MC2-2: a code to calculate fast neutron spectra and multigroup cross sections
International Nuclear Information System (INIS)
Henryson, H. II; Toppel, B.J.; Stenberg, C.G.
1976-06-01
MC 2 -2 is a program to solve the neutron slowing down problem using basic neutron data derived from the ENDF/B data files. The spectrum calculated by MC 2 -2 is used to collapse the basic data to multigroup cross sections for use in standard reactor neutronics codes. Four different slowing down formulations are used by MC 2 -2: multigroup, continuous slowing down using the Goertzel-Greuling or Improved Goertzel-Greuling moderating parameters, and a hyper-fine-group integral transport calculation. Resolved and unresolved resonance cross sections are calculated accounting for self-shielding, broadening and overlap effects. This document provides a description of the MC 2 -2 program. The physics and mathematics of the neutron slowing down problem are derived and detailed information is provided to aid the MC 2 -2 user in preparing input for the program and implementation of the program on IBM 370 or CDC 7600 computers
MC2-2, Calculation of Fast Neutron Spectra and Multigroup Cross-Sections from ENDF/B Data
International Nuclear Information System (INIS)
2001-01-01
1 - Description of program or function: MC 2 -2 solves the neutron slowing-down equations using basic neutron data derived from ENDF/B data files to determine fundamental mode spectra for use in generating multigroup neutron cross sections. The current edition includes the ability to treat all ENDF/B-V and -VI data representations. It accommodates high-order P scattering representations and provides numerous capabilities such as isotope mixing, delayed neutron processing, free-format input, and flexibility in output data selection. This edition supersedes previous releases of the MC22 program and the earlier MC2 program. Improved physics algorithms and increased computational efficiency are incorporated. Input data files required by MC2-2 may be generated from ENDF/B data by the code ETOE-2. The hyper-fine-group integral transport theory module of MC2-2, RABANL, is an improved version of the RABBLE/RABID codes. Many of the MC2-2 modules are used in the SDX code. 2 - Methods: The extended transport P1, B1, consistent P1, and consistent B1 fundamental mode ultra-fine-group equations are solved using continuous slowing-down theory and multigroup methods. Fast and accurate resonance integral methods are used in the narrow resonance resolved and unresolved resonance treatments. A fundamental mode homogeneous unit cell calculation is performed using either a multigroup or a continuous slowing-down treatment. Multigroup neutron homogeneous cross sections are generated in an ISOTXS format for an arbitrary group structure. A hyper-fine-group integral transport slowing down calculation (RABANL) is available as an option. RABANL performs a homogeneous or heterogeneous (pin or slab) unit cell calculation over the resonance region (resolved and unresolved) and generates multigroup neutron cross sections in an ISOTXS format. Neutron cross sections are generated by RABANL for the homogeneous unit cell and for each heterogeneous region in the pin or slab unit cell calculation
Energy Technology Data Exchange (ETDEWEB)
Matausek, M V [Boris Kidric Institute of Nuclear Sciences Vinca, Beograd (Yugoslavia)
1968-06-15
Programme MULTI calculates the space energy distribution of thermal neutrons in a multizone, cylindrical, infinitely long reactor lattice by using the multigroup or multipoint P{sub 3} approximation. This report presents a short description of the algorithm and the programme and gives the instructions for its exploitation. (author)
TEMPEST-2, Thermalization Program for Neutron Spectra and Multigroup Cross-Sections
International Nuclear Information System (INIS)
Gowins, G.
1984-01-01
Description of problem or function: TEMPEST2 is a neutron thermalization program based upon the Wigner-Wilkins approximation for light moderators and the Wilkins approximation for heavy moderators. A Maxwellian distribution may also be used. The model used may be selected as a function of energy. The second-order differential equations are integrated directly rather than transformed to the Riccati equation. The program provides microscopic and macroscopic cross-section averages over the thermal neutron spectrum
Multigroup or multipoint thermal neutron data preparation. Programme SIGMA
International Nuclear Information System (INIS)
Matausek, M.V.; Kunc, M.
1974-01-01
When calculating the space energy distribution of thermal neutrons in reactor lattices, in either the multigroup or the multipoint approximation, it is convenient to divide the problem into two independent parts. Firstly, for all material regions of the given reactor lattice cell, the group or the point values of cross sections, scattering kernel and the outer source of thermal neutrons are calculated by a data preparation programme. These quantities are then used as input, by the programme which solves multigroup or multipoint transport equations, to generate the space energy neutron spectra in the cell considered and to determine the related integral quantities, namely the different reaction rates. The present report deals with the first part of the problem. An algorithm for constructing a set of thermal neutron input data, to be used with the multigroup or multipoint version of the code MULTI /1,2,3/, is presented and the new version of the programme SIGMA /4/, written in FORTRAN IV for the CDC-3600 computer, is described. For a given reactor cell material, composed of a number of different isotopes, this programme calculates the group or the point values of the scattering macroscopic absorption cross section, macroscopic scattering cross section, kernel and the outer source of thermal neutrons. Numerous options are foreseen in the programme, concerning the energy variation of cross sections and a scattering kernel, concerning the weighting spectrum in multigroup scheme or the procedure for constructing the scattering matrix in the multipoint scheme and, finally, concerning the organization of output. The details of the calculational algorithm are presented in Section 2 of the paper. Section 3 contains the description of the programme and the instructions for its use (author)
Multi-group neutron transport theory
International Nuclear Information System (INIS)
Zelazny, R.; Kuszell, A.
1962-01-01
Multi-group neutron transport theory. In the paper the general theory of the application of the K. M. Case method to N-group neutron transport theory in plane geometry is given. The eigenfunctions (distributions) for the system of Boltzmann equations have been derived and the completeness theorem has been proved. By means of general solution two examples important for reactor and shielding calculations are given: the solution of a critical and albedo problem for a slab. In both cases the system of singular integral equations for expansion coefficients into a full set of eigenfunction distributions has been reduced to the system of Fredholm-type integral equations. Some results can be applied also to some spherical problems. (author) [fr
International Nuclear Information System (INIS)
Erradi, L.; Karouani, K.
1994-01-01
Many multigroup neutron cross section libraries have been processed from basic evaluated nuclear data for use in neutron dosimetry, reactor shielding calculation and in the development of fusion reactors. Most of these libraries have been tested only for fission spectra and were not validated for fusion spectra. Fifteen of these libraries such as DOSCROS84, IRDF85 and ENDFB5 have been used along with the neutron spectra unfolding code SAND II to evaluate about fifteen threshold detector saturated activities. The comparison between these computed activities and the measured ones of a set of foils placed in different places along the axis of a paraffin cylinder and irradiated by 14 MeV neutrons generated by a D-T source, hence giving rise to complex spectra, leads to different types of discrepancies. The analysis of these discrepancies allows to select from these libraries the ones that can be recommended. 1 fig., 4 refs. (author)
The isotope density inverse problem in multigroup neutron transport
International Nuclear Information System (INIS)
Zazula, J.M.
1981-01-01
The inverse problem for stationary multigroup anisotropic neutron transport is discussed in order to search for isotope densities in multielement medium. The spatial- and angular-integrated form of neutron transport equation, in terms of the flux in a group - density of an element spatial correlation, leads to a set of integral functionals for the densities weighted by the group fluxes. Some methods of approximation to make the problem uniquently solvable are proposed. Particularly P 0 angular flux information and the spherically-symetrical geometry of an infinite medium are considered. The numerical calculation using this method related to sooner evaluated direct problem data gives promising agreement with primary densities. This approach would be the basis for further application in an elemental analysis of a medium, using an isotopic neutron source and a moving, energy-dependent neutron detector. (author)
International Nuclear Information System (INIS)
Stamatelatos, M.G.; England, T.R.
1977-05-01
FPDCYS and FPSPEC are two FORTRAN computer programs used at the Los Alamos Scientific Laboratory (LASL), in conjunction with the CINDER-10 program, for calculating cumulative fission-product beta and/or gamma multigroup spectra in arbitrary energy structures, and for arbitrary neutron irradiation periods and cooling times. FPDCYS processes ENDF/B-IV fission-product decay energy data to generate multigroup beta and gamma spectra from individual ENDF/B-IV fission-product nuclides. FPSPEC further uses these spectra and the corresponding nuclide activities calculated by the CINDER-10 code to produce cumulative beta and gamma spectra in the same energy grids in which FPDCYS generates individual isotope decay spectra. The code system consisting of CINDER-10, FPDCYS, and FPSPEC has been used for comparisons with experimental spectra and continues to be used at LASL for generating spectra in special user-oriented group structures. 3 figures
International Nuclear Information System (INIS)
Buxerolle, M.; Massoutie, M.; Kurdjian, J.
1987-09-01
Neutron dosimetry problems have arisen as a result of developments in the applications of nuclear energy. The largest number of possible irradiation situations has been collected: they are presented in the form of a compilation of 44 neutron spectra. Diagrams show the variations of energy fluence and energy fluence weighted by the dose equivalent/fluence conversion factor, with the logarithm of the corresponding energy. The equivalent dose distributions are presented as percentages for the following energy bins: 0.01 eV/0.5 eV/50 keV/1 MeV/5 MeV/15 MeV. The dose equivalent, the mean energy and the effective energy for the dose equivalent for 1 neutron cm -2 are also given [fr
Complex of two-dimensional multigroup programs for neutron-physical computations of nuclear reactor
International Nuclear Information System (INIS)
Karpov, V.A.; Protsenko, A.N.
1975-01-01
Briefly stated mathematical aspects of the two-dimensional multigroup method of neutron-physical computation of nuclear reactor. Problems of algorithmization and BESM-6 computer realisation of multigroup diffuse approximations in hexagonal and rectangular calculated lattices are analysed. The results of computation of fast critical assembly having complicated composition of the core are given. The estimation of computation accuracy of criticality, neutron fields distribution and efficiency of absorbing rods by means of computer programs developed is done. (author)
Application of direct discrete method (DDM) to multigroup neutron transport problems
International Nuclear Information System (INIS)
Vosoughi, Naser; Salehi, Ali Akbar; Shahriari, Majid
2003-01-01
The Direct Discrete Method (DDM), which produced excellent results for one-group neutron transport problems, has been developed for multigroup energy. A multigroup neutron transport discrete equation has been produced for a cylindrical shape fuel element with and without associated coolant regions with two boundary conditions. The calculations are illustrated for two-group energy by graphs showing the fast and thermal fluxes. The validity of the results are tested against the results obtained by the ANISN code. (author)
Neutron-photon multigroup cross sections for neutron energies up to 400 MeV: HILO86R
International Nuclear Information System (INIS)
Kotegawa, Hiroshi; Nakane, Yoshihiro; Hasegawa, Akira; Tanaka, Shun-ichi
1993-02-01
A macroscopic multigroup cross section library of 66 neutron and 22 photon groups for neutron energies up to 400 MeV: HILO86R is prepared for 10 typical shielding materials; water, concrete, iron, air, graphite, polyethylene, heavy concrete, lead, aluminum and soil. The library is a revision of the DLC-119/HILO86, in which only the cross sections below 19.6 MeV have been exchanged with a group cross section processed from the JENDL-3 microscopic cross section library. In the HILO86R library, self shielding factors are used to produce effective cross sections for neutrons less than 19.6 MeV considering rather coarse energy meshes. Energy spectra and dose attenuation in water, concrete and iron have been compared among the HILO, HILO86 and HILO86R libraries for different energy neutron sources. Significant discrepancy has been observed in the energy spectra less than a couple of MeV energy in iron among the libraries, resulting large difference in the dose attenuation. The difference was attributed to the effect of self-shielding factor, namely to the difference between infinite dilution and effective cross sections. Even for 400 MeV neutron source the influence of the self-shielding factor is significant, nevertheless only the cross sections below 19.6 MeV are exchanged. (author)
The problem of resonance self-shielding effect in neutron multigroup calculations
International Nuclear Information System (INIS)
Wang Qingming; Huang Jinghua
1991-01-01
It is not allowed to neglect the resonance self-shielding effect in hybrid blanket and fast reactor neutron designs. The authors discussed the importance as well as the method of considering the resonance self-shielding effect in hybrid blanket and fast reactor neutron multigroup calculations
Proposal to extend CSEWG neutron and photon multigroup structures for wider applications
International Nuclear Information System (INIS)
LaBauve, R.J.; Wilson, W.B.
1976-02-01
The 239-group neutron multigroup structure recommended by the Codes and Formats Subcommittee of the cross section evaluation working group (CSEWG) for use in LMFBR design is not well suited for application in certain other areas, particularly thermal reactor design. This report describes a proposal for a neutron group structure consisting of 347 groups, which is an extension of the CSEWG group structure into the thermal range, and also includes more detail in other energy ranges important in LWR, HTGR, GCFR, and CTR design. Similarly, a proposed extension of the CSEWG 94-group photon multigroup structure to 103 groups is described. A subset of the neutron multigroup structure, consisting of 154 groups and for use in power reactor studies, is also presented
Proposal to extend CSEWG neutron and photon multigroup structures for wider applications. [Tables
Energy Technology Data Exchange (ETDEWEB)
LaBauve, R.J.; Wilson, W.B.
1976-02-01
The 239-group neutron multigroup structure recommended by the Codes and Formats Subcommittee of the cross section evaluation working group (CSEWG) for use in LMFBR design is not well suited for application in certain other areas, particularly thermal reactor design. This report describes a proposal for a neutron group structure consisting of 347 groups, which is an extension of the CSEWG group structure into the thermal range, and also includes more detail in other energy ranges important in LWR, HTGR, GCFR, and CTR design. Similarly, a proposed extension of the CSEWG 94-group photon multigroup structure to 103 groups is described. A subset of the neutron multigroup structure, consisting of 154 groups and for use in power reactor studies, is also presented.
An accurate solution of point reactor neutron kinetics equations of multi-group of delayed neutrons
International Nuclear Information System (INIS)
Yamoah, S.; Akaho, E.H.K.; Nyarko, B.J.B.
2013-01-01
Highlights: ► Analytical solution is proposed to solve the point reactor kinetics equations (PRKE). ► The method is based on formulating a coefficient matrix of the PRKE. ► The method was applied to solve the PRKE for six groups of delayed neutrons. ► Results shows good agreement with other traditional methods in literature. ► The method is accurate and efficient for solving the point reactor kinetics equations. - Abstract: The understanding of the time-dependent behaviour of the neutron population in a nuclear reactor in response to either a planned or unplanned change in the reactor conditions is of great importance to the safe and reliable operation of the reactor. In this study, an accurate analytical solution of point reactor kinetics equations with multi-group of delayed neutrons for specified reactivity changes is proposed to calculate the change in neutron density. The method is based on formulating a coefficient matrix of the homogenous differential equations of the point reactor kinetics equations and calculating the eigenvalues and the corresponding eigenvectors of the coefficient matrix. A small time interval is chosen within which reactivity relatively stays constant. The analytical method was applied to solve the point reactor kinetics equations with six-groups delayed neutrons for a representative thermal reactor. The problems of step, ramp and temperature feedback reactivities are computed and the results compared with other traditional methods. The comparison shows that the method presented in this study is accurate and efficient for solving the point reactor kinetics equations of multi-group of delayed neutrons
Multigroup neutron transport equation in the diffusion and P{sub 1} approximation
Energy Technology Data Exchange (ETDEWEB)
Obradovic, D [Boris Kidric Institute of nuclear sciences Vinca, Belgrade (Yugoslavia)
1970-07-01
Investigations of the properties of the multigroup transport operator, width and without delayed neutrons in the diffusion and P{sub 1} approximation, is performed using Keldis's theory of operator families as well as a technique . recently used for investigations into the properties of the general linearized Boltzmann operator. It is shown that in the case without delayed neutrons, multigroup transport operator in the diffusion and P{sub 1} approximation possesses a complete set of generalized eigenvectors. A formal solution to the initial value problem is also given. (author)
International Nuclear Information System (INIS)
Smith, L.A.; Gehin, J.C.; Worley, B.A.; Renier, J.P.
1994-01-01
The FOEHN critical experiments were analyzed to validate the use of multigroup cross sections in the design of the Advanced Neutron Source. Eleven critical configurations were evaluated using the KENO, DORT, and VENTURE neutronics codes. Eigenvalue and power density profiles were computed and show very good agreement with measured values
MCFT: a program for calculating fast and thermal neutron multigroup constants
International Nuclear Information System (INIS)
Yang Shunhai; Sang Xinzeng
1993-01-01
MCFT is a program for calculating the fast and thermal neutron multigroup constants, which is redesigned from some codes for generation of thermal neutron multigroup constants and for fast neutron multigroup constants adapted on CYBER 825 computer. It uses indifferently as basic input with the evaluated nuclear data contained in the ENDF/B (US), KEDAK (Germany) and UK (United Kingdom) libraries. The code includes a section devoted to the generation of resonant Doppler broadened cross section in the framework of single-or multi-level Breit-Wigner formalism. The program can compute the thermal neutron scattering law S (α, β, T) as the input data in tabular, free gas or diffusion motion form. It can treat up to 200 energy groups and Legendre moments up to P 5 . The output consists of various reaction multigroup constants in all neutron energy range desired in the nuclear reactor design and calculation. Three options in input file can be used by the user. The output format is arbitrary and defined by user with a minimum of program modification. The program includes about 15,000 cards and 184 subroutines. FORTRAN 5 computer language is used. The operation system is under NOS 2 on computer CYBER 825
The Multigroup Neutron Diffusion Equations/1 Space Dimension
Energy Technology Data Exchange (ETDEWEB)
Linde, Sven
1960-06-15
A description is given of a program for the Ferranti Mercury computer which solves the one-dimensional multigroup diffusion equations in plane, cylindrical or spherical geometry, and also approximates automatically a two-dimensional solution by separating the space variables. In section A the method of calculation is outlined and the preparation of data for two group problems is described. The spatial separation of two-dimensional equations is considered in section B. Section C covers the multigroup equations. These parts are self contained and include all information required for the use of the program. Details of the numerical methods are given in section D. Three sample problems are solved in section E. Punching and operating instructions are given in an appendix.
The Multigroup Neutron Diffusion Equations/1 Space Dimension
International Nuclear Information System (INIS)
Linde, Sven
1960-06-01
A description is given of a program for the Ferranti Mercury computer which solves the one-dimensional multigroup diffusion equations in plane, cylindrical or spherical geometry, and also approximates automatically a two-dimensional solution by separating the space variables. In section A the method of calculation is outlined and the preparation of data for two group problems is described. The spatial separation of two-dimensional equations is considered in section B. Section C covers the multigroup equations. These parts are self contained and include all information required for the use of the program. Details of the numerical methods are given in section D. Three sample problems are solved in section E. Punching and operating instructions are given in an appendix
International Nuclear Information System (INIS)
Ozgener, B.
1998-01-01
A boundary integral equation (BIE) is developed for the application of the boundary element method to the multigroup neutron diffusion equations. The developed BIE contains no explicit scattering term; the scattering effects are taken into account by redefining the unknowns. Boundary elements of the linear and constant variety are utilised for validation of the developed boundary integral formulation
On efficiently computing multigroup multi-layer neutron reflection and transmission conditions
International Nuclear Information System (INIS)
Abreu, Marcos P. de
2007-01-01
In this article, we present an algorithm for efficient computation of multigroup discrete ordinates neutron reflection and transmission conditions, which replace a multi-layered boundary region in neutron multiplication eigenvalue computations with no spatial truncation error. In contrast to the independent layer-by-layer algorithm considered thus far in our computations, the algorithm here is based on an inductive approach developed by the present author for deriving neutron reflection and transmission conditions for a nonactive boundary region with an arbitrary number of arbitrarily thick layers. With this new algorithm, we were able to increase significantly the computational efficiency of our spectral diamond-spectral Green's function method for solving multigroup neutron multiplication eigenvalue problems with multi-layered boundary regions. We provide comparative results for a two-group reactor core model to illustrate the increased efficiency of our spectral method, and we conclude this article with a number of general remarks. (author)
AMPX: a modular code system for generating coupled multigroup neutron-gamma libraries from ENDF/B
Energy Technology Data Exchange (ETDEWEB)
Greene, N.M.; Lucius, J.L.; Petrie, L.M.; Ford, W.E. III; White, J.E.; Wright, R.Q.
1976-03-01
AMPX is a modular system for producing coupled multigroup neutron-gamma cross section sets. Basic neutron and gamma cross-section data for AMPX are obtained from ENDF/B libraries. Most commonly used operations required to generate and collapse multigroup cross-section sets are provided in the system. AMPX is flexibly dimensioned; neutron group structures, and gamma group structures, and expansion orders to represent anisotropic processes are all arbitrary and limited only by available computer core and budget. The basic processes provided will (1) generate multigroup neutron cross sections; (2) generate multigroup gamma cross sections; (3) generate gamma yields for gamma-producing neutron interactions; (4) combine neutron cross sections, gamma cross sections, and gamma yields into final ''coupled sets''; (5) perform one-dimensional discrete ordinates transport or diffusion theory calculations for neutrons and gammas and, on option, collapse the cross sections to a broad-group structure, using the one-dimensional results as weighting functions; (6) plot cross sections, on option, to facilitate the ''evaluation'' of a particular multigroup set of data; (7) update and maintain multigroup cross section libraries in such a manner as to make it not only easy to combine new data with previously processed data but also to do it in a single pass on the computer; and (8) output multigroup cross sections in convenient formats for other codes. (auth)
APPLE, Plot of 1-D Multigroup Neutron Flux and Gamma Flux and Reaction Rates from ANISN
International Nuclear Information System (INIS)
Kawasaki, Hiromitsu; Seki, Yasushi
1983-01-01
A - Description of problem or function: The APPLE-2 code has the following functions: (1) It plots multi-group energy spectra of neutron and/or gamma ray fluxes calculated by ANISN, DOT-3.5, and MORSE. (2) It gives an overview plot of multi-group neutron fluxes calculated by ANISN and DOT-3.5. The scalar neutron flux phi(r,E) is plotted with the spatial parameter r linear along the Y-axis, logE along the X-axis and log phi(r,E) in the Z direction. (3) It calculates the spatial distribution and region volume integrated values of reaction rates using the scalar flux calculated with ANISN and DOT-3.5. (4) Reaction rate distribution along the R or Z direction may be plotted. (5) An overview plot of reaction rates or scalar fluxes summed over specified groups may be plotted. R(ri,zi) or phi(ri,zi) is plotted with spatial parameters r and z along the X- and Y-axes in an orthogonal coordinate system. (6) Angular flux calculated by ANISN is rearranged and a shell source at any specified spatial mesh point may be punched out in FIDO format. The shell source obtained may be employed in solving deep penetration problems with ANISN, when the entire reactor system is divided into two or more parts and the neutron fluxes in two adjoining parts are connected by using the shell source. B - Method of solution: (a) The input data specification is made as simple as possible by making use of the input data required in the radiation transport code. For example, geometry related data in ANISN and DOT are transmitted to APPLE-2 along with scalar flux data so as to reduce duplicity and errors in reproducing these data. (b) Most the input data follow the free form FIDO format developed at Oak Ridge National Laboratory and used in the ANISN code. Furthermore, the mixture specifying method used in ANISN is also employed by APPLE-2. (c) Libraries for some standard response functions required in fusion reactor design have been prepared and are made available to users of the 42-group neutron
International Nuclear Information System (INIS)
Alsmiller, R.G. Jr.; Barnes, J.M.; Drischler, J.D.
1986-01-01
For a variety of applications, e.g., accelerator shielding design, neutrons in radiotherapy, radiation damage studies, etc., it is necessary to carry out transport calculations involving medium-energy (greater than or equal to20 MeV) neutrons. A previous paper described neutron-photon multigroup cross sections in the ANISN format for neutrons from thermal to 400 MeV. In the present paper the cross-section data presented previously have been revised to make them agree with available experimental data. 7 refs., 1 fig
PHISICS multi-group transport neutronic capabilities for RELAP5
Energy Technology Data Exchange (ETDEWEB)
Epiney, A.; Rabiti, C.; Alfonsi, A.; Wang, Y.; Cogliati, J.; Strydom, G. [Idaho National Laboratory (INL), 2525 N. Fremont Ave., Idaho Falls, ID 83402 (United States)
2012-07-01
PHISICS is a neutronic code system currently under development at INL. Its goal is to provide state of the art simulation capability to reactor designers. This paper reports on the effort of coupling this package to the thermal hydraulic system code RELAP5. This will enable full prismatic core and system modeling and the possibility to model coupled (thermal-hydraulics and neutronics) problems with more options for 3D neutron kinetics, compared to the existing diffusion theory neutron kinetics module in RELAP5 (NESTLE). The paper describes the capabilities of the coupling and illustrates them with a set of sample problems. (authors)
Multi-group transport methods for high-resolution neutron activation analysis
International Nuclear Information System (INIS)
Burns, K. A.; Smith, L. E.; Gesh, C. J.; Shaver, M. W.
2009-01-01
The accurate and efficient simulation of coupled neutron-photon problems is necessary for several important radiation detection applications. Examples include the detection of nuclear threats concealed in cargo containers and prompt gamma neutron activation analysis for nondestructive determination of elemental composition of unknown samples. In these applications, high-resolution gamma-ray spectrometers are used to preserve as much information as possible about the emitted photon flux, which consists of both continuum and characteristic gamma rays with discrete energies. Monte Carlo transport is the most commonly used modeling tool for this type of problem, but computational times for many problems can be prohibitive. This work explores the use of multi-group deterministic methods for the simulation of neutron activation problems. Central to this work is the development of a method for generating multi-group neutron-photon cross-sections in a way that separates the discrete and continuum photon emissions so that the key signatures in neutron activation analysis (i.e., the characteristic line energies) are preserved. The mechanics of the cross-section preparation method are described and contrasted with standard neutron-gamma cross-section sets. These custom cross-sections are then applied to several benchmark problems. Multi-group results for neutron and photon flux are compared to MCNP results. Finally, calculated responses of high-resolution spectrometers are compared. Preliminary findings show promising results when compared to MCNP. A detailed discussion of the potential benefits and shortcomings of the multi-group-based approach, in terms of accuracy, and computational efficiency, is provided. (authors)
Discrete formulation for two-dimensional multigroup neutron diffusion equations
Energy Technology Data Exchange (ETDEWEB)
Vosoughi, Naser E-mail: vosoughi@mehr.sharif.edu; Salehi, Ali A.; Shahriari, Majid
2003-02-01
The objective of this paper is to introduce a new numerical method for neutronic calculation in a reactor core. This method can produce the final finite form of the neutron diffusion equation by classifying the neutronic variables and using two kinds of cell complexes without starting from the conventional differential form of the neutron diffusion equation. The method with linear interpolation produces the same convergence as the linear continuous finite element method. The quadratic interpolation is proven; the convergence order depends on the shape of the dual cell. The maximum convergence order is achieved by choosing the dual cell based on two Gauss' points. The accuracy of the method was examined with a well-known IAEA two-dimensional benchmark problem. The numerical results demonstrate the effectiveness of the new method.
Discrete formulation for two-dimensional multigroup neutron diffusion equations
International Nuclear Information System (INIS)
Vosoughi, Naser; Salehi, Ali A.; Shahriari, Majid
2003-01-01
The objective of this paper is to introduce a new numerical method for neutronic calculation in a reactor core. This method can produce the final finite form of the neutron diffusion equation by classifying the neutronic variables and using two kinds of cell complexes without starting from the conventional differential form of the neutron diffusion equation. The method with linear interpolation produces the same convergence as the linear continuous finite element method. The quadratic interpolation is proven; the convergence order depends on the shape of the dual cell. The maximum convergence order is achieved by choosing the dual cell based on two Gauss' points. The accuracy of the method was examined with a well-known IAEA two-dimensional benchmark problem. The numerical results demonstrate the effectiveness of the new method
International Nuclear Information System (INIS)
Kodeli, I.; Aldama, D. L.; De Leege, P. F. A.; Legrady, D.; Hoogenboom, J. E.; Cowan, P.
2004-01-01
As part of the IRTMBA (Improved Radiation Transport Modelling for Borehole Applications) project of the EU community's 5. framework program a special purpose multigroup cross-section library was prepared for use in deterministic and Monte Carlo oil well logging particle transport calculations. This library is expected to improve the prediction of the neutron and gamma spectra at the detector positions of the logging tool, and their use for the interpretation of the neutron logging measurements was studied. Preparation and testing of this library is described. (authors)
International Nuclear Information System (INIS)
Kelsey IV, Charles T.; Prinja, Anil K.
2011-01-01
We evaluate the Monte Carlo calculation efficiency for multigroup transport relative to continuous energy transport using the MCNPX code system to evaluate secondary neutron doses from a proton beam. We consider both fully forward simulation and application of a midway forward adjoint coupling method to the problem. Previously we developed tools for building coupled multigroup proton/neutron cross section libraries and showed consistent results for continuous energy and multigroup proton/neutron transport calculations. We observed that forward multigroup transport could be more efficient than continuous energy. Here we quantify solution efficiency differences for a secondary radiation dose problem characteristic of proton beam therapy problems. We begin by comparing figures of merit for forward multigroup and continuous energy MCNPX transport and find that multigroup is 30 times more efficient. Next we evaluate efficiency gains for coupling out-of-beam adjoint solutions with forward in-beam solutions. We use a variation of a midway forward-adjoint coupling method developed by others for neutral particle transport. Our implementation makes use of the surface source feature in MCNPX and we use spherical harmonic expansions for coupling in angle rather than solid angle binning. The adjoint out-of-beam transport for organs of concern in a phantom or patient can be coupled with numerous forward, continuous energy or multigroup, in-beam perturbations of a therapy beam line configuration. Out-of-beam dose solutions are provided without repeating out-of-beam transport. (author)
Solution for the multigroup neutron space kinetics equations by the modified Picard algorithm
Energy Technology Data Exchange (ETDEWEB)
Tavares, Matheus G.; Petersen, Claudio Z., E-mail: matheus.gulartetavares@gmail.com [Universidade Federal de Pelotas (UFPEL), Capao do Leao, RS (Brazil). Departamento de Matematica e Estatistica; Schramm, Marcelo, E-mail: schrammmarcelo@gmail.com [Universidade Federal de Pelotas (UFPEL), RS (Brazil). Centro de Engenharias; Zanette, Rodrigo, E-mail: rodrigozanette@hotmail.com [Universidade Federal do Rio Grande do Sul (UFRGS), Porto Alegre, RS (Brazil). Instituto de Matematica e Estatistica
2017-07-01
In this work, we used a modified Picards method to solve the Multigroup Neutron Space Kinetics Equations (MNSKE) in Cartesian geometry. The method consists in assuming an initial guess for the neutron flux and using it to calculate a fictitious source term in the MNSKE. A new source term is calculated applying its solution, and so on, iteratively, until a stop criterion is satisfied. For the solution of the fast and thermal neutron fluxes equations, the Laplace Transform technique is used in time variable resulting in a rst order linear differential matrix equation, which are solved by classical methods in the literature. After each iteration, the scalar neutron flux and the delayed neutron precursors are reconstructed by polynomial interpolation. We obtain the fluxes and precursors through Numerical Inverse Laplace Transform using the Stehfest method. We present numerical simulations and comparisons with available results in literature. (author)
Solution for the multigroup neutron space kinetics equations by the modified Picard algorithm
International Nuclear Information System (INIS)
Tavares, Matheus G.; Petersen, Claudio Z.; Schramm, Marcelo; Zanette, Rodrigo
2017-01-01
In this work, we used a modified Picards method to solve the Multigroup Neutron Space Kinetics Equations (MNSKE) in Cartesian geometry. The method consists in assuming an initial guess for the neutron flux and using it to calculate a fictitious source term in the MNSKE. A new source term is calculated applying its solution, and so on, iteratively, until a stop criterion is satisfied. For the solution of the fast and thermal neutron fluxes equations, the Laplace Transform technique is used in time variable resulting in a rst order linear differential matrix equation, which are solved by classical methods in the literature. After each iteration, the scalar neutron flux and the delayed neutron precursors are reconstructed by polynomial interpolation. We obtain the fluxes and precursors through Numerical Inverse Laplace Transform using the Stehfest method. We present numerical simulations and comparisons with available results in literature. (author)
Different spectra with the same neutron source
International Nuclear Information System (INIS)
Vega C, H. R.; Ortiz R, J. M.; Hernandez D, V. M.; Martinez B, M. R.; Hernandez A, B.; Ortiz H, A. A.; Mercado, G. A.
2010-01-01
Using as source term the spectrum of a 239 Pu-Be source several neutron spectra have been calculated using Monte Carlo methods. The source term was located in the centre of spherical moderators made of light water, heavy water and polyethylene of different diameters. Also a 239 Pu-Be source was used to measure its neutron spectrum, bare and moderated by water. The neutron spectra were measured at 100 cm with a Bonner spheres spectrometer. Monte Carlo calculations were used to calculate the neutron spectra of bare and water-moderated spectra that were compared with those measured with the spectrometer. Resulting spectra are similar to those found in power plants with PWR, BWR and Candu nuclear reactors. Beside the spectra the dosimetric features were determined. Using moderators and a single neutron source can be produced neutron spectra alike those found in workplaces, this neutron fields can be utilized to calibrate neutron dosimeters and area monitors. (Author)
Calculations of neutron spectra after neutron-neutron scattering
Energy Technology Data Exchange (ETDEWEB)
Crawford, B E [Gettysburg College, Box 405, Gettysburg, PA 17325 (United States); Stephenson, S L [Gettysburg College, Box 405, Gettysburg, PA 17325 (United States); Howell, C R [Duke University and Triangle Universities Nuclear Laboratory, Durham, NC 27708-0308 (United States); Mitchell, G E [North Carolina State University, Raleigh, NC 27695-8202 (United States); Tornow, W [Duke University and Triangle Universities Nuclear Laboratory, Durham, NC 27708-0308 (United States); Furman, W I [Joint Institute for Nuclear Research, 141980 Dubna (Russian Federation); Lychagin, E V [Joint Institute for Nuclear Research, 141980 Dubna (Russian Federation); Muzichka, A Yu [Joint Institute for Nuclear Research, 141980 Dubna (Russian Federation); Nekhaev, G V [Joint Institute for Nuclear Research, 141980 Dubna (Russian Federation); Strelkov, A V [Joint Institute for Nuclear Research, 141980 Dubna (Russian Federation); Sharapov, E I [Joint Institute for Nuclear Research, 141980 Dubna (Russian Federation); Shvetsov, V N [Joint Institute for Nuclear Research, 141980 Dubna (Russian Federation)
2004-09-01
A direct neutron-neutron scattering length, a{sub nn}, measurement with the goal of 3% accuracy (0.5 fm) is under preparation at the aperiodic pulsed reactor YAGUAR. A direct measurement of a{sub nn} will not only help resolve conflicting results of a{sub nn} by indirect means, but also in comparison to the proton-proton scattering length, a{sub pp}, shed light on the charge-symmetry of the nuclear force. We discuss in detail the analysis of the nn-scattering data in terms of a simple analytical expression. We also discuss calibration measurements using the time-of-flight spectra of neutrons scattered on He and Ar gases and the neutron activation technique. In particular, we calculate the neutron velocity and time-of-flight spectra after scattering neutrons on neutrons and after scattering neutrons on He and Ar atoms for the proposed experimental geometry, using a realistic neutron flux spectrum-Maxwellian plus epithermal tail. The shape of the neutron spectrum after scattering is appreciably different from the initial spectrum, due to collisions between thermal-thermal and thermal-epithermal neutrons. At the same time, the integral over the Maxwellian part of the realistic scattering spectrum differs by only about 6 per cent from that of a pure Maxwellian nn-scattering spectrum.
A multi-group neutron noise simulator for fast reactors
International Nuclear Information System (INIS)
Tran, Hoai Nam; Zylbersztejn, Florian; Demazière, Christophe; Jammes, Christian; Filliatre, Philippe
2013-01-01
Highlights: • The development of a neutron noise simulator for fast reactors. • The noise equation is solved fully in a frequency-domain. • A good agreement with ERANOS on the static calculations. • Noise calculations induced by a localized perturbation of absorption cross section. - Abstract: A neutron noise simulator has been developed for fast reactors based on diffusion theory with multi-energy groups and several groups of delayed neutron precursors. The tool is expected to be applicable for core monitoring of fast reactors and also for other reactor types with hexagonal fuel assemblies. The noise sources are modeled through small stationary fluctuations of macroscopic cross sections, and the induced first order noise is solved fully in the frequency domain. Numerical algorithms are implemented for solving both the static and noise equations using finite differences for spatial discretization, where a hexagonal assembly is radially divided into finer triangular meshes. A coarse mesh finite difference (CMFD) acceleration has been used for accelerating the convergence of both the static and noise calculations. Numerical calculations have been performed for the ESFR core with 33 energy groups and 8 groups of delayed neutron precursors using the cross section data generated by the ERANOS code. The results of the static state have been compared with those obtained using ERANOS. The results show an adequate agreement between the two calculations. Noise calculations for the ESFR core have also been performed and demonstrated with an assumption of the perturbation of the absorption cross section located at the central fuel ring
International Nuclear Information System (INIS)
Honeck, H.C.
1984-01-01
1 - Description of problem or function: HAMMER performs infinite lattice, one-dimensional cell multigroup calculations, followed (optionally) by one-dimensional, few-group, multi-region reactor calculations with neutron balance edits. 2 - Method of solution: Infinite lattice parameters are calculated by means of multigroup transport theory, composite reactor parameters by few-group diffusion theory. 3 - Restrictions on the complexity of the problem: - Cell calculations - maxima of: 30 thermal groups; 54 epithermal groups; 20 space points; 20 regions; 18 isotopes; 10 mixtures; 3 thermal up-scattering mixtures; 200 resonances per group; no overlap or interference; single level only. - Reactor calculations - maxima of : 40 regions; 40 mixtures; 250 space points; 4 groups
International Nuclear Information System (INIS)
Kim, Kyung-O; Jeong, Hae Sun; Jo, Daeseong
2017-01-01
Highlights: • Employing the Radial Point Interpolation Method (RPIM) in numerical analysis of multi-group neutron-diffusion equation. • Establishing mathematical formation of modified multi-group neutron-diffusion equation by RPIM. • Performing the numerical analysis for 2D critical problem. - Abstract: A mesh-free method is introduced to overcome the drawbacks (e.g., mesh generation and connectivity definition between the meshes) of mesh-based (nodal) methods such as the finite-element method and finite-difference method. In particular, the Point Interpolation Method (PIM) using a radial basis function is employed in the numerical analysis for the multi-group neutron-diffusion equation. The benchmark calculations are performed for the 2D homogeneous and heterogeneous problems, and the Multiquadrics (MQ) and Gaussian (EXP) functions are employed to analyze the effect of the radial basis function on the numerical solution. Additionally, the effect of the dimensionless shape parameter in those functions on the calculation accuracy is evaluated. According to the results, the radial PIM (RPIM) can provide a highly accurate solution for the multiplication eigenvalue and the neutron flux distribution, and the numerical solution with the MQ radial basis function exhibits the stable accuracy with respect to the reference solutions compared with the other solution. The dimensionless shape parameter directly affects the calculation accuracy and computing time. Values between 1.87 and 3.0 for the benchmark problems considered in this study lead to the most accurate solution. The difference between the analytical and numerical results for the neutron flux is significantly increased in the edge of the problem geometry, even though the maximum difference is lower than 4%. This phenomenon seems to arise from the derivative boundary condition at (x,0) and (0,y) positions, and it may be necessary to introduce additional strategy (e.g., the method using fictitious points and
International Nuclear Information System (INIS)
Alsmiller, R.G. Jr.; Barnes, J.M.; Drischler, J.D.
1986-02-01
Multigroup cross sections (66 neutron groups and 22 photon groups) are described for neutron energies from thermal to 400 MeV. The elements considered are hydrogen, 10 B, 11 B, carbon, nitrogen, oxygen, sodium, magnesium, aluminum, silicon, sulfur, potassium, calcium, chromium, iron, nickel, tungsten, and lead. The cross section data presented are a revision of similar data presented previously. In the case of iron, transport calculations using the earlier and the revised cross sections are presented and compared, and significant differences are found. The revised cross sections are available from the Radiation Shielding information Center of the Oak Ridge National Laboratory. 32 refs., 5 figs., 3 tabs
Energy Technology Data Exchange (ETDEWEB)
Zanette, Rodrigo; Petersen, Caudio Zen [Univ. Federal de Pelotas, Capao do Leao (Brazil). Programa de Pos Graduacao em Modelagem Matematica; Schramm, Marcello [Univ. Federal de Pelotas (Brazil). Centro de Engenharias; Zabadal, Jorge Rodolfo [Univ. Federal do Rio Grande do Sul, Tramandai (Brazil)
2017-05-15
In this paper a solution for the one-dimensional steady state Multilayer Multigroup Neutron Diffusion Equation in cartesian geometry by Fictitious Borders Power Method and a perturbative analysis of this solution is presented. For each new iteration of the power method, the neutron flux is reconstructed by polynomial interpolation, so that it always remains in a standard form. However when the domain is long, an almost singular matrix arises in the interpolation process. To eliminate this singularity the domain segmented in R regions, called fictitious regions. The last step is to solve the neutron diffusion equation for each fictitious region in analytical form locally. The results are compared with results present in the literature. In order to analyze the sensitivity of the solution, a perturbation in the nuclear parameters is inserted to determine how a perturbation interferes in numerical results of the solution.
International Nuclear Information System (INIS)
Moraes, Pedro Gabriel B.; Leite, Michel C.A.; Barros, Ricardo C.
2013-01-01
In this work we developed a software to model and generate results in tables and graphs of one-dimensional neutron transport problems in multi-group formulation of energy. The numerical method we use to solve the problem of neutron diffusion is analytic, thus eliminating the truncation errors that appear in classical numerical methods, e.g., the method of finite differences. This numerical analytical method increases the computational efficiency, since they are not refined spatial discretization necessary because for any spatial discretization grids used, the numerical result generated for the same point of the domain remains unchanged unless the rounding errors of computational finite arithmetic. We chose to develop a computational application in MatLab platform for numerical computation and program interface is simple and easy with knobs. We consider important to model this neutron transport problem with a fixed source in the context of shielding calculations of radiation that protects the biosphere, and could be sensitive to ionizing radiation
International Nuclear Information System (INIS)
Smith, L.A.; Gallmeier, F.X.; Gehin, J.C.
1995-05-01
The FOEHN critical experiment was analyzed to validate the use of multigroup cross sections and Oak Ridge National Laboratory neutronics computer codes in the design of the Advanced Neutron Source. The ANSL-V 99-group master cross section library was used for all the calculations. Three different critical configurations were evaluated using the multigroup KENO Monte Carlo transport code, the multigroup DORT discrete ordinates transport code, and the multigroup diffusion theory code VENTURE. The simple configuration consists of only the fuel and control elements with the heavy water reflector. The intermediate configuration includes boron endplates at the upper and lower edges of the fuel element. The complex configuration includes both the boron endplates and components in the reflector. Cross sections were processed using modules from the AMPX system. Both 99-group and 20-group cross sections were created and used in two-dimensional models of the FOEHN experiment. KENO calculations were performed using both 99-group and 20-group cross sections. The DORT and VENTURE calculations were performed using 20-group cross sections. Because the simple and intermediate configurations are azimuthally symmetric, these configurations can be explicitly modeled in R-Z geometry. Since the reflector components cannot be modeled explicitly using the current versions of these codes, three reflector component homogenization schemes were developed and evaluated for the complex configuration. Power density distributions were calculated with KENO using 99-group cross sections and with DORT and VENTURE using 20-group cross sections. The average differences between the measured values and the values calculated with the different computer codes range from 2.45 to 5.74%. The maximum differences between the measured and calculated thermal flux values for the simple and intermediate configurations are ∼ 13%, while the average differences are < 8%
Analysis of coupled neutron-gamma radiations, applied to shieldings in multigroup albedo method
International Nuclear Information System (INIS)
Dunley, Leonardo Souza
2002-01-01
The principal mathematical tools frequently available for calculations in Nuclear Engineering, including coupled neutron-gamma radiations shielding problems, involve the full Transport Theory or the Monte Carlo techniques. The Multigroup Albedo Method applied to shieldings is characterized by following the radiations through distinct layers of materials, allowing the determination of the neutron and gamma fractions reflected from, transmitted through and absorbed in the irradiated media when a neutronic stream hits the first layer of material, independently of flux calculations. Then, the method is a complementary tool of great didactic value due to its clarity and simplicity in solving neutron and/or gamma shielding problems. The outstanding results achieved in previous works motivated the elaboration and the development of this study that is presented in this dissertation. The radiation balance resulting from the incidence of a neutronic stream into a shielding composed by 'm' non-multiplying slab layers for neutrons was determined by the Albedo method, considering 'n' energy groups for neutrons and 'g' energy groups for gammas. It was taken into account there is no upscattering of neutrons and gammas. However, it was considered that neutrons from any energy groups are able to produce gammas of all energy groups. The ANISN code, for an angular quadrature order S 2 , was used as a standard for comparison of the results obtained by the Albedo method. So, it was necessary to choose an identical system configuration, both for ANISN and Albedo methods. This configuration was six neutron energy groups and eight gamma energy groups, using three slab layers (iron aluminum - manganese). The excellent results expressed in comparative tables show great agreement between the values determined by the deterministic code adopted as standard and, the values determined by the computational program created using the Albedo method and the algorithm developed for coupled neutron
Neutron spectra produced by moderating an isotopic neutron source
International Nuclear Information System (INIS)
Carrillo Nunnez, Aureliano; Vega Carrillo, Hector Rene
2001-01-01
A Monte Carlo study has been carried out to determine the neutron spectra produced by an isotopic neutron source inserted in moderating media. Most devices used for radiation protection have a response strongly dependent on neutron energy. ISO recommends several neutron sources and monoenergetic neutron radiations, but actual working situations have broad spectral neutron distributions extending from thermal to MeV energies, for instance, near nuclear power plants, medical applications accelerators and cosmic neutrons. To improve the evaluation of the dosimetric quantities, is recommended to calibrate the radiation protection devices in neutron spectra which are nearly like those met in practice. In order to complete the range of neutron calibrating sources, it seems useful to develop several wide spectral distributions representative of typical spectra down to thermal energies. The aim of this investigation was to use an isotopic neutron source in different moderating media to reproduce some of the neutron fields found in practice. MCNP code has been used during calculations, in these a 239PuBe neutron source was inserted in H2O, D2O and polyethylene moderators. Moderators were modeled as spheres and cylinders of different sizes. In the case of cylindrical geometry the anisotropy of resulting neutron spectra was calculated from 0 to 2 . From neutron spectra dosimetric features were calculated. MCNP calculations were validated by measuring the neutron spectra of a 239PuBe neutron source inserted in a H2O cylindrical moderator. The measurements were carried out with a multisphere neutron spectrometer with a 6LiI(Eu) scintillator. From the measurements the neutron spectrum was unfolded using the BUNKIUT code and the UTA4 response matrix. Some of the moderators with the source produce a neutron spectrum close to spectra found in actual applications, then can be used during the calibration of radiation protection devices
Neutron and photon spectra in LINACs
International Nuclear Information System (INIS)
Vega-Carrillo, H.R.; Martínez-Ovalle, S.A.; Lallena, A.M.; Mercado, G.A.; Benites-Rengifo, J.L.
2012-01-01
A Monte Carlo calculation, using the MCNPX code, was carried out in order to estimate the photon and neutron spectra in two locations of two linacs operating at 15 and 18 MV. Detailed models of both linac heads were used in the calculations. Spectra were estimated below the flattening filter and at the isocenter. Neutron spectra show two components due to evaporation and knock-on neutrons. Lethargy spectra under the filter were compared to the spectra calculated from the function quoted by Tosi et al. that describes reasonably well neutron spectra beyond 1 MeV, though tends to underestimate the energy region between 10 –6 and 1 MeV. Neutron and the Bremsstrahlung spectra show the same features regardless of the linac voltage. - Highlights: ► With MCNPX code realistic models of two LINACs were built. ► Photon and neutron spectra below the flattening filter and at the isocenter were calculated. ► Neutron spectrum at the flattening filter was compared against the Tosi et al. source-term model. ► Tosi et al. model underestimates the neutron contribution below 1 MeV. ► Photon spectra look alike to those published in literature.
International Nuclear Information System (INIS)
Schriewer, J.; Hehn, G.; Mattes, M.; Pfister, G.; Keinert, J.
1978-01-01
Calculations were made for different benchmark experiments in order to test the coupled multigroup neutron and gamma library EURLIB-3 with 100 neutron groups and 20 gamma groups. In cooperation with EURATOM, Ispra, we produced this shielding library recently from ENDF/B-IV data for application in fission and fusion technology. Integral checks were performed for natural lithium, carbon, oxygen, and iron. Since iron is the most important structural material in nuclear technology, we started with calculations of iron benchmark experiments. Most of them are integral experiments of INR, Karlsruhe, but comparisons were also done with benchmark experiments from USA and Japan. For the experiments with fission sources we got satisfying results. All details of the resonances cannot be checked with flux measurements and multigroup cross sections used. But some averaged resonance behaviour of the measured and calculated fluxes can be compared and checked within the error limits given. We get greater differences in the calculations of benchmark experiments with 14 MeV neutron sources. For iron the group cross sections of EURLIB-3 produce an underestimation of the neutron flux in a broad energy region below the source energy. The conclusion is that the energy degradation by inelastic scattering is too strong. For fusion application the anisotropy of the inelastic scatter process must be taken into account, which isn't done by the processing codes at present. If this effect isn't enough, additional corrections have to be applied to the inelastic cross sections of iron in ENDF/B-IV. (author)
International Nuclear Information System (INIS)
Si, S.
2012-01-01
The Universal Algorithm of Stiffness Confinement Method (UASCM) for neutron kinetics model of multi-dimensional and multi-group transport equations or diffusion equations has been developed. The numerical experiments based on transport theory code MGSNM and diffusion theory code MGNEM have demonstrated that the algorithm has sufficient accuracy and stability. (authors)
International Nuclear Information System (INIS)
Modak, R.S.; Sahni, D.C.
1996-01-01
Some simple reciprocity-like relations that exist in multi-group neutron diffusion and transport theory over bare homogeneous regions are presented. These relations do not involve the adjoint solutions and are directly related to numerical schemes based on an explicit evaluation of the fission matrix. (author)
Energy Technology Data Exchange (ETDEWEB)
Lillie, R.A.; Robinson, J.C.
1976-05-01
The discrete ordinates method is the most powerful and generally used deterministic method to obtain approximate solutions of the Boltzmann transport equation. A finite element formulation, utilizing a canonical form of the transport equation, is here developed to obtain both integral and pointwise solutions to neutron transport problems. The formulation is based on the use of linear triangles. A general treatment of anisotropic scattering is included by employing discrete ordinates-like approximations. In addition, multigroup source outer iteration techniques are employed to perform group-dependent calculations. The ability of the formulation to reduce substantially ray effects and its ability to perform streaming calculations are demonstrated by analyzing a series of test problems. The anisotropic scattering and multigroup treatments used in the development of the formulation are verified by a number of one-dimensional comparisons. These comparisons also demonstrate the relative accuracy of the formulation in predicting integral parameters. The applicability of the formulation to nonorthogonal planar geometries is demonstrated by analyzing a hexagonal-type lattice. A small, high-leakage reactor model is analyzed to investigate the effects of varying both the spatial mesh and order of angular quadrature. This analysis reveals that these effects are more pronounced in the present formulation than in other conventional formulations. However, the insignificance of these effects is demonstrated by analyzing a realistic reactor configuration. In addition, this final analysis illustrates the importance of incorporating anisotropic scattering into the finite element formulation. 8 tables, 29 figures.
International Nuclear Information System (INIS)
Lillie, R.A.; Robinson, J.C.
1976-05-01
The discrete ordinates method is the most powerful and generally used deterministic method to obtain approximate solutions of the Boltzmann transport equation. A finite element formulation, utilizing a canonical form of the transport equation, is here developed to obtain both integral and pointwise solutions to neutron transport problems. The formulation is based on the use of linear triangles. A general treatment of anisotropic scattering is included by employing discrete ordinates-like approximations. In addition, multigroup source outer iteration techniques are employed to perform group-dependent calculations. The ability of the formulation to reduce substantially ray effects and its ability to perform streaming calculations are demonstrated by analyzing a series of test problems. The anisotropic scattering and multigroup treatments used in the development of the formulation are verified by a number of one-dimensional comparisons. These comparisons also demonstrate the relative accuracy of the formulation in predicting integral parameters. The applicability of the formulation to nonorthogonal planar geometries is demonstrated by analyzing a hexagonal-type lattice. A small, high-leakage reactor model is analyzed to investigate the effects of varying both the spatial mesh and order of angular quadrature. This analysis reveals that these effects are more pronounced in the present formulation than in other conventional formulations. However, the insignificance of these effects is demonstrated by analyzing a realistic reactor configuration. In addition, this final analysis illustrates the importance of incorporating anisotropic scattering into the finite element formulation. 8 tables, 29 figures
Reconstruction of neutron spectra through neural networks
International Nuclear Information System (INIS)
Vega C, H.R.; Hernandez D, V.M.; Manzanares A, E.
2003-01-01
A neural network has been used to reconstruct the neutron spectra starting from the counting rates of the detectors of the Bonner sphere spectrophotometric system. A group of 56 neutron spectra was selected to calculate the counting rates that would produce in a Bonner sphere system, with these data and the spectra it was trained the neural network. To prove the performance of the net, 12 spectra were used, 6 were taken of the group used for the training, 3 were obtained of mathematical functions and those other 3 correspond to real spectra. When comparing the original spectra of those reconstructed by the net we find that our net has a poor performance when reconstructing monoenergetic spectra, this attributes it to those characteristic of the spectra used for the training of the neural network, however for the other groups of spectra the results of the net are appropriate with the prospective ones. (Author)
Spectrum of the multigroup neutron transport operator for bounded spatial domains
International Nuclear Information System (INIS)
Larsen, E.W.
1979-01-01
The spectrum of the multigroup neutron transport operator A is studied for bounded spatial regions D which consist of a finite number of material subregions. Our main results provide simple conditions on the material cross sections which guarantee that (1) A possesses eigenvalues in the finite plane; (2) A possesses a ''leading'' eigenvalue lambda 0 which is real, not less than the real part of any other eigenvalue, and to which there corresponds at least one nonnegative eigenfunction psi/sub lambda/0; and (3) A possesses a ''dominant'' eigenvalue lambda 0 which is real, simple, greater than the real part of any other eigenvalue, and whose eigenfunction psi/sub lambda/0 satisfies psi/sub lambda/0> or =0 and ∫psi/sub lambda/0d 2 Ω>0. We give examples to illustrate the results and to show that a leading eigenvalue need not be simple, nor its eigenfunction(s) positive
The solution of the multigroup neutron transport equation using spherical harmonics
International Nuclear Information System (INIS)
Fletcher, K.
1981-01-01
A solution of the multi-group neutron transport equation in up to three space dimensions is presented. The flux is expanded in a series of unnormalised spherical harmonics. Using the various recurrence formulae a linked set of first order differential equations is obtained for the moments psisup(g)sub(lm)(r), γsup(g)sub(lm)(r). Terms with odd l are eliminated resulting in a second order system which is solved by two methods. The first is a finite difference formulation using an iterative procedure, secondly, in XYZ and XY geometry a finite element solution is given. Results for a test problem using both methods are exhibited and compared. (orig./RW) [de
Energy Technology Data Exchange (ETDEWEB)
Zanette, Rodrigo [Universidade Federal do Rio Grande do Sul (UFRGS), Porto Alegre, RS (Brazil). Programa de Pós-Graduação em Matemática Aplicada; Petersen, Claudio Z.; Tavares, Matheus G., E-mail: rodrigozanette@hotmail.com, E-mail: claudiopetersen@yahoo.com.br, E-mail: matheus.gulartetavares@gmail.com [Universidade Federal de Pelotas (UFPEL), RS (Brazil). Programa de Pós-Graduação em Modelagem Matemática
2017-07-01
We describe in this work the application of the modified power method for solve the multigroup neutron diffusion eigenvalue problem in slab geometry considering two-dimensions for nuclear reactor global calculations. It is well known that criticality calculations can often be best approached by solving eigenvalue problems. The criticality in nuclear reactors physics plays a relevant role since establishes the ratio between the numbers of neutrons generated in successive fission reactions. In order to solve the eigenvalue problem, a modified power method is used to obtain the dominant eigenvalue (effective multiplication factor (K{sub eff})) and its corresponding eigenfunction (scalar neutron flux), which is non-negative in every domain, that is, physically relevant. The innovation of this work is solving the neutron diffusion equation in analytical form for each new iteration of the power method. For solve this problem we propose to apply the Finite Fourier Sine Transform on one of the spatial variables obtaining a transformed problem which is resolved by well-established methods for ordinary differential equations. The inverse Fourier transform is used to reconstruct the solution for the original problem. It is known that the power method is an iterative source method in which is updated by the neutron flux expression of previous iteration. Thus, for each new iteration, the neutron flux expression becomes larger and more complex due to analytical solution what makes propose that it be reconstructed through an polynomial interpolation. The methodology is implemented to solve a homogeneous problem and the results are compared with works presents in the literature. (author)
International Nuclear Information System (INIS)
Ford, W.E. III; Arwood, J.W.; Greene, N.M.; Petrie, L.M.; Primm, R.T. III; Waddell, M.W.; Webster, C.C.; Westfall, R.M.; Wright, R.Q.
1987-01-01
Multigroup P3 neutron, P0-P3 secondary gamma ray production (SGRP), and P6 gamma ray interaction (GRI) cross section libraries have been generated to support design work on the Advanced Neutron Source (ANS) reactor. The libraries, designated ANSL-V (Advanced Neutron Source Cross-Section Libraries), are data bases in a format suitable for subsequent generation of problem dependent cross sections. The ANSL-V libraries are available on magnetic tape from the Radiation Shielding Information Center at Oak Ridge National Laboratory
International Nuclear Information System (INIS)
Jones, D.B.
1986-01-01
EPRI-LATTICE is a multigroup neutron transport computer code for the analysis of light water reactor fuel assemblies. It can solve the two-dimensional neutron transport problem by two distinct methods: (a) the method of collision probabilities and (b) the method of discrete ordinates. The code was developed by S. Levy Inc. as an account of work sponsored by the Electric Power Research Institute (EPRI). The collision probabilities calculation in EPRI-LATTICE (L-CP) is based on the same methodology that exists in the lattice codes CPM-2 and EPRI-CPM. Certain extensions have been made to the data representations of the CPM programs to improve the overall accuracy of the calculation. The important extensions include unique representations of scattering matrices and fission fractions (chi) for each composition in the problem. A new capability specifically developed for the EPRI-LATTICE code is a discrete ordinates methodology. The discrete ordinates calculation in EPRI-LATTICE (L-SN) is based on the discrete S/sub n/ methodology that exists in the TWODANT program. In contrast to TWODANT, which utilizes synthetic diffusion acceleration and supports multiple geometries, only the transport equations are solved by L-SN and only the data representations for the two-dimensional geometry are treated
International Nuclear Information System (INIS)
Reed, D.L.; Symons, C.R.
1965-01-01
A method of calculation is given which assists the analyses of chopper measurements of spectra from ZENITH and enables complex multigroup theoretical calculations of the spectra to be put into a form which may be compared with experiment. In addition the theory of the cut-off function has been extended to give analytical expressions which take into account the effects of sub-collimators, off centre slits and of a rotor made of a material partially transparent to neutrons. The theoretical cut-off function suggested shows good agreement with experiment. (author)
Energy Technology Data Exchange (ETDEWEB)
Reed, D L; Symons, C R [General Reactor Physics Division, Atomic Energy Establishment, Winfrith, Dorchester, Dorset (United Kingdom)
1965-01-15
A method of calculation is given which assists the analyses of chopper measurements of spectra from ZENITH and enables complex multigroup theoretical calculations of the spectra to be put into a form which may be compared with experiment. In addition the theory of the cut-off function has been extended to give analytical expressions which take into account the effects of sub-collimators, off centre slits and of a rotor made of a material partially transparent to neutrons. The theoretical cut-off function suggested shows good agreement with experiment. (author)
International Nuclear Information System (INIS)
Petersen, Claudio Zen; Vilhena, Marco T.; Barros, Ricardo C.
2009-01-01
In this paper the application of the Laplace transform method is described in order to determine the energy-dependent albedo matrix that is used in the boundary conditions multigroup neutron diffusion eigenvalue problems in slab geometry for nuclear reactor global calculations. In slab geometry, the diffusion albedo substitutes without approximation the baffle-reflector system around the active domain. Numerical results to typical test problems are shown to illustrate the accuracy and the efficiency of the Chebysheff acceleration scheme. (orig.)
International Nuclear Information System (INIS)
Ilieva, K.; Belousov, S.; Apostolov, T.
1998-01-01
The verification of calculated neutron fluence onto the WWER-440/230 pressure vessel is very topical task in particular referring that some of this type of reactors have been operated the major part of its design lifetime. Since the induced activity from the neutron irradiation onto the elements is a simple response of neutron flux the neutron fluence verification usually is done using the measured activity of radionuclides produced during reactor operation. Calculational and experimental results of 54 Mn induced activity of scraps from inner wall of Unit 1 reactor pressure vessel after 18th cycle and detectors irradiated behind the vessel during the 18th cycle of Unit 1 at Kozloduy NPP as well as neutron flux attenuation through the WWER-440/230 pressure vessel are presented. Neutron cross sections libraries generated on the base of ENDF/B-IV and ENDF/B-VI have been used in the calculations. The comparative analysis of evaluated activities and attenuation coefficient demonstrates the better reliability of the neutron fluence calculations by the libraries based on ENDF/B-VI than by ones on ENDF/B-IV. The extreme rarity of data for the activity of scraps from the WWER-440 reactor vessel and its combination with the data for the detectors irradiated behind the vessel makes them especially attractive for verification of calculational methods of neutron fluence onto the WWER-440 vessel with dummy cassettes loading. (author)
Three-dimensional h-adaptivity for the multigroup neutron diffusion equations
Wang, Yaqi
2009-04-01
Adaptive mesh refinement (AMR) has been shown to allow solving partial differential equations to significantly higher accuracy at reduced numerical cost. This paper presents a state-of-the-art AMR algorithm applied to the multigroup neutron diffusion equation for reactor applications. In order to follow the physics closely, energy group-dependent meshes are employed. We present a novel algorithm for assembling the terms coupling shape functions from different meshes and show how it can be made efficient by deriving all meshes from a common coarse mesh by hierarchic refinement. Our methods are formulated using conforming finite elements of any order, for any number of energy groups. The spatial error distribution is assessed with a generalization of an error estimator originally derived for the Poisson equation. Our implementation of this algorithm is based on the widely used Open Source adaptive finite element library deal.II and is made available as part of this library\\'s extensively documented tutorial. We illustrate our methods with results for 2-D and 3-D reactor simulations using 2 and 7 energy groups, and using conforming finite elements of polynomial degree up to 6. © 2008 Elsevier Ltd. All rights reserved.
MENDF71x. Multigroup Neutron Cross Section Data Tables Based upon ENDF/B-VII.1
International Nuclear Information System (INIS)
Conlin, Jeremy Lloyd; Parsons, Donald Kent; Gardiner, Steven J.; Gray, Mark Girard; Lee, Mary Beth; White, Morgan Curtis
2015-01-01
A new multi-group neutron cross section library has been released along with the release of NDI version 2.0.20. The library is named MENDF71x and is based upon the evaluations released in ENDF/B-VII.1 which was made publicly available in December 2011. ENDF/B-VII.1 consists of 423 evaluations of which ten are excited states evaluations and 413 are ground state evaluations. MENDF71x was created by processing the 423 evaluations into 618-group, downscatter only NDI data tables. The ENDF/B evaluation files were processed using NJOY version 99.393 with the exception of 35 Cl and 233 U. Those two isotopes had unique properties that required that we process the evaluation using NJOY version 2012. The MENDF71x library was only processed to room temperature, i.e., 293.6 K. In the future, we plan on producing a multi-temperature library based on ENDF/B-VII.1 and compatible with MENDF71x.
International Nuclear Information System (INIS)
Seed, T.J.; Miller, W.F. Jr.; Brinkley, F.W. Jr.
1977-03-01
TRIDENT solves the two-dimensional-multigroup-transport equations in rectangular (x-y) and cylindrical (r-z) geometries using a regular triangular mesh. Regular and adjoint, inhomogeneous and homogeneous (k/sub eff/ and eigenvalue searches) problems subject to vacuum, reflective, white, or source boundary conditions are solved. General anisotropic scattering is allowed and anisotropic-distributed sources are permitted. The discrete-ordinates approximation is used for the neutron directional variables. An option is included to append a fictitious source to the discrete-ordinates equations that is defined such that spherical-harmonics solutions (in x-y geometry) or spherical-harmonics-like solutions (in r-z geometry) are obtained. A spatial-finite-element method is used in which the angular flux is expressed as a linear polynomial in each triangle that is discontinous at triangle boundaries. Unusual Features of the program: Provision is made for creation of standard interface output files for S/sub N/ constants, angle-integrated (scalar) fluxes, and angular fluxes. Standard interface input files for S/sub N/ constants, inhomogeneous sources, cross sections, and the scalar flux may be read. Flexible edit options as well as a dump and restart capability are provided
TASK, 1-D Multigroup Diffusion or Transport Theory Reactor Kinetics with Delayed Neutron
International Nuclear Information System (INIS)
Buhl, A.R.; Hermann, O.W.; Hinton, R.J.; Dodds, H.L. Jr.; Robinson, J.C.; Lillie, R.A.
1975-01-01
1 - Description of problem or function: TASK solves the one-dimensional multigroup form of the reactor kinetics equations, using either transport or diffusion theory and allowing an arbitrary number of delayed neutron groups. The program can also be used to solve standard static problems efficiently such as eigenvalue problems, distributed source problems, and boundary source problems. Convergence problems associated with sources in highly multiplicative media are circumvented, and such problems are readily calculable. 2 - Method of solution: TASK employs a combination scattering and transfer matrix method to eliminate certain difficulties that arise in classical finite difference approximations. As such, within-group (inner) iterations are eliminated and solution convergence is independent of spatial mesh size. The time variable is removed by Laplace transformation. (A later version will permit direct time solutions.) The code can be run either in an outer iteration mode or in closed (non-iterative) form. The running mode is dictated by the number of groups times the number of angles, consistent with available storage. 3 - Restrictions on the complexity of the problem: The principal restrictions are available storage and computation time. Since the code is flexibly-dimensioned and has an outer iteration option there are no internal restrictions on group structure, quadrature, and number of ordinates. The flexible-dimensioning scheme allows optional use of core storage. The generalized cylindrical geometry option is not complete in Version I of the code. The feedback options and omega-mode search options are not included in Version I
Measuring neutron spectra in radiotherapy using the nested neutron spectrometer
Energy Technology Data Exchange (ETDEWEB)
Maglieri, Robert, E-mail: robert.maglieri@mail.mcgill.ca; Evans, Michael; Seuntjens, Jan; Kildea, John [Medical Physics Unit, McGill University, Montreal, Quebec H4A 3J1 (Canada); Licea, Angel [Canadian Nuclear Safety Commission, Ottawa, Ontario K1P 5S9 (Canada)
2015-11-15
Purpose: Out-of-field neutron doses resulting from photonuclear interactions in the head of a linear accelerator pose an iatrogenic risk to patients and an occupational risk to personnel during radiotherapy. To quantify neutron production, in-room measurements have traditionally been carried out using Bonner sphere systems (BSS) with activation foils and TLDs. In this work, a recently developed active detector, the nested neutron spectrometer (NNS), was tested in radiotherapy bunkers. Methods: The NNS is designed for easy handling and is more practical than the traditional BSS. Operated in current-mode, the problem of pulse pileup due to high dose-rates is overcome by measuring current, similar to an ionization chamber. In a bunker housing a Varian Clinac 21EX, the performance of the NNS was evaluated in terms of reproducibility, linearity, and dose-rate effects. Using a custom maximum-likelihood expectation–maximization algorithm, measured neutron spectra at various locations inside the bunker were then compared to Monte Carlo simulations of an identical setup. In terms of dose, neutron ambient dose equivalents were calculated from the measured spectra and compared to bubble detector neutron dose equivalent measurements. Results: The NNS-measured spectra for neutrons at various locations in a treatment room were found to be consistent with expectations for both relative shape and absolute magnitude. Neutron fluence-rate decreased with distance from the source and the shape of the spectrum changed from a dominant fast neutron peak near the Linac head to a dominant thermal neutron peak in the moderating conditions of the maze. Monte Carlo data and NNS-measured spectra agreed within 30% at all locations except in the maze where the deviation was a maximum of 40%. Neutron ambient dose equivalents calculated from the authors’ measured spectra were consistent (one standard deviation) with bubble detector measurements in the treatment room. Conclusions: The NNS may
International Nuclear Information System (INIS)
Recktenwald, G.D.; Bronk, L.A.; Deinert, M.R.
2010-01-01
Determining the time dependent concentration of isotopes within a nuclear reactor core is central to the analysis of nuclear fuel cycles. We present a fast, flexible tool for determining the time dependent neutron spectrum within fast reactors. The code (VBUDS: visualization, burnup, depletion and spectra) uses a two region, multigroup collision probability model to simulate the energy dependent neutron flux and tracks the buildup and burnout of 24 actinides, as well as fission products. While originally developed for LWR simulations, the model is shown to produce fast reactor spectra that show high degree of fidelity to available fast reactor benchmarks. (authors)
International Nuclear Information System (INIS)
Nakagawa, Masayuki; Katsuragi, Satoru; Narita, Hideo.
1976-07-01
The multi-group treatment has been used in the design study of fast reactors and analysis of experiments at fast critical assemblies. The accuracy of the multi-group cross sections therefore affects strongly the results of these analyses. The ESELEM 4 code has been developed to produce multi-group cross sections with an advanced method from the nuclear data libraries used in the JAERI Fast set. ESELEM 4 solves integral transport equation by the collision probability method in plate lattice geometry to obtain the fine neutron spectrum. A typical fine group mesh width is 0.008 in lethargy unit. The multi-group cross sections are calculated by weighting the point data with the fine structure neutron flux. Some devices are applied to reduce computation time and computer core storage required for the calculation. The slowing down sources are calculated with the use of a recurrence formula derived for elastic and inelastic scattering. The broad group treatment is adopted above 2 MeV for dealing with both light any heavy elements. Also the resonance cross sections of heavy elements are represented in a broad group structure, for which we use the values of the JAERI Fast set. The library data are prepared by the PRESM code from ENDF/A type nuclear data files. The cross section data can be compactly stored in the fast computer core memory for saving the core storage and data processing time. The programme uses the variable dimensions to increase its flexibility. The users' guide for ESELEM 4 and PRESM is also presented in this report. (auth.)
CARNAC, Neutron Flux and Neutron Spectra in Criticality Accident
International Nuclear Information System (INIS)
Bessis, J.
1976-01-01
Nature of physical problem solved: Calculation of flux and neutron spectra in the case of a criticality accident. The method is unsophisticated but fast. The program is divided into two parts: (1) The code CRITIC is based on the Fermi age equation and evaluates the neutron number per fission emitted from a moderate critical system and its energy spectrum. (2) The code NARCISSE uses concrete current albedo, evaluates the product of neutron reflection on walls of the source containment and calculates the resulting flux at any point, and its energy distribution into 21 groups. The results obtained seem satisfactory, if compared with a Monte Carlo program
International Nuclear Information System (INIS)
Ford, W.E. III; Arwood, J.W.; Greene, N.M.; Moses, D.L.; Petrie, L.M.; Primm, R.T. III; Slater, C.O.; Westfall, R.M.; Wright, R.Q.
1990-09-01
Pseudo-problem-independent, multigroup cross-section libraries were generated to support Advanced Neutron Source (ANS) Reactor design studies. The ANS is a proposed reactor which would be fueled with highly enriched uranium and cooled with heavy water. The libraries, designated ANSL-V (Advanced Neutron Source Cross Section Libraries based on ENDF/B-V), are data bases in AMPX master format for subsequent generation of problem-dependent cross-sections for use with codes such as KENO, ANISN, XSDRNPM, VENTURE, DOT, DORT, TORT, and MORSE. Included in ANSL-V are 99-group and 39-group neutron, 39-neutron-group 44-gamma-ray-group secondary gamma-ray production (SGRP), 44-group gamma-ray interaction (GRI), and coupled, 39-neutron group 44-gamma-ray group (CNG) cross-section libraries. The neutron and SGRP libraries were generated primarily from ENDF/B-V data; the GRI library was generated from DLC-99/HUGO data, which is recognized as the ENDF/B-V photon interaction data. Modules from the AMPX and NJOY systems were used to process the multigroup data. Validity of selected data from the fine- and broad-group neutron libraries was satisfactorily tested in performance parameter calculations
Time-of-flight neutron spectra measurements in Zenith
Energy Technology Data Exchange (ETDEWEB)
Barclay, F R; Coates, M S; Diment, K M; Durrani, S A; Gayther, D B; Poole, M J; Reed, D L
1962-01-15
Neutron spectra in the second core loading of ZENITH have been measured using a neutron chopper. Spectra at two positions in the reactore core were obtained over a range of temperatures extending to 650 deg C.
International Nuclear Information System (INIS)
Vondy, D.R.; Fowler, T.B.; Cunningham, G.W.
1977-11-01
The report documents the computer code block VENTURE designed to solve multigroup neutronics problems with application of the finite-difference diffusion-theory approximation to neutron transport (or alternatively simple P 1 ) in up to three-dimensional geometry. It uses and generates interface data files adopted in the cooperative effort sponsored by the Reactor Physics Branch of the Division of Reactor Research and Development of the Energy Research and Development Administration. Several different data handling procedures have been incorporated to provide considerable flexibility; it is possible to solve a wide variety of problems on a variety of computer configurations relatively efficiently
Energy Technology Data Exchange (ETDEWEB)
Vondy, D.R.; Fowler, T.B.; Cunningham, G.W.
1977-11-01
The report documents the computer code block VENTURE designed to solve multigroup neutronics problems with application of the finite-difference diffusion-theory approximation to neutron transport (or alternatively simple P/sub 1/) in up to three-dimensional geometry. It uses and generates interface data files adopted in the cooperative effort sponsored by the Reactor Physics Branch of the Division of Reactor Research and Development of the Energy Research and Development Administration. Several different data handling procedures have been incorporated to provide considerable flexibility; it is possible to solve a wide variety of problems on a variety of computer configurations relatively efficiently.
International Nuclear Information System (INIS)
Vondy, D.R.; Fowler, T.B.; Cunningham, G.W.
1975-10-01
The computer code block VENTURE, designed to solve multigroup neutronics problems with application of the finite-difference diffusion-theory approximation to neutron transport (or alternatively simple P 1 ) in up to three-dimensional geometry is described. A variety of types of problems may be solved: the usual eigenvalue problem, a direct criticality search on the buckling, on a reciprocal velocity absorber (prompt mode), or on nuclide concentrations, or an indirect criticality search on nuclide concentrations, or on dimensions. First-order perturbation analysis capability is available at the macroscopic cross section level
Microdosimetric spectra measurements of JANUS neutrons
Energy Technology Data Exchange (ETDEWEB)
Marshall, I.R.; Williamson, F.S.
1985-01-01
Neutron radiation from the JANUS reactor at Argonne National Laboratory is being used with increasing frequency for major biological experiments. The fast neutron spectrum has a Kerma-weighted mean energy of 0.8 MeV and low gamma-ray contamination. In 1984 the JANUS fission converter plate of highly enriched uranium was replaced by one made of low-enriched uranium. We recorded microdosimetric spectra at several different positions in the high-flux irradiation room of JANUS before the change of the converter plate. Each set of measurements consisted of spectra taken at three different site diameters (0.5, 1.0, and 5.0 ..mu..m) and in both ''attenuator up'' and ''attenuator down'' configurations. At two conventional dosimetry reference positions, two sets of measurements were recorded. At three biological reference positions, measurements simulating several biological irradiation conditions, were taken. The dose rate at each position was estimated and compared with dose rates obtained previously by conventional dosimetry. Comparison of the different measurements showed no major change in spectra as a function of position or irradiation condition. First results from similar sets of measurements recorded after the installment of the new converter plate indicate no major change in the spectra. 11 refs., 4 figs., 5 tabs.
Microdosimetric spectra measurements of JANUS neutrons
International Nuclear Information System (INIS)
Marshall, I.R.; Williamson, F.S.
1985-01-01
Neutron radiation from the JANUS reactor at Argonne National Laboratory is being used with increasing frequency for major biological experiments. The fast neutron spectrum has a Kerma-weighted mean energy of 0.8 MeV and low gamma-ray contamination. In 1984 the JANUS fission converter plate of highly enriched uranium was replaced by one made of low-enriched uranium. We recorded microdosimetric spectra at several different positions in the high-flux irradiation room of JANUS before the change of the converter plate. Each set of measurements consisted of spectra taken at three different site diameters (0.5, 1.0, and 5.0 μm) and in both ''attenuator up'' and ''attenuator down'' configurations. At two conventional dosimetry reference positions, two sets of measurements were recorded. At three biological reference positions, measurements simulating several biological irradiation conditions, were taken. The dose rate at each position was estimated and compared with dose rates obtained previously by conventional dosimetry. Comparison of the different measurements showed no major change in spectra as a function of position or irradiation condition. First results from similar sets of measurements recorded after the installment of the new converter plate indicate no major change in the spectra. 11 refs., 4 figs., 5 tabs
Compendium on neutron spectra in criticality accident dosimetry
International Nuclear Information System (INIS)
Ing, H.
1978-01-01
Graphical and tabulated neutron spectra are presented: from selected critical assemblies; from critical solutions; of fission neutrons through shielding; of H 2 O-moderated fission neutrons through shielding; of D 2 O-moderated fission neutrons through shielding; of fission neutrons reflected from various materials; from the D(T, 4 He)n reaction (''14 MeV'' neutrons) through shielding and of ''14 MeV'' neutrons reflected from various materials
On the calculation of multi-group fission spectrum vectors
International Nuclear Information System (INIS)
Mueller, E.Z.
1984-05-01
In this report, the problem of calculating fission spectrum vectors in a consistent manner is formulated. The practical implications of using fission spectrum vectors in multi-group transport calculations are also addressed. The significance of the weighting spectra used for the calculation of fission spectrum vectors is illustrated for the case of a simple neutronic assembly
International Nuclear Information System (INIS)
Ganesan, S.; Muir, D.W.
1992-01-01
Selected neutron reaction nuclear data libraries and photon-atomic interaction cross section libraries for elements of interest to the IAEA's program on Fusion Evaluated Nuclear Data Library (FENDL) have been processed into MATXSR format using the NJOY system on the VAX4000 computer of the IAEA. This document lists the resulting multigroup data libraries. All the multigroup data generated are available cost-free upon request from the IAEA Nuclear Data Section. (author). 9 refs
Analysis of SPECTROX method of multigroup spectra calculation in unitary reactor cells
International Nuclear Information System (INIS)
Leite, Sergio de Q. Bogado
2005-01-01
The thermal neutron spectrum in a lattice cell is strongly space-dependent. In addition, in many situations, as for example in core design calculations, a more precise energetic and spatial representation of the flux is needed, which cannot be provided by few group diffusion theory. In such cases, the well-known SPECTROX method, employing diffusion theory in the moderator, where it is supposed sufficiently accurate, and collision probability theory in the fuel, together with appropriate interface current relations for assuring neutron conservation, has been widely used by WIMS as well as other codes. In this work, the approximations leading to the SPECTROX equations are reviewed and the calculated average fluxes in the fuel are compared with accurate values obtained from the solution of the transport equation by the FN method. (author)
Prompt fission neutron spectra and average prompt neutron multiplicities
International Nuclear Information System (INIS)
Madland, D.G.; Nix, J.R.
1983-01-01
We present a new method for calculating the prompt fission neutron spectrum N(E) and average prompt neutron multiplicity anti nu/sub p/ as functions of the fissioning nucleus and its excitation energy. The method is based on standard nuclear evaporation theory and takes into account (1) the motion of the fission fragments, (2) the distribution of fission-fragment residual nuclear temperature, (3) the energy dependence of the cross section sigma/sub c/ for the inverse process of compound-nucleus formation, and (4) the possibility of multiple-chance fission. We use a triangular distribution in residual nuclear temperature based on the Fermi-gas model. This leads to closed expressions for N(E) and anti nu/sub p/ when sigma/sub c/ is assumed constant and readily computed quadratures when the energy dependence of sigma/sub c/ is determined from an optical model. Neutron spectra and average multiplicities calculated with an energy-dependent cross section agree well with experimental data for the neutron-induced fission of 235 U and the spontaneous fission of 252 Cf. For the latter case, there are some significant inconsistencies between the experimental spectra that need to be resolved. 29 references
Neutron spectra characteristics for the intense neutron source, INS
International Nuclear Information System (INIS)
Battat, M.; Dierckx, R.; Emigh, C.R.
1977-01-01
The Intense Neutron Source, INS, facility is presently under construction at the Los Alamos Scientific Laboratory. Its purpose is to provide a broad base for research work related to the radiation effects produced by 14-MeV neutrons from a D-T burn of a fusion reactor. The INS facility produces a D-T burn-like reaction from the collision of an intense tritium-ion beam with a supersonic jet target of deuterium gas. The reaction produces a typical D-T 14-MeV neutron spectrum. By adding a fission blanket surrounding the D-T ''burn,'' the neutron spectral shape may be tailored to match almost perfectly the anticipated first-wall spectra from presently proposed fusion reactors. With a blanket in place, the total production of neutrons can be as large as 3 x 10 16 n/s and experimental volumes of the order of 1000 cm 3 can be available at flux levels greater than 0.6 x 10 14 n/cm 2 s
VARI-QUIR-3, 2-D Multigroup Steady-State Neutron Diffusion in X-Y R-Z or R-Theta Geometry
International Nuclear Information System (INIS)
Collier, George
1984-01-01
1 - Nature of physical problem solved: The steady-state, multigroup, two-dimensional neutron diffusion equations are solved in x-y, r-z, and r-theta geometry. 2 - Method of solution: A Gauss-Seidel type of solution with inner and outer iterations is used. The source is held constant during the inner iterations
Analysis of cavity effect on space- and time-dependent fast and thermal neutron energy spectra
International Nuclear Information System (INIS)
Kudo, Katsuhisa; Narita, Masakuni; Ozawa, Yasutomo.
1975-01-01
The effects of the presence of a central cavity on the space- and time-dependent neutron energy spectra in both thermal and fast neutron systems are analyzed theoretically with use made of the multi-group one-dimensional time-dependent Ssub(n) method. The thermal neutron field is also analyzed for the case of a fundamental time eigenvalue problem with the time-dependent P 1 approximation. The cavity radius is variable, and the system radius for graphite is 120 cm and for the other materials 7 cm. From the analysis of the time-dependent Ssub(n) calculations in the non-multiplying systems of polythene, light water and graphite, cavity heating is the dominant effect for the slowing-down spectrum in the initial period following fast neutron burst, and when the slowing-down spectrum comes into the thermal energy region, cavity heating shifts to cavity cooling. In the multiplying system of 235 U, cavity cooling also takes place as the spectrum approaches equilibrium after the fast neutron burst is injected. The mechanism of cavity cooling is explained analytically for the case of thermal neutron field to illustrate its physical aspects, using the time-dependent P 1 approximation. An example is given for the case of light water. (auth.)
Evaluation of secondary and prompt fission neutron spectra
Energy Technology Data Exchange (ETDEWEB)
Porodzinskij, Yu.V.; Sukhovitskij, E.Sh. [Radiation Physics and Chemistry Problems Inst., Minsk-Sosny (Belarus)
1997-03-01
A simple model allowing to split neutron emission spectra into reaction partials is suggested. Predicted spectra of (n,n`{gamma}), (n,n`f), etc appear to be much harder than usually evaluated. (author)
International Nuclear Information System (INIS)
Kawasaki, Hiromitsu; Seki, Yasushi.
1982-07-01
A computer code APPLE-2 which plots the spatial distribution of energy spectra of multi-group neutron and/or gamma ray fluxes, and reaction rates has been developed. This code is an improved version of the previously developed APPLE code and has the following features: (1) It plots energy spectra of neutron and/or gamma ray fluxes calculated by ANISN, DOT and MORSE. (2) It calculates and plots the spatial distribution of neutron and gamma ray fluxes and various types of reaction rates such as nuclear heating rates, operational dose rates, displacement damage rates. (3) Input data specification is greatly simplified by the use of standard, response libraries and by close coupling with radiation transport calculation codes. (4) Plotting outputs are given in camera ready form. (author)
International Nuclear Information System (INIS)
2005-01-01
A - Description of program or function: (1) Problems to be solved: MVP/GMVP can solve eigenvalue and fixed-source problems. The multigroup code GMVP can solve forward and adjoint problems for neutron, photon and neutron-photon coupled transport. The continuous-energy code MVP can solve only the forward problems. Both codes can also perform time-dependent calculations. (2) Geometry description: MVP/GMVP employs combinatorial geometry to describe the calculation geometry. It describes spatial regions by the combination of the 3-dimensional objects (BODIes). Currently, the following objects (BODIes) can be used. - BODIes with linear surfaces: half space, parallelepiped, right parallelepiped, wedge, right hexagonal prism; - BODIes with quadratic surface and linear surfaces: cylinder, sphere, truncated right cone, truncated elliptic cone, ellipsoid by rotation, general ellipsoid; - Arbitrary quadratic surface and torus. The rectangular and hexagonal lattice geometry can be used to describe the repeated geometry. Furthermore, the statistical geometry model is available to treat coated fuel particles or pebbles for high temperature reactors. (3) Particle sources: The various forms of energy-, angle-, space- and time-dependent distribution functions can be specified. (4) Cross sections: The ANISN-type PL cross sections or the double-differential cross sections can be used in the multigroup code GMVP. On the other hand, the specific cross section libraries are used in the continuous-energy code MVP. The libraries are generated from the evaluated nuclear data (JENDL-3.3, ENDF/B-VI, JEF-3.0 etc.) by using the LICEM code. The neutron cross sections in the unresolved resonance region are described by the probability table method. The neutron cross sections at arbitrary temperatures are available for MVP by just specifying the temperatures in the input data. (5) Boundary conditions: Vacuum, perfect reflective, isotropic reflective (white), periodic boundary conditions can be
REX1-87, Multigroup Neutron Cross-Sections from ENDF/B
International Nuclear Information System (INIS)
Gopalakrishnan, V.; Ganesan, S.
1988-01-01
1 - Description of program or function: The program calculates self- shielding factors for reactor applications from a pre-processed (linearized) evaluated nuclear data file in the ENDF/B format. 2 - Method of solution: Bondarenko definition of multigroup self- shielding factors invoking narrow resonance treatment is used. 3 - Restrictions on the complexity of the problem: a) Maximum no. of energy group is 620. b) Only the built-in forms of the weighting functions can be chosen. c) The program is strictly limited to resolved resonance region from physical considerations
International Nuclear Information System (INIS)
Gupta, I.J.; Trikha, S.K.
1977-01-01
Calculations are presented of the diffusion of thermal neutrons (2.5 x 10 -4 to 7 x 10 -1 eV) across an absorption discontinuity in a water assembly, consisting of pure water on one side and aqueous solutions of three different non-1/V absorbers on the other, which were obtained by solving the Boltzmann transport equation in the diffusion approximation using the multigroup formalism. The gradual appearance and disappearance of the depletion region in the neutron spectra (caused by the resonance absorption peaks at energies 0.096 and 0.179 eV for samarium and cadmium respectively), as one moves from the pure water assembly to the poisoned water assembly and vice versa, have also been studied. The minimum concentrations of Sm and Cd atoms in water for which the depletion region in the spectra just starts building up are found to be 60 x 10 18 Sm atom cm -3 and 125 x 10 18 Cd atom cm -3 respectively. However no such depletion region is observed in gadolinium-poisoned water assembly. At the boundary, the equilibrium neutron distribution gets disturbed and is re-established to the equilibrium distribution of the second medium at some distance from the interface. The diffusion lengths so calculated from the total neutron density curves are in good agreement with the experimental results of Goddard and Johnson (Nucl. Sci. Eng.; 37:127 (1969)) at various concentrations of Gd and Cd atoms in water. (author)
Mechanical approach to the neutrons spectra collimation and detection
Energy Technology Data Exchange (ETDEWEB)
Sadeghi, H.; Roshan, M. V. [Energy Engineering and Physics Department, Amirkabir University of Technology, Tehran (Iran, Islamic Republic of)
2014-11-15
Neutrons spectra from most of known sources require being collimated for numerous applications; among them one is the Neutron Activation Analysis. High energy neutrons are collimated through a mechanical procedure as one of the most promising methods. The output energy of the neutron beam depends on the velocity of the rotating Polyethylene disks. The collimated neutrons are then measured by an innovative detection technique with high accuracy.
Neutron spectra of /sup 239/Pu-Be neutron sources
Energy Technology Data Exchange (ETDEWEB)
Kumar, A; Nagarajan, P S [Bhabha Atomic Research Centre, Bombay (India). Div. of Radiation Protection
1977-01-01
Neutron spectra of /sup 239/Pu-Be(..cap alpha..,n) sources have been calculated by using the most recent data on the differential cross sections and angular distributions. The contribution from the multibody break-up reaction /sup 9/Be(..cap alpha..,..cap alpha..n)/sup 8/Be has also been incorporated. Modifications to the primary spectrum due to the secondary interactions in the source such as elastic scattering with beryllium, oxygen and plutonium and the /sup 9/Be(n,2n) and /sup 239/Pu(n,f) reaction have been calculated for different strengths and geometries. The present calculation has shown that the spectrum changes considerably because of these events within the source by way of smearing of peaks and filling up of valleys and raising the low energy part of the spectrum. Increase in H/D value leads to channeling of extra neutrons into the equatorial plane at the cost of the neutrons along the axial direction. The present calculations show that inclusion of secondary interactions to the extent considered in this work does not account completely for the increased intensity in the lower energy end of the measured spectrum.
Unfolding of neutron spectra from Godiva type critical assemblies
International Nuclear Information System (INIS)
Harvey, J.T.; Meason, J.L.; Wright, H.L.
1976-01-01
The results from three experiments conducted at the White Sands Missile Range Fast Burst Reactor Facility are discussed. The experiments were designed to measure the ''free-field'' neutron leakage spectrum and the neutron spectra from mildly perturbed environments. SAND-II was used to calculate the neutron spectrum utilizing several different trial input spectra for each experiment. Comparisons are made between the unfolded neutron spectrum for each trial input on the basis of the following parameters: average neutron energy (above 10 KeV), integral fluence (above 10 KeV), spectral index and the hardness parameter, phi/sub eq//phi
A multi-region boundary element method for multigroup neutron diffusion calculations
International Nuclear Information System (INIS)
Ozgener, H.A.; Ozgener, B.
2001-01-01
For the analysis of a two-dimensional nuclear system consisting of a number of homogeneous regions (termed cells), first the cell matrices which depend solely on the material composition and geometrical dimension of the cell (hence on the cell type) are constructed using a boundary element formulation based on the multigroup boundary integral equation. For a particular nuclear system, the cell matrices are utilized in the assembly of the global system matrix in block-banded form using the newly introduced concept of virtual side. For criticality calculations, the classical fission source iteration is employed and linear system solutions are by the block Gaussian-elimination algorithm. The numerical applications show the validity of the proposed formulation both through comparison with analytical solutions and assessment of benchmark problem results against alternative methods
International Nuclear Information System (INIS)
Ritchie, A.I.M.; Wilson, D.J.
1984-12-01
A multigroup diffusion code has been used to predict the count rate from a neutron moisture meter for a range of values of soil water content ω, thermal neutron absorption cross section Ssub(a) (defined as Σsub(a)/rho) of the soil matrix and soil matrix density rho. Two dimensions adequately approximated the geometry of the source, detector and soil surrounding the detector. Seven energy groups, the data for which were condensed from 128 group data set over the neutron energy spectrum appropriate to the soil-water mixture under study, proved adequate to describe neutron slowing-down and diffusion. The soil-water mixture was an SiO 2 →water mixture, with the absorption cross section of SiO 2 increased to cover the range of Σsub(a) required. The response to changes in matrix density is, in general, linear but the response to changes in water content is not linear over the range of parameter values investigated. Tabular results are presented which allow interpolation of the response for a particular ω, Ssub(a) and rho. It is shown that R(ω, Ssub(a), rho) rho M(Ssub(a)) + C(ω) is a crude representation of the response over a very limited range of variation of ω, and Ssub(a). As the response is a slowly varying function of rho, Ssub(a) and ω, a polynomial fit will provide a better estimate of the response for values of rho, Ssub(a) and ω not tabulated
Inclusive sum rules and spectra of neutrons at the ISR
International Nuclear Information System (INIS)
Grigoryan, A.A.
1975-01-01
Neutron spectra in pp collisions at ISR energies are studied in the framework of sum rules for inclusive processes. The contributions of protons, π- and E- mesons to the energy sum rule are calculated at √5 = 53 GeV. It is shown by means of this sum rule that the spectra of neutrons at the ISR are in contradiction with the spectra of other particles also measured at the ISR
BASACF, Integral Neutron Spectra Adjustment and Dosimetry
International Nuclear Information System (INIS)
Tichy, Milos
1996-01-01
1 - Description of program or function: Adjustment of a neutron spectrum based on integral detector measurements and calculation of an integral dosimetric quantity (integral flux, d.p.a., dose equivalent) and its variance. The program requires measured data (activities and their covariance matrix) and a priori information (spectrum, dosimetry cross sections, integral quantity conversion factor and their covariance matrices). All a priori covariance matrices can be read in from a file prepared by some other code or can be generated by means of three different methods (by subroutines included in the program). A subroutine which can normalize the a priori flux to measured data is also included. The program provides also adjusted dosimetry cross sections (with covariance matrix) so that it can be used for an adjustment of cross sections (or response functions of e.g. Bonner balls) by measurements in well-known neutron spectra. 2 - Method of solution: Bayesian theorem on conditional probability applied to linearized relation between activities, dosimetry cross sections and flux. All probability distributions are supposed to be normal and this supposition leads to minimizing of the same functional as least squares method (STAY'SL). This task is solved by a covariance filter method which avoids any matrix inversion and is numerically robust and stable. 3 - Restrictions on the complexity of the problem: This version can use 45 energy groups and 5 detectors and occupies 310 kB of main memory. This restriction can be modified according to available memory. The covariance matrix of activities is supposed diagonal. A solution is produced for any set of input data but in the case of non-consistent data, when measured activities do not match the a priori flux, the solution is not very meaningful
Fission neutron spectra measurements at LANSCE - Status and plans
International Nuclear Information System (INIS)
Haight, R. C.; Noda, S.; Nelson, R. O.; O'Donnell, J. M.; Devlin, M.; Chatillon, A.; Granier, T.; Taiebb, J.; Laurent, B.; Belier, G.; Becker, J. A.; Wu, C. Y.
2010-01-01
A program to measure fission neutron spectra from neutron-induced fission of actinides is underway at the Los Alamos Neutron Science Center (LANSCE) in a collaboration among the CEA laboratory at Bruyeres-le-Chatel, Lawrence Livermore National Laboratory and Los Alamos National Laboratory. The spallation source of fast neutrons at LANSCE is used to provide incident neutron energies from less than 1 MeV to 100 MeV or higher. The fission events take place in a gas-ionization fission chamber, and the time of flight from the neutron source to that chamber gives the energy of the incident neutron. Outgoing neutrons are detected by an array of organic liquid scintillator neutron detectors, and their energies are deduced from the time of flight from the fission chamber to the neutron detector. Measurements have been made of the fission neutrons from fission of 235 U, 238 U, 237 Np and 239 Pu. The range of outgoing energies measured so far is from 0.7 MeV to approximately 8 MeV. These partial spectra and average fission neutron energies are compared with evaluated data and with models of fission neutron emission. Results to date are summarized in this presentation. Future plans are to make significant improvements in the fission chambers, neutron detectors, signal processing, data acquisition and the experimental environment to provide high fidelity data including measurements of fission neutrons below 0.7 MeV and improvements in the data above 8 MeV. (authors)
International Nuclear Information System (INIS)
Calloo, A.A.
2012-01-01
In reactor physics, calculation schemes with deterministic codes are validated with respect to a reference Monte Carlo code. The remaining biases are attributed to the approximations and models induced by the multigroup theory (self-shielding models and expansion of the scattering law using Legendre polynomials) to represent physical phenomena (resonant absorption and scattering anisotropy respectively). This work focuses on the relevance of a polynomial expansion to model the scattering law. Since the outset of reactor physics, the latter has been expanded on a truncated Legendre polynomial basis. However, the transfer cross sections are highly anisotropic, with non-zero values for a very small range of the cosine of the scattering angle. Besides, the finer the energy mesh and the lighter the scattering nucleus, the more exacerbated is the peaked shape of this cross section. As such, the Legendre expansion is less suited to represent the scattering law. Furthermore, this model induces negative values which are non-physical. In this work, various scattering laws are briefly described and the limitations of the existing model are pointed out. Hence, piecewise-constant functions have been used to represent the multigroup scattering cross section. This representation requires a different model for the diffusion source. The discrete ordinates method which is widely employed to solve the transport equation has been adapted. Thus, the finite volume method for angular discretization has been developed and implemented in Paris environment which hosts the S n solver, Snatch. The angular finite volume method has been compared to the collocation method with Legendre moments to ensure its proper performance. Moreover, unlike the latter, this method is adapted for both the Legendre moments and the piecewise-constant functions representations of the scattering cross section. This hybrid-source method has been validated for different cases: fuel cell in infinite lattice
Creation and validation of a neutron-gamma coupled multigroup cross section library
International Nuclear Information System (INIS)
Devan, K.; Gopalakrishnan, V.; Lee, S.M.
1995-01-01
The task of creating our own neutron-gamma coupled library was taken up. By using 1985 version of NJOY code system, a coupled set called IGC-DE4-S1 in ANISN format for 25 nuclides has been arrived at based on ENDF/B-IV neutron library and DLC-99 gamma library, with Legendre order of up to 5. The flow chart for the creation of coupled set is given. 5 refs, 1 fig., 3 tabs
Bench mark spectra for high-energy neutron dosimetry
International Nuclear Information System (INIS)
Dierckx, R.
1986-01-01
To monitor radiation damage experiments, activation detectors are commonly used. The precision of the results obtained by the multiple foil analysis is largely increased by the intercalibration in bench-mark spectra. This technique is already used in dosimetry measurements for fission reactors. To produce neutron spectra similar to fusion reactor and high-energy high-intensity neutron sources (d-Li or spallation), accelerators can be used. Some possible solutions as p-Be and d-D 2 O neutron sources, useful as bench-mark spectra are described. (author)
Compilation of neutron flux density spectra and reaction rates in different neutron fields. V.3
International Nuclear Information System (INIS)
Ertek, C.
1980-04-01
Upon the recommendation of the International Working Group of Reactor Radiation Measurements (IWGRRM) a compilation of documents containing neutron flux density spectra and the reaction rates obtained by activiation and fission foils in different neutron fields is presented
International Nuclear Information System (INIS)
Yang, W.S.; Lee, C.H.
2008-01-01
Under the fast reactor simulation program launched in April 2007, development of an advanced multigroup cross section generation code was initiated in July 2007, in conjunction with the development of the high-fidelity deterministic neutron transport code UNIC. The general objectives are to simplify the existing multi-step schemes and to improve the resolved and unresolved resonance treatments. Based on the review results of current methods and the fact that they have been applied successfully to fast critical experiment analyses and fast reactor designs for last three decades, the methodologies of the ETOE-2/MC 2 -2/SDX code system were selected as the starting set of methodologies for multigroup cross section generation for fast reactor analysis. As the first step for coupling with the UNIC code and use in a parallel computing environment, the MC 2 -2 code was updated by modernizing the memory structure and replacing old data management package subroutines and functions with FORTRAN 90 based routines. Various modifications were also made in the ETOE-2 and MC 2 -2 codes to process the ENDF/B-VII.0 data properly. Using the updated ETOE-2/MC 2 -2 code system, the ENDF/B-VII.0 data was successfully processed for major heavy and intermediate nuclides employed in sodium-cooled fast reactors. Initial verification tests of the MC 2 -2 libraries generated from ENDF/B-VII.0 data were performed by inter-comparison of twenty-one group infinite dilute total cross sections obtained from MC 2 -2, VIM, and NJOY. For almost all nuclides considered, MC 2 -2 cross sections agreed very well with those from VIM and NJOY. Preliminary validation tests of the ENDF/B-VII.0 libraries of MC 2 -2 were also performed using a set of sixteen fast critical benchmark problems. The deterministic results based on MC 2 -2/TWODANT calculations were in good agreement with MCNP solutions within ∼0.25% Δρ, except a few small LANL fast assemblies. Relative to the MCNP solution, the MC 2 -2/TWODANT
Energy Technology Data Exchange (ETDEWEB)
Yang, W. S.; Lee, C. H. (Nuclear Engineering Division)
2008-05-16
Under the fast reactor simulation program launched in April 2007, development of an advanced multigroup cross section generation code was initiated in July 2007, in conjunction with the development of the high-fidelity deterministic neutron transport code UNIC. The general objectives are to simplify the existing multi-step schemes and to improve the resolved and unresolved resonance treatments. Based on the review results of current methods and the fact that they have been applied successfully to fast critical experiment analyses and fast reactor designs for last three decades, the methodologies of the ETOE-2/MC{sup 2}-2/SDX code system were selected as the starting set of methodologies for multigroup cross section generation for fast reactor analysis. As the first step for coupling with the UNIC code and use in a parallel computing environment, the MC{sup 2}-2 code was updated by modernizing the memory structure and replacing old data management package subroutines and functions with FORTRAN 90 based routines. Various modifications were also made in the ETOE-2 and MC{sup 2}-2 codes to process the ENDF/B-VII.0 data properly. Using the updated ETOE-2/MC{sup 2}-2 code system, the ENDF/B-VII.0 data was successfully processed for major heavy and intermediate nuclides employed in sodium-cooled fast reactors. Initial verification tests of the MC{sup 2}-2 libraries generated from ENDF/B-VII.0 data were performed by inter-comparison of twenty-one group infinite dilute total cross sections obtained from MC{sup 2}-2, VIM, and NJOY. For almost all nuclides considered, MC{sup 2}-2 cross sections agreed very well with those from VIM and NJOY. Preliminary validation tests of the ENDF/B-VII.0 libraries of MC{sup 2}-2 were also performed using a set of sixteen fast critical benchmark problems. The deterministic results based on MC{sup 2}-2/TWODANT calculations were in good agreement with MCNP solutions within {approx}0.25% {Delta}{rho}, except a few small LANL fast assemblies
Neutron spectra unfolding in Bonner spheres spectrometry using neural networks
International Nuclear Information System (INIS)
Kardan, M.R.; Setayeshi, S.; Koohi-Fayegh, R.; Ghiassi-Nejad, M.
2003-01-01
The neural network method has been used for the unfolding of neutron spectra in neutron spectrometry by Bonner spheres. A back propagation algorithm was used for training of neural networks 4mm x 4 mm bare LiI(Eu) and in a polyethylene sphere set: 2, 3, 4, 5, 6, 7, 8, 10, 12, 18 inch diameter have been used for unfolding of neutron spectra. Neural networks were trained by 199 sets of neutron spectra, which were subdivided into 6, 8, 10, 12, 15 and 20 energy bins and for each of them an appropriate neural network was designed and trained. The validation was performed by the 21 sets of neutron spectra. A neural network with 10 energy bins which had a mean value of error of 6% for dose equivalent estimation of spectra in the validation set showed the best results. The obtained results show that neural networks can be applied as an effective method for unfolding neutron spectra especially when the main target is neutron dosimetry. (author)
Energy Technology Data Exchange (ETDEWEB)
Oliva, Amaury M.; Filho, Hermes A.; Silva, Davi M.; Garcia, Carlos R., E-mail: aoliva@iprj.uerj.br, E-mail: halves@iprj.uerj.br, E-mail: davijmsilva@yahoo.com.br, E-mail: cgh@instec.cu [Universidade do Estado do Rio de Janeiro (UERJ), Nova Friburgo, RJ (Brazil). Instituto Politecnico. Departamento de Modelagem Computacional; Instituto Superior de Tecnologias y Ciencias Aplicadas (InSTEC), La Habana (Cuba)
2017-07-01
In this paper, we propose a numerical methodology for the development of a method of the spectral nodal class that will generate numerical solutions free from spatial truncation errors. This method, denominated Spectral Deterministic Method (SDM), is tested as an initial study of the solutions (spectral analysis) of neutron transport equations in the discrete ordinates (S{sub N}) formulation, in one-dimensional slab geometry, multigroup approximation, with linearly anisotropic scattering, considering homogeneous and heterogeneous domains with fixed source. The unknowns in the methodology are the cell-edge, and cell average angular fluxes, the numerical values calculated for these quantities coincide with the analytic solution of the equations. These numerical results are shown and compared with the traditional ne- mesh method Diamond Difference (DD) and the coarse-mesh method spectral Green's function (SGF) to illustrate the method's accuracy and stability. The solution algorithms problems are implemented in a computer simulator made in C++ language, the same that was used to generate the results of the reference work. (author)
International Nuclear Information System (INIS)
Ceolin, Celina
2010-01-01
The objective of this work is to obtain an analytical solution of the neutron diffusion kinetic equation in one-dimensional cartesian geometry, to monoenergetic and multigroup problems. These equations are of the type stiff, due to large differences in the orders of magnitude of the time scales of the physical phenomena involved, which make them difficult to solve. The basic idea of the proposed method is applying the spectral expansion in the scalar flux and in the precursor concentration, taking moments and solving the resulting matrix problem by the Laplace transform technique. Bearing in mind that the equation for the precursor concentration is a first order linear differential equation in the time variable, to enable the application of the spectral method we introduce a fictitious diffusion term multiplied by a positive value which tends to zero. This procedure opened the possibility to find an analytical solution to the problem studied. We report numerical simulations and analysis of the results obtained with the precision controlled by the truncation order of the series. (author)
International Nuclear Information System (INIS)
Hill, T. R.; Reed, W. H.
1980-01-01
1 - Description of problem or function: TIMEX solves the time- dependent, one-dimensional multigroup transport equation with delayed neutrons in plane, cylindrical, spherical, and two-angle plane geometries. Both regular and adjoint, inhomogeneous and homogeneous problems subject to vacuum, reflective, periodic, white, albedo or inhomogeneous boundary flux conditions are solved. General anisotropic scattering is allowed and anisotropic inhomogeneous sources are permitted. 2 - Method of solution: The discrete ordinates approximation for the angular variable is used with the diamond (central) difference approximation for the angular extrapolation in curved geometries. A linear discontinuous finite element representation for the angular flux in each spatial mesh cell is used. Negative fluxes are eliminated by a local set-to-zero and correct algorithm. The time variable is differenced by an explicit technique that is unconditionally stable so that arbitrarily large time-steps can be taken. Two acceleration methods, exponential extrapolation and re-balance, are utilized to improve the accuracy of the time differencing scheme. 3 - Restrictions on the complexity of the problem: Variable dimensioning is used so that any combination of problem parameters leading to a container array less than MAXCOR can be accommodated. In addition, the CDC version permits the use of extended core storage less than MAXECS
On the exact solution for the multi-group kinetic neutron diffusion equation in a rectangle
International Nuclear Information System (INIS)
Petersen, C.Z.; Vilhena, M.T.M.B. de; Bodmann, B.E.J.
2011-01-01
In this work we consider the two-group bi-dimensional kinetic neutron diffusion equation. The solution procedure formalism is general with respect to the number of energy groups, neutron precursor families and regions with different chemical compositions. The fast and thermal flux and the delayed neutron precursor yields are expanded in a truncated double series in terms of eigenfunctions that, upon insertion into the kinetic equation and upon taking moments, results in a first order linear differential matrix equation with source terms. We split the matrix appearing in the transformed problem into a sum of a diagonal matrix plus the matrix containing the remaining terms and recast the transformed problem into a form that can be solved in the spirit of Adomian's recursive decomposition formalism. Convergence of the solution is guaranteed by the Cardinal Interpolation Theorem. We give numerical simulations and comparisons with available results in the literature. (author)
International Nuclear Information System (INIS)
Woznicki, Z.I.
1983-07-01
This report presents the HEXAGA-III-programme solving multi-group time-independent real and/or adjoint neutron diffusion equations for three-dimensional-triangular-z-geometry. The method of solution is based on the AGA two-sweep iterative method belonging to the family of factorization techniques. An arbitrary neutron scattering model is permitted. The report written for users provides the description of the programme input and output and the use of HEXAGA-III is illustrated by a sample reactor problem. (orig.) [de
Procedure to Generate the MPACT Multigroup Library
Energy Technology Data Exchange (ETDEWEB)
Kim, Kang Seog [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
2015-12-17
The CASL neutronics simulator MPACT is under development for the neutronics and T-H coupled simulation for the light water reactor. The objective of this document is focused on reviewing the current procedure to generate the MPACT multigroup library. Detailed methodologies and procedures are included in this document for further discussion to improve the MPACT multigroup library.
Neutron spectra due 13N production in a PET cyclotron
International Nuclear Information System (INIS)
Benavente, J.A.; Vega-Carrillo, H.R.; Lacerda, M.A.S.; Fonseca, T.C.F.; Faria, F.P.; Silva, T.A. da
2015-01-01
Monte Carlo and experimental methods have been used to characterize the neutron radiation field around PET (Positron Emission Tomography) cyclotrons. In this work, the Monte Carlo code MCNPX was used to estimate the neutron spectra, the neutron fluence rates and the ambient dose equivalent (H*(10)) in seven locations around a PET cyclotron during 13 N production. In order to validate these calculations, H*(10) was measured in three sites and were compared with the calculated doses. All the spectra have two peaks, one above 0.1 MeV due to the evaporation neutrons and another in the thermal region due to the room-return effects. Despite the relatively large difference between the measured and calculated H*(10) for one point, the agreement was considered good, compared with that obtained for 18 F production in a previous work. - Highlights: • MCNPX code was used to estimate the neutron spectra in a PET cyclotron. • Neutrons were estimated when 13 N is produced. • Neutron spectra show evaporation and room-return neutrons. • Calculated H*(10) were compared with measured H*(10)
A code for leakage neutron spectra through thick shields
International Nuclear Information System (INIS)
Nagarajan, P.S.; Sethulakshmi, P.; Raghavendran, C.P.
1975-01-01
An exponential transform Monte Carlo code has been developed for deep penetration of neutrons and the results of leakage neutron spectra of this code have been compared with those of a basic Monte Carlo code for small thickness. The development of the code and optimisation of certain transform parameters are discussed and results are presented for a few thick shields of concrete and water in the context of neutron monitoring in the environs of accelerator and reactor shields. (author)
Development of 3D multi-group neutron diffusion code for hexagonal geometry
International Nuclear Information System (INIS)
Sun Wei; Wang Kan; Ni Dongyang; Li Qing
2013-01-01
Based on the theory of new flux expansion nodal method to solve the neutron diffusion equations, the intra-nodal fluence rate distribution was expanded in a series of analytic basic functions for each group. In order to improve the accuracy of calculation result, continuities of neutron fluence rate and current were utilized across the nodal surfaces. According to the boundary conditions, the iteration method was adopted to solve the diffusion equation, where inner iteration speedup method is Gauss-Seidel method and outer is Lyusternik-Wagner. A new speedup method (one-outer-iteration and multi-inner-iteration method) was proposed according to the characteristic that the convergence speed of multiplication factor is faster than that of neutron fluence rate and the update of inner iteration matrix is slow. Based on the proposed model, the code HANDF-D was developed and tested by 3D two-group vver440 benchmark, experiment 2 of HFETR, 3D four-group thermal reactor benchmark, and 3D seven-group fast reactor benchmark. The numerical results show that HANDF-D can predict accurately the multiplication factor and nodal powers. (authors)
Fission neutron spectra measurements at LANSCE - status and plans
International Nuclear Information System (INIS)
Haight, Robert C.; Noda, Shusaku; Nelson, Ronald O.; O' Donnell, John M.; Devlin, Matt; Chatillon, Audrey; Granier, Thierry; Taieb, Julien; Laurent, Benoit; Belier, Gilbert; Becker, John A.; Wu, Ching-Yen
2009-01-01
A program to measure fission neutron spectra from neutron-induced fission of actinides is underway at the Los Alamos Neutron Science Center (LANSCE) in a collaboration among the CEA laboratory at Bruyeres-le-Chatel, Lawrence Livermore National Laboratory and Los Alamos National Laboratory. The spallation source of fast neutrons at LANSCE is used to provide incident neutron energies from less than 1 MeV to 100 MeV or higher. The fission events take place in a gas-ionization fission chamber, and the time of flight from the neutron source to that chamber gives the energy of the incident neutron. Outgoing neutrons are detected by an array of organic liquid scintillator neutron detectors, and their energies are deduced from the time of flight from the fission chamber to the neutron detector. Measurements have been made of the fission neutrons from fission of 235 U, 238 U, 237 Np and 239 Pu. The range of outgoing energies measured so far is from 1 MeV to approximately 8 MeV. These partial spectra and average fission neutron energies are compared with evaluated data and with models of fission neutron emission. Results to date will be presented and a discussion of uncertainties will be given in this presentation. Future plans are to make significant improvements in the fission chambers, neutron detectors, signal processing, data acquisition and the experimental environment to provide high fidelity data including mea urements of fission neutrons below 1 MeV and improvements in the data above 8 MeV.
Neutron thermalization and spectra; Thermalisation et spectres de neutrons
Energy Technology Data Exchange (ETDEWEB)
Cadilhac, M; Soule, J L; Tretiakoff, O [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires
1964-07-01
The investigation of the neutron spectra in thermal reactors is taking an increasing importance due to the role played in them by Plutonium. Whatever the absorption law, it has been remarked that the scattering law in the.moderator affects the spectrum only through certain overall properties. It would thus seem possible to develop a simplified representation of this effect which would lead to a clear understanding of the phenomena, reducing at the same time the volume of numerical calculations required.. The synthetic model employed by the authors presents the advantage of reducing the determination of the spectra in an homogeneous medium to the resolution of a second order differential equation, like the Wigner-Wilkins model (monoatomic gaseous hydrogen) and the generalized heavy gas model of J. Horowitz which, incidentally, are both special cases. The model is, on the other hand, sufficiently general to allow a correct treatment of the situations met with in practice and in particular the important case where the presence of Plutonium introduces absorption resonances at low energy. Actually, the chemical or crystalline bonds of the moderator are introduced into the proposed model through two energy functions. These functions have been adjusted for the usual moderators (Graphite heavy water, light water) by means of known theoretical scattering laws. In a heterogeneous medium, the most important factor is the mean spectrum in the fuel of one cell, the knowledge of which is allowed by a generalization of the Amouyal-Benoist-Horowitz method. The proposed model lends itself particularly well to such calculations and also allows the effects of re-thermalization (for instance when the cooling system and the moderator are at different temperatures) to be treated. Finally, some examples are given of practical applications: codes for spectra and effective cross sections computations (editing of tables), codes for the treatment of neutron balance in a lattice or for the
Cyclotron Lines in Accreting Neutron Star Spectra
Wilms, Jörn; Schönherr, Gabriele; Schmid, Julia; Dauser, Thomas; Kreykenbohm, Ingo
2009-05-01
Cyclotron lines are formed through transitions of electrons between discrete Landau levels in the accretion columns of accreting neutron stars with strong (1012 G) magnetic fields. We summarize recent results on the formation of the spectral continuum of such systems, describe recent advances in the modeling of the lines based on a modification of the commonly used Monte Carlo approach, and discuss new results on the dependence of the measured cyclotron line energy from the luminosity of transient neutron star systems. Finally, we show that Simbol-X will be ideally suited to build and improve the observational database of accreting and strongly magnetized neutron stars.
Status of measurements of fission neutron spectra of Minor Actinides
Energy Technology Data Exchange (ETDEWEB)
Drapchinsky, L.; Shiryaev, B. [V.G. Khlopin Radium Inst., Saint Petersburg (Russian Federation)
1997-03-01
The report considers experimental and theoretical works on studying the energy spectra of prompt neutrons emitted in spontaneous fission and neutron induced fission of Minor Actinides. It is noted that neutron spectra investigations were done for only a small number of such nuclei, most measurements, except those of Cf-252, having been carried out long ago by obsolete methods and imperfectapparatus. The works have no detailed description of experiments, analysis of errors, detailed numerical information about results of experiments. A conclusion is made that the available data do not come up to modern requirements. It is necessary to make new measurements of fission prompt neutron spectra of transuranium nuclides important for the objectives of working out a conception of minor actinides transmutation by means of special reactors. (author)
The numerical analysis of eigenvalue problem solutions in the multigroup neutron diffusion theory
International Nuclear Information System (INIS)
Woznicki, Z.I.
1994-01-01
The main goal of this paper is to present a general iteration strategy for solving the discrete form of multidimensional neutron diffusion equations equivalent mathematically to an eigenvalue problem. Usually a solution method is based on different levels of iterations. The presented matrix formalism allows us to visualize explicitly how the used matrix splitting influences the matrix structure in an eigenvalue problem to be solved as well as the interdependence between inner and outer iteration within global iterations. Particular interactive strategies are illustrated by numerical results obtained for several reactor problems. (author). 21 refs, 32 figs, 15 tabs
The numerical analysis of eigenvalue problem solutions in the multigroup neutron diffusion theory
Energy Technology Data Exchange (ETDEWEB)
Woznicki, Z I [Institute of Atomic Energy, Otwock-Swierk (Poland)
1994-12-31
The main goal of this paper is to present a general iteration strategy for solving the discrete form of multidimensional neutron diffusion equations equivalent mathematically to an eigenvalue problem. Usually a solution method is based on different levels of iterations. The presented matrix formalism allows us to visualize explicitly how the used matrix splitting influences the matrix structure in an eigenvalue problem to be solved as well as the interdependence between inner and outer iteration within global iterations. Particular interactive strategies are illustrated by numerical results obtained for several reactor problems. (author). 21 refs, 32 figs, 15 tabs.
The numerical analysis of eigenvalue problem solutions in multigroup neutron diffusion theory
International Nuclear Information System (INIS)
Woznicki, Z.I.
1995-01-01
The main goal of this paper is to present a general iteration strategy for solving the discrete form of multidimensional neutron diffusion equations equivalent mathematically to an eigenvalue problem. Usually a solution method is based on different levels of iterations. The presented matrix formalism allows us to visualize explicitly how the used matrix splitting influences the matrix structure in an eigenvalue problem to be solved as well as the interdependence between inner and outer iterations within global iterations. Particular iterative strategies are illustrated by numerical results obtained for several reactor problems. (author). 21 refs, 35 figs, 16 tabs
Nodal deterministic simulation for problems of neutron shielding in multigroup formulation
International Nuclear Information System (INIS)
Baptista, Josue Costa; Heringer, Juan Diego dos Santos; Santos, Luiz Fernando Trindade; Alves Filho, Hermes
2013-01-01
In this paper, we propose the use of some computational tools, with the implementation of numerical methods SGF (Spectral Green's Function), making use of a deterministic model of transport of neutral particles in the study and analysis of a known and simplified problem of nuclear engineering, known in the literature as a problem of neutron shielding, considering the model with two energy groups. These simulations are performed in MatLab platform, version 7.0, and are presented and developed with the help of a Computer Simulator providing a friendly computer application for their utilities
Compilation of neutron flux density spectra and reaction rates in different neutron fields
International Nuclear Information System (INIS)
Ertek, C.
1979-07-01
Upon the recommendation of International Working Group of Reactor Radiation Measurements (IWGRRM), the compilation of neutron flux density spectra and the reaction rates obtained by activation and fission foils in different neutron fields is presented. The neutron fields considered are as follows: 1/E; iron block; LWR core and pressure vessel; LMFBR core and blanket; CTR first wall and blanket; fission spectrum
Survey of neutron spectra generated by the fission of heavy nuclei induced by fast neutrons
International Nuclear Information System (INIS)
Lovchikova, G.N.; Trufanov, A.M.
1997-01-01
A review of neutron fission spectra measurements is presented. This review and the results of this analysis was performed with the participation of the authors. It is shown that there is a need for additional measurements of the energy and angular distributions of secondary neutrons in order to improve the understanding of the neutron emission mechanism in fission. (author). 21 refs, 6 figs
International Nuclear Information System (INIS)
Hill, T.R.; Reed, W.H.
1976-01-01
TIMEX solves the time-dependent, one-dimensional multigroup transport equation with delayed neutrons in plane, cylindrical, spherical, and two-angle plane geometries. Both regular and adjoint, inhomogeneous and homogeneous problems subject to vacuum, reflective, periodic, white, albedo or inhomogeneous boundary flux conditions are solved. General anisotropic scattering is allowed and anisotropic inhomogeneous sources are permitted. The discrete ordinates approximation for the angular variable is used with the diamond (central) difference approximation for the angular extrapolation in curved geometries. A linear discontinuous finite element representation for the angular flux in each spatial mesh cell is used. The time variable is differenced by an explicit technique that is unconditionally stable so that arbitrarily large time steps can be taken. Because no iteration is performed the method is exceptionally fast in terms of computing time per time step. Two acceleration methods, exponential extrapolation and rebalance, are utilized to improve the accuracy of the time differencing scheme. Variable dimensioning is used so that any combination of problem parameters leading to a container array less than MAXCOR can be accommodated. The running time for TIMEX is highly problem-dependent, but varies almost linearly with the total number of unknowns and time steps. Provision is made for creation of standard interface output files for angular fluxes and angle-integrated fluxes. Five interface units (use of interface units is optional), five output units, and two system input/output units are required. A large bulk memory is desirable, but may be replaced by disk, drum, or tape storage. 13 tables, 9 figures
Neutron spectra measuring by magnetless hadron spectrometer
International Nuclear Information System (INIS)
Bayukov, Yu.D.; Buklej, A.E.; Gavrilov, V.B.
1980-01-01
The energy resolution, efficiency and background conditions of neutron recording in inclusive nuclear reactions by a magnetless hadron spectrometer (MHS) in the 8-300 MeV energy range. The scheme of apparatus lay-out for measuring neutron recording efficiency is shown. For recording colliding particles with the 3 GeV/c momentum four beam scintillation counters, the latter of which of 30x40 mm dimensions and 1 mm thickness defines the working beam range in the target centre, are used. Targets of the 80 mm diameter made of C and Pb (2.08 g/cm 2 and 3.04 g/cm 2 thickness, respectively) are located at the 45 deg angle in respect to the beam direction. Secondary particles escaping at the 90 deg angle are recorded by two telescopes of the scintillation counters. For neutron and γ quanta recording the special scintillation detector of the 20 cm thickness encircled by an anticoincidence counter is used. The neutron recording efficiency is determined on the basis of comparison of the neutron production differential cross sections of the π +- 12 C 6 → nX reactions and of proton production in isotopically symmetric reactions π +- 12 C 6 → pX. The experimental data are in good agreement with the calculation data [ru
Energy Technology Data Exchange (ETDEWEB)
Vega C, H.R.; Hernandez D, V.M.; Manzanares A, E. [Cuerpo Academico de Radiobiologia, Estudios Nucleares, Universidad Autonoma de Zacatecas, A.P. 336, 98000 Zacatecas (Mexico)] e-mail: rvega@cantera.reduaz.mx [and others
2003-07-01
A neural network has been used to reconstruct the neutron spectra starting from the counting rates of the detectors of the Bonner sphere spectrophotometric system. A group of 56 neutron spectra was selected to calculate the counting rates that would produce in a Bonner sphere system, with these data and the spectra it was trained the neural network. To prove the performance of the net, 12 spectra were used, 6 were taken of the group used for the training, 3 were obtained of mathematical functions and those other 3 correspond to real spectra. When comparing the original spectra of those reconstructed by the net we find that our net has a poor performance when reconstructing monoenergetic spectra, this attributes it to those characteristic of the spectra used for the training of the neural network, however for the other groups of spectra the results of the net are appropriate with the prospective ones. (Author)
International Nuclear Information System (INIS)
Chang, Jonghwa
2014-01-01
Today, we can use a computer cluster consist of a few hundreds CPUs with reasonable budget. Such computer system enables us to do detailed modeling of reactor core. The detailed modeling will improve the safety and the economics of a nuclear reactor by eliminating un-necessary conservatism or missing consideration. To take advantage of such a cluster computer, efficient parallel algorithms must be developed. Mechanical structure analysis community has studied the domain decomposition method to solve the stress-strain equation using the finite element methods. One of the most successful domain decomposition method in terms of robustness is FETI-DP. We have modified the original FETI-DP to solve the eigenvalue problem for the multi-group diffusion problem in previous study. In this study, we report the result of recent modification to handle the three-dimensional subdomain partitioning, and the sub-domain multi-group problem. Modified FETI-DP algorithm has been successfully applied for the eigenvalue problem of multi-group neutron diffusion equation. The overall CPU time is decreasing as number of sub-domains (partitions) is increasing. However, there may be a limit in decrement due to increment of the number of primal points will increase the CPU time spent by the solution of the global equation. Even distribution of computational load (criterion a) is important to achieve fast computation. The subdomain partition can be effectively performed using suitable graph theory partition package such as MeTIS
Energy Technology Data Exchange (ETDEWEB)
Chang, Jonghwa [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)
2014-10-15
Today, we can use a computer cluster consist of a few hundreds CPUs with reasonable budget. Such computer system enables us to do detailed modeling of reactor core. The detailed modeling will improve the safety and the economics of a nuclear reactor by eliminating un-necessary conservatism or missing consideration. To take advantage of such a cluster computer, efficient parallel algorithms must be developed. Mechanical structure analysis community has studied the domain decomposition method to solve the stress-strain equation using the finite element methods. One of the most successful domain decomposition method in terms of robustness is FETI-DP. We have modified the original FETI-DP to solve the eigenvalue problem for the multi-group diffusion problem in previous study. In this study, we report the result of recent modification to handle the three-dimensional subdomain partitioning, and the sub-domain multi-group problem. Modified FETI-DP algorithm has been successfully applied for the eigenvalue problem of multi-group neutron diffusion equation. The overall CPU time is decreasing as number of sub-domains (partitions) is increasing. However, there may be a limit in decrement due to increment of the number of primal points will increase the CPU time spent by the solution of the global equation. Even distribution of computational load (criterion a) is important to achieve fast computation. The subdomain partition can be effectively performed using suitable graph theory partition package such as MeTIS.
Determination of neutron spectra using the programs GNSR and SPECTRIX
International Nuclear Information System (INIS)
Weyrauch, M.; Dietz, E.; Matzke, M.
2002-01-01
We describe the capabilities and the application of two computer programs, which have been developed in order to facilitate common tasks in neutron spectrometry: GNSR (calculation of response matrices) and SPECTRIX (unfolding). Gas-filled Neutron Spectrometer Response calculates response functions and response matrices of various gas-filled neutron detectors. It can be configured to accommodate the appropriate gas-fillings and supports a number of different neutron beam configurations with a possibility to input calculated or measured neutron beam spectra. The program includes graphical capabilities as well as a context-sensitive help system. SPECTRIX implements several unfolding algorithms as well as support algorithms for unfolding and includes graphics capabilities and context-sensitive help. We apply both programs to a specific example: calculation of the response matrix of a 3 He detector and unfolding of the neutron spectrum of a thick accelerator target using the calculated response matrix
Energy Technology Data Exchange (ETDEWEB)
Ceolin, Celina; Schramm, Marcelo; Bodmann, Bardo Ernst Josef; Vilhena, Marco Tullio Mena Barreto de [Universidade Federal do Rio Grande do Sul, Porto Alegre (Brazil). Programa de Pos-Graduacao em Engenharia Mecanica; Bogado Leite, Sergio de Queiroz [Comissao Nacional de Energia Nuclear, Rio de Janeiro (Brazil)
2014-11-15
In this work the authors solved the steady state neutron diffusion equation for a multi-layer slab assuming the multi-group energy model. The method to solve the equation system is based on an expansion in Taylor Series resulting in an analytical expression. The results obtained can be used as initial condition for neutron space kinetics problems. The neutron scalar flux was expanded in a power series, and the coefficients were found by using the ordinary differential equation and the boundary and interface conditions. The effective multiplication factor k was evaluated using the power method. We divided the domain into several slabs to guarantee the convergence with a low truncation order. We present the formalism together with some numerical simulations.
ANS - the analysis of the neutron spectra
International Nuclear Information System (INIS)
Ivanov, B.I.; Rosek, J.
1991-01-01
The program ANS which is the graphical user friendly program to process evaluated neutron data files for interpretation of transmission experiments. The ANS program was written in the Turbo Pascal v. 5 language and may work on the IBM AT with Math CoProcessor. 3 refs.; 1 fig
International Nuclear Information System (INIS)
Woznicki, Z.
1979-06-01
This report presents the AGA two-sweep iterative methods belonging to the family of factorization techniques in their practical application in the HEXAGA-II two-dimensional programme to obtain the numerical solution to the multi-group, time-independent, (real and/or adjoint) neutron diffusion equations for a fine uniform triangular mesh. An arbitrary group scattering model is permitted. The report written for the users provides the description of input and output. The use of HEXAGA-II is illustrated by two sample reactor problems. (orig.) [de
International Nuclear Information System (INIS)
Pashchenko, A.B.; Wienke, H.; Ganesan, S.
1996-01-01
Selected neutron reaction nuclear data evaluations and photon-atomic interaction cross section libraries for elements of interest to the IAEA's program on Fusion Evaluated Nuclear Data Library (FENDL) have been processed into GENDF and MATXS format using the NJOY system by R.E. MacFarlane, in VITAMIN-J group structure with VITAMIN-E weighting spectrum. This document summarizes the resulting multigroup data library FENDL/MG version 1.1. The data are available costfree, upon request from the IAEA Nuclear Data Section, online or on magnetic tape. (author). 7 refs, 1 tab
Calculation of Spectra of Neutrons and Charged Particles Produced in a Target of a Neutron Generator
Gaganov, V. V.
2017-12-01
An algorithm for calculating the spectra of neutrons and associated charged particles produced in the target of a neutron generator is detailed. The products of four nuclear reactions 3H( d, n)4He, 2H( d, n)3He, 2H( d, p)3H, and 3He( d, p)4He are analyzed. The results of calculations are presented in the form of neutron spectra for several emission angles and spectra of associated charged particles emitted at an angle of 180° for a deuteron initial energy of 0.13 MeV.
The measurement of neutron and neutron induced photon spectra in fusion reactor related assemblies
Unholzer, S; Klein, H; Seidel, K
2002-01-01
The spectral neutron and photon fluence (or flux) measured outside and inside of assemblies related to fusion reactor constructions are basic quantities of fusion neutronics. The comparison of measured spectra with the results of MCNP neutron and photon transport calculations allows a crucial test of evaluated nuclear data as generally used in fusion applications to be carried out. The experiments concern mixed neutron/photon fields with about the same intensity of the two components. An NE-213 scintillation spectrometer, well described by response matrices for both neutrons and photons, is used as proton-recoil and Compton spectrometer. The experiments described here in more detail address the background problematic of two applications, an iron benchmark experiment with an ns-pulsed neutron source and a deep penetration mock-up experiment for the investigation of the ITER in-board shield system. The measured spectral neutron and photon fluences are compared with spectra calculated with the MCNP code on the b...
Logic based feature detection on incore neutron spectra
International Nuclear Information System (INIS)
Bende-Farkas, S.; Kiss, S.; Racz, A.
1992-09-01
A methodology is proposed to investigate neutron spectra in such a way which is similar to human thinking. The goal was to save experts from tedious, mechanical tasks of browsing a large amount of signals in order to recognize changes in the underlying mechanisms. The general framework for detecting features of incore neutron spectra with a rulebased methodology is presented. As an example, the meaningful peaks in the APSDs are determined. This method is a part of a wider project to develop a noise diagnostic expert system. (R.P.) 6 refs.; 6 figs.; 1 tab
Energy Technology Data Exchange (ETDEWEB)
Nguyen-Ngoc, H [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires
1969-07-01
In order to reduce computing time, two and three-dimensional multigroup neutron diffusion equations in cylindrical, rectangular (X, Y), (X, Y, Z) and hexagonal geometries are solved by the method of synthesis using an appropriate variational principle (stationary principle). The basic idea is to reduce the number of independent variables by constructing two or three-dimensional solutions from solutions of fewer variables, hence the name 'synthesis method'. Whatever the geometry, we are led to solve a system of ordinary differential equations with matrix coefficients to which one can apply well-known numerical methods: CHEBYSHEV's polynomial method, Gaussian elimination. Numerical results furnished by synthesis programs written for the IBM 7094, the IBM 360-75 and the CDC 6600 computers, are confronted with those which are given by programs employing the classical finite difference method. [French] En vue de reduire le-temps de calcul, les equations de diffusion neutronique, multigroupe, a deux et trois dimensions d'espace dans les geometries cylindrique, rectangulaire (X, Y), (X, Y, Z) et hexagonale sont resolues par la methode de synthese utilisant un principe variationnel approprie (principe stationnaire). L'idee consiste a reduire le nombre de variables independantes par construction d'une solution bi ou tridimensionnelle au moyen de solutions dependant d'un nombre inferieur de variables, d'ou le nom de la methode. Dans tous les cas de geometrie, nous sommes conduits a resoudre un systeme d'equations differentielles a coefficients matriciels auquel peuvent s'appliquer les methodes numeriques courantes; methode polynomiale de TCHEBYCHEFF et methode d'elimination de GAUSS. Les resultats numeriques obtenus par nos codes de synthese programmes sur IBM 7094, IBM 360-75 et CDC 6600, sont confrontes avec ceux que fournissent les programmes adoptant la methode classique des differences finies. (auteur)
Uncertainties related to numerical methods for neutron spectra unfolding
International Nuclear Information System (INIS)
Glodic, S.; Ninkovic, M.; Adarougi, N.A.
1987-10-01
One of the often used techniques for neutron detection in radiation protection utilities is the Bonner multisphere spectrometer. Besides its advantages and universal applicability for evaluating integral parameters of neutron fields in health physics practices, the outstanding problems of the method are data analysis and the accuracy of the results. This paper briefly discusses some numerical problems related to neutron spectra unfolding, such as uncertainty of the response matrix as a source of error, and the possibility of real time data reduction using spectrometers. (author)
The background cross section method for calculating the epithermal neutron spectra
International Nuclear Information System (INIS)
Martinez, A.S.
1983-01-01
We have developed a new methodology to the multigroup constants calculations, for thermal and fast reactors. The method to obtain the constants is extremely fast and simple, and it avoid repeated computations of the detailed neutron spectrum for different cell configurations (composition, geometry and temperature). (author) [pt
International Nuclear Information System (INIS)
1968-01-01
Proceedings of a Symposium organized by the IAEA and held at Ann Arbor, Michigan, USA, 17 - 21 July 1967. The meeting was attended by 143 participants from 24 Member States and one international organization. Contents: (Vol.I) Theory of neutron thermalization (15 papers); Scattering law (20 papers); Angular, space, temperature and time dependence of neutron spectra (9 papers). (Vol.II) Measurement of thermal neutron spectra and spectral indices, and comparison with theory (17 papers); Time-dependent problems in neutron thermalization (12 papers). Each paper is in its original language (61 English, 1 French and 11 Russian) and is preceded by an abstract in English with one in the original language if this is not English. Discussions are in English.
Measurements of {sup 237}Np secondary neutron spectra
Energy Technology Data Exchange (ETDEWEB)
Kornilov, N.V.
1997-03-01
The activities carried out during the first year of the project are summarized. The main problems for Np spectra measurements arise from high intrinsic gamma-ray activity of the sample and admixture of the oxygen and iron nuclei. The inelastically scattered neutrons and the fission neutrons spectra for {sup 237}Np were measured by time-of-flight spectrometer of the IPPE at incident neutron energies {approx_equal}1.5 MeV, and {approx_equal}0.5 MeV. A solid tritium target and a Li-metallic target were used as neutron sources. The neutron scattering on C sample (C(n,n) standard reaction) was measured to normalize the Np data. The experimental data should be simulated by Monte Carlo method to correct the experimental data for oxygen and iron admixture as well as for multiple scattering of the neutrons in the sample. Therefore the response function of the spectrometer, and the neutron energy distribution from the source were investigated in detail. (author)
Spallation neutron spectra measured at Saturne
International Nuclear Information System (INIS)
Boyard, J.L.; Bouyer, P.; Brochard, F.; Duchazeaubeneix, J.C.; Durand, J.M.; Leray, S.; Milleret, G.; Plouin, F.; Uematsu, M.; Whittal, D.M.; Martinez, E.; Beau, M.; Boue, F.; Crespin, S.; Drake, D.; Frehaut, J.; Lochard, J.P.; Patin, Y.; Petibon, E.; Legrain, R.; Terrien, Y.
1995-01-01
Good knowledge of spallation reactions is necessary to design accelerator-based transmutation systems. An extensive program has begun at Saturne to measure energy and angular distributions of neutrons produced by incident protons or deuterons of up to 2 GeV on several thin targets. Our measurements will extend the available data to higher energies than the present limit of 800 MeV enabling improvements to the codes which are sometimes in poor agreement with the data. (Authors). 7 refs., 7 figs
International Nuclear Information System (INIS)
Kim, Jung-Do; Lee, Jong Tai
1986-01-01
Description of problem or function: Format: TEMPEST and MUFT; Number of groups: 246 thermal groups in TEMPEST Format and 54 fast groups in MUFT Format. From this library, the program SPOTS4 generates a 172-54 group library as input to the code LEOPARD. Nuclides: H, O, Zr, C, Fe, Ni, Al, Cr, Mn, U, Pu, Th, Pa, Xe, Sm, B and D. Origin: ENDF/B-4; Weighting spectrum: 1/E + U 235 fission spectrum. Data library of thermal and fast neutron group Cross sections to generate input to the program LEOPARD. The data is based on ENDF/B-4 and consists of two parts: (1) 246 thermal groups in TEMPEST Format. (2) 54 fast groups in MUFT Format. From this library, the program SPOTS4 generates a 172-54 group library as input to the code LEOPARD (NESC0279)
International intercomparison of neutron spectra evaluating methods using activation detectors
International Nuclear Information System (INIS)
Fischer, A.
1975-06-01
The international intercomparison of neutron spectrum evaluation methods using activation detectors was organized by the IAEA in 1971 - 1972. All of the contributions and the results of a critical evaluation are presented here. The spectra of different contributors are compared to a reference spectrum by means of different integrals and weighting functions. Different cross section sets, foil numbers, energy point systems, guess spectra used by the contributors cause differences in the resulting spectra. The possible ways of separating these effects are also investigated. Suggestions are made for the organization of a new intercomparison on the basis of more uniform input data. (orig.) [de
Logic based feature detection on incore neutron spectra
Energy Technology Data Exchange (ETDEWEB)
Racz, A.; Kiss, S.; Bende-Farkas, S. (Hungarian Academy of Sciences, Budapest (Hungary). Central Research Inst. for Physics)
1993-04-01
A general framework for detecting features of incore neutron spectra with a rule-based methodology is presented. As an example, we determine the meaningful peaks in the APSD-s. This work is part of a larger project, aimed at developing a noise diagnostic expert system. (Author).
Calculation of prompt neutron spectra for curium isotopes
Energy Technology Data Exchange (ETDEWEB)
Ohsawa, Takaaki [Kinki Univ., Higashi-Osaka, Osaka (Japan). Atomic Energy Research Inst.
1997-03-01
With the aim of checking the existing evaluations contained in JENDL-3.2 and providing new evaluations based on a methodology proposed by the author, a series of calculations of prompt neutron spectra have been undertaken for curium isotopes. Some of the evaluations in JENDL-3.2 was found to be unphysically hard and should be revised. (author)
Neutron spectra from radionuclide sources for cardiac pacemakers
International Nuclear Information System (INIS)
Kluge, H.
1975-01-01
Neutron spectra from Plutonium 238 radioisotope batteries powering cardiac pacemakers are measured in the energy range above 0.7 MeV. The results are used to calculate radiation doses within a cylindrical phantom. There are only minor differences between the different types of plutonium 238-batteries and californium 252-batteries
Informational-computer system for the neutron spectra analysis
International Nuclear Information System (INIS)
Berzonis, M.A.; Bondars, H.Ya.; Lapenas, A.A.
1979-01-01
In this article basic principles of the build-up of the informational-computer system for the neutron spectra analysis on a basis of measured reaction rates are given. The basic data files of the system, needed software and hardware for the system operation are described
Measurement of fast neutron spectra. 1-2
International Nuclear Information System (INIS)
Kimura, Itsuro
1976-01-01
The present status of the techniques for the measurement of fast neutron spectra is reviewed with particular attention to the recent activities in Japan. The first section of this report defines the energy range of fast neutrons, and various techniques are classified into four groups. In the following sections, recent development in each group is reviewed. The first part is the integral method represented mainly by the activation method. The variation of this method is shortly reviewed, and some results of the spectrum measurement for JRR-4 (a thermal research reactor) and YAYOI (a fast neutron source reactor) are presented together with the results of computed spectra. The second part is the method of proton recoil. The improvement of a proportional counter by Ichimori is shortly reviewed. The use of liquid scintillator is also discussed together with the experimental and computational results of YAYOI benchmark spectra of fast neutrons transmitted through the layers of iron. The utilization of n-α or n-p reaction as a sandwitch counter is discussed in the third part. Measured and calculated spectra in the FCA (a fast critical assembly) core are presented as examples. The method of time-of-flight is discussed in the fourth part. Recent developments in Japan such as the method with a double-scintillation counter are shortly presented together with its block diagram. (Aoki, K.)
Measurement of neutron spectra through composed material block bombarded with D-T neutrons
Energy Technology Data Exchange (ETDEWEB)
Zhu, T.H. [Institute of Nuclear Physics and Chemistry, China Academy of Engineering Physics, P.O. BOX 919-213, Mian yang 621900 (China)], E-mail: zhutonghua@yahoo.com.cn; Liu, R.; Lu, X.X.; Jiang, L.; Wen, Z.W.; Wang, M.; Lin, J.F. [Institute of Nuclear Physics and Chemistry, China Academy of Engineering Physics, P.O. BOX 919-213, Mian yang 621900 (China)
2009-12-15
A 2-dimensional composed material assembly made of the iron and hydric block has been established. The neutron spectra from the assembly bombarded with 14-MeV neutrons at neutron generator have been obtained using the proton recoil technique with a stillbene detector. The detector positions were selected at the 60 deg., 120 deg., 180 deg. on the surface of the iron spherical shell. The background neutron spectra consisted of background and room return radiation were subtracted with combination of methods of experimental shielding and MCNP calculation. The uncertainty of results was 6.3-7.4%. The experiment results were analyzed and simulated by MCNP code and two data library. The difference is integral neutron flux (background neutron subtracted) of measured results greater than calculations with maximum of 21.2% in the range of 1-16 MeV.
NEUPAC, Experimental Neutron Spectra Unfolding with Sensitivities
International Nuclear Information System (INIS)
Sasaki, Makoto; Nakazawa, Masaharu
1986-01-01
1 - Description of problem or function: The code is able to determine the integral quantities and their sensitivities, together with an estimate of the unfolded spectrum and integral quantities. The code also performs a chi-square test of the input/output data, and contains many options for the calculational routines. 2 - Method of solution: The code is based on the J1-type unfolding method, and the estimated neutron flux spectrum is obtained as its solution. 3 - Restrictions on the complexity of the problem: The maximum number of energy groups used for unfolding is 620. The maximum number of reaction rates and the window functions given as input is 20. The total storage requirement depends on the amount of input data
Neutron spectra measurements and neutron flux monitoring for radiation damage purposes
International Nuclear Information System (INIS)
Osmera, B.; Petr, J.; Racek, J.; Rumler, C.; Turzik, Z.; Franc, L.; Holman, M.; Hogel, J.; Kovarik, K.; Marik, P.; Vespalec, R.; Albert, D.; Hansen, V.; Vogel, W.
1979-09-01
Neutron spectra were measured for the TR-0, WWR-S and SR-0 experimental reactors using the recoil proton method, 6 Li spectrometry, scintillation spectrometry and activation detectors in a variety of conditions. Neutron fluence was also measured and calculated. (M.S.)
The study of prompt neutron spectra of 238U fission induced by fast neutron
International Nuclear Information System (INIS)
Li Anli; Bai Xixiang; Wang Yufeng; Wang Xiaozhong; Men Jiangchen; Huang Shengnian
1990-01-01
The measurements of prompt neutron time-of-flight spectra of U fission induced by 11 MeV neutrons were carried out at HI-13 Tandem Van de Graaff Accelerator Laboratory in 1989. The block diagram of the electronics is shown. A fission neutron TOF spectrum for the sixth section of the fission plates and the left detector at low bias is given. The data accumulation time is 60 h
Adjusted neutron spectra of STEK cores for reactivity calculations
International Nuclear Information System (INIS)
Dekker, J.W.M.; Dragt, J.B.; Janssen, A.J.; Heijboer, R.J.; Klippel, H.Th.
1978-02-01
Neutron flux and adjoint flux spectra form a pre-requisite in the analysis of reactivity worth data measured in the STEK facility. First, a survey of all available information about these spectra is given. Next a special application of a general adjustment method is described. This method has been used to obtain adjusted STEK group flux and adjoint flux spectra, starting from calculated spectra. These theoretical spectra were adjusted to reactivity worths of natural boron (nat. B) and 235 U as well as a number of fission reaction rates. As a by-product in this adjustment calculation adjusted fission group cross sections of 235 U were obtained. The results, viz. group fluxes and adjoint fluxes and adjusted fission cross sections of 235 U are given. They have been used for the interpretation of fission product reactivity worth measurements made in STEK
The determination of neutron energy spectra of radioisotope sources
International Nuclear Information System (INIS)
Lutkin, J.E.
1975-08-01
The neutron energy spectrum of a 241 Am-Be radioisotope neutron source has been determined by use of a time of flight neutron spectrometer; this spectrometer not being subject to the same uncertainties as a scintillation spectrometer. Neutron spectra have been determined using a scintillation spectrometer with which the effects of instrumental uncertainties, particularly the pulse shape discrimination have been assessed. In the course of the development of the time flight spectrometer a zero crossover pulse shape discrimination system was developed in order to reduce the unwanted background. Using this system a quantitative survey of pulse shape discrimination with experimental and commercial liquid and plastic organic scintillators were carried out. In addition the pulse shape discrimination properties of inorganic scintillators were also examined. (author)
Delayed neutron spectra from short pulse fission of uranium-235
International Nuclear Information System (INIS)
Atwater, H.F.; Goulding, C.A.; Moss, C.E.; Pederson, R.A.; Robba, A.A.; Wimett, T.F.; Reeder, P.; Warner, R.
1986-01-01
Delayed neutron spectra from individual short pulse (∼50 μs) fission of small 235 U samples (50 mg) were measured using a small (5 cm OD x 5 cm length) NE 213 neutron spectrometer. The irradiating fast neutron flux (∼10 13 neutrons/cm 2 ) for these measurements was provided by the Godiva fast burst reactor at the Los Alamos Critical Experiment Facility (LACEF). A high speed pneumatic transfer system was used to transfer the 50 mg 235 U samples from the irradiation position near the Godiva assembly to a remote shielded counting room containing the NE 213 spectrometer and associated electronics. Data were acquired in sixty-four 0.5 s time bins and over an energy range 1 to 7 MeV. Comparisons between these measurements and a detailed model calculation performed at Los Alamos is presented
Neutron dose and energy spectra measurements at Savannah River Plant
International Nuclear Information System (INIS)
Brackenbush, L.W.; Soldat, K.L.; Haggard, D.L.; Faust, L.G.; Tomeraasen, P.L.
1987-08-01
Because some workers have a high potential for significant neutron exposure, the Savannah River Plant (SRP) contracted with Pacific Northwest Laboratory (PNL) to verify the accuracy of neutron dosimetry at the plant. Energy spectrum and neutron dose measurements were made at the SRP calibrations laboratory and at several other locations. The energy spectra measurements were made using multisphere or Bonner sphere spectrometers, 3 He spectrometers, and NE-213 liquid scintillator spectrometers. Neutron dose equivalent determinations were made using these instruments and others specifically designed to determine dose equivalent, such as the tissue equivalent proportional counter (TEPC). Survey instruments, such as the Eberline PNR-4, and the thermoluminescent dosimeter (TLD)-albedo and track etch dosimeters (TEDs) were also used. The TEPC, subjectively judged to provide the most accurate estimation of true dose equivalent, was used as the reference for comparison with other devices. 29 refs., 43 figs., 13 tabs
Calculation of neutron spectra produced in neutron generator target: Code testing.
Gaganov, V V
2018-03-01
DT-neutron spectra calculated using the SRIANG code was benchmarked against the results obtained by widely used Monte Carlo codes: PROFIL, SHORIN, TARGET, ENEA-JSI, MCUNED, DDT and NEUSDESC. The comparison of the spectra obtained by different codes confirmed the correctness of SRIANG calculations. The cross-checking of the compared spectra revealed some systematic features and possible errors of analysed codes. Copyright © 2017 Elsevier Ltd. All rights reserved.
Systematic evaluation of prompt neutron spectra in fission
International Nuclear Information System (INIS)
Osawa, Takaaki
1995-01-01
To create the nuclear data fail JEND-32, the prompt fission neutron spectra X(E) of 233 U, 235 U, 238 U and 239 Pu were reevaluated and some improvement were added to the calculation models. We tried to extend the calculation method of fission spectra of nuclides with poor measurement data in consideration of increasing the importance of nuclear data of minor actinoids. We improved and extended the following five points. (1) On JENDL-3.1, the fission spectra of principal fissible materials had been calculated by the Modland-Nix model which the neutron emissions of fragments were calculated under the approximation of the constant inverse process cross section. In the paper, the spectra were calculated by the use of the inverse process cross section depend on the energy obtained by the calculation of the optical model. The result showed the increase of low energy components and the softening effect of spectra (2) On JENDL-3.1, the all fission processes were assumed to undergo (n,f) reaction. In the paper, they were calculated by the multi-chance fission such as (n, n'f), (n, 2nf) and (n, 3nf) etc. Softening of the spectra (En > 6 MeV) was obtained by this method. (3) The level density parameter (LDP) has been assumed as a = A/C in either case of light fragment (LF) and heavy fragment (HF) in the original Madland-Nix model. But we used LDP based on the Ignatyuk model under consideration of the shell effects of nuclear fragments, hence the neutron spectra of heavy fragments were hardening. (4) Nuclear temperature of both fragments had been assumed to be the same at original model, but now R T = Tm/TmH was derived to calculate them. The ratio of middle/both side components of spectra was changed. (5) Unknown neutron fission spectra of minor actinide were able to the assumed on the basis of Moriyama-Ohnishi model. (S.Y.)
A new method to evaluate neutron spectra for bnct
International Nuclear Information System (INIS)
Martin Hernandez, Guido
2001-01-01
This paper deals with the development of a method to evaluate neutron spectra for BNCT. Physical dose deposition calculations for different neutron energies, ranging from thermal to fast, were performed. A matrix, containing dose for each energy and position in the beam center line was obtained. MCNP 4B and Snyder's head model were used. A simple computer code containing the matrix calculates the dose for each point in the beam center line depending on the input energy spectrum to be evaluated. The output of this program is the dose distribution in the brain and the dose gain, that is the ratio between dose to tumor and maximum dose to healthy tissue maximum
Evaluation of double differential yield as used for representation of neutron spectra
International Nuclear Information System (INIS)
Solieman, A.H.M.; Comsan, M.N.H.
2002-01-01
The neutron intensity for TOF spectra representation has, until now, only been expressed in terms of double differential yield; number of neutrons per unit charge per unit solid angle per unit neutron energy interval (i.e. neutron intensity at a given resolving power). For accelerator-based neutron sources, the double differential yield - in terms of neutron energy interval - is found to be affected by the kinematics of the neutron producing reaction, to produce intensity irrelevant spectra. The results affect not only the applications that depend on relative neutron intensities, but also the applications that depend on the neutron intensity-weighted integration of the neutron spectra (e.g. neutron average energy calculation, and dose calculation using kerma factors). Other definition of the double differential yield - in terms of projectile energy loss - is suggested to avoid the drawbacks of the old definition. The neutron spectra that are driven using the two definitions are discussed
SLAROM, Neutron Flux Distribution and Spectra in Lattice Cell
International Nuclear Information System (INIS)
Nakagawa, M.; Tsuchihashi, K.
2002-01-01
1 - Description of program or function: SLAROM solves the neutron integral transport equations to determine flux distribution and spectra in a lattice and calculates cell averaged effective cross sections. 2 - Method of solution: Collision probability method for cell calculation and 1D diffusion for core calculation. 3 - Restrictions on the complexity of the problem: Variable dimensions are used throughout the program so that computer core requirements depend on a variety of program parameters
The activation method for determining neutron spectra and fluences
International Nuclear Information System (INIS)
Hogel, J.; Vespalec, R.
1980-01-01
3 mm thick foils of 4 and 17 mm in diameter were used for measurements. NaI scintillation detectors 45 mm in diameter by 50 mm thick and 40 mm in diameter by 1 mm thick, and a Ge-Li spectrometer of 53 cm 3 in volume were used for gamma detection. A photopeak or a certain part of the integral spectrum was measured for each radionuclide. Computer code PIKAR was applied in automatic calculation of a simple gamma spectrum obtained using the semiconductor spectrometer. The FACT code was used for calculating foil activity. Codes SAND II and RFSP were used for neutron spectra unfolding. Ge-Li detector spectrometry was used for determining neutron fluence. Code FLUE was used for determining the mean value of neutron flux density and fluence. (J.P.)
Neutron energy spectra calculations in the low power research reactor
International Nuclear Information System (INIS)
Omar, H.; Khattab, K.; Ghazi, N.
2011-01-01
The neutron energy spectra have been calculated in the fuel region, inner and outer irradiation sites of the zero power research reactor using the MCNP-4C code and the combination of the WIMS-D/4 transport code for generation of group constants and the three-dimensional CITATION diffusion code for core analysis calculations. The neutron energy spectrum has been divided into three regions and compared with the proposed empirical correlations. The calculated thermal and fast neutron fluxes in the low power research reactor MNSR inner and outer irradiation sites have been compared with the measured results. Better agreements have been noticed between the calculated and measured results using the MCNP code than those obtained by the CITATION code. (author)
Activation method for measuring the neutron spectra parameters. Computer software
International Nuclear Information System (INIS)
Efimov, B.V.; Ionov, V.S.; Konyaev, S.I.; Marin, S.V.
2005-01-01
The description of mathematical statement of a task for definition the spectral characteristics of neutron fields with use developed in RRC KI unified activation detectors (UKD) is resulted. The method of processing of results offered by authors activation measurements and calculation of the parameters used for an estimation of the neutron spectra characteristics is discussed. Features of processing of the experimental data received at measurements of activation with using UKD are considered. Activation detectors UKD contain a little bit specially the picked up isotopes giving at irradiation peaks scale of activity in the common spectrum scale of activity. Computing processing of results of the measurements is applied on definition of spectrum parameters for nuclear reactor installations with thermal and close to such power spectrum of neutrons. The example of the data processing, the measurements received at carrying out at RRC KI research reactor F-1 is resulted [ru
Eigenvalue-dependent neutron energy spectra: Definitions, analyses, and applications
International Nuclear Information System (INIS)
Cacuci, D.G.; Ronen, Y.; Shayer, Z.; Wagschal, J.J.; Yeivin, Y.
1982-01-01
A general qualitative analysis of spectral effects that arise from solving the kappa-, α-, γ-, and sigma-eigenvalue formulations of the neutron transport equation for nuclear systems that deviate (to first order) from criticality is presented. Hierarchies of neutron spectra softness are established and expressed concisely in terms of the newly introduced spatialdependent local spectral indices for the core and for the reflector. It is shown that each hierarchy is preserved, regardless of the nature of the specific physical mechanism that cause the system to deviate from criticality. Qualitative conclusions regarding the general behavior of the spectrum-dependent integral spectral indices and ICRs corresponding to the kappa-, α-, γ-, and sigma-eigenvalue formalisms are also presented. By defining spectral indices separately for the core and for the reflector, it is possible to account for the characteristics of neutron spectra in both the core and the reflector. The distinctions between the spectra in the core and in the reflector could not have been accounted for by using a single type of spectral index (e.g., a spectral index for the entire system or a spectral index solely for the core)
International Nuclear Information System (INIS)
Milosevic, M.
1979-01-01
One-dimensional variational method for cylindrical configuration was applied for calculating group constants, together with effects of elastic slowing down, anisotropic elastic scattering, inelastic scattering, heterogeneous resonance absorption with the aim to include the presence of a number of different isotopes and effects of neutron leakage from the reactor core. Neutron flux shape P 3 and adjoint function are proposed in order to enable calculation of smaller size reactors and inclusion of heterogeneity effects by cell calculations. Microscopic multigroup constants were prepared based on the UKNDL data library. Analytical-numerical approach was applied for solving the equations of the P 3 approximation to obtain neutron flux moments and adjoint functions
Influence of cross-section structure on unfolded neutron spectra
International Nuclear Information System (INIS)
Ertek, C.; Vlasov, M.F.; Cross, B.; Smith, P.M.
1979-01-01
The influence of cross-section structure on neutron spectra unfolded by multiple foil activation technique, SAND-II case, has been studied. For three reactions with evident structure in neutron cross-section above threshold: 27Al(n,α)24Na, 31P(n,p)31Si and 32S(n,p)32P, two remarkably different sets of evaluated data were selected from the available evaluations; one set of data was ''smooth'', the structure having been averaged over by a smooth curve; the other set was ''sharp'' with structure given in detail. These data were used in unfolding procedure together with other reactions, the same in both cases (as well as input spectra and measured reaction rates). It was found that during unfolding calculations less iteration steps were needed to unfold the neutron flux spectrum with the set of ''sharp'' data. In case of ''smooth'' data it was difficult to obtain an agreement between measured and calculated activity values even by increasing the number of iteration steps. Contrary to expectations, considerable deformation of unfolded neutron flux spectrum has been observed in the case of the ''smooth'' data set. (author)
Measurements and calculations of neutron spectra and neutron dose distribution in human phantoms
International Nuclear Information System (INIS)
Palfalvi, J.
1984-11-01
The measurement and calculation of the radiation field around and in a phantom, with regard to the neutron component and the contaminating gamma radiation, are essential for radiation protection and radiotherapy purposes. The final report includes the development of the simple detector system, automized detector measuring facilities and a computerized evaluating system. The results of the depth dose and neutron spectra experiments and calculations in a human phantom are given
International Nuclear Information System (INIS)
Garner, F.A.; Greenwood, L.R.
1998-01-01
A review is presented of recent insights on the role of transmutation in the development of radiation-induced changes in dimension or radiation-induced changes in physical or mechanical properties. It is shown that, in some materials and some neutron spectra, transmutation can significantly affect or even dominate a given property change process. When the process under study is also sensitive to displacement rate, and especially if it involves radiation-induced segregation and precipitation, it becomes much more difficult to separate the transmutation and displacement rate dependencies. This complicates the application of data derived from 'surrogate' spectra to predictions in other flux-spectra environments. It is also shown in this paper that one must be sensitive to the impact of previously -ignored 'small' variations in neutron spectra within a given reactor. In some materials these small variations have major consequences. (author)
Theoretical and Experimental Analysis of Fast Neutron Spectra
Energy Technology Data Exchange (ETDEWEB)
Van Dam, H.; Kleijn, H. R. [Reactor Instituut, Delft (Netherlands)
1968-04-15
The reactor physics division of the Inter-Academic Reactor Institute at Delft is concentrating its efforts in the field of fast reactor physics on problems of a more fundamental nature. The object of the programme is to determine experimentally a number of microscopic reactor physics parameters such as conversion potentials, fission ratios and Doppler coefficients for simple geometries and material compositions. Because of the extreme importance of knowledge of the neutron spectrum for the interpretation of the results, attention has initially been concentrated on both the measurement and the calculation of fast neutron spectra. The transport of neutrons in absorbing and non-absorbing heavy atom materials is studied by solving the Boltzmann equation. Both isotropic and anisotropic scattering are considered. Anisotropic scattering is treated by the P{sub n}-approximation, while flux-anisotropy is handled with the S{sub N}-method. In the code FAST-DELFT, scattering is treated up to the P{sub 4} component, a further extension of which is useless because of the lack of available cross-section data. By using this method, the effect of scattering anisotropy on the spectrum formation has been studied. In addition the influence of group cross-section inaccuracies was determined. The experimental work has been concentrated on methods to determine in-core spectra. Using home-made proportional counters with gamma-ray discrimination provisions fast neutron spectra have been measured in simple geometries. These experiments were complemented by foil measurements in the lower energy region. The results of this work are presented in this paper. (author)
Neutron spectra and dosimetric features of isotopic neutron sources: a review
International Nuclear Information System (INIS)
Vega C, H. R.; Martinez O, S. A.
2015-10-01
A convenient way to produce neutrons is the isotopic neutron source, where the production is through (α, n), (γ, n), and spontaneous fission reactions. Isotopic neutron sources are small, easy to handle, and have a relative low cost. On the other hand the neutron yield is small and mostly of them produces neutrons with a wide energy distribution. In this work, a review is carried out about the the main features of 24 NaBe, 24 NaD 2 O, 116 InBe, 140 LaBe, 238 PuLi, 239 PuBe, 241 AmB, 241 AmBe, 241 AmF, 241 AmLi, 242 CmBe, 210 PoBe, 226 RaBe, 252 Cf and 252 Cf/D 2 O isotopic neutron source. Also, using Monte Carlo methods, the neutron spectra in 31 energy groups, the neutron mean energy; the Ambient dose equivalent, the Personal dose equivalent and the Effective dose were calculated for these isotopic neutron sources. (Author)
Neutron spectra and dosimetric features of isotopic neutron sources: a review
Energy Technology Data Exchange (ETDEWEB)
Vega C, H. R. [Universidad Autonoma de Zacatecas, Unidad Academica de Estudios Nucleares, Cipres No. 10, Fracc. La Penuela, 98060 Zacatecas, Zac. (Mexico); Martinez O, S. A., E-mail: fermineutron@yahoo.com [Universidad Pedagogica y Tecnologica de Colombia, Grupo de Fisica Nuclear Aplicada y Simulacion, Av. Central del Norte 39-115, 150003 Tunja, Boyaca (Colombia)
2015-10-15
A convenient way to produce neutrons is the isotopic neutron source, where the production is through (α, n), (γ, n), and spontaneous fission reactions. Isotopic neutron sources are small, easy to handle, and have a relative low cost. On the other hand the neutron yield is small and mostly of them produces neutrons with a wide energy distribution. In this work, a review is carried out about the the main features of {sup 24}NaBe, {sup 24}NaD{sub 2}O, {sup 116}InBe, {sup 140}LaBe, {sup 238}PuLi, {sup 239}PuBe, {sup 241}AmB, {sup 241}AmBe, {sup 241}AmF, {sup 241}AmLi, {sup 242}CmBe, {sup 210}PoBe, {sup 226}RaBe, {sup 252}Cf and {sup 252}Cf/D{sub 2}O isotopic neutron source. Also, using Monte Carlo methods, the neutron spectra in 31 energy groups, the neutron mean energy; the Ambient dose equivalent, the Personal dose equivalent and the Effective dose were calculated for these isotopic neutron sources. (Author)
Ogawa, Y; Sagawa, H; Tsujimoto, T
2002-01-01
The highly sensitive cylindrical multi-moderator type neutron spectrometer was constructed for measurement of low level environmental neutrons. This neutron spectrometer was applied for the determination of leakage neutron energy spectra around the Kinki University Reactor. The analysis of the leakage neutron energy spectra was performed by MCNP Monte Carlo code. From the obtained results, the agreement between the MCNP predictions and the experimentally determined values is fairly good, which indicates the MCNP model is correctly simulating the UTR-KINKI.
Neutron spectra of /sup 242/Cm-Be and /sup 244/Cm-Be neutron sources
Energy Technology Data Exchange (ETDEWEB)
Kumar, A; Nagarajan, P S [Bhabha Atomic Research Centre, Bombay (India). Div. of Radiation Protection
1977-02-15
Neutron spectra of /sup 242/Cm-Be(..cap alpha..,n) and /sup 244/Cm-Be(..cap alpha..,n) sources have been calculated including the spontaneous fission contribution which is negligible for /sup 242/Cm and amounts to about 4% for /sup 244/Cm. The agreement of the present work with experimental results is poor.
Gaganov, V. V.
2017-12-01
The correctness of calculations performed with the SRIANG code for modeling the spectra of DT neutrons is estimated by comparing the obtained spectra to the results of calculations carried out with five different codes based on the Monte Carlo method.
Neutron and gamma-ray spectra of 239PuBe and 241AmBe
International Nuclear Information System (INIS)
Vega-Carrillo, H.R.; Manzanares-Acuna, Eduardo; Becerra-Ferreiro, A.M.; Carrillo-Nunez, Aureliano
2002-01-01
Neutron and gamma-ray spectra of 239 PuBe and 241 AmBe were measured and their dosimetric features were calculated. Neutron spectra were measured using a multisphere neutron spectrometer with a 6 LiI(Eu) scintillator. The 239 PuBe neutron spectrum was measured in an open environment, while the 241 AmBe neutron spectrum was measured in a closed environment. Gamma-ray spectra were measured using a NaI(Tl) scintillator using the same experimental conditions for both sources. The effect of measuring conditions for the 241 AmBe neutron spectrum indicates the presence of epithermal and thermal neutrons. The low-resolution neutron spectra obtained with the multisphere spectrometer allows one to calculate the dosimetric features of neutron sources. At 100 cm both sources produce approximately the same count rate as that of the 4.4 MeV gamma-ray per unit of alpha emitter activity
{sup 235}U(n,F) prompt fission neutron spectra
Energy Technology Data Exchange (ETDEWEB)
Maslov, M.V.; Tetereva, N.A. [Joint Institute of Nuclear and Energy Research, Minsk-Sosny (Belarus); Pronyaev, V.P.; Kagalenko, A.B. [Institute of Physics and Power Engineering, Obninsk (Russian Federation); Capote, R. [International Atomic Energy Agency, Vienna (Austria); Granier, T.; Morillon, B. [CEA, Centre DAM-IIe de France, 91 - Arpajon (France); Hambsch, F.J. [EC-JRC Institute for Reference Materials and Measurements, Geel (Belgium); Sublet, J.C. [CEA Cadarache, 13 - Saint Paul lez Durance (France)
2009-07-01
The longstanding problem of inconsistency of integral thermal data testing and differential prompt fission neutron spectra data (PFNS) is mostly due to rather poor fits of differential PFNS data in major data libraries. The measured database is updated by using modern standards including Manhart's evaluation of the spontaneous fission neutron spectra of {sup 252}Cf(sf). That largely removes the inconsistency of older thermal neutron-induced PFNS measurements with newest data of JRC IRMM by Hambsch et al. (2009). A phenomenological approach, developed by Kornilov et al. (1999), for the first-chance fission and extended for the emissive fission domain by Maslov et al. (2005) is calibrated at E{sub th} to predict both the PFNS average energy
International Nuclear Information System (INIS)
Nagaya, Yasunobu; Okumura, Keisuke; Sakurai, Takeshi; Mori, Takamasa
2017-03-01
In order to realize fast and accurate Monte Carlo simulation of neutron and photon transport problems, two Monte Carlo codes MVP (continuous-energy method) and GMVP (multigroup method) have been developed at Japan Atomic Energy Agency. The codes have adopted a vectorized algorithm and have been developed for vector-type supercomputers. They also support parallel processing with a standard parallelization library MPI and thus a speed-up of Monte Carlo calculations can be achieved on general computing platforms. The first and second versions of the codes were released in 1994 and 2005, respectively. They have been extensively improved and new capabilities have been implemented. The major improvements and new capabilities are as follows: (1) perturbation calculation for effective multiplication factor, (2) exact resonant elastic scattering model, (3) calculation of reactor kinetics parameters, (4) photo-nuclear model, (5) simulation of delayed neutrons, (6) generation of group constants. This report describes the physical model, geometry description method used in the codes, new capabilities and input instructions. (author)
International Nuclear Information System (INIS)
Nagaya, Yasunobu; Okumura, Keisuke; Sakurai, Takeshi; Mori, Takamasa
2017-03-01
In order to realize fast and accurate Monte Carlo simulation of neutron and photon transport problems, two Monte Carlo codes MVP (continuous-energy method) and GMVP (multigroup method) have been developed at Japan Atomic Energy Agency. The codes have adopted a vectorized algorithm and have been developed for vector-type supercomputers. They also support parallel processing with a standard parallelization library MPI and thus a speed-up of Monte Carlo calculations can be achieved on general computing platforms. The first and second versions of the codes were released in 1994 and 2005, respectively. They have been extensively improved and new capabilities have been implemented. The major improvements and new capabilities are as follows: (1) perturbation calculation for effective multiplication factor, (2) exact resonant elastic scattering model, (3) calculation of reactor kinetics parameters, (4) photo-nuclear model, (5) simulation of delayed neutrons, (6) generation of group constants. This report describes the physical model, geometry description method used in the codes, new capabilities and input instructions. (author)
Measurement of neutron spectra for photonuclear reaction with linearly polarized photons
Directory of Open Access Journals (Sweden)
Kirihara Yoichi
2017-01-01
Full Text Available Spectra of neutrons produced by a photonuclear reaction from a 197Au target were measured using 16.95 MeV linearly and circularly polarized photon beams at NewSUBARU-BL01 using a time-of-flight method. The difference in the neutron spectra between the cases of a linearly and circularly polarized photon was measured. The difference in the neutron yield increased with the neutron energy and was approximately threefold at the maximum neutron energy. In a direction perpendicular to that of the linear polarization, the neutron yields decreased as the neutron energy increased.
Program SITHA. New version of the multigroup system of the neutron cross section GR175-V1
International Nuclear Information System (INIS)
Daniehl', A.V.; Perov, V.Yu.; Sokol, E.A.
1991-01-01
Structure of the system of the group neutron constants with band description of the resonance field and program system is described. Results of the testing calculations, made by code SITHA, for number of integral experiments devoted to measurements of the neutron flux from H 2 O,C,N,O and Al spherical targets are discussed. 13 refs.; 8 figs.; 1 tab
Energy Technology Data Exchange (ETDEWEB)
Burns, Kimberly A. [Georgia Inst. of Technology, Atlanta, GA (United States)
2009-08-01
The accurate and efficient simulation of coupled neutron-photon problems is necessary for several important radiation detection applications. Examples include the detection of nuclear threats concealed in cargo containers and prompt gamma neutron activation analysis for nondestructive determination of elemental composition of unknown samples.
International Nuclear Information System (INIS)
van der Hagen, T.H.J.J.; Hoogenboom, J.E.; van Dam, H.
1992-01-01
This paper reports on the sensitivity of a neutron detector to parametric fluctuations in the core of a reactor which depends on the position and the frequency of the perturbation. The basic neutron diffusion model for the calculation of this so-called field of view (FOV) of the detector is extended with respect to the dimensionality of the problem and the number of energy groups involved. The physical meaning of the FOV concept is illustrated by means of some simple examples, which can be handled analytically. The possibility of calculating the FOV by a conventional neutron diffusion code is demonstrated. In that case, the calculation in n neutron energy groups leads to 2n modified neutron diffusion equations
Prompt gamma-based neutron dosimetry for Am-Be and other workplace neutron spectra
International Nuclear Information System (INIS)
Udupi, Ashwini; Panikkath, Priyada; Sarkar, P.K.
2016-01-01
A new field-deployable technique for estimating the neutron ambient dose equivalent H*(10) by using the measured prompt gamma intensities emitted from borated high-density polyethylene (BHDPE) and the combination of normal HDPE and BHDPE with different configurations have been evaluated in this work. Monte Carlo simulations using the FLUKA code has been employed to calculate the responses from the prompt gammas emitted due to the monoenergetic neutrons interacting with boron, hydrogen, and carbon nuclei. A suitable linear combination of these prompt gamma responses (dose conversion coefficient (DCC)-estimated) is generated to approximate the International Commission on Radiological Protection provided DCC using the cross-entropy minimization technique. In addition, the shape and configurations of the HDPE and BHDPE combined system are optimized using the FLUKA code simulation results. The proposed method is validated experimentally, as well as theoretically, using different workplace neutron spectra with a satisfactory outcome. (author)
Neutron spectra unfolding with maximum entropy and maximum likelihood
International Nuclear Information System (INIS)
Itoh, Shikoh; Tsunoda, Toshiharu
1989-01-01
A new unfolding theory has been established on the basis of the maximum entropy principle and the maximum likelihood method. This theory correctly embodies the Poisson statistics of neutron detection, and always brings a positive solution over the whole energy range. Moreover, the theory unifies both problems of overdetermined and of underdetermined. For the latter, the ambiguity in assigning a prior probability, i.e. the initial guess in the Bayesian sense, has become extinct by virtue of the principle. An approximate expression of the covariance matrix for the resultant spectra is also presented. An efficient algorithm to solve the nonlinear system, which appears in the present study, has been established. Results of computer simulation showed the effectiveness of the present theory. (author)
DANTE, Activation Analysis Neutron Spectra Unfolding by Covariance Matrix Method
International Nuclear Information System (INIS)
Petilli, M.
1981-01-01
1 - Description of problem or function: The program evaluates activation measurements of reactor neutron spectra and unfolds the results for dosimetry purposes. Different evaluation options are foreseen: absolute or relative fluxes and different iteration algorithms. 2 - Method of solution: A least-square fit method is used. A correlation between available data and their uncertainties has been introduced by means of flux and activity variance-covariance matrices. Cross sections are assumed to be constant, i.e. with variance-covariance matrix equal to zero. The Lagrange multipliers method has been used for calculating the solution. 3 - Restrictions on the complexity of the problem: 9 activation experiments can be analyzed. 75 energy groups are accepted
Measurement of thermal neutron spectra using LINAC in Japan Atomic Energy Research Institute (JAERI)
International Nuclear Information System (INIS)
Akino, Fujiyoshi
1982-01-01
The exact grasp of thermal neutron spectra in a core region is very important for obtaining accurate thermal neutron group constants in the calculation for the nuclear design of a reactor core. For the accurate grasp of thermal neutron spectra, the capability of thermal neutron spectra to describe the moderator cross-sections for thermal neutron scattering is a key factor. Accordingly, 0 deg angular thermal neutron spectra were measured by the time of flight (TOF) method using the JAERI LINAC as a pulsed neutron source, for light water system added with Cd and In, high temperature graphite system added with boron, and light water-natural uranium heterogeneous multiplication system among the reactor moderators of light water or graphite systems. First, the equations to give the time of flight and neutron flux by TOF method were analyzed, and several corrections were investigated, such as those for detector efficiency, background, the transmission coefficient of air and the Al window of a flight tube, mean emission time of neutrons, and the distortion effect of re-entrant hole on thermal neutron spectra. Then, the experimental system, results and calculation were reported for the experiments on the above three moderator systems. Finally, the measurement of fast neutron spectra in natural uranium system and that of the efficiency of a 6 Li glass scintillator detector are described. (Wakatsuki, Y.)
International Nuclear Information System (INIS)
Nagaya, Yasunobu; Okumura, Keisuke; Mori, Takamasa; Nakagawa, Masayuki
2005-06-01
In order to realize fast and accurate Monte Carlo simulation of neutron and photon transport problems, two vectorized Monte Carlo codes MVP and GMVP have been developed at JAERI. MVP is based on the continuous energy model and GMVP is on the multigroup model. Compared with conventional scalar codes, these codes achieve higher computation speed by a factor of 10 or more on vector super-computers. Both codes have sufficient functions for production use by adopting accurate physics model, geometry description capability and variance reduction techniques. The first version of the codes was released in 1994. They have been extensively improved and new functions have been implemented. The major improvements and new functions are (1) capability to treat the scattering model expressed with File 6 of the ENDF-6 format, (2) time-dependent tallies, (3) reaction rate calculation with the pointwise response function, (4) flexible source specification, (5) continuous-energy calculation at arbitrary temperatures, (6) estimation of real variances in eigenvalue problems, (7) point detector and surface crossing estimators, (8) statistical geometry model, (9) function of reactor noise analysis (simulation of the Feynman-α experiment), (10) arbitrary shaped lattice boundary, (11) periodic boundary condition, (12) parallelization with standard libraries (MPI, PVM), (13) supporting many platforms, etc. This report describes the physical model, geometry description method used in the codes, new functions and how to use them. (author)
International Nuclear Information System (INIS)
Kim, Jung Do; Gil, Choong Sup.
1997-03-01
The KAFAX-F22 was developed from JEF-2.2, which is a MATXS format, multigroup library of fast reactor. The KAFAX-F22 has 80 and 24 energy group structures for neutron and photon, respectively. It includes 89 nuclide data processed by NJOY94.38. The TRANSX/TWODANT system was used for benchmark calculations of fast reactor and one- and two-dimensional calculations of ONEDANT and TWODANT were carried out with 80 group, P 3 S 16 and with 25 group, P 3 S 8 , respectively. The average values of multiplication factors are 0.99652 for MOX cores, 1.00538 for uranium cores and 1.00032 for total cores. Various central reaction rate ratios also give good agreements with the experimental values considering experimental uncertainties except for VERA-11A, VERA-1B, ZPR-6-7 and ZPR-6-6A cores of which experimental values seem to involve some problems. (author). 13 refs., 18 tabs., 2 figs
On hard X-ray spectra of accreting neutron stars
International Nuclear Information System (INIS)
Zheleznyakov, V.V.
1982-01-01
Formation of the spectra of X-ray pulsars and gamma bursters is investigated. Interpretation of a hard X-ray spectrum of pulsars containing cyclotron lines is feasible on the basis of an isothermal model of a polar spot heated due to acccretion to a neutron star. It has been ascertained that in the regions responsible for the formation of continuum radiation and lines the mode polarization is determined by a magnetized vacuum rather than by a plasma. Bearing this in mind, the influence of the magnetic field of a star on the wide wings of the cyclotron line and on its depth is discussed. The part played by the accreting column in the case of strong accretion (approx. equal to 10 19 el cm -3 ) needed for long sustaining of the high level of X-rays from a neutron star-pulsar is studied. There occur the gaps in spectrum at frequencies close to the electron gyro-frequency and its harmonics due to the screening of the hot spot by the opaque gyro-resonant layer located within the accreting column. These gaps ensure the formation of cyclotron lines in absorption irrespective of the presence of such lines in the X-ray spectrum of a polar hot spot. (orig./WL)
International Nuclear Information System (INIS)
Kroc, T.K.
2009-01-01
No fast neutron therapy facility has been built with optimized beam quality based on a thorough understanding of the neutron spectrum and its resulting biological effectiveness. A study has been initiated to provide the information necessary for such an optimization. Monte Carlo studies will be used to simulate neutron energy spectra and LET spectra. These studies will be bench-marked with data taken at existing fast neutron therapy facilities. Results will also be compared with radiobiological studies to further support beam quality ptimization. These simulations, anchored by this data, will then be used to determine what parameters might be optimized to take full advantage of the unique LET properties of fast neutron beams. This paper will present preliminary work in generating energy and LET spectra for the Fermilab fast neutron therapy facility.
Influence of Neutron Spectra Unfolding Method on Fast Neutron Dose Determination
International Nuclear Information System (INIS)
Marinkovic, P.
1991-01-01
Full text: Accuracy of knowing the fast neutron spectra has great influence on equivalent dose determination. In usual fast neutron spectrum measurements with scintillation detectors based on proton recoil, the main difficulty is confidence of unfolding method. In former ones variance of obtained result is usually great and negative values are possible too, which does means that we don't now exactly is obtained neutron spectrum real one. The new unfolding method based on Shanon's information theory, which gives non-negative spectrum and relative low variance, is obtained and appropriate numerical code for application in fast neutron spectrometry based on proton recoil is realized. In this method principle of maximum entropy and maximum likelihood are used together. Unknown group density distribution functions, which are considered as desired normalized mean neutron group flux, are constl u cted using only constrain of knowing mean value. Obtained distributions are consistent to available information (counts in NCA from proton recoil), while being maximally noncommittal with respect to all other unknown circumstances. For maximum likelihood principle, distribution functions around mean value of counts in the channels of MCA are taken to be Gauss function shape. Optimal non-negative solution is searched by means of Lagrange parameter method. Nonlinear system of equations, is solved using gradient and Newton iterative algorithm. Error covariance matrix is obtained too. (author)
MC^{2}-3: Multigroup Cross Section Generation Code for Fast Reactor Analysis
Energy Technology Data Exchange (ETDEWEB)
Lee, C. H. [Argonne National Lab. (ANL), Argonne, IL (United States); Yang, W. S. [Argonne National Lab. (ANL), Argonne, IL (United States)
2013-11-08
The MC^{2}-3 code is a Multigroup Cross section generation Code for fast reactor analysis, developed by improving the resonance self-shielding and spectrum calculation methods of MC^{2}-2 and integrating the one-dimensional cell calculation capabilities of SDX. The code solves the consistent P1 multigroup transport equation using basic neutron data from ENDF/B data files to determine the fundamental mode spectra for use in generating multigroup neutron cross sections. A homogeneous medium or a heterogeneous slab or cylindrical unit cell problem is solved in ultrafine (~2000) or hyperfine (~400,000) group levels. In the resolved resonance range, pointwise cross sections are reconstructed with Doppler broadening at specified isotopic temperatures. The pointwise cross sections are directly used in the hyperfine group calculation whereas for the ultrafine group calculation, self-shielded cross sections are prepared by numerical integration of the pointwise cross sections based upon the narrow resonance approximation. For both the hyperfine and ultrafine group calculations, unresolved resonances are self-shielded using the analytic resonance integral method. The ultrafine group calculation can also be performed for two-dimensional whole-core problems to generate region-dependent broad-group cross sections. Multigroup cross sections are written in the ISOTXS format for a user-specified group structure. The code is executable on UNIX, Linux, and PC Windows systems, and its library includes all isotopes of the ENDF/BVII. 0 data.
Prompt fission neutron spectra of n + 235U above the (n, nf) fission threshold
International Nuclear Information System (INIS)
Shu Nengchuan; Chen Yongjing; Liu Tingjin; Jia Min
2015-01-01
Calculations of prompt fission neutron spectra (PFNS) from the 235 U(n, f) reaction were performed with a semi-empirical method for En = 7.0 and 14.7 MeV neutron energies. The total PFNS were obtained as a superposition of (n, xnf) pre-fission neutron spectra and post-fission spectra of neutrons which were evaporated from fission fragments, and these two kinds of spectra were taken as an expression of the evaporation spectrum. The contributions of (n, xnf) fission neutron spectra on the calculated PFNS were discussed. The results show that emission of one or two neutrons in the (n, nf) or (n, 2nf) reactions influences the PFNS shape, and the neutron spectra of the (n, xnf) fission-channel are soft compared with the neutron spectra of the (n, f) fission channel. In addition, analysis of the multiple-chance fission component showed that second-chance fission dominates the PFNS with an incident neutron energy of 14.7 MeV whereas first-chance fission dominates the 7 MeV case. (authors)
The Dynamic Method for Time-of-Flight Measurement of Thermal Neutron Spectra from Pulsed Sources
International Nuclear Information System (INIS)
Pepelyshev, Yu.N.; Tulaev, A.B.; Bobrakov, V.F.
1994-01-01
The time-of-flight method for a measurement of thermal neutron spectra in the pulsed neutron sources with high efficiency of neutron registration, more than 10 5 times higher in comparison with traditional one, is described. The main problems connected with the electric current technique for time-of-flight spectra measurement are examined. The methodical errors, problems of a special neutron detector design and other questions are discussed. Some experimental results, spectra from surfaces of the water and solid methane moderators, obtained in the pulsed reactor IBR-2 (Dubna, Russia) are presented. 4 refs., 5 figs
Statistical theory for calculating energy spectra of β-delayed neutrons
International Nuclear Information System (INIS)
Kawano, Toshihiko; Moeller, Peter; Wilson, William B.
2008-01-01
Theoretical β-delayed neutron spectra are calculated based on the Quasi-particle Random Phase Approximation (QRPA) and the Hauser-Feshbach statistical model. Neutron emissions from an excited daughter nucleus after β-decay to the granddaughter residual are more accurately calculated than previous evaluations, including all the microscopic nuclear structure information, such as a Gamow-Teller strength distribution and discrete states in the granddaughter. The calculated delayed-neutron spectra reasonably agree with those evaluations in the ENDF decay library, which are based on experimental data. The model was adopted to generate the delayed-neutron spectra for all 271 precursors. (authors)
RDANN a new methodology to solve the neutron spectra unfolding problem
International Nuclear Information System (INIS)
Ortiz R, J.M.; Martinez B, M.R.; Vega C, H.R.
2006-01-01
The optimization processes known as Taguchi method and DOE methodology are applied to the design, training and testing of Artificial Neural Networks in the neutron spectrometry field, which offer potential benefits in the evaluation of the behavior of the net as well as the ability to examine the interaction of the weights and neurons inside the same one. In this work, the Robust Design of Artificial Neural Networks methodology is used to solve the neutron spectra unfolding problem, designing, training and testing an ANN using a set of 187 neutron spectra compiled by the International Atomic Energy Agency, to obtain the better neutron spectra unfolded from the Bonner spheres spectrometer's count rates. (Author)
Neutron spectra determination methods using the measured reaction rates in SAPIS
International Nuclear Information System (INIS)
Bondars, Kh.Ya.; Lapenas, A.A.
1980-01-01
Mathematical basis of algorithms is given for methods of neutron spectra restoration in accordance with the measured reaction rates of the activation detectors included into the information-determination system SAIPS aimed at generalization of the most popular home and foreign neutron spectra determination methods as well as the establishment of their mutual relations. The following neutron spectra determination methods are described: SAND-II, CRYSTAL BALL, WINDOWS, SPECTRA, RESP, JUL; polynominal and directed divergence methods. The algorithms have been realized on the ES computer
Energy spectra of neutrons accompanying the emission fission of 238U
International Nuclear Information System (INIS)
Smirenkin, G.N.; Lovchikova, G.N.; Trufanov, A.M.; Svirin, M.I.; Polyakov, A.V.; Vinogradov, V.A.; Dmitriev, V.D.; Boykov, G.S.
1996-01-01
The spectra of fission neutrons emitted from 238U are measured for the first time by the time-of-flight method at incident-neutron energies of 16.0 and 17.7 MeV. Analysis of the neutron spectra shows that experimental results at incident-neutron energies of 14.7, 16.0, and 17.7 MeV (above the threshold of chance fission) differ significantly from those obtained at a neutron energy of 2.9 MeV (below the threshold of chance fission). Owing to the prefission emission of neutrons, the observed spectra of neutrons from emission fission exhibit a characteristic growth of the neutron yield in both hard and soft sections of the spectrum of secondary neutrons. This growth manifests itself as a step in the first case and as a rise in the second case, where it results in a noticeable excess of neutrons over the statistical-model predictions for E<2 MeV. The first feature in the spectra of neutrons from emission fission can be associated with the nonequilibrium decay of an excited fissile nucleus. On the contrary, the origin of the second feature has yet to be clarified. Additional measurements of angular distributions of secondary neutrons may prove helpful in this respect
Time-of-flight spectrometer for the measurement of gamma correlated neutron spectra
International Nuclear Information System (INIS)
Andriashin, A.V.; Devkin, B.V.; Lychagin, A.A.; Minko, J.V.; Mironov, A.N.; Nesterenko, V.S.; Sztaricskai, T.; Petoe, G.; Vasvary, L.
1986-01-01
A time-of-flight spectrometer for the measurement of gamma correlated neutron spectra from (n,xnγ) reactions is described. The operation and the main parameters are discussed. The resolution in the neutron channel is 2.2 ns/m at the 150 keV neutron energy threshold. A simultaneous measurement of the time-of-flight and amplitude distributions makes it possible to study gamma correlated neutron spectra as well as the prompt gamma spectra in coincidence with selected energy neutrons. In order to test the spectrometer, measurements of the neutron spectrum in coincidence with the 846 keV gamma line of 56 Fe were carried out at an incident neutron energy of 14.1 MeV. (Auth.)
Time-of-flight spectrometer for the measurement of gamma correlated neutron spectra
International Nuclear Information System (INIS)
Andryashin, A.V.; Devlein, B.V.; Lychagin, A.A.; Minko, Y.V.; Mironov, A.N.; Nesterenko, V.S.
1986-01-01
A time-of-flight spectrometer for the measurement of gamma correlated neutron spectra form (n,xnγ) reactions is described. The operation and the main parameters are discussed. The resolution in the neutron channel is 2.2 ns/m at the 150 keV neutron energy threshold. A simultaneous measurement of the time-of-flight and amplitude distributions makes it possible to study gamma correlated neutron spectra as well as the prompt gamma spectra in coincidence with selected energy neutrons. In order to test the spectrometer, measurements of the neutron spectrum in coincidence with the 846 keV gamma line of 56 Fe were carried out at an incident neutron energy of 14.1 MeV. (author). 3 figs., 6 refs
International Nuclear Information System (INIS)
Klix, A.; Batistoni, P.; Boettger, R.; Lebrun-Grandie, D.; Fischer, U.; Henniger, J.; Leichtle, D.; Villari, R.
2010-01-01
Fast neutron and gamma-ray flux spectra and time-of-arrival spectra of slow neutrons have been measured in a neutronics mock-up of the European Helium-Cooled Lithium-Lead Test Blanket Module with the aim to validate nuclear cross-section data. The mock-up was irradiated with fusion peak neutrons from the DT neutron generator of the Technical University of Dresden. A well characterized cylindrical NE-213 scintillator was inserted into two positions in the LiPb/EUROFER assembly. Pulse height spectra from neutrons and gamma-rays were recorded from the NE-213 output. The spectra were then unfolded with experimentally obtained response matrices of the NE-213 detector. Time-of-arrival spectra of slow neutrons were measured with a 3 He counter placed in the mock-up, and the neutron generator was operated in pulsed mode. Monte Carlo calculations using the MCNP code and nuclear cross-section data from the JEFF-3.1.1 and FENDL-2.1 libraries were performed and the results are compared with the experimental results. A good agreement of measurement and calculation was found with some deviations in certain energy intervals.
Targeted Modification of Neutron Energy Spectra for National Security Applications
Bevins, James Edward
with the current sample doping approach and applied neutron spectral shaping to design an ETA that can create realistic synthetic fission and activation products and improve technical nuclear forensics outcomes. However, the ETA presented in this research represents more than a stand alone point design with a limited scope and application. It is proof of a concept and the product of a unique capability that has a wide range of potential applications. This research demonstrates that the concept of neutron spectral shaping can be used to engineer complex neutron spectra within the confines of physics. There are many possible applications that could benefit from the ability to generate custom energy neutron spectra that fall outside of current sources and methods. The ETA is the product of a general-purpose optimization algorithm, Gnowee, and design framework, Coeus, which enables the use of Gnowee for complex nuclear design problems. Through Gnowee and Coeus, new ETA neutronics designs can be generated in days, not months or years, with a drastic reduction in the research effort required to do so. (Abstract shortened by ProQuest.).
International Nuclear Information System (INIS)
Capote Noy, R.
2013-09-01
A summary is given of the Second Research Coordination Meeting on Prompt Fission Neutron Spectra of Actinides. Experimental data and modelling methods on prompt fission neutron spectra were reviewed. Extensive technical discussions held on theoretical methods to calculate prompt fission spectra. Detailed coordinated research proposals have been agreed. Summary reports of selected technical presentations at the meeting are given. The resulting work plan of the Coordinated Research Programme is summarized, along with actions and deadlines. (author)
Generating and verification of ACE-multigroup library for MCNP
International Nuclear Information System (INIS)
Chen Chaobin; Hu Zehua; Chen Yixue; Wu Jun; Yang Shouhai
2012-01-01
The Monte Carlo code MCNP can handle multigroup calculations and a sample multigroup set based on ENDF/B-V, MGXSNP, is available for MCNP for coupled neutron-photon transport. However, this library is not suit- able for all problems, and there is a need for users to be able to generate multigroup libraries tailored to their specific applications. For these purposes CSPT (cross section processing tool) is created to generate multigroup library for MCNP from deterministic multigroup cross sections (GENDF or ANISN format at present). Several ACE-multigroup libraries based on ENDF/B-VII.0 converted and verified in this work, we drawn the conclusion that the CSPT code works correctly and the libraries produced are credible. (authors)
Validation of neutron data libraries by backscattered spectra of Pu-Be Neutrons
El-Agib, I
1999-01-01
Elastically backscattered spectra of Pu-Be neutrons have been measured for SiO sub 2 , water, graphite, paraffin oil and Al slabs using a proton recoil spectrometer. The results were compared with the calculated spectra obtained by the three-dimensional Monte-Carlo transport code MCNP-4B and point-wise cross sections from the ENDF/B-V, ENDF/B-VI, JENDL-3.1 and BROND-2 data libraries. The good agreement between the measured and calculated results indicates that this procedure can be used for validation of different data libraries. This simple method renders possible the detection of oxygen, carbon and hydrogen in bulk samples. (author)
International Nuclear Information System (INIS)
Rimpler, A.; Kneschke, H.
1985-01-01
Based on a systematic evaluation of area dose studies at the beginning of the seventies, no individual routine neutron monitoring has been performed at the Rossendorf research reactors. To check this decision, a limited number of persons has been monitored with solid-state nuclear track detectors for several years. The dosemeters were calibrated on the basis of neutron spectra determined at the working places by means of the Bonner sphere method. Intermediate neutrons with a 1/E/sup α/ Fermi distribution were dominating. The fraction of fast neutrons was practically negligible. The obtained spectra, radiation, field quantities and results of individual dose measurements are presented. The dosemeter most appropriate for such neutron fields would be a 12-inch Bonner sphere rem counter. As the mean annual neutron exposure of research workers at the reactor amounted to only 2% of the maximum permissible dose, individual routine monitoring will, also in the future, not be neccessary. (author)
Consultants' meeting on prompt fission neutron spectra of major actinides. Summary report
International Nuclear Information System (INIS)
Capote Noy, R.; Maslov, V.; Bauge, E.; Ohsawa, T.; Vorobyev, A.; Chadwick, M.B.; Oberstedt, S.
2009-01-01
A Consultants' Meeting on 'Prompt Fission Neutron Spectra of Major Actinides' was held at IAEA Headquarters, Vienna, Austria, to discuss the adequacy and quality of the recommended prompt fission neutron spectra to be found in existing nuclear data applications libraries. These prompt fission neutron spectra were judged to be inadequate, and this problem has proved difficult to resolve by means of theoretical modelling. Major adjustments may be required to ensure the validity of such important data. There is a strong requirement for an international effort to explore and resolve these difficulties and recommend prompt fission neutron spectra and uncertainty covariance matrices for the actinides over the neutron energy range from thermal to 20 MeV. Participants also stressed that there would be a strong need for validation of the resulting data against integral critical assembly and dosimetry data. (author)
Portable instrument for measuring neutron energy spectra and neutron dose in a mixed n-γ field
International Nuclear Information System (INIS)
Daniels, C. J.; Silberberg, J. L.
1980-01-01
A portable high-speed neutron spectrometer consists of an organic scintillator, a true zero-crossing pulse shape discriminator, a 1 MHZ conversion-rate multichannel analyzer, an 8-bit microcomputer, and appropriate displays. The device can be used to measure neutron energy spectra and kerma rate in intense n- gamma radiation fields in which the neutron energy is from 5 to 15 MEV
Determination of the fast neutrons spectra by the Elastic scattering method (n, p)
International Nuclear Information System (INIS)
Elizalde D, J.
1973-01-01
This work consists in determining the fast neutron spectra emitted by a Pu-Be isotopic source. The implemented technique is based in the spectrometry (n, p). This consists in making to fall on a fast neutrons beams (polyenergetic) over a thin film of hydrogenated material, detecting the spectra of emitted protons at a fix angle. The polyethylene film and the used solid state detector are inside of a vacuum chamber. The detector is placed at 30 degree with respect to direction of the incident neutrons beam. The protons spectra is stored in a multichannel. the energy is obtained with the prior calibration of the system. The data processing involves the transformation of the protons spectra observed at the falling on neutrons spectra over the film. The energy of the neutrons is related with that of the protons, according to the collision kinematical equations. The cross section of elastic collision of the neutrons with the hydrogen atoms is obtained from literature. Applying these relations to the observed spectra it is obtained the falling on neutron spectra over the film. (Author)
Neutron and gamma dose and spectra measurements on the Little Boy replica
International Nuclear Information System (INIS)
Hoots, S.; Wadsworth, D.
1984-01-01
The radiation-measurement team of the Weapons Engineering Division at Lawrence Livermore National Laboratory (LLNL) measured neutron and gamma dose and spectra on the Little Boy replica at Los Alamos National Laboratory (LANL) in April 1983. This assembly is a replica of the gun-type atomic bomb exploded over Hiroshima in 1945. These measurements support the National Academy of Sciences Program to reassess the radiation doses due to atomic bomb explosions in Japan. Specifically, the following types of information were important: neutron spectra as a function of geometry, gamma to neutron dose ratios out to 1.5 km, and neutron attenuation in the atmosphere. We measured neutron and gamma dose/fission from close-in to a kilometer out, and neutron and gamma spectra at 90 and 30 0 close-in. This paper describes these measurements and the results. 12 references, 13 figures, 5 tables
A high-resolution neutron spectra unfolding method using the Genetic Algorithm technique
Mukherjee, B
2002-01-01
The Bonner sphere spectrometers (BSS) are commonly used to determine the neutron spectra within various nuclear facilities. Sophisticated mathematical tools are used to unfold the neutron energy distribution from the output data of the BSS. This paper highlights a novel high-resolution neutron spectra-unfolding method using the Genetic Algorithm (GA) technique. The GA imitates the biological evolution process prevailing in the nature to solve complex optimisation problems. The GA method was utilised to evaluate the neutron energy distribution, average energy, fluence and equivalent dose rates at important work places of a DIDO class research reactor and a high-energy superconducting heavy ion cyclotron. The spectrometer was calibrated with a sup 2 sup 4 sup 1 Am/Be (alpha,n) neutron standard source. The results of the GA method agreed satisfactorily with the results obtained by using the well-known BUNKI neutron spectra unfolding code.
International Nuclear Information System (INIS)
Zhu, Qingjun; Song, Fengquan; Ren, Jie; Chen, Xueyong; Zhou, Bin
2014-01-01
To further expand the application of an artificial neural network in the field of neutron spectrometry, the criteria for choosing between an artificial neural network and the maximum entropy method for the purpose of unfolding neutron spectra was presented. The counts of the Bonner spheres for IAEA neutron spectra were used as a database, and the artificial neural network and the maximum entropy method were used to unfold neutron spectra; the mean squares of the spectra were defined as the differences between the desired and unfolded spectra. After the information entropy of each spectrum was calculated using information entropy theory, the relationship between the mean squares of the spectra and the information entropy was acquired. Useful information from the information entropy guided the selection of unfolding methods. Due to the importance of the information entropy, the method for predicting the information entropy using the Bonner spheres' counts was established. The criteria based on the information entropy theory can be used to choose between the artificial neural network and the maximum entropy method unfolding methods. The application of an artificial neural network to unfold neutron spectra was expanded. - Highlights: • Two neutron spectra unfolding methods, ANN and MEM, were compared. • The spectrum's entropy offers useful information for selecting unfolding methods. • For the spectrum with low entropy, the ANN was generally better than MEM. • The spectrum's entropy was predicted based on the Bonner spheres' counts
Final report [on solving the multigroup diffusion equations
International Nuclear Information System (INIS)
Birkhoff, G.
1975-01-01
Progress achieved in the development of variational methods for solving the multigroup neutron diffusion equations is described. An appraisal is made of the extent to which improved variational methods could advantageously replace difference methods currently used
Average radiation weighting factors for specific distributed neutron spectra
International Nuclear Information System (INIS)
Ninkovic, M.M.; Raicevic, J.J.
1993-01-01
Spectrum averaged radiation weighting factors for 6 specific neutron fields in the environment of 3 categories of the neutron sources (fission, spontaneous fission and (α,n)) are determined in this paper. Obtained values of these factors are greater 1.5 to 2 times than the corresponding quality factors used for the same purpose until a few years ago. This fact is very important to have in mind in the conversion of the neutron fluence into the neutron dose equivalent. (author)
The dynamic method for time-of-flight measurement of thermal neutron spectra from pulsed sources
International Nuclear Information System (INIS)
Pepyolyshev, Yu.N.; Chuklyaev, S.V.; Tulaev, A.B.; Bobrakov, V.F.
1995-01-01
A time-of-flight method for measurement of thermal neutron spectra in pulsed neutron sources with an efficiency more than 10 5 times higher than the standard method is described. The main problems associated with the electric current technique for time-of-flight spectra measurement are examined. The methodical errors, problems of special neutron detector design and other questions are discussed. Some experimental results for spectra from the surfaces of water and solid methane moderators obtained at the IBR-2 pulsed reactor (Dubna, Russia) are presented. (orig.)
Characterization of materials used for neutron spectra modification
International Nuclear Information System (INIS)
Solieman, A.H.M.; Comsan, M.N.H.; Fahmey, M.A.; Morsy, A.A.
2008-01-01
Monte Carlo Simulation is used to study the thickness-dependent neutron-spectral-modification after transport in different materials. A collection of significant materials is studied, for choosing of potential candidates in the construction and design of accelerator-based neutron irradiation system suitable for Boron Neutron Capture Therapy (BNCT)
Neutron emission spectra of excited 126–140Sn nuclei
International Nuclear Information System (INIS)
Aggarwal, Mamta; Rajasekaran, M.
2004-01-01
We investigate one-neutron and two-neutron emission from 132 Sn and its neighboring isotopes due to thermal excitation. The rotational states of 132 Sn at different temperatures are investigated. The effects of separation energy and thermal excitation energy on neutron emission probability are studied. (author)
Fast neutron spectra unfolding with SAND-11 and maximum likelihoed methods
International Nuclear Information System (INIS)
Bondars, Kh.Ya.; Kamnev, V.A.; Lapenas, A.A.; Troshin, V.S.
1980-01-01
Mutual comparison of the methods SAND-II and maximal likeness for neutron spectra determination are represented. Spectra were restored according to the measures reaction rate of ten activation detectors using the device B-2 of the reactor BR-5 behind two thicknesses of steel-graphite shielding: Z=6.5 cm and Z=42.5 cm. The influence of earlier information on the results of neutron spectra determination was studied. Differential and integral energy dependences of neutron flux density for three initial spectra and two cross section libraries (BGS-1 and ZACRSS) are presented. The both methods yield close differential spectra (discrepancies < 10 %) when identical cross section libraries and reference spectra are used
International Nuclear Information System (INIS)
Woznicki, Z.
1976-05-01
This report presents the AGA two-sweep iterative methods belonging to the family of factorization techniques in their practical application in the HEXAGA-II two-dimensional programme to obtain the numerical solution to the multi-group, time-independent, (real and/or adjoint) neutron diffusion equations for a fine uniform triangular mesh. An arbitrary group scattering model is permitted. The report written for the users provides the description of input and output. The use of HEXAGA-II is illustrated by two sample reactor problems. (orig.) [de
Neutron spectrum adjustment. The role of covariances
International Nuclear Information System (INIS)
Remec, I.
1992-01-01
Neutron spectrum adjustment method is shortly reviewed. Practical example dealing with power reactor pressure vessel exposure rates determination is analysed. Adjusted exposure rates are found only slightly affected by the covariances of measured reaction rates and activation cross sections, while the multigroup spectra covariances were found important. Approximate spectra covariance matrices, as suggested in Astm E944-89, were found useful but care is advised if they are applied in adjustments of spectra at locations without dosimetry. (author) [sl
Neutron spectra in two beam ports of the TRIGA Mark III reactor
International Nuclear Information System (INIS)
Vega C, H. R.; Hernandez D, V. M.; Aguilar, F.; Paredes, L.; Rivera M, T.
2013-10-01
The neutron spectra have been measured in two beam ports, radial and tangential, of the TRIGA Mark III nuclear reactor from the National Institute of Nuclear Research. Measurements were carried out with the core with mixed fuel (Leu 8.5/20 and Flip Heu 8.5/70). Two reactor powers, 5 and 10 W, were used during neutron spectra measurements using a Bonner sphere spectrometer with a 6 Lil(Eu) scintillator and 2, 3, 5, 8, 10 and 12 inches-diameter high density polyethylene spheres. The neutron spectra were unfolded using the NSDUAZ unfolding code; from each spectrum the total neutron flux, the neutron mean energy and the neutron ambient dose equivalent dose were determined. Measured spectra show fission (E≥ 0.1 MeV), epithermal (from 0.4 eV up to 0.1 MeV) and thermal neutrons (E≤ 0.4 eV). For both reactor powers the spectra in the radial beam port have similar features which are different to the neutron spectrum characteristics in the tangential beam port. (Author)
Neutron spectra in two beam ports of the TRIGA Mark III reactor
Energy Technology Data Exchange (ETDEWEB)
Vega C, H. R.; Hernandez D, V. M. [Universidad Autonoma de Zacatecas, Unidad Academica de Estudios Nucleares, Cipres No. 10, Fracc. La Penuela, 98060 Zacatecas (Mexico); Aguilar, F.; Paredes, L. [ININ, Carretera Mexico-Toluca s/n, 52750 Ocoyoacac, Estado de Mexico (Mexico); Rivera M, T., E-mail: fermineutron@yahoo.com [IPN, Centro de Investigacion en Ciencia Aplicada y Tecnologia Avanzada, Unidad Legaria, Av. Legaria 694, 11500 Mexico D. F. (Mexico)
2013-10-15
The neutron spectra have been measured in two beam ports, radial and tangential, of the TRIGA Mark III nuclear reactor from the National Institute of Nuclear Research. Measurements were carried out with the core with mixed fuel (Leu 8.5/20 and Flip Heu 8.5/70). Two reactor powers, 5 and 10 W, were used during neutron spectra measurements using a Bonner sphere spectrometer with a {sup 6}Lil(Eu) scintillator and 2, 3, 5, 8, 10 and 12 inches-diameter high density polyethylene spheres. The neutron spectra were unfolded using the NSDUAZ unfolding code; from each spectrum the total neutron flux, the neutron mean energy and the neutron ambient dose equivalent dose were determined. Measured spectra show fission (E≥ 0.1 MeV), epithermal (from 0.4 eV up to 0.1 MeV) and thermal neutrons (E≤ 0.4 eV). For both reactor powers the spectra in the radial beam port have similar features which are different to the neutron spectrum characteristics in the tangential beam port. (Author)
Neutron energy spectra produced by α-bombardment of light elements in thick targets
International Nuclear Information System (INIS)
Jacobs, G.J.H.
1982-01-01
The aim of the work, presented in this thesis, is to determine energy spectra of neutrons produced by α-particle bombardment of thick targets containing light elements. These spectra are required for nuclear waste management. The set-up of the neutron spectrometer is described, and its calibration discussed. Absolute efficiencies were determined at various neutron energies, using monoenergetic neutrons produced with the Van de Graaff accelerator in pulsed mode. The additional calibration of the neutron spectrometer as proton-recoil spectrometer was carried out primarily for future applications in measurements where no pulsed neutron source is available or the neutron flux density is too low. The basis for an accurate uncertainty analysis is made by the determination of the covariance matrix for the uncertainties in the efficiencies. The determination of the neutron energy spectra from time-of-flight and from proton-recoil measurements is described. A comparison of the results obtained from the two different types of measurements is made. The experimentally determined spectra were compared with spectra calculated from stopping powers and theoretically determined cross sections. These cross sections were calculated from optical model parameters and level parameters using the Hauser-Feshbach formalism. Measurements were carried out on thick targets of silicon, aluminium, magnesium, carbon, boron nitride, calcium fluoride, aluminium oxide, silicon oxide and uranium oxide at four different α-particle energies. (Auth.)
Method of measuring neutron spectra in JMTR exclusively used for irradiation and their evaluation
International Nuclear Information System (INIS)
Sakurai, Kiyoshi
1983-01-01
In the core of the Japan Materials Testing Reactor, about 60 capsules are irradiated. These are the material capsules for irradiating reactor materials, the fuel capsules for irradiating reactor fuel, the RI capsules for producing radioisotopes and so on. In the irradiation experiment using a reactor, the information on the neutron fluence is indispensable, and the neutron fluence in the irradiated specimen part is evaluated with a dosimeter or the nuclear calculation for the core of the JMTR. At the time of irradiating reactor materials, the dosimeter Fe-54 (n,p) Mn-54 is generally used for evaluating the neutron fluence more than 1 MeV. In the case of fuel irradiation, the thermal neutron fluence is evaluated with the dosimeter Co-59 (n,γ) Co-60. It is important to examine in detail neutron spectra by both calculation and experiment in the reactors exclusively used for irradiation such as the JMTR. The neutron irradiation field in the JMTR, neutron spectrum measuring experiment, the neutron flux monitors for standardizing data, the measurement of X-ray and gamma ray, neutron guess spectrum, the compilation of neutron cross section for SAND 2, and the unfolding of neutron spectra are reported. The degree of agreement of the neutron fluence more than 1 MeV by measurement and calculation was +- 10 to 20 %. (Kako, I.)
Use of the response function in the analysis of complex neutron spectra
International Nuclear Information System (INIS)
Kegel, G.H.R.; Ciarcia, C.; Couchell, G.P.; Shao, J.
1974-01-01
Neutron time-of-flight spectra with overlapping peaks must be unfolded to yield contributions of individual neutron groups. This requires an accurate knowledge of the resolution profile of each group. It is also desirable to know the shape of the spectra of neutrons which were scattered more than once in the scatterer, so that corrections for multiple interactions can be made. These resolution profiles and spectra shapes are not readily available. We have developed a series of measures to account for these effects in our work. We monitor the neutron target thickness during target preparation with a separate time-of-flight spectrometer; we measure detector and accelerator time resolutions for different neutron energies using a thin target and we use computer codes to simulate those factors not amenable to direct measurement
Summary report of the consultants' meeting on neutron sources spectra for EXFOR
International Nuclear Information System (INIS)
Simakov, S.P.; Kaeppeler, F.
2011-10-01
The participants highlighted the importance of complementing the averaged cross section data already stored in EXFOR by the incident neutron energy spectra. They shared their experience on measurement and simulation of neutron fields produced at reactors and accelerators over a wide energy range. The source characteristics, format and rules needed for storage in EXFOR were discussed. The participants submitted the numerical information on spectra that will essentially increase the number of 'complete' data sets in EXFOR. The report additionally provides an overview of (i) neutron production cross sections and thick target yields missing from the EXFOR database; (ii) codes for neutron spectra calculations; (iii) informational resources for reactor, radioactive and spallation neutron sources; (iv) codes for spectrum unfolding and (v) EXFOR compilation rules for the Maxwellian averaged cross sections measured for the reactor and astrophysical applications. (author)
Range calculations using multigroup transport methods
International Nuclear Information System (INIS)
Hoffman, T.J.; Robinson, M.T.; Dodds, H.L. Jr.
1979-01-01
Several aspects of radiation damage effects in fusion reactor neutron and ion irradiation environments are amenable to treatment by transport theory methods. In this paper, multigroup transport techniques are developed for the calculation of particle range distributions. These techniques are illustrated by analysis of Au-196 atoms recoiling from (n,2n) reactions with gold. The results of these calculations agree very well with range calculations performed with the atomistic code MARLOWE. Although some detail of the atomistic model is lost in the multigroup transport calculations, the improved computational speed should prove useful in the solution of fusion material design problems
A method for prediction of prompt fission neutron spectra
International Nuclear Information System (INIS)
Grashin, A.F.; Lepeshkin, M.V.
1988-01-01
Three-parameter formula for the prompt-fission-neutron integral spectrum is derived from a thermodynamical model. Two parameters, scission-neutron weight p = 11 % and anisotropy factor for accelerated fragments b = 10 %, are determined from experimental data, the same values being assumed for any type of fission. The thermodynamical theory provides the value of the third parameter, temperature τ, thus prognozing neutron spectrum and average energy with an error about 1 %. (author)
Fast neutron spectra determination by threshold activation detectors using neural networks
International Nuclear Information System (INIS)
Kardan, M.R.; Koohi-Fayegh, R.; Setayeshi, S.; Ghiassi-Nejad, M.
2004-01-01
Neural network method was used for fast neutron spectra unfolding in spectrometry by threshold activation detectors. The input layer of the neural networks consisted of 11 neurons for the specific activities of neutron-induced nuclear reaction products, while the output layers were fast neutron spectra which had been subdivided into 6, 8, 10, 12, 15 and 20 energy bins. Neural network training was performed by 437 fast neutron spectra and corresponding threshold activation detector readings. The trained neural network have been applied for unfolding 50 spectra, which were not in training sets and the results were compared with real spectra and unfolded spectra by SANDII. The best results belong to 10 energy bin spectra. The neural network was also trained by detector readings with 5% uncertainty and the response of the trained neural network to detector readings with 5%, 10%, 15%, 20%, 25% and 50% uncertainty was compared with real spectra. Neural network algorithm, in comparison with other unfolding methods, is very fast and needless to detector response matrix and any prior information about spectra and also the outputs have low sensitivity to uncertainty in the activity measurements. The results show that the neural network algorithm is useful when a fast response is required with reasonable accuracy
Calculation of neutron spectra in the reactor cell of the RA experimental reactor in Vinca
International Nuclear Information System (INIS)
Bosevski, T.; Altiparmakov, D.; Marinkovic, N.
1974-01-01
In the frame of neutron properties of RA experimental reactor the study of energy neutron spectra in the reactor cell are planned. Complex reactor cell geometry, nine cylindrical regions causes high space-energy variations of neutron flux with a significant gradient both in energy and space variables. Treatment of such a complex problem needs adequate methodology which ensures reliable results and control of accuracy. This paper describes in detail the method for calculating group constants based on lattice cell calculation for the need of calculation of reactor core parameters. In 26 group approximation for the energy region from 0 - 10.5 MeV, values of neutron spectra are obtained in 18 space points chosen to describe, with high accuracy, integral reactor cell parameters of primary importance for the reactor core calculation. Obtained space-energy distribution of neutron flux in the reactor cell is up to now unique in the study of neutron properties of Ra reactor [sr
Calculated /alpha/-induced thick target neutron yields and spectra, with comparison to measured data
International Nuclear Information System (INIS)
Wilson, W.B.; Bozoian, M.; Perry, R.T.
1988-01-01
One component of the neutron source associated with the decay of actinide nuclides in many environments is due to the interaction of decay /alpha/ particles in (/alpha/,n) reactions on low Z nuclides. Measurements of (/alpha/,n) thick target neutron yields and associated neutron spectra have been made for only a few combinations of /alpha/ energy and target nuclide or mixtures of actinide and target nuclides. Calculations of thick target neutron yields and spectra with the SOURCES code require /alpha/-energy-dependent cross sections for (/alpha/,n) reactions, as well as branching fractions leading to the energetically possible levels of the product nuclides. A library of these data has been accumulated for target nuclides of Z /le/ 15 using that available from measurements and from recent GNASH code calculations. SOURCES, assuming neutrons to be emitted isotopically in the center-of-mass system, uses libraries of /alpha/ stopping cross sections, (/alpha/,n) reaction cross reactions, product nuclide level branching fractions, and actinide decay /alpha/ spectra to calculate thick target (/alpha/,n) yields and neutron spectra for homogeneous combinations of nuclides. The code also calculates the thick target yield and angle intergrated neutron spectrum produced by /alpha/-particle beams on targets of homogeneous mixtures of nuclides. Illustrative calculated results are given and comparisons are made with measured thick target yields and spectra. 50 refs., 1 fig., 2 tabs
Energy Technology Data Exchange (ETDEWEB)
Ajdacic, V S; Lalovic, B I; Petrovic, B P [Institute of nuclear sciences Boris Kidric, Vinca, Beograd (Yugoslavia)
1963-12-15
The possibility of using the Li{sup 6} semiconductor counter spectrometer for measuring fast neutron spectra inside reactors has been investigated in details and some solutions of the difficulties associated with the high interference of thermal neutrons in well-moderated reactors are suggested and checked experimentally (author)
Neutron leakage spectra from Be, Pb and U spheres at 14 MeV energy
International Nuclear Information System (INIS)
Androsenko, A.A.; Androsenko, P.A.; Devkin, B.V.
1989-01-01
Experimental data on neutron leakage spectra from beryllium, lead and uranium spheres with a central 14 MeV neutron source using a time-of-flight spectrometer have been measured. The data were compared with those calculated with the BLANK code using different nuclear data files. 15 refs, 1 fig., 2 tabs
International Nuclear Information System (INIS)
Sekimoto, Hiroshi
1989-01-01
The tritium production density, kerma heat production density, dose and certain integral values of scalar neutron spectra in bare and graphite-reflected lithium-fluoride piles irradiated with D-T neutrons were evaluated from the pulse height distribution of a miniature NE213 neutron spectrometer with UFO data processing code, and compared with the values calculated with MORSE-CV Monte Carlo code. (author). 8 refs.; 1 fig.; 2 tabs
Inclusive zero-angle neutron spectra at the ISR and OPER-model
International Nuclear Information System (INIS)
Grigoryan, A.A.
1977-01-01
The invlusive zero-angle neutron spectra in pp-collisions measured at the ISR are compared with the OPER-model predictions. OPER-model rather well describes the experimental data. Some features of the spectra behaviour at fixed transverse momentum and large x are considered
Measurement of spectra and neutron fluxes on artificial earth satellites from the Cosmos series
Dudkin, V. Y.; Kovalev, Y. Y.; Novikova, M. R.; Potapov, Y. V.; Skvortsov, S. S.; Smirennyy, L. N.
1975-01-01
In 1966-1967 measurements were carried out at the altitudes of 200 to 400 km to determine the spectra and fluxes of fast neutrons inside the hermetically sealed artificial earth satellites of the Cosmos series. The detectors used were nuclear emulsions of the B9 and BR types and an emulsion of the P9 type, filled with Li and P. Spectra and fluxes of neutrons in the range of energies from thermal energies to 10 MeV are presented. Neutron doses are also estimated.
CHARTB multigroup transport package
International Nuclear Information System (INIS)
Baker, L.
1979-03-01
The physics and numerical implementation of the radiation transport routine used in the CHARTB MHD code are discussed. It is a one-dimensional (Cartesian, cylindrical, and spherical symmetry), multigroup,, diffusion approximation. Tests and applications will be discussed as well
Neutron spectra and H*(10) around and 18 MV Linac by Ann's
Energy Technology Data Exchange (ETDEWEB)
Banuelos F, A.; Valero L, C.; Borja H, C. G.; Hernandez D, V. M.; Vega C, H. R., E-mail: alanb535@hotmail.com [Universidad Autonoma de Zacatecas, Unidad Academica de Estudios Nucleares, Calle Cipres No. 10, Fracc. La Penuela, 98068 Zacatecas (Mexico)
2011-10-15
Neutron spectra and ambient dose equivalent H*(10) were calculated for a radiotherapy room in 16 point-like detectors, 15 located inside the vault room and 1 located outside the bunker. The calculation was carried out using Monte Carlo Methods with the MCNP5 code for a generic radiotherapy room model operating with a 18 MV Linac, obtaining 16 neutron spectra with 47 energy bins, the H*(10) values were calculated from the neutron spectra by the use of the fluence-dose conversion factors. An artificial neural network were designed and trained to determine the neutron H*(10) in 15 different locations inside the vault room from the H*(10) dose calculated for the detector located outside the room, using the calculated dose values as training set, using the scaled conjugated gradient training algorithm. The mean squared error set for the network training was 1E(-14), adjusting the data in 99.992 %. In the treatment hall, as the distance respect to the isocenter is increased, the amount of neutrons and the H*(10) are reduced, neutrons in the high-energy region are shifted to lower region peaking around 0.1 MeV, however the epithermal and thermal neutrons remain constant due to the room-return effect. In the maze the spectra are dominated by epithermal and thermal neutrons that contributes to produce activation and the production of prompt gamma-rays. The results shows the using this artificial intelligence technic as a useful tool for the neutron spectrometry and dosimetry by the simplification on the neutronic fields characterization inside radiotherapy rooms avoiding the use of traditional spectrometric systems. And once the H*(10) doses have been calculated, to take the appropriated actions to reduce or prevent the patient and working staff exposure to this undesirable neutron radiation. (Author)
Neutron spectra and H*(10) around and 18 MV Linac by Ann's
International Nuclear Information System (INIS)
Banuelos F, A.; Valero L, C.; Borja H, C. G.; Hernandez D, V. M.; Vega C, H. R.
2011-10-01
Neutron spectra and ambient dose equivalent H*(10) were calculated for a radiotherapy room in 16 point-like detectors, 15 located inside the vault room and 1 located outside the bunker. The calculation was carried out using Monte Carlo Methods with the MCNP5 code for a generic radiotherapy room model operating with a 18 MV Linac, obtaining 16 neutron spectra with 47 energy bins, the H*(10) values were calculated from the neutron spectra by the use of the fluence-dose conversion factors. An artificial neural network were designed and trained to determine the neutron H*(10) in 15 different locations inside the vault room from the H*(10) dose calculated for the detector located outside the room, using the calculated dose values as training set, using the scaled conjugated gradient training algorithm. The mean squared error set for the network training was 1E(-14), adjusting the data in 99.992 %. In the treatment hall, as the distance respect to the isocenter is increased, the amount of neutrons and the H*(10) are reduced, neutrons in the high-energy region are shifted to lower region peaking around 0.1 MeV, however the epithermal and thermal neutrons remain constant due to the room-return effect. In the maze the spectra are dominated by epithermal and thermal neutrons that contributes to produce activation and the production of prompt gamma-rays. The results shows the using this artificial intelligence technic as a useful tool for the neutron spectrometry and dosimetry by the simplification on the neutronic fields characterization inside radiotherapy rooms avoiding the use of traditional spectrometric systems. And once the H*(10) doses have been calculated, to take the appropriated actions to reduce or prevent the patient and working staff exposure to this undesirable neutron radiation. (Author)
Measurements of time dependent energy spectra of neutrons in a small graphite assembly
International Nuclear Information System (INIS)
Fujita, Yoshiaki; Sakamoto, Shigeyasu; Aizawa, Otohiko; Takahashi, Akito; Sumita, Kenji.
1975-01-01
The time-dependent energy spectra of neutrons have been measured in a small 30x30x30 cm 3 graphite assembly by means of the linac-chopper method, with a view to establishing experimental evidence that there is no asymptotic spectrum in such a small assembly, and in order to study the non-asymptotic behavior of neutrons. The arrangement of a polyethylene pre-moderator adjacent to the assembly made the measurements possible with the improvement obtained thereby of the neutron counting statistics. It was indicated from calculation that the presence of the pre-moderator had little effect - at least above the Bragg cut-off energy - on the evolution in time of the energy spectra of neutrons in the graphite assembly. The experimental results indicated very probable disappearance of asymptotic spectra, and revealed significant enhancement of trapping at Bragg energies with the lapse of time. This is consistent with the results of pulsed neutron experiments in small assemblies conducted by Takahashi et al., and falls in line with de Saussure's approximation. The spectra in the graphite assembly showed significant space dependence, the spectra becoming harder with increasing distance from the pre-moderator. This hardening may be attributed to the relatively faster propagation of higher energy neutrons. (auth.)
Recent improvements in the calculation of prompt fission neutron spectra: Preliminary results
International Nuclear Information System (INIS)
Madland, D.G.; LaBauve, R.J.; Nix, J.R.
1989-01-01
We consider three topics in the refinement and improvement of our original calculations of prompt fission neutron spectra. These are an improved calculation of the prompt fission neutron spectrum N(E) from the spontaneous fission of 252 Cf, a complete calculation of the prompt fission neutron spectrum matrix N(E,E n ) from the neutron-induced fission of 235 U, at incident neutron energies ranging from 0 to 15 MeV, and an assessment of the scission neutron component of the prompt fission neutron spectrum. Preliminary results will be presented and compared with experimental measurements and an evaluation. A suggestion is made for new integral cross section measurements. (author). 45 refs, 12 figs, 1 tab
Irradiation tests of ITER candidate Hall sensors using two types of neutron spectra
International Nuclear Information System (INIS)
Duran, I.; Bolshakova, I.; Holyaka, R.; Viererbl, L.; Lahodova, Z.; Sentkerestiova, J.; Bem, P.
2010-01-01
We report on irradiation tests of InSb based Hall sensors at two irradiation facilities with two distinct types of neutron spectra. One was a fission reactor neutron spectrum with a significant presence of thermal neutrons, while another one was purely fast neutron field. Total neutron fluence of the order of 10 16 cm -2 was accumulated in both cases, leading to significant drop of Hall sensor sensitivity in case of fission reactor spectrum, while stable performance was observed at purely fast neutron spectrum. This finding suggests that performance of this particular type of Hall sensors is governed dominantly by transmutation. Additionally, it further stresses the need to test ITER candidate Hall sensors under neutron flux with ITER relevant spectrum.
RDANN a new methodology to solve the neutron spectra unfolding problem
Energy Technology Data Exchange (ETDEWEB)
Ortiz R, J.M.; Martinez B, M.R.; Vega C, H.R. [UAZ, Av. Ramon Lopez Velarde No. 801, 98000 Zacatecas (Mexico)
2006-07-01
The optimization processes known as Taguchi method and DOE methodology are applied to the design, training and testing of Artificial Neural Networks in the neutron spectrometry field, which offer potential benefits in the evaluation of the behavior of the net as well as the ability to examine the interaction of the weights and neurons inside the same one. In this work, the Robust Design of Artificial Neural Networks methodology is used to solve the neutron spectra unfolding problem, designing, training and testing an ANN using a set of 187 neutron spectra compiled by the International Atomic Energy Agency, to obtain the better neutron spectra unfolded from the Bonner spheres spectrometer's count rates. (Author)
Measurement of time-dependent fast neutron energy spectra in a depleted uranium assembly
International Nuclear Information System (INIS)
Whittlestone, S.
1980-10-01
Time-dependent neutron energy spectra in the range 0.6 to 6.4 MeV have been measured in a depleted uranium assembly. By selecting windows in the time range 0.9 to 82 ns after the beam pulse, it was possible to observe the change of the neutron energy distributions from spectra of predominantly 4 to 6 MeV neutrons to spectra composed almost entirely of fission neutrons. The measured spectra were compared to a Monte Carlo calculation of the experiment using the ENDF/B-IV data file. At times and energies at which the calculation predicted a fission spectrum, the experiment agreed with the calculation, confirming the accuracy of the neutron spectroscopy system. However, the presence of discrepancies at other times and energies suggested that there are significant inconsistencies in the inelastic cross sections in the 1 to 6 MeV range. The time response generated concurrently with the energy spectra was compared to the Monte Carlo calculation. From this comparison, and from examination of time spectra measured by other workers using 235 U and 237 Np fission detectors, it would appear that there are discrepancies in the ENDF/B-IV cross sections below 1 MeV. The predicted decay rates were too low below and too high above 0.8 MeV
Lotfalizadeh, F.; Faghihi, R.; Bahadorzadeh, B.; Sina, S.
2017-07-01
Neutron spectrometry using a single-sphere containing dosimeters has been developed recently, as an effective replacement for Bonner sphere spectrometry. The aim of this study is unfolding the neutron energy spectra using GRNN artificial neural network, from the response of thermoluminescence dosimeters, TLDs, located inside a polyethylene sphere. The spectrometer was simulated using MCNP5. TLD-600 and TLD-700 dosimeters were simulated at different positions in all directions. Then the GRNN was used for neutron spectra prediction, using the TLDs' readings. Comparison of spectra predicted by the network with the real spectra, show that the single-sphere dosimeter is an effective instrument in unfolding neutron spectra.
Shielding experiments in different materials with 252Cf neutron spectra
International Nuclear Information System (INIS)
Sathian, Deepa; Marathe, P.K.; Pal, Rupali; Jayalakshmi, V.; Chourasiya, G.; Mayya, Y.S.
2008-01-01
Adequate shielding for neutron sources can be determined using analytical method or by actually measuring the attenuation for the target configuration. This paper describes the measurement of Half Value Thickness (HVT), Tenth Value Thickness (TVT), Σ values for four different shielding materials, using a standard 252 Cf neutron source and comparing with the values calculated using an empirical relationship. BF 3 based REM-counter is used for measurement of neutron dose equivalent, against different thickness of the shielding material. The experimental HVT and S values are in good agreement with the calculated values. From this study, it is concluded that, among the four materials studied, high density polyethylene (HDPE) is best suitable for the shielding of a 252 Cf neutron source. (author)
Energy spectra of fast neutrons by nuclear emulsion method
International Nuclear Information System (INIS)
Quaresma, A.A.
1977-01-01
An experimental method which uses nuclear emulsion plates to determine the energy spectrum of fission neutrons is described. By using this technique, we have obtained the energy distribution of neutrons from spontaneous fission of Cf 2 5 2 . The results are in good agreement with whose obtained previously by others authors who have used different detection techniques, and they are consistent with a Maxwellian distribution as expected by Weisskopf's nuclear evaporation theory. (author)
International Nuclear Information System (INIS)
Androsenko, A.A.; Androsenko, P.A.; Deeva, V.V.; Prokof'eva, Z.A.
1990-01-01
Analysis is made for the effect of mathematical model accuracy of the system concerned on the calculation results using the BRAND program system. Consideration is given to the impact of the following factors: accuracy of neutron source energy-angular characteristics description, various degrees of system geometry approximation, adequacy of Monte-Carlo method estimation to a real physical neutron detector. The calculation results analysis is made on the basis of the experiments on leakage neutron spectra measurement in spherical lead assemblies with the 14 MeV-neutron source in the centre. 4 refs.; 2 figs.; 10 tabs
Testing of the IRDF-90 cross-section library in benchmark neutron spectra
International Nuclear Information System (INIS)
Nolthenius, H.J.; Zsolnay, E.M.; Szondi, E.J.
1993-09-01
The new version of the International Reactor Dosimetry File IRDF-90 (called ''Version April 1993'') has been tested by calculation of average cross-sections and their uncertainties in a coarse three energy group structure and by neutron spectrum adjustments in reference neutron spectra. This paper presents the results obtained and compares them with the corresponding ones of the old IRDF-85 and with the data of the Nuclear Data Guide for Reactor Neutron Metrology. The applicability of the new library in the field of neutron metrology is discussed. (orig.)
International Nuclear Information System (INIS)
Zhang, S.; Chen, Z.; Nie, Y.; Wada, R.; Ruan, X.; Han, R.; Liu, X.; Lin, W.; Liu, J.; Shi, F.; Ren, P.; Tian, G.; Luo, F.; Ren, J.; Bao, J.
2015-01-01
Highlights: • Evaluated data for Tungsten are validated by integral experiment. • Leakage neutron spectra from the irradiation of D-T neutrons on Tungsten are measured at 60° and 120° by using a time-of-flight method. • The measured results are compared to the MCNP-4C calculated ones with evaluated data of the different libraries. - Abstract: Integral neutronics experiments have been investigated at Institute of Modern Physics, Chinese Academy of Sciences (IMP, CAS) in order to validate evaluated nuclear data related to the design of Chinese Initiative Accelerator Driven Systems (CIADS). In the present paper, the accuracy of evaluated nuclear data for Tungsten has been examined by comparing measured leakage neutron spectra with calculated ones. Leakage neutron spectra from the irradiation of D-T neutrons on Tungsten slab sample were experimentally measured at 60° and 120° by using a time-of-flight method. Theoretical calculations are carried out by Monte Carlo neutron transport code MCNP-4C with evaluated nuclear data of the ADS-2.0, ENDF/B-VII.0, ENDF/B-VII.1, JENDL-4.0 and CENDL-3.1 libraries. From the comparisons, it is found that the calculations with ADS-2.0 and ENDF/B-VII.1 give good agreements with the experiments in the whole energy regions at 60°, while a large discrepancy is observed at 120° in the elastic scattering peak, caused by a slight difference in the oscillation pattern of the elastic angular distribution at angles larger than 20°. However, the calculated spectra using data from ENDF/B-VII.0, JENDL-4.0 and CENDL-3.1 libraries showed larger discrepancies with the measured ones, especially around 8.5–13.5 MeV. Further studies are presented for these disagreements
COOLC, Ne-213 Liquid Scintillation Detector Neutron Spectra Unfolding
International Nuclear Information System (INIS)
1971-01-01
1 - Nature of physical problem solved: COOLC is designed to calculate a neutron energy spectrum from a pulse-height spectrum produced by a detector system using the liquid scintillator NE-213. 2 - Method of solution: The program estimates the counts which would be observed in an ideal detector system having a response which is specified by the user. The solution implicitly takes into account the non-negativity of the desired neutron spectrum. The solution is obtained by finding a nearly optimal combination of slices through the spectrometer response functions such that their sum approximates the response of a channel of the ideal analyzer, and then uses the coefficients so determined to obtain an estimate of the desired neutron spectrum. 3 - Restrictions on the complexity of the problem: There are none noted
Inelastic neutron spectra and cross sections for 238 U
International Nuclear Information System (INIS)
Kornilov, N.V.; Kagalenko, A.V.
1994-01-01
The report discusses the experimental facilities of IPPE, results of spectra and cross sections investigations. The problems of existing data libraries were highlighted. Some of these problems for example, inelastic spectra at high energy may be solved by correct theoretical calculation. Others like level cross sections at E > 2 MeV and the possible structure of excitation function for group levels between 0.5 to 0.85 MeV demand new experimental efforts. 21 refs., 11 figs., 5 tabs
Measurement and analysis of fast neutron spectra in reactor materials by time-of-flight method
International Nuclear Information System (INIS)
Hayashi, Shuhei; Kimura, Itsuro; Kobayashi, Shohei; Yamamoto, Shuji; Nishihara, Hiroshi.
1982-01-01
The LINAC-TOF experiments have been done to measure the neutron energy spectra in the assemblies of reactor materials. The sample materials to be measured were iron, stainless steel, aluminum, nickel, zirconium, thorium, lithium, and so on. The shapes of assemblies were piles (rectangular parallelopiped, sphere, and polyhedron) and slab. A photoneutron target was set at the center of the pile assemblies. Each assembly has an electron injection hole and a re-entrant hole. In case of a slab, a photo neutron target was placed at the outside of the slab. Neutrons were generated by using an electron linear accelerator (LINAC). The length of the flight path was 20 m. The neutron detectors were a Li-6 glass scintillator and a B-10 vaseline-NaI(Tl) scintillator. The spatial distributions of neutrons in the piles were measured by the foil activation method. The neutron transport calculation was performed, and the evaluation of group constants was made. (Kato, T.)
Multicomponent activation detector measurements of reactor neutron spectra
International Nuclear Information System (INIS)
Sandberg, J.; Aarnio, P. A.; Routti, J. T.
1984-01-01
Information on the neutron flux is required in many applications of research reactors, such as activation analysis or radiation damage measurements. Flux spectrum measurements are commonly carried out with activation foils. The reaction types used are threshold reactions in the fast energy region, resonance reactions in the intermediate region and neutron capture reactions with l/v-cross section in the thermal region. It has been shown that it is possible to combine several detector elements into homogeneous multicomponent detectors. The activities of all detector reaction products can be determined with a single gamma spectrum measurement. The multicomponent principle sets some restrictions on the choice of detector reactions, for example, each product nuclide may be produced in one reaction only. Separate multicomponent threshold and resonance detectors were designed for the fast and intermediate regions, respectively. The detectors were fabricated in polyethylene irradiation capsules or quartz glass ampoules, and they were irradiated in a cadmium cover. The detectors were succesfully used in the irradiation ring and in the core of a Triga reactor. The intermediate and fast neutron spectrum was unfolded with the least-squares unfolding program LOUHI. According to the preliminary results multicomponent activation detectors might constitute a convenient means for carrying out routine neutron spectrum measurements in research reactors. (orig.)
Energy spectra of primary knock-on atoms under neutron irradiation
International Nuclear Information System (INIS)
Gilbert, M.R.; Marian, J.; Sublet, J.-Ch.
2015-01-01
Materials subjected to neutron irradiation will suffer from a build-up of damage caused by the displacement cascades initiated by nuclear reactions. Previously, the main “measure” of this damage accumulation has been through the displacements per atom (dpa) index, which has known limitations. This paper describes a rigorous methodology to calculate the primary atomic recoil events (often called the primary knock-on atoms or PKAs) that lead to cascade damage events as a function of energy and recoiling species. A new processing code SPECTRA-PKA combines a neutron irradiation spectrum with nuclear recoil data obtained from the latest nuclear data libraries to produce PKA spectra for any material composition. Via examples of fusion relevant materials, it is shown that these PKA spectra can be complex, involving many different recoiling species, potentially differing in both proton and neutron number from the original target nuclei, including high energy recoils of light emitted particles such as α-particles and protons. The variations in PKA spectra as a function of time, neutron field, and material are explored. The application of PKA spectra to the quantification of radiation damage is exemplified using two approaches: the binary collision approximation and stochastic cluster dynamics, and the results from these different models are discussed and compared. - Highlights: • Recoil cross-section matrices under neutron irradiation are generated. • Primary knock-on atoms (PKA) spectra are calculated for fusion relevant materials. • Variation in PKA spectra due to changes in geometry are considered. • Inventory simulations to consider time-evolution in PKA spectra. • Damage quantification using damage functions from different approximations.
The application of n-γ discrimination in 252Cf spontaneous neutron TOF spectra measurement
International Nuclear Information System (INIS)
Zhou Haojun; Zhang Yi; Li Jiansheng; Jin Yu; Wang Jie; Li Chunyuan
2004-01-01
The BC501 scintillator is used as a fast neutron detector. The effect that the pulse rise time method was used to discriminate γ from 252 Cf spontaneous neutron TOF spectra is studied in the experiment. A pulse rise time separation spectra of γ and 252 Cf spontaneous neuron upon 1 MeV is obtained, the n-γ separation function reaches to 4.6. When the result of pulse rise time separation coincides with the time-of-flight spectra in which the neutron energy is upon 0.5 MeV, 0.8 MeV and 1.0 MeV, comparing with the anticoincidence, γ was eliminated 99.90% at least. (authors)
International Nuclear Information System (INIS)
Peneliau, Y.; Litaize, O.; Archier, P.; De Saint Jean, C.
2014-01-01
A large set of nuclear data are investigated to improve the calculation predictions of the new neutron transport simulation codes. With the next generation of nuclear power plants (GEN IV projects), one expects to reduce the calculated uncertainties which are mainly coming from nuclear data and are still very important, before taking into account integral information in the adjustment process. In France, future nuclear power plant concepts will probably use MOX fuel, either in Sodium Fast Reactors or in Gas Cooled Fast Reactors. Consequently, the knowledge of 239 Pu cross sections and other nuclear data is crucial issue in order to reduce these sources of uncertainty. The Prompt Fission Neutron Spectra (PFNS) for 239 Pu are part of these relevant data (an IAEA working group is even dedicated to PFNS) and the work presented here deals with this particular topic. The main international data files (i.e. JEFF-3.1.1, ENDF/B-VII.0, JENDL-4.0, BRC-2009) have been considered and compared with two different spectra, coming from the works of Maslov and Kornilov respectively. The spectra are first compared by calculating their mathematical moments in order to characterize them. Then, a reference calculation using the whole JEFF-3.1.1 evaluation file is performed and compared with another calculation performed with a new evaluation file, in which the data block containing the fission spectra (MF=5, MT=18) is replaced by the investigated spectra (one for each evaluation). A set of benchmarks is used to analyze the effects of PFNS, covering criticality cases and mock-up cases in various neutron flux spectra (thermal, intermediate, and fast flux spectra). Data coming from many ICSBEP experiments are used (PU-SOL-THERM, PU-MET-FAST, PU-MET-INTER and PU-MET-MIXED) and French mock-up experiments are also investigated (EOLE for thermal neutron flux spectrum and MASURCA for fast neutron flux spectrum). This study shows that many experiments and neutron parameters are very sensitive to
D-D neutron energy-spectra measurements in Alcator C
International Nuclear Information System (INIS)
Pappas, D.S.; Wysocki, F.J.; Furnstahl, R.J.
1982-08-01
Measurements of energy spectra of neutrons produced during high density (anti n/sub e/ > 2 x 10 14 cm -3 ) deuterium discharges have been performed using a proton-recoil (NE 213) spectrometer. A two foot section of light pipe (coupling the scintillator and photomultiplier) was used to extend the scintillator into a diagnostic viewing port to maximize the neutron detection efficiency while not imposing excessive magnetic shielding requirements. A derivative unfolding technique was used to deduce the energy spectra. The results showed a well defined peak at 2.5 MeV which was consistent with earlier neutron flux measurements on Alcator C that indicated the neutrons were of thermonuclear origin
Neutron spectra in two beam ports of a TRIGA Mark III reactor with HEU fuel
International Nuclear Information System (INIS)
Vega C, H. R.; Hernandez D, V. M.; Paredes G, L.; Aguilar, F.
2012-10-01
Before to change the HEU for Leu fuel of the ININ's TRIGA Mark III nuclear reactor the neutron spectra were measured in two beam ports using 5 and 10 W. Measurements were carried out in a tangential and a radial beam port using a Bonner sphere spectrometer. It was found that neutron spectra are different in the beam ports, in radial beam port the amplitude of thermal and fast neutrons are approximately the same while, in the tangential beam port thermal neutron peak is dominant. In the radial beam port the fluence-to-ambient dose equivalent factors are 131±11 and 124±10 p Sv-cm 2 for 5 and 10 W respectively while in the tangential beam port the fluence-to-ambient dose equivalent factor is 55±4 p Sv-cm 2 for 10 W. (Author)
International Nuclear Information System (INIS)
Santoro, R.T.; Alsmiller, R.G. Jr.; Barnes, J.M.; Chapman, G.T.
1980-08-01
Integral experiments that measure the transport of approx. 14 MeV D-T neutrons through laminated slabs of proposed fusion reactor shield materials have been carried out. Measured and calculated neutron and gamma ray energy spectra are compared as a function of the thickness and composition of stainless steel type 304, borated polyethylene, and Hevimet (a tungsten alloy), and as a function of detector position behind these materials. The measured data were obtained using a NE-213 liquid scintillator using pulse-shape discrimination methods to resolve neutron and gamma ray pulse height data and spectral unfolding methods to convert these data to energy spectra. The calculated data were obtained using two-dimensional discrete ordinates radiation transport methods in a complex calculational network that takes into account the energy-angle dependence of the D-T neutrons and the nonphysical anomalies of the S/sub n/ method
Theoretical analysis of time-dependent neutron spectra in bulk assemblies
International Nuclear Information System (INIS)
Akimoto, Tadashi; Ogawa, Yuichi; Togawa, Orihiko.
1988-01-01
Time-dependent neutron spectra in an iron assembly and in a graphite assembly are obtained with the one-dimensional S N calculation, in order an attempt to investigate the availability of these spectra to the benchmark test by the LINAC-TOF method for evaluation of nuclear data and numerical methods. The group constants are taken from the JAERI FAST SET Version 1, 2 and the ABBN SET. It was demonstrated by a sensitivity test that the time-dependent neutron spectra are sensitive to changes in the inelastic scattering cross section data in the iron assembly and to changes in the elastic scattering cross section data in the graphite assembly. Moreover, it is shown that the time-dependent spectra in the graphite assembly are sensitive to the group structure. Because some information about the neutron transport phenomena which has not been obtained in the stationary spectra is observed in the time-dependent spectra, the availability of the benchmark test based on the time-dependent spectra is indicated from the theoretical analysis. (author)
Spherical Harmonics Treatment of Epithermal Neutron Spectra in Reactor lattices
International Nuclear Information System (INIS)
Matausek, M.V.
1972-04-01
A procedure has been developed to solve the slowing down transport equation for neutrons in a cylindrized reactor lattice cell. Treating the anisotropy of the epithermal neutron flux by the spherical harmonics formalism, which reduces the space-angle-lethargy-dependent transport equation to the matrix integrodifferential equation in space and lethargy, and replacing the lethargy transfer integrals by finite-difference forms, a set of matrix ordinary differential equations, with lethargy and space dependent coefficients, is obtained. In the resonance region this set takes a lower block triangular form and can be directly solved by forward block substitution; in the lethargy range, where the fast fission effects have to be considered, the iterative procedure is introduced. A simple and efficient approximation is then proposed, making possible the analytical solution for the spatial dependence of the spherical harmonics flux moments. The proposed procedure has been numerically examined and approved. Some typical results are presented and discussed. (author)
Application of modular neutron spectrometer to measure neutron spectra from fission of 252Cf
International Nuclear Information System (INIS)
Szeflinski, Z.; Osuch, S.; Popkiewicz, M.; Wilhelmi, Z.; Zelazny, Z.
1996-01-01
The neutron spectrometer MONA (Modular Neutron Array) and its test has been described. The spectrometers consist of eight BC-501A liquid scintillator detectors of BICRON which allow one to distinguish between the pulses from gamma quanta and neutrons using pulse shape discrimination (PSD) method. The electronic equipment for the PSD and the test result using the 252 Cf radioactive source are presented
International Nuclear Information System (INIS)
Schickler, R.A.; Marcum, W.R.; Reese, S.R.
2013-01-01
Highlights: • The Oregon State TRIGA ® Reactor neutron spectra is characterized herein. • Neutron spectra between highly enriched uranium and low enriched uranium cores are compared. • Discussion is given as to differences between HEU and LEU core spectra results and impact on experiments. -- Abstract: In 2008, the Oregon State TRIGA ® Reactor (OSTR) was converted from highly enriched uranium (HEU) fuel lifetime improvement plan (FLIP) fuel to low-enriched uranium (LEU) fuel. This effort was driven and supported by the Department of Energy's (DoE's) Reduced Enrichment for Research and Test Reactors (RERTR) program. The basis behind the RERTR program's ongoing conversion effort is to reduce the nuclear proliferation risk of civilian research and test reactors. The original intent of the HEU FLIP fuel was to provide fuel to research reactors that could be utilized for many years before a necessary refueling cycle. As a research reactor, the OSTR provides irradiation facilities for a variety of applications, such as activation analysis, fission-track dating, commercial isotope production, neutron radiography, prompt gamma characterization, and many others. In order to accurately perform these research functions, several studies had been conducted on the HEU FLIP fuel core to characterize the neutron spectra in various experimental facilities of the OSTR (Tiyapun, 1997; Ashbaker, 2005). As useful as these analyses were, they are no longer valid due to the change in fuel composition and the resulting alteration of core performance characteristics. Additionally, the core configuration (fuel reconfiguration) was altered between the HEU and LEU cores. This study characterizes the neutron spectra in various experimental facilities within and around the current LEU core. It also compares the spectra to that which was yielded in the HEU core through use of Monte Carlo n-Particle 5 (MCNP5) and experimental adjustment via a least-squares technique. The quantification of
Neutron energy spectra from the thick target 9Be(d,n)10B reaction
International Nuclear Information System (INIS)
Whittlestone, S.
1976-12-01
The energy spectrum of neutrons emitted when deuterons impinge on a thick beryllium target has been measured using an NE213 scintillation detector and the time-of-flight technique. Spectra were measured at angles of 0, 30, 45, 60, 90, 120 and 150 0 for deuteron energies of 1.4, 1.8, 2.3 and 2.8 MeV. Tables are presented of these angle-dependent energy spectra, the angle-integrated energy dependent yeidls, and the total neutron yield as a function of deuteron energy. (author)
Study on thermal neutron spectra in reactor moderators by time-of-flight method
International Nuclear Information System (INIS)
Akino, Fujiyoshi
1982-12-01
Prediction of thermal neutron spectra in a reactor core plays very important role in the neutronic design of the reactor for obtaining the accurate thermal group constants. It is well known that the neutron scattering properties of the moderator materials markedly influence the thermal neutron spectra. Therefore, 0 0 angular dependent thermal neutron spectra were measured by the time-of-flight method in the following moderator bulks 1) Graphite bulk poisoned with boron at the temperatures from 20 to 800 0 C, 2) Light water bulk poisoned with Cadmium and/or Indium, 3) Light water-natural uranium heterogeneous bulk. The measured results were compared with calculation utilizing Young-Koppel and Haywood scattering model for graphite and light water respectively. On the other hand, a variety of 20% enriched uranium loaded and graphite moderated cores consisting of the different lattice cell in a wide range of the carbon to uranium atomic ratio have been built at Semi-Homogeneous Critical Experimental Assembly (SHE) to perform the critical experiments related to Very High Temperature Reactor (VHTR). The experimental data were for the critical masses in 235 U, reactivity worths of experimental burnable poison rods, thorium rods, natural-uranium rods and experimental control rods and kinetic parameters. It is made clear from comparison between measurement and calculation that the accurate thermal group constants can be obtained by use of the Young-Koppel and Haywood neutron scattering models if heterogeneity of reactor core lattices is taken into account precisely. (author)
Gamma-ray emission spectra from spheres with 14 MeV neutron source
International Nuclear Information System (INIS)
Yamamoto, Junji; Kanaoka, Takeshi; Murata, Isao; Takahashi, Akito; Sumita, Kenji
1989-01-01
Energy spectra of neutron-induced gamma-rays emitted from spherical samples were measured using a 14 MeV neutron source. The samples in use were LiF, Teflon:(CF 2 ) n , Si, Cr, Mn, Co, Cu, Nb, Mo, W and Pb. A diameter of the sphere was either 40 or 60 cm. The gamma-ray energy in the emission spectra covered the range from 500 keV to 10 MeV. Measured spectra were compared with transport calculations using the nuclear data files of JENDL-3T and ENDF/B-IV. The agreements between the measurements and the JENDL-3T calculations were good in the emission spectra for the low energy gamma-rays from inelastic scattering. (author)
International Nuclear Information System (INIS)
Luo, F.; Han, R.; Nie, Y.; Chen, Z.; Zhang, S.; Shi, F.; Lin, W.; Ren, P.; Tian, G.; Sun, Q.; Gou, B.; Ruan, X.; Ren, J.; Ye, M.
2016-01-01
Highlights: • Evaluated data for SiC are validated by a high precision benchmark experiment. • Leakage neutron spectra from SiC cylinders are measured at 60° and 120° using time-of-flight method. • The experimental results are compared with the MCNP-4C calculations with ENDF-BVII.1, JENDL-4.0 and CENDL-3.1 libraries. • The SiC evaluated nuclear data from CENDL-3.1 library was checked for the first time and proved to be reliable. - Abstract: Benchmarking of evaluated nuclear data libraries was performed for 14 MeV neutrons on silicon carbide samples. The experiments were carried out by using the benchmark experimental facility at China Institute of Atomic Energy (CIAE). The leakage neutron spectra from SiC (Φ13 cm × 20 cm) at 60° and 120° and SiC (Φ13 cm × 2 cm) at 60° were measured by the TOF method. The measured spectra are well reproduced by MCNP-4C calculations with the CENDL-3.1, ENDF/B-VII.1 and JENDL-4.0 evaluated nuclear data libraries, except 5–8 MeV range for 20 cm thickness. The discrepancies are mostly considered as caused by the improper evaluation of the angular distribution and secondary neutron energy distribution of the elastic scattering and inelastic scattering in evaluated nuclear data libraries.
Energy Technology Data Exchange (ETDEWEB)
Luo, F. [School of Nuclear Science and Technology, University of Science and Technology of China, Hefei 230026 (China); Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000 (China); Han, R. [Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000 (China); Key Laboratory of Nuclear Data, China Institute of Atomic Energy, Beijing 102413 (China); Nie, Y. [Key Laboratory of Nuclear Data, China Institute of Atomic Energy, Beijing 102413 (China); Chen, Z., E-mail: zqchen@impcas.ac.cn [Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000 (China); Zhang, S. [College of Physics Electronic Information, Inner Mongolia University for the Nationalities, Tongliao 028000 (China); Shi, F.; Lin, W.; Ren, P.; Tian, G.; Sun, Q.; Gou, B. [Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000 (China); Ruan, X.; Ren, J. [Key Laboratory of Nuclear Data, China Institute of Atomic Energy, Beijing 102413 (China); Ye, M. [School of Nuclear Science and Technology, University of Science and Technology of China, Hefei 230026 (China)
2016-11-15
Highlights: • Evaluated data for SiC are validated by a high precision benchmark experiment. • Leakage neutron spectra from SiC cylinders are measured at 60° and 120° using time-of-flight method. • The experimental results are compared with the MCNP-4C calculations with ENDF-BVII.1, JENDL-4.0 and CENDL-3.1 libraries. • The SiC evaluated nuclear data from CENDL-3.1 library was checked for the first time and proved to be reliable. - Abstract: Benchmarking of evaluated nuclear data libraries was performed for 14 MeV neutrons on silicon carbide samples. The experiments were carried out by using the benchmark experimental facility at China Institute of Atomic Energy (CIAE). The leakage neutron spectra from SiC (Φ13 cm × 20 cm) at 60° and 120° and SiC (Φ13 cm × 2 cm) at 60° were measured by the TOF method. The measured spectra are well reproduced by MCNP-4C calculations with the CENDL-3.1, ENDF/B-VII.1 and JENDL-4.0 evaluated nuclear data libraries, except 5–8 MeV range for 20 cm thickness. The discrepancies are mostly considered as caused by the improper evaluation of the angular distribution and secondary neutron energy distribution of the elastic scattering and inelastic scattering in evaluated nuclear data libraries.
Energy Technology Data Exchange (ETDEWEB)
Greene, N.M.; Ford, W.E. III; Petrie, L.M.; Arwood, J.W.
1992-10-01
AMPX-77 is a modular system of computer programs that pertain to nuclear analyses, with a primary emphasis on tasks associated with the production and use of multigroup cross sections. AH basic cross-section data are to be input in the formats used by the Evaluated Nuclear Data Files (ENDF/B), and output can be obtained in a variety of formats, including its own internal and very general formats, along with a variety of other useful formats used by major transport, diffusion theory, and Monte Carlo codes. Processing is provided for both neutron and gamma-my data. The present release contains codes all written in the FORTRAN-77 dialect of FORTRAN and wig process ENDF/B-V and earlier evaluations, though major modules are being upgraded in order to process ENDF/B-VI and will be released when a complete collection of usable routines is available.
International Nuclear Information System (INIS)
Greene, N.M.; Ford, W.E. III; Petrie, L.M.; Arwood, J.W.
1992-10-01
AMPX-77 is a modular system of computer programs that pertain to nuclear analyses, with a primary emphasis on tasks associated with the production and use of multigroup cross sections. AH basic cross-section data are to be input in the formats used by the Evaluated Nuclear Data Files (ENDF/B), and output can be obtained in a variety of formats, including its own internal and very general formats, along with a variety of other useful formats used by major transport, diffusion theory, and Monte Carlo codes. Processing is provided for both neutron and gamma-my data. The present release contains codes all written in the FORTRAN-77 dialect of FORTRAN and wig process ENDF/B-V and earlier evaluations, though major modules are being upgraded in order to process ENDF/B-VI and will be released when a complete collection of usable routines is available
The covariance matrix of neutron spectra used in the REAL 84 exercise
International Nuclear Information System (INIS)
Matzke, M.
1986-08-01
Covariance matrices of continuous functions are discussed. It is pointed out that the number of non-vanishing eigenvalues corresponds to the number of random variables (parameters) involved in the construction of the continuous functions. The covariance matrices used in the REAL 84 international intercomparison of unfolding methods of neutron spectra are investigated. It is shown that a small rank of these covariance matrices leads to a restriction of the possible solution spectra. (orig.) [de
Effects of Hot-Spot Geometry on Backscattering and Down-Scattering Neutron Spectra
Mohamed, Z. L.; Mannion, O. M.; Forrest, C. J.; Knauer, J. P.; Anderson, K. S.; Radha, P. B.
2017-10-01
The measured neutron spectrum produced by a fusion experiment plays a key role in inferring observable quantities. One important observable is the areal density of an implosion, which is inferred by measuring the scattering of neutrons. This project seeks to use particle-transport simulations to model the effects of hot-spot geometry on backscattering and down-scattering neutron spectra along different lines of sight. Implosions similar to those conducted at the Laboratory of Laser Energetics are modeled by neutron transport through a DT plasma and a DT ice shell using the particle transport codes MCNP and IRIS. Effects of hot-spot geometry are obtained by ``detecting'' scattered neutrons along different lines of sight. This process is repeated for various hot-spot geometries representing known shape distortions between the hot spot and the shell. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0001944.
Resonant Inverse Compton Scattering Spectra from Highly Magnetized Neutron Stars
Wadiasingh, Zorawar; Baring, Matthew G.; Gonthier, Peter L.; Harding, Alice K.
2018-02-01
Hard, nonthermal, persistent pulsed X-ray emission extending between 10 and ∼150 keV has been observed in nearly 10 magnetars. For inner-magnetospheric models of such emission, resonant inverse Compton scattering of soft thermal photons by ultrarelativistic charges is the most efficient production mechanism. We present angle-dependent upscattering spectra and pulsed intensity maps for uncooled, relativistic electrons injected in inner regions of magnetar magnetospheres, calculated using collisional integrals over field loops. Our computations employ a new formulation of the QED Compton scattering cross section in strong magnetic fields that is physically correct for treating important spin-dependent effects in the cyclotron resonance, thereby producing correct photon spectra. The spectral cutoff energies are sensitive to the choices of observer viewing geometry, electron Lorentz factor, and scattering kinematics. We find that electrons with energies ≲15 MeV will emit most of their radiation below 250 keV, consistent with inferred turnovers for magnetar hard X-ray tails. More energetic electrons still emit mostly below 1 MeV, except for viewing perspectives sampling field-line tangents. Pulse profiles may be singly or doubly peaked dependent on viewing geometry, emission locale, and observed energy band. Magnetic pair production and photon splitting will attenuate spectra to hard X-ray energies, suppressing signals in the Fermi-LAT band. The resonant Compton spectra are strongly polarized, suggesting that hard X-ray polarimetry instruments such as X-Calibur, or a future Compton telescope, can prove central to constraining model geometry and physics.
The secondary neutrons spectra of 235U, 238U for incident energy range 1-2.5 MeV
International Nuclear Information System (INIS)
Kornilov, N.V.; Kagalenko, A.B.; Balitsky, A.V.; Baryba, V.Ja.; Androsenko, P.A.; Androsenko, A.A.
1993-01-01
Spectra of inelastic scattered neutrons and fission neutrons were measured with neutron time of flight spectrometer. The solid tritium target was used as a neutron source. The energy distribution of neutrons on the sample was calculated with Monte-Carlo code, taking into account interaction income protons inside target and reaction kinematics. The detector efficiency was determined with 252 Cf source. The multiple scattering and absorption corrections were calculated with codes packet BRAND. Our results confirm ENDF/B-6 data library. (author)
Theoretical description of prompt neutron multiplicity and spectra
International Nuclear Information System (INIS)
Manailescu, C.
2013-02-01
The present work concerns two of successful models used today: PbP (Point by Point) and the Monte-Carlo approaches for providing all quantities characterizing the prompt neutron and gamma-ray emission. Therefore the thesis is structured as described below. The description of the PbP model and of the extended Los Alamos model for higher energies that takes into account the secondary chains and ways is given in Chapter II. In this chapter are detailed also examples of PbP and most probable fragmentation approach calculations for various quantities which characterize prompt emission: multi-parametric matrices [meaning different quantities as a function of fragment and of TKE (Total Kinetic Energy of the fission fragments)], quantities as a function of fragment mass, quantities as a function of the TKE and total average quantities, for different spontaneous and neutron induced fissioning systems. Special care was given to the TXE (Total Excitation Energy) partition between the fully accelerated fission fragments, two partition methods used in the PbP model being discussed in details. In Chapter III is given the description of the Monte Carlo treatment included in the FIFRELIN code. Only those aspects that differ from the PbP treatment are emphasized, namely the treatment of the moment of inertia entering the rotational energy calculation and the TXE partition method based on a mass dependent temperature ratio law. A special attention is given to the latest developments of the code concerning the inclusion of the energy dependent compound nucleus cross-section of the inverse process of neutron evaporation from fragments. In this chapter examples of calculation with the FIFRELIN code for the case of the standard fissioning system 252 Cf (SF) are given. Original results for several plutonium spontaneous fissioning systems ( 236,238,240,242,244 Pu) and one neutron induced fissioning system ( 239 Pu(nth,f)) obtained with both PbP and Monte-Carlo treatments are given in
Prompt fission neutron spectra and anti νp
International Nuclear Information System (INIS)
Madland, D.G.
Methods used to obtain the evaluated prompt fisson neutron spectrum N(E) and the average prompt neutron multiplicity anti ν/sub p/ are reviewed. The relative influence of experimental data; interpolated, extrapolated, and fitted experimental data; systematics; and nuclear theory are considered for the cases where (a) abundant experimental data exist, (b) some experimental data exist, and (c) no experimental data exist. The Maxwellian and Watt distributions, and the determination of the parameters of these distributions by data fitting, are described and compared to recent new theoretical work on the calculation of N(E). Similarly, various expressions for anti γ/sub p/ that have been obtained by data fitting and systematics are described and compared to recent new theoretical work. Complications in the evaluation of N(E) and anti γ/sub p/ due to the onset of multiple-chance fission and the interrelationships between N(E), anti γΔ/sub p/ and the multiple-chance fission cross section are discussed using the example of the fission of 235 U. Some statistics and comments are given on the evaluations of N(E) and anti γ/sub p/ contained in ENDF/B-V, and a number of concluding recommendations are made for future evaluation work
Energy Technology Data Exchange (ETDEWEB)
Poole, M. J.; Schofield, P.; Sinclair, R. N. [United Kingdom Atomic Energy Authority, Research Group, Atomic Energy Research Establishment, Harwell (United Kingdom)
1964-04-15
Complementary programmes to determine moderator scattering law and to test its validity through spectrum measurements have been initiated at Harwell. The scattering-law experiments have been largely carried out at Chalk River, while the data processing is done at the Argonne National Laboratory and the analysis and necessary extrapolation from the measurements performed at Harwell. The spectrum measurements fall naturally into two parts. Using time-of-flight spectroscopy a wide range of measurements has been made of thermal neutron spectra in homogeneous poisoned moderators. This work parallels and extends the earlier work of the author and of Beyster et al. and serves to check the validity of energy transfer cross-sections o(E -> E) derived from the scattering law in use. However such an experiment is completely insensitive to the angular dependence of scattering and to that part of the scattering cross-section involving no energy change of the scattered neutron, both of which are important in any spatially dependent problem. Accordingly other experiments have been undertaken in which spatial or thermal discontinuities were deliberately introduced to make the spectrum depend on the complete scattering law. The first such is the so-called ''two block experiment'' in which thermal neutrons are allowed to diffuse from a block of graphite at room temperature into a second block whose temperature may be raised to 400 Degree-Sign C. Neutron spectra are measured at various positions near to the temperature discontinuity by extracting a beam of neutrons from each position and passing this into a chopper time-of-flight spectrometer. As a preliminary analysis ''rethermalization cross-sections'' have been derived from the experiment which may be compared with those of Bennet et al. who perfomved a similar experiment using energy sensitive detectors. In order to obtain a more detailed comparison, multigroup diffusion-theory calculations are being carried out, using the Chalk
Use of the foil activation method with arbitrary trial functions to determine neutron energy spectra
International Nuclear Information System (INIS)
Kelly, J.G.; Vehar, D.W.
1987-01-01
Neutron Spectra have been measured by the foil activation method in thirteen different environments in and around the Sandia Pulsed Reactor (SPR-III), the White Sands Missile Range FBR, and the Annular Core Research Reactor (ACRR). The unfolded spectra were obtained by using the SANDII code in a manner which was not dependent on the initial trial. This altered technique is, therefore, better suited for the determination of spectra in environments that are difficult to predict by calculation, and it tends to reveal features that may be biased out by the use of standard trial functions
International Nuclear Information System (INIS)
Johnson, M.R.; Trommsdorff, H.P.
2009-01-01
Vibrational spectra of crystalline powder of four isotopologues of formic acid (HCOOH, HCOOD, DCOOH, DCOOD) and of acetic acid (CH 3 COOH, CH 3 COOD, CD 3 COOH, CD 3 COOD) were recorded at 20 K by inelastic neutron scattering. These spectra are compared with computed spectra based on harmonic force fields derived from periodic density functional theory (DFT) calculations. The assignment of all internal vibrations is obvious from the spectral changes under isotopic substitution. Discrepancies between calculation and experiment expose the over evaluation of the strength of the hydrogen bond by these standard DFT calculations
Method of spectra parametrization of (n, x) and (n, nx) reactions induced by DT-neutrons
International Nuclear Information System (INIS)
Aleksandrov, D.V.; Kovrigin, B.S.
1980-01-01
A method for parmetrization of experimental spectra has been developed for more convenient carrying out a process of separating competing mechanisms contributions in spectra of the (n, x) and (n, nx) reactions induced with DT neutrons. Differential cross sections of competing partial processes are used. as expanding coefficients. Model spectra may be represented in the form of tabulated-given functions calculated separately from formulae of any complexity degree. Fit of model expressions is performed by the least square method (lsm). Step-by-step algorithm of nonlinear optimization is used for search for lsm- evaluations of theoretical models parameters [ru
Data and software for calculating neutron spectra from measured reaction rates
International Nuclear Information System (INIS)
Berzonis, M.A.; Bonbars, Kh.Ya.
1981-01-01
The information system SAIPS is presented, which allows the automated calculation of neutron spectra and the use of cross section libraries on EC type computers. The following programmes can be applied: SAND II, WINDOWS, CRYSTAL BALL, RFSP JUEL, etc. The system includes both cross section libraries established by means of the code mentioned and libraries recommended by several laboratories. (author)
Calculation of neutron and gamma-ray emission spectra produced by p +2''2'Al reactions
International Nuclear Information System (INIS)
Arthur, E.D.
1985-01-01
As a contribution to the US/Japan cooperative program in fusion neutronics, we have prepared a library of multigroup neutron cross sections, scattering matrices, and covariances (uncertainties and their correlations). This 74-group library, called COVFILS-2, is being used at Los Alamos and at the University of California at Los Angeles in the sensitivity and uncertainty analysis of the Li 2 O integral experiment recently performed at the Fast Neutron Source (FNS) in Japan. Another intended use of this library is in the estimation of the uncertainty in key performance parameters (such as breeding ratio) of conceptual fusion reactors. The 14 materials included in the first version of COVFILS-2 are H, 6 Li, 7 Li, Be, C, N, O, Na, Al, Si, Cr, Fe, Ni, and Pb
Experiment and analysis of neutron spectra in a concrete assembly bombarded by 14 MeV neutrons
International Nuclear Information System (INIS)
Oishi, Koji; Tomioka, Kazuyuki; Ikeda, Yujiro; Nakamura, Tomoo.
1988-01-01
Neutron spectrum in concrete bombarded by 14 MeV neutrons was measured using a miniature NE213 spectrometer and multi-foil activation method. A good agreement between those two experimental methods was obtained within experimental errors. The measured spectrum was compared with calculated ones using two-dimensional transport code DOT3.5 with 125 group structure cross section libraries based on ENDF/B-IV, JENDL-2, and JENDL-3T (the testing version of JENDL-3.) In the D-T neutron peak region, measured and calculated neutron spectra agreed well with each other for those libraries. However, disagreements of about -10 % to +50 % and -30 % to +40 % were obtained in the MeV region and still lower neutron energy range, respectively. As a result, it was concluded that those discrepancies were caused by the overestimation of secondary neutrons emitted by inelastic scattering from O, Si, and/or Ca which were the main components of concrete. (author)
Energy Technology Data Exchange (ETDEWEB)
Chang, Jonghwa [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)
2014-05-15
Parallelization of Monte Carlo simulation is widely adpoted. There are also several parallel algorithms developed for the SN transport theory using the parallel wave sweeping algorithm and for the CPM using parallel ray tracing. For practical purpose of reactor physics application, the thermal feedback and burnup effects on the multigroup cross section should be considered. In this respect, the domain decomposition method(DDM) is suitable for distributing the expensive cross section calculation work. Parallel transport code and diffusion code based on the Raviart-Thomas mixed finite element method was developed. However most of the developed methods rely on the heuristic convergence of flux and current at the domain interfaces. Convergence was not attained in some cases. Mechanical stress computation community has also work on the DDM to solve the stress-strain equation using the finite element methods. The most successful domain decomposition method in terms of robustness is FETI-DP. We have modified the original FETI-DP to solve the eigenvalue problem for the multigroup diffusion problem in this study.
COLLI-PTB, Neutron Fluence Spectra for 3-D Collimator System by Monte-Carlo
International Nuclear Information System (INIS)
Schlegel-Bickmann, Dietrich
1995-01-01
1 - Description of program or function: For optimizing collimator systems (shieldings) for fast neutrons with energies between 10 KeV and 20 MeV. Only elastic and inelastic neutron scattering processes are involved. Isotropic angular distribution for inelastic scattering in the center of mass system is assumed. 2 - Method of solution: The Monte Carlo method with importance sampling technique, splitting and Russian Roulette is used. The neutron attenuation and scattering kinematics is taken into account. 3 - Restrictions on the complexity of the problem: Energy range from 10 KeV to 20 MeV. For the output spectra any bin width is possible. The output spectra are confined to 40 equidistant channels
Measurements of fast neutron spectra in iron, uranium and sodium-iron assemblies
International Nuclear Information System (INIS)
Kappler, F.; Pieroni, N.; Rusch, D.; Schmidt, A.; Wattecamps, E.; Werle, H.
1979-01-01
Spectrum measurements were performed at the fast subcritical facility SUAK to test nuclear data and computer codes used in fast reactor calculations. In order to obtain a specific and quantitative interpretation of discrepancies between measured and calculated spectrum, homogeneous assemblies consisting of single materials were investigated. The leakage spectrum of iron and uranium cylinders was measured by time-of-flight and proportional counters. Time-dependent leakage spectra were measured by a NE 213 liquid scintillator. It was demonstrated that the investigation of time-dependent spectra is a sensitive test of inelastic scattering cross section data. The effect of an interface on fast neutron spectra was also investigated by measuring space dependent spectra across a sodium-iron interface. The measured spectra of these assemblies are suitable for testing the adequacy of computational approximations and cross section data. (author)
International Nuclear Information System (INIS)
Santoro, R.T.; Barnes, J.M.
1983-08-01
Neutron and gamma-ray spectra resulting from the interactions of approx. 14-MeV neutrons in laminated slabs of stainless steel type-304 and borated polyethylene have been calculated using the Monte Carlo code MCNP. The calculated spectra are compared with measured data as a function of slab thickness and material composition and as a function of detector location behind the slabs. Comparisons of the differential energy spectra are made for neutrons with energies above 850 keV and for gamma rays with energies above 750 keV. The measured neutron spectra and those calculated using Monte Carlo methods agree within 5% to 50% depending on the slab thickness and composition and neutron energy. The agreement between the measured and calculated gamma-ray energy spectra is also within this range. The MCNP data are also in favorable agreement with attenuated data calculated previously by discrete ordinates transport methods and the Monte Carlo code SAM-CE
Scattering of 14.6 MeV neutrons from Fe and evidence for structure in the emitted neutron spectra
International Nuclear Information System (INIS)
Gul, K.; Anwar, M.; Ahmad, M.; Saleem, S.M.; Khan, N.A.
1984-06-01
Structure in the spectra of neutrons emitted from iron on bombardment with 14.6 MeV neutrons has been investigated and explained in terms of excitation of levels in iron 56. The energies of scattered neutrons have been measured by the time-of-flight technique based on the associated particle method. The observed excitations have been correlated with the reported levels in a satisfactory manner. Evidence for new excitations at 8.8 +- 0.02, 9.8 +- 0.1, 10.2 +- 0.1, 12.44 +- 0.03 and 12.52 +- 0.03 MeV has been obtained. The excitation of possible components of Ml giant resonance in iron 56 is discussed. (author)
Spectra of neutrons and fusion charged products produced in a dense laser plasma
International Nuclear Information System (INIS)
Burtsev, V.A.; Dyatlov, V.D.; Krzhizhanovskij, R.E.; Levkovskij, A.A.
1977-01-01
The possibility of laser-produced plasma diagnostics has been investigated by measuring spectra of neutrons and alpha particles produced in the T(d,n) 4 He reaction. Using the Monte Carlo method the spectra have been calculated for nine states of the deuterium-tritium plasma with the temperature of 1;5 and 10 keV and the density of 0.2; 1 and 10 g/cm 3 respectively. The initial radius of the target was assumed to be 0.01 cm at the density of 0.2 g/cm 3 . It is shown that the neutron and alpha spectra can serve as plasma diagnostics parameters in laser fusion
International Nuclear Information System (INIS)
Kupchishin, A.A.; Kupchishin, A.I.; Stusik, G.; Omarbekova, Zh.
2001-01-01
Peculiarities of approximation for reactor neutron energy spectra during radiation defects computerized simulation were discussed. Approximation of neutron spectra N(E) was carried out by N(E)=α·exp(-β·E)·sh(γ·E) formula (1), where α, β, γ - approximation coefficients. In the capacity of operating reactor data experimental data on 235 U and 239 Pu were applied. The algorithm was designed, and acting soft ware for spectra parameters calculation was developed. The following values of approximation parameters were obtained: α=80.8; β=0.935;γ=2.04 (for uranium and plutonium these coefficients are less distinguishing). Then with use of formula 1 and α, β, γ coefficients the approximation curves were constructed. These curves satisfactorily describe existing experimental data and allowing to use its for radiation defects simulation in the reactor materials
International Nuclear Information System (INIS)
Huebner, K.; Baetzner, R.; Roos, M.; Robouch, B.V.; Ingrosso, L.; Wurz, H.
1987-08-01
The problem of nuclear emulsion measurements at ASDEX is considered. Besides the application of the VINIA-3DAMC software, this needs a description of the plasma neutron source, a model of the ASDEX structure, and calculation of the response of the nuclear emulsion to the incoming spectral neutron fluence. The latter is essential for comparing the numerical results with measurements at ASDEX. To treat this part, the NEPMC software was developed. The aim of the present work is to demonstrate the feasibility, reliability and usefulness of the method. Therefore simplified treatments for the ASDEX model, the plasma neutron source and the track statistics in the NEPMC software were used. Such calculations are of interest not only for nuclear emulsion measurements as well as any other neutron diagnostics, but also for all problems of neutron shielding for other diagnostics. (orig./GG)
Measurement and Analysis of Neutron Leakage Spectra from Pb and LBE Cylinders with D-T Neutrons
Chen, Size; Gan, Leting; Li, Taosheng; Han, Yuncheng; Liu, Chao; Jiang, Jieqiong; Wu, Yican
2017-09-01
For validating the current evaluated neutron data libraries, neutron leakage spectra from lead and lead bismuth eutectic (LBE) cylinders have been measured using an intense D-T pulsed neutron source with time-of-flight (TOF) method by Institute of Nuclear Energy Safety Technology (INEST), Chinese Academy of Sciences (CAS). The measured leakage spectra have been compared with the calculated ones using Super Monte Carlo Simulation Program for Nuclear and Radiation Process (SuperMC) with the evaluated pointwise data of lead and bismuth processed from ENDF/B-VII.1, JEFF-3.1 and JENDL-4.0 libraries. This work shows that calculations of the three libraries are all generally consistent with the lead experimental result. For LBE experiment, the JEFF-3.1 and JENDL-4.0 calculations both agree well with the measurement. However, the result of ENDF/B-VII.1 fails to fit with the measured data, especially in the energy range of 5.5 and 7 MeV with difference more than 80%. Through sensitivity analysis with partial cross sections of 209Bi in ENDF/B-VII.1 and JEFF, the difference between the measurement and the ENDF/B-VII.1 calculation in LBE experiment is found due to the neutron data of 209Bi.
Study of gamma ray multiplicity spectra for radiative capture of neutrons in 113,115In
International Nuclear Information System (INIS)
Georgiev, G.P.; Fajkov-Stanchik, Kh.; Grigor'ev, Yu.V.; Muradyan, G.V.; Yaneva, N.B.
1997-08-01
Neutron radiative capture measurements were performed for the enriched isotopes 113 In and 115 In on the neutron spectrometer at the Neutron Physics Laboratory of the Joint Institute for Nuclear Research employing the gamma ray multiplicity technique and using a ''Romashka'' multi-sectional 4p detector on the 500 m time base of the IBR-30 booster. The gamma multiplicity spectra of resolved resonances were obtained for the 20-500 eV energy range. The mean gamma ray multiplicity was determined for each resonance. The dependence of the ratio S of the low-energy coincidence multiplicity spectrum to the high-energy coincidence multiplicity spectrum on resonance energy exhibits a non-statistical structure. This structure was found to correlate with the local neutron strength function. (author). 10 refs, 6 figs, 2 tabs
Delayed neutron spectra and their uncertainties in fission product summation calculations
Energy Technology Data Exchange (ETDEWEB)
Miyazono, T.; Sagisaka, M.; Ohta, H.; Oyamatsu, K.; Tamaki, M. [Nagoya Univ. (Japan)
1997-03-01
Uncertainties in delayed neutron summation calculations are evaluated with ENDF/B-VI for 50 fissioning systems. As the first step, uncertainty calculations are performed for the aggregate delayed neutron activity with the same approximate method as proposed previously for the decay heat uncertainty analyses. Typical uncertainty values are about 6-14% for {sup 238}U(F) and about 13-23% for {sup 243}Am(F) at cooling times 0.1-100 (s). These values are typically 2-3 times larger than those in decay heat at the same cooling times. For aggregate delayed neutron spectra, the uncertainties would be larger than those for the delayed neutron activity because much more information about the nuclear structure is still necessary. (author)
Unfolding neutron spectra with BS-TLD system using genetic algorithms
International Nuclear Information System (INIS)
Santos, Joelan A.L.; Silva, Everton R.; Vilela, Eudice C.
2011-01-01
Due to the variability of neutron spectrum within the same environment, it is essential that the spectral distribution as function of energy to be characterized. To perform this task, the neutron spectrometer has a primary role in determining the neutron flux (Φ E (E)). Precise information allows radiological quantities establishment related to that spectrum but it is necessary, however, a series of steps with a spectrometric system that can cover a large interval of energy and whose answer is isotropic. The most widely used for accomplishing this task is the spectrometric Bonner spheres system. One of the biggest problems related to neutron spectrometry is the process of data analysis, known as unfolding. Most of the work undertaken to implement new techniques of this process, using data obtained with the scintillator 6 LiI(I). However, characteristics related to the dead time make it not be so effective when used in high flow neutron fields. An alternative to this problem is the use of thermoluminescent detectors (TLD), but the codes used do not provide a more specific response matrix to unfolding the information obtained through these materials, which makes the development of a specific response matrix important to adequately characterize the response obtained by them. This paper proposes using a technique of artificial intelligence called genetic algorithm, which uses bio-inspired mathematical models and through the implementation of a specific matrix to unfolding data obtained from a combination of TLDs embedded in a system of Bonner spheres, such as thermal neutron detectors, to characterize the neutron spectrum as a function of energy. The results obtained with this method were in accordance with reference spectra, thus enables of this technique to unfolding neutrons spectra with BS-TLD system. (author)
Unfolding neutron spectra with BS-TLD system using genetic algorithms
Energy Technology Data Exchange (ETDEWEB)
Santos, Joelan A.L., E-mail: jasantos@cnen.gov.br [Universidade Federal de Pernambuco (UFPE), Recife, PE (Brazil). Dept. de Energia Nuclear; Centro Regional de Ciencias Nucleares do Nordeste (CRCN-NE/CNEN-PE), Recife, PE (Brazil); Silva, Everton R. [Universidade Federal de Pernambuco (UFPE), Recife, PE (Brazil). Centro de Informatica; Ferreira, Tiago A.E. [Universidade Federal Rural de Pernambuco (UFRPE), Recife, PE (Brazil). Dept. de Estatistica e Informatica; Fonseca, Evaldo S. [Instituto de Radioprotecao e Dosimetria (IRD/CNEN-RJ), Rio de Janeiro, RJ (Brazil); Vilela, Eudice C., E-mail: ecvilela@cnen.gov.br [Centro Regional de Ciencias Nucleares do Nordeste (CRCN-NE/CNEN-PE), Recife, PE (Brazil)
2011-07-01
Due to the variability of neutron spectrum within the same environment, it is essential that the spectral distribution as function of energy to be characterized. To perform this task, the neutron spectrometer has a primary role in determining the neutron flux ({Phi}{sub E}(E)). Precise information allows radiological quantities establishment related to that spectrum but it is necessary, however, a series of steps with a spectrometric system that can cover a large interval of energy and whose answer is isotropic. The most widely used for accomplishing this task is the spectrometric Bonner spheres system. One of the biggest problems related to neutron spectrometry is the process of data analysis, known as unfolding. Most of the work undertaken to implement new techniques of this process, using data obtained with the scintillator {sup 6}LiI(I). However, characteristics related to the dead time make it not be so effective when used in high flow neutron fields. An alternative to this problem is the use of thermoluminescent detectors (TLD), but the codes used do not provide a more specific response matrix to unfolding the information obtained through these materials, which makes the development of a specific response matrix important to adequately characterize the response obtained by them. This paper proposes using a technique of artificial intelligence called genetic algorithm, which uses bio-inspired mathematical models and through the implementation of a specific matrix to unfolding data obtained from a combination of TLDs embedded in a system of Bonner spheres, such as thermal neutron detectors, to characterize the neutron spectrum as a function of energy. The results obtained with this method were in accordance with reference spectra, thus enables of this technique to unfolding neutrons spectra with BS-TLD system. (author)
Energy Technology Data Exchange (ETDEWEB)
Elizalde D, J
1973-07-01
This work consists in determining the fast neutron spectra emitted by a Pu-Be isotopic source. The implemented technique is based in the spectrometry (n, p). This consists in making to fall on a fast neutrons beams (polyenergetic) over a thin film of hydrogenated material, detecting the spectra of emitted protons at a fix angle. The polyethylene film and the used solid state detector are inside of a vacuum chamber. The detector is placed at 30 degree with respect to direction of the incident neutrons beam. The protons spectra is stored in a multichannel. the energy is obtained with the prior calibration of the system. The data processing involves the transformation of the protons spectra observed at the falling on neutrons spectra over the film. The energy of the neutrons is related with that of the protons, according to the collision kinematical equations. The cross section of elastic collision of the neutrons with the hydrogen atoms is obtained from literature. Applying these relations to the observed spectra it is obtained the falling on neutron spectra over the film. (Author)
The LANL/LLNL Program to Measure Prompt Fission Neutron Spectra at LANSCE
Haight, Robert; Wu, Ching Yen; Lee, Hye Young; Taddeucci, Terry; Mosby, Shea; O'Donnell, John; Fotiades, Nikolaos; Devlin, Mattew; Ullmann, John; Nelson, Ronald; Wender, Stephen; White, Morgan; Solomon, Clell; Neudecker, Denise; Talou, Patrick; Rising, Michael; Bucher, Brian; Buckner, Matthew; Henderson, Roger
2015-10-01
Accurate data on the spectrum of neutrons emitted in neutron-induced fission are needed for applications and for a better understanding of the fission process. At LANSCE we have made important progress in understanding systematic uncertainties and in obtaining data for 235U on the low-energy part of the prompt fission neutron spectra (PFNS), a particularly difficult region because down-scattered neutrons go in this direction. We use a double time-of-flight technique to determine energies of incoming and outgoing neutrons. With data acquisition via waveform digitizers, accidental coincidences between fission chamber and neutron detector are measured to high statistical accuracy and then subtracted from measured events. Monte Carlo simulations with high performance computers have proven to be essential in the design to minimize neutron scattering and in calculating detector response. Results from one of three approaches to analyzing the data will be presented. This work is funded by the US Department of Energy, National Nuclear Security Administration and Office of Nuclear Physics.
Simulation of Neutron-Induced Prompt Gamma-ray Spectra Emitted from Fake Tungsten Gold Bar
Energy Technology Data Exchange (ETDEWEB)
Lee, K. M.; Sum, G. M. [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)
2016-10-15
Fake gold bars on the market cannot be identified easily without testing because they have the same appearance as a pure gold bar. A non-destructive monitoring method is needed to avoid the trading of fake gold bars on the market. The ultimate goal of this study is to find a fake gold bar detection method using a PGAA (Prompt Gamma Activation Analysis). Using existing data, the number of neutron capture for gold and tungsten in fake tungsten gold bar was calculated and a Monte Carlo simulation for the prompt neutron-induced gamma-ray spectra was conducted. A simulation for neutron-induced prompt gamma-rays spectra when a neutron beam is irradiated onto pure and fake gold bars was successfully conducted. Through a comparison between the prompt gamma-ray spectra of the pure gold bar and those of the fake gold bar, it was concluded that the observation of prompt high-energy gamma-rays from tungsten or a reduction of prompt gamma-rays from gold can be evidence of a fake gold bar. The possibility for detecting a fake gold bar using a PGAA facility was verified.
Simulation of Neutron-Induced Prompt Gamma-ray Spectra Emitted from Fake Tungsten Gold Bar
International Nuclear Information System (INIS)
Lee, K. M.; Sum, G. M.
2016-01-01
Fake gold bars on the market cannot be identified easily without testing because they have the same appearance as a pure gold bar. A non-destructive monitoring method is needed to avoid the trading of fake gold bars on the market. The ultimate goal of this study is to find a fake gold bar detection method using a PGAA (Prompt Gamma Activation Analysis). Using existing data, the number of neutron capture for gold and tungsten in fake tungsten gold bar was calculated and a Monte Carlo simulation for the prompt neutron-induced gamma-ray spectra was conducted. A simulation for neutron-induced prompt gamma-rays spectra when a neutron beam is irradiated onto pure and fake gold bars was successfully conducted. Through a comparison between the prompt gamma-ray spectra of the pure gold bar and those of the fake gold bar, it was concluded that the observation of prompt high-energy gamma-rays from tungsten or a reduction of prompt gamma-rays from gold can be evidence of a fake gold bar. The possibility for detecting a fake gold bar using a PGAA facility was verified
DEMONR, Monte-Carlo Shielding Calculation for Neutron Flux and Neutron Spectra, Teaching Program
International Nuclear Information System (INIS)
Courtney, J. C.
1987-01-01
1 - Description of problem or function: DEMONR treats the behavior of neutrons in a slab shield. It is frequently used as a teaching tool. 2 - Method of solution: An unbiased Monte Carlo code calculates the number, energy, and direction of neutrons that penetrate or are reflected from a shield. 3 - Restrictions on the complexity of the problem: Only one shield may be used in each problem. The shield material may be a single element or a homogeneous mixture of elements with a single effective atomic weight. Only elastic scattering and neutron capture processes are allowed. The source is a point located on one face of the slab. It provides a cosine distribution of current. Monoenergetic or fission spectrum neutrons may be selected
International Nuclear Information System (INIS)
Smith, A.R.; Schimmerling, W.; Henson, A.M.; Kanstein, L.L.; McCaslin, J.B.; Stephens, L.D.; Thomas, R.H.; Ozawa, J.; Yeater, F.W.
1978-07-01
Helium ions, with an energy of 920 MeV, produced by the 184-inch synchrocyclotron of the Lawrence Berkeley Laboratory are now being used in a pilot series to determine their efficacy in the treatment of tumors of large volume. The techniques for production of the large uniform radiation fields required for these treatments involve the use of beam-limiting collimators and energy degraders. Interaction of the primary beam with these beam components produces secondary charged particles and neutrons. The sources of neutron production in the beam transport system of the alpha-particle beam have been identified and their magnitudes have been determined. Measurements with activation detectors and pulse counters of differing energy responses have been used to determine secondary particle spectra at various locations on the patient table. These spectra are compared to a calculation of neutron production based on best estimates derived from published cross sections. Agreement between the calculated spectra and those derived from experimental measurements is obtained (at the 10 to 20% level) when the presence of charged particles is taken into account. The adsorbed dose in soft tissue is not very sensitive to the shape of the incident neutron energy spectrum, and the values obtained from unfolding the experimental measurements agree with the values obtained from the calculated spectra within the estimated uncertainty of +-25%. These values are about 3 x 10 -3 rad on the beam axis and about 1 x 10 -3 rad at 20 cm or more from the beam axis, per rad deposited by the incident alpha-particle beam. Estimates of upper limit dose to the lens of the eye and red bone marrow are approximately 10 rad and approximately 1 rad, respectively, for a typical treatment plan. The absorbed dose to the lens of the eye is thus well below the threshold value for cataractogenesis estimated for fission neutrons. An upper limit for the risk of leukemia is estimated to be approximately 0.04%
Determination of fast neutrons energy spectra by Monte-Carlo Method
International Nuclear Information System (INIS)
Chetaine, A.
1986-01-01
Two computation codes based on the Monte-Carlo method are established for studying the spectrometry of neutrons with 14 Mev as initial energy. The spectra are determined, on one hand, around a neutron generator Ti-T target and, on the other hand, in a big paraffin cylinder. One code allows to determine the spectrum of neutrons irradiating the sample at various distances from the Ti-T target versus accelerator parameters: high voltage, atomic or molecular nature of deuterons beam, target thickness and materials surrounding the target. The other code determines neutron spectra at various positions inside and outside the 30 x 30 cm paraffin cylinder. The validity of the procedure used in these codes is verified by determining the spectrum of neutrons crossing a big surface, using the procedure in question and using direct simulation method. The biasing procedure used in the two codes permits to have results with good statistics from a reduced number of drawings. 70 figs.; 62 refs.; 1 tab. (author)
Experimental characterization of the neutron spectra generated by a high-energy clinical LINAC
Energy Technology Data Exchange (ETDEWEB)
Amgarou, K., E-mail: khalil.amgarou@uab.e [Institut de Radioprotection et de Surete Nucleaire (IRSN), Laboratoire de Metrologie et de Dosimetrie des Neutrons, F-13115 Saint Paul-Lez-Durance (France); Lacoste, V.; Martin, A. [Institut de Radioprotection et de Surete Nucleaire (IRSN), Laboratoire de Metrologie et de Dosimetrie des Neutrons, F-13115 Saint Paul-Lez-Durance (France)
2011-02-11
The production of unwanted neutrons by electron linear accelerators (LINACs) has attracted a special attention since the early 50s. The renewed interest in this topic during the last years is due mainly to the increased use of such machines in radiotherapy. Specially, in most of developing countries where many old teletherapy irradiators, based on {sup 60}Co and {sup 137}Cs radioactive sources, are being replaced with new LINAC units. The main objective of this work is to report the results of an experimental characterization of the neutron spectra generated by a high-energy clinical LINAC. Measurements were carried out, considering four irradiation configurations, by means of our recently developed passive Bonner sphere spectrometer (BSS) using pure gold activation foils as central detectors. This system offers the possibility to measure neutrons over a wide energy range (from thermal up to a few MeV) at pulsed, intense and complex mixed n-{gamma} fields. A two-step unfolding method that combines the NUBAY and MAXED codes was applied to derive the final neutron spectra as well as their associated integral quantities (in terms of total neutron fluence and ambient dose equivalent rates) and fluence-averaged energies.
Baseline distortion effect on gamma-ray pulse-height spectra in neutron capture experiments
International Nuclear Information System (INIS)
Laptev, A.; Harada, H.; Nakamura, S.; Hori, J.; Igashira, M.; Ohsaki, T.; Ohgama, K.
2005-01-01
A baseline distortion effect due to gamma-flash at neutron time-of-flight measurement using a pulse neutron source has been investigated. Pulses from C 6 D 6 detectors accumulated by flash-ADC were processed with both standard analog-to-digital converter (ADC) and flash-ADC operational modes. A correction factor of gamma-ray yields, due to baseline shift, was quantitatively obtained by comparing the pulse height spectra of the two data-taking modes. The magnitude of the correction factor depends on the time after gamma-flash and has complex time dependence with a changing sign
Quality factor calculations for neutron spectra below 4 MeV
International Nuclear Information System (INIS)
Borak, T.B.; Stinchcomb, T.G.
1979-01-01
A method is described for computing the distribution of absorbed dose, D(L), as a function of linear energy transfer, L, for any neutron spectrum with energies below 4 MeV. The results are used to determine the average quality factor for two distinctly different neutron spectra using the ICRP recommended values of the quality factor, Q(L). A comparison is made between the calculations and measurements of D(L) using a spherical tissue equivalent proportional counter. Heavy ion recoil contributions to the average quality factor are examined in detail. (author)
Measuring thermal neutron spectra of RIEN-1 reactor with a chopper
International Nuclear Information System (INIS)
Jesus Vilar, G. de.
1977-03-01
The setting up of a time-of-flight spectrometer (Fermi Chopper) and its use in measurements of thermal neutron spectra in the irradiation channels of the Argonaut Reactor(Instituto de Engenharia Nuclear, Brazil), is described. These distributions are obtained using a multichannel analyser with the necessary corrections being made for counting losses in the analyser, dectector efficiency experimental resolution and chopper transmission function. The results obtained show that the thermal neutron flux emerging from the canal J-9 can be approximately described by a Maxwellian distribution with and associated characteristic temperature fo 430+-30 0 K [pt
International Nuclear Information System (INIS)
Chatillon, A.; Belier, G.; Granier, T.; Laurent, B.; Morillon, B.; Taieb, J.; Haight, R.C.; Devlin, M.; Nelson, R.O.; Noda, R.S.; O'Donnell, J.M.
2014-01-01
Prompt fission neutron spectra in the neutron-induced fission of "2"3"9Pu have been measured for incident neutron energies from 1 to 200 MeV at the Los Alamos Neutron Science Center. Mean energies deduced from the prompt fission neutron spectra (PFNS) lead to the observation of the opening of the second chance fission at 7 MeV and to indications for the openings of fission channels of third and fourth chances. Moreover, the general trend of the measured PFNS is well reproduced by the different models. The comparison between data and models presents, however, two discrepancies. First, the prompt neutron mean energy seems constant for neutron energy, at least up to 7 MeV, whereas in the theoretical calculations it is continuously increasing. Second, data disagree with models on the shape of the high energy part of the PFNS, where our data suggest a softer spectrum than the predictions. (authors)
MADNIX a code to calculate prompt fission neutron spectra and average prompt neutron multiplicities
International Nuclear Information System (INIS)
Merchant, A.C.
1986-03-01
A code has been written and tested on the CDC Cyber-170 to calculate the prompt fission neutron spectrum, N(E), as a function of both the fissioning nucleus and its excitation energy. In this note a brief description of the underlying physical principles involved and a detailed explanation of the required input data (together with a sample output for the fission of 235 U induced by 14 MeV neutrons) are presented. Weisskopf's standard nuclear evaporation theory provides the basis for the calculation. Two important refinements are that the distribution of fission-fragment residual nuclear temperature and the cooling of the fragments as neutrons are emitted approximately taken into account, and also the energy dependence of the cross section for the inverse process of compound nucleus formation is included. This approach is then used to calculate the average number of prompt neutrons emitted per fission, v-bar p . At high excitation energies, where fission is still possible after neutron emission, the consequences of the competition between first, second and third chance fission on N(E) and v-bar p are calculated. Excellent agreement with all the examples given in the original work of Madland and Nix is obtained. (author) [pt
Energy Technology Data Exchange (ETDEWEB)
Howell, Rebecca M., E-mail: rhowell@mdanderson.org [Department of Radiation Physics, The University of Texas M. D. Anderson Cancer Center, Houston, Texas (United States); Burgett, Eric A.; Isaacs, Daniel [Department of Nuclear Engineering, Idaho State University, Pocatello, Idaho (United States); Price Hedrick, Samantha G.; Reilly, Michael P.; Rankine, Leith J.; Grantham, Kevin K.; Perkins, Stephanie; Klein, Eric E. [Department of Radiation Oncology, Washington University, St. Louis, Missouri (United States)
2016-05-01
Purpose: To measure, in the setting of typical passively scattered proton craniospinal irradiation (CSI) treatment, the secondary neutron spectra, and use these spectra to calculate dose equivalents for both internal and external neutrons delivered via a Mevion single-room compact proton system. Methods and Materials: Secondary neutron spectra were measured using extended-range Bonner spheres for whole brain, upper spine, and lower spine proton fields. The detector used can discriminate neutrons over the entire range of the energy spectrum encountered in proton therapy. To separately assess internally and externally generated neutrons, each of the fields was delivered with and without a phantom. Average neutron energy, total neutron fluence, and ambient dose equivalent [H* (10)] were calculated for each spectrum. Neutron dose equivalents as a function of depth were estimated by applying published neutron depth–dose data to in-air H* (10) values. Results: For CSI fields, neutron spectra were similar, with a high-energy direct neutron peak, an evaporation peak, a thermal peak, and an intermediate continuum between the evaporation and thermal peaks. Neutrons in the evaporation peak made the largest contribution to dose equivalent. Internal neutrons had a very low to negligible contribution to dose equivalent compared with external neutrons, largely attributed to the measurement location being far outside the primary proton beam. Average energies ranged from 8.6 to 14.5 MeV, whereas fluences ranged from 6.91 × 10{sup 6} to 1.04 × 10{sup 7} n/cm{sup 2}/Gy, and H* (10) ranged from 2.27 to 3.92 mSv/Gy. Conclusions: For CSI treatments delivered with a Mevion single-gantry proton therapy system, we found measured neutron dose was consistent with dose equivalents reported for CSI with other proton beamlines.
Neutron spectra and level density parameters from 16O + 12C fusion reaction
International Nuclear Information System (INIS)
Kasagi, J.; Remington, B.; Galonsky, A.; Haas, F.; Racca, R.; Prosser, F.W.
1985-01-01
Residues following 16 O + 12 C fusion were identified by their characteristic γ-rays. For several transitions in 23 Mg, 25 Mg, and 26 Al coincident neutron spectra were measured at six angles. Through use of the evaporation code CASCADE, comparisons were made of these spectra with predictions of the statistical model at five 16 O projectile energies between 43.2 and 56.0 MeV. The results require an excitation energy dependence for the effective radius parameter r 0 which determines the spin cutoff factor
Multi-Group Covariance Data Generation from Continuous-Energy Monte Carlo Transport Calculations
International Nuclear Information System (INIS)
Lee, Dong Hyuk; Shim, Hyung Jin
2015-01-01
The sensitivity and uncertainty (S/U) methodology in deterministic tools has been utilized for quantifying uncertainties of nuclear design parameters induced by those of nuclear data. The S/U analyses which are based on multi-group cross sections can be conducted by an simple error propagation formula with the sensitivities of nuclear design parameters to multi-group cross sections and the covariance of multi-group cross section. The multi-group covariance data required for S/U analysis have been produced by nuclear data processing codes such as ERRORJ or PUFF from the covariance data in evaluated nuclear data files. However in the existing nuclear data processing codes, an asymptotic neutron flux energy spectrum, not the exact one, has been applied to the multi-group covariance generation since the flux spectrum is unknown before the neutron transport calculation. It can cause an inconsistency between the sensitivity profiles and the covariance data of multi-group cross section especially in resolved resonance energy region, because the sensitivities we usually use are resonance self-shielded while the multi-group cross sections produced from an asymptotic flux spectrum are infinitely-diluted. In order to calculate the multi-group covariance estimation in the ongoing MC simulation, mathematical derivations for converting the double integration equation into a single one by utilizing sampling method have been introduced along with the procedure of multi-group covariance tally
International Nuclear Information System (INIS)
Sekimoto, H.
1987-01-01
The kerma heat production density, tritum production density, and dose in a lithium-fluoride pile with a deuterium-tritum neutron source were calculated with a data processing code, UFO, from the pulse height distribution of a miniature NE213 neutron spectrometer, and compared with the values calculated with a Monte Carlo code, MORSE-CV. Both the UFO and MORSE-CV values agreed with the statistical error (less than 6%) of the MORSE-CV calculations, except for the outer-most point in the pile. The MORSE-CV values were slightly smaller than the UFO values for almost all cases, and this tendency increased with increasing distance from the neutron source
Study of spectral response of a neutron filter. Design of a method to adjust spectra
International Nuclear Information System (INIS)
Colomb-Dolci, F.
1999-02-01
The first part of this thesis describes an experimental method which intends to determine a neutron spectrum in the epithermal range [1 eV -10 keV]. Based on measurements of reaction rates provided by activation foils, it gives flux level in each energy range corresponding to each probe. This method can be used in any reactor location or in a neutron beam. It can determine scepter on eight energy groups, five groups in the epithermal range. The second part of this thesis presents a study of an epithermal neutron beam design, in the frame of Neutron Capture Therapy. A beam tube was specially built to test filters made up of different materials. Its geometry was designed to favour epithermal neutron crossing and to cut thermal and fast neutrons. A code scheme was validated to simulate the device response with a Monte Carlo code. Measurements were made at ISIS reactor and experimental spectra were compared to calculated ones. This validated code scheme was used to simulate different materials usable as shields in the tube. A study of these shields is presented at the end of this thesis. (author)
Neutron Energy Spectra and Yields from the 7Li(p,n) Reaction for Nuclear Astrophysics
Tessler, M.; Friedman, M.; Schmidt, S.; Shor, A.; Berkovits, D.; Cohen, D.; Feinberg, G.; Fiebiger, S.; Krása, A.; Paul, M.; Plag, R.; Plompen, A.; Reifarth, R.
2016-01-01
Neutrons produced by the 7Li(p, n)7Be reaction close to threshold are widely used to measure the cross section of s-process nucleosynthesis reactions. While experiments have been performed so far with Van de Graaff accelerators, the use of RF accelerators with higher intensities is planned to enable investigations on radioactive isotopes. In parallel, high-power Li targets for the production of high-intensity neutrons at stellar energies are developed at Goethe University (Frankfurt, Germany) and SARAF (Soreq NRC, Israel). However, such setups pose severe challenges for the measurement of the proton beam intensity or the neutron fluence. In order to develop appropriate methods, we studied in detail the neutron energy distribution and intensity produced by the thick-target 7Li(p,n)7Be reaction and compared them to state-of- the-art simulation codes. Measurements were performed with the bunched and chopped proton beam at the Van de Graaff facility of the Institute for Reference Materials and Measurements (IRMM) using the time-of-flight (TOF) technique with thin (1/8") and thick (1") detectors. The importance of detailed simulations of the detector structure and geometry for the conversion of TOF to a neutron energy is stressed. The measured neutron spectra are consistent with those previously reported and agree well with Monte Carlo simulations that include experimentally determined 7Li(p,n) cross sections, two-body kinematics and proton energy loss in the Li-target.
Cross sections and differential spectra for reactions of 2-20 MeV neutrons on /sup nat/Cr
International Nuclear Information System (INIS)
Blann, M.; Komoto, T.T.
1988-01-01
This report summarizes product yields, secondary n,p and α spectra, and γ-ray spectra calculated for incident neutrons of 2 to 20 MeV on /sup nat/Cr targets. Results are all from the code ALICE, using the version ALISO which does weighting of results for targets which are a mix of isotopes. Where natural isotopic targets are involved, yields and n,p,α spectra will be reported weighted over isotopic yields. Gamma-ray spectra, however, will be reported for the most abundant isotope. We present product yields versus incident neutron energy, n,p,α spectra versus incident neutron energy, and calculated γ-ray spectra
Measurement of D-T neutron penetration probability spectra for iron ball shell systems
International Nuclear Information System (INIS)
Duan Shaojie
1998-06-01
The D-T neutron penetration probability spectra are measured for iron ball shell systems of the series of samples used in the experiments, and the penetration curves are presented. As the detector is near to samples, the measured results being approximately corrected are compared with those in the literature, and it is shown that the former is compatible with the latter in the range of the experimental error
International Nuclear Information System (INIS)
Urabe, Itsumasa
1986-01-01
This is a report of the symposium on measurements of neutron energy spectra using recoil proton proportional counters held at the Research Reactor Institute of Kyoto University on January 27 in 1986. An energy resolution, wall effects of response functions, n · γ discrimination methods and other fundamental properties of recoil proton counters are discussed for a new development of an application of this counter. (author)
Inelastic neutron scattering studies of the phonon spectra of Chevrel-phase superconductors
International Nuclear Information System (INIS)
Bader, S.D.; Sinha, S.K.; Shelton, R.N.
1976-01-01
Phonon spectra are obtained using inelastic neutron scattering by polycrystals of the Chevrel-phase superconductors SnMo 6 S 8 , PbMo 6 S 8 , Mo 6 Se 8 , and Pb 1 . 2 Mo 6 Se 8 . Modes associated primarily with Sn (or Pb) atomic displacements are clearly identified. Acoustic softening on cooling is noted for SnMo 6 S 8 . Anharmonicity and the superconductivity are discussed utilizing the molecular-crystal concept
Calculations of the spectra of fast neutrons in iron spheres using the vitamin-C file
International Nuclear Information System (INIS)
Ahmed, F.; Aizawa, O.; Kadotani, H.
1984-01-01
Steady-state space-dependent fast neutron angular and scalar spectra and total flux in various iron spheres have been calculated using the one-dimensional discrete ordinate transport code ANISN and Vitamin-C nuclear data file. The results have been used to study the question of establishment of equilibrium and of an associated fast neutron diffusion length in iron. The authors find that true equilibrium conditions are not established even inside a 3-m-radius iron sphere. However, from the study of spatial decay of total flux, one can obtain the value of the fast neutron diffusion length in iron, which in the present case is found to be 24.4 cm
Analysis of accelerator based neutron spectra for BNCT using proton recoil spectroscopy
International Nuclear Information System (INIS)
Wielopolski, L.; Ludewig, H.; Powell, J.R.; Raparia, D.; Alessi, J.G.; Lowenstein, D.I.
1998-01-01
Boron Neutron Capture Therapy (BNCT) is a promising binary treatment modality for high-grade primary brain tumors (glioblastoma multiforme, GM) and other cancers. BNCT employs a boron-10 containing compound that preferentially accumulates in the cancer cells in the brain. Upon neutron capture by 10 B energetic alpha particles and triton released at the absorption site kill the cancer cell. In order to gain penetration depth in the brain Fairchild proposed, for this purpose, the use of energetic epithermal neutrons at about 10 keV. Phase I/II clinical trials of BNCT for GM are underway at the Brookhaven Medical Research Reactor (BMRR) and at the MIT Reactor, using these nuclear reactors as the source for epithermal neutrons. In light of the limitations of new reactor installations, e.g. cost, safety and licensing, and limited capability for modulating the reactor based neutron beam energy spectra alternative neutron sources are being contemplated for wider implementation of this modality in a hospital environment. For example, accelerator based neutron sources offer the possibility of tailoring the neutron beams, in terms of improved depth-dose distributions, to the individual and offer, with relative ease, the capability of modifying the neutron beam energy and port size. In previous work new concepts for compact accelerator/target configuration were published. In this work, using the Van de Graaff accelerator the authors have explored different materials for filtering and reflecting neutron beams produced by irradiating a thick Li target with 1.8 to 2.5 MeV proton beams. However, since the yield and the maximum neutron energy emerging from the Li-7(p,n)Be-7 reaction increase with increase in the proton beam energy, there is a need for optimization of the proton energy versus filter and shielding requirements to obtain the desired epithermal neutron beam. The MCNP-4A computer code was used for the initial design studies that were verified with benchmark experiments
Features of the neutron spectra accompanying the fission of actinide nuclei
International Nuclear Information System (INIS)
Lovchikova, G.N.; Trufanov, A.M.; Svirin, M.I.; Polyakov, A.V.; Vinogradov, V.A.; Dmitriev, V.D.; Boykov, G.S.
2000-01-01
The spectra of fission neutrons from 238 U are measured by the time-of-flight technique at incident-neutron energies E n = 5.0 and 13.2 MeV. The data are compared with those obtained in the previous studies for 232 Th, 235,238 U, 237 Np at E n = 2.9 and 14.7 MeV; for 232 Th at E n = 14.6 and 17.7 MeV; for 238 U at 16.0 and 17.7 MeV. An excess of soft neutrons, which is observed in comparing experimental spectra for E n 13.2, 14.7, 16.0 and 17.7 MeV with the results of traditional theoretical calculations, is reproduced fairly well under the assumption that, at high excitation energies of a compound system, some part of post-fission neutrons can be emitted by nonaccelerated fragments [ru
Calculation of neutron spectra for a 252Cf transport cask using ANISN running on a PC
International Nuclear Information System (INIS)
West, L.; Akin, B.P.; Lemley, E.C.
1995-01-01
Neutron spectra have been calculated using the ANISN one-dimensional discrete ordinates code for the case of a 152 Cf source in a transport cask of a particular design. All computations were done on personal computers (PCs) (mostly 486 models) with the ANISN-ORNL (486 version) computer code. With a source of 252 Cf fission neutrons, the neutron flux spectrum in the cask cannot be characterized as open-quotes moderated.close quotes Concern about an appropriate choice for the cross-section data set has led to a comparison, for this application, of three different cross-section libraries: DABL, HILO, and BUGLE-80. Although the cross-section sets were not originally designed for PC use, the libraries have been successfully employed for PC computations. Work with yet another data library, BUGLE-93, is incomplete at this stage. From neutron flux spectra on the surface of the cask, personnel dosimetric quantities (such as dose equivalent) have been determined for the DABL, HILO, and BUGLE-80 ANISN calculations
Neutron and gamma-ray spectra of {sup 239}PuBe and {sup 241}AmBe
Energy Technology Data Exchange (ETDEWEB)
Vega-Carrillo, H.R. E-mail: rvega@cantera.reduaz.mx; Manzanares-Acuna, Eduardo; Becerra-Ferreiro, A.M.; Carrillo-Nunez, Aureliano
2002-08-01
Neutron and gamma-ray spectra of {sup 239}PuBe and {sup 241}AmBe were measured and their dosimetric features were calculated. Neutron spectra were measured using a multisphere neutron spectrometer with a {sup 6}LiI(Eu) scintillator. The {sup 239}PuBe neutron spectrum was measured in an open environment, while the {sup 241}AmBe neutron spectrum was measured in a closed environment. Gamma-ray spectra were measured using a NaI(Tl) scintillator using the same experimental conditions for both sources. The effect of measuring conditions for the {sup 241}AmBe neutron spectrum indicates the presence of epithermal and thermal neutrons. The low-resolution neutron spectra obtained with the multisphere spectrometer allows one to calculate the dosimetric features of neutron sources. At 100 cm both sources produce approximately the same count rate as that of the 4.4 MeV gamma-ray per unit of alpha emitter activity.
International Nuclear Information System (INIS)
Ortiz R, J.M.; Martinez B, M.R.; Arteaga A, T.; Vega C, H.R.; Hernandez D, V.M.; Manzanares A, E.
2005-01-01
The artificial neural networks (RN) have been used successfully to solve a wide variety of problems. However to determine an appropriate set of values of the structural parameters and of learning of these, it continues being even a difficult task. Contrary to previous works, here a set of neural networks is designed to reconstruct neutron spectra starting from the counting rates coming from the detectors of the Bonner spheres system, using a systematic and experimental strategy for the robust design of multilayer neural networks of the feed forward type of inverse propagation. The robust design is formulated as a design problem of Taguchi parameters. It was selected a set of 53 neutron spectra, compiled by the International Atomic Energy Agency, the counting rates were calculated that would take place in a Bonner spheres system, the set was arranged according to the wave form of those spectra. With these data and applying the Taguchi methodology to determine the best parameters of the network topology, it was trained and it proved the same one with the spectra. (Author)
On the convergence of multigroup discrete-ordinates approximations
International Nuclear Information System (INIS)
Victory, H.D. Jr.; Allen, E.J.; Ganguly, K.
1987-01-01
Our analysis is divided into two distinct parts which we label for convenience as Part A and Part B. In Part A, we demonstrate that the multigroup discrete-ordinates approximations are well-defined and converge to the exact transport solution in any subcritical setting. For the most part, we focus on transport in two-dimensional Cartesian geometry. A Nystroem technique is used to extend the discrete ordinates multigroup approximates to all values of the angular and energy variables. Such an extension enables us to employ collectively compact operator theory to deduce stability and convergence of the approximates. In Part B, we perform a thorough convergence analysis for the multigroup discrete-ordinates method for an anisotropically-scattering subcritical medium in slab geometry. The diamond-difference and step-characteristic spatial approximation methods are each studied. The multigroup neutron fluxes are shown to converge in a Banach space setting under realistic smoothness conditions on the solution. This is the first thorough convergence analysis for the fully-discretized multigroup neutron transport equations
FINELM: a multigroup finite element diffusion code. Part II
International Nuclear Information System (INIS)
Davierwalla, D.M.
1981-05-01
The author presents the axisymmetric case in cylindrical coordinates for the finite element multigroup neutron diffusion code, FINELM. The numerical acceleration schemes incorporated viz. the Lebedev extrapolations and the coarse mesh rebalancing, space collapsing, are discussed. A few benchmark computations are presented as validation of the code. (Auth.)
Calculation of multigroup reaction rates for the Ghana Research ...
African Journals Online (AJOL)
The discrete ordinate spatial model, which pro-vides solution to the differential form of the transport equation by the Carlson-SN (N=4) approach was adopted to solve the Ludwig-Boltzmann multigroup neutron transport equation for this analysis. The results show that for any fissile resonance absorber, the reaction rates ...
Neutron reference spectra measurements with the Bonner multi-spheres spectrometer
International Nuclear Information System (INIS)
Lemos Junior, Roberto Mendonca de
2004-01-01
This paper aims to define a procedure to use the Bonner Multisphere Spectrometer with a 6 LiI(Eu) detector in order to determine of neutron spectra. It was measured 238 PuBe spectra and same of reference ( 241 AmBe, 252 Cf e 252 Cf+D 2 O) published in ISO 8529-1 (2001) Norm. The data were processed by a computer program (BUNKI), which presents the results in neutrons energy fluency. Each input parameter of the program was studied in order to establish their influence in the adjustment result. The environment dose equivalent rate obtained placing the detector 1 m from the 241 AmBe source was 122 ± 4 μSv/h with 7% of uncertainty and 95% of confidence level. The procedure established in this work was tested with the 238 PuBe spectrum, obtaining an environment dose equivalent rate of 286 ± 9 μSv/h, 8% lower than the value measured experimentally used as reference. Through this procedure will be possible to measure neutron spectra in different work places where neutrons sources are used. Knowing these spectra, it will be possible to evaluate which area monitors, are more suitable, as well as, to study better the response of individual neutron monitors, as for instance, to obtain a conversion coefficient more appropriate to the albedo dosimeter used in different work places. As the measurements need a long time to be accomplished, the work optimization is fundamental to reduce the exposing time of the Bonner spectrometer operator. For this reason, an important parameter examined in this paper was the possibility of reducing the number of spheres used during the measurement without changing the final result. Considering the radiation protection standards, this parameter has a huge importance when the measurements are performed in work places where the neutron fluency and gamma rate offer risks to the operator's health, as for instance, in nuclear centrals. Studying this parameter, it was possible to conclude that removing the 20,32 cm diameter sphere it will be
The optimization of gamma spectra processing in prompt gamma neutron activation analysis (PGNAA)
Energy Technology Data Exchange (ETDEWEB)
Pinault, Jean-Louis [IAEA Expert, 96 rue du Port David, 45370 Dry (France)], E-mail: jeanlouis_pinault@hotmail.fr; Solis, Jose [Instituto Peruano de Energia Nuclear, Av. Canada No. 1470, San Borja, Lima 41 (Peru)
2009-04-15
The uncertainty of the elemental analysis is one of the major factors governing the utility of on-line Prompt Gamma Neutron Activation Analysis (PGNAA) in the blending and sorting of bulk materials. In this paper, a general method applicable to Gamma spectra processing is presented and applied to PGNAA in mineral industry. Based on the Fourier transform of spectra and their de-correlation in the Fourier space (the improvement of the conditioning of the correlation matrix), processing of overlapping of characteristic peaks minimizes the propagation of random errors, which optimizes the accuracy and decreases the detection limits of elemental analyses. In comparison with classical methods based on the linear combinations of relevant regions of spectra the improvement may be considerable, especially when several elements are interfering. The method is applied to four case stories covering both borehole logging and on-line analysis on conveyor belt of raw materials.
International Nuclear Information System (INIS)
Kelly, J.G.; Vehar, D.W.
1987-12-01
Neutron spectra have been measured by the foil-activation method in 13 different environments in and around the Sandia Pulsed Reactor, the White Sands Missile Range Fast Burst Reactor, and the Sandia Annular Core Research Reactor. The spectra were obtained by using the SANDII code in a manner that was not dependent on the initial trial. This altered technique is better suited for the determination of spectra in environments that are difficult to predict by calculation, and it tends to reveal features that may be biased out by the use of standard trial-dependent methods. For some of the configurations, studies have also been made of how well the solution is determined in each energy region. The experimental methods and the techniques used in the analyses are thoroughly explained. 34 refs., 51 figs., 40 tabs
Spectra and neutron dose of an 18 MV Linac using two geometric models of the head
International Nuclear Information System (INIS)
Barrera, M. T.; Pino, F.; Barros, H.; Sajo-Bohus, L.; Davila, J.; Salcedo, E.; Vega C, H. R.; Benites R, J. L.
2015-10-01
Full text: Using the Monte Carlo method, by MCNP5 code, simulations were performed with different source terms and 2 geometric models of the head to obtain spectra in energy, flow and doses of photo-neutrons at different positions on the stretcher and in the radiotherapy room. The simplest model was a spherical shell of tungsten; the second was the complete model of a heterogeneous head of an accelerator Varian ix. In both models Tosi function was used as a source term. In addition, for the second model Sheikh-Bagheri distribution was used for photons and photo-neutrons were generated. Also in both models the radiotherapy room of Gurve group of the Teaching Medical Center La Trinidad was included, which is equipped with an accelerator Varian Clinic 2100. In this Center passive detectors PADC (Cr-39) were irradiated with neutron converters, with 18 MeV photons radiation. The measured neutron flow was compared with that obtained with Monte Carlo calculations. The Monte Carlo flows are similar to those measured at the isocenter. The simplest model underestimates the neutron flow compared with the calculated flows with the heterogeneous model of the head. (Author)
International Nuclear Information System (INIS)
Kim, Bong Hwan
2006-01-01
Neutron field spectrometry using multi spheres such as Bonner Spheres (BS) has been almost essential in radiation protection dosimetry for a long time at workplace in spite of poor energy resolution because it is not asking the fine energy resolution but requiring easy operation and measurement performance over a wide range of energy interested. KAERI has developed and used extended BS system based on a LiI(Eu) scintillator as the representative neutron spectrometry system for workplace monitoring as well as for the quantification of neutron calibration fields such as those recommended by ISO 8529. Major topics in using BS are how close the unfolded spectra is the real one and to minimize the interference of gamma radiation in neutron/gamma mixed fields in case of active instrument such as a BS with a LiI(Eu) scintillator. The former is related with choosing a priori information when unfolding the measured data and the latter is depend on how to discriminate it in intense gamma radiation fields. Influence of a priori information in unfolding and effect of counting loss due to pile-up of signals for the KAERI BS system were investigated analyzing the spectral measurement results of Scattered Neutron Calibration Fields (SNCF)
International Nuclear Information System (INIS)
Broecker, B.; Clausen, K.; Schneider-Kuehnle, P.; Weinert, M.
1975-01-01
An experiment to measure the radiation transport originating from a 14-MeV neutron source in liquid nitrogen and liquid air is presented. Neutron and gamma-ray spectra were measured with a proton-recoil NE 213 scintillator and with four spherical proportional counters in a tank filled with liquid nitrogen or liquid air. The neutron spectra cover the energy range of 20 keV to 18 MeV. The source-detector separation varies in the liquid medium between 60 and 240 cm. The experimental setup is briefly described and the errors are estimated. (2 tables, 9 figures) (auth)
The effect of the neutron spectra unfolding method on the fast neutron dose determination
International Nuclear Information System (INIS)
Marinkovic, P.; Zavaljevski, N.
1992-01-01
Based on Shanon's information theory, a new unfolding method which gives non-negative spectrum values and a relatively low variance, is proposed, and a numerical code suitable for application in fast neutron spectroscopy based on proton recoil is developed. The principles of maximum entropy and maximum likelihood are jointly applied. According to the principle of maximum likelihood, the distribution functions around the mean value of the counts in the MCA channels are assumed to be Gaussians. The Lagrange parameter method is applied in the search for an optimal non-negative solution. The nonlinear system of equations is solved using the gradient and Newton iterative algorithms. (orig.)
The effect of the neutron spectra unfolding method on the fast neutron dose determination
International Nuclear Information System (INIS)
Marinkovic, P.; Avdic, S.; Pesic, M.; Zavaljevski, N
1992-09-01
Based on Shanon's information theory, a new unfolding method which gives non-negative spectrum values and a relatively low variance, is proposed, and a numerical code suitable for application in fast neutron spectroscopy based on proton recoil is developed. The principles of maximum entropy and maximum likelihood are jointly applied. According to the principle of maximum likelihood, the distribution functions around the mean value of the counts in the MCA channels are assumed to be Gaussians. The Lagrange parameter method is applied in the search for an optimal non-negative solution. The nonlinear system of equations is solved using the gradient and Newton iterative algorithms. (author)
Multi-group diffusion perturbation calculation code. PERKY (2002)
Energy Technology Data Exchange (ETDEWEB)
Iijima, Susumu; Okajima, Shigeaki [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment
2002-12-01
Perturbation calculation code based on the diffusion theory ''PERKY'' is designed for nuclear characteristic analyses of fast reactor. The code calculates reactivity worth on the multi-group diffusion perturbation theory in two or three dimensional core model and kinetics parameters such as effective delayed neutron fraction, prompt neutron lifetime and absolute reactivity scale factor ({rho}{sub 0} {delta}k/k) for FCA experiments. (author)
International Nuclear Information System (INIS)
Arteaga A, T.; Ortiz R, J.M.; Vega C, H.R.; Hernandez D, V.M.; Manzanares A, E.; Mercado S, G.A.
2006-01-01
People that live in high places respect to the sea level, in latitudes far from the equator or that they travel by plane, they are exposed to atmospheres of high radiation generated by the cosmic rays. Another atmosphere with radiation is the medical equipment, particle accelerators and nuclear reactors. The evaluation of the biological risk for neutron radiation requires an appropriate and sure dosimetry. A commonly used system is the Bonner Sphere Spectrometer (EEB) with the purpose of reconstructing the spectrum that is important because the equivalent dose for neutrons depends strongly on its energy. The count rates obtained in each sphere are treated, in most of the cases, for iterative methods, Monte Carlo or Maximum Entropy. Each one of them has difficulties that it motivates to the development of complementary procedures. Recently it has been used Artificial Neural Networks, ANN) and not yet conclusive results have been obtained. In this work it was designed an ANN to obtain the neutron energy spectrum neutrons starting from the counting rate of count of an EEB. The ANN was trained with 129 reference spectra obtained of the IAEA (1990, 2001), 24 were built as defined energy, including isotopic sources of neutrons of reference and operational, of accelerators, reactors, mathematical functions, and of defined energy with several peaks. The spectrum was transformed from lethargy units to energy and were reaccommodated in 31 energies using the Monte Carlo code 4C. The reaccommodated spectra and the response matrix UTA4 were used to calculate the prospective count rates in the EEB. These rates were used as entrance and its respective spectrum was used as output during the net training. The net design is Retropropagation type with 5 layers of 7, 140, 140, 140 and 31 neurons, transfer function logsig, tansig, logsig, logsig, logsig respectively. Training algorithm, traingdx. After the training, the net was proven with a group of training spectra and others that
Unfolding neutron spectra obtained from BS–TLD system using genetic algorithm
International Nuclear Information System (INIS)
Santos, J.A.L.; Silva, E.R.; Ferreira, T.A.E; Vilela, E.C.
2012-01-01
Due to the variability of neutron spectrum within the same environment, it is essential that the spectral distribution as a function of energy should be characterized. The precise information allows radiological quantities establishment related to that spectrum, but it is necessary that a spectrometric system covers a large interval of energy and an unfolding process is appropriate. This paper proposes use of a technique of Artificial Intelligence (AI) called genetic algorithm (GA), which uses bio-inspired mathematical models with the implementation of a specific matrix to unfolding data obtained from a combination of TLDs embedded in a BS system to characterize the neutron spectrum as a function of energy. The results obtained with this method were in accordance with reference spectra, thus enabling this technique to unfold neutron spectra with the BS–TLD system. - Highlights: ► The unfolding code used the artificial intelligence technique called genetic algorithms. ► A response matrix specific to the unfolding data obtained with the BS–TLD system is used by the AGLN. ► The observed results demonstrate the potential use of genetic algorithms in solving complex nuclear problems.
Review of multigroup nuclear cross-section processing
Energy Technology Data Exchange (ETDEWEB)
Trubey, D.K.; Hendrickson, H.R. (comps.)
1978-10-01
These proceedings consist of 18 papers given at a seminar--workshop on ''Multigroup Nuclear Cross-Section Processing'' held at Oak Ridge, Tennessee, March 14--16, 1978. The papers describe various computer code systems and computing algorithms for producing multigroup neutron and gamma-ray cross sections from evaluated data, and experience with several reference data libraries. Separate abstracts were prepared for 13 of the papers. The remaining five have already been cited in ERA, and may be located by referring to the entry CONF-780334-- in the Report Number Index. (RWR)
Analysis of MCNP simulated gamma spectra of CdTe detectors for boron neutron capture therapy.
Winkler, Alexander; Koivunoro, Hanna; Savolainen, Sauli
2017-06-01
The next step in the boron neutron capture therapy (BNCT) is the real time imaging of the boron concentration in healthy and tumor tissue. Monte Carlo simulations are employed to predict the detector response required to realize single-photon emission computed tomography in BNCT, but have failed to correctly resemble measured data for cadmium telluride detectors. In this study we have tested the gamma production cross-section data tables of commonly used libraries in the Monte Carlo code MCNP in comparison to measurements. The cross section data table TENDL-2008-ACE is reproducing measured data best, whilst the commonly used ENDL92 and other studied libraries do not include correct tables for the gamma production from the cadmium neutron capture reaction that is occurring inside the detector. Furthermore, we have discussed the size of the annihilation peaks of spectra obtained by cadmium telluride and germanium detectors. Copyright © 2017 Elsevier Ltd. All rights reserved.
Measurement and analysis of angular neutron spectra in a manganese pile
International Nuclear Information System (INIS)
Selvi, S.; Hayashi, S.A.; Kimura, I.; Kobayashi, K.; Yamamoto, S.; Mori, T.; Nishihara, H.; Kanazawa, S.; Nakagawa, M.
1984-01-01
The energy and angular distribution of neutrons in a Mn pile were measured by the linac time-of-flight method. A cylindrical Pb target for the production of photoneutrons was placed at the center of the pile. The experimental results were compared with the theoretical calculations using the group constants from the nuclear data files, JENDL-2 and ENDF/B-IV. Good agreement can be seen in the general shapes between calculated and measured angular spectra in three decades of energy range form a few keV to a few MeV. As far as can be concluded from the intercomparison, the neutron cross section data for Mn in ENDF/B-IV may be applicable to reactor design: however, several improvements for its resonance parameters can be recommended. A little more improvements are recommended for that in JENDL-2 from this intercomparison. (orig.) [de
Using the SAND-II and MLM methods to reconstruct fast neutron spectra
International Nuclear Information System (INIS)
Bondars, Kh.Ya.; Kamnev, V.A.; Lapenas, A.A.; Troshin, V.S.
1981-01-01
The reconstruction of fast neutron spectra from measured reaction rates may be reduced to the solution of Fredholm's integral equation of the first kind. This problem falls in the category of incorrectly formulated problems, and so additional information is required concerning the unknown function i.e. concerning the differential energy dependence of the neutron, flux density sup(phi)(E). There are various methods for seeking a solution to the problem as formulated above. One of the best-known methods used in the USSR is the maximum likelihood method (MLM) (or directional difference method (DDM)), whereas SAND-II is commonly used abroad. The purpose of this paper is to compare the MLM and SAND-II methods, taking as an example the processing of measurement data which were obtained in the B-2 beam line at the BR-10 reactor in order to determine the composition of shielding for a fast reactor
International Nuclear Information System (INIS)
Mori, Takamasa
1985-05-01
In order to assess the cross section data for future reactor materials, such as molybdenum, niobium, titanium, lithium and fluorine, the angular neutron spectra in test piles of these materials or their chemical compounds have been measured in the energy range from a few keV to a few MeV by the linac time-of-flight method. The results have been compared with those theoretically calculated from the evaluated cross section data in such as JENDL-2 (or JENDL-1, JENDL-3PR1) and ENDF/B-IV. For both of molybdenum and niobium, it has been found that the energy distribution of inelastically scattered neutrons plays an important role in the analysis, and the JENDL library gives better predictions of spectrum shapes than ENDF/B-IV for both cases. In the case of niobium, however, it appears that the values of inelastic scattering cross section in JENDL-2 are too small around 2 MeV. It has been also found for niobium that the cross section data below 100 keV in ENDF/B-IV are inadequate. In a titanium pile, a discrepancy between the measured spectrum and the calculated one from ENDF/B-IV has been found in the energy range from about 60 keV to a few 100 keV. In order to investigate the cause of this discrepancy, the total cross sections for titanium have been measured by the transmission method. In the case of lithium, the discrepancy between the measured and calculated spectra is considerably reduced by adopting the angular distribution for 7 Li from ENDF/B-IV above about 500 keV. In the case of fluorine, spatial distributions of neutrons and X-rays have been also measured in both piles by the activation method to estimate the influence of photoneutrons generated in the sample material on the neutron distribution, and it has been found that their influence below 1 MeV is not so large as is necessary to be taken into account for the present assessment. (J.P.N)
International Nuclear Information System (INIS)
Rezac, K.; Klir, D.; Kubes, P.; Kravarik, J.
2009-01-01
We present the reconstruction of neutron energy spectra from time-of-flight signals. This technique is useful in experiments with the time of neutron production in the range of about tens or hundreds of nanoseconds. The neutron signals were obtained by a common hard X-ray and neutron fast plastic scintillation detectors. The reconstruction is based on the Monte Carlo method which has been improved by simultaneous usage of neutron detectors placed on two opposite sides from the neutron source. Although the reconstruction from detectors placed on two opposite sides is more difficult and a little bit inaccurate (it followed from several presumptions during the inclusion of both sides of detection), there are some advantages. The most important advantage is smaller influence of scattered neutrons on the reconstruction. Finally, we describe the estimation of the error of this reconstruction.
Arkhipkin, D. A.; Buttsev, V. S.; Chigrinov, S. E.; Kutuev, R. Kh.; Polanski, A.; Rakhno, I. L.; Sissakian, A.; Zulkarneev, R. Ya.; Zulkarneeva, Yu. R.
2003-07-01
The paper deals with theoretical and experimental investigation of transmutation rates for a number of long-lived fission products and minor actinides, as well as with neutron spectra formed in a subcritical assembly driven with the following monodirectional beams: 660-MeV protons and 14-MeV neutrons. In this work, the main objective is the comparison of neutron spectra in the MOX assembly for different external driving sources: a 660-MeV proton accelerator and a 14-MeV neutron generator. The SAD project (JINR, Russia) has being discussed. In the context of this project, a subcritical assembly consisting of a cylindrical lead target surrounded by a cylindrical MOX fuel layer will be constructed. Present conceptual design of the subcritical assembly is based on the core with a nominal unit capacity of 15 kW (thermal). This corresponds to a multiplication coefficient, keff= 0.945, and an accelerator beam power of 0.5 kW. The results of theoretical investigations on the possibility of incinerating long-lived fission products and minor actinides in fast neutron spectrum and formation of neutron spectra with different hardness in subcritical systems based on the MOX subcritical assembly are discussed. Calculated neutron spectra emitted from a lead target irradiated by a 660-MeV protons are also presented.
International Nuclear Information System (INIS)
Vasil'ev, Yu.A.; Sidorov, L.V.; Vasil'eva, N.K.; Barashkov, Yu.A.; Golovanov, O.A.; Kopalkin, N.V.; Nemudrov, N.I.; Surin, V.M.; Khachaturov, Yu.F.
1984-01-01
The results of the 4π-spectrometer mesurement of the neutron spectra in the 26-154 deg angle range for seven groups of fragments with different masses and total kinetic energies are given. Experimental spectra have been analyzed for consistency with the evaporation model of neutrons from moving fragments. The results of an analysis of differential neutron spectra shows that the main reason of the ''yearly'' neutron emission is a neutron evaporation from fragments with large excitation energy and from fragments with neutron number N>82 during the time as compared with the time of fragment acceleration
The Suppression of Energy Discretization Errors in Multigroup Transport Calculations
International Nuclear Information System (INIS)
Larsen, Edward
2013-01-01
The Objective of this project is to develop, implement, and test new deterministric methods to solve, as efficiently as possible, multigroup neutron transport problems having an extremely large number of groups. Our approach was to (i) use the standard CMFD method to 'coarsen' the space-angle grid, yielding a multigroup diffusion equation, and (ii) use a new multigrid-in-space-and-energy technique to efficiently solve the multigroup diffusion problem. The overall strategy of (i) how to coarsen the spatial an energy grids, and (ii) how to navigate through the various grids, has the goal of minimizing the overall computational effort. This approach yields not only the fine-grid solution, but also coarse-group flux-weighted cross sections that can be used for other related problems.
CASTHY, Statistical Model for Neutron Cross-Sections and Gamma-Ray Spectra
International Nuclear Information System (INIS)
Igarasi, Sin-iti; Fukahori, Tokio
1998-01-01
Description of program or function: CASTHY calculates neutron cross sections of total, shape elastic scattering and compound nucleus formation with the optical model, and compound elastic, inelastic and capture cross sections by the statistical model. The other cross sections, such as (n,2n), (n,p), (n,f) reactions are treated as cross sections of competing processes, and their sum is given through input data. Capture gamma-ray spectra can also be calculated. The branching ratio for primary transition can be treated in a particular way, if required
Theory of neutron spectra from d-d-reactions in the linear z-pinch and the plasma focus
International Nuclear Information System (INIS)
Deutsch, R.; Kaeppeler, H.J.
1982-05-01
Because of a finite gyroradius effect, the equilibrium probability density function of the ions in the azimuthal magnetic field of a linear z-pinch becomes anisotropic. This density function was derived by solving the Vlasov equation and used to determine the neutron spectra produced in the deuterium plasma of a z-pinch. The neutron spectra were calculated for two models, differing in the energy distribution of the fast ions. A background plasma with 'slow' ions was also considered. The interactions of the fast ions with the slow ions and 'beam-beam' interactions between fast ions were considered. Typical spectra for arbitrary directions to the cylindrical axis are given. The anisotropy factors were calculated. Considering the influence of the azimuthal magnetic field on the equilibrium density function of the deuterons, the well known particularities of the neutron spectra are obtained without any of the contradictions typical of the traditional models. (orig.)
International Nuclear Information System (INIS)
Sakamoto, Yukio
2001-01-01
The information about neutrons at the surrounding of JCO site in the critical accident is limited to survey results by neutron Rem counter in the period of accident and activation data very near the test facility measured after the shut down of accident. This caused the big uncertainty in the dose estimation by detailed shielding calculation codes. On the other hand, environmental activity data measured by radiochemical researchers included the information about fast neutrons inside of JCO site and thermal neutrons up to 1 km from test facility. It is important to grasp the actual circumstance and examine the executed evaluation of the critical accident as scientifically as possible. Therefore, it is meaningful for different field researchers to corporate and exchange the information. In the Technical Divisions of Radiation Science and Technology in Atomic Energy Society of Japan, the information about neutron spectra are released from their home page and three groups of JAERI/CRC, Sumitomo Atomic Energy Industry and Nuclear Power Engineering Corp. (NUPEC)/Mitsubishi Research Institute Inc. (MRI), tried the shielding calculation by Monte Carlo Code MCNP-4B. The procedures and main results of shielding calculations were reviewed in this report. The main difference of shielding calculation by three groups was density and water content of autoclaved light-weight concrete (ALC) as the wall and ceiling. From the result by NUPEC/MRI, it was estimated that the water content in ALC was from 0.05 g/cm 3 to 0.10 g/cm 3 . The behavior of dose equivalent attenuation obtained by shielding calculation was very similar with the measured data from 250 m to 1,700 m obtained by survey meter, TLD and monitoring post. For more exact dose estimation, more detail examination of density and water content of ALC will be needed. (author)
NDS multigroup cross section libraries
International Nuclear Information System (INIS)
DayDay, N.
1981-12-01
A summary description and documentation of the multigroup cross section libraries which exist at the IAEA Nuclear Data Section are given in this report. The libraries listed are available either on tape or in printed form. (author)
International Nuclear Information System (INIS)
Schwenk-Ferrero, A.
1986-11-01
GANTRAS is a system of codes for neutron transport calculations in which the anisotropy of elastic and inelastic (including (n,n'x)-reactions) scattering is fully taken into account. This is achieved by employing a rigorous method, so-called I * -method, to represent the scattering term of the transport equation and with the use of double-differential cross-sections for the description of the emission of secondary neutrons. The I * -method was incorporated into the conventional transport code ONETRAN. The ONETRAN subroutines were modified for the new purpose. An implementation of the updated version ANTRA1 was accomplished for plane and spherical geometry. ANTRA1 was included in GANTRAS and linked to another modules which prepare angle-dependent transfer matrices. The GANTRAS code consists of three modules: 1. The CROMIX code which calculates the macroscopic transfer matrices for mixtures on the base of microscopic nuclide-dependent data. 2. The ATP code which generates discretized angular transfer probabilities (i.e. discretizes the I * -function). 3. The ANTRA1 code to perform S N transport calculations in one-dimensional plane and spherical geometries. This structure of GANTRAS allows to accommodate the system to various transport problems. (orig.) [de
Effect of fission dynamics on the spectra and multiplicities of prompt fission neutrons
International Nuclear Information System (INIS)
Nix, J.R.; Madland, D.G.; Sierk, A.J.
1985-01-01
With the goal of examining their effect on the spectra and multiplicities of the prompt neutrons emitted in fission, we discuss recent advances in a unified macroscopic-microscopic description of large-amplitude collective nuclear dynamics. The conversion of collective energy into single-particle excitation energy is calculated for a new surface-plus-window dissipation mechanism. By solving the Hamilton equations of motion for initial conditions appropriate to fission, we obtain the average fission-fragment translational kinetic energy and excitation energy. The spectra and multiplicities of the emitted neutrons, which depend critically upon the average excitation energy, are then calculated on the basis of standard nuclear evaporation theory, taking into account the average motion of the fission fragments, the distribution of fission-fragment residual nuclear temperature, the energy dependence of the cross section for the inverse process of compound-nucleus formation, and the possibility of multiple-chance fission. Some illustrative comparisons of our calculations with experimental data are shown
Artificial neural network for the determination of neutron spectra in the bunker of a Linac of 18 MV
International Nuclear Information System (INIS)
Banuelos F, A.; Borja H, C. G.; Valero L, C.; Guzman G, K. A.; Hernandez D, V. M.; Vega C, H. R.
2011-11-01
The neutron spectrum and equivalent of environmental dose H(10) were calculated for a radiotherapy room in 16 punctual detectors, 15 inside of and 1 outside of the same one. The calculations were carried out with the Monte Carlo method and with the code MCNP5 for a generic room model with a Linac of 18 MV, obtaining this way 16 spectra with 47 intervals of energy class, starting from these spectra the values of H(10) were calculated. On the other hand, an artificial neural network was designed and trained to determine the spectra by neutrons in 15 different locations inside the radiotherapy room starting from the value of H(10) in the detector 16 located in the exterior of the room, using as training data the spectra and calculated dose by neutrons, of which a medium quadratic error was obtained (m se) in the adjustment between the objective data and the exit data of m se=1E(-8). The results demonstrate that the use of the artificial intelligence as technique is an useful tool in the spectrometry and dosimetry of neutrons, since it simplifies the characterization process of neutron fields in radiotherapy rooms without the use of spectrometry systems, and that once the energy distribution of the neutrons produced by the Linac is known and the corresponding doses be calculated H(10), they can take the appropriate cautions for the security patient in treatment as well as for the personnel in the room. (Author)
Burnup simulations of an inert matrix fuel using a two region, multigroup reactor physics model
Energy Technology Data Exchange (ETDEWEB)
Schneider, E. [Dept. of Mechanical Engineering, Univ. of Texas at Austin, 1 Univ. Place C2200, Austin, TX 78712 (United States); Deinert, M.; Bingham Cady, K. [Dept. of Theoretical and Applied Mechanics, Cornell Univ., Ithaca, NY 14853 (United States)
2006-07-01
Determining the time dependent concentration of isotopes in a nuclear reactor core is of fundamental importance to analysis of nuclear fuel cycles and the impact of spent fuels on long term storage facilities. We present a fast, conceptually simple tool for performing burnup calculations applicable to obtaining isotopic balances as a function of fuel burnup. The code (VBUDS: visualization, burnup, depletion and spectra) uses a two region, multigroup collision probability model to determine the energy dependent neutron flux and tracks the buildup and burnout of 24 actinides, as well as fission products. The model has been tested against benchmarked results for LWRs burning UOX and MOX, as well as MONTEBURNS simulations of zirconium oxide based IMF, all with strong fidelity. As an illustrative example, VBUDS burnup calculation results for an IMF fuel are presented in this paper. (authors)
International Nuclear Information System (INIS)
Klix, Axel; Angelone, Maurizio; Fischer, Ulrich; Pillon, Mario
2016-01-01
Highlights: • Fast neutron and gamma-ray spectra were measured in a copper assembly irradiated with DT neutrons. • The results were compared with MCNP calculations. • Primary aim was to provide experimental data for checking and validation of nuclear data evaluations of copper. - Abstract: A neutronics benchmark experiment on a pure Copper assembly was performed at the Frascati Neutron Generator. The work aimed at testing of recent nuclear data libraries. This paper focuses on the measurement of fast neutron and gamma-ray flux spectra in the Copper assembly under DT neutron irradiation in two selected positions with a spectrometer based on the organic liquid scintillator NE-213. The measurement results were compared with Monte Carlo radiation transport calculations using MCNP and nuclear data from the JEFF-3.1.1 library. Calculations have been done with Cu data from JEFF-3.1.1, JEFF-3.2, FENDL-3 and ENDF/B-7.0. Discrepancies appear in the intermediate neutron energy range between experiment and calculation. Large discrepancies were observed in the gamma-ray spectra calculated with JEFF-3.2.
Energy Technology Data Exchange (ETDEWEB)
Klix, Axel, E-mail: axel.klix@kit.edu [Karlsruhe Institute of Technology, Institute for Neutron Physics and Reactor Technology Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen (Germany); Angelone, Maurizio [ENEA Dipartimento Fusione e Tecnologie per la Sicurezza Nucleare, C.R. Frascati, via E. Fermi 45, 00044 Frascati (Italy); Fischer, Ulrich [Karlsruhe Institute of Technology, Institute for Neutron Physics and Reactor Technology Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen (Germany); Pillon, Mario [ENEA Dipartimento Fusione e Tecnologie per la Sicurezza Nucleare, C.R. Frascati, via E. Fermi 45, 00044 Frascati (Italy)
2016-11-01
Highlights: • Fast neutron and gamma-ray spectra were measured in a copper assembly irradiated with DT neutrons. • The results were compared with MCNP calculations. • Primary aim was to provide experimental data for checking and validation of nuclear data evaluations of copper. - Abstract: A neutronics benchmark experiment on a pure Copper assembly was performed at the Frascati Neutron Generator. The work aimed at testing of recent nuclear data libraries. This paper focuses on the measurement of fast neutron and gamma-ray flux spectra in the Copper assembly under DT neutron irradiation in two selected positions with a spectrometer based on the organic liquid scintillator NE-213. The measurement results were compared with Monte Carlo radiation transport calculations using MCNP and nuclear data from the JEFF-3.1.1 library. Calculations have been done with Cu data from JEFF-3.1.1, JEFF-3.2, FENDL-3 and ENDF/B-7.0. Discrepancies appear in the intermediate neutron energy range between experiment and calculation. Large discrepancies were observed in the gamma-ray spectra calculated with JEFF-3.2.
ZZ DOSCROS, Neutron Cross-Section Library for Spectra Unfolding and Integral Parameter Evaluation
International Nuclear Information System (INIS)
Zijp, Willem L.; Nolthenius, Henk J.; Rieffe, Henk Ch.
1987-01-01
1 - Description of problem or function: Format: SAND-II; Number of groups: 640 fine group cross section values; Nuclides: Li, B, F, Na, Mg, Al, S, Sc, Ti, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Br, Nb, Mo, Rh, Pd, Ag, In, Sb, I, Cs, La, Eu, Sm, Dy, Lu, Ta, W, Re, Au, Th, U, Np, Pu. Origin: ENDF/B-V mainly, ENDF/B-IV, INDL/V. This library forms in combination with the DAMSIG81 library a convenient source of evaluated energy dependent cross section sets which may be used in the determination of neutron spectra by means of adjustment (or unfolding) procedures or which can be used for the determination of integral parameters (such as damage-to-activation ratio) useful in characterising the neutron spectra. The energy dependent fine group cross section data are presented in a 640 group structure of the SAND-II type. This group structure has 45 energy groups per energy decade below 1 MeV and a group width of 100 KeV above 1 MeV. The total energy span of this group structure is from 10 -10 MeV to 20 MeV. The library has the SAND-II format, which implies that a special part of the library has to contain cover cross section data sets. These cross section data sets are required in the SAND-II program for taking into account the influence of special detector surroundings which may be used during an irradiation. 2 - Method of solution: The selection of the reactions from the evaluated nuclear data libraries was determined by various properties of the reactions for neutron metrology. For this reason all the well- known reactions of the ENDF/B-V dosimetry file are included but these data are supplemented with cross section sets for less well known metrology reactions which may become of interest
Energy Technology Data Exchange (ETDEWEB)
Petersen, Claudio Z. [Universidade Federal de Pelotas, Capao do Leao (Brazil). Programa de Pos Graduacao em Modelagem Matematica; Bodmann, Bardo E.J.; Vilhena, Marco T. [Universidade Federal do Rio Grande do Sul, Porto Alegre, RS (Brazil). Programa de Pos-graduacao em Engenharia Mecanica; Barros, Ricardo C. [Universidade do Estado do Rio de Janeiro, Nova Friburgo, RJ (Brazil). Inst. Politecnico
2014-12-15
In the present work we solve in analytical representation the three dimensional neutron kinetic diffusion problem in rectangular Cartesian geometry for homogeneous and bounded domains for any number of energy groups and precursor concentrations. The solution in analytical representation is constructed using a hierarchical procedure, i.e. the original problem is reduced to a problem previously solved by the authors making use of a combination of the spectral method and a recursive decomposition approach. Time dependent absorption cross sections of the thermal energy group are considered with step, ramp and Chebyshev polynomial variations. For these three cases, we present numerical results and discuss convergence properties and compare our results to those available in the literature.
Comparison of experimental and calculated neutron emission spectra and angular distributions
International Nuclear Information System (INIS)
Gruppelaar, H.; Akkermans, J.M.
1980-06-01
Experimental and calculated neutron emission spectra and angular distributions have been intercompared for 14.6-MeV neutron-induced reactions. The experimental data, measured by Hermsdorf et al., cover 34 elements in a large mass range. To calculate the differential neutron scattering cross sections a unified model of preequilibrium neutron emission was used, in which the generalized master equation of Mantzouranis et al. was solved with a fast exact matrix method, recently introduced by Akkermans. For the scattering kernel a three-term Legendre polynomial representation was adopted, which was either derived from the differential free nucleon-nucleon scattering cross section or fitted to obtain optimal agreement with the set of experimental data of Hermsdorf et al. The results of the last-mentioned calculation are quite acceptable in view of the fact that only two global parameters have been to describe the angular distributions of all experimental data. The report contains tables and graphs of the calculated Legendre coefficients and graphs of energy-averaged angular distributions for all 34 elements. It is further shown that improvements in the energy and angular distributions could be obtained by means of adjustment of the level-density parameters of the individual residual nuclei. Finally a short discussion is devoted to the problems of fitting angular distributions at backward angles by varying the model parameters or the specification of the initial condition. It is indicated that the so-called preequilibrium phase of the nuclear reaction actually consists of two different stages, the first one generating the forward-peaked angular distributions and the second one showing angular distributions symmetric about 90 0
International Nuclear Information System (INIS)
Allab, M.
1984-03-01
Encouraging findings in radiobiology have stimulated a renewed use of fast neutrons in radiotherapy. The physical characteristics required for neutron beams to be suitable for radiotherapy are well established. As a result, the tendency is to replace the previous machines which generated the neutron beams from deuteron bombardment of thick targets (T, Li, Be) by hospital based cyclotrons which accelerate protons on thick Beryllium targets. This report surveys the available experimental data of the 9 Be(p,n) reaction (cross sections, neutron spectra, yields, mean neutron energies) from the threshold to the proton energy Esub(p)=120 MeV and the works using this reaction in dosimetry measurements, with an emphasis on the data since 1977
International Nuclear Information System (INIS)
Petriw, S; Cantargi, F; Granada, R
2006-01-01
We present here a Synthetic Model for Molecular Solids, aimed at the description of the interaction of thermal neutrons with this kind of systems.Simple representations of the molecular dynamical modes are used, in order to produce a fair description of neutron scattering kernels and cross sections with a minimum set of input data. Using those spectra, we have generated thermal libraries for M C N P [es
Energy Technology Data Exchange (ETDEWEB)
Wright, R.Q.; Renier, J.P.; Bucholz, J.A.
1995-08-01
The original ANSL-V cross-section libraries (ORNL-6618) were developed over a period of several years for the physics analysis of the ANS reactor, with little thought toward including the materials commonly needed for shielding applications. Materials commonly used for shielding applications include calcium barium, sulfur, phosphorous, and bismuth. These materials, as well as {sup 6}Li, {sup 7}Li, and the naturally occurring isotopes of hafnium, have been added to the ANSL-V libraries. The gamma-ray production and gamma-ray interaction cross sections were completely regenerated for the ANSL-V 99n/44g library which did not exist previously. The MALOCS module was used to collapse the 99n/44g coupled library to the 39n/44g broad- group library. COMET was used to renormalize the two-dimensional (2- D) neutron matrix sums to agree with the one-dimensional (1-D) averaged values. The FRESH module was used to adjust the thermal scattering matrices on the 99n/44g and 39n/44g ANSL-V libraries. PERFUME was used to correct the original XLACS Legendre polynomial fits to produce acceptable distributions. The final ANSL-V 99n/44g and 39n/44g cross-section libraries were both checked by running RADE. The AIM module was used to convert the master cross-section libraries from binary coded decimal to binary format (or vice versa).
Measurement of keV-neutron capture cross sections and capture gamma-ray spectra of Er isotopes
International Nuclear Information System (INIS)
Harun-Ar-Rashid, A.K.M.; Igashira, Masayuki; Ohsaki, Toshiro
2000-01-01
Neutron capture cross sections and capture γ-ray spectra of 166,167, 168 Er were measured in the energy region of 10 to 550 keV. The measurements were performed with a pulsed 7 Li(p,n) 7 Be neutron source and a large anti-Compton NaI(Tl) γ-ray spectrometer. A pulse-height weighting technique and the standard capture cross sections of gold were used to derive the capture cross sections. The errors of the derived cross sections were about 5%. The present results were compared with other measurements and evaluations. The observed capture γ-ray pulse-height spectra were unfolded to obtain the corresponding γ-ray spectra. An anomalous shoulder was observed around 3 MeV in each of the capture γ-ray spectra. (author)
Energy Technology Data Exchange (ETDEWEB)
Hosseini, Seyed Abolfazl, E-mail: sahosseini@sharif.edu [Department of Energy Engineering, Sharif University of Technology, Tehran 8639-11365 (Iran, Islamic Republic of); Afrakoti, Iman Esmaili Paeen [Faculty of Engineering & Technology, University of Mazandaran, Pasdaran Street, P.O. Box: 416, Babolsar 47415 (Iran, Islamic Republic of)
2017-04-11
Accurate unfolding of the energy spectrum of a neutron source gives important information about unknown neutron sources. The obtained information is useful in many areas like nuclear safeguards, nuclear nonproliferation, and homeland security. In the present study, the energy spectrum of a poly-energetic fast neutron source is reconstructed using the developed computational codes based on the Group Method of Data Handling (GMDH) and Decision Tree (DT) algorithms. The neutron pulse height distribution (neutron response function) in the considered NE-213 liquid organic scintillator has been simulated using the developed MCNPX-ESUT computational code (MCNPX-Energy engineering of Sharif University of Technology). The developed computational codes based on the GMDH and DT algorithms use some data for training, testing and validation steps. In order to prepare the required data, 4000 randomly generated energy spectra distributed over 52 bins are used. The randomly generated energy spectra and the simulated neutron pulse height distributions by MCNPX-ESUT for each energy spectrum are used as the output and input data. Since there is no need to solve the inverse problem with an ill-conditioned response matrix, the unfolded energy spectrum has the highest accuracy. The {sup 241}Am-{sup 9}Be and {sup 252}Cf neutron sources are used in the validation step of the calculation. The unfolded energy spectra for the used fast neutron sources have an excellent agreement with the reference ones. Also, the accuracy of the unfolded energy spectra obtained using the GMDH is slightly better than those obtained from the DT. The results obtained in the present study have good accuracy in comparison with the previously published paper based on the logsig and tansig transfer functions. - Highlights: • The neutron pulse height distribution was simulated using MCNPX-ESUT. • The energy spectrum of the neutron source was unfolded using GMDH. • The energy spectrum of the neutron source was
Neutron spectra calculation in material in order to compute irradiation damage
International Nuclear Information System (INIS)
Dupont, C.; Gonnord, J.; Le Dieu de Ville, A.; Nimal, J.C.; Totth, B.
1982-01-01
This short presentation will be on neutron spectra calculation methods in order to compute the damage rate formation in irradiated structure. Three computation schemes are used in the French C.E.A.: (1) 3-dimensional calculations using the line of sight attenuation method (MERCURE IV code), the removal cross section being obtained from an adjustment on a 1-dimensional transport calculation with the discrete ordinate code ANISN; (2) 2-dimensional calculations using the discrete ordinates method (DOT 3.5 code), 20 to 30 group library obtained by collapsing the 100 group a library on fluxes computed by ANISN; (3) 3-dimensional calculations using the Monte Carlo method (TRIPOLI system). The cross sections which originally came from UKNDL 73 and ENDF/B3 are now processed from ENDF B IV. (author)
NEWSPEC: A computer code to unfold neutron spectra from Bonner sphere data
International Nuclear Information System (INIS)
Lemley, E.C.; West, L.
1996-01-01
A new computer code, NEWSPEC, is in development at the University of Arkansas. The NEWSPEC code allows a user to unfold, fold, rebin, display, and manipulate neutron spectra as applied to Bonner sphere measurements. The SPUNIT unfolding algorithm, a new rebinning algorithm, and the graphical capabilities of Microsoft (MS) Windows and MS Excel are utilized to perform these operations. The computer platform for NEWSPEC is a personal computer (PC) running MS Windows 3.x or Win95, while the code is written in MS Visual Basic (VB) and MS VB for Applications (VBA) under Excel. One of the most useful attributes of the NEWSPEC software is the link to Excel allowing additional manipulation of program output or creation of program input
Energy Technology Data Exchange (ETDEWEB)
Ghrayeb, S. Z. [Dept. of Mechanical and Nuclear Engineering, Pennsylvania State Univ., 230 Reber Building, Univ. Park, PA 16802 (United States); Ouisloumen, M. [Westinghouse Electric Company, 1000 Westinghouse Drive, Cranberry Township, PA 16066 (United States); Ougouag, A. M. [Idaho National Laboratory, MS-3860, PO Box 1625, Idaho Falls, ID 83415 (United States); Ivanov, K. N.
2012-07-01
A multi-group formulation for the exact neutron elastic scattering kernel is developed. This formulation is intended for implementation into a lattice physics code. The correct accounting for the crystal lattice effects influences the estimated values for the probability of neutron absorption and scattering, which in turn affect the estimation of core reactivity and burnup characteristics. A computer program has been written to test the formulation for various nuclides. Results of the multi-group code have been verified against the correct analytic scattering kernel. In both cases neutrons were started at various energies and temperatures and the corresponding scattering kernels were tallied. (authors)
Bedogni, Roberto; Pelliccioni, Maurizio; Esposito, Adolfo
2010-03-01
Due to the increased interest of the scientific community in the applications of synchrotron light, there is an increasing demand of high-energy electron facilities, testified by the construction of several new facilities worldwide. The radiation protection around such facilities requires accurate experimental methods to determine the dose due to prompt radiation fields. Neutron fields, in particular, are the most complex to measure, because they extend in energy from thermal (10 -8 MeV) up to hundreds MeV and because the responses of dosemeters and survey meters usually have large energy dependence. The Bonner Spheres Spectrometer (BSS) is in practice the only instrument able to respond over the whole energy range of interest, and for this reason it is frequently used to derive neutron spectra and dosimetric quantities in accelerator workplaces. Nevertheless, complex unfolding algorithms are needed to derive the neutron spectra from the experimental BSS data. This paper presents a parametric model specially developed for the unfolding of the experimental data measured with BSS around high-energy electron accelerators. The work consists of the following stages: (1) Generation with the FLUKA code, of a set of neutron spectra representing the radiation environment around accelerators with different electron energies; (2) formulation of a parametric model able to describe these spectra, with particular attention to the high-energy component (>10 MeV), which may be responsible for a large part of the dose in workplaces; and (3) implementation of this model in an existing unfolding code.
International Nuclear Information System (INIS)
Bedogni, Roberto; Pelliccioni, Maurizio; Esposito, Adolfo
2010-01-01
Due to the increased interest of the scientific community in the applications of synchrotron light, there is an increasing demand of high-energy electron facilities, testified by the construction of several new facilities worldwide. The radiation protection around such facilities requires accurate experimental methods to determine the dose due to prompt radiation fields. Neutron fields, in particular, are the most complex to measure, because they extend in energy from thermal (10 -8 MeV) up to hundreds MeV and because the responses of dosemeters and survey meters usually have large energy dependence. The Bonner Spheres Spectrometer (BSS) is in practice the only instrument able to respond over the whole energy range of interest, and for this reason it is frequently used to derive neutron spectra and dosimetric quantities in accelerator workplaces. Nevertheless, complex unfolding algorithms are needed to derive the neutron spectra from the experimental BSS data. This paper presents a parametric model specially developed for the unfolding of the experimental data measured with BSS around high-energy electron accelerators. The work consists of the following stages: (1) Generation with the FLUKA code, of a set of neutron spectra representing the radiation environment around accelerators with different electron energies; (2) formulation of a parametric model able to describe these spectra, with particular attention to the high-energy component (>10 MeV), which may be responsible for a large part of the dose in workplaces; and (3) implementation of this model in an existing unfolding code.
International Nuclear Information System (INIS)
Perry, R.T.; Wilson, W.B.; Charlton, W.S.
1998-04-01
In many systems, it is imperative to have accurate knowledge of all significant sources of neutrons due to the decay of radionuclides. These sources can include neutrons resulting from the spontaneous fission of actinides, the interaction of actinide decay α-particles in (α,n) reactions with low- or medium-Z nuclides, and/or delayed neutrons from the fission products of actinides. Numerous systems exist in which these neutron sources could be important. These include, but are not limited to, clean and spent nuclear fuel (UO 2 , ThO 2 , MOX, etc.), enrichment plant operations (UF 6 , PuF 4 , etc.), waste tank studies, waste products in borosilicate glass or glass-ceramic mixtures, and weapons-grade plutonium in storage containers. SOURCES-3A is a computer code that determines neutron production rates and spectra from (α,n) reactions, spontaneous fission, and delayed neutron emission due to the decay of radionuclides in homogeneous media (i.e., a mixture of α-emitting source material and low-Z target material) and in interface problems (i.e., a slab of α-emitting source material in contact with a slab of low-Z target material). The code is also capable of calculating the neutron production rates due to (α,n) reactions induced by a monoenergetic beam of α-particles incident on a slab of target material. Spontaneous fission spectra are calculated with evaluated half-life, spontaneous fission branching, and Watt spectrum parameters for 43 actinides. The (α,n) spectra are calculated using an assumed isotropic angular distribution in the center-of-mass system with a library of 89 nuclide decay α-particle spectra, 24 sets of measured and/or evaluated (α,n) cross sections and product nuclide level branching fractions, and functional α-particle stopping cross sections for Z < 106. The delayed neutron spectra are taken from an evaluated library of 105 precursors. The code outputs the magnitude and spectra of the resultant neutron source. It also provides an
Neutron and gamma-ray spectra measurement on the model of the KS-150 reactor radial shielding
International Nuclear Information System (INIS)
Holman, M.; Hogel, J.; Marik, J.; Kovarik, K.; Franc, L.; Vespalec, R.
1977-01-01
A shortened model of the peripheral region of the KS-150 reactor core consisting of two rows of fuel elements and a reflector was constructed from the peripheral fuel elements of the KS-150 reactor core in an experiment on the TR-0 reactor. The mockup of the thermal shield (10 cm of steel), the pressure vessel (15 cm of steel) and the inner wall of the water biological shielding (2 cm of steel) of the KS-150 reactor were erected outside the TR-0 vessel. Fast neutron and gamma spectra were measured with a stilbene crystal scintillation spectrometer. The resonance neutron spectra were measured with 197 Au, 63 Cu and 23 Na resonance activation detectors. Fast neutron spectra inside the reactor were measured with a 10 mm diameter by 10 mm thick stilbene crystal spectrometer, outside the reactor with a 10 mm diameter by 10 mm thick and a 20 mm diameter by 20 mm thick stilbene crystal spectrometer. Neutron spectra in the energy regions of 1 eV to 3 keV and 0.6 MeV to 0.8 MeV were obtained on the core periphery, on the reflector half-thickness and in front of and behind the reactor thermal shield. Gamma spectra were obtained in front of and behind the thermal shield. It was found that the attenuation of neutron fluxes by the reflector and the thermal shield increased with increasing energy while gamma radiation attenuation decreased with increasing energy. It was not possible to obtain the neutron spectrum in the 10 to 600 keV energy range because suitable detection instrumentation was not available. (J.P.)
Calculated microdose spectra for intermediate energy neutrons (1 to 100 keV)
International Nuclear Information System (INIS)
Al-Affan, I.A.M.; Watt, D.E.
1983-01-01
Basic formulae for calculation of energy deposition events due to insiders, starters, stoppers and crossers, using the continuous slowing down approximation have been modified to allow for the enhanced energy deposition in spherical volumes due to elastic scattering interactions which reduce the penetration depth of the charged particle recoils. Energy deposition spectra have been obtained for energies of 1, 10, 50, 100 keV in 0.2 μm and 1 μm tissue-equivalent spheres. From these, frequency and dose distributions in lineal energy and in specific energy density have been calculated. Also calculated for different neutron energies are values of zeta, the energy average of event size, as a function of the diameter of the sensitive site. The structure of the energy event distributions can be interpreted in terms of the basic physics. The effect of the modifications to the basic formulae is to increase the number of energy deposition events due to insiders and to decrease the number of starters, stoppers and crossers. The degree of the effect increases with decreasing neutron energy, increasing sphere size, and the change is most significant for low energy deposition events. (author)
Calculated microdose spectra for intermediate energy neutrons (1 to 100 keV)
Energy Technology Data Exchange (ETDEWEB)
Al-Affan, I.A.M.; Watt, D.E. (Dundee Univ. (UK). Dept. of Medical Biophysics); Colautti, P.; Talpo, G. (Laboratori Nazionali dell' Infn, 35020, Legnaro (Padova) (Italy))
1983-01-01
Basic formulae for calculation of energy deposition events due to insiders, starters, stoppers and crossers, using the continuous slowing down approximation have been modified to allow for the enhanced energy deposition in spherical volumes due to elastic scattering interactions which reduce the penetration depth of the charged particle recoils. Energy deposition spectra have been obtained for energies of 1, 10, 50, 100 keV in 0.2 ..mu..m and 1 ..mu..m tissue-equivalent spheres. From these, frequency and dose distributions in lineal energy and in specific energy density have been calculated. Also calculated for different neutron energies are values of zeta, the energy average of event size, as a function of the diameter of the sensitive site. The structure of the energy event distributions can be interpreted in terms of the basic physics. The effect of the modifications to the basic formulae is to increase the number of energy deposition events due to insiders and to decrease the number of starters, stoppers and crossers. The degree of the effect increases with decreasing neutron energy, increasing sphere size, and the change is most significant for low energy deposition events.
Measurement of prompt fission gamma-ray spectra in fast neutron-induced fission
International Nuclear Information System (INIS)
Laborie, J.M.; Belier, G.; Taieb, J.
2012-01-01
Knowledge of prompt fission gamma-ray emission has been of major interest in reactor physics for a few years. Since very few experimental spectra were ever published until now, new measurements would be also valuable to improve our understanding of the fission process. An experimental method is currently being developed to measure the prompt fission gamma-ray spectrum from some tens keV up to 10 MeV at least. The mean multiplicity and total energy could be deduced. In this method, the gamma-rays are measured with a bismuth germanate (BGO) detector which has the advantage to present a high P/T ratio and a high efficiency compared to other gamma-ray detectors. The prompt fission neutrons are rejected by the time of flight technique between the BGO detector and a fission trigger given by a fission chamber or a scintillating active target. Energy and efficiency calibration of the BGO detector were carried out up to 10.76 MeV by means of the Al-27(p, gamma) reaction. First prompt fission gamma-ray spectrum measurements performed for the spontaneous fission of Cf-252 and for 1.7 and 15.6 MeV neutron-induced fission of U-238 at the CEA, DAM, DIF Van de Graaff accelerator, will be presented. (authors)
International Nuclear Information System (INIS)
Baba, Mamoru; Itoh, Nobuo; Maeda, Kazuto; Hirakawa, Naohiro; Wakabayashi, Hidetaka.
1989-10-01
This report presents the summary of experimental studies of prompt fission neutron spectra and double-differential neutron inelastic-scattering cross sections of 238 U and 232 Th. The experiments were performed at Tohoku University Fast Neutron Laboratory employing a time-of-flight technique and Dynamitron accelerator as the pulsed neutron generator. From the experiments, we obtained the following data for both nuclei; 1. prompt fission neutron spectrum for 2 MeV neutrons, 2. double-differential neutron inelastic-scattering cross sections for 1.2, 2.0, 4.2, 6.1 and 14.1 MeV incident neutrons. Both in experiments and data processing, cares were taken to obtain reliable data by avoiding systematic uncertainty. The experimental data were compared with those by other experiments, evaluations and model calculations. Through the data comparison, some fundamental problems were found in the experiments by previous authors and the evaluations. The present data will provide useful data base for refinement of the evaluated data and theoretical models. (author)
Optimal calculational schemes for solving multigroup photon transport problem
International Nuclear Information System (INIS)
Dubinin, A.A.; Kurachenko, Yu.A.
1987-01-01
A scheme of complex algorithm for solving multigroup equation of radiation transport is suggested. The algorithm is based on using the method of successive collisions, the method of forward scattering and the spherical harmonics method, and is realized in the FORAP program (FORTRAN, BESM-6 computer). As an example the results of calculating reactor photon transport in water are presented. The considered algorithm being modified may be used for solving neutron transport problems
Nuclear data and multigroup methods in fast reactor calculations
International Nuclear Information System (INIS)
Gur, Y.
1975-03-01
The work deals with fast reactor multigroup calculations, and the efficient treatment of basic nuclear data, which serves as raw material for the calculations. Its purpose is twofold: to build a computer code system that handles a large, detailed library of basic neutron cross section data, (such as ENDF/B-III) and yields a compact set of multigroup cross sections for reactor calculations; to use the code system for comparative analysis of different libraries, in order to discover basic uncertainties that still exist in the measurement of neutron cross sections, and to determine their influence upon uncertainties in nuclear calculations. A program named NANICK which was written in two versions is presented. The first handles the American basic data library, ENDF/B-III, while the second handles the German basic data library, KEDAK. The mathematical algorithm is identical in both versions, and only the file management is different. This program calculates infinitely diluted multigroup cross sections and scattering matrices. It is complemented by the program NASIF that calculates shielding factors from resonance parameters. Different versions of NASIF were written to handle ENDF/B-III or KEDAK. New methods for evaluating in reactor calculations the long term behavior of the neutron flux as well as its fine structure are described and an efficient calculation of the shielding factors from resonance parameters is offered. (B.G.)
Comparison of (alpha, n) thick-target neutron yields and spectra from ORIGEN-S and SOURCES
International Nuclear Information System (INIS)
Brown, T.H.; Wilson, W.B.; Perry, R.T.; Charlton, W.S.
1998-01-01
Both ORIGEN-S and SOURCES generate thick-target neutron yields and energy spectra from (α,n) reactions in homogeneous materials. SOURCES calculates yield and spectra for any material containing α-emitting and (α,n) target elements by simulating reaction physics, using α-emission energy spectra, elemental stopping cross sections, (α,n) cross sections for target nuclei, and branching fractions to produce-nuclide energy levels. This methodology results in accurate yield and spectra. ORIGEN-S has two options for calculating yields and spectra. The UO 2 option (default) estimates yields and spectra assuming the input α-emitters to be infinitely dilute in UO 2 . The borosilicate-glass option estimates yields from the total input material composition and generates spectra purportedly representative of spectra generated by 238 Pu, 241 Am, 242 Cm, and 244 Cm infinitely dilute in borosilicate glass, even if none of these four α-emitters are present in the input material composition. Because yields from the borosilicate-glass option in ORIGEN-S are based on entire input material composition and are reasonably accurate, the same is often assumed to be true for spectra. The input/output functionality of the borosilicate-glass option, along with ambiguity in ORIGEN-S documentation, gives the incorrect impression that spectra representative of input compositions are generated. This impression is reinforced by wide usage of the SCALE code system and its ORIGEN-S module and their sponsorship by the US Nuclear Regulatory Commission
Energy Technology Data Exchange (ETDEWEB)
Milosevic, M [Institute of Nuclear Sciences Vinca, Beograd (Serbia and Montenegro)
1979-07-01
One-dimensional variational method for cylindrical configuration was applied for calculating group constants, together with effects of elastic slowing down, anisotropic elastic scattering, inelastic scattering, heterogeneous resonance absorption with the aim to include the presence of a number of different isotopes and effects of neutron leakage from the reactor core. Neutron flux shape P{sub 3} and adjoint function are proposed in order to enable calculation of smaller size reactors and inclusion of heterogeneity effects by cell calculations. Microscopic multigroup constants were prepared based on the UKNDL data library. Analytical-numerical approach was applied for solving the equations of the P{sub 3} approximation to obtain neutron flux moments and adjoint functions.
International Nuclear Information System (INIS)
Seidel, K.; Freiesleben, H.; Poenitz, E.; Klix, A.; Unholzer, S.; Batistoni, P.; Fischer, U.; Leichtle, D.
2006-01-01
The nuclear parameters of a breeding blanket, such as tritium production rate, nuclear heating, activation and dose rate, are calculated by integral folding of an energy dependent cross section (or coefficient) with the neutron (or gamma-ray) flux energy spectra. The uncertainties of the designed parameters are determined by the uncertainties of both the cross section data and the flux spectra obtained by transport calculations. Also the analysis of possible discrepancies between measured and calculated integral nuclear parameter represents a two-step procedure. First, the energy region and the amount of flux discrepancies has to be found out and second, the cross section data have to be checked. To this end, neutron and gamma-ray flux spectra in a mock-up of the EU Helium-Cooled Pebble Bed (HCPB) breeder Test Blanket Module (TBM), irradiated with 14 MeV neutrons, were measured and analysed by means of Monte Carlo transport calculations. The flux spectra were determined for the energy ranges that are relevant for the most important nuclear parameters of the TBM, which are the tritium production rate and the shielding capability. The fast neutron flux which determines the tritium production on 7 Li and dominates the shield design was measured by the pulse-height distribution obtained from an organic liquid scintillation detector. Simultaneously, the gamma-ray flux spectra were measured. The neutron flux at lower energies, down to thermal, which determines the tritium production on 6 Li, was measured with time-of-arrival spectroscopy. For this purpose, the TUD neutron generator was operated in pulsed mode (pulse width 10 μs, frequency 1 kHz) and the neutrons arriving at a 3 He proportional counter in the mock-up were recorded as a function of time after the source neutron pulse. The spectral distributions for the two positions in the mock-up, where measurements were carried out, were calculated with the Monte Carlo code MCNP, version 5, and nuclear data from the
Inter-pulse high-resolution gamma-ray spectra using a 14 MeV pulsed neutron generator
Evans, L.G.; Trombka, J.I.; Jensen, D.H.; Stephenson, W.A.; Hoover, R.A.; Mikesell, J.L.; Tanner, A.B.; Senftle, F.E.
1984-01-01
A neutron generator pulsed at 100 s-1 was suspended in an artificial borehole containing a 7.7 metric ton mixture of sand, aragonite, magnetite, sulfur, and salt. Two Ge(HP) gamma-ray detectors were used: one in a borehole sonde, and one at the outside wall of the sample tank opposite the neutron generator target. Gamma-ray spectra were collected by the outside detector during each of 10 discrete time windows during the 10 ms period following the onset of gamma-ray build-up after each neutron burst. The sample was measured first when dry and then when saturated with water. In the dry sample, gamma rays due to inelastic neutron scattering, neutron capture, and decay were counted during the first (150 ??s) time window. Subsequently only capture and decay gamma rays were observed. In the wet sample, only neutron capture and decay gamma rays were observed. Neutron capture gamma rays dominated the spectrum during the period from 150 to 400 ??s after the neutron burst in both samples, but decreased with time much more rapidly in the wet sample. A signal-to-noise-ratio (S/N) analysis indicates that optimum conditions for neutron capture analysis occurred in the 350-800 ??s window. A poor S/N in the first 100-150 ??s is due to a large background continuum during the first time interval. Time gating can be used to enhance gamma-ray spectra, depending on the nuclides in the target material and the reactions needed to produce them, and should improve the sensitivity of in situ well logging. ?? 1984.
Analysis of a neutron scattering integral experiment on iron for neutron energies from 1 to 15 MeV
International Nuclear Information System (INIS)
Cramer, S.N.; Oblow, E.M.
1976-11-01
Monte Carlo calculations were made to analyze the results of an integral experiment with an iron sample to determine the adequacy of neutron scattering cross section data for iron. The experimental results analyzed included energy-dependent NE-213 detector count rates at a scattering angle of 90 deg and pulse-height spectra for scattered neutrons produced in an iron ring pulsed with a 1- to 20-MeV neutron source. The pulse-height data were unfolded to generate secondary neutron spectra at 90 deg as a function of incident neutron energy. Multigroup Monte Carlo calculations using the MORSE code and ENDF/B-IV cross sections were made to analyze all reported results. Discrepancies between calculated and measured responses were found for inelastic scattering reactions in the range from 1 to 4 MeV. These results were related to deficiencies in ENDF/B-IV iron cross section data
Martín-Hernández, G; Mastinu, P F; Praena, J; Dzysiuk, N; Capote Noy, R; Pignatari, M
2012-08-01
The need of neutron capture cross section measurements for astrophysics motivates present work, where calculations to generate stellar neutron spectra at different temperatures are performed. The accelerator-based (7)Li(p,n)(7)Be reaction is used. Shaping the proton beam energy and the sample covering a specific solid angle, neutron activation for measuring stellar-averaged capture cross section can be done. High-quality Maxwell-Boltzmann neutron spectra are predicted. Assuming a general behavior of the neutron capture cross section a weighted fit of the spectrum to Maxwell-Boltzmann distributions is successfully introduced. Copyright © 2012 Elsevier Ltd. All rights reserved.
Measurement of cold neutron spectra at a model of cryogenic moderator of the IBR-2M reactor
International Nuclear Information System (INIS)
Kulikov, S.A.; Chernikov, A.N.; Shabalin, E.P.; Kalinin, I.V.; Morozov, V.M.; Novikov, A.G.; Puchkov, A.V.
2010-01-01
The article is dedicated to methods and results of experimental determination of cold neutron spectra from solid mesitylene at neutron moderator temperatures 10-50 K. Experiments were fulfilled at the DIN-2PI spectrometer of the IBR-2 reactor. The main goals of this work were to examine a system of constants for Monte Carlo calculation of cryogenic moderators of the IBR-2M reactor and to determine the temperature dependence of cold neutron intensity from the moderator. A reasonable agreement of experimental and calculation results for mesitylene at 20 K has been obtained. The cold neutron intensity at temperature of moderator 10 K is about 1.8 times higher than at T=50 K
International Nuclear Information System (INIS)
Demidov, A.M.; Dikarev, V.S.; Efimov, B.V.; Ionov, V.S.; Marin, S.V.
2005-01-01
The method proposed for estimation of parameters thermal and epithermal parts of energy distribution of neutrons is described. The method based on application of activation measuring with use of unified composition detectors (UCD) and samples of fuel. The method is applicable for definition of neutron spectrum parameters and velocities of division in fuel of nuclear installations. Theoretical bases and the description of a method, expedients of manufacturing and calibration for the detectors, the experimental data, carried out in RRC KI are given and processing of experimental data, and also. The parametric model of a spectrum constructed on the basis of Westcott's formalism is described. The parameter of stiffness is entered and its role for temperature of neutron gas, spectral coefficients of isotopes of detectors, the transition area thermal and epithermal parts of neutron spectra is observationally appreciated. It is offered to confirm the found results by calculations with use of MCU Monte Carlo code [ru
International Nuclear Information System (INIS)
Ganapol, B.D.
2011-01-01
Highlights: → Coupled neutron and gamma transport is considered in the multigroup diffusion approximation. → The model accommodates fission, up- and down-scattering and common neutron-gamma interactions. → The exact solution to the diffusion equation in a heterogeneous media of any number of regions is found. → The solution is shown to parallel the one-group case in a homogeneous medium. → The discussion concludes with a heterogeneous, 2 fuel-plate 93.2% enriched reactor fuel benchmark demonstration. - Abstract: The angular flux for the 'rod model' describing coupled neutron/gamma (n, γ) diffusion has a particularly straightforward analytical representation when viewed from the perspective of a one-group homogeneous medium. Cast in the form of matrix functions of a diagonalizable matrix, the solution to the multigroup equations in heterogeneous media is greatly simplified. We shall show exactly how the one-group homogeneous medium solution leads to the multigroup solution.
Energy Technology Data Exchange (ETDEWEB)
Siegel, Daniel M. [Max Planck Institute for Gravitational Physics (Albert Einstein Institute), Am Mühlenberg 1, D-14476 Potsdam-Golm (Germany); Ciolfi, Riccardo, E-mail: daniel.siegel@aei.mpg.de, E-mail: riccardo.ciolfi@unitn.it [Physics Department, University of Trento, Via Sommarive 14, I-38123 Trento (Italy)
2016-03-01
Recent observations indicate that in a large fraction of binary neutron star (BNS) mergers a long-lived neutron star (NS) may be formed rather than a black hole. Unambiguous electromagnetic (EM) signatures of such a scenario would strongly impact our knowledge on how short gamma-ray bursts (SGRBs) and their afterglow radiation are generated. Furthermore, such EM signals would have profound implications for multimessenger astronomy with joint EM and gravitational-wave (GW) observations of BNS mergers, which will soon become reality thanks to the ground-based advanced LIGO/Virgo GW detector network. Here we explore such EM signatures based on the model presented in a companion paper, which provides a self-consistent evolution of the post-merger system and its EM emission up to ∼10{sup 7} s. Light curves and spectra are computed for a wide range of post-merger physical properties. We present X-ray afterglow light curves corresponding to the “standard” and the “time-reversal” scenario for SGRBs (prompt emission associated with the merger or with the collapse of the long-lived NS). The light curve morphologies include single and two-plateau features with timescales and luminosities that are in good agreement with Swift observations. Furthermore, we compute the X-ray signal that should precede the SGRB in the time-reversal scenario, the detection of which would represent smoking-gun evidence for this scenario. Finally, we find a bright, highly isotropic EM transient peaking in the X-ray band at ∼10{sup 2}–10{sup 4} s after the BNS merger with luminosities of L{sub X} ∼ 10{sup 46}–10{sup 48} erg s{sup −1}. This signal represents a very promising EM counterpart to the GW emission from BNS mergers.
International Nuclear Information System (INIS)
Donahue, R.J.; Thomas, R.H.; Zeman, G.H.
2001-01-01
Offsite neutron fluences resulting from Bevatron operations reached a maximum in 1959, prior to the addition of a permanent concrete roof shield, which was constructed in 1962. From the first operation of the Bevatron measurements of neutron fluence were made at locations around the perimeter of the Lawrence Berkeley National Laboratory (LBNL) campus. Since the late 1950's measurements made at several locations, and particularly at the site of what is now called the Olympus Gate Environmental Monitoring Station, have been routinely reported and published. Early measurements were used to establish the shape of the neutron-energy spectrum from which an energy-averaged fluence-to-dose equivalent conversion coefficient could be derived. This conversion coefficient was then applied to a measured total neutron fluence to obtain the appropriate dose equivalent quantity required by regulation. Recent work by Thomas et al. (2000) have compared the early conversion coefficients used in the sixties with those accepted today and suggest suggested that ''the dose equivalents reported in the late fifties and early sixties were conservative by factors between two and four. In any current review of the historical data, therefore it would be prudent to reduce the reported dose equivalents by at least a factor of two.'' However, that analysis was based on the ''state of the art'' neutron energy-spectra of the '60s. This paper provides a detailed knowledge of the neutron energy spectrum at the site boundary paper thus removing any uncertainty in the analysis of Thomas et al., which might be caused by the use of the early neutron energy-spectra. Detailed Monte Carlo analyses of the interactions of 6.2 GeV protons in thick, medium-A targets are described. In the computer simulations, neutrons produced were allowed to scatter in the atmosphere. Detailed neutron energy spectra were calculated at a distance and elevation corresponding to the location of the Olympus Gate EMS. Both older
Multigroup neutron data base for nuclear geophysics
International Nuclear Information System (INIS)
Dworak, D.; Loskiewicz, J.
1989-01-01
The average group constants for the total, elastic, inelastic and capture cross sections as well as the average cosine of the scattering angle for elastic scattering and the average logarithmic energy decrement for elastic scattering have been obtained at two temperatures (300 and 400 deg K), using the ENDF/B-4 data and the IAEA-NDS pre-processing codes. The extended Abagyan group structure and the weighting spectrum of type 1/E were applied in course of the calculations. Self-shielding effect was not taken into account. All cross sections were Doppler broadened for both, 300 and 400 deg K temperatures. Under above assumptions, the average group constants were obtained for exactly 22 ENDF materials, which are of special importance for nuclear geophysics applications. 10 refs., 15 figs., 44 tabs. (author)
Kalpakkam multigroup cross section set for fast reactor applications - status and performance
International Nuclear Information System (INIS)
Ramanadhan, M.M.; Gopalakrishnan, M.M.
1986-01-01
This report documents the status of the presently created set of multigroup constants at Kalpakkam. The list of nuclides processed and the details of multigroup structure are given. Also included are the particulars of dilutions and temperatures for each nuclide in the multigroup cross section set for which self shielding factors have been calculated. Using this new multigroup cross section set, measured integral quantities such as K-eff, central reaction rate ratios, central reactivity worths etc. were calculated for a few fast critical benchmark assemblies and the calculated values of neutronic parameters obtained were compared with those obtained using the available Cadarache cross section library and those published in literature for ENDF/B-IV based set and Japanese evaluated nuclear data library (JENDL). The details of analyses are documented along with the conclusions. (author). 17 refs., 12 tabs
Energy Technology Data Exchange (ETDEWEB)
Chittenden, J. P., E-mail: j.chittenden@imperial.ac.uk; Appelbe, B. D.; Manke, F.; McGlinchey, K.; Niasse, N. P. L. [Centre for Inertial Fusion Studies, The Blackett Laboratory, Imperial College, London SW7 2AZ (United Kingdom)
2016-05-15
We present the results of 3D simulations of indirect drive inertial confinement fusion capsules driven by the “high-foot” radiation pulse on the National Ignition Facility. The results are post-processed using a semi-deterministic ray tracing model to generate synthetic deuterium-tritium (DT) and deuterium-deuterium (DD) neutron spectra as well as primary and down scattered neutron images. Results with low-mode asymmetries are used to estimate the magnitude of anisotropy in the neutron spectra shift, width, and shape. Comparisons of primary and down scattered images highlight the lack of alignment between the neutron sources, scatter sites, and detector plane, which limits the ability to infer the ρr of the fuel from a down scattered ratio. Further calculations use high bandwidth multi-mode perturbations to induce multiple short scale length flows in the hotspot. The results indicate that the effect of fluid velocity is to produce a DT neutron spectrum with an apparently higher temperature than that inferred from the DD spectrum and which is also higher than the temperature implied by the DT to DD yield ratio.
Gatu Johnson, M.; Frenje, J.; Lahmann, B.; Seguin, F.; Petrasso, R.; Appelbe, B.; Chittenden, J.; Walsh, C.; Delettrez, J.; Igumenshchev, I.; Knauer, J. P.; Glebov, V. Yu.; Forrest, C.; Grimble, W.; Marshall, F.; Michel, T.; Stoeckl, C.; Haines, B. M.; Zylstra, A. B.
2017-10-01
Ion temperatures (Tion) in Inertial Confinement Fusion (ICF) experiments have traditionally been inferred from the broadening of primary neutron spectra. Directional motion (flow) of the fuel at burn, expected to arise due to asymmetries imposed by e.g. engineering features or drive non-uniformity, also impacts broadening and may lead to artificially inflated ``Tion'' values. Flow due to low-mode asymmetries is expected to give rise to line-of-sight variations in measured Tion, as observed in OMEGA cryogenic DT implosions but not in similar experiments at the NIF. In this presentation, we report on OMEGA experiments with intentional drive asymmetry designed for testing the ability to accurately predict and measure line-of-sight differences in apparent Tion due to low-mode asymmetry-seeded flows. The measurements are contrasted to CHIMERA, RAGE and ASTER simulations, providing insight into implosion dynamics and the relative importance of laser drive non-uniformity, stalk and offset as sources of asymmetry. The results highlight the complexity of hot-spot dynamics, which is a problem that must be mastered to achieve ICF ignition. This work was supported in part by the U.S. DOE, NLUF and LLE.
MPI version of NJOY and its application to multigroup cross-section generation
Energy Technology Data Exchange (ETDEWEB)
Alpan, A.; Haghighat, A.
1999-07-01
Multigroup cross-section libraries are needed in performing neutronics calculations. These libraries are referred to as broad-group libraries. The number of energy groups and group structure are highly dependent on the application and/or user's objectives. For example, for shielding calculations, broad-group libraries such as SAILOR and BUGLE with 47-neutron and 20-gamma energy groups are used. The common procedure to obtain a broad-group library is a three-step process: (1) processing pointwise ENDF (PENDF) format cross sections; (2) generating fine-group cross sections; and (3) collapsing fine-group cross sections to broad-group. The NJOY code is used to prepare fine-group cross sections by processing pointwise ENDF data. The code has several modules, each one performing a specific task. For instance, the module RECONR performs linearization and reconstruction of the cross sections, and the module GROUPR generates multigroup self-shielded cross sections. After fine-group, i.e., groupwise ENDF (GENDF), cross sections are produced, cross sections are self-shielded, and a one-dimensional transport calculation is performed to obtain flux spectra at specific regions in the model. These fluxes are then used as weighting functions to collapse the fine-group cross sections to obtain a broad-group cross-section library. The third step described is commonly performed by the AMPX code system. SMILER converts NJOY GENDF filed to AMPX master libraries, AJAX collects the master libraries. BONAMI performs self-shielding calculations, NITAWL converts the AMPX master library to a working library, XSDRNPM performs one-dimensional transport calculations, and MALOCS collapses fine-group cross sections to broad-group. Finally, ALPO is used to generate ANISN format libraries. In this three-step procedure, generally NJOY requires the largest amount of CPU time. This time varies depending on the user's specified parameters for each module, such as reconstruction tolerances
MPI version of NJOY and its application to multigroup cross-section generation
International Nuclear Information System (INIS)
Alpan, A.; Haghighat, A.
1999-01-01
Multigroup cross-section libraries are needed in performing neutronics calculations. These libraries are referred to as broad-group libraries. The number of energy groups and group structure are highly dependent on the application and/or user's objectives. For example, for shielding calculations, broad-group libraries such as SAILOR and BUGLE with 47-neutron and 20-gamma energy groups are used. The common procedure to obtain a broad-group library is a three-step process: (1) processing pointwise ENDF (PENDF) format cross sections; (2) generating fine-group cross sections; and (3) collapsing fine-group cross sections to broad-group. The NJOY code is used to prepare fine-group cross sections by processing pointwise ENDF data. The code has several modules, each one performing a specific task. For instance, the module RECONR performs linearization and reconstruction of the cross sections, and the module GROUPR generates multigroup self-shielded cross sections. After fine-group, i.e., groupwise ENDF (GENDF), cross sections are produced, cross sections are self-shielded, and a one-dimensional transport calculation is performed to obtain flux spectra at specific regions in the model. These fluxes are then used as weighting functions to collapse the fine-group cross sections to obtain a broad-group cross-section library. The third step described is commonly performed by the AMPX code system. SMILER converts NJOY GENDF filed to AMPX master libraries, AJAX collects the master libraries. BONAMI performs self-shielding calculations, NITAWL converts the AMPX master library to a working library, XSDRNPM performs one-dimensional transport calculations, and MALOCS collapses fine-group cross sections to broad-group. Finally, ALPO is used to generate ANISN format libraries. In this three-step procedure, generally NJOY requires the largest amount of CPU time. This time varies depending on the user's specified parameters for each module, such as reconstruction tolerances, temperatures
Thermal neutron group constants in monoatomic-gas approximation
Energy Technology Data Exchange (ETDEWEB)
Matausek, M V; Bosevski, T [Institute of nuclear sciences Boris Kidric, Vinca, Beograd (Yugoslavia)
1965-12-15
To solve the problem of space-energy neutron distribution in an elementary reactor cell, a combination of the multigroup procedure and the P{sub 3} approximation of the spherical harmonics method was chosen. The calculation was divided into two independent parts: the first part was to provide multigroup constants which serve as input data for the second part - the determination of the slow neutron spectra. In the present report only the first part of the problem will be discussed. The velocity dependence of cross-sections and scattering function in thermal range was interpreted by the monoatomic-gas model. A digital computer program was developed for the evaluation of the group values for these quantities (author00.
Energy Technology Data Exchange (ETDEWEB)
Schickler, R.A., E-mail: robert.schickler@oregonstate.edu; Marcum, W.R., E-mail: wade.marcum@oregonstate.edu; Reese, S.R.
2013-09-15
Highlights: • The Oregon State TRIGA{sup ®} Reactor neutron spectra is characterized herein. • Neutron spectra between highly enriched uranium and low enriched uranium cores are compared. • Discussion is given as to differences between HEU and LEU core spectra results and impact on experiments. -- Abstract: In 2008, the Oregon State TRIGA{sup ®} Reactor (OSTR) was converted from highly enriched uranium (HEU) fuel lifetime improvement plan (FLIP) fuel to low-enriched uranium (LEU) fuel. This effort was driven and supported by the Department of Energy's (DoE's) Reduced Enrichment for Research and Test Reactors (RERTR) program. The basis behind the RERTR program's ongoing conversion effort is to reduce the nuclear proliferation risk of civilian research and test reactors. The original intent of the HEU FLIP fuel was to provide fuel to research reactors that could be utilized for many years before a necessary refueling cycle. As a research reactor, the OSTR provides irradiation facilities for a variety of applications, such as activation analysis, fission-track dating, commercial isotope production, neutron radiography, prompt gamma characterization, and many others. In order to accurately perform these research functions, several studies had been conducted on the HEU FLIP fuel core to characterize the neutron spectra in various experimental facilities of the OSTR (Tiyapun, 1997; Ashbaker, 2005). As useful as these analyses were, they are no longer valid due to the change in fuel composition and the resulting alteration of core performance characteristics. Additionally, the core configuration (fuel reconfiguration) was altered between the HEU and LEU cores. This study characterizes the neutron spectra in various experimental facilities within and around the current LEU core. It also compares the spectra to that which was yielded in the HEU core through use of Monte Carlo n-Particle 5 (MCNP5) and experimental adjustment via a least
Nie, Y. B.; Ruan, X. C.; Ren, J.; Zhang, S.; Han, R.; Bao, J.; Huang, H. X.; Ding, Y. Y.; Wu, H. C.; Liu, P.; Zhou, Z. Y.
2017-09-01
In order to make benchmark validation of the nuclear data for gallium (Ga), tungsten (W) and beryllium (Be) in existing modern evaluated nuclear data files, neutron leakage spectra in the range from 0.8 to 15 MeV from slab samples were measured by time-of-flight technique with a BC501 scintillation detector. The measurements were performed at China Institute of Atomic Energy (CIAE) using a D-T neutron source. The thicknesses of the slabs were 0.5 to 2.5 mean free path for 14.8 MeV neutrons, and the measured angles were chosen to be 60∘ and 120∘. The measured spectra were compared with those calculated by the continuous energy Monte-Carlo transport code MCNP, using the data from the CENDL-3.1, ENDF/B-VII.1 and JENDL-4.0 nuclear data files, the comparison between the experimental and calculated results show that: The results from all three libraries significantly underestimate the cross section in energy range of 10-13 MeV for Ga; For W, the calculated spectra using data from CENDL-3.1 and JENDL-4.0 libraries show larger discrepancies with the measured ones, especially around 8.5-13.5 MeV; and for Be, all the libraries led to underestimation below 3 MeV at 120∘.
Study on keV-neutron capture cross sections and capture γ-ray spectra of 117,119Sn
International Nuclear Information System (INIS)
Nishiyama, J.; Igashira, M.; Ohsaki, T.; Kim, G.N.; Chung, W.C.; Ro, T.I.
2006-01-01
The capture cross sections and capture γ-ray spectra of 117,119 Sn were measured in an incident neutron energy region from 10 to 100 keV and at 570 keV, using a 1.5-ns pulsed neutron source by the 7 Li(p,n) 7 Be reaction and a large anti-Compton NaI(Tl) γ-ray spectrometer. A pulse-height weighting technique was applied to observed capture γ-ray pulse-height spectra to derive capture yields. The capture cross sections of 117,119 Sn were obtained with the error of about 5% by using the standard capture cross sections of 197 Au. The present cross sections were compared with previous experimental data and the evaluated values in JENDL-3.3 and ENDF/B-VI. The capture γ-ray spectra of 117,119 Sn were derived by unfolding the observed capture γ-ray pulse-height spectra. The calculations of capture cross sections and capture γ-ray spectra of 117,119 Sn were performed with the EMPIRE-II code. The calculated results were compared with the present experimental ones. (author)
International Nuclear Information System (INIS)
Okamoto, K.; Mehta, M.K.
1988-05-01
The second IAEA Research Co-ordination Meeting on Measurement and Analysis of Double-Differential Neutron Emission Spectra in (p,n) and (α,n) Reactions was convened by the IAEA Nuclear Data Section at the IAEA Headquarters in Vienna during 8-10 February, 1988. The main objectives of the Co-ordinated Research Project for which this meeting was held are (i) to extract systematic information about nuclear level densities as a function of excitation energy by analysing the neutron emission spectra from (p,n) and (α,n) reactions on properly selected targets and bombarding energy range, and (ii) to parametrize this information into appropriate phenomenological models to enable reliable extrapolation for general use of level density information in basic and applied nuclear physics related problems. Detailed conclusions and recommendations, together with a summary of the programme during 1988/1989 are attached in the Appendices
Energy Technology Data Exchange (ETDEWEB)
Lemos Junior, Roberto Mendonca de
2004-07-01
This paper aims to define a procedure to use the Bonner Multisphere Spectrometer with a {sup 6}LiI(Eu) detector in order to determine of neutron spectra. It was measured {sup 238}PuBe spectra and same of reference ({sup 241}AmBe, {sup 252}Cf e {sup 252}Cf+D{sub 2}O) published in ISO 8529-1 (2001) Norm. The data were processed by a computer program (BUNKI), which presents the results in neutrons energy fluency. Each input parameter of the program was studied in order to establish their influence in the adjustment result. The environment dose equivalent rate obtained placing the detector 1 m from the {sup 241}AmBe source was 122 {+-} 4 {mu}Sv/h with 7% of uncertainty and 95% of confidence level. The procedure established in this work was tested with the {sup 238}PuBe spectrum, obtaining an environment dose equivalent rate of 286 {+-} 9 {mu}Sv/h, 8% lower than the value measured experimentally used as reference. Through this procedure will be possible to measure neutron spectra in different work places where neutrons sources are used. Knowing these spectra, it will be possible to evaluate which area monitors, are more suitable, as well as, to study better the response of individual neutron monitors, as for instance, to obtain a conversion coefficient more appropriate to the albedo dosimeter used in different work places. As the measurements need a long time to be accomplished, the work optimization is fundamental to reduce the exposing time of the Bonner spectrometer operator. For this reason, an important parameter examined in this paper was the possibility of reducing the number of spheres used during the measurement without changing the final result. Considering the radiation protection standards, this parameter has a huge importance when the measurements are performed in work places where the neutron fluency and gamma rate offer risks to the operator's health, as for instance, in nuclear centrals. Studying this parameter, it was possible to conclude that
Maekawa, F; Wada, M; Wilson, P P H; Ikeda, Y
2000-01-01
Neutron flux spectra at an irradiation field produced by a 40-MeV deuteron bombardment on a thick lithium-target at Forschungszentrum Karlsruhe, Germany, have been determined by the multi-foil activation technique. Twenty-seven dosimetry reactions having a wide energy range of threshold energies up to 38 MeV were employed as detectors for the neutron flux spectra extending to 55 MeV. The spectra were adjusted with the SAND-II code with the experimental reaction rates based on an iterative method. The adjusted spectra validated quantitatively the Monte Carlo deuteron-lithium (d-Li) neutron source model code (M sup C DeLi) which was used to calculate initial guess spectra and also has been used for IFMIF nuclear designs. Accuracy of the adjusted spectra was approx 10% that was suitable for successive integral tests of activation cross section data.
Energy Technology Data Exchange (ETDEWEB)
Gerasimenko, B.F. [V.G. Khlopin Radium Inst., Saint Peterburg (Russian Federation)
1997-03-01
The calculations of integral spectra of prompt neutrons of spontaneous fission of {sup 244}Cm and {sup 246}Cm were carried out. The calculations were done by the Statistical Computer Code Complex SCOFIN applying the Hauser-Feschbach method as applied to the description of the de-excitation of excited fission fragments by means of neutron emission. The emission of dipole gamma-quanta from these fragments was considered as a competing process. The average excitation energy of a fragment was calculated by two-spheroidal model of tangent fragments. The density of levels in an excited fragment was calculated by the Fermi-gas model. The quite satisfactory agreement was reached between theoretical and experimental results obtained in frames of Project measurements. The calculated values of average multiplicities of neutron number were 2,746 for {sup 244}Cm and 2,927 for {sup 246}Cm that was in a good accordance with published experimental figures. (author)
Energy Technology Data Exchange (ETDEWEB)
Almen, E; Holmqvist, B; Wiedling, T
1971-09-15
The shapes of fission neutron spectra are of interest for power reactor calculations. Recently it has been suggested that the neutron induced fission spectrum of 235U may be harder than was earlier assumed. For this reason measurements of the neutron spectra of some fissile isotopes are in progress at our laboratory. This report will present results from studies of the energy spectra of the neutrons emitted in the neutron induced fission of 235U and 238U. The measurements were performed at an incident neutron energy of 0.95 MeV for 235U and at energies of 1.35 and 2.02 MeV for 238U using time-of-flight techniques. The time-of-flight spectra were only analysed at energies higher than those of the incident neutrons and up to about 10 MeV. Corrections for neutron attenuation in the uranium samples were calculated using a Monte Carlo program. The corrected fission neutron spectra were fitted to Maxwellian temperature distributions. For 235U a temperature of 1.27 +- 0.01 MeV gives the best fit to the experimental data and for 238U the corresponding values are 1.29 +- 0.03 MeV at 1.35 MeV and 1.29 +- 0.02 MeV at 2.02 MeV
International Nuclear Information System (INIS)
Kasselmann, S.; Druska, C.; Lauer, A.
2010-01-01
The energy spectra of fast and thermal neutrons from fission reactions in the FZJ code TINTE are modelled by two broad energy groups. Present demands for increased numerical accuracy led to the question of how precise the 2-group approximation is compared to a multi-group model. Therefore a new simulation program called MGT (Multi Group TINTE) has recently been developed which is able to handle up to 43 energy groups. Furthermore, an internal spectrum calculation for the determination of cross-sections can be performed for each time step and location within the reactor. In this study the multi-group energy models are compared to former calculations with only two energy groups. Different scenarios (normal operation and design-basis accidents) have been defined for a high temperature pebble bed reactor design with annular core. The effect of an increasing number of energy groups on safety-related parameters like the fuel and coolant temperature, the nuclear heat source or the xenon concentration is studied. It has been found that for the studied scenarios the use of up to 8 energy groups is a good trade-off between precision and a tolerable amount of computing time. (orig.)
International Nuclear Information System (INIS)
Halilou, A.; Lounici, A.
1981-01-01
The subject is divided in two parts: In the first part a nodal method has been worked out to solve the steady state multigroup diffusion equation. This method belongs to the same set of nodal methods currently used to calculate the exact fission powers and neutron fluxes in a very short computing time. It has been tested on a two dimensional idealized reactors. The effective multiplication factor and the fission powers for each fuel element have been calculated. The second part consists in studying and mastering the multigroup diffusion code DAHRA - a reduced version of DIANE - a two dimensional code using finite difference method
Neutron spectra calculation and doses in a subcritical nuclear reactor based on thorium
International Nuclear Information System (INIS)
Medina C, D.; Hernandez A, P. L.; Hernandez D, V. M.; Vega C, H. R.; Sajo B, L.
2015-10-01
This paper describes a heterogeneous subcritical nuclear reactor with molten salts based on thorium, with graphite moderator and a source of 252 Cf, whose dose levels in the periphery allows its use in teaching and research activities. The design was done by the Monte Carlo method with the code MCNP5 where the geometry, dimensions and fuel was varied in order to obtain the best design. The result is a cubic reactor of 110 cm side with graphite moderator and reflector. In the central part they have 9 ducts that were placed in the direction of axis Y. The central duct contains the source of 252 Cf, of 8 other ducts, are two irradiation ducts and the other six contain a molten salt ( 7 LiF - BeF 2 - ThF 4 - UF 4 ) as fuel. For design the k eff , neutron spectra and ambient dose equivalent was calculated. In the first instance the above calculation for a virgin fuel was called case 1, then a percentage of 233 U was used and the percentage of Th was decreased and was called case 2. This with the purpose to compare two different fuels working inside the reactor. In the case 1 a value was obtained for the k eff of 0.13 and case 2 of 0.28, maintaining the subcriticality in both cases. In the dose levels the higher value is in case 2 in the axis Y with a value of 3.31 e-3 ±1.6% p Sv/Q this value is reported in for one. With this we can calculate the exposure time of personnel working in the reactor. (Author)
QUANTUM NATURE OF CYCLOTRON HARMONICS IN THERMAL SPECTRA OF NEUTRON STARS
International Nuclear Information System (INIS)
Suleimanov, V. F.; Werner, K.; Pavlov, G. G.
2010-01-01
Some isolated neutron stars (NSs) show harmonically spaced absorption features in their thermal soft X-ray spectra. The interpretation of the features as a cyclotron line and its harmonics has been suggested, but the usual explanation of the harmonics as caused by relativistic effects fails because the relativistic corrections are extremely small in this case. We suggest that the features, known as quantum oscillations, correspond to the peaks in the energy dependence of the free-free opacity in a quantizing magnetic field. The peaks arise when the transitions to new Landau levels become allowed with increasing the photon energy; they are strongly enhanced by the square-root singularities in the phase-space density of quantum states in the case when the free (non-quantized) motion is effectively one dimensional. To explore observable properties of these quantum oscillations, we calculate models of hydrogen NS atmospheres with B ∼ 10 10 -10 11 G (i.e., electron cyclotron energy E c,e ∼ 0.1-1 keV) and T eff = 1-3 MK. Such conditions are thought to be typical for the so-called central compact objects in supernova remnants, such as 1E 1207.4-5209 in PKS 1209-51/52. We show that observable features at the electron cyclotron harmonics form at moderately large values of the quantization parameter, b eff ≡ E c,e /kT eff ≅ 0.5-20. The equivalent widths of the features can reach ∼100-200 eV; they grow with increasing b eff and are lower for higher harmonics.
Atmospheres and spectra of strongly magnetized neutron stars - II. The effect of vacuum polarization
Ho, Wynn C. G.; Lai, Dong
2003-01-01
We study the effect of vacuum polarization on the atmosphere structure and radiation spectra of neutron stars with surface magnetic fields B= 1014-1015 G, as appropriate for magnetars. Vacuum polarization modifies the dielectric property of the medium and gives rise to a resonance feature in the opacity; this feature is narrow and occurs at a photon energy that depends on the plasma density. Vacuum polarization can also induce resonant conversion of photon modes via a mechanism analogous to the Mikheyev-Smirnov-Wolfenstein (MSW) mechanism for neutrino oscillation. We construct atmosphere models in radiative equilibrium with an effective temperature of a few ×106 K by solving the full radiative transfer equations for both polarization modes in a fully ionized hydrogen plasma. We discuss the subtleties in treating the vacuum polarization effects in the atmosphere models and present approximate solutions to the radiative transfer problem which bracket the true answer. We show from both analytic considerations and numerical calculations that vacuum polarization produces a broad depression in the X-ray flux at high energies (a few keV <~E<~ a few tens of keV) as compared to models without vacuum polarization; this arises from the density dependence of the vacuum resonance feature and the large density gradient present in the atmosphere. Thus the vacuum polarization effect softens the high-energy tail of the thermal spectrum, although the atmospheric emission is still harder than the blackbody spectrum because of the non-grey opacities. We also show that the depression of continuum flux strongly suppresses the equivalent width of the ion cyclotron line and therefore makes the line more difficult to observe.
International Nuclear Information System (INIS)
Mi Aijun; Li Junjie
2010-01-01
In this paper the multi-group libraries were constructed by processing ENDF/B-VII neutron incident files into multi-group structure, and the application of the multi-group libraries in the pressurized-water reactor(PWR) design was studied. The construction of the multi-group library is realized by using the NJOY nuclear data processing system. The code can process the neutron cross section files form ENDF format to MATXS format which was required in SN code. Two dimension transport theory code of discrete ordinates DORT was used to verify the multi-group libraries and the method of the construction by comparing calculations for some representative benchmarks. We made the PWR shielding calculation by using the multi-group libraries and studied the influence of the parameters involved during the construction of the libraries such as group structure, temperatures and weight functions on the shielding design of the PWR. This work is the preparation for the construction of the multi-group library which will be used in PWR shielding design in engineering. (authors)
International Nuclear Information System (INIS)
Zou Jun; He Zhaozhong; Zeng Qin; Qiu Yuefeng; Wang Minghuang
2010-01-01
A multigroup library HENDL2.1/SS (Hybrid Evaluated Nuclear Data Library/Self-Shielding) based on ENDF/B-VII.0 evaluate data has been generated using Bondarenko and flux calculator method for the correction of self-shielding effect of neutronics analyses. To validate the reliability of the multigroup library HENDL2.1/SS, transport calculations for fusion-fission hybrid system FDS-I were performed in this paper. It was verified that the calculations with the HENDL2.1/SS gave almost the same results with MCNP calculations and were better than calculations with the HENDL2.0/MG which is another multigroup library without self-shielding correction. The test results also showed that neglecting resonance self-shielding caused underestimation of the K eff , neutron fluxes and waste transmutation ratios in the multigroup calculations of FDS-I.
International Nuclear Information System (INIS)
Borak, T.B.; Stinchcomb, T.G.
1979-01-01
A rapid system has been developed for computing charged-particle distributions generated in tissue by any neutron spectra less than 4 MeV. Oxygen and carbon recoils were derived from R-matrix theory, and hydrogen recoils were obtained from cross-section evaluation. Application to two quite different fission-neutron spectra demonstrates the flexibility of this method for providing spectral details of the different types of charged-particle recoils. Comparisons have been made between calculations and measurements of event-size distributions for a sphere of tissue 1 μm in diameter irradiated by these two neutron spectra. LET distributions have been calculated from computed charged-particle recoils and also derived from measurements using the conventional approximation that all charged particles traverse the chamber. The limitations of the approximation for these neutron spectra are discussed. (author)
Energy Technology Data Exchange (ETDEWEB)
Perot, B., E-mail: bertrand.perot@cea.fr [CEA, DEN, Cadarache, Nuclear Measurement Laboratory, F-13108 Saint-Paul-lez-Durance (France); El Kanawati, W.; Carasco, C.; Eleon, C. [CEA, DEN, Cadarache, Nuclear Measurement Laboratory, F-13108 Saint-Paul-lez-Durance (France); Valkovic, V. [A.C.T.d.o.o., Prilesje 4, 10000 Zagreb (Croatia); Sudac, D.; Obhodas, J. [Ruder Boskovic Institute, Bijenicka c. 54, 10000 Zagreb (Croatia); Sannie, G. [CEA, LIST, Saclay, F-91191 Gif-sur-Yvette (France)
2012-07-15
Fast neutron interrogation with the associated particle technique can be used to identify explosives in cargo containers (EURITRACK FP6 project) and unexploded ordnance on the seabed (UNCOSS FP7 project), by detecting gamma radiations induced by 14 MeV neutrons produced in the {sup 2}H({sup 3}H,{alpha})n reaction. The origin of the gamma rays can be determined in 3D by the detection of the alpha particle, which provides the direction of the opposite neutron and its time-of-flight. Gamma spectroscopy provides the relative counts of carbon, nitrogen, and oxygen, which are converted to chemical fractions to differentiate explosives from other organic substances. To this aim, Monte Carlo calculations are used to take into account neutron moderation and gamma attenuation in cargo materials or seawater. This paper presents an experimental verification that C, N, and O counts are correctly reproduced by numerical simulation. A quantitative comparison is also reported for silicon, iron, lead, and aluminium. - Highlights: Black-Right-Pointing-Pointer Gamma-ray spectra produced by 14 MeV neutrons in C, N, O, Si, Al, Fe, and Pb elements. Black-Right-Pointing-Pointer Quantitative comparison with MCNPX simulations using the ENDF/B-VII.0 library. Black-Right-Pointing-Pointer C, N, and O counts correctly reproduced and chemical proportions recovered using calculation. Black-Right-Pointing-Pointer Application to the detection of explosives or illicit drugs in cargo containers.
Spectra of fast neutrons using a lithiated glass film on silicon
International Nuclear Information System (INIS)
Wallace, Steven; Stephan, Andrew C.; Womble, Phillip C.; Begtrup, Gavi; Dai Sheng
2003-01-01
Experimental results of a neutron detector manufactured by coating a silicon charged particle detector with a film of lithiated glass are presented. The silicon surface barrier detector (SBD) responds to the 6 Li(n, alpha)triton reaction products generated in the thin film of lithiated glass entering the SBD. Neutron spectral information is present in the pulse height spectrum. An energy response is seen that clearly shows that neutrons from a Pu-Be source and from a deuterium-tritium (D-T) pulsed neutron generator can be differentiated and counted above a gamma background. The significant result is that the fissile content within a container can be measured using a pulsed D-T neutron generator using the neutrons that are counted in the interval between the pulses
International Nuclear Information System (INIS)
Oparaji, U.; Tsai, Y. H.; Liu, Y. C.; Lee, K. W.; Patelli, E.; Sheu, R. J.
2017-01-01
This paper presents improved and extended results of our previous study on corrections for conventional neutron dose meters used in environments with high-energy neutrons (E n > 10 MeV). Conventional moderated-type neutron dose meters tend to underestimate the dose contribution of high-energy neutrons because of the opposite trends of dose conversion coefficients and detection efficiencies as the neutron energy increases. A practical correction scheme was proposed based on analysis of hundreds of neutron spectra in the IAEA-TRS-403 report. By comparing 252 Cf-calibrated dose responses with reference values derived from fluence-to-dose conversion coefficients, this study provides recommendations for neutron field characterization and the corresponding dose correction factors. Further sensitivity studies confirm the appropriateness of the proposed scheme and indicate that (1) the spectral correction factors are nearly independent of the selection of three commonly used calibration sources: 252 Cf, 241 Am-Be and 239 Pu-Be; (2) the derived correction factors for Bonner spheres of various sizes (6''-9'') are similar in trend and (3) practical high-energy neutron indexes based on measurements can be established to facilitate the application of these correction factors in workplaces. (authors)
Czech Academy of Sciences Publication Activity Database
Králík, M.; Krása, Josef; Velyhan, Andriy; Scholz, M.; Ivanova-Stanik, I.M.; Bienkowska, B.; Miklaszewski, R.; Schmidt, H.; Řezáč, K.; Klír, D.; Kravárik, J.; Kubeš, P.
2010-01-01
Roč. 81, č. 11 (2010), 113503/1-113503/5 ISSN 0034-6748 R&D Projects: GA MŠk LA08024 Grant - others:FP-6 EU(XE) RITA-CT2006-26095 Institutional research plan: CEZ:AV0Z10100523 Keywords : plasma focus * fusion DD neutrons * Bonner sphere spectrometer * energy spectra of scattered neutrons * unfolded and calculated spectra Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 1.598, year: 2010
Discrimination of neutrons and gamma quanta with the aid of their power density spectra
International Nuclear Information System (INIS)
Buchmueller, R.
1977-01-01
The paper introduces a method of using only one fission chamber to discriminate the neutron flux against the gamma flux. The gamma chamber current may be several orders of magnitude higher than the neutron chamber current. In specially dimensioned fission chambers the neutrons and gamma quanta are made to generate different current pulses. Discrimination becomes possible by recording the power density spectrum of the mixture of pulses over a broad frequency range ( [de
International Nuclear Information System (INIS)
Genta, Philippe; Millet, Francois; Vezin, Robert.
1975-01-01
Bernstein simplifying hypotheses are used to describe the FOCUS plasma producing nuclear reactions, by means of two populations: the accelerated deuterons described by the space-time mean value of their single velocity distribution f 1 (E(d), theta(d)); and a beam of target deuterons with a kinetic energy E(T). The neutron spectrum S(M)(P 0 ,E,theta(n)) being obtained by a time-of-flight measurement, a possible determination of the function f 1 (E(d), theta(d)) giving the same spectrum is developed. When theta(n) is not zero, the Gauss-Legendre two-step method used for the programming allows a precise computation for the infinite branches. There is no difficulty in the case where theta(n)=0,π. A discrete solution is developed from two or three different values of theta(n) and a ten energy values with 100keV steps. The minimization leads to solving a linear system by the Gauss-Seidel method [fr
International Nuclear Information System (INIS)
Paul, Sabyasachi; Sahoo, G. S.; Tripathy, S. P.; Sunil, C.; Bandyopadhyay, T.; Sharma, S. C.; Ramjilal,; Ninawe, N. G.; Gupta, A. K.
2014-01-01
A systematic study on the measurement of neutron spectra emitted from the interaction of protons of various energies with a thick beryllium target has been carried out. The measurements were carried out in the forward direction (at 0° with respect to the direction of protons) using CR-39 detectors. The doses were estimated using the in-house image analyzing program autoTRAK-n, which works on the principle of luminosity variation in and around the track boundaries. A total of six different proton energies starting from 4 MeV to 24 MeV with an energy gap of 4 MeV were chosen for the study of the neutron yields and the estimation of doses. Nearly, 92% of the recoil tracks developed after chemical etching were circular in nature, but the size distributions of the recoil tracks were not found to be linearly dependent on the projectile energy. The neutron yield and dose values were found to be increasing linearly with increasing projectile energies. The response of CR-39 detector was also investigated at different beam currents at two different proton energies. A linear increase of neutron yield with beam current was observed
WINTOF - A program to produce neutron spectra from Zebra time-of-flight experiments
International Nuclear Information System (INIS)
Marshall, J.
1969-06-01
This report describes a computer program, written for the Winfrith KDF9 computer, which is used to calculate the neutron energy spectrum in the Zebra reactor from neutron time-of-flight measurements using the Zebra Linac. The data requirements for the program are specified and an illustration of the final spectrum is included. (author)
International Nuclear Information System (INIS)
Noda, S.; Haight, R. C.; Nelson, R. O.; Devlin, M.; O'Donnell, J. M.; Chatillon, A.; Granier, T.; Belier, G.; Taieb, J.; Kawano, T.; Talou, P.
2011-01-01
Prompt fission neutron spectra from 235 U and 239 Pu were measured for incident neutron energies from 1 to 200 MeV at the Weapons Neutron Research facility (WNR) of the Los Alamos Neutron Science Center, and the experimental data were analyzed with the Los Alamos model for the incident neutron energies of 1-8 MeV. A CEA multiple-foil fission chamber containing deposits of 100 mg 235 U and 90 mg 239 Pu detected fission events. Outgoing neutrons were detected by the Fast Neutron-Induced γ-Ray Observer array of 20 liquid organic scintillators. A double time-of-flight technique was used to deduce the neutron incident energies from the spallation target and the outgoing energies from the fission chamber. These data were used for testing the Los Alamos model, and the total kinetic energy parameters were optimized to obtain a best fit to the data. The prompt fission neutron spectra were also compared with the Evaluated Nuclear Data File (ENDF/B-VII.0). We calculate average energies from both experimental and calculated fission neutron spectra.
Analysis of the neutron time-of-flight spectra from inertial confinement fusion experiments
Energy Technology Data Exchange (ETDEWEB)
Hatarik, R., E-mail: hatarik1@llnl.gov; Sayre, D. B.; Caggiano, J. A.; Phillips, T.; Eckart, M. J.; Bond, E. J.; Cerjan, C.; Grim, G. P.; Hartouni, E. P.; Mcnaney, J. M.; Munro, D. H. [Lawrence Livermore National Laboratory, Livermore, California 94550 (United States); Knauer, J. P. [Laboratory for Laser Energetics, University of Rochester, Rochester, New York 14623 (United States)
2015-11-14
Neutron time-of-flight diagnostics have long been used to characterize the neutron spectrum produced by inertial confinement fusion experiments. The primary diagnostic goals are to extract the d + t → n + α (DT) and d + d → n + {sup 3}He (DD) neutron yields and peak widths, and the amount DT scattering relative to its unscattered yield, also known as the down-scatter ratio (DSR). These quantities are used to infer yield weighted plasma conditions, such as ion temperature (T{sub ion}) and cold fuel areal density. We report on novel methodologies used to determine neutron yield, apparent T{sub ion}, and DSR. These methods invoke a single temperature, static fluid model to describe the neutron peaks from DD and DT reactions and a spline description of the DT spectrum to determine the DSR. Both measurements are performed using a forward modeling technique that includes corrections for line-of-sight attenuation and impulse response of the detection system. These methods produce typical uncertainties for DT T{sub ion} of 250 eV, 7% for DSR, and 9% for the DT neutron yield. For the DD values, the uncertainties are 290 eV for T{sub ion} and 10% for the neutron yield.
International Nuclear Information System (INIS)
Erdtmann, G.
1993-08-01
A sufficiently accurate characterization of the neutron flux and spectrum, i.e. the determination of the thermal flux, the flux ratio and the epithermal flux spectrum shape factor, α, is a prerequisite for all types of absolute and monostandard methods of reactor neutron activation analysis. A convenient method for these measurements is the bare triple monitor method. However, the results of this method, are very imprecise, because there are high error propagation factors form the counting errors of the monitor activities. Procedures are described to calculate the errors of the flux parameters, the α-dependent cross-section ratios, and of the analytical results from the errors of the activities of the monitor isotopes. They are included in FORTRAN programs which also allow a graphical representation of the results. A great number of examples were calculated for ten different irradiation facilities in four reactors and for 28 elements. Plots of the results are presented and discussed. (orig./HP) [de
Neutron emission spectra and level density of hot rotating 132Sn
International Nuclear Information System (INIS)
Aggarwal, Mamta
2008-01-01
The neutron emission spectrum of the highly excited compound nuclear system 132 Sn is investigated at high spin. The doubly magic nucleus 132 Sn undergoes a shape transition at high angular momentum which affects the nuclear level density and neutron emission probability considerably. The interplay of temperature, shape, deformation and rotational degrees of freedom and their influence on neutron emission is emphasized. We predict an enhancement of nucleonic emission at those spins where the nucleus suffers a transition from a spherical to deformed shape. (author)
International Nuclear Information System (INIS)
Calamand, D.; Desprets, A.; Rancurel, H.
1977-01-01
The first results of a joint CEA/CNEN neutron propagation program conducted on the source reactors HARMONIE and TAPIRO are presented. In both cases, a buffer zone representative of the blanket of a commercial fast power reactor is interposed between the source reactor and the medium in which neutron propagation is measured. This buffer zone provides a realistic source spectrum to be propagated. Experimental results are compared to older results obtained without the buffer zone. The effect of the source spectrum on neutron propagation is discussed, as well as the coherence of the results obtained with the two installations
Jansky, Bohumil; Rejchrt, Jiri; Novak, Evzen; Losa, Evzen; Blokhin, Anatoly I.; Mitenkova, Elena
2017-09-01
The leakage neutron spectra measurements have been done on benchmark spherical assemblies - iron spheres with diameter of 20, 30, 50 and 100 cm. The Cf-252 neutron source was placed into the centre of iron sphere. The proton recoil method was used for neutron spectra measurement using spherical hydrogen proportional counters with diameter of 4 cm and with pressure of 400 and 1000 kPa. The neutron energy range of spectrometer is from 0.1 to 1.3 MeV. This energy interval represents about 85 % of all leakage neutrons from Fe sphere of diameter 50 cm and about of 74% for Fe sphere of diameter 100 cm. The adequate MCNP neutron spectra calculations based on data libraries CIELO, JEFF-3.2 and ENDF/B-VII.1 were done. Two calculations were done with CIELO library. The first one used data for all Fe-isotopes from CIELO and the second one (CIELO-56) used only Fe-56 data from CIELO and data for other Fe isotopes were from ENDF/B-VII.1. The energy structure used for calculations and measurements was 40 gpd (groups per decade) and 200 gpd. Structure 200 gpd represents lethargy step about of 1%. This relatively fine energy structure enables to analyze the Fe resonance neutron energy structure. The evaluated cross section data of Fe were validated on comparisons between the calculated and experimental spectra.
International Nuclear Information System (INIS)
Yildirim, G.
2008-01-01
In the present study, the (p,xn) reaction neutron-emission spectra for some amphoter target nuclei as 27 A l, 64 Z n, 120 S n, and 208 P b were investigated up to 140 MeV incident proton energy. The pre-equilibrium calculations were calculated by using the hybrid model, the geometry dependent hybrid model, the full exciton model and the cascade exciton model. The reaction equilibrium component was calculated with a traditional compound nucleus model developed by Weisskopf Ewing. Calculation results have been discussed and compared with the available experimental data in literature
Measurements of Neutron Spectra Produced from a Thick Iron Target Bombarded with 1.5-GeV Protons
International Nuclear Information System (INIS)
Meigo, Shin-ichiro; Shigyo, Nobuhiro; Iga, Kiminori; Iwamoto, Yosuke; Kitsuki, Hirohiko; Ishibashi, Kenji; Maehata, Keisuke; Arima, Hidehiko; Nakamoto, Tatsushi; Numajiri, Masaharu
2005-01-01
For validation of calculation codes that are employed in the design of accelerator facilities, spectra of neutrons produced from a thick iron target bombarded with 1.5-GeV protons were measured. The calculated results with NMTC/JAM were compared with the present experimental results. It is found that the NMTC/JAM generally shows good agreement with experiment. Furthermore, the calculation gives good agreement with the experiment for the energy region 20 to 80 MeV for iron, whereas the NMTC/JAM gives 50% of the experimental data for the heavy-nuclides such as lead and tungsten
Measurements of neutron spectra produced from a thick iron target bombarded with 1.5 GeV protons
International Nuclear Information System (INIS)
Meigo, Shin-ichiro; Takada, Hiroshi
2001-01-01
For validation of calculation codes which are employed in the design of accelerator facilities, spectra of neutrons produced from a thick iron target bombarded with 1.5-GeV protons were measured. The calculated results with NMTC/JAM were compared with the present experimental results. It is found the NMTC/JAM generally shows in good agreement with experiment. Furthermore, the calculation gives good agreement with the experiment for the energy region 20-80 MeV, whereas the NMTC/JAM gives 50% of the experimental data for the heavy nuclide target such as lead and tungsten target. (author)
Spectra and absorbed dose by photo-neutrons in a solid water mannequin exposed to a Linac of 15 MV
International Nuclear Information System (INIS)
Benites R, J.; Vega C, H. R.; Velazquez F, J.
2012-10-01
Using Monte Carlo methods was modeled a solid water mannequin; according to the ICRU 44 (1989), Tissue substitutes in radiation dosimetry and measurements, of the International Commission on Radiation Units and Measurements; Report 44. This material Wt 1 is made of H (8.1%), C (67.2%), N (2.4%), O (19.9%), Cl (0.1%), Ca (2.3%) and its density is of 1.02 gr/cm 3 . The mannequin was put instead of the patient, inside the treatment room and the spectra and absorbed dose were determined by photo-neutrons exposed to a Linac of 15 MV. (Author)
International Nuclear Information System (INIS)
Deutsch, R.; Herold, H.; Kaeppeler, H.J.; Schmidt, H.
1982-07-01
In order to analyse the influence of the deviation from the equilibrium distribution of the fast deuterons on the neutron spectrum, the limiting case, corresponding to a two-dimensional mono-energetic deuteron distribution, was studied. An essential difference in comparison to the equilibrium case is the appearance of a pronounced peak in the side-on spectra at Esub(n)approx.=2.5 MeV. A comparison of the theoretical and experimental data was made. If we take into account the relaxation processes, there results a good agreement between theory and experiment. (orig.)
Thermal neutron spectra measurements in IEAR-1 Reactor, by using a crystal spectrometer
International Nuclear Information System (INIS)
Fulfaro, R.; Figueiredo Neto, A.M.; Stasiulevicius, E.; Vinhas, L.A.
1975-01-01
The thermal neutron spectrum of the IEN Argonauta reactor has been measured in the wavelength from 0.7 to 1.9A, using a neutron crystal spectrometer. An aluminium single crystal, in transmission, was used as monochromator. The aluminium crystal reflectivity employed in the analysis of the data was calculated for the first five permitted orders. An effective absorption coefficient of the crystal was used to perform the calculations instead of the macroscopic cross section of the element
Horsewill, A J; Goh, K; Rols, S; Ollivier, J; Johnson, M R; Levitt, M H; Carravetta, M; Mamone, S; Murata, Y; Chen, J Y-C; Johnson, J A; Lei, X; Turro, N J
2013-09-13
The quantum dynamics of a hydrogen molecule encapsulated inside the cage of a C60 fullerene molecule is investigated using inelastic neutron scattering (INS). The emphasis is on the temperature dependence of the INS spectra which were recorded using time-of-flight spectrometers. The hydrogen endofullerene system is highly quantum mechanical, exhibiting both translational and rotational quantization. The profound influence of the Pauli exclusion principle is revealed through nuclear spin isomerism. INS is shown to be exceptionally able to drive transitions between ortho-hydrogen and para-hydrogen which are spin-forbidden to photon spectroscopies. Spectra in the temperature range 1.6≤T≤280 K are presented, and examples are given which demonstrate how the temperature dependence of the INS peak amplitudes can provide an effective tool for assigning the transitions. It is also shown in a preliminary investigation how the temperature dependence may conceivably be used to probe crystal field effects and inter-fullerene interactions.
Energy Technology Data Exchange (ETDEWEB)
Silva, Davi J.M.; Nunes, Carlos E.A.; Alves Filho, Hermes; Barros, Ricardo C., E-mail: davijmsilva@yahoo.com.br, E-mail: ceanunes@yahoo.com.br, E-mail: rcbarros@pq.cnpq.br [Secretaria Municipal de Educacao de Itaborai, RJ (Brazil); Universidade Estacio de Sa (UNESA), Rio de Janeiro, RJ (Brazil); Universidade do Estado do Rio de Janeiro (UERJ), Novra Friburgo, RJ (Brazil). Instituto Politecnico. Departamento de Modelagem Computacional
2017-11-01
Discussed here is the accuracy of approximate albedo boundary conditions for energy multigroup discrete ordinates (S{sub N}) eigenvalue problems in two-dimensional rectangular geometry for criticality calculations in neutron fission reacting systems, such as nuclear reactors. The multigroup (S{sub N}) albedo matrix substitutes approximately the non-multiplying media around the core, e.g., baffle and reflector, as we neglect the transverse leakage terms within these non-multiplying regions. Numerical results to a typical model problem are given to illustrate the accuracy versus the computer running time. (author)
International Nuclear Information System (INIS)
Huang, Mi; Yi, Ce; Manalo, Kevin L.; Sjoden, Glenn E.
2011-01-01
Multigroup optimization is performed on a neutron detector assembly to examine the validity of transport response in forward and adjoint modes. For SN transport simulations, we discuss the multigroup collapse of an 80 group library to 40, 30, and 16 groups, constructed from using the 3-D parallel PENTRAN and macroscopic cross section collapsing with YGROUP contribution weighting. The difference in using P_1 and P_3 Legendre order in scattering cross sections is investigated; also, associated forward and adjoint transport responses are calculated. We conclude that for the block analyzed, a 30 group cross section optimizes both computation time and accuracy relative to the 80 group transport calculations. (author)
Multi-level methods for solving multigroup transport eigenvalue problems in 1D slab geometry
International Nuclear Information System (INIS)
Anistratov, D. Y.; Gol'din, V. Y.
2009-01-01
A methodology for solving eigenvalue problems for the multigroup neutron transport equation in 1D slab geometry is presented. In this paper we formulate and compare different variants of nonlinear multi-level iteration methods. They are defined by means of multigroup and effective one-group low-order quasi diffusion (LOQD) equations. We analyze the effects of utilization of the effective one-group LOQD problem for estimating the eigenvalue. We present numerical results to demonstrate the performance of the iteration algorithms in different types of reactor-physics problems. (authors)
Multi-level nonlinear diffusion acceleration method for multigroup transport k-Eigenvalue problems
International Nuclear Information System (INIS)
Anistratov, Dmitriy Y.
2011-01-01
The nonlinear diffusion acceleration (NDA) method is an efficient and flexible transport iterative scheme for solving reactor-physics problems. This paper presents a fast iterative algorithm for solving multigroup neutron transport eigenvalue problems in 1D slab geometry. The proposed method is defined by a multi-level system of equations that includes multigroup and effective one-group low-order NDA equations. The Eigenvalue is evaluated in the exact projected solution space of smallest dimensionality, namely, by solving the effective one- group eigenvalue transport problem. Numerical results that illustrate performance of the new algorithm are demonstrated. (author)
Neutron energy spectra of sup 2 sup 5 sup 2 Cf, Am-Be source and of the D(d,n) sup 3 He reaction
Sang Tae Park
2003-01-01
The neutron energy spectrum of the following sources were measured using a fast neutron spectrometer with the NE-213 liquid scintillator: sup 2 sup 5 sup 2 Cf, Am-Be and D(d,n) sup 3 He reaction from a 3 MeV Pelletron accelerator in Tokyo Institute of Technology. The measured proton recoil pulse height data of sup 2 sup 5 sup 2 Cf, Am-Be and D(d,n) sup 3 He were unfolded using the mathematical program to obtain the neutron energy spectrum. The sup 2 sup 5 sup 2 Cf and Am-Be neutron energy spectra were measured and the results obtained showed a good agreement with the spectra usually published in the literature. The neutron energy spectrum from D(d,n) sup 3 He was measured and the results obtained also showed a good agreement with the calculation by time of flight (TOF) methods. (author)
Ichihara, C; Hayashi, S A; Yamamoto, J; Takahashi, A
2003-01-01
In order to make a benchmark validation of the nuclear data for Zr, the leakage neutron spectrum from a Zr sphere of a 61-cm diameter was measured between 0.1 and 16MeV using a time-of-flight technique with a 14MeV neutron source facility, OKTAVIAN. The result was compared with the calculation using the Monte Carlo code MCNP-4A. To investigate the spectrum dependence on the individual neutron reactions, test calculations were carried out with the MCNP-4A code using the JENDL-3.2-based libraries, in which partial cross section values were reduced from the original values. From the comparison between the measured and the calculated spectra, it was found that each of the results could predict well the experiment in general. However, in detail, both ENDF/B-VI and EFF-2.4 gave considerable overestimation above 1 MeV. The JENDL-3.2 predicts the spectrum almost satisfactorily except below 0.8 MeV and around 10 MeV. The discrepancy found in JENDL-3.2 calculation is considered due to the cross section values of the (n...
Energy Technology Data Exchange (ETDEWEB)
Park, Ho Jin; Cho, Jin Young [KAERI, Daejeon (Korea, Republic of); Kim, Kang Seog [Oak Ridge National Laboratory, Oak Ridge (United States); Hong, Ser Gi [Kyung Hee University, Yongin (Korea, Republic of)
2016-05-15
In this study, multi-group cross section libraries for the DeCART code were generated using a new procedure. The new procedure includes generating the RI tables based on the MC calculations, correcting the effective fission product yield calculations, and considering most of the fission products as resonant nuclides. KAERI (Korea Atomic Energy Research Institute) has developed the transport lattice code KARMA (Kernel Analyzer by Ray-tracing Method for fuel Assembly) and DeCART (Deterministic Core Analysis based on Ray Tracing) for a multi-group neutron transport analysis of light water reactors (LWRs). These codes adopt the method of characteristics (MOC) to solve the multi-group transport equation and resonance fixed source problem, the subgroup and the direct iteration method with resonance integral tables for resonance treatment. With the development of the DeCART and KARMA code, KAERI has established its own library generation system for a multi-group transport calculation. In the KAERI library generation system, the multi-group average cross section and resonance integral (RI) table are generated and edited using PENDF (point-wise ENDF) and GENDF (group-wise ENDF) produced by the NJOY code. The new method does not need additional processing because the MC method can handle any geometry information and material composition. In this study, the new method is applied to the dominant resonance nuclide such as U{sup 235} and U{sup 238} and the conventional method is applied to the minor resonance nuclides. To examine the newly generated multi-group cross section libraries, various benchmark calculations such as pin-cell, FA, and core depletion problem are performed and the results are compared with the reference solutions. Overall, the results by the new method agree well with the reference solution. The new procedure based on the MC method were verified and provided the multi-group library that can be used in the SMR nuclear design analysis.
Time-of-flight techniques applied to neutron spectra measurements in fast subcritical assemblies
International Nuclear Information System (INIS)
Rotival, Michel
1975-04-01
Time-of-flight measurements on Uranium-Graphite assemblies were performed using the BCMN linear accelerator. Methods to provide scalar spectra averaged over a core cell from these experimental results are described [fr
Determination of proton and neutron spectra in the LANSCE spallation irradiation facility
International Nuclear Information System (INIS)
James, M.R.; Maloy, S.A.; Sommer, W.F.; Fowler, M.M.; Dry, D.; Ferguson, P.D.; Mueller, G.; Corzine, R.K.
1999-01-01
Materials samples were recently irradiated in the Los Alamos Radiation Effects Facility (LASREF) at the Los Alamos Neutron Science Center (LANSCE) to provide data for the Accelerator Production of Tritium (APT) project on the effect of irradiation on the mechanical and physical properties of materials. The targets were configured to expose samples to a variety of radiation environments including, high-energy protons, mixed protons and high-energy neutrons, and low-energy neutrons. The samples were irradiated for approximately six months during a ten month period using an 800 MeV proton beam with a circular Gaussian shape of approximately 2σ = 3.0 cm. At the end of this period, the samples were extracted and tested. Activation foils were also extracted that had been placed in proximity to the materials samples. These were used to quantify the fluences in various locations
Neutron Spectra, Fluence and Dose Rates from Bare and Moderated Cf-252 Sources
Energy Technology Data Exchange (ETDEWEB)
Radev, Radoslav P. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
2016-04-01
A new, stronger ^{252}Cf source (serial number SR-CF-3050-OR) was obtained from Oak Ridge National Laboratory (ORNL) in 2014 to supplement the existing ^{252}Cf sources which had significantly decayed. A new instrument positioning track system was designed and installed by Hopewell Designs, Inc. in 2011. The neutron field from the new, stronger ^{252}Cf source in the modified calibration environment needed to be characterized as well as the modified neutron fields produced by the new source and seven different neutron moderators. Comprehensive information about our ^{252}Cf source, its origin, production, and isotopic content and decay characteristics needed to be compiled as well. This technical report is intended to address these issues.
The holistic analysis of gamma-ray spectra in instrumental neutron activation analysis
Energy Technology Data Exchange (ETDEWEB)
Blaauw, M
1993-11-15
The subject is the computerized analysis of the gamma-ray spectra in INAA. This analysis can be separated in three parts: The conversion of the spectra to information on {gamma}-ray energies and their relative intensities (spectrum reduction), the determination of the relation between the intensity of a {gamma}-ray and the amount of the corresponding element present in the sample (standardization) and the attribution of the {gamma}-ray energies to the elements, including the subsequent computation of the amounts of the elements (interpretation). A {gamma}-ray spectrum can be considered to be the linear sum of the {gamma}-ray spectra of the individual radionuclides present in the sample. Knowing the relative activities of the different radionuclides that may be produced by activation of a single element, a {gamma}-ray spectrum in INAA can also be considered to be the linear sum of the spectra of the elements. This principle has hitherto not been used in INAA to analyze the spectra by linear least squares methods, using all {gamma}-ray energies observed in the spectrum. The implementation of this `holistic` approach required that attention be paid to both spectrum reduction, standardization and interpretation. The thesis describes the methods developed for the holistic analysis of {gamma}-ray spectra in INAA, and present results of experimental comparisons between the holistic and other approaches. (orig./HP).
The holistic analysis of gamma-ray spectra in instrumental neutron activation analysis
International Nuclear Information System (INIS)
Blaauw, M.
1993-01-01
The subject is the computerized analysis of the gamma-ray spectra in INAA. This analysis can be separated in three parts: The conversion of the spectra to information on γ-ray energies and their relative intensities (spectrum reduction), the determination of the relation between the intensity of a γ-ray and the amount of the corresponding element present in the sample (standardization) and the attribution of the γ-ray energies to the elements, including the subsequent computation of the amounts of the elements (interpretation). A γ-ray spectrum can be considered to be the linear sum of the γ-ray spectra of the individual radionuclides present in the sample. Knowing the relative activities of the different radionuclides that may be produced by activation of a single element, a γ-ray spectrum in INAA can also be considered to be the linear sum of the spectra of the elements. This principle has hitherto not been used in INAA to analyze the spectra by linear least squares methods, using all γ-ray energies observed in the spectrum. The implementation of this 'holistic' approach required that attention be paid to both spectrum reduction, standardization and interpretation. The thesis describes the methods developed for the holistic analysis of γ-ray spectra in INAA, and present results of experimental comparisons between the holistic and other approaches. (orig./HP)
BCG: a code for calculating pointwise neutron spectra and criticality in fast reactor cells
International Nuclear Information System (INIS)
Leite, S.B.; Caldeira, A.D.; Garcia, R.D.M.
1988-02-01
The BCG code for determining the space and energy neutron flux distribution and criticality of fast reactor cylindrical cells is presented. The code solves the unidimensional neutron transport equation together with interface current relations at each energy in an unionized grid prepared for the cell and at an arbitrary number of spatial zones. While the spatial resolution is user specified, the energy dependence of the flux distribution is resolved according to the degree of variation in the reconstructed total microscopic cross sections of the atomic species in the cell. Results for a defined sample problem illustrate the high resolution and accuracy that can be obtained with the code. (author) [pt
BCG: a computer code for calculating neutron spectra and criticality in cells of fast reactors
International Nuclear Information System (INIS)
Leite, S.B.; Caldeira, A.D.; Garcia, R.D.M.
1988-01-01
The BCG code for determining the space and energy neutron flux distribution and criticality of fast reactor cylindrical cells is discussed. The code solves the unidimensional neutron transport equation together with interface current relations at each energy point in an unionized energy grid prepared for the cell and at an arbitrary number of spatial zones. While the spatial resolution is user specified, the energy dependence of the flux distribution is resolved according to the degree of variation in the reconstruced total microscopic cross sections of the atomic species in the cell. Results for a simplified fuel cell illustrate the high resolution and accuracy that can be obtained with the code. (author) [pt
Energy Technology Data Exchange (ETDEWEB)
Yücel, Haluk [Ankara University, Institute of Nuclear Sciences, 06100 Tandogan, Ankara (Turkey); Budak, Mustafa Guray, E-mail: mbudak@gazi.edu.tr [Gazi University, Gazi Education Faculty, 06500 Teknikokullar, Ankara (Turkey); Karadag, Mustafa [Gazi University, Gazi Education Faculty, 06500 Teknikokullar, Ankara (Turkey); Yüksel, Alptuğ Özer [Ankara University, Institute of Nuclear Sciences, 06100 Tandogan, Ankara (Turkey)
2014-11-01
Highlights: • An irradiation unit was installed using a 37 GBq {sup 241}Am-Be neutron source. • The source neutrons moderated by using both water and paraffin. • Irradiation unit was shielded by boron oxide and lead against neutrons and gammas. • There are two sites for irradiations, one of them has a pneumatic transfer system. • Cadmium ratio method was used for irradiation site characterization. - Abstract: For the applicability of instrumental neutron activation analysis (NAA) technique, an irradiation unit with a 37 GBq {sup 241}Am-Be neutron source was installed at Institute of Nuclear Sciences of Ankara University. Design and configuration properties of the irradiation unit are described. It has two different sample irradiation positions, one is called site #1 having a pneumatic sample transfer system and the other is site #2 having a location for manual use. In order to characterize neutron flux spectra in the irradiation sites, the measurement results were obtained for thermal (φ{sub th}) and epithermal neutron fluxes (φ{sub epi}), thermal to epithermal flux ratio (f) and epithermal spectrum shaping factors (α) by employing cadmium ratios of gold (Au) and molybdenum (Mo) monitors. The activities produced in these foils were measured by using a p-type, 44.8% relative efficiency HPGe well detector. For the measured γ-rays, self-absorption and true coincidence summing effects were taken into account. Additionally, thermal neutron self-shielding and resonance neutron self-shielding effects were taken into account in the measured results. For characterization of site #1, the required parameters were found to be φ{sub th} = (2.11 ± 0.05) × 10{sup 3} n cm{sup −2} s{sup −1}, φ{sub epi} = (3.32 ± 0.17) × 10{sup 1} n cm{sup −2} s{sup −1}, f = 63.6 ± 1.5, α = 0.045 ± 0.009, respectively. Similarly, those parameters were measured in site #2 as φ{sub th} = (1.49 ± 0.04) × 10{sup 3} n cm{sup −2} s{sup −1}, φ{sub epi} = (2.93 ± 0
Koliopanos, Filippos; Vasilopoulos, Georgios; Godet, Olivier; Bachetti, Matteo; Webb, Natalie A.; Barret, Didier
2017-12-01
Aims: In light of recent discoveries of pulsating ultraluminous X-ray sources (ULXs) and recently introduced theoretical schemes that propose neutron stars (NSs) as the central engines of ULXs, we revisit the spectra of eighteen well known ULXs, in search of indications that favour this newly emerging hypothesis. Methods: We examine the spectra from high-quality XMM-Newton and NuSTAR observations. We use a combination of elementary black body and multicolour disk black body (MCD) models, to diagnose the predictions of classic and novel theoretical models of accretion onto NSs. We re-interpret the well established spectral characteristics of ULXs in terms of accretion onto lowly or highly magnetised NSs, and explore the resulting parameter space for consistency. Results: We confirm the previously noted presence of the low-energy (≲6 keV) spectral rollover and argue that it could be interpreted as due to thermal emission. The spectra are well described by a double thermal model consisting of a "hot" (≳1 keV) and a "cool" (≲0.7 keV) multicolour black body (MCB). Under the assumption that the "cool" MCD emission originates in a disk truncated at the neutron star magnetosphere, we find that all ULXs in our sample are consistent with accretion onto a highly magnetised (B ≳ 1012 G) neutron star. We note a strong correlation between the strength of the magnetic field, the temperature of the "hot" thermal component and the total unabsorbed luminosity. Examination of the NuSTAR data supports this interpretation and also confirms the presence of a weak, high-energy (≳15 keV) tail, most likely the result of modification of the MCB emission by inverse Compton scattering. We also note that the apparent high-energy tail, may simply be the result of mismodelling of MCB emission with an atypical temperature (T) versus radius (r) gradient, using a standard MCD model with a fixed gradient of T r-0.75. Conclusions: We have offered a new and robust physical interpretation for
International Nuclear Information System (INIS)
Kojima, Kensuke; Okumura, Keisuke; Kosako, Kazuaki; Torii, Kazutaka
2016-01-01
At the decommissioning of light water reactors (LWRs), it is important to evaluate an amount of radioactivity in the ex-core structures such as a reactor containment vessel, radiation shieldings, and so on. It is thought that the leakage neutron spectra in these radioactivation regions, which strongly affect the induced radioactivity, would be changed by different reactor core configurations such as fuel assembly loading pattern and fuel burnups. This study was intended to evaluate these effects. For this purpose, firstly, partial neutron currents on the core surfaces were calculated for some core configurations. Then, the leakage neutron flux spectra in major radioactivation regions were calculated based on the provided currents. Finally, influence of the core configurations upon the neutron flux spectra was evaluated. As a result, it has been found that the influence is small on the spectrum shapes of neutron fluxes. However, it is necessary to pay attention to the facts that intensities of the leakage neutron fluxes are changed by the configurations and that intensities and spectrum shapes of the leakage neutron fluxes are changed depending on the angular direction around the core. (author)
Iwamoto, Y; Nakamura, T; Nakashima, H; Mares, V; Itoga, T; Matsumoto, T; Nakane, Y; Feldbaumer, E; Jaegerhofer, L; Pioch, C; Tamii, A; Satoh, D; Masuda, A; Sato, T; Iwase, H; Yashima, H; Nishiyama, J; Hagiwara, M; Hatanaka, K; Sakamoto, Y
2011-01-01
The authors measured the neutron energy spectra of a quasi-monoenergetic (7)Li(p,n) neutron source with 246 and 389 MeV protons set at seven angles (0 degrees, 2.5 degrees, 5 degrees, 10 degrees, 15 degrees, 20 degrees and 30 degrees), using a time-of-flight (TOF) method employing organic scintillators NE213 at the Research Center for Nuclear Physics (RCNP) of Osaka University. The energy spectra of the source neutrons were precisely deduced down to 2 MeV at 0 degrees and 10 MeV at other angles. The cross-sections of the peak neutron production reaction at 0 degrees were on the 35-40 mb line of other experimental data, and the peak neutron angular distribution agreed well with the Taddeucci formula. Neutron energy spectra below 100 MeV at all angles were comparable, but the shapes of the continuum above 150 MeV changed considerably with the angle. In order to consider the correction required to derive the response in the peak region from the measured total response for high-energy neutron monitors such as DAR...
A Laplace transform method for energy multigroup hybrid discrete ordinates
International Nuclear Information System (INIS)
Segatto, C.F.; Vilhena, M.T.; Barros, R.C.
2010-01-01
In typical lattice cells where a highly absorbing, small fuel element is embedded in the moderator, a large weakly absorbing medium, high-order transport methods become unnecessary. In this work we describe a hybrid discrete ordinates (S N) method for energy multigroup slab lattice calculations. This hybrid S N method combines the convenience of a low-order S N method in the moderator with a high-order S N method in the fuel. The idea is based on the fact that in weakly absorbing media whose physical size is several neutron mean free paths in extent, even the S 2 method (P 1 approximation), leads to an accurate result. We use special fuel-moderator interface conditions and the Laplace transform (LTS N ) analytical numerical method to calculate the two-energy group neutron flux distributions and the thermal disadvantage factor. We present numerical results for a range of typical model problems.
International Nuclear Information System (INIS)
Greene, N.M.; Arwood, J.W.; Wright, R.Q.; Parks, C.V.
1994-08-01
The 238-group LAW Library is a new multigroup neutron cross-section library based on ENDF/B-V data, with five sets of data taken from ENDF/B-VI ( 14 N 7 , 15 N 7 , 16 O 8 , 154Eu 63 , and 155 Eu 63 ). These five nuclides are included because the new evaluations are thought to be superior to those in Version 5. The LAW Library contains data for over 300 materials and will be distributed by the Radiation Shielding Information Center, located at Oak Ridge National Laboratory. It was generated for use in neutronics calculations required in radioactive waste analyses, although it has equal utility in any study requiring multigroup neutron cross sections
Deconvolution of charged particle spectra from neutron depth profiling using Simplex method
Czech Academy of Sciences Publication Activity Database
Hnatowicz, Vladimír; Vacík, Jiří; Fink, Dietmar
2010-01-01
Roč. 81, č. 7 (2010), 073906/1-073906/7 ISSN 0034-6748 R&D Projects: GA MŠk(CZ) LC06041 Institutional research plan: CEZ:AV0Z10480505 Keywords : neutron depth profiling * Simplex method * NDP Subject RIV: BG - Nuclear , Atomic and Molecular Physics, Colliders Impact factor: 1.598, year: 2010
International Nuclear Information System (INIS)
Cornelius, I.M.; Rosenfeld, A.B.
2003-01-01
Microdosimetry is used to predict the biological effects of the densely ionizing radiation environments of hadron therapy and space. The creation of a solid state microdosimeter to replace the conventional Tissue Equivalent Proportional Counter (TEPC) is a topic of ongoing research. The Centre for Medical Radiation Physics has been investigating a technique using microscopic arrays of reverse biased PN junctions. A prototype silicon-on-insulator (SOI) microdosimeter was developed and preliminary measurements have been conducted at several hadron therapy facilities. Several factors impede the application of silicon microdosimeters to hadron therapy. One of the major limitations is that of tissue equivalence, ideally the silicon microdosimeter should provide a microdosimetry distribution identical to that of a microscopic volume of tissue. For microdosimetry in neutron fields, such as Fast Neutron Therapy, it is important that products resulting from neutron interactions in the non tissue equivalent sensitive volume do not contribute significantly to the spectrum. Experimental measurements have been conducted at the Gershenson Radiation Oncology Center, Harper Hospital, Detroit by Bradley et al. The aim was to provide a comparison with measurements performed with a TEPC under identical experimental conditions. Monte Carlo based calculations of these measurements were made using the GEANT4 Monte Carlo toolkit. Agreement between experimental and theoretical results was observed. The model illustrated the importance of neutron interactions in the non tissue equivalent sensitive volume and showed this effect to decrease with sensitive volume size as expected. Simulations were also performed for 1 micron cubic silicon sensitive volumes embedded in tissue equivalent material to predict the best case scenario for silicon microdosimetry in Fast Neutron Therapy
International Nuclear Information System (INIS)
Mewissen, D.J.; Rust, J.H.
1976-01-01
A total of 7109 C 57 Black mice of either sex were either sham-, neutron- or cobalt-irradiated at the age of 33+-3 days. The dose range extended from 3.2 to 47.2 rads for neutrons and from 18 to 141 rads for γ rays. This experiment was aimed at assessing relative biological effectiveness (RBE) and its possible dose dependence from radiation mortality and morbidity data, using actuarial statistics. The primary goal was to define the spontaneous or basic tumour spectrum in control animals of either sex, which included a major proportion of lymphocytic lymphomas, followed by reticulum cell lymphomas. A variety of other tumours were observed, among them various adenocarcinomas, squamous cell carcinomas and leiomyosarcomas of the gastrointestinal tract, liver and spleen hemangiomas, micro- and macrofollicular hyperplasia as well as papillary adenomas of the thyroid, fibromas and fibrosarcomas of connective tissue, muscles and bones, myomas and fibrosarcomas of uterus, luteomas and cysts of the ovary, papillary and transitional cell carcinomas of kidneys and an occasional mammary adenocarcinoma or skin epithelioma. Modulation of the basic tumour pattern by neutrons or cobalt was primarily operative on the reticular tissue. Age-specific incidence rates for combined mature and immature lymphocytic lymphomas decreased following neutron or cobalt irradiation at higher dose levels. In reticulum cell sarcomas, however, the tumour type evidently shifted almost entirely from the mature to the immature type. Furthermore, all rates increased markedly following irradiation at all dose levels. One major finding in all groups was the non-linearity of tumour response. Furthermore, it appeared that the control as well as the radiation-modulated tumour spectra were likely to proceed from intercompetitive stochastic processes rather than from some probabilistic random distribution. Some implications of these primary results are discussed
International Nuclear Information System (INIS)
Kaplan, A.; Bueyuekuslu, H.; Tel, E.; Aydin, A.; Boeluekdemir, M.H.
2011-01-01
In this study, neutron-emission spectra produced by (n, xn) reactions up to 26 MeV for some deformed target nuclei as 165 Ho, 181 Ta, 184 W, 232 Th and 238 U have been investigated. Also, the mean free path parameter's effect for 9n, xn) neutron-emission spectra has been examined. In the calculations, pre-equilibrium neutron-emission spectra have been calculated by using new evaluated hybrid model and geometry dependent hybrid model, full exciton model and cascade exciton model. The reaction equilibrium component has been calculated by Weisskopf-Ewing model. The obtained results have been discussed and compared with the available experimental data and found agreement with each other. (author)
Energy Technology Data Exchange (ETDEWEB)
Parker, K [Atomic Weapons Research Establishment, Aldermaston (United Kingdom)
1962-03-15
The AWRE punched-card library of neutron cross-sections is described together with associated IBM-7090 programmes which process this data to give group-averaged cross-sections for use in Monte Carlo, Carlson S{sub n} and other multi-group neutronics calculations. The methods developed to deal with both isotropic and anisotropic elastic scattering are described. These include the multi-group transport approximation and the full treatment of anisotropic scattering using the Legendre polynomial moments of the scattering transfer matrix. The principles of group-constant formation are considered and illustrated by describing systems of group constants suitable for fast-reactor calculations. Practical problems such as the empirical adjustment of group constants to reproduce integral results and the collapsing of a many-group set of constants to give a few-group set are discussed. (author) [French] L'auteur decrit le fichier de cartes perforees sur lesquelles on enregistre a l'Atomic Weapons Research Establishment (AWRE) les sections efficaces neutroniques ainsi que les programmes IBM-7090 associes qui sont employes pour le traitement de ces informations, en vue d'obtenir des sections efficaces moyennes par groupe pouvant servir aux calculs de neutroniques a plusieurs groupes, effectues a l'aide des methodes de Monte-Carlo, S{sub n} de Carlson et autres methodes. L'auteur expose ensuite les methodes mises au point roda etudier la diffusion elastique, tant isotrope qu'anisotrope. Elles comprennent l'approximation de transport a plusieurs groupes, ainsi que le traitement complet de la diffusion anisotrope par les moments polynomiaux de Legendre de la matrice de transfert de la diffusion. L'auteur examine les principes de la formation des constantes de groupes; a titre d'illustration, il decrit les systemes de constantes de groupes qui se pretent aux calculs de reacteurs a neutrons rapides. Il expose quelques problemes pratiques, tels que l'ajustement empirique des
Study of neutron spectra in extended uranium target. New experimental data
Directory of Open Access Journals (Sweden)
Paraipan M.
2017-01-01
Full Text Available The spatial distribution of neutron fluences in the extended uranium target (“Quinta” assembly irradiated with 0.66 GeV proton, 4 AGeV deuteron and carbon beams was studied using the reactions with different threshold energy (Eth. The data sets were obtained with 59Co samples. The accumulation rates for the following isotopes: 60Co (Eth 0 MeV, 59Fe (Eth 3 MeV, 58Co (Eth 10 MeV, 57Co (Eth 20 MeV, 56Co (Eth 32 MeV, 47Sc (Eth 55 MeV, and 48V (Eth 70 MeV were measured with HPGe spectrometer. The experimental accumulation rates were compared with the predictions of the simulations with Geant4 code. Substantial difference between the reconstructed and the simulated data for the hard part of the neutron spectrum was analyzed.
Formation properties from high resolution neutron activation gamma-ray spectra
International Nuclear Information System (INIS)
Mellor, D.W.; Underwood, M.C.
1985-01-01
A neutron activation logging tool has been developed comprising a Five Curie /sup 241/ Am-Be neutron source and a large n-type hyper-pure germanium gamma-ray detector. The tool maintains a constant temperature cryogenic environment for periods in excess of twenty hours. No liquid nitrogen or other consumable material is used in the operating or recharging stages. A large calibration tank in simulated well-bore geometry has been constructed with sand bodies saturated with oil and low salinity water (14,000 ppm NaCl). In the water zone prompt neutron capture gamma-rays from silicon, hydrogen and chlorine were prominent; gamma-rays from inelastic scattering on oxygen and silicon were detected. No gamma-rays arising from inelastic scattering on carbon were detected. These data have been interpreted to yield the porosity, fluid saturations, salinity and matrix composition. In the oil zone, gamma-rays arising from inelastic scattering on oxygen, silicon and carbon were detected. The intensity of the carbon line was very poor, and inadequate for quantitative purposes
International Nuclear Information System (INIS)
Košťál, Michal; Veškrna, Martin; Cvachovec, František; Jánský, Bohumil; Novák, Evžen; Rypar, Vojtěch; Milčák, Ján; Losa, Evžen; Mravec, Filip; Matěj, Zdeněk; Rejchrt, Jiří; Forget, Benoit; Harper, Sterling
2015-01-01
Highlights: • Neutron spectra measured in graphite and LiF + NaF. • Comparison of calculated and measured neutron spectra. • Effect of 19F on variation between various library calculated spectra. - Abstract: The present paper aims to compare the calculated and measured spectra after insertion of candidate materials for the Molten salt reactor/Fluoride cooled high temperature reactor system concept into the LR-0 reactor. The calculation is realized with MCNP6 code using ENDF/B-VII.0, JEFF-3.1, JENDL-3.3, JENDL-4, ROSFOND-2010 and CENDL-3.1 nuclear data libraries. Additionally, comparisons between the slowing down power of each media were performed. The slowing down properties are important parameters affecting the thickness of moderator media in a reactor
Zbiri, Mohamed; Viennois, Romain
2017-10-01
We report inelastic neutron scattering measurements of phonon spectra in the parent superconductor iron-tuned chalcogenide F e1 +xTe for two different x contents (x ≤0.11 ) using neutron time-of-flight technique. Thermal neutron spectroscopy allowed the collection of the low-temperature Stokes spectra over an extended Q range at 2, 40, and 120 K, hence covering both the magnetic monoclinic and the paramagnetic tetragonal phases, whereas cold neutrons allowed the measurement of high-resolution anti-Stokes spectra at 140, 220, and 300 K, thus covering the tetragonal phase. Our results evidence a spin-phonon coupling behavior towards the observed noticeable temperature-dependent change of the Stokes spectra across the transition temperatures. On the other hand, the anti-Stokes spectra reveal a pronounced hardening of the low-energy, acoustic region of the phonon spectrum upon heating, indicating a strong anharmonicity and a subtle dependence of phonons on structural evolution within the tetragonal phase. Experimental results are accompanied by ab initio calculations of phonon spectra of the tetragonal stoichiometric phase for a comparison with the high-resolution anti-Stokes spectra. Calculations included different density functional methods. Spin polarization and van der Waals interaction were either considered or neglected, individually or concomitantly, in order to study their respective effect on lattice dynamics description. Our results suggest that including van der Waals interaction has only a slight effect on phonon dynamics; however, phonon spectra are better described when spin polarization is included in a cooperative way with van der Waals interactions.
The thick-target 9Be(d,n) neutron spectra for deuteron energies between 2.6 and 7.0-MeV
International Nuclear Information System (INIS)
Meadows, J.W.
1991-11-01
The measurement of the zero deg. neutron spectra and yields from deuterons incident on thick beryllium metal targets is described. 235 U and 238 U fission ion chambers were used as neutron detectors to span the neutron energy range above 0.05-MeV with a time resolution of ≤ 3 nanosec. Measurements were made for incident deuteron energies from 2.6 to 7.0-MeV, at 0.4-MeV intervals, using time-of-flight techniques with flight paths of 2.7 and 6.8 meters. The results are presented in graphical form and in tables
Theoretical Time Dependent Thermal Neutron Spectra and Reaction Rates in H2O and D2O
International Nuclear Information System (INIS)
Purohit, S.N.
1966-04-01
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 2 O and D 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 2 O and D 2 O. The bound models of Nelkin for H 2 O and of Butler for D 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 2 O than of the Nelkin model with H 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 2 O and D 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 group structure and the scattering
NUMERICAL MULTIGROUP TRANSIENT ANALYSIS OF SLAB NUCLEAR REACTOR WITH THERMAL FEEDBACK
Directory of Open Access Journals (Sweden)
Filip Osuský
2016-12-01
Full Text Available The paper describes a new numerical code for multigroup transient analyses with thermal feedback. The code is developed at Institute of Nuclear and Physical Engineering. It is necessary to carefully investigate transient states of fast neutron reactors, due to recriticality issues after accident scenarios. The code solves numerical diffusion equation for 1D problem with possible neutron source incorporation. Crank-Nicholson numerical method is used for the transient states. The investigated cases are describing behavior of PWR fuel assembly inside of spent fuel pool and with the incorporated neutron source for better illustration of thermal feedback.
Casoli, P.; Authier, N.; Jacquet, X.; Cartier, J.
2014-04-01
Caliban and Prospero are two highly enriched uranium metallic core reactors operated on the CEA Center of Valduc. These critical assemblies are suitable for integral experiments, such as fission yields measurements or perturbation measurements, which have been carried out recently on the Caliban reactor. Different unfolding methods, based on activation foils and fission chambers measurements, are used to characterize the reactor spectra and especially the Caliban spectrum, which is very close to a pure fission spectrum.
An ''exact'' treatment of self-shielding and covers in neutron spectra determinations
International Nuclear Information System (INIS)
Griffin, P.J.; Kelly, J.G.
1995-01-01
Most neutron spectrum determination methodologies ignore self-shielding effects in dosimetry foils and treat covers with an exponential attenuation model. This work provides a quantitative analysis of the approximations in this approach. It also provides a methodology for improving the fidelity of the treatment of the dosimetry sensor response to a level consistent with the user's spectrum characterization approach. A library of correction functions for the energy-dependent sensor response has been compiled that addresses dosimetry foils/configurations in use at the Sandia National Laboratories Radiation Metrology Laboratory
Kondo resonance in the neutron spectra of intermediate-valent YbAl3
International Nuclear Information System (INIS)
Walter, U.; Holland-Moritz, E.; Fisk, Z.
1991-01-01
We have measured the dynamic susceptibility of intermediate-valent YbAl 3 by means of cold-neutron scattering. We find two intense magnetic excitations below 40 meV. One of these, with location around 18 meV at helium temperatures, shifts steadily toward 0 meV with increasing temperatures. While crystal field interactions are unable to account for such a behavior, this excitation is in good agreement with a transition from the f ground state to a Kondo resonance as described by the Anderson model. In particular, it definitely excludes a gaplike magnetic response with gap width Δ=30 meV as asserted earlier
International Nuclear Information System (INIS)
Vaidyanathan, R.; Bourke, M.A.; Dunand, D.C.
1999-01-01
Neutron diffraction spectra were obtained during various stages of a reversible stress-induced austenite to martensite phase transformation in superelastic NiTi. This was accomplished by neutron diffraction measurements on bulk polycrystalline NiTi samples simultaneously subjected to mechanical loading. Analysis of the data was carried out using individual lattice plane (hkl) reflections as well as by Rietveld refinement. In the Rietveld procedure, strains in austenite were described in terms of an isotropic (hkl independent) and an anisotropic (hkl dependent) component. At higher stresses, austenite lattice plane reflections exhibited nonlinear and dissimilar elastic responses which may be attributed to the transformation. The texture evolution is significant in both austenite and martensite phases during the transformation and two approaches were used to describe this evolving texture, i.e., an ellipsoidal model due to March - Dollase and a generalized spherical-harmonic approach. The respective predictions of the phase fraction evolution as a function of applied stress were compared. A methodology is thus established to quantify the discrete phase strains, phase volume fractions, and texture during such transformations. copyright 1999 American Institute of Physics
Measurements of the neutron energy spectra in the core of IPEN/MB-01 reactor
International Nuclear Information System (INIS)
Martins, Fernando Prat Goncalves
2006-01-01
This work presents the neutron spectrum measurements in the Reactor IPEN/MB-01 using very thin activation detectors in the metallic form, in reactor core, in moderator region. An articulated device allows that the foils are inserted in the central position of reactor core, ensuring that all the foils are irradiated in the same position. The activation detectors of different materials such Au 197 , Mg 24 , Ti 4 '8, In 115 , Sc 45 and others, were selected to cover a large range of neutron spectrum. After the irradiation, the activation detectors were submitted to a spectrometry gamma by using a system of counting with high purity Germanium, to obtain the saturation activity per target nuclide. The saturation activity is one of the main data of input of unfolding code SANDBP, that through an iterative adjustment, modify the spectrum that better agree with the dataset of code input, composition mainly for measure reaction rate per target nuclide and a initial input spectrum, calculated for Hammer-Technion code, supplying a solution spectrum. (author)
Holmes, Jesse Curtis
Nuclear data libraries provide fundamental reaction information required by nuclear system simulation codes. The inclusion of data covariances in these libraries allows the user to assess uncertainties in system response parameters as a function of uncertainties in the nuclear data. Formats and procedures are currently established for representing covariances for various types of reaction data in ENDF libraries. This covariance data is typically generated utilizing experimental measurements and empirical models, consistent with the method of parent data production. However, ENDF File 7 thermal neutron scattering library data is, by convention, produced theoretically through fundamental scattering physics model calculations. Currently, there is no published covariance data for ENDF File 7 thermal libraries. Furthermore, no accepted methodology exists for quantifying or representing uncertainty information associated with this thermal library data. The quality of thermal neutron inelastic scattering cross section data can be of high importance in reactor analysis and criticality safety applications. These cross sections depend on the material's structure and dynamics. The double-differential scattering law, S(alpha, beta), tabulated in ENDF File 7 libraries contains this information. For crystalline solids, S(alpha, beta) is primarily a function of the material's phonon density of states (DOS). Published ENDF File 7 libraries are commonly produced by calculation and processing codes, such as the LEAPR module of NJOY, which utilize the phonon DOS as the fundamental input for inelastic scattering calculations to directly output an S(alpha, beta) matrix. To determine covariances for the S(alpha, beta) data generated by this process, information about uncertainties in the DOS is required. The phonon DOS may be viewed as a probability density function of atomic vibrational energy states that exist in a material. Probable variation in the shape of this spectrum may be
International Nuclear Information System (INIS)
Titarenko, Yu.E.; Batyaev, V.F.; Borovlev, S.P.; Gladkikh, N.G.; Igumnov, M.M.; Legostaev, V.O.; Karpikhin, E.I.; Konev, V.N.; Kushnerev, Yu.T.; Ryazhsky, V.I.; Spiridonov, V.G.; Chernyavsky, E.V.; Shvedov, O.V.
2009-10-01
The main goal of the Project is to study and evaluate nuclear characteristics of materials and isotopes involved in processes of irradiated nuclear fuel transmutation. This principal task is subdivided into 9 subtasks subject to the neutron or proton source used, the type of the nuclear process under study, isotope collection, characteristics of which are to be investigated, etc. In the presented extract of the Project Activity report the measurements there were used the MAKET zero-power heavy-water reactor in the measurements there was employed a large set of minor actinide samples highly enriched with the main isotope. The samples were obtained with mass-separator SM-2 (VNIIEF). At the heavy-water reactor MAKET (ITEP) there were measured multiplying and kinetic characteristics of salt mixtures basing on the spectra of fast and thermal neutrons. The salt mixtures of zirconium and sodium fluorides were available in salt blanket models (SBM) of cylindrical shape. There were measured the neutron spectra formed by this micro-model as well as the effective fission cross-sections of neptunium, plutonium, americium and curium isotopes caused by SBM neutrons. The neutron spectra in the measurement positions were determined from activation reaction rates. (author)
International Nuclear Information System (INIS)
Tassan, S.
1978-01-01
A selection of technical documents is given concerning the experimental determination of the neutron capture cross-sections of fast reactor structural materials (Fe, Cr, Ni...) integrated over the intermediate energy spectra. The experimental structure project and modifications of the reactor RB2 for this experiment, together with criticality and safety calculations, are presented
On unfolding counting-rate spectra of recoil-proton neutron detectors
International Nuclear Information System (INIS)
Yeivin, Yehuda
1983-01-01
This note proposes a possible scheme for unfolding recoil-proton neutron detector data, in which at first the undistorted proton source spectrum is derived. The main argument in favour of this scheme is that, compared with the conventional scheme, it necessitates somewhat weaker assumptions with respect to the unknown spectrum above the detector's upper energy cutoff, and would therefore be more reliable. We also demonstrate a simple, elementary proof of the wall effect correction for spherical detectors, and, in order to gain insight of the potential merits of the proposed unfolding scheme, illustrate our main argument by considering a hypothetic linear range-energy relation, in which case complete unfolding becomes possible with no assumptions at all on the proton spectrum above the cutoff energy. (author)
International Nuclear Information System (INIS)
Ondov, J.M.; Divita, F. Jr.
1993-01-01
Size-fractionated aerosol samples collected with micro-orifice impactors at Camden, NJ, a heavily industrialized urban area, and at two sites near Washington, DC, were analyzed for elemental constituents determined instrumentally from short-lived neutron activation products. A least-squares peak-fitting method was used with impactor calibration data to determine log-normal distribution parameters, i.e., mass median aerodynamic diameter (MMAD) and geometric standard deviation (σ g ) for particles bearing S, V, Br, and I. For these elements, MMADs ranged from 0.24 to 0.65 μm; 0.23 to 0.53 μm; 0.22 to 0.61 μm, and 0.20 to 0.48 μm, respectively. (author) 15 refs.; 4 figs.; 2 tabs
Cassandre : a two-dimensional multigroup diffusion code for reactor transient analysis
International Nuclear Information System (INIS)
Arien, B.; Daniels, J.
1986-12-01
CASSANDRE is a two-dimensional (x-y or r-z) finite element neutronics code with thermohydraulics feedback for reactor dynamics prior to the disassembly phase. It uses the multigroup neutron diffusion theory. Its main characteristics are the use of a generalized quasistatic model, the use of a flexible multigroup point-kinetics algorithm allowing for spectral matching and the use of a finite element description. The code was conceived in order to be coupled with any thermohydraulics module, although thermohydraulics feedback is only considered in r-z geometry. In steady state criticality search is possible either by control rod insertion or by homogeneous poisoning of the coolant. This report describes the main characterstics of the code structure and provides all the information needed to use the code. (Author)
International Nuclear Information System (INIS)
Ouisloumen, M.
1989-03-01
This research thesis reports an investigation of neutron diffusion by the fuel of a nuclear reactor while taking thermal agitation of diffusing nuclei into account. The author adopted the free gas model to describe the atom vibrations in the crystal network. He reports the elaboration of a diffusion law which gives the neutron energy spectrum after collision. Some particular theoretical cases are then studied in order to explain the observed physical phenomena, and to confirm the obtained results. The Monte Carlo method is also used to validate these results. The author presents the various physical criteria which must be met by an energetic grid in order to minimize errors in reaction rate calculations
International Nuclear Information System (INIS)
Nolthenius, H.J.; Zijp, W.L.
1981-11-01
Results are given of a study on the consistency between 'integral' and 'differential' cross sections data for four benchmark neutron spectra and 36 neutron reactions of importance for reactor neutron metrology. The energy dependent cross section data and their uncertainty data are obtained from the ENDF/B-V dosimetry file. The reactions have been considered with respect to the following quantities: 1. the precision of the averaged cross sections, for a specified spectrum; 2. the discrepancy between the measured and the calculated average cross section values; 3. the consistency between the measured and calculated average cross section values, described by the chi 2 -parameter. It was possible to take into account the available cross section covariance information present in the ENDF/B-V dosimetry file. Covariance information on the benchmark flux density spectra was not taken into account in this study
Verification and validation of multi-group library MUSE1.0 created from ENDF/B-VII.0
International Nuclear Information System (INIS)
Chen Yixue; Wu Jun; Yang Shouhai; Zhang Bin; Lu Daogang; Chen Chaobin
2010-01-01
A multi-group library set named MUSE1.0 with 172-neutron group and 42-photon group is produced based on ENDF/B-VII.0 using NJOY code. Weight function of the multi-group library set is taken from the Vitanim-e library and the max legendre order of scattering matrix is six. All the nuclides have thermal scattering data created using free-gas scattering law and 10 Bondarenko background cross sections se lected to generate the self-shielded multi-group cross sections. The final libraries have GENDF-format, MATXS-format and ACE-multi-group sub-libraries and each sub-library generated under 4 temperatures(293 K,600 K,800 K and 900 K). This paper provides a summary of the procedure to produce the library set and a detail description of the validation of the multi-group library set by several critical benchmark devices and shielding benchmark devices using MCNP code. The ability to handle the thermal neutron transport and resonance self-shielding problems are investigated specially. In the end, we draw the conclusion that the multi-group libraries produced is credible and can be used in the R and D process of Supercritical Water Reactor Design. (authors)
VSOP, Neutron Spectra, 2-D Flux Synthesis, Fuel Management, Thermohydraulics Calculation
International Nuclear Information System (INIS)
Teuchert, E.; Haas, K.A.
1995-01-01
1 - Description of problem or function: VSOP (Very Superior Old Programs) is a system of codes linked together for the simulation of reactor life histories. It comprises neutron cross section libraries and processing routines, repeated neutron spectrum evaluation, 2-D and 3-D diffusion calculation, depletion and shut-down features, in- core and out-of-pile fuel management, fuel cycle cost analysis, and thermal hydraulics (steady state and transient). Various techniques have been employed to accelerate the iterative processes and to optimize the internal data transfer. The code system has been used extensively for comparison studies of thermal reactors, their fuel cycles, thermal transients, and safety assessment. Besides its use in research and development work for the Gas Cooled High Temperature Reactor, the system has been applied successfully to Light Water and Heavy Water Reactors, MAGNOX, and RBMK. 2 - Method of solution: The nuclear data for 184 isotopes are contained in two libraries. Fast and epithermal data in a 68 group GAM-I structure have been prepared mainly from ENDF/B-V and JEF-1. Resonance cross section data are given as input. Thermal data in a 30 group THERMOS structure have been collapsed from a 96 group THERMALIZATION (GATHER) library by a relevant neutron energy spectrum generated by the THERMALIZATION code. Graphite scattering matrices are based on the Young phonon spectrum in graphite. The neutron spectrum is calculated by a combination of the GAM and THERMOS codes. They can simultaneously be employed for many core regions differing in temperature, burnup, and fuel element lay-out. The thermal cell code THERMOS has been extended to treat the grain structure of the coated particles inside the fuel elements, and the epithermal GAM code uses modified cross sections for the resonance absorbers prepared from double heterogeneous ZUT-DGL calculations. The diffusion module of the code is CITATION with 2 - 8 energy groups. It provides the neutron
A code system to generate multigroup cross-sections using basic data
International Nuclear Information System (INIS)
Garg, S.B.; Kumar, Ashok
1978-01-01
For the neutronic studies of nuclear reactors, multigroup cross-sections derived from the basic energy point data are needed. In order to carry out the design based studies, these cross-sections should also incorporate the temperature and fuel concentration effects. To meet these requirements, a code system comprising of RESRES, UNRES, FIGERO, INSCAT, FUNMO, AVER1 and BGPONE codes has been adopted. The function of each of these codes is discussed. (author)
International Nuclear Information System (INIS)
Takeshi, Y.; Keisuke, K.
1983-01-01
The multigroup neutron diffusion equation for two-dimensional triangular geometry is solved by the finite Fourier transformation method. Using the zero-th-order equation of the integral equation derived by this method, simple algebraic expressions for the flux are derived and solved by the alternating direction implicit method. In sample calculations for a benchmark problem of a fast breeder reactor, it is shown that the present method gives good results with fewer mesh points than the usual finite difference method
Survey of computer codes which produce multigroup data from ENDF/B-IV
International Nuclear Information System (INIS)
Greene, N.M.
1975-01-01
The features of three code systems that produce multigroup neutron data are contrasted. This includes the ETOE-2/MC 2 -2/SDX, MINX/SPHINX and AMPX code packages. These systems all contain a fairly extensive set of processing capabilities with the current evaluated nuclear data files--ENDF/B. They were designed with different goals and applications in mind. This paper discusses some of their differences and the implications for particular situations
Energy Technology Data Exchange (ETDEWEB)
Gerhard Strydom; Cristian Rabiti; Andrea Alfonsi
2012-10-01
PHISICS is a neutronics code system currently under development at the Idaho National Laboratory (INL). Its goal is to provide state of the art simulation capability to reactor designers. The different modules for PHISICS currently under development are a nodal and semi-structured transport core solver (INSTANT), a depletion module (MRTAU) and a cross section interpolation (MIXER) module. The INSTANT module is the most developed of the mentioned above. Basic functionalities are ready to use, but the code is still in continuous development to extend its capabilities. This paper reports on the effort of coupling the nodal kinetics code package PHISICS (INSTANT/MRTAU/MIXER) to the thermal hydraulics system code RELAP5-3D, to enable full core and system modeling. This will enable the possibility to model coupled (thermal-hydraulics and neutronics) problems with more options for 3D neutron kinetics, compared to the existing diffusion theory neutron kinetics module in RELAP5-3D (NESTLE). In the second part of the paper, an overview of the OECD/NEA MHTGR-350 MW benchmark is given. This benchmark has been approved by the OECD, and is based on the General Atomics 350 MW Modular High Temperature Gas Reactor (MHTGR) design. The benchmark includes coupled neutronics thermal hydraulics exercises that require more capabilities than RELAP5-3D with NESTLE offers. Therefore, the MHTGR benchmark makes extensive use of the new PHISICS/RELAP5-3D coupling capabilities. The paper presents the preliminary results of the three steady state exercises specified in Phase I of the benchmark using PHISICS/RELAP5-3D.
Multigroup P8 - elastic scattering matrices of main reactor elements
International Nuclear Information System (INIS)
Garg, S.B.; Shukla, V.K.
1979-01-01
To study the effect of anisotropic scattering phenomenon on shielding and neutronics of nuclear reactors multigroup P8-elastic scattering matrices have been generated for H, D, He, 6 Li, 7 Li, 10 B, C, N, O, Na, Cr, Fe, Ni, 233 U, 235 U, 238 U, 239 Pu, 240 Pu, 241 Pu and 242 Pu using their angular distribution, Legendre coefficient and elastic scattering cross-section data from the basic ENDF/B library. Two computer codes HSCAT and TRANS have been developed to complete this task for BESM-6 and CDC-3600 computers. These scattering matrices can be directly used as input to the transport theory codes ANISN and DOT. (auth.)
Inherent protection of plutonium by doping minor actinide in thermal neutron spectra
International Nuclear Information System (INIS)
Peryoga, Yoga; Sagara, Hiroshi; Saito, Masaki; Ezoubtchenko, Alexey
2005-01-01
The present study focuses on the exploration of the effect of minor actinide (MA) addition into uranium oxide fuels of different enrichment (5% 235 U and 20% 235 U) as ways of increasing fraction of even-mass-number plutonium isotopes. Among plutonium isotopes, 238 Pu, 240 Pu and 242 Pu have the characteristics of relatively high decay heat and spontaneous fission neutron rate that can improve proliferation-resistant properties of a plutonium composition. Two doping options were proposed, i.e. doping of all MA elements (Np, Am and Cm) and doping of only Np to observe their effect on plutonium proliferation-resistant properties. Pressurized water reactor geometry has been chosen for fuels irradiation environment where irradiation has been extended beyond critical to explore the subcritical system potential. Results indicate that a large amount of MA doping within subcritical operation highly improves the proliferation-resistant properties of the plutonium with high total plutonium production. Doping of 1% MA or Np into 5% 235 U enriched uranium fuel appears possible for critical operation of the current commercial light water reactor with reasonable improvement in the plutonium proliferation-resistant properties. (author)
Energy Technology Data Exchange (ETDEWEB)
Calloo, A.; Vidal, J.F.; Le Tellier, R.; Rimpault, G., E-mail: ansar.calloo@cea.fr, E-mail: jean-francois.vidal@cea.fr, E-mail: romain.le-tellier@cea.fr, E-mail: gerald.rimpault@cea.fr [CEA, DEN, DER/SPRC/LEPh, Saint-Paul-lez-Durance (France)
2011-07-01
This paper deals with the solving of the multigroup integro-differential form of the transport equation for fine energy group structure. In that case, multigroup transfer cross sections display strongly peaked shape for light scatterers and the current Legendre polynomial expansion is not well-suited to represent them. Furthermore, even if considering an exact scattering cross sections representation, the scattering source in the discrete ordinates method (also known as the Sn method) being calculated by sampling the angular flux at given directions, may be wrongly computed due to lack of angular support for the angular flux. Hence, following the work of Gerts and Matthews, an angular finite volume solver has been developed for 2D Cartesian geometries. It integrates the multigroup transport equation over discrete volume elements obtained by meshing the unit sphere with a product grid over the polar and azimuthal coordinates and by considering the integrated flux per solid angle element. The convergence of this method has been compared to the S{sub n} method for a highly anisotropic benchmark. Besides, piecewise-average scattering cross sections have been produced for non-bound Hydrogen atoms using a free gas model for thermal neutrons. LWR lattice calculations comparing Legendre representations of the Hydrogen scattering multigroup cross section at various orders and piecewise-average cross sections for this same atom are carried out (while keeping a Legendre representation for all other isotopes). (author)
International Nuclear Information System (INIS)
Calloo, A.; Vidal, J.F.; Le Tellier, R.; Rimpault, G.
2011-01-01
This paper deals with the solving of the multigroup integro-differential form of the transport equation for fine energy group structure. In that case, multigroup transfer cross sections display strongly peaked shape for light scatterers and the current Legendre polynomial expansion is not well-suited to represent them. Furthermore, even if considering an exact scattering cross sections representation, the scattering source in the discrete ordinates method (also known as the Sn method) being calculated by sampling the angular flux at given directions, may be wrongly computed due to lack of angular support for the angular flux. Hence, following the work of Gerts and Matthews, an angular finite volume solver has been developed for 2D Cartesian geometries. It integrates the multigroup transport equation over discrete volume elements obtained by meshing the unit sphere with a product grid over the polar and azimuthal coordinates and by considering the integrated flux per solid angle element. The convergence of this method has been compared to the S_n method for a highly anisotropic benchmark. Besides, piecewise-average scattering cross sections have been produced for non-bound Hydrogen atoms using a free gas model for thermal neutrons. LWR lattice calculations comparing Legendre representations of the Hydrogen scattering multigroup cross section at various orders and piecewise-average cross sections for this same atom are carried out (while keeping a Legendre representation for all other isotopes). (author)
Energy Technology Data Exchange (ETDEWEB)
Chiang, Min-Han; Wang, Jui-Yu [Institute of Nuclear Engineering and Science, National Tsing Hua University, 101, Section 2, Kung-Fu Road, Hsinchu 30013, Taiwan (China); Sheu, Rong-Jiun, E-mail: rjsheu@mx.nthu.edu.tw [Institute of Nuclear Engineering and Science, National Tsing Hua University, 101, Section 2, Kung-Fu Road, Hsinchu 30013, Taiwan (China); Department of Engineering System and Science, National Tsing Hua University, 101, Section 2, Kung-Fu Road, Hsinchu 30013, Taiwan (China); Liu, Yen-Wan Hsueh [Institute of Nuclear Engineering and Science, National Tsing Hua University, 101, Section 2, Kung-Fu Road, Hsinchu 30013, Taiwan (China); Department of Engineering System and Science, National Tsing Hua University, 101, Section 2, Kung-Fu Road, Hsinchu 30013, Taiwan (China)
2014-05-01
The High Temperature Engineering Test Reactor (HTTR) in Japan is a helium-cooled graphite-moderated reactor designed and operated for the future development of high-temperature gas-cooled reactors. Two detailed full-core models of HTTR have been established by using SCALE6 and MCNP5/X, respectively, to study its neutronic properties. Several benchmark problems were repeated first to validate the calculation models. Careful code-to-code comparisons were made to ensure that two calculation models are both correct and equivalent. Compared with experimental data, the two models show a consistent bias of approximately 20–30 mk overestimation in effective multiplication factor for a wide range of core states. Most of the bias could be related to the ENDF/B-VII.0 cross-section library or incomplete modeling of impurities in graphite. After that, a series of systematic analyses was performed to investigate the effects of cross sections on the HTTR criticality and burnup calculations, with special interest in the comparison between continuous-energy and multigroup results. Multigroup calculations in this study were carried out in 238-group structure and adopted the SCALE double-heterogeneity treatment for resonance self-shielding. The results show that multigroup calculations tend to underestimate the system eigenvalue by a constant amount of ∼5 mk compared to their continuous-energy counterparts. Further sensitivity studies suggest the differences between multigroup and continuous-energy results appear to be temperature independent and also insensitive to burnup effects.
International Nuclear Information System (INIS)
Chiang, Min-Han; Wang, Jui-Yu; Sheu, Rong-Jiun; Liu, Yen-Wan Hsueh
2014-01-01
The High Temperature Engineering Test Reactor (HTTR) in Japan is a helium-cooled graphite-moderated reactor designed and operated for the future development of high-temperature gas-cooled reactors. Two detailed full-core models of HTTR have been established by using SCALE6 and MCNP5/X, respectively, to study its neutronic properties. Several benchmark problems were repeated first to validate the calculation models. Careful code-to-code comparisons were made to ensure that two calculation models are both correct and equivalent. Compared with experimental data, the two models show a consistent bias of approximately 20–30 mk overestimation in effective multiplication factor for a wide range of core states. Most of the bias could be related to the ENDF/B-VII.0 cross-section library or incomplete modeling of impurities in graphite. After that, a series of systematic analyses was performed to investigate the effects of cross sections on the HTTR criticality and burnup calculations, with special interest in the comparison between continuous-energy and multigroup results. Multigroup calculations in this study were carried out in 238-group structure and adopted the SCALE double-heterogeneity treatment for resonance self-shielding. The results show that multigroup calculations tend to underestimate the system eigenvalue by a constant amount of ∼5 mk compared to their continuous-energy counterparts. Further sensitivity studies suggest the differences between multigroup and continuous-energy results appear to be temperature independent and also insensitive to burnup effects
WIMSD5, Deterministic Multigroup Reactor Lattice Calculations
International Nuclear Information System (INIS)
2004-01-01
1 - Description of program or function: The Winfrith improved multigroup scheme (WIMS) is a general code for reactor lattice cell calculation on a wide range of reactor systems. In particular, the code will accept rod or plate fuel geometries in either regular arrays or in clusters and the energy group structure has been chosen primarily for thermal calculations. The basic library has been compiled with 14 fast groups, 13 resonance groups and 42 thermal groups, but the user is offered the choice of accurate solutions in many groups or rapid calculations in few groups. Temperature dependent thermal scattering matrices for a variety of scattering laws are included in the library for the principal moderators which include hydrogen, deuterium, graphite, beryllium and oxygen. WIMSD5 is a successor version of WIMS-D/4. 2 - Method of solution: The treatment of resonances is based on the use of equivalence theorems with a library of accurately evaluated resonance integrals for equivalent homogeneous systems at a variety of temperatures. The collision theory procedure gives accurate spectrum computations in the 69 groups of the library for the principal regions of the lattice using a simplified geometric representation of complicated lattice cells. The computed spectra are then used for the condensation of cross-sections to the number of groups selected for solution of the transport equation in detailed geometry. Solution of the transport equation is provided either by use of the Carlson DSN method or by collision probability methods. Leakage calculations including an allowance for streaming asymmetries may be made using either diffusion theory or the more elaborate B1-method. The output of the code provides Eigenvalues for the cases where a simple buckling mode is applicable or cell-averaged parameters for use in overall reactor calculations. Various reaction rate edits are provided for direct comparison with experimental measurements. 3 - Restrictions on the complexity of
Energy Technology Data Exchange (ETDEWEB)
Nicholl, M.; Berger, E.; Kasen, D.; Metzger, B. D.; Elias, J.; Briceño, C.; Alexander, K. D.; Blanchard, P. K.; Chornock, R.; Cowperthwaite, P. S.; Eftekhari, T.; Fong, W.; Margutti, R.; Villar, V. A.; Williams, P. K. G.; Brown, W.; Annis, J.; Bahramian, A.; Brout, D.; Brown, D. A.; Chen, H. -Y.; Clemens, J. C.; Dennihy, E.; Dunlap, B.; Holz, D. E.; Marchesini, E.; Massaro, F.; Moskowitz, N.; Pelisoli, I.; Rest, A.; Ricci, F.; Sako, M.; Soares-Santos, M.; Strader, J.
2017-10-16
We present optical and ultraviolet spectra of the first electromagnetic counterpart to a gravitational wave (GW) source, the binary neutron star merger GW170817. Spectra were obtained nightly between 1.5 and 9.5 days post-merger, using the SOAR and Magellan telescopes; the UV spectrum was obtained with the \\textit{Hubble Space Telescope} at 5.5 days. Our data reveal a rapidly-fading blue component ($T\\approx5500$ K at 1.5 days) that quickly reddens; spectra later than $\\gtrsim 4.5$ days peak beyond the optical regime. The spectra are mostly featureless, although we identify a possible weak emission line at $\\sim 7900$ \\AA\\ at $t\\lesssim 4.5$ days. The colours, rapid evolution and featureless spectrum are consistent with a "blue" kilonova from polar ejecta comprised mainly of light $r$-process nuclei with atomic mass number $A\\lesssim 140$. This indicates a sight-line within $\\theta_{\\rm obs}\\lesssim 45^{\\circ}$ of the orbital axis. Comparison to models suggests $\\sim0.03$ M$_\\odot$ of blue ejecta, with a velocity of $\\sim 0.3c$. The required lanthanide fraction is $\\sim 10^{-4}$, but this drops to $<10^{-5}$ in the outermost ejecta. The large velocities point to a dynamical origin, rather than a disk wind, for this blue component, suggesting that both binary constituents are neutron stars (as opposed to a binary consisting of a neutron star and a black hole). For dynamical ejecta, the high mass favors a small neutron star radius of $\\lesssim 12$ km. This mass also supports the idea that neutron star mergers are a major contributor to $r$-process nucleosynthesis.
International Nuclear Information System (INIS)
Harker, Y.D.
1976-01-01
A semi-empirical analytical expression representing a fast reactor neutron spectrum has been developed. This expression was used in a non-linear regression computer routine to obtain from measured multiple foil integral reaction data the neutron spectrum inside the Coupled Fast Reactivity Measurement Facility. In this application six parameters in the analytical expression for neutron spectrum were adjusted in the non-linear fitting process to maximize consistency between calculated and measured integral reaction rates for a set of 15 dosimetry detector foils. In two-thirds of the observations the calculated integral agreed with its respective measured value to within the experimental standard deviation, and in all but one case agreement within two standard deviations was obtained. Based on this quality of fit the estimated 70 to 75 percent confidence intervals for the derived spectrum are 10 to 20 percent for the energy range 100 eV to 1 MeV, 10 to 50 percent for 1 MeV to 10 MeV and 50 to 90 percent for 10 MeV to 18 MeV. The analytical model has demonstrated a flexibility to describe salient features of neutron spectra of the fast reactor type. The use of regression analysis with this model has produced a stable method to derive neutron spectra from a limited amount of integral data
International Nuclear Information System (INIS)
Main, P.L.; Hughes, M.J.
1983-01-01
The system developed at the British Museum Research Laboratory for the examination of ancient ceramics by neutron activation analysis is described. The description covers the procedures followed for sample preparation, spectrum accumulation, and the subsequent analysis by computer to yield final concentrations of elements present in the samples. Spectra are accumulated using a 7000 series Ge(Li) detector attached to a Canberra model 8180 multi-channel analyser, and are transferred on-line to a Hewlett-Packard 1000 system computer running under the RTE IVB real-time operating system. Particular attention is given to the design of the computer programs, and how a series of smaller programs communicating via intermediate command files can overcome the problems of accommodating a large amount of program code on a minicomputer. This also results in great flexibility in how the processing is carried out. One of the programs described is an implementation of the peak-searching and fitting routines from the Naval Research Laboratory's program HYPERMET. (author)
International Nuclear Information System (INIS)
Nicoli, I.G.
1981-06-01
A radiochemical investigation is performed to measure the cumulative fission product yields of several lantanides and yttrium nuclides in the 238 U by fission neutron spectra. Natural and depleted uranium are irradiated under the same experimental conditions in order to find a way to subtract the contribution of the 235 U fission. 235 U percentage in the natural uranium was 3.5 times higher than in the depleted uranium. Uranium oxides samples are irradiated inside the core of the Argonaut Reactor, at the Instituto de Engenharia Nuclear, and the lantanides and yttrium are chemically separated. The fission products gamma activities were detected, counted and analysed in a system constituted by a high resolution Ge(Li) detector, 4096 multichannel analyser and a PDP-11 computer. Cumulative yields for fission products with half-lives between 1 to 33 hours are measured: 93 Y, 141 La, 142 La, 143 Ce and 149 Nd. The chain total yields are calculated. The cumulative fission yields measured for 93 Y, 141 La, 142 La, 143 Ce and 149 Nd are 4,49%, 4,54%, 4,95%, 4,16% and 1,37% respectively and they are in good agreement with the values found in the literature. (Author) [pt