind the ZnS(Ag). The other discriminations were achieved by pulse shape analysis. Satisfactory discrimination among α-, β(γ)-rays and thermal neutrons was obtained with the ZnS(Ag)/Au Mylar/NS8 and ZnS(Ag)/NE102A/NS8 phoswiches. Discrimination characteristics of the devised phoswiches were described.

  16. Performance analysis of single stage libr-water absorption machine operated by waste thermal energy of internal combustion engine: Case study

    Science.gov (United States)

    Sharif, Hafiz Zafar; Leman, A. M.; Muthuraman, S.; Salleh, Mohd Najib Mohd; Zakaria, Supaat

    2017-09-01

    Combined heating, cooling, and power is also known as Tri-generation. Tri-generation system can provide power, hot water, space heating and air -conditioning from single source of energy. The objective of this study is to propose a method to evaluate the characteristic and performance of a single stage lithium bromide-water (LiBr-H2O) absorption machine operated with waste thermal energy of internal combustion engine which is integral part of trigeneration system. Correlations for computer sensitivity analysis are developed in data fit software for (P-T-X), (H-T-X), saturated liquid (water), saturated vapor, saturation pressure and crystallization temperature curve of LiBr-H2O Solution. Number of equations were developed with data fit software and exported into excel work sheet for the evaluation of number of parameter concerned with the performance of vapor absorption machine such as co-efficient of performance, concentration of solution, mass flow rate, size of heat exchangers of the unit in relation to the generator, condenser, absorber and evaporator temperatures. Size of vapor absorption machine within its crystallization limits for cooling and heating by waste energy recovered from exhaust gas, and jacket water of internal combustion engine also presented in this study to save the time and cost for the facilities managers who are interested to utilize the waste thermal energy of their buildings or premises for heating and air conditioning applications.

  17. Changes in graphite coefficient of thermal expansion due to fast neutron irradiation and applied stress in the temperature range 300C-1200C

    Energy Technology Data Exchange (ETDEWEB)

    Marsden, B.J. [AEA Technology Plc, Risley, Warrington, Cheshire (United Kingdom); Arai, Taketoshi [Oarai Research Establishment, Japan Atomic Energy Research Institute JAERI, Ibaraki-ken (Japan); McLachlan, N. [Nuclear Electric Ltd, Edinburgh, Scotland (United Kingdom)

    1998-09-01

    Changes in coefficient of thermal expansion (CTE) in nuclear graphite are important because they are related to dimensional change and the thermal stressing of graphite moderated reactor graphite components. The CTE of nuclear graphite can be modified by fast neutron irradiation, stress and creep strain. Various theories exist which relate the CTE of the individual graphite crystallite to the CTE of the polycrystalline graphite through a structure factor. This structure factor is a function of the graphite crystal orientation and the accommodation available due to local crystal porosity. The porosity can be taken up by raising the temperature of the graphite, which causes the lattice `c` spacing to expand, or by fast neutron irradiation induced crystal dimensional changes. It is also proposed that this porosity can be taken up by stressing unirradiated graphite, although there appears to be some evidence from Japan that the anisotropy of graphite is also altered by pre-stress. Annealing of creep strain specimens has shown that not all of irradiation induced creep strain is responsible for modifying CTE. 12 refs.

  18. The study of sup 1 sup 0 sup 5 Pd(n,gamma) sup 1 sup 0 sup 6 Pd reaction with thermal neutrons

    CERN Document Server

    Miah, M M H; Harada, H; Nakamura, S

    2002-01-01

    This is a report about the study of sup 1 sup 0 sup 5 Pd(n,gamma) sup 1 sup 0 sup 6 Pd reaction with thermal neutrons performed by Dr. M.M.H.Miah, who was engaged in the investigation as a visiting research associate of Japan Nuclear Cycle Development Institute (JNC) under the STA fellowship program for the periods ranging from January 2001 to July 2002, together with members belong to System Design Analysis Group of JNC. The investigation of sup 1 sup 0 sup 5 Pd(n,gamma) sup 1 sup 0 sup 6 Pd reaction has been performed by using the prompt gamma-ray spectroscopic technique to supply basic data for the nuclear transmutation. Samples of natural Pd and enriched sup 1 sup 0 sup 5 Pd were irradiated separately with the B-4 thermal neutron guide facilities at Kyoto University Research Reactor Institute (KURRI). Capture prompt gamma-rays were detected in both singles and coincidence modes by using two high purity Ge detectors. By analyzing gamma-gamma coincidence data, 42 cascading gamma-transitions were identified ...

  19. Coulomb and even-odd effects in cold and super-asymmetric fragmentation for thermal neutron induced fission of {sup 235}U

    Energy Technology Data Exchange (ETDEWEB)

    Montoya, M. [Universidad Nacional de Ingeniería, Av. Túpac Amaru 210, Rímac, Lima (Peru)

    2016-07-07

    Even-odd effects of the maximal total kinetic energy (K{sub max}) as a function of charge (Z) and mass (A) of fragments from thermal neutron induced fission of actinides are questioned by other authors. In this work, visiting old results on thermal neutron induced fission of {sup 235}U, those even-odd effects are reconfirmed. The cases seeming to contradict even-odd effects are interpreted with the Coulomb effect hypothesis. According to Coulomb effect hypothesis, K{sub max} is equal to the Coulomb interaction energy of the most compact scission configuration. As a consequence, between two isobaric charge splits with similar Q-values, the more asymmetrical one will get the more compact scission configuration and then it will reach the higher K{sub max}-value. In some cases, the more asymmetrical charge split corresponds, by coincidence, to an odd charge split; consequently its higher K{sub max}-value may be misinterpreted as anti-even-odd effect. Another experimental result reported in the literature is the increasing of even-odd effects on charge distribution on the more asymmetrical fragmentations region. In this region, the difference between K{sub max} and Q-values increases with asymmetry, which means that the corresponding scission configuration needs higher total deformation energy to occur. Higher deformation energy of the fragments implies lower free energy to break nucleon pairs. Consequently, in the asymmetric fragmentation region, the even-odd effects of the distribution of proton number and neutron number must increase with asymmetry.

  20. Extraction of pure thermal neutron beam for the proposed PGNAA facility at the TRIGA research reactor of AERE, Savar, Bangladesh

    Science.gov (United States)

    Alam, Sabina; Zaman, M. A.; Islam, S. M. A.; Ahsan, M. H.

    1993-10-01

    A study on collimators and filters for the design of a spectrometer for prompt gamma neutron activation analysis (PGNAA) at one of the radial beamports of the TRIGA Mark II reactor at AERE, Savar has been carried out. On the basis of this study a collimator and a filter have been designed for the proposed PGNAA facility. Calculations have been done for measuring neutron flux at various positions of the core of the reactor using the computer code TRIGAP. Gamma dose in the core of the reactor has also been measured experimentally using TLD technique in the present work.

  1. Production of a {sup 44} Ti target and its cross section of thermal neutron capture; Producao de um alvo de {sup 44} Ti e sua secao de choque para captura de neutrons termicos

    Energy Technology Data Exchange (ETDEWEB)

    Ejnisman, R

    1993-12-31

    A study of the production of a {sup 44} Ti target was carried out aiming the determination of its thermal neutron capture cross-section. With this purpose, the cross-section of the reaction {sup 45} Sc(p,2 n) {sup 44} Ti was determined in the energies 16-, 18-, 20-22- and 45 MeV. The cross-section of the reactions (p,n) {sup 45} Ti, (p,pn) {sup 44m} Sc, (p,pn) {sup 44g} Sc and (p,p2n){sup 43} Sc were also measured. The results in the low energy region are in good agreement with a previous work by McGee et al. On the other hand, the cross-section at 45 MeV is different from McGee`s result and indicates the existence of an abnormal behavior of the excitation function at higher energies. Furthermore, a radiochemical separation method was developed in order to eliminate Sc from the {sup 44} Ti target which was irradiated with neutrons. It was possible to determine an upper limit for the cross-section of the reaction {sup 44} Ti (n, {gamma}) of 4 x 10{sup 3} b. At last, it is presented a discussion of the results obtained and their possible astrophysical implications. (author) 94 refs.

  2. Survey of boron detectors for thermal neutrons operating in the non proportional regime; Etude de detecteurs a bore pour neutrons thermiques fonctionnant en regime non proportionnel

    Energy Technology Data Exchange (ETDEWEB)

    Vacarie, J. [Commissariat a l' Energie Atomique, 38 - Grenoble (France). Centre d' Etudes Nucleaires

    1968-07-01

    In gas counters, the alternative of directly detecting (i.e. without using the phenomenon of multiplication the charges ionized by the reaction {sup 10}B (n,{alpha}){sup 7}Li, offers many advantages as to the conception of such a detector. After examining the ionization phenomenon and deducing the characteristics of low-noise amplifiers, various prototypes are studied. - The D.I.N. 5/4, intended for fast neutrons detector, grants leave to have good isotropic proprieties thanks to its geometry and good sensitivity imputable to the BF{sub 3} filling pressure of 1 atm. - A flat counter (D.E.H. type), with plane and parallel electrodes, grants leave to work out a low height of influence, soil moisture measurer. The confrontation between various filling pressures (0.5, 1, 2, 3 atm.) points out the importance of attachment in BF{sub 3}. - Thanks to neutronic diffraction counter (C.D.N. 2 type) filled under 2 atm and parallelepiped, one can considerably reduce the weight of the goniometer protection, and lightly increase its sensitivity. - The results given by the experimental boron coating device have allowed to build a boron coating counter to be used in current collection. (author) [French] Dans les compteurs a gaz, la possibilite de detecter directement (c'est-a-dire sans utiliser le phenomene de multiplication) les charges ionisees lors de la reaction {sup 10}B (n,{alpha}){sup 7}Li offre de nombreux avantages pour la conception de detecteurs a bore. Apres avoir examine les phenomenes d'ionisation et en avoir deduit les caracteristiques de la chaine d'amplification faible-bruit, on etudie les differents prototypes developpes. - Le D.I.N. 5/4 destine a une sonde de neutrons rapides, permet d'avoir une bonne isotropie grace a sa geometrie et une bonne sensibilite due a sa pression de remplissage de 1 atm. en BF{sub 3}. - Un compteur plat (type D.E.H.) a electrodes planes et paralleles permet de realiser un humidimetre a faible hauteur d

  3. Neutron imaging and tomography with MCPS

    NARCIS (Netherlands)

    Duarte Pinto, S.C.; Ortega, R; Ritzau, S.; Pasquale, D; Laprade, B.; Mrotek, S.; Gardell, S.; Zhou, Z.; Plomp, J.; van Eijck, L.; Bilheux, H.; Dhiman, I.

    2017-01-01

    A neutron imaging detector based on neutron-sensitive microchannel plates (mcps) was constructed and tested at beamlines of thermal and cold neutrons. The mcps are made of a glass mixture containing 10B and natural Gd, which makes the bulk of the mcp an efficient neutron converter. Contrary to the

  4. Neutron detectors for the ESS diffractometers

    Czech Academy of Sciences Publication Activity Database

    Stefanescu, I.; Christensen, M.; Fenske, J.; Hall-Wilton, R.; Henry, P. F.; Kirstein, O.; Muller, M.; Nowak, G.; Pooley, D.; Raspino, D.; Rhodes, N.; Šaroun, Jan; Schefer, J.; Schooneveld, E.; Sykora, J.; Schweika, W.

    2017-01-01

    Roč. 12, JAN (2017), č. článku P01019. ISSN 1748-0221 R&D Projects: GA MŠk LM2015048 Institutional support: RVO:61389005 Keywords : instrumentation for neutron sources * neutron diffraction detectors * neutron detectors (cold, thermal, fast neutrons) Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.220, year: 2016

  5. INFLUENCE OF SCATTERED NEUTRON RADIATION ON METROLOGICAL CHARACTERISTICS OF АТ140 NEUTRON CALIBRATION FACILITY

    Directory of Open Access Journals (Sweden)

    D. I. Komar

    2017-01-01

    Full Text Available Today facilities with collimated radiation field are widely used as reference in metrological support of devices for neutron radiation measurement. Neutron fields formed by radionuclide neutron sources. The aim of this research was to study characteristics of experimentally realized neutron fields geometries on АТ140 Neutron Calibration Facility using Monte Carlo method.For calibration, we put a device into neutron field with known flux density or ambient equivalent dose rate. We can form neutron beam from radionuclide fast-neutron source in different geometries. In containercollimator of АТ140 Neutron Calibration Facility we can install special inserts to gather fast-neutron geometry or thermal-neutron geometry. We need to consider neutron scattering from air and room’s walls. We can conduct measurements of neutron field characteristics in several points and get the other using Monte Carlo method.Thermal neutron collimator forms a beam from radionuclide source with a significant amount of neutrons with thermal energies. From found relationship between full neutron flux and distance to neutron source we see that inverse square law is violated. Scattered radiation contribution into total flux increases when we are moving away from neutron source and significantly influences neutron fields characteristics. While source is exposed in shadow-cone geometry neutron specter has pronounced thermal component from wall scattering.In this work, we examined main geometry types used to acquire reference neutron radiation using radionuclide sources. We developed Monte Carlo model for 238Pu-Be neutron source and АТ140 Neutron Calibration Facility’s container-collimator. We have shown the most significant neutron energy distribution factor to be scattered radiation from room’s walls. It leads to significant changes of neutron radiation specter at a distance from the source. When planning location, and installing the facility we should consider

  6. Positron source based on neutron capture

    Science.gov (United States)

    Hugenschmidt, C.; Kögel, G.; Repper, R.; Schreckenbach, K.; Sperr, P.; Triftshäuser, W.

    2003-10-01

    A positron beam based on absorption of high-energy prompt γ-rays from thermal neutron capture in 113Cd was installed at a neutron guide of the High Flux Reactor at the ILL in Grenoble. The positron source consists of platinum foils acting as γ-e +e --converter and positron moderator. After acceleration to 3 keV by electrical lenses the positrons were magnetically guided through the beamline. Measurements were performed for various source geometries. The beam diameter and moderation characteristics such as positron work function, moderation efficiency and degradation were determined as well. The results lead to an optimised design of the in-pile positron source which will be implemented at the Munich research reactor FRM-II.

  7. Prototype Stilbene Neutron Collar

    Energy Technology Data Exchange (ETDEWEB)

    Prasad, M. K. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Shumaker, D. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Snyderman, N. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Verbeke, J. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Wong, J. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

    2016-10-26

    A neutron collar using stilbene organic scintillator cells for fast neutron counting is described for the assay of fresh low enriched uranium (LEU) fuel assemblies. The prototype stilbene collar has a form factor similar to standard He-3 based collars and uses an AmLi interrogation neutron source. This report describes the simulation of list mode neutron correlation data on various fuel assemblies including some with neutron absorbers (burnable Gd poisons). Calibration curves (doubles vs 235U linear mass density) are presented for both thermal and fast (with Cd lining) modes of operation. It is shown that the stilbene collar meets or exceeds the current capabilities of He-3 based neutron collars. A self-consistent assay methodology, uniquely suited to the stilbene collar, using triples is described which complements traditional assay based on doubles calibration curves.

  8. Gold nanoparticles production using reactor and cyclotron based methods in assessment of (196,198)Au production yields by (197)Au neutron absorption for therapeutic purposes.

    Science.gov (United States)

    Khorshidi, Abdollah

    2016-11-01

    Medical nano-gold radioisotopes is produced regularly using high-flux nuclear reactors, and an accelerator-driven neutron activator can turn out higher yield of (197)Au(n,γ)(196,198)Au reactions. Here, nano-gold production via radiative/neutron capture was investigated using irradiated Tehran Research Reactor flux and also simulated proton beam of Karaj cyclotron in Iran. (197)Au nano-solution, including 20nm shaped spherical gold and water, was irradiated under Tehran reactor flux at 2.5E+13n/cm(2)/s for (196,198)Au activity and production yield estimations. Meanwhile, the yield was examined using 30MeV proton beam of Karaj cyclotron via simulated new neutron activator containing beryllium target, bismuth moderator around the target, and also PbF2 reflector enclosed the moderator region. Transmutation in (197)Au nano-solution samples were explored at 15 and 25cm distances from the target. The neutron flux behavior inside the water and bismuth moderators was investigated for nano-gold particles transmutation. The transport of fast neutrons inside bismuth material as heavy nuclei with a lesser lethargy can be contributed in enhanced nano-gold transmutation with long duration time than the water moderator in reactor-based method. Cyclotron-driven production of βeta-emitting radioisotopes for brachytherapy applications can complete the nano-gold production technology as a safer approach as compared to the reactor-based method. Copyright © 2016 Elsevier B.V. All rights reserved.

  9. Measurements of the neutron capture cross sections and incineration potentials of minor-actinides in high thermal neutron fluxes: Impact on the transmutation of nuclear wastes; Mesures des sections efficaces de capture et potentiels d'incineration des actinides mineurs dans les hauts flux de neutrons: Impact sur la transmutation des dechets

    Energy Technology Data Exchange (ETDEWEB)

    Bringer, O

    2007-10-15

    This thesis comes within the framework of minor-actinide nuclear transmutation studies. First of all, we have evaluated the impact of minor actinide nuclear data uncertainties within the cases of {sup 241}Am and {sup 237}Np incineration in three different reactor spectra: EFR (fast), GT-MHR (epithermal) and HI-HWR (thermal). The nuclear parameters which give the highest uncertainties were thus highlighted. As a result of fact, we have tried to reduce data uncertainties, in the thermal energy region, for one part of them through experimental campaigns in the moderated high intensity neutron fluxes of ILL reactor (Grenoble). These measurements were focused onto the incineration and transmutation of the americium-241, the curium-244 and the californium-249 isotopes. Finally, the values of 12 different cross sections and the {sup 241}Am isomeric branching ratio were precisely measured at thermal energy point. (author)

  10. Numerical solution of Williamson fluid flow past a stretching cylinder and heat transfer with variable thermal conductivity and heat generation/absorption

    Directory of Open Access Journals (Sweden)

    M. Y. Malik

    2016-03-01

    Full Text Available In this article, Williamson fluid flow and heat transfer over a stretching cylinder is discussed. The thermal conductivity is assumed to be vary linearly with temperature. Heat generation/absorption effects are also taken into account. Modeled partial differential equations are converted into ordinary differential form by using appropriate transformations. Shooting method in conjunction with Runge-Kutta-Fehlberg method is used to find the solution of the problem. Moreover, the effects of different flow parameters γ, λ, ϵ, β and Pr on velocity and temperature profiles are shown graphically. Local Nusselt number and skin friction coefficient are shown in tabular and graphical form.

  11. Terrestrial Neutrons in West Zone II Building on Ito Campus

    OpenAIRE

    Naher, Kamrun; Ikeda, Nobuo; Fukuda, Hiroaki; Iwamoto, Hiroki; Fukui, Yoshinori; Koba, Yusuke; Imamura, Minoru; Uozumi, Yusuke

    2009-01-01

    Thermal and fast neutrons were measured inside the West Zone II building on Ito Campus for the assessment of terrestrial neutrons in a stand alone concrete building. Ratios of count rate of thermal neutrons to that of fast neutrons were almost constant inside the building. The contribution of fast neutrons across outside wall has been discussed. A simple method to estimate the neutron flux near the outside wall has been proposed.

  12. Water absorption and viscosity behaviour of thermally stable novel graft copolymer of carboxymethyl cellulose and poly(sodium 1-hydroxy acrylate).

    Science.gov (United States)

    Kumar, Bijender; Negi, Yuvraj Singh

    2018-02-01

    A novel thermally stable hydrolysed carboxymethyl cellulose-g-poly(sodium 1-hydroxy acrylate) i.e. CMC-g-PNaHA graft copolymer was synthesized from the CMC and vinyl monomer 5-methylene-2-isopropyl-1,3-dioxolan-4-one (MD) in an aqueous medium using an initiator followed by transformation of resulting CMC-g-PMD via alkaline hydrolysis. The graft copolymerization is confirmed by the Fourier transform infrared spectroscopy (FT-IR), Nuclear magnetic resonance spectroscopy (NMR) and X-ray diffractometer (XRD). The influence of the CMC and PNaHA content on the properties of the resulting hydrolysed CMC-g-PNaHA graft copolymer was investigated. In comparison with the PNaHA polymer, the resulted hydrolysed CMC-g-PNaHA grafted copolymer has improved thermal stability, water absorption properties, viscosity and weight-average molecular weight. Copyright © 2017 Elsevier Ltd. All rights reserved.

  13. Temperature-dependent absorption cross-sections in the thermal infrared bands of SF{sub 5}CF{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Rinsland, C.P. E-mail: c.p.rinsland@larc.nasa.gov; Sharpe, S.W.; Sams, R.L

    2003-12-15

    Absorption cross-sections have been measured at five temperatures between 213 and 323 K in the infrared bands of SF{sub 5}CF{sub 3}. The spectra were recorded at a resolution of 0.112 cm{sup -1} using a commercial Fourier transform infrared spectrometer and a 20 cm temperature-controlled sample cell. Samples of SF{sub 5}CF{sub 3} were pressurized with high-purity nitrogen to a total pressure of 1013.3 hPa (760 Torr). Six or more spectra with varying SF{sub 5}CF{sub 3} column amounts were analyzed at each temperature. The full spectral range of the measurements was 520-6500 cm{sup -1}, with only weak bands observed beyond 1400 cm{sup -1}. Absorption of thermal radiation in the 8-12 {mu}m atmospheric window region being important for climate change, we report here the integrated cross-sections of the significant absorption bands in that spectral region. Our results closely match room temperature values reported previously. Only small variation of the integrated absorption cross-sections with temperature was found. Our results confirm the accuracy of the previous measurements, which find SF{sub 5}CF{sub 3} important for global climate change on a per molecule basis. Absorption cross-sections derived from a single, near Doppler-limited spectrum recorded at room temperature do not show any rotational fine structure in the 700-950 cm{sup -1} region.

  14. Effect of self-bias on the elemental composition and neutron absorption of boron carbide films deposited by RF plasma enhanced CVD

    Energy Technology Data Exchange (ETDEWEB)

    Bute, A., E-mail: butearundhati@gmail.com [Laser and Plasma Technology Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085 (India); Jagannath, E-mail: ssai@barc.gov.in [Technical Physics Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085 (India); Kar, R., E-mail: rajibkar@barc.gov.in [Laser and Plasma Technology Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085 (India); Chopade, S.S., E-mail: supriyagindalkar@rediffmail.com [Laser and Plasma Technology Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085 (India); Desai, S.S., E-mail: ssdesai@barc.gov.in [Solid State Physics Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085 (India); Deo, M.N., E-mail: mndeo@barc.gov.in [High Pressure and Synchrotron Radiation Physics Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085 (India); Rao, Pritty, E-mail: praocccm@rediffmail.com [The National Centre for Compositional Characterization of Materials, Hyderabad (India); Chand, N., E-mail: naresh@barc.gov.in [Laser and Plasma Technology Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085 (India); Kumar, S., E-mail: sanjivcccm@rediffmail.com [The National Centre for Compositional Characterization of Materials, Hyderabad (India); Singh, K., E-mail: singhkw@barc.gov.in [Fusion Reactor Material Section, Bhabha Atomic Research Centre, Trombay, Mumbai 400085 (India); Patil, D.S., E-mail: dspatil@iitb.ac.in [Department of Metallurgical Engineering and Materials Science, Indian Institute of Technology Bombay, Mumbai 400076 (India); Sinha, S., E-mail: ssinha@barc.gov.in [Laser and Plasma Technology Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085 (India)

    2016-10-01

    Boron carbide films are increasingly being investigated for their application in new generation neutron detectors. It is implemented as conversion layer for neutrons and emerging as a potential alternative to {sup 3}He based detectors. This work reports synthesis of boron carbide (B{sub x}C) films from ortho-carborane (o-C{sub 2}B{sub 10}H{sub 12}) by rad