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Sample records for avr pebble bed

  1. The importance of the AVR pebble-bed reactor for the future of nuclear power

    Energy Technology Data Exchange (ETDEWEB)

    Pohl, P. [Arbeitsgemeinschaft Versuchsreaktor AVR GmbH, Postfach 1160, 52412 Juelich (Germany)

    2006-07-01

    The AVR pebble-bed high temperature gas-cooled reactor (HTGR) at Juelich (Germany)) operated from 1967 to 1988 and was certainly the most important HTGR project of the past. The reactor was the mass test bed for all development steps of HTGR pebble fuel. Some early fuel charges failed under high temperature conditions and contaminated the reactor. An accurate pebble measurement (Cs 137) allowed to clean the core from unwanted pebbles after 1981. The coolant activity went down and remained very low for the remaining reactor operation. A melt-wire experiment in 1986 revealed max. coolant temperatures of >1280 deg. C and fuel temperatures of >1350 deg. C, explained by under-estimated bypasses. The fuel still in the core achieved high burn-ups and showed under the extreme temperature conditions excellent fission product retention. Thus, the AVR operation qualified the HTGR fuel, and an average discharge burn-up of 112% fifa revealed an excellent fuel economy of the pebble-bed reactor. Furthermore, the AVR operation offers many meaningful data for code-to-experiment comparisons. (authors)

  2. Fission Product Transport and Source Terms in HTRs: Experience from AVR Pebble Bed Reactor

    Directory of Open Access Journals (Sweden)

    Rainer Moormann

    2008-01-01

    Full Text Available Fission products deposited in the coolant circuit outside of the active core play a dominant role in source term estimations for advanced small pebble bed HTRs, particularly in design basis accidents (DBA. The deposited fission products may be released in depressurization accidents because present pebble bed HTR concepts abstain from a gas tight containment. Contamination of the circuit also hinders maintenance work. Experiments, performed from 1972 to 88 on the AVR, an experimental pebble bed HTR, allow for a deeper insight into fission product transport behavior. The activity deposition per coolant pass was lower than expected and was influenced by fission product chemistry and by presence of carbonaceous dust. The latter lead also to inconsistencies between Cs plate out experiments in laboratory and in AVR. The deposition behavior of Ag was in line with present models. Dust as activity carrier is of safety relevance because of its mobility and of its sorption capability for fission products. All metal surfaces in pebble bed reactors were covered by a carbonaceous dust layer. Dust in AVR was produced by abrasion in amounts of about 5 kg/y. Additional dust sources in AVR were ours oil ingress and peeling of fuel element surfaces due to an air ingress. Dust has a size of about 1  m, consists mainly of graphite, is partly remobilized by flow perturbations, and deposits with time constants of 1 to 2 hours. In future reactors, an efficient filtering via a gas tight containment is required because accidents with fast depressurizations induce dust mobilization. Enhanced core temperatures in normal operation as in AVR and broken fuel pebbles have to be considered, as inflammable dust concentrations in the gas phase.

  3. A safety re-evaluation of the AVR pebble bed reactor operation and its consequences for future HTR concepts

    Energy Technology Data Exchange (ETDEWEB)

    Moormann, R.

    2008-06-15

    The AVR pebble bed reactor (46 MW{sub th}) was operated 1967-88 at coolant outlet temperatures up to 990 C. A principle difference of pebble bed HTRs as AVR to conventional reactors is the continuous movement of fuel element pebbles through the core which complicates thermohydraulic, nuclear and safety estimations. Also because of a lack of other experience AVR operation is still a relevant basis for future pebble bed HTRs and thus requires careful examination. This paper deals mainly with some insufficiently published unresolved safety problems of AVR operation and of pebble bed HTRs but skips the widely known advantageous features of pebble bed HTRs. The AVR primary circuit is heavily contaminated with metallic fission products (Sr-90, Cs-137) which create problems in current dismantling. The amount of this contamination is not exactly known, but the evaluation of fission product deposition experiments indicates that the end of life contamination reached several percent of a single core inventory, which is some orders of magnitude more than precalculated and far more than in large LWRs. A major fraction of this contamination is bound on graphitic dust and thus partly mobile in depressurization accidents, which has to be considered in safety analyses of future reactors. A re-evaluation of the AVR contamination is performed here in order to quantify consequences for future HTRs (400 MW{sub th}). It leads to the conclusion that the AVR contamination was mainly caused by inadmissible high core temperatures, increasing fission product release rates, and not - as presumed in the past - by inadequate fuel quality only. The high AVR core temperatures were detected not earlier than one year before final AVR shut-down, because a pebble bed core cannot yet be equipped with instruments. The maximum core temperatures are still unknown but were more than 200 K higher than calculated. Further, azimuthal temperature differences at the active core margin of up to 200 K were

  4. Installation of a three-dimensional simulation method for core-physical description of pebble bed reactors with multiple recycling process at the example of the AVR

    International Nuclear Information System (INIS)

    To describe the core-physical behaviour of pebble bed reactors simulation models are used, which reproduce the burn-up/recycling and - resulting - calculate criticality and neutron spectrum as well as neutron flux and temperature distribution. Modelling the AVR-reactor requires a three-dimensional treating for detailed considerations because of the graphite noses extending into the core. Such a system is built up in the present work and compared with the results of the two-dimensional model standardizated from operational side. The agreement is so good that the latter one is sufficient for the calculations accompanying the operation. The comparison with results of measurement is very satisfying in regard to fuel element distribution and temperature coefficient. As in all theoretical investigations there stays a discrepance of a little more than 1 nile against the measurement at the reactivity equivalence of the AVR rod-bank. On the other hand it is possible to reproduce the rod-bank curve resulting of the calibration very exactly with the present model. (orig.)

  5. Pebble bed pebble motion: Simulation and Applications

    CERN Document Server

    Cogliati, Joshua J

    2011-01-01

    This dissertation presents a method for simulation of motion of the pebbles in a PBR. A new mechanical motion simulator, PEBBLES, efficiently simulates the key elements of motion of the pebbles in a PBR. This model simulates gravitational force and contact forces including kinetic and true static friction. It's used for a variety of tasks including simulation of the effect of earthquakes on a PBR, calculation of packing fractions, Dancoff factors, pebble wear and the pebble force on the walls. The simulator includes a new differential static friction model for the varied geometries of PBRs. A new static friction benchmark was devised via analytically solving the mechanics equations to determine the minimum pebble-to-pebble friction and pebble-to-surface friction for a five pebble pyramid. This pyramid check as well as a comparison to the Janssen formula was used to test the new static friction equations. Because larger pebble bed simulations involve hundreds of thousands of pebbles and long periods of time, P...

  6. Pebble-bed pebble motion: Simulation and Applications

    Energy Technology Data Exchange (ETDEWEB)

    Joshua J. Cogliati; Abderrafi M. Ougouag

    2011-11-01

    Pebble bed reactors (PBR) have moving graphite fuel pebbles. This unique feature provides advantages, but also means that simulation of the reactor requires understanding the typical motion and location of the granular flow of pebbles. This report presents a method for simulation of motion of the pebbles in a PBR. A new mechanical motion simulator, PEBBLES, efficiently simulates the key elements of motion of the pebbles in a PBR. This model simulates gravitational force and contact forces including kinetic and true static friction. It's used for a variety of tasks including simulation of the effect of earthquakes on a PBR, calculation of packing fractions, Dancoff factors, pebble wear and the pebble force on the walls. The simulator includes a new differential static friction model for the varied geometries of PBRs. A new static friction benchmark was devised via analytically solving the mechanics equations to determine the minimum pebble-to-pebble friction and pebble-to-surface friction for a five pebble pyramid. This pyramid check as well as a comparison to the Janssen formula was used to test the new static friction equations. Because larger pebble bed simulations involve hundreds of thousands of pebbles and long periods of time, the PEBBLES code has been parallelized. PEBBLES runs on shared memory architectures and distributed memory architectures. For the shared memory architecture, the code uses a new O(n) lock-less parallel collision detection algorithm to determine which pebbles are likely to be in contact. The new collision detection algorithm improves on the traditional non-parallel O(n log(n)) collision detection algorithm. These features combine to form a fast parallel pebble motion simulation. The PEBBLES code provides new capabilities for understanding and optimizing PBRs. The PEBBLES code has provided the pebble motion data required to calculate the motion of pebbles during a simulated earthquake. The PEBBLES code provides the ability to

  7. Numerical simulation of nuclear pebble bed configurations

    Energy Technology Data Exchange (ETDEWEB)

    Shams, A., E-mail: shams@nrg.eu [Nuclear Research and Consultancy Group (NRG), Petten (Netherlands); Roelofs, F., E-mail: roelofs@nrg.eu [Nuclear Research and Consultancy Group (NRG), Petten (Netherlands); Komen, E.M.J., E-mail: komen@nrg.eu [Nuclear Research and Consultancy Group (NRG), Petten (Netherlands); Baglietto, E., E-mail: emiliob@MIT.EDU [Massachusetts Institute of Technology (MIT) (United States)

    2015-08-15

    Highlights: • Numerical simulations of a single face cubic centred pebble bed are performed. • Wide range of turbulence modelling techniques are used to perform these calculations. • The methods include 1-DNS, 1-LES, 3-Hybrid (RANS/LES) and 3-RANS models, respectively. • The obtained results are extensively compared to provide guidelines for such flow regimes. • These guidelines are used to perform reference LES for a limited sized random pebble bed. - Abstract: High Temperature Reactors (HTRs) are being considered all over the world. An HTR uses helium gas as a coolant, while the moderator function is taken up by graphite. The fuel is embedded in the graphite moderator. A particular inherent safety advantage of HTR designs is that the graphite can withstand very high temperatures, that the fuel inside will stay inside the graphite pebble and cannot escape to the surroundings even in the event of loss of cooling. Generally, the core can be designed using a graphite pebble bed. Some experimental and demonstration reactors have been operated using a pebble bed design. The test reactors have shown safe and efficient operation, however questions have been raised about possible occurrence of local hot spots in the pebble bed which may affect the pebble integrity. Analysis of the fuel integrity requires detailed evaluation of local heat transport phenomena in a pebble bed, and since such phenomena cannot easily be modelled experimentally, numerical simulations are a useful tool. As a part of a European project, named Thermal Hydraulics of Innovative Nuclear Systems (THINS), a benchmarking quasi-direct numerical simulation (q-DNS) of a well-defined pebble bed configuration has been performed. This q-DNS will serve as a reference database in order to evaluate the prediction capabilities of different turbulence modelling approaches. A wide range of numerical simulations based on different available turbulence modelling approaches are performed and compared with

  8. Mechanism analysis of quasi-static dense pebble flow in pebble bed reactor using phenomenological approach

    International Nuclear Information System (INIS)

    Highlights: ► We introduced four basic forms of phenomenological method for pebble flow. ► We discussed the physical nature of the quasi-static pebble flow. ► We verified the applicability of the discrete element method. ► We investigated the parameter effects on quasi-static pebble flow. - Abstract: By means of the four basic forms of the phenomenological method, experimental results have intuitionally disclosed the physical mechanism from various views of the quasi-static pebble flow in a pebble bed reactor and successfully verified the availability of the discrete element method, on which the parameter effects have been investigated, including different base cone angle and different friction coefficient. The flow fields under different parameters have been discussed. On the basis of these researches, a framework of the general understanding of pebble flow mechanism has been drawn; many essential problems are discussed, including the interpretation of the quasi-static pebble flow, force analysis inside the pebble packing, propagation and distribution of the voids, internal equilibrium arches, competition mechanism, internal collapse, self-organization, equivalent shear force, equivalent normal force, the physical process of stagnant zone's influence on the overall flow field, and so on. All of these are very helpful to understand the physical mechanism of the quasi-static pebble flow in a pebble bed reactor.

  9. Experimental and computational investigation of flow of pebbles in a pebble bed nuclear reactor

    Science.gov (United States)

    Khane, Vaibhav B.

    The Pebble Bed Reactor (PBR) is a 4th generation nuclear reactor which is conceptually similar to moving bed reactors used in the chemical and petrochemical industries. In a PBR core, nuclear fuel in the form of pebbles moves slowly under the influence of gravity. Due to the dynamic nature of the core, a thorough understanding about slow and dense granular flow of pebbles is required from both a reactor safety and performance evaluation point of view. In this dissertation, a new integrated experimental and computational study of granular flow in a PBR has been performed. Continuous pebble re-circulation experimental set-up, mimicking flow of pebbles in a PBR, is designed and developed. Experimental investigation of the flow of pebbles in a mimicked test reactor was carried out for the first time using non-invasive radioactive particle tracking (RPT) and residence time distribution (RTD) techniques to measure the pebble trajectory, velocity, overall/zonal residence times, flow patterns etc. The tracer trajectory length and overall/zonal residence time is found to increase with change in pebble's initial seeding position from the center towards the wall of the test reactor. Overall and zonal average velocities of pebbles are found to decrease from the center towards the wall. Discrete element method (DEM) based simulations of test reactor geometry were also carried out using commercial code EDEM(TM) and simulation results were validated using the obtained benchmark experimental data. In addition, EDEM(TM) based parametric sensitivity study of interaction properties was carried out which suggests that static friction characteristics play an important role from a packed/pebble beds structural characterization point of view. To make the RPT technique viable for practical applications and to enhance its accuracy, a novel and dynamic technique for RPT calibration was designed and developed. Preliminary feasibility results suggest that it can be implemented as a non

  10. Core Physics of Pebble Bed High Temperature Nuclear Reactors

    NARCIS (Netherlands)

    Auwerda, G.J.

    2014-01-01

    To more accurately predict the temperature distribution inside the reactor core of pebble bed type high temperature reactors, in this thesis we investigated the stochastic properties of randomly stacked beds and the effects of the non-homogeneity of these beds on the neutronics and thermal-hydraulic

  11. Nuclear Safeguards Considerations For The Pebble Bed Modular Reactor (PBMR)

    Energy Technology Data Exchange (ETDEWEB)

    Phillip Casey Durst; David Beddingfield; Brian Boyer; Robert Bean; Michael Collins; Michael Ehinger; David Hanks; David L. Moses; Lee Refalo

    2009-10-01

    High temperature reactors (HTRs) have been considered since the 1940s, and have been constructed and demonstrated in the United Kingdom (Dragon), United States (Peach Bottom and Fort Saint Vrain), Japan (HTTR), Germany (AVR and THTR-300), and have been the subject of conceptual studies in Russia (VGM). The attraction to these reactors is that they can use a variety of reactor fuels, including abundant thorium, which upon reprocessing of the spent fuel can produce fissile U-233. Hence, they could extend the stocks of available uranium, provided the fuel is reprocessed. Another attractive attribute is that HTRs typically operate at a much higher temperature than conventional light water reactors (LWRs), because of the use of pyrolytic carbon and silicon carbide coated (TRISO) fuel particles embedded in ceramic graphite. Rather than simply discharge most of the unused heat from the working fluid in the power plant to the environment, engineers have been designing reactors for 40 years to recover this heat and make it available for district heating or chemical conversion plants. Demonstrating high-temperature nuclear energy conversion was the purpose behind Fort Saint Vrain in the United States, THTR-300 in Germany, HTTR in Japan, and HTR-10 and HTR-PM, being built in China. This resulted in nuclear reactors at least 30% or more thermodynamically efficient than conventional LWRs, especially if the waste heat can be effectively utilized in chemical processing plants. A modern variant of high temperature reactors is the Pebble Bed Modular Reactor (PBMR). Originally developed in the United States and Germany, it is now being redesigned and marketed by the Republic of South Africa and China. The team examined historical high temperature and high temperature gas reactors (HTR and HTGR) and reviewed safeguards considerations for this reactor. The following is a preliminary report on this topic prepared under the ASA-100 Advanced Safeguards Project in support of the NNSA Next

  12. Effect of wall structure on pebble stagnation behavior in pebble bed reactor

    International Nuclear Information System (INIS)

    Highlights: • DEM study of wall structure role in preventing near wall crystallization is carried out. • Suggestions on pebble’s kinematic parameters and wall structure design are provided. • Triangle is better than arc and sawtooth shapes for wall structure design. • Wall structure size should be close to the scale of pebble diameter. • Suitable intervals can prevent crystallization without significantly increasing the flow resistance. - Abstract: Crystallization of pebbles in pebble bed is a crucial problem in high temperature gas-cooled pebble-bed reactors. This phenomenon usually happens along the internal surface and leads to a large number of stagnated pebbles, which poses a threat to reactor safety. In real reactor engineering, wall structures have been utilized to avoid this problem. This article verifies the crystallization phenomenon through DEM (discrete element method) simulation, and explains how wall structures work in preventing crystallization. Moreover, several kinematic parameters have been adopted to evaluate wall structures with different shapes, sizes and intervals. Detailed information shows the impact of wall structure on flow field in pebble bed. Lastly, the preferred characteristics of an effective wall structure are suggested for reactor engineering

  13. Optimization of MOX fuel cycles in pebble bed HTGR

    International Nuclear Information System (INIS)

    Compared with light water reactor (LWR), the pebble bed high temperature gas-cooled reactor (HTGR) is able to operate in a full mixed oxide (MOX) fuelled core without significant change to core structure design. Based on a reference design of 250 MW pebble bed HTGR, four MOX fuel cycles were designed and evaluated by VSOP program package, including the mixed Pu-U fuel pebbles and mixed loading of separate Pu-pebbles and U-pebbles. Some important physics features were investigated and compared for these four cycles, such as the effective multiplication factor of initial core, the pebble residence time, discharge burnup, and temperature coefficients. Preliminary results show that the overall performance of one case is superior to other equivalent MOX fuel cycles on condition that uranium fuel elements and plutonium fuel elements are separated as the different fuel pebbles and that the uranium fuel elements are irradiated longer in the core than the plutonium fuel elements, and the average discharge burnup of this case is also higher than others. (authors)

  14. Initial prediction of dust production in pebble bed reactors

    Directory of Open Access Journals (Sweden)

    M. Rostamian

    2011-09-01

    Full Text Available This paper describes the computational simulation of contact zones between pebbles in a pebble bed reactor. In this type of reactor, the potential for graphite dust generation from frictional contact of graphite pebbles and the subsequent transport of dust and fission products can cause significant safety issues at very high temperatures around 900 °C in HTRs. The present simulation is an initial attempt to quantify the amount of nuclear grade graphite dust produced within a very high temperature reactor.

  15. PEBBLE: a two-dimensional steady-state pebble bed reactor thermal hydraulics code

    International Nuclear Information System (INIS)

    This report documents the local implementation of the PEBBLE code to treat the two-dimensional steady-state pebble bed reactor thermal hydraulics problem. This code is implemented as a module of a computation system used for reactor core history calculations. Given power density data, the geometric description in (RZ), and basic heat removal conditions and thermal properties, the coolant properties, flow conditions, and temperature distributions in the pebble fuel elements are predicted. The calculation is oriented to the continuous fueling, steady state condition with consideration of the effect of the high energy neutron flux exposure and temperature history on the thermal conductivity. The coolant flow conditions are calculated for the same geometry as used in the neutronics calculation, power density and fluence data being used directly, and temperature results are made available for subsequent use

  16. PEBBLE: a two-dimensional steady-state pebble bed reactor thermal hydraulics code

    Energy Technology Data Exchange (ETDEWEB)

    Vondy, D.R.

    1981-09-01

    This report documents the local implementation of the PEBBLE code to treat the two-dimensional steady-state pebble bed reactor thermal hydraulics problem. This code is implemented as a module of a computation system used for reactor core history calculations. Given power density data, the geometric description in (RZ), and basic heat removal conditions and thermal properties, the coolant properties, flow conditions, and temperature distributions in the pebble fuel elements are predicted. The calculation is oriented to the continuous fueling, steady state condition with consideration of the effect of the high energy neutron flux exposure and temperature history on the thermal conductivity. The coolant flow conditions are calculated for the same geometry as used in the neutronics calculation, power density and fluence data being used directly, and temperature results are made available for subsequent use.

  17. Pebble Bed Reactor review update. Fiscal year 1979 annual report

    International Nuclear Information System (INIS)

    Updated information is presented on the Pebble Bed Reactor (PBR) concept being developed in the Federal Republic of Germany for electricity generation and process heat applications. Information is presented concerning nuclear analysis and core performance, fuel cycle evaluation, reactor internals, and safety and availability

  18. Pebble Bed Reactor review update. Fiscal year 1979 annual report

    Energy Technology Data Exchange (ETDEWEB)

    1980-01-01

    Updated information is presented on the Pebble Bed Reactor (PBR) concept being developed in the Federal Republic of Germany for electricity generation and process heat applications. Information is presented concerning nuclear analysis and core performance, fuel cycle evaluation, reactor internals, and safety and availability.

  19. Modelling of thermal and mechanical behaviour of pebble beds

    International Nuclear Information System (INIS)

    FZK (Forshungzentrum Karlsruhe) is developing a Helium Cooled Pebble Bed (HCPB) Blanket Concept for fusion power reactors based on the use of ceramic breeder materials and beryllium multiplier in the form of pebble beds. The design of such a blanket requires models and computer codes describing the thermal-mechanical behavior of pebble beds to evaluate the temperatures, stresses, deformations and mechanical interactions between pebble beds and the structure with required accuracy and reliability. The objective to describe the beginning of life condition for the HCPB blanket seems near to be reached. Mechanical models that describe the thermo-mechanical behavior of granular materials used in form of pebble beds are implemented in a commercial structure code. These models have been calibrated using the results of a large series of dedicated experiments. The modeling work is practically concluded for ceramic breeder; it will be carried on in the next year for beryllium to obtain the required correlations for creep and the thermal conductivity. The difficulties for application in large components (such as the HCPB blanket) are the limitations of the present commercial codes to manage such a set of constitutive equations under complex load conditions and large mesh number. The further objective is to model the thermal cycles during operation; the present correlations have to be adapted for the release phase. A complete description of the blanket behavior during irradiation is at the present out of our capability; this objective requires an extensive R and D program that at the present is only at the beginning. (Y.Tanaka)

  20. PEBBED ANALYSIS OF HOT SPOTS IN PEBBLE-BED REACTORS

    Energy Technology Data Exchange (ETDEWEB)

    Abderrafi M. Ougouag; Hans D. Gougar; William K. Terry; Frederik Reitsma; Wessel Joubert

    2005-09-01

    The Idaho National Laboratory’s PEBBED code and simple probability considerations are used to estimate the likelihood and consequences of the accumulation of highly reactive pebbles in the region of peak power in a pebble-bed reactor. The PEBBED code is briefly described, and the logic of the probability calculations is presented in detail. The results of the calculations appear to show that hot-spot formation produces only moderate increases in peak accident temperatures, and no increases at all in normal operating temperatures.

  1. Computational prediction of dust production in pebble bed reactors

    International Nuclear Information System (INIS)

    Highlights: ► Finite element analysis of frictional contact. ► Plasticity taken into account for nuclear graphite at room temperature. ► Prediction of order of magnitude for dust loading in PBRs. ► Archard wear model for wear mass calculations. - Abstract: This paper describes the computational modeling and simulation of graphite pebbles in frictional contacts as anticipated in a pebble bed reactor. For the high temperature gas-cooled reactor, the potential dust generation from frictional contact at the surface of pebbles and the subsequent lift-off and transport of dust and absorbed fission products are of safety concern at elevated temperatures under an air ingress accident. The aim of this work is to perform a computational study to estimate the quantity of the nuclear grade graphite dust produces from a typical anticipated configuration.

  2. Modeling of laminar forced convection in spherical- pebble packed beds

    International Nuclear Information System (INIS)

    There are many parameters that have significant effects on forced convection heat transfer in packed beds, including Reynolds and Prandtl numbers of flow, porosity, pebble geometry, local flow conditions, wall and end effects. In addition, there have been many experimental investigations on forced convection heat transfer in packed beds and each have studied the effect of some of these parameters. Yet, there is not a reliable correlation that includes the effect of main parameters: at the same time, the prediction of precise correct limits for very low and high Reynolds numbers is off hand. In this article a general well-known model of convection heat transfer from isothermal bodies, next to some previous reliable experimental data has been used as a basis for a more comprehensive and accurate correlation to calculate the laminar constant temperature pebble-fluid forced convection heat transfer in a homogeneous saturated bed with spherical pebbles. Finally, for corroboration, the present results are compared with previous works and show a very good agreement for laminar flows at any Prandtl number and all porosities

  3. Development of Chinese HTR-PM pebble bed equivalent conductivity test facility

    Energy Technology Data Exchange (ETDEWEB)

    Ren, Cheng; Yang, Xingtuan; Jiang, Shengyao [Tsinghua Univ., Beijing (China). Inst. of Nuclear and New Energy Technology

    2016-01-15

    The first two 250-MWt high-temperature reactor pebble bed modules (HTR-PM) have been installing at the Shidaowan plant in Shandong Province, China. The values of the effective thermal conductivity of the pebble bed core are essential parameters for the design. For their determination, Tsinghua University in China has proposed a full-scale heat transfer experiment to conduct comprehensive thermal transfer tests in packed pebble bed and to determine the effective thermal conductivity.

  4. Benchmark Evaluation of HTR-PROTEUS Pebble Bed Experimental Program

    International Nuclear Information System (INIS)

    Benchmark models were developed to evaluate 11 critical core configurations of the HTR-PROTEUS pebble bed experimental program. Various additional reactor physics measurements were performed as part of this program; currently only a total of 37 absorber rod worth measurements have been evaluated as acceptable benchmark experiments for Cores 4, 9, and 10. Dominant uncertainties in the experimental keff for all core configurations come from uncertainties in the 235U enrichment of the fuel, impurities in the moderator pebbles, and the density and impurity content of the radial reflector. Calculations of keff with MCNP5 and ENDF/B-VII.0 neutron nuclear data are greater than the benchmark values but within 1% and also within the 3σ uncertainty, except for Core 4, which is the only randomly packed pebble configuration. Repeated calculations of keff with MCNP6.1 and ENDF/B-VII.1 are lower than the benchmark values and within 1% (~3σ) except for Cores 5 and 9, which calculate lower than the benchmark eigenvalues within 4σ. The primary difference between the two nuclear data libraries is the adjustment of the absorption cross section of graphite. Simulations of the absorber rod worth measurements are within 3σ of the benchmark experiment values. The complete benchmark evaluation details are available in the 2014 edition of the International Handbook of Evaluated Reactor Physics Benchmark Experiments

  5. Characterization of the thermal conductivity for ceramic pebble beds

    Science.gov (United States)

    Lo Frano, R.; Aquaro, D.; Scaletti, L.; Olivi, N.

    2015-11-01

    The evaluation of the thermal conductivity of breeder materials is one of the main goals to find the best candidate material for the fusion reactor technology. The aim of this paper is to evaluate experimentally the thermal conductivity of a ceramic material by applying the hot wire method at different temperatures, ranging from 50 to about 800°C. The updated experimental facility, available at the Department of Civil and Industrial Engineering (DICI) of the University of Pisa, used to determine the thermal conductivity of a ceramic material (alumina), will be described along with the measurement acquisition system. Moreover it will be also provided an overview of the current state of art of the ceramic pebble bed breeder thermos-mechanics R&D (e.g. Lithium Orthosilicate (Li4SiO4) and Lithium Metatitanate (Li2TiO3)) focusing on the up-to-date analysis. The methodological approach adopted is articulated in two phase: the first one aimed at the experimental evaluation of thermal conductivity of a ceramic material by means of hot wire method, to be subsequently used in the second phase that is based on the test rig method, through which is measured the thermal conductivity of pebble bed material. In this framework, the experimental procedure and the measured results obtained varying the temperature, are presented and discussed.

  6. Steady-state thermal-hydraulic of pebble bed blanket on hybrid reactor

    International Nuclear Information System (INIS)

    This paper gives thermal-hydraulic studies of pebble bed blanket on Hybrid Reactor. The concept of whole pebble bed blanket and the cooling methods are presented. The thermal-hydraulic characteristics of pebble bed are summarized. The theoretical model and code for solving heat transfer and flowing are presented. By using this code the calculation and analysis of thermal hydraulic of pebble bed Blanket of Hybrid Reactor are also given. In order to improve the flexibility, safety and economy, the authors select pebble beds not only to breed Tritium, but also to breed fission material and to multiply neutron. 5 MPa Helium is used as coolant and 0.05 MPa-0.1 MPa Helium is used as Purge gas. The heat transfer mechanisms of pebble bed are very complicated which include conduction, convection and radiation. In order to study the thermal-hydraulic of the bed, the authors just simply consider it as homogeneous and continuous binary phase medium as that used in the porous medium at the condition that the size of the bed is much greater than that of the balls. The coolant or the purge gas flowing through the bed is just considered existing a cooling source in the bed. It also significantly influences the effective conductivity's of the bed. Porous fraction, the main factor of the bed depends on the geometry position and parameters. From this model, one can obtain the thermal-hydraulic governing equations of the bed

  7. Gas Reactor International Cooperative Program. Interim report. Safety and licensing evaluaion of German Pebble Bed Reactor concepts

    Energy Technology Data Exchange (ETDEWEB)

    1978-09-01

    The Pebble Bed Gas Cooled Reactor, as developed in the Federal Republic of Germany, was reviewed from a United States Safety and Licensing perspective. The primary concepts considered were the steam cycle electric generating pebble bed (HTR-K) and the process heat pebble bed (PNP), although generic consideration of the direct cycle gas turbine pebble bed (HHT) was included. The study examines potential U.S. licensing issues and offers some suggestions as to required development areas.

  8. Deleterious Thermal Effects Due To Randomized Flow Paths in Pebble Bed, and Particle Bed Style Reactors

    Science.gov (United States)

    Moran, Robert P.

    2013-01-01

    A review of literature associated with Pebble Bed and Particle Bed reactor core research has revealed a systemic problem inherent to reactor core concepts which utilize randomized rather than structured coolant channel flow paths. For both the Pebble Bed and Particle Bed Reactor designs; case studies reveal that for indeterminate reasons, regions within the core would suffer from excessive heating leading to thermal runaway and localized fuel melting. A thermal Computational Fluid Dynamics model was utilized to verify that In both the Pebble Bed and Particle Bed Reactor concepts randomized coolant channel pathways combined with localized high temperature regions would work together to resist the flow of coolant diverting it away from where it is needed the most to cooler less resistive pathways where it is needed the least. In other words given the choice via randomized coolant pathways the reactor coolant will take the path of least resistance, and hot zones offer the highest resistance. Having identified the relationship between randomized coolant channel pathways and localized fuel melting it is now safe to assume that other reactor concepts that utilize randomized coolant pathways such as the foam core reactor are also susceptible to this phenomenon.

  9. Pore Scale Thermal Hydraulics Investigations of Molten Salt Cooled Pebble Bed High Temperature Reactor with BCC and FCC Configurations

    Directory of Open Access Journals (Sweden)

    Shixiong Song

    2014-01-01

    CFD results and empirical correlations’ predictions of pressure drop and local Nusselt numbers. Local pebble surface temperature distributions in several default conditions are investigated. Thermal removal capacities of molten salt are confirmed in the case of nominal condition; the pebble surface temperature under the condition of local power distortion shows the tolerance of pebble in extreme neutron dose exposure. The numerical experiments of local pebble insufficient cooling indicate that in the molten salt cooled pebble bed reactor, the pebble surface temperature is not very sensitive to loss of partial coolant. The methods and results of this paper would be useful for optimum designs and safety analysis of molten salt cooled pebble bed reactors.

  10. Preliminary safety analysis of a thorium high-conversion pebble bed reactor

    International Nuclear Information System (INIS)

    An inherently safe thorium High-Conversion Pebble Bed Reactor would combine the inherent safety characteristics of the Pebble Bed Reactor with the favourable waste characteristics and resource availability of the thorium fuel cycle. Previous work by the authors showed that high conversion ratio's can be achieved within a thorium Pebble Bed Reactor (PBR) at a practical operating regime. The thorium PBR core design consists of a cylindrical core with a central driver zone surrounded by a breeder zone. The breeder pebbles have a 30 g heavy metal (HM) loading to enhance conversion of Th-232 into U-233, while the driver pebbles (10 w% U-233) contain a lower metal loading to enhance fission. In previous studies, thorium PBR designs were presented for three core diameters, using a 7.5 g heavy metal (HM) loading for the driver pebbles. The current paper investigates the safety of these thorium PBR designs in terms of reactivity coefficients and possible reactivity insertion due to water ingress. Early results indicated that the values of the reactivity coefficients for the three designs with 7.5 g HM loading per driver pebble were rather small and the possible reactivity insertion due to water ingress was very large. Therefore, also a lower HM loading per driver pebble (4 g) was investigated to reduce the impact of water ingress, since the core becomes less under-moderated. For the three core diameters investigated, it is shown that reducing the metal loading in the driver pebbles to 4 g is indeed advantageous in terms of safety, water ingress leads to a smaller reactivity increase but also the reactivity coefficients become stronger negative. Secondly, the breeding performance of the cores with a 4 g driver pebble HM loading improves. On the downside, the driver pebble residence times become shorter, which could increase fuel reprocessing costs. Fuel pebbles would have to be recycled at an increased rate, which might be more challenging from a practical perspective

  11. Positron emission tomography in pebble beds. Part 1: Liquid particle deposition

    Energy Technology Data Exchange (ETDEWEB)

    Barth, T., E-mail: t.barth@hzdr.de [Helmholtz-Zentrum Dresden-Rossendorf, Institute of Fluid Dynamics (IFD), Bautzner Landstraße 400, 01328 Dresden (Germany); Ludwig, M. [Helmholtz-Zentrum Dresden-Rossendorf, Institute of Fluid Dynamics (IFD), Bautzner Landstraße 400, 01328 Dresden (Germany); Kulenkampff, J.; Gründig, M. [Helmholtz-Zentrum Dresden-Rossendorf, Institute of Resource Ecology (IRE), Permoserstraße 15, 04318 Leipzig (Germany); Franke, K. [Helmholtz-Zentrum Dresden-Rossendorf, Institute of Resource Ecology (IRE), Permoserstraße 15, 04318 Leipzig (Germany); Helmholtz-Zentrum Dresden-Rossendorf, Institute of Radiopharmacy (IRP), Permoserstraße 15, 04318 Leipzig (Germany); Lippmann-Pipke, J. [Helmholtz-Zentrum Dresden-Rossendorf, Institute of Resource Ecology (IRE), Permoserstraße 15, 04318 Leipzig (Germany); Hampel, U. [Helmholtz-Zentrum Dresden-Rossendorf, Institute of Fluid Dynamics (IFD), Bautzner Landstraße 400, 01328 Dresden (Germany); Helmholtz-Zentrum Dresden-Rossendorf, AREVA Endowed Chair of Imaging Techniques in Energy and Process Engineering, Technische Universität Dresden, 01062 Dresden (Germany)

    2014-02-15

    Highlights: • Particle deposition in a pebble bed was recorded by positron emission tomography. • The particles were radioactively labelled and their spatial distribution was recorded. • Particle deposition was mainly driven by particle inertia and turbulent dispersion. • Particle deposits form hot spots on the upstream face of the single pebbles. - Abstract: Accidental scenarios such as the depressurisation of the primary circuit of high temperature gas cooled pebble bed reactors may lead to the release of fission products via the discharge of radioactive graphite dust. For a detailed source term assessment in such accident scenarios knowledge of the flow mechanics of dust transport in complex coolant circuit components, like pebble beds, recuperator structures and pipe systems is necessary. In this article an experimental study of aerosol deposition in a pebble bed is described. We investigated the deposition of radiolabelled liquid aerosol particles in a scaled pebble bed in an air-driven small-scale aerosol flow test facility under isothermal ambient conditions. The aerosol particles were generated by means of a condensational aerosol generator with potassium-fluoride (KF) condensation nuclei. Particle concentration measurements upstream and downstream of the pebble bed were performed by isokinetic sampling and particle counting. The results agree with typical deposition curves for turbulent and inertia driven particle deposition. Furthermore, positron emission tomography (PET) was performed to visualize and measure particle deposition distributions in the pebble bed. Results of a selected deposition experiment with moderately large particles (d{sub aero} = 3.5 μm, Re{sup ′}{sub pb}=2200) show that the deposited particles are located in the vicinity of the upstream stagnation points of the pebbles. These findings support the thesis that inertia driven particle deposition is predominating.

  12. Experimental studies on heat transfer and pressure drop in pebble bed test facility

    International Nuclear Information System (INIS)

    Indian program for development of high temperature reactor and its utilization to supply process heat aimed to develop alternate fuel carrier to substitute petroleum based transport fuel, which has very small reserves in India and results in large import bills. Hydrogen is an attractive energy carrier for transport applications. It can be produced by splitting water which requires either electricity or process heat at high temperatures or both depending upon the process selected. BARC is carrying out design of a 600 MWth reactor capable of supplying process heat at around 1000 °C as required for hydrogen production. For this reactor various design options with respect to fuel configurations, such as prismatic bed and pebble bed were considered for thermal hydraulics analysis. Coolant options such as molten lead and molten salt were analyzed. Studies carried out indicate selection of pebble bed reactor core with molten salt as coolant. Thermal-hydraulic studies are required for pebble bed reactor. With this in view, a pebble bed test facility has been setup to study the heat transfer and pressure drop in pebble bed. Water is used as a working medium for the facility. The paper deals with the description of the pebble bed test facility and the experimental results of heat transfer and pressure drop. It also deals with the assessment of correlations for heat transfer and pressure drop in pebble bed geometry. Pressure drop experiments in the pebble bed test facility have been performed for Raynolds number ranges from 3000-12000. Various pressure drop correlations have been compared with the experimental data. It has been found that that the correlation given by Leva et. al. matches well with the experimental data. Various heat transfer correlations have also been compared. Heat transfer experiments are nearing completion

  13. Modularity of the MIT Pebble Bed Reactor for use by the commercial power industry

    OpenAIRE

    Hanlon-Hyssong, Jaime E.

    2008-01-01

    CIVINS The Modular Pebble Bed Reactor is a small high temperature helium cooled reactor that is being considered for both electric power and hydrogen production. Pebble bed reactors are being developed in South Africa, China and the US. To make smaller 120 Mwe reactors economically competitive with larger 1500 Mwe traditional light water reactors changes in the way these plants are built are needed. Economies of production need to be sufficiently large to compete with economies of sca...

  14. Pebble Bed Reactors Design Optimization Methods and their Application to the Pebble Bed Fluoride Salt Cooled High Temperature Reactor (PB-FHR)

    Science.gov (United States)

    Cisneros, Anselmo Tomas, Jr.

    The Fluoride salt cooled High temperature Reactor (FHR) is a class of advanced nuclear reactors that combine the robust coated particle fuel form from high temperature gas cooled reactors, direct reactor auxillary cooling system (DRACS) passive decay removal of liquid metal fast reactors, and the transparent, high volumetric heat capacitance liquid fluoride salt working fluids---flibe (33%7Li2F-67%BeF)---from molten salt reactors. This combination of fuel and coolant enables FHRs to operate in a high-temperature low-pressure design space that has beneficial safety and economic implications. In 2012, UC Berkeley was charged with developing a pre-conceptual design of a commercial prototype FHR---the Pebble Bed- Fluoride Salt Cooled High Temperature Reactor (PB-FHR)---as part of the Nuclear Energy University Programs' (NEUP) integrated research project. The Mark 1 design of the PB-FHR (Mk1 PB-FHR) is 236 MWt flibe cooled pebble bed nuclear heat source that drives an open-air Brayton combine-cycle power conversion system. The PB-FHR's pebble bed consists of a 19.8% enriched uranium fuel core surrounded by an inert graphite pebble reflector that shields the outer solid graphite reflector, core barrel and reactor vessel. The fuel reaches an average burnup of 178000 MWt-d/MT. The Mk1 PB-FHR exhibits strong negative temperature reactivity feedback from the fuel, graphite moderator and the flibe coolant but a small positive temperature reactivity feedback of the inner reflector and from the outer graphite pebble reflector. A novel neutronics and depletion methodology---the multiple burnup state methodology was developed for an accurate and efficient search for the equilibrium composition of an arbitrary continuously refueled pebble bed reactor core. The Burnup Equilibrium Analysis Utility (BEAU) computer program was developed to implement this methodology. BEAU was successfully benchmarked against published results generated with existing equilibrium depletion codes VSOP

  15. Experimental reactivity assessment during AVR defuelling

    Energy Technology Data Exchange (ETDEWEB)

    Pohl, P. [Arbeitsgemeinschaft Versuchs-Reaktor GmbH, Duesseldorf (Germany)

    1996-07-01

    In defuelling the AVR experimental nuclear power plant with pebble bed high temperature gas-cooled reactor positive reactivity effects are to be considered. The development of subcriticality with defuelling was therefore monitored by measurement. As first, the subcriticality was assessed by accurate period measurements; later, when this method came to its limit, an approximation method was used that allowed the determination of subcriticality values of up to about 5.5% {Delta}k{sub eff}. (J.P.N.)

  16. STUDI PEMODELAN DAN PERHITUNGAN TRANSPORT MONTE CARLO DALAM TERAS HTR PEBBLE BED

    Directory of Open Access Journals (Sweden)

    Zuhair .

    2013-01-01

    Full Text Available Konsep sistem energi VHTR baik yang berbahan bakar pebble (VHTR pebble bed maupun blok prismatik (VHTR prismatik menarik perhatian fisikawan reaktor nuklir. Salah satu kelebihan teknologi bahan bakar bola adalah menawarkan terobosan teknologi pengisian bahan bakar tanpa harus menghentikan produksi listrik. Selain itu, partikel bahan bakar pebble dengan kernel uranium oksida (UO2 atau uranium oksikarbida (UCO yang dibalut TRISO dan pelapisan silikon karbida (SiC dianggap sebagai opsi utama dengan pertimbangan performa tinggi pada burn-up bahan bakar dan temperatur tinggi. Makalah ini mendiskusikan pemodelan dan perhitungan transport Monte Carlo dalam teras HTR pebble bed. HTR pebble bed adalah reaktor berpendingin gas temperatur tinggi dan bermoderator grafit dengan kemampuan kogenerasi. Perhitungan dikerjakan dengan program MCNP5 pada temperatur 1200 K. Pustaka data nuklir energi kontinu ENDF/B-V dan ENDF/B-VI dimanfaatkan untuk melengkapi analisis. Hasil perhitungan secara keseluruhan menunjukkan konsistensi dengan nilai keff yang hampir sama untuk pustaka data nuklir yang digunakan. Pustaka ENDF/B-VI (66c selalu memproduksi keff lebih besar dibandingkan ENDF/B-V (50c maupun ENDF/B-VI (60c dengan bias kurang dari 0,25%. Kisi BCC memprediksi keff hampir selalu lebih kecil daripada kisi lainnya, khususnya FCC. Nilai keff kisi BCC lebih dekat dengan kisi FCC dengan bias kurang dari 0,19% sedangkan dengan kisi SH bias perhitungannya kurang dari 0,22%. Fraksi packing yang sedikit berbeda (BCC= 61%, SH= 60,459% tidak membuat bias perhitungan menjadi berbeda jauh. Estimasi keff ketiga model kisi menyimpulkan bahwa model BCC lebih bisa diadopsi dalam perhitungan HTR pebble bed dibandingkan model FCC dan SH. Verifikasi hasil estimasi ini perlu dilakukan dengan simulasi Monte Carlo atau bahkan program deterministik lainnya guna optimisasi perhitungan teras reaktor temperatur tinggi.   Kata-kunci: kernel, TRISO, bahan bakar pebble, HTR pebble bed

  17. Thermal-hydraulics numerical analyses of Pebble Bed Advanced High Temperature Reactor hot channel

    International Nuclear Information System (INIS)

    Background: The thermal hydraulics behavior of the Pebble Bed Advanced High Temperature Reactor (PB-AHTR) hot channel was studied. Purpose: We aim to analyze the thermal-hydraulics behavior of the PB-AHTR, such as pressure drop, temperature distribution of coolant and pebble bed as well as thermal removal capacity in the condition of loss of partial coolant. Methods: We used a modified FLUENT code which was coupled with a local non-equilibrium porous media model by introducing a User Defined Scalar (UDS) in the calculation domain of the reactor core and subjoining different resistance terms (Ergun and KTA) to calculate the temperature of coolant, solid phase of pebble bed and pebble center in the core. Results: Computational results showed that the resistance factor has great influence on pressure drop and velocity distribution, but less impact on the temperature of coolant, solid phase of pebble bed and pebble center. We also confirmed the heat removal capacity of the PB-AHTR in the condition of nominal and loss of partial coolant conditions. Conclusion: The numerical analyses results can provide a useful proposal to optimize the design of PB-AHTR. (authors)

  18. Characterisation of thermal radiation in the near-wall region of a packed pebble bed / Maritza de Beer

    OpenAIRE

    De Beer, Maritza

    2014-01-01

    The heat transfer phenomena in the near-wall region of a randomly packed pebble bed are important in the design of a Pebble Bed Reactor (PBR), especially when considering the safety case during accident conditions. At higher temperatures the contribution of the radiation heat transfer component to the overall heat transfer in a PBR increases significantly. The wall effect present in the near-wall region of a packed pebble bed affects the heat transfer in this region. Various correlations e...

  19. Absorber rod for nuclear reactors in a pebble bed of spherical operating elements

    International Nuclear Information System (INIS)

    The claim refers to the constructional configuration of an absorber rod, whose and penetrating into the pebble bed has an opening to reduce the fracture rate, so that the operating elements can escape into a channel within the absorber rod. To suit this to the direction of movement of the elements a part of the end of the rod is flexibly connected to the hollow absorber rod via a joint. In this way the mechanical load of the element particles is reduced and simultaneously one achieves that much lower force is required to insert the absorber rod into the pebble bed. (UA)

  20. Prototype studies on the nondestructive online burnup determination for the modular pebble bed reactors

    International Nuclear Information System (INIS)

    Highlights: • Prototype study of online burnup measurement for HTR proves its feasibility. • Calibration and its correction of burnup assay device is discussed and verified. • Analysis of simulated gamma spectra shows good performance of spectra-unfolding method. - Abstract: The online fuel pebble burnup determination in future modular pebble bed reactor is implemented by measuring nondestructively the activity of the monitoring nuclide Cs-137 with HPGe detector on a pebble-by-pebble basis. Based on a full size prototype the feasibility is investigated. The prototype was first tested by using double sources to show that a precision of 2.8% (1σ) can be achieved in the determination of the Cs-137 net counting rate. Then, the relationship between the Cs-137 activity and the net counting rate recorded in the HPGe detector is calibrated with a standard Cs-137 source contained in the center of a graphite sphere with the same dimension as a real fuel pebble. Because the self attenuation of the calibration source differs with a fuel pebble, a correction factor of 1.07 ± 0.02 (p = 0.95) to the calibration is derived by using the efficiency transfer method. Last, by analyzing the spectra generated with KORIGEN software followed by Monte Carlo simulation, it is predicted that the relative standard deviation of the Cs-137 net counting rate can be still controlled below 3.5% despite of the presence of all the interfering peaks. The results demonstrate the feasibility of utilizing HPGe gamma spectrometry in the online determination of the pebble burnup in future modular pebble bed reactors

  1. Temperature transients of a fusion-fission ITER pebble bed reactor in loss of coolant accident

    International Nuclear Information System (INIS)

    In this preliminary scoping study, post-accident temperature transients of several fusion-fission designs utilizing ITER-FEAT-like parameters and fission pebble bed fuel technology are examined using a 1-D cylindrical MATLAB heat transfer code along with conventional fission decay heat approximations. Scenarios studied include systems with no additional passive safety features to systems with melting reflectors designed to increase emissivity after reaching a specified temperature. Results show that for a total fission power of ∼1400-2800 MW, two of the realistic variants investigated are passively safe. The crucial time, defined as the time when either any structural part of the fusion-fission tokamak reaches melting point, or when the pebble fuel reaches 1873 K, ranges from 5.7 to 76 h for the unsafe configurations. Additionally, it is illustrated that, fundamentally, the LOCA characteristics of pure fission pebble beds and fusion-fission pebble beds are different. Namely, the former depends on the pebble fuel's large thermal capacity, along with external radiation and natural convective cooling, while the latter depends significantly more on the tokamak's sizeable total internal heat capacity. This difference originates from the fusion-fission reactor's conflicting goal of having to minimize heat transfer to the magnets during normal operation. These results are discussed in the context of overall fusion-fission reactor design and safety

  2. Measurement of the thermal conductivity and heat transfer coefficient of a binary bed of beryllium pebbles

    Energy Technology Data Exchange (ETDEWEB)

    Donne, M.D.; Piazza, G. [Forschungszentrum Karlsruhe GmbH Technik und Umwelt (Germany). Inst. fuer Neutronenphysik und Reaktortechnik; Goraieb, A.; Sordon, G.

    1998-01-01

    The four ITER partners propose to use binary beryllium pebble bed as neutron multiplier. Recently this solution has been adopted for the ITER blanket as well. In order to study the heat transfer in the blanket the effective thermal conductivity and the wall heat transfer coefficient of the bed have to be known. Therefore at Forschungszentrum Karlsruhe heat transfer experiments have been performed with a binary bed of beryllium pebbles and the results have been correlated expressing thermal conductivity and wall heat transfer coefficients as a function of temperature in the bed and of the difference between the thermal expansion of the bed and of that of the confinement walls. The comparison of the obtained correlations with the data available from the literature show a quite good agreement. (author)

  3. Optimized core design and fuel management of a pebble-bed type nuclear reactor

    NARCIS (Netherlands)

    Boer, B.

    2009-01-01

    The core design of a pebble-bed type Very High Temperature Reactor (VHTR) is optimized, aiming for an increase of the coolant outlet temperature to 1000 C, while retaining its inherent safety features. The VHTR has been selected by the international Generation IV research initiative as one of the si

  4. Preliminary Neutronic Design of High Burnup OTTO Cycle Pebble Bed Reactor

    Directory of Open Access Journals (Sweden)

    T. Setiadipura

    2015-04-01

    Full Text Available The pebble bed type High Temperature Gas-cooled Reactor (HTGR is among the interesting nuclear reactor designs in terms of safety and flexibility for co-generation applications. In addition, the strong inherent safety characteristics of the pebble bed reactor (PBR which is based on natural mechanisms improve the simplicity of the PBR design, in particular for the Once-Through-Then-Out (OTTO cycle PBR design. One of the important challenges of the OTTO cycle PBR design, and nuclear reactor design in general, is improving the nuclear fuel utilization which is shown by attaining a higher burnup value. This study performed a preliminary neutronic design study of a 200 MWt OTTO cycle PBR with high burnup while fulfilling the safety criteria of the PBR design.The safety criteria of the design was represented by the per-fuel-pebble maximum power generation of 4.5 kW/pebble. The maximum burnup value was also limited by the tested maximum burnup value which maintained the integrity of the pebble fuel. Parametric surveys were performed to obtain the optimized parameters used in this study, which are the fuel enrichment, per-pebble heavy metal (HM loading, and the average axial speed of the fuel. An optimum design with burnup value of 131.1 MWd/Kg-HM was achieved in this study which is much higher compare to the burnup of the reference design HTR-MODUL and a previously proposed OTTO-cycle PBR design. This optimum design uses 17% U-235 enrichment with 4 g HM-loading per fuel pebble

  5. Preliminary neutronic design of high burnup OTTO cycle pebble bed reactor

    International Nuclear Information System (INIS)

    The pebble bed type High Temperature Gas-cooled Reactor (HTGR) is among the interesting nuclear reactor designs in terms of safety and flexibility for co-generation applications. In addition, the strong inherent safety characteristics of the pebble bed reactor (PBR) which is based on natural mechanisms improve the simplicity of the PBR design, in particular for the Once-Through-Then-Out (OTTO) cycle PBR design. One of the important challenges of the OTTO cycle PBR design, and nuclear reactor design in general, is improving the nuclear fuel utilization which is shown by attaining a higher burnup value. This study performed a preliminary neutronic design study of a 200 MWt OTTO cycle PBR with high burnup while fulfilling the safety criteria of the PBR design.The safety criteria of the design was represented by the per-fuel-pebble maximum power generation of 4.5 kW/pebble. The maximum burnup value was also limited by the tested maximum burnup value which maintained the integrity of the pebble fuel. Parametric surveys were performed to obtain the optimized parameters used in this study, which are the fuel enrichment, per-pebble heavy metal (HM) loading, and the average axial speed of the fuel. An optimum design with burnup value of 131.1 MWd/Kg-HM was achieved in this study which is much higher compare to the burnup of the reference design HTR-MODUL and a previously proposed OTTO-cycle PBR design. This optimum design uses 17% U-235 enrichment with 4 g HM-loading per fuel pebble. (author)

  6. Numerical Simulation of Particle Flow Motion in a Two-Dimensional Modular Pebble-Bed Reactor with Discrete Element Method

    Directory of Open Access Journals (Sweden)

    Guodong Liu

    2013-01-01

    Full Text Available Modular pebble-bed nuclear reactor (MPBNR technology is promising due to its attractive features such as high fuel performance and inherent safety. Particle motion of fuel and graphite pebbles is highly associated with the performance of pebbled-bed modular nuclear reactor. To understand the mechanism of pebble’s motion in the reactor, we numerically studied the influence of number ratio of fuel and graphite pebbles, funnel angle of the reactor, height of guide ring on the distribution of pebble position, and velocity by means of discrete element method (DEM in a two-dimensional MPBNR. Velocity distributions at different areas of the reactor as well as mixing characteristics of fuel and graphite pebbles were investigated. Both fuel and graphite pebbles moved downward, and a uniform motion was formed in the column zone, while pebbles motion in the cone zone was accelerated due to the decrease of the cross sectional flow area. The number ratio of fuel and graphite pebbles and the height of guide ring had a minor influence on the velocity distribution of pebbles, while the variation of funnel angle had an obvious impact on the velocity distribution. Simulated results agreed well with the work in the literature.

  7. Numerical simulation on friction coefficient effect of pebble flow dynamics in two-dimensional pebble-bed reactor

    International Nuclear Information System (INIS)

    In order to investigate the pebble flow dynamics in the high-temperature reactor core and based on the two-dimensional experiments of pebble flow dynamics, discrete element method (DEM) was used to simulate the pebble flow dynamics. The mean flow stream lines, standard deviation and the mean residence time of the pebble flow zone generated by markers were compared and analyzed. The results show that ball friction coefficient has little effect on the pebble flow field. With the pebble friction coefficient increasing, the horizontal diffusion of pebbles decreases and the pebble flow seems to be more uniform. The wall friction coefficient has little effect on the horizontal diffusion. While the wall friction coefficient increases, the flow tends to be more uneven. (authors)

  8. Some Movement Mechanisms and Characteristics in Pebble Bed Reactor

    Directory of Open Access Journals (Sweden)

    Xingtuan Yang

    2014-01-01

    Full Text Available The pebblebed-type high temperature gas-cooled reactor is considered to be one of the promising solutions for generation IV advanced reactors, and the two-region arranged reactor core can enhance its advantages by flattening neutron flux. However, this application is held back by the existence of mixing zone between central and peripheral regions, which results from pebbles’ dispersion motions. In this study, experiments have been carried out to study the dispersion phenomenon, and the variation of dispersion region and radial distribution of pebbles in the specifically shaped flow field are shown. Most importantly, the standard deviation of pebbles’ radial positions in dispersion region, as a quantitative index to describe the size of dispersion region, is gotten through statistical analysis. Besides, discrete element method has been utilized to analyze the parameter influence on dispersion region, and this practice offers some strategies to eliminate or reduce mixing zone in practical reactors.

  9. Gas Reactor International Cooperative Program: German Pebble Bed Reactor Technology review update

    International Nuclear Information System (INIS)

    This report provides a review of the German pebble bed reactor technology, and updates the information provided in the Gas Reactor International Cooperative Program Interim Report COO-4057-6, German Pebble Bed Reactor Design and Technology Review, dated September 1978. Most of the updated information is for the PNP-500 and the HHT-Prototype plants. The PNP-500 is a 500 MW(t) multi-purpose demonstration plant for coal conversion applications. The HHT-Prototype is a 1640 MWt reactor designed to produce 675 MWe of electricity using a direct cycle gas turbine. The report provides a description and evaluation of the overall plant and the nuclear reactor for both the PNP-500 and HHT-Prototype. A description and evaluation of the primary system components is presented for the process heat and gas turbine applications

  10. Numerical Simulation of Accident Scenario in High Temperature Gas Cooled (Pebble Bed) Nuclear Reactor

    Energy Technology Data Exchange (ETDEWEB)

    Peter, Geoffrey J. [Oregon Institute of Technology - Portland Center, Portland (United States)

    2012-03-15

    The accident scenario resulting from blockages due to the retention of dust in the coolant gas or from the rupture of one or more fuel particles used in the High Temperature Gas Cooled (Pebble Bed) Nuclear Reactors is considered in this paper. The next generation of Advanced High Temperature Reactors (AHTR), are considered for nuclear power production, and for high-temperature hydrogen production using nuclear reactors to reduce the carbon footprint. Blockages can cause LOCA variations in flow and heat transfer that may lead to hot spots within the bed that could compromise reactor safety. Therefore, it is important to know the void fraction distribution and the interstitial velocity field in the packed bed. The blockage for this numerical study simulated a region with significantly lower void than that in the rest of the bed. Finite difference technique solved the simplified continuity, momentum, and energy equations. Any meaningful outcome of the solution depended largely upon the validity of the boundary conditions. Among them, the inlet and outlet velocity profiles required special attention. Thus, a close approximation to these profiles obtained from an experimental set-up established the boundary conditions. This paper presents the development of the elliptic-partial equation for a bed of a bed of pebbles, and the solution procedure. The paper also discusses velocity and temperature profiles obtained from both numerical and experimental set-up, with and without effect of blockage. Based on the studies it is evident that knowledge of LOCA velocity and temperature distribution within the fuel element in a Pebble Bed Nuclear Reactor or AHTR is essential for reactor safety.

  11. Medium voltage direct current (MVDC) converter for pebble bed modular reactor (PBMR) / Hendrik de Villiers Pretorius

    OpenAIRE

    Pretorius, Hendrik de Villiers

    2004-01-01

    Nuclear and renewable energy systems will probably be used more and more extensively in future due to high environmental demands regarding pollution and exhaustion of the world's gas and coal reserves. Because most types of renewable energy systems do not supply electric power at line frequency and voltage a converter is used to connect these sources to the existing power system. The Pebble Bed Modular Reactor (PBMR) is a nuclear power plant currently using a 50 Hz synchrono...

  12. Modular Pebble-Bed Reactor Project: Laboratory-Directed Research and Development Program FY 2002 Annual Report

    Energy Technology Data Exchange (ETDEWEB)

    Petti, David Andrew; Dolan, Thomas James; Miller, Gregory Kent; Moore, Richard Leroy; Terry, William Knox; Ougouag, Abderrafi Mohammed-El-Ami; Oh, Chang H; Gougar, Hans D

    2002-11-01

    This report documents the results of our research in FY-02 on pebble-bed reactor technology under our Laboratory Directed Research and Development (LDRD) project entitled the Modular Pebble-Bed Reactor. The MPBR is an advanced reactor concept that can meet the energy and environmental needs of future generations under DOE’s Generation IV initiative. Our work is focused in three areas: neutronics, core design and fuel cycle; reactor safety and thermal hydraulics; and fuel performance.

  13. HTR-PROTEUS Pebble Bed Experimental Program Cores 1, 1A, 2, and 3: Hexagonal Close Packing with a 1:2 Moderator-to-Fuel Pebble Ratio

    Energy Technology Data Exchange (ETDEWEB)

    John D. Bess; Barbara H. Dolphin; James W. Sterbentz; Luka Snoj; Igor Lengar; Oliver Köberl

    2012-03-01

    In its deployment as a pebble bed reactor (PBR) critical facility from 1992 to 1996, the PROTEUS facility was designated as HTR-PROTEUS. This experimental program was performed as part of an International Atomic Energy Agency (IAEA) Coordinated Research Project (CRP) on the Validation of Safety Related Physics Calculations for Low Enriched HTGRs. Within this project, critical experiments were conducted for graphite moderated LEU systems to determine core reactivity, flux and power profiles, reaction-rate ratios, the worth of control rods, both in-core and reflector based, the worth of burnable poisons, kinetic parameters, and the effects of moisture ingress on these parameters. Four benchmark experiments were evaluated in this report: Cores 1, 1A, 2, and 3. These core configurations represent the hexagonal close packing (HCP) configurations of the HTR-PROTEUS experiment with a moderator-to-fuel pebble ratio of 1:2. Core 1 represents the only configuration utilizing ZEBRA control rods. Cores 1A, 2, and 3 use withdrawable, hollow, stainless steel control rods. Cores 1 and 1A are similar except for the use of different control rods; Core 1A also has one less layer of pebbles (21 layers instead of 22). Core 2 retains the first 16 layers of pebbles from Cores 1 and 1A and has 16 layers of moderator pebbles stacked above the fueled layers. Core 3 retains the first 17 layers of pebbles but has polyethylene rods inserted between pebbles to simulate water ingress. The additional partial pebble layer (layer 18) for Core 3 was not included as it was used for core operations and not the reported critical configuration. Cores 1, 1A, 2, and 3 were determined to be acceptable benchmark experiments.

  14. HTR-PROTEUS Pebble Bed Experimental Program Cores 1, 1A, 2, and 3: Hexagonal Close Packing with a 1:2 Moderator-to-Fuel Pebble Ratio

    Energy Technology Data Exchange (ETDEWEB)

    John D. Bess; Barbara H. Dolphin; James W. Sterbentz; Luka Snoj; Igor Lengar; Oliver Köberl

    2013-03-01

    In its deployment as a pebble bed reactor (PBR) critical facility from 1992 to 1996, the PROTEUS facility was designated as HTR-PROTEUS. This experimental program was performed as part of an International Atomic Energy Agency (IAEA) Coordinated Research Project (CRP) on the Validation of Safety Related Physics Calculations for Low Enriched HTGRs. Within this project, critical experiments were conducted for graphite moderated LEU systems to determine core reactivity, flux and power profiles, reaction-rate ratios, the worth of control rods, both in-core and reflector based, the worth of burnable poisons, kinetic parameters, and the effects of moisture ingress on these parameters. Four benchmark experiments were evaluated in this report: Cores 1, 1A, 2, and 3. These core configurations represent the hexagonal close packing (HCP) configurations of the HTR-PROTEUS experiment with a moderator-to-fuel pebble ratio of 1:2. Core 1 represents the only configuration utilizing ZEBRA control rods. Cores 1A, 2, and 3 use withdrawable, hollow, stainless steel control rods. Cores 1 and 1A are similar except for the use of different control rods; Core 1A also has one less layer of pebbles (21 layers instead of 22). Core 2 retains the first 16 layers of pebbles from Cores 1 and 1A and has 16 layers of moderator pebbles stacked above the fueled layers. Core 3 retains the first 17 layers of pebbles but has polyethylene rods inserted between pebbles to simulate water ingress. The additional partial pebble layer (layer 18) for Core 3 was not included as it was used for core operations and not the reported critical configuration. Cores 1, 1A, 2, and 3 were determined to be acceptable benchmark experiments.

  15. Development and testing of analytical models for the pebble bed type HTRs

    International Nuclear Information System (INIS)

    The pebble bed type gas cooled high temperature reactor (HTR) appears to be a good candidate for the next generation nuclear reactor technology. These reactors have unique characteristics in terms of the randomness in geometry, and require special techniques to analyze their systems. This study includes activities concerning the testing of computational tools and the qualification of models. Indeed, it is essential that the validated analytical tools be available to the research community. From this viewpoint codes like MCNP, ORIGEN and RELAP5, which have been used in nuclear industry for many years, are selected to identify and develop new capabilities needed to support HTR analysis. The geometrical model of the full reactor is obtained by using lattice and universe facilities provided by MCNP. The coupled MCNP-ORIGEN code is used to estimate the burnup and the refuelling scheme. Results obtained from Monte Carlo analysis are interfaced with RELAP5 to analyze the thermal hydraulics and safety characteristics of the reactor. New models and methodologies are developed for several past and present experimental and prototypical facilities that were based on HTR pebble bed concepts. The calculated results are compared with available experimental data and theoretical evaluations showing very good agreement. The ultimate goal of the validation of the computer codes for pebble bed HTR applications is to acquire and reinforce the capability of these general purpose computer codes for performing HTR core design and optimization studies

  16. Advanced Core Design And Fuel Management For Pebble-Bed Reactors

    Energy Technology Data Exchange (ETDEWEB)

    Hans D. Gougar; Abderrafi M. Ougouag; William K. Terry

    2004-10-01

    A method for designing and optimizing recirculating pebble-bed reactor cores is presented. At the heart of the method is a new reactor physics computer code, PEBBED, which accurately and efficiently computes the neutronic and material properties of the asymptotic (equilibrium) fuel cycle. This core state is shown to be unique for a given core geometry, power level, discharge burnup, and fuel circulation policy. Fuel circulation in the pebble-bed can be described in terms of a few well?defined parameters and expressed as a recirculation matrix. The implementation of a few heat?transfer relations suitable for high-temperature gas-cooled reactors allows for the rapid estimation of thermal properties critical for safe operation. Thus, modeling and design optimization of a given pebble-bed core can be performed quickly and efficiently via the manipulation of a limited number key parameters. Automation of the optimization process is achieved by manipulation of these parameters using a genetic algorithm. The end result is an economical, passively safe, proliferation-resistant nuclear power plant.

  17. A simulation of a pebble bed reactor core by the MCNP-4C computer code

    Directory of Open Access Journals (Sweden)

    Bakhshayesh Moshkbar Khalil

    2009-01-01

    Full Text Available Lack of energy is a major crisis of our century; the irregular increase of fossil fuel costs has forced us to search for novel, cheaper, and safer sources of energy. Pebble bed reactors - an advanced new generation of reactors with specific advantages in safety and cost - might turn out to be the desired candidate for the role. The calculation of the critical height of a pebble bed reactor at room temperature, while using the MCNP-4C computer code, is the main goal of this paper. In order to reduce the MCNP computing time compared to the previously proposed schemes, we have devised a new simulation scheme. Different arrangements of kernels in fuel pebble simulations were investigated and the best arrangement to decrease the MCNP execution time (while keeping the accuracy of the results, chosen. The neutron flux distribution and control rods worth, as well as their shadowing effects, have also been considered in this paper. All calculations done for the HTR-10 reactor core are in good agreement with experimental results.

  18. Computational prediction of dust production in graphite moderated pebble bed reactors

    Science.gov (United States)

    Rostamian, Maziar

    The scope of the work reported here, which is the computational study of graphite wear behavior, supports the Nuclear Engineering University Programs project "Experimental Study and Computational Simulations of Key Pebble Bed Thermomechanics Issues for Design and Safety" funded by the US Department of Energy. In this work, modeling and simulating the contact mechanics, as anticipated in a PBR configuration, is carried out for the purpose of assessing the amount of dust generated during a full power operation year of a PBR. A methodology that encompasses finite element analysis (FEA) and micromechanics of wear is developed to address the issue of dust production and its quantification. Particularly, the phenomenon of wear and change of its rate with sliding length is the main focus of this dissertation. This work studies the wear properties of graphite by simulating pebble motion and interactions of a specific type of nuclear grade graphite, IG-11. This study consists of two perspectives: macroscale stress analysis and microscale analysis of wear mechanisms. The first is a set of FEA simulations considering pebble-pebble frictional contact. In these simulations, the mass of generated graphite particulates due to frictional contact is calculated by incorporating FEA results into Archard's equation, which is a linear correlation between wear mass and wear length. However, the experimental data by Johnson, University of Idaho, revealed that the wear rate of graphite decreases with sliding length. This is because the surfaces of the graphite pebbles become smoother over time, which results in a gradual decrease in wear rate. In order to address the change in wear rate, a more detailed analysis of wear mechanisms at room temperature is presented. In this microscale study, the wear behavior of graphite at the asperity level is studied by simulating the contact between asperities of facing surfaces. By introducing the effect of asperity removal on wear rate, a nonlinear

  19. Interim report on core physics and fuel cycle analysis of the pebble bed reactor power plant concept

    International Nuclear Information System (INIS)

    Calculations were made to predict the performance of a pebble bed reactor operated in a mode to produce fissile fuel (high conversion or breeding). Both a one pebble design and a design involving large primary feed pebbles and small fertile pebbles were considered. A relatively short residence time of the primary pebbles loaded with 233U fuel was found to be necessary to achieve a high breeding ratio, but this leads to relatively high fuel costs. A high fissile inventory is associated with a low C/Th ratio and a high thorium loading, causing the doubling time to be long, even though the breeding ratio is high, and the fuel cost of electrical product to be high. Production of 233U fuel from 235U feed was studied and performances of the converter and breeder reactor concepts were examined varying the key parameters

  20. HTR-PROTEUS PEBBLE BED EXPERIMENTAL PROGRAM CORE 4: RANDOM PACKING WITH A 1:1 MODERATOR-TO-FUEL PEBBLE RATIO

    Energy Technology Data Exchange (ETDEWEB)

    John D. Bess; Leland M. Montierth

    2013-03-01

    In its deployment as a pebble bed reactor (PBR) critical facility from 1992 to 1996, the PROTEUS facility was designated as HTR-PROTEUS. This experimental program was performed as part of an International Atomic Energy Agency (IAEA) Coordinated Research Project (CRP) on the Validation of Safety Related Physics Calculations for Low Enriched HTGRs. Within this project, critical experiments were conducted for graphite moderated LEU systems to determine core reactivity, flux and power profiles, reaction-rate ratios, the worth of control rods, both in-core and reflector based, the worth of burnable poisons, kinetic parameters, and the effects of moisture ingress on these parameters. One benchmark experiment was evaluated in this report: Core 4. Core 4 represents the only configuration with random pebble packing in the HTR-PROTEUS series of experiments, and has a moderator-to-fuel pebble ratio of 1:1. Three random configurations were performed. The initial configuration, Core 4.1, was rejected because the method for pebble loading, separate delivery tubes for the moderator and fuel pebbles, may not have been completely random; this core loading was rejected by the experimenters. Cores 4.2 and 4.3 were loaded using a single delivery tube, eliminating the possibility for systematic ordering effects. The second and third cores differed slightly in the quantity of pebbles loaded (40 each of moderator and fuel pebbles), stacked height of the pebbles in the core cavity (0.02 m), withdrawn distance of the stainless steel control rods (20 mm), and withdrawn distance of the autorod (30 mm). The 34 coolant channels in the upper axial reflector and the 33 coolant channels in the lower axial reflector were open. Additionally, the axial graphite fillers used in all other HTR-PROTEUS configurations to create a 12-sided core cavity were not used in the randomly packed cores. Instead, graphite fillers were placed on the cavity floor, creating a funnel-like base, to discourage ordering

  1. HTR-PROTEUS PEBBLE BED EXPERIMENTAL PROGRAM CORE 4: RANDOM PACKING WITH A 1:1 MODERATOR-TO-FUEL PEBBLE RATIO

    Energy Technology Data Exchange (ETDEWEB)

    John D. Bess; Leland M. Montierth

    2014-03-01

    In its deployment as a pebble bed reactor (PBR) critical facility from 1992 to 1996, the PROTEUS facility was designated as HTR-PROTEUS. This experimental program was performed as part of an International Atomic Energy Agency (IAEA) Coordinated Research Project (CRP) on the Validation of Safety Related Physics Calculations for Low Enriched HTGRs. Within this project, critical experiments were conducted for graphite moderated LEU systems to determine core reactivity, flux and power profiles, reaction-rate ratios, the worth of control rods, both in-core and reflector based, the worth of burnable poisons, kinetic parameters, and the effects of moisture ingress on these parameters. One benchmark experiment was evaluated in this report: Core 4. Core 4 represents the only configuration with random pebble packing in the HTR-PROTEUS series of experiments, and has a moderator-to-fuel pebble ratio of 1:1. Three random configurations were performed. The initial configuration, Core 4.1, was rejected because the method for pebble loading, separate delivery tubes for the moderator and fuel pebbles, may not have been completely random; this core loading was rejected by the experimenters. Cores 4.2 and 4.3 were loaded using a single delivery tube, eliminating the possibility for systematic ordering effects. The second and third cores differed slightly in the quantity of pebbles loaded (40 each of moderator and fuel pebbles), stacked height of the pebbles in the core cavity (0.02 m), withdrawn distance of the stainless steel control rods (20 mm), and withdrawn distance of the autorod (30 mm). The 34 coolant channels in the upper axial reflector and the 33 coolant channels in the lower axial reflector were open. Additionally, the axial graphite fillers used in all other HTR-PROTEUS configurations to create a 12-sided core cavity were not used in the randomly packed cores. Instead, graphite fillers were placed on the cavity floor, creating a funnel-like base, to discourage ordering

  2. Potential and limitations in maximizing the power output of an inherent safe modular pebble bed HTGR

    International Nuclear Information System (INIS)

    The past development of modular pebble-bed HTGRs in Germany led to two well-defined reactor designs, namely the 200 MWth HTR-MODUL and the 250 MWth HTR-100 by SIEMENS/Interatom and ABB/HRB, respectively. Recently the South African utility, ESKOM, decided to include the pebble-bed HTGR design as a future supply option. In contrast to the German designs, ESKOM prefers a direct cycle helium turbine system on the power conversion side. This imposes certain modified boundary conditions on the reactor design and enables a higher plant efficiency. Nuclear and thermal-hydraulic investigations have been performed at KFA-ISR to determine the potential and limitations of increasing the unit thermal power output of the reactor compared to the former german designs. In doing so an upper limit for the maximum fuel element temperature of 1600 deg. C was observed. The impact of all modifications in view onto the efficiency of the nuclear control and shut-down systems was also considered. The results obtained so far demonstrate the well-adapted and conservative design of the SIEMENS HTR-MODUL within a 10% safety margin to the higher region. The introduction of graphite noses has a remarkably positive influence on the shut-down and control systems, while the positive effect on the maximum accident temperature depends strongly on the fast neutron dose-related thermal conductivity of the nose graphite. Considering the fact that effective conductivity of the pebble-bed core is maintained at high temperatures, the temperature effect due to the noses are of secondary influence at this point. (author)

  3. On-line interrogation of pebble bed reactor fuel using passive gamma-ray spectrometry

    Science.gov (United States)

    Chen, Jianwei

    The Pebble Bed Reactor (PBR) is a helium-cooled, graphite-moderated high temperature nuclear power reactor. In addition to its inherently safe design, a unique feature of this reactor is its multipass fuel cycle in which graphite fuel pebbles (of varying enrichment) are randomly loaded and continuously circulated through the core until they reach their prescribed end-of-life burnup limit (˜80,000--100,000 MWD/MTU). Unlike the situation with conventional light water reactors (LWRs), depending solely on computational methods to perform in-core fuel management will be highly inaccurate. As a result, an on-line measurement approach becomes the only accurate method to assess whether a particular pebble has reached its end-of-life burnup limit. In this work, an investigation was performed to assess the feasibility of passive gamma-ray spectrometry assay as an approach for on-line interrogation of PBR fuel for the simultaneous determination of burnup and enrichment on a pebble-by-pebble basis. Due to the unavailability of irradiated or fresh pebbles, Monte Carlo simulations were used to study the gamma-ray spectra of the PBR fuel at various levels of burnup. A pebble depletion calculation was performed using the ORIGEN code, which yielded the gamma-ray source term that was introduced into the input of an MCNP simulation. The MCNP simulation assumed the use of a high-purity coaxial germanium detector. Due to the lack of one-group high temperature reactor cross sections for ORIGEN, a heterogeneous MCNP model was developed to describe a typical PBR core. Subsequently, the code MONTEBURNS was used to couple the MCNP model and ORIGEN. This approach allowed the development of the burnup-dependent, one-group spectral-averaged PBR cross sections to be used in the ORIGEN pebble depletion calculation. Based on the above studies, a relative approach for performing the measurements was established. The approach is based on using the relative activities of Np-239/I-132 in combination

  4. Numerical analysis of dynamic behavior of HTR pebble-bed core and comparison with test results

    International Nuclear Information System (INIS)

    The behavior under seismic loading of the pebble bed core of a high temperature reactor is the objective of the investigation reported here. The paper describes the constitutive modelling of the assembly of spheres comprising the core and the finite element simulation of shaking table tests conducted on a one-sixth physical model of the core of a proposed new medium-sized HTR power plant. The analytical studies and the shaking table tests have been performed with the aim of gaining a fundamental understanding of the dynamic behavior of such core material and validating numerical models

  5. The pebble bed high temperature reactor as a source of nuclear process heat. Vol. 2

    International Nuclear Information System (INIS)

    A theoretical analysis is given for a series of 8 different variants of the pebble-bed reactor in the 'once through' fuel management scheme. The comparison gives some insight into the parametric sensitivities and into the development potential of this type. The thorium/U-233 recycling fuel cycle allows to increase the conversion ratio up to the range between 0.90 and 0.95. The feasibility for a changeover between different fuel cycles under full power operation. - The study is complemented by a review of the relevant previous investigations. (orig.)

  6. Preparation and characterization of Li{sub 4}SiO{sub 4} ceramic pebbles by graphite bed method

    Energy Technology Data Exchange (ETDEWEB)

    Hong, Ming; Zhang, Yingchun, E-mail: zycustb@163.com; Xiang, Maoqiao; Liu, Zhiang

    2015-06-15

    Highlights: • Lithium orthosilicate pebbles were fabricated by a new graphite bed process. • Two routes using different raw materials have been conducted in this work. • The fabricated pebbles exhibit a high relative density with uniform microstructure. • This method is short and simple as the pebbles could be fabricated in a continuous process. - Abstract: Lithium-based ceramics have long been recognized as tritium breeding materials in fusion reactor blankets. Lithium orthosilicate (Li{sub 4}SiO{sub 4}) is one of these materials and has been recommended by many ITER research teams as the first selection for the solid tritium breeder. In this paper, the fabrication of Li{sub 4}SiO{sub 4} pebbles used as tritium breeder by a graphite bed method was studied for the first time. Ceramic powders and deionized water were mixed and ball milled to obtain homogeneous suspensions. And then the ceramic suspensions were dispersed on spread graphite powder through nozzles. Spherical droplets with highly uniform size were formed by the surface tension of the liquid droplets. The droplets converted into green pebbles after drying. After calcination and sintering, Li{sub 4}SiO{sub 4} pebbles with desired size and shape were prepared. The obtained Li{sub 4}SiO{sub 4} pebbles had narrow size distribution and favorable sphericity. Thermal analysis, phase analysis and microstructure observation of the pebbles were carried out systematically. Properties of the prepared pebbles were also characterized for crushing load strength, density and porosity, etc. The values were found to be conforming to the desired properties for used as solid breeder.

  7. Very High Temperature Reactor (VHTR) Deep Burn Core and Fuel Analysis -- Complete Design Selection for the Pebble Bed Reactor

    Energy Technology Data Exchange (ETDEWEB)

    B. Boer; A. M. Ougouag

    2010-09-01

    The Deep-Burn (DB) concept focuses on the destruction of transuranic nuclides from used light water reactor fuel. These transuranic nuclides are incorporated into TRISO coated fuel particles and used in gas-cooled reactors with the aim of a fractional fuel burnup of 60 to 70% in fissions per initial metal atom (FIMA). This high performance is expected through the use of multiple recirculation passes of the fuel in pebble form without any physical or chemical changes between passes. In particular, the concept does not call for reprocessing of the fuel between passes. In principle, the DB pebble bed concept employs the same reactor designs as the presently envisioned low-enriched uranium core designs, such as the 400 MWth Pebble Bed Modular Reactor (PBMR-400). Although it has been shown in the previous Fiscal Year (2009) that a PuO2 fueled pebble bed reactor concept is viable, achieving a high fuel burnup, while remaining within safety-imposed prescribed operational limits for fuel temperature, power peaking and temperature reactivity feedback coefficients for the entire temperature range, is challenging. The presence of the isotopes 239-Pu, 240-Pu and 241-Pu that have resonances in the thermal energy range significantly modifies the neutron thermal energy spectrum as compared to a ”standard,” UO2-fueled core. Therefore, the DB pebble bed core exhibits a relatively hard neutron energy spectrum. However, regions within the pebble bed that are near the graphite reflectors experience a locally softer spectrum. This can lead to power and temperature peaking in these regions. Furthermore, a shift of the thermal energy spectrum with increasing temperature can lead to increased absorption in the resonances of the fissile Pu isotopes. This can lead to a positive temperature reactivity coefficient for the graphite moderator under certain operating conditions. The effort of this task in FY 2010 has focused on the optimization of the core to maximize the pebble discharge

  8. Analysis of Fluid Flow and Heat Transfer Model for the Pebble Bed High Temperature Gas Cooled Reactor

    Directory of Open Access Journals (Sweden)

    S. Yamoah

    2012-06-01

    Full Text Available The pebble bed type high temperature gas cooled nuclear reactor is a promising option for next generation reactor technology and has the potential to provide high efficiency and cost effective electricity generation. The reactor unit heat transfer poses a challenge due to the complexity associated with the thermalflow design. Therefore to reliably simulate the flow and heat transport of the pebble bed modular reactor necessitates a heat transfer model that deals with radiation as well as thermal convection and conduction. In this study, a model with the capability to simulate fluid flow and heat transfer in the pebble bed modular reactor core has been developed. The developed model was implemented on a personal computer using FORTRAN 95 programming language. Several important fluid flow and heat transfer parameters have been examined: including the pressure drop over the reactor core, the heat transfer coefficient, the Nusselt number and the effective thermal conductivity of the fuel pebbles. Results obtained from the simulation experiments show a uniform pressure in the radial direction for a core to fuel element diameter (D/d ratio>20 and the heat transfer coefficient increases with increasing temperature and coolant mass flow rate. The model can adequately account for the flow and heat transfer phenomenon and the loss of pressure through friction in the pebble bed type high temperature nuclear reactor.

  9. Conceptual design study of Pebble Bed Type High Temperature Gas-cooled Reactor with annular core structure

    International Nuclear Information System (INIS)

    This report presents the Conceptual Design Study of Pebble Bed Type High Temperature Gas-cooled Reactor with Annular Core Structure. From this study, it is made clear that the thermal power of the Pebble Bed Type Reactor can be increased to 500MW through introducing the annular core structure without losing the inherent safe characteristics (in the coolant depressurization accident, the fuel temperature does not exceed the temperature where the fuel defect begins.) This thermal power is two times higher than the inherent safe Pebble Bed Type High temperature Gas-cooled Reactor (MHTGR) designed in West Germany. From this result, it is foreseen that the ratio of the plant cost to the reactor power is reduced and the economy of the plant operation is improved. The reactor performances e.g. fuel burnup and fuel temperature are maintained in same level of the MHTGR. (author)

  10. Dynamics and transient stability of a pebble bed reactor during start up

    Energy Technology Data Exchange (ETDEWEB)

    Miles, B.; Pain, C.C.; Eaton, M.D.; Ziver, A.K.; Goddard, A.J.H. [Applied Modelling and Computation Group, Imperial College of Science, Technology and Medicine, Dept. of Earth Science and Engineering, London (United Kingdom); Oliveira, C.R.E. de [Nuclear and Radiological Engineering and Medical Physics Program, The George W Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA (United States)

    2005-07-01

    A design of a modular pebble bed reactor (PBR) is being developed for construction in South Africa. The design of this PBR is simulated in the FETCH nuclear criticality model. FETCH solves the neutron transport equations coupled to fluid dynamics and has been used in simulations of fluidized bed reactors. In the neutronics module of FETCH steady state neutronic calculations are performed to obtain the starting conditions for the subsequent calculation of transient behaviour. These include fuel temperature and control rod position. Neutron flux and the initial surplus reactivity are also calculated. Each step change in a simulated start-up is initiated by an excess reactivity which produces more severe transients than would be encountered in normal operation. The variations of several parameters with time are recorded, for example, temperature at various points in the reactor, temperature of the hottest pebble and fission rate. Spatial profiles are recorded at regular time intervals, including temperatures, power density, gas velocity and gas pressure. The stability of the reactor is demonstrated.

  11. Feasibility of Thorium Fuel Cycles in a Very High Temperature Pebble-Bed Hybrid System

    Directory of Open Access Journals (Sweden)

    L.P. Rodriguez

    2015-08-01

    Full Text Available Nuclear energy presents key challenges to be successful as a sustainable energy source. Currently, the viability of the use thorium-based fuel cycles in an innovative nuclear energy generation system is being investigated in order to solve these key challenges. In this work, the feasibility of three thorium-based fuel cycles (232Th-233U, 232Th-239Pu, and 232Th-U in a hybrid system formed by a Very High Temperature Pebble-Bed Reactor (VHTR and two Pebble-Bed Accelerator Driven Systems (ADSs was evaluated using parameters related to the neutronic behavior such as nuclear fuel breeding, minor actinide stockpile, the energetic contribution of each fissile isotope, and the radiotoxicity of the long lived wastes. These parameters were used to compare the fuel cycles using the well-known MCNPX ver. 2.6e computational code. The results obtained confirm that the 232Th-233U fuel cycle is the best cycle for minimizing the production of plutonium isotopes and minor actinides. Moreover, the inclusion of the second stage in the ADSs demonstrated the possibility of extending the burnup cycle duration and reducing the radiotoxicity of the discharged fuel from the VHTR.

  12. Modular pebble-bed reactor reforming plant design for process heat

    International Nuclear Information System (INIS)

    This report describes a preliminary design study of a Modular Pebble-Bed Reactor System Reforming (MPB-R) Plant. The system uses one pressure vessel for the reactor and a second pressure vessel for the components, i.e., reformer, steam generator and coolant circulator. The two vessels are connected by coaxial pipes in an arrangement known as the side-by-side (SBS). The goal of the study is to gain an understanding of this particular system and to identify any technical issues that must be resolved for its application to a modular reformer plant. The basic conditions for the MPB-R were selected in common with those of the current study of the MRS-R in-line prismatic fuel concept, specifically, the module core power of 250 MWt, average core power density of 4.1 w/cc, low enriched uranium (LEU) fuel with a 235U content of 20% homogeneously mixed with thorium, and a target burnup of 80,000 MWD/MT. Study results include the pebble-bed core neutronics and thermal-hydraulic calculations. Core characteristics for both the once-through-then-out (OTTO) and recirculation of fuel sphere refueling schemes were developed. The plant heat balance was calculated with 55% of core power allotted to the reformer

  13. Autonomous multi-purpose floating power system with a compact static pebble bed reactor

    Energy Technology Data Exchange (ETDEWEB)

    Tsvetkov, Pavel; Vierow, Karen; Peddicord, Kenneth; Ragusa, Jean; McDeavitt, Sean; Poston, John Sr.; Shao, Lin; Willems, Greg [Department of Nuclear Engineering, Texas A and M University, College Station, Texas (United States)

    2008-07-01

    The paper introduces a new concept of an autonomous multipurpose system with a compact static-bed pebble bed reactor as a power source. The system is envisioned as a small floating power complex in which a compact high-efficiency nuclear system provides the source of energy for a variety of industrial processes. It offers the near-term (with a conventional power source) and long-term (with a compact high-efficiency nuclear system) technologies for a low cost electricity/potable water supply compared to traditional systems for regions where local communities are isolated and do not have extensive industrial infrastructure and distribution networks. The complex can be quickly installed anywhere following demands and needs of local communities - coastal regions and islands. The reactor design and system layout, balance-of-plant evaluations, performance characteristics and deployment strategies are discussed. (authors)

  14. Simplified models for pebble-bed HTR core burn-up calculations with Monteburns2.0©

    International Nuclear Information System (INIS)

    Highlights: ► PBMR-400 annular core is very difficult to simulate in a reliable way. ► Nuclide evolutions given by different lattice models can differ significantly. ► To split fixed lattice models into two axial zones does not affect results significantly. ► We can choose a (simplified) core model on the basis of the analysis aim. ► Monteburns gives by survey burn-up calculations reasonable nuclide evolution trends. - Abstract: This paper aims at comparing some simplified models to simulate irradiation cycles of Pu fuelled pebble-bed reactors with Monteburns2.0© code. As a reference core, the PBMR-400 (proposed in the framework of the EU PUMA project, where this kind of core fuelled by a Pu and Pu–Np fuel has been studied) was taken into account. Pebble-bed High Temperature Reactor (HTR) cores consist of hundreds of thousands pebbles arranged stochastically in a cylindrical or annular space and each pebble is a single fuel element, and it is able to reach ultra-high burn-ups, i.e. up to 750 GWd/tHM (for Pu-based fuels). Additionally, pebble-bed cores are characterised by a continuous recirculation of pebbles from the top to the bottom of the core. Modelling accurately with current computer codes such an arrangement, in order to predict the behaviour of the core itself, is a very difficult task and any depletion code specifically devoted to pebble-bed burn-up calculation is not available at the moment. Because of limitations of the most common current MCNP-based depletion codes as well as huge calculation times, simplified models have to be implemented. After an analysis of the literature available on pebble-bed models for criticality and burn-up calculations, a preliminary assessment of the impact of different kind of simplified models for a Pu-Np fuelled Pebble-Bed Modular Reactor (PBMR), proposed in the framework of the EU PUMA project, is shown, particularly as far as burn-up prediction with Monteburns2.0© code is concerned.

  15. Characteristics of convective heat transport in a packed pebble-bed reactor

    International Nuclear Information System (INIS)

    Highlights: • A fast-response heat transfer probe has been developed and used in this work. • Heat transport has been quantified in terms of local heat transfer coefficients. • The method of the electrically heated single sphere in packing has been applied. • The heat transfer coefficient increases from the center to the wall of packed bed. • This work advancing the knowledge of heat transport in the studied packed bed. - Abstract: Obtaining more precise results and a better understanding of the heat transport mechanism in the dynamic core of packed pebble-bed reactors is needed because this mechanism poses extreme challenges to the reliable design and efficient operation of these reactors. This mechanism can be quantified in terms of a solid-to-gas convective heat transfer coefficient. Therefore, in this work, the local convective heat transfer coefficients and their radial profiles were measured experimentally in a separate effect pilot-plant scale and cold-flow experimental setup of 0.3 m in diameter, using a sophisticated noninvasive heat transfer probe of spherical type. The effect of gas velocity on the heat transfer coefficient was investigated over a wide range of Reynolds numbers of practical importance. The experimental investigations of this work include various radial locations along the height of the bed. It was found that an increase in coolant gas flow velocity causes an increase in the heat transfer coefficient and that effect of the gas flow rate varies from laminar to turbulent flow regimes at all radial positions of the studied packed pebble-bed reactor. The results show that the local heat transfer coefficient increases from the bed center to the wall due to the change in the bed structure, and hence, in the flow pattern of the coolant gas. The findings clearly indicate that one value of an overall heat transfer coefficient cannot represent the local heat transfer coefficients within the bed; therefore, correlations are needed to

  16. Plutonium and minor actinide utilisation in a pebble-bed high temperature reactor

    International Nuclear Information System (INIS)

    This paper contains results of the analysis of the pebble-bed high temperature gas-cooled PUMA reactor loaded with plutonium and minor actinide (Pu/MA) fuel. Starting from knowledge and experience gained in the Euratom FP5 projects HTR-N and HTR-N1, this study aims at demonstrating the potential of high temperature reactors to utilize or transmute Pu/MA fuel. The work has been performed within the Euratom FP6 project PUMA. A number of different fuel types and fuel configurations have been analyzed and compared with respect to incineration performance and safety-related reactor parameters. The results show the excellent plutonium and minor actinide burning capabilities of the high temperature reactor. The largest degree of incineration is attained in the case of an HTR fuelled by pure plutonium fuel as it remains critical at very deep burnup of the discharged pebbles. Addition of minor actinides to the fuel leads to decrease of the achievable discharge burnup and therefore smaller fraction of actinides incinerated during reactor operation. The inert-matrix fuel design improves the transmutation performance of the reactor, while the 'wallpaper' fuel does not have advantage over the standard fuel design in this respect. After 100 years of decay following the fuel discharge, the total amount of actinides remains almost unchanged for all of the fuel types considered. Among the plutonium isotopes, only the amount of Pu-241 is reduced significantly due to its relatively short half-life. (authors)

  17. Plutonium and minor actinide utilisation in a pebble-bed high temperature reactor

    Energy Technology Data Exchange (ETDEWEB)

    Petrov, B. Y.; Kuijper, J. C.; Oppe, J.; De Haas, J. B. M. [Nuclear Research and Consultancy Group, Westerduinweg 3, 1755 ZG Petten (Netherlands)

    2012-07-01

    This paper contains results of the analysis of the pebble-bed high temperature gas-cooled PUMA reactor loaded with plutonium and minor actinide (Pu/MA) fuel. Starting from knowledge and experience gained in the Euratom FP5 projects HTR-N and HTR-N1, this study aims at demonstrating the potential of high temperature reactors to utilize or transmute Pu/MA fuel. The work has been performed within the Euratom FP6 project PUMA. A number of different fuel types and fuel configurations have been analyzed and compared with respect to incineration performance and safety-related reactor parameters. The results show the excellent plutonium and minor actinide burning capabilities of the high temperature reactor. The largest degree of incineration is attained in the case of an HTR fuelled by pure plutonium fuel as it remains critical at very deep burnup of the discharged pebbles. Addition of minor actinides to the fuel leads to decrease of the achievable discharge burnup and therefore smaller fraction of actinides incinerated during reactor operation. The inert-matrix fuel design improves the transmutation performance of the reactor, while the 'wallpaper' fuel does not have advantage over the standard fuel design in this respect. After 100 years of decay following the fuel discharge, the total amount of actinides remains almost unchanged for all of the fuel types considered. Among the plutonium isotopes, only the amount of Pu-241 is reduced significantly due to its relatively short half-life. (authors)

  18. Pebble bed modular reactor safeguards: developing new approaches and implementing safeguards by design

    Energy Technology Data Exchange (ETDEWEB)

    Beyer, Brian David [Los Alamos National Laboratory; Beddingfield, David H [Los Alamos National Laboratory; Durst, Philip [INL; Bean, Robert [INL

    2010-01-01

    The design of the Pebble Bed Modular Reactor (PBMR) does not fit or seem appropriate to the IAEA safeguards approach under the categories of light water reactor (LWR), on-load refueled reactor (OLR, i.e. CANDU), or Other (prismatic HTGR) because the fuel is in a bulk form, rather than discrete items. Because the nuclear fuel is a collection of nuclear material inserted in tennis-ball sized spheres containing structural and moderating material and a PBMR core will contain a bulk load on the order of 500,000 spheres, it could be classified as a 'Bulk-Fuel Reactor.' Hence, the IAEA should develop unique safeguards criteria. In a multi-lab DOE study, it was found that an optimized blend of: (i) developing techniques to verify the plutonium content in spent fuel pebbles, (ii) improving burn-up computer codes for PBMR spent fuel to provide better understanding of the core and spent fuel makeup, and (iii) utilizing bulk verification techniques for PBMR spent fuel storage bins should be combined with the historic IAEA and South African approaches of containment and surveillance to verify and maintain continuity of knowledge of PBMR fuel. For all of these techniques to work the design of the reactor will need to accommodate safeguards and material accountancy measures to a far greater extent than has thus far been the case. The implementation of Safeguards-by-Design as the PBMR design progresses provides an approach to meets these safeguards and accountancy needs.

  19. Safeguards Challenges for Pebble-Bed Reactors (PBRs):Peoples Republic of China (PRC)

    Energy Technology Data Exchange (ETDEWEB)

    Forsberg, Charles W. [Massachusetts Institute of Technology (MIT); Moses, David Lewis [ORNL

    2009-11-01

    The Peoples Republic of China (PRC) is operating the HTR-10 pebble-bed reactor (PBR) and is in the process of building a prototype PBR plant with two modular reactors (250-MW(t) per reactor) feeding steam to a single turbine-generator. It is likely to be the first modular hightemperature reactor to be ready for commercial deployment in the world because it is a highpriority project for the PRC. The plant design features multiple modular reactors feeding steam to a single turbine generator where the number of modules determines the plant output. The design and commercialization strategy are based on PRC strengths: (1) a rapidly growing electric market that will support low-cost mass production of modular reactor units and (2) a balance of plant system based on economics of scale that uses the same mass-produced turbine-generator systems used in PRC coal plants. If successful, in addition to supplying the PRC market, this strategy could enable China to be the leading exporter of nuclear reactors to developing countries. The modular characteristics of the reactor match much of the need elsewhere in the world. PBRs have major safety advantages and a radically different fuel. The fuel, not the plant systems, is the primary safety system to prevent and mitigate the release of radionuclides under accident conditions. The fuel consists of small (6-cm) pebbles (spheres) containing coatedparticle fuel in a graphitized carbon matrix. The fuel loading per pebble is small (~9 grams of low-enriched uranium) and hundreds of thousands of pebbles are required to fuel a nuclear plant. The uranium concentration in the fuel is an order of magnitude less than in traditional nuclear fuels. These characteristics make the fuel significantly less attractive for illicit use (weapons production or dirty bomb); but, its unusual physical form may require changes in the tools used for safeguards. This report describes PBRs, what is different, and the safeguards challenges. A series of

  20. High temperature gas-cooled pebble bed reactor steady state thermal-hydraulics analyses based on CFD method

    International Nuclear Information System (INIS)

    Background: Based on general purpose CFD code Fluent, the PBMR-400 full load nominal condition thermal-hydraulics performance was studied by applying local thermal non-equilibrium porous media model. Purpose: In thermal hydraulics study of the gas cooled pebble bed reactor, the core of the reactor can be treated as macroscopic porous media with strong inner heat source, and the original Fluent code can not handle it properly. Methods: By introducing a UDS in the calculation domain of the reactor core and subjoining a new resistance term, we develop a non-equilibrium porous media model which can give an accurate description of the core of the pebble bed. The mesh of CFD code is finer than that of the traditional pebble bed reactor thermal hydraulics analysis code such as THERMIX and TINTE, thus more information about coolant velocity fields, temperature field and solid phase temperature field can be acquired. Results: The nominal condition calculation results of the CFD code are compared to those of the well-established thermal-hydraulic code THERMIX and TINTE, and show a good consistency. Conclusion: The extended local thermal non-equilibrium model can be used to analyse thermal-hydraulics of high temperature pebble bed type reactor. (authors)

  1. Pebble Bed Reactor Plant screening evaluation. Volume 1. Overall plant and reactor system

    International Nuclear Information System (INIS)

    This report consists of three volumes which describe the design concepts and screening evaluation for a 3000 MW/sub t/ Pebble Bed Reactor Multiplex Plant (PBR-MX). The Multiplex plant produces both electricity and transportable chemical energy via the thermochemical pipeline (TCP). The evaluation was limited to a direct cycle plant which has the steam generators and steam reformers in the primary circuit. Volume 1 reports the overall plant and reactor system. Core scoping studies were performed which evaluated the effects of annular and cyclindrical core configurations, radial blanket zones, burnup, and ball heavy metal loadings. The reactor system, including the PCRV, was investigated for both the annular and cylindrical core configurations

  2. Storage built pebble bed for greenhouse use; Acumulador tipo lecho para uso en invernaderos

    Energy Technology Data Exchange (ETDEWEB)

    Bistoni, S.; Iriarte, A.; Saravia, L.

    2004-07-01

    To heat greenhouses during the night it is necessary to use storage systems. Our region shows high radiation levels, even in winter, so during the day stored energy inside of a greenhouse is more than necessary. If the excess of energy is stored up, it can be used during the night when it is necessary. In this paper the performance of a storage built with plastic bottles with water inside them are studied and it is compared with a pebble bed. A model and its solution using the electric- thermal analogy are presented. The results show that it is feasible and economic to build a storage like the proposed. It is important to mention that the simulation is very simple because of the computational program used. (Author)

  3. Simulation of the Pebble Bed Micro Model Benchmark Problem using MARS-GCR

    Energy Technology Data Exchange (ETDEWEB)

    Seo, Dong Un [Seoul National Univ., Seoul (Korea, Republic of); Bae, Sung Won; Lee, Won Jae [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2007-07-01

    The Pebble Bed Micro Model (PBMM) is a benchmark model of the Power Conversion Unit (PCU) to demonstrate the dynamic behavior of a three shafts power conversion system with nitrogen as a working fluid. This closed recuperative Brayton power conversion cycle is one of the viable options for the power conversion unit (PCU) of the very high temperature gas cooled reactor (VHTR). It is important for the safety analysis code to be able to accurately predict the behavior of the PCU. In order to obtain data for a validation of the safety analysis code, the MARS-GCR code, is applied to the steady state and mass injection test runs of the PBMM benchmark problem.

  4. Design of fuzzy PID controller for high temperature pebble bed reactor

    Energy Technology Data Exchange (ETDEWEB)

    Badgujar, Kushal D.; Satpute, Satchidanand R.; Revankara, Shripad T.; Lee, John C.; Kim, Moo Hwan [POSTECH, Pohang (Korea, Republic of)

    2012-10-15

    Control system is most important characteristic to be considered to control spontaneous fission reaction in the design of the nuclear reactor. Recently fuzzy based control systems have been designed and applied as control system for nuclear plants. This article emphasize on controlling the power of the high temperature pebble bed reactor (HTPBR) with the design of Fuzzy proportional integral derivative (PID) controller. A simplified reactor model with point kinetics equation and reactor heat balance equation is used. The reactivity feedback arising from power coefficient of reactivity and Xenon poisoning is also considered. The reactor is operated at various power levels by using fuzzy PID controller. The fuzzy logic eliminates the necessity of the tuning the gains of PID controller each time by extending the finite sets of the PID controller gains.

  5. Computational Model for the Neutronic Simulation of Pebble Bed Reactor’s Core Using MCNPX

    Directory of Open Access Journals (Sweden)

    J. Rosales

    2014-01-01

    Full Text Available Very high temperature reactor (VHTR designs offer promising performance characteristics; they can provide sustainable energy, improved proliferation resistance, inherent safety, and high temperature heat supply. These designs also promise operation to high burnup and large margins to fuel failure with excellent fission product retention via the TRISO fuel design. The pebble bed reactor (PBR is a design of gas cooled high temperature reactor, candidate for Generation IV of Nuclear Energy Systems. This paper describes the features of a detailed geometric computational model for PBR whole core analysis using the MCNPX code. The validation of the model was carried out using the HTR-10 benchmark. Results were compared with experimental data and calculations of other authors. In addition, sensitivity analysis of several parameters that could have influenced the results and the accuracy of model was made.

  6. Gas reactor international cooperative program interim report: German Pebble Bed Reactor design and technology review

    International Nuclear Information System (INIS)

    This report describes and evaluates several gas-cooled reactor plant concepts under development within the Federal Republic of Germany (FRG). The concepts, based upon the use of a proven Pebble Bed Reactor (PBR) fuel element design, include nuclear heat generation for chemical processes and electrical power generation. Processes under consideration for the nuclear process heat plant (PNP) include hydrogasification of coal, steam gasification of coal, combined process, and long-distance chemical heat transportation. The electric plant emphasized in the report is the steam turbine cycle (HTR-K), although the gas turbine cycle (HHT) is also discussed. The study is a detailed description and evaluation of the nuclear portion of the various plants. The general conclusions are that the PBR technology is sound and that the HTR-K and PNP plant concepts appear to be achievable through appropriate continuing development programs, most of which are either under way or planned

  7. Requirements for helium cooled pebble bed blanket and R and D activities

    Energy Technology Data Exchange (ETDEWEB)

    Carloni, D., E-mail: dario.carloni@kit.edu; Boccaccini, L.V.; Franza, F.; Kecskes, S.

    2014-10-15

    This work aims to give an outline of the design requirements of the helium cooled pebble bed (HCPB) blanket and its associated R and D activities. In DEMO fusion reactor the plasma facing components have to fulfill several requirements dictated by safety and process sustainability criteria. In particular the blanket of a fusion reactor shall transfer the heat load coming from the plasma to the cooling system and also provide tritium breeding for the fuel cycle of the machine. KIT has been investigating and developed a helium-cooled blanket for more than three decades: the concept is based on the adoption of separated small lithium orthosilicate (tritium breeder) and beryllium (neutron multiplier) pebble beds, i.e. the HCPB blanket. One of the test blanket modules of ITER will be a HCPB type, aiming to demonstrate the soundness of the concept for the exploitation in future fusion power plants. A discussion is reported also on the development of the design criteria for the blanket to meet the requirements, such as tritium environmental release, also with reference to the TBM. The selection of materials and components to be used in a unique environment as the Tokamak of a fusion reactor requires dedicated several R and D activities. For instance, the performance of the coolant and the tritium self-sufficiency are key elements for the realization of the HCPB concept. Experimental campaigns have been conducted to select the materials to be used inside the solid breeder blanket and R and D activities have been carried out to support the design. The paper discusses also the program of future developments for the realization of the HCPB concept, also focusing to the specific campaigns necessary to qualify the TBM for its implementation in the ITER machine.

  8. Comparative evaluation of pebble-bed and prismatic fueled high-temperature gas-cooled reactors

    Energy Technology Data Exchange (ETDEWEB)

    Kasten, P.R.; Bartine, D.E.

    1981-01-01

    A comparative evaluation has been performed of the HTGR and the Federal Republic of Germany's Pebble Bed Reactor (PBR) for potential commercial applications in the US. The evaluation considered two reactor sizes (1000 and 3000 MW(t)) and three process applications (steam cycle, direct cycle, and process heat, with outlet coolant temperatures of 750, 850, and 950/sup 0/C, respectively). The primary criterion for the comparison was the levelized (15-year) cost of producing electricity or process heat. Emphasis was placed on the cost impact of differences between the prismatic-type HTGR core, which requires periodic refuelings during reactor shutdowns, and the pebble bed PBR core, which is refueled continuously during reactor operations. Detailed studies of key technical issues using reference HTGR and PBR designs revealed that two cost components contributing to the levelized power costs are higher for the PBR: capital costs and operation and maintenance costs. A third cost component, associated with nonavailability penalties, tended to be higher for the PBR except for the process heat application, for which there is a large uncertainty in the HTGR nonavailability penalty at the 950/sup 0/C outlet coolant temperature. A fourth cost component, fuel cycle costs, is lower for the PBR, but not sufficiently lower to offset the capital cost component. Thus the HTGR appears to be slightly superior to the PBR in economic performance. Because of the advanced development of the HTGR concept, large HTGRs could also be commercialized in the US with lower R and D costs and shorter lead times than could large PBRs. It is recommended that the US gas-cooled thermal reactor program continue giving primary support to the HTGR, while also maintaining its cooperative PBR program with FRG.

  9. Comparative evaluation of pebble-bed and prismatic fueled high-temperature gas-cooled reactors

    International Nuclear Information System (INIS)

    A comparative evaluation has been performed of the HTGR and the Federal Republic of Germany's Pebble Bed Reactor (PBR) for potential commercial applications in the US. The evaluation considered two reactor sizes [1000 and 3000 MW(t)] and three process applications (steam cycle, direct cycle, and process heat, with outlet coolant temperatures of 750, 850, and 9500C, respectively). The primary criterion for the comparison was the levelized (15-year) cost of producing electricity or process heat. Emphasis was placed on the cost impact of differences between the prismatic-type HTGR core, which requires periodic refuelings during reactor shutdowns, and the pebble bed PBR core, which is refueled continuously during reactor operations. Detailed studies of key technical issues using reference HTGR and PBR designs revealed that two cost components contributing to the levelized power costs are higher for the PBR: capital costs and operation and maintenance costs. A third cost component, associated with nonavailability penalties, tended to be higher for the PBR except for the process heat application, for which there is a large uncertainty in the HTGR nonavailability penalty at the 9500C outlet coolant temperature. A fourth cost component, fuel cycle costs, is lower for the PBR, but not sufficiently lower to offset the capital cost component. Thus the HTGR appears to be slightly superior to the PBR in economic performance. Because of the advanced development of the HTGR concept, large HTGRs could also be commercialized in the US with lower R and D costs and shorter lead times than could large PBRs. It is recommended that the US gas-cooled thermal reactor program continue giving primary support to the HTGR, while also maintaining its cooperative PBR program with FRG

  10. Development of a thermal–hydraulic analysis code for the Pebble Bed Water-cooled Reactor

    International Nuclear Information System (INIS)

    Highlights: ► Main design features of the PBWR were put forward. ► Thermal–hydraullics analysis code for the PBWR was developed and verified. ► Key thermal–hydraullics parameters were calculated in normal operation. ► The PBWR has a great pressure loss but an excellent heat transfer characteristic. ► Maximum fuel temperature and MDNBR are in conformity with safety criterion. - Abstract: The Pebble Bed Water-cooled Reactor (PBWR) is a water-moderated water-cooled pebble bed reactor in which millions of tristructural-isotropic (TRISO) coated micro-fuel elements (MFE) pile in each assembly. Light water is used as coolant that flows from bottom to top in the assembly while the moderator water flows in the reverse direction out of the assembly. Steady-state thermal–hydraullic analysis code for the PBWR will provide a set of thermal hydraulic parameters of the primary loop so that heat transported out of the core can match with the heat generated by the core for a safe operation of the reactor. The key parameters of the core including the void fraction, pressure drop, heat transfer coefficients, the temperature distribution and the Departure from Nucleate Boiling Ratio (DNBR) is calculated for the core in normal operation. The code can calculate for liquid region, water-steam two phase region and superheated steam region. The results show that the maximum fuel temperature is much lower than the design limitation and the flow distribution can meet the cooling requirement in the reactor core. As a new type of nuclear reactor, the main design features with a sufficient safety margin were also put forward in this paper.

  11. Requirements for helium cooled pebble bed blanket and R and D activities

    International Nuclear Information System (INIS)

    This work aims to give an outline of the design requirements of the helium cooled pebble bed (HCPB) blanket and its associated R and D activities. In DEMO fusion reactor the plasma facing components have to fulfill several requirements dictated by safety and process sustainability criteria. In particular the blanket of a fusion reactor shall transfer the heat load coming from the plasma to the cooling system and also provide tritium breeding for the fuel cycle of the machine. KIT has been investigating and developed a helium-cooled blanket for more than three decades: the concept is based on the adoption of separated small lithium orthosilicate (tritium breeder) and beryllium (neutron multiplier) pebble beds, i.e. the HCPB blanket. One of the test blanket modules of ITER will be a HCPB type, aiming to demonstrate the soundness of the concept for the exploitation in future fusion power plants. A discussion is reported also on the development of the design criteria for the blanket to meet the requirements, such as tritium environmental release, also with reference to the TBM. The selection of materials and components to be used in a unique environment as the Tokamak of a fusion reactor requires dedicated several R and D activities. For instance, the performance of the coolant and the tritium self-sufficiency are key elements for the realization of the HCPB concept. Experimental campaigns have been conducted to select the materials to be used inside the solid breeder blanket and R and D activities have been carried out to support the design. The paper discusses also the program of future developments for the realization of the HCPB concept, also focusing to the specific campaigns necessary to qualify the TBM for its implementation in the ITER machine

  12. Supplemental Report on Nuclear Safeguards Considerations for the Pebble Bed Modular Reactor (PBMR)

    Energy Technology Data Exchange (ETDEWEB)

    Moses, David Lewis [ORNL; Ehinger, Michael H [ORNL

    2010-05-01

    Recent reports by Department of Energy National Laboratories have discussed safeguards considerations for the low enriched uranium (LEU) fueled Pebble Bed Modular Reactor (PBMR) and the need for bulk accountancy of the plutonium in used fuel. These reports fail to account effectively for the degree of plutonium dilution in the graphitized-carbon pebbles that is sufficient to meet the International Atomic Energy Agency's (IAEA's) 'provisional' guidelines for termination of safeguards on 'measured discards.' The thrust of this finding is not to terminate safeguards but to limit the need for specific accountancy of plutonium in stored used fuel. While the residual uranium in the used fuel may not be judged sufficiently diluted to meet the IAEA provisional guidelines for termination of safeguards, the estimated quantities of {sup 232}U and {sup 236}U in the used fuel at the target burn-up of {approx}91 GWD/MT exceed specification limits for reprocessed uranium (ASTM C787) and will require extensive blending with either natural uranium or uranium enrichment tails to dilute the {sup 236}U content to fall within specification thus making the PBMR used fuel less desirable for commercial reprocessing and reuse than that from light water reactors. Also the PBMR specific activity of reprocessed uranium isotopic mixture and its A{sub 2} values for effective dose limit if released in a dispersible form during a transportation accident are more limiting than the equivalent values for light water reactor spent fuel at 55 GWD/MT without accounting for the presence of the principal carry-over fission product ({sup 99}Tc) and any possible plutonium contamination that may be present from attempted covert reprocessing. Thus, the potentially recoverable uranium from PBMR used fuel carries reactivity penalties and radiological penalties likely greater than those for reprocessed uranium from light water reactors. These factors impact the economics of

  13. Sustainability of thorium-uranium in pebble-bed fluoride salt-cooled high temperature reactor

    Directory of Open Access Journals (Sweden)

    Zhu Guifeng

    2016-01-01

    Full Text Available Sustainability of thorium fuel in a Pebble-Bed Fluoride salt-cooled High temperature Reactor (PB-FHR is investigated to find the feasible region of high discharge burnup and negative Flibe (2LiF-BeF2 salt Temperature Reactivity Coefficient (TRC. Dispersion fuel or pellet fuel with SiC cladding and SiC matrix is used to replace the tristructural-isotropic (TRISO coated particle system for increasing fuel loading and decreasing excessive moderation. To analyze the neutronic characteristics, an equilibrium calculation method of thorium fuel self-sustainability is developed. We have compared two refueling schemes (mixing flow pattern and directional flow pattern and two kinds of reflector materials (SiC and graphite. This method found that the feasible region of breeding and negative Flibe TRC is between 20 vol% and 62 vol% fuel loading in the fuel. A discharge burnup could be achieved up to about 200 MWd/kgHM. The case with directional flow pattern and SiC reflector showed superior burnup characteristics but the worst radial power peak factor, while the case with mixing flow pattern and SiC reflector, which was the best tradeoff between discharge burnup and radial power peak factor, could provide burnup of 140 MWd/kgHM and about 1.4 radial power peak factor with 50 vol% dispersion fuel. In addition, Flibe salt displays good neutron properties as a coolant of quasi-fast reactors due to the strong 9Be(n,2n reaction and low neutron absorption of 6Li (even at 1000 ppm in fast spectrum. Preliminary thermal hydraulic calculation shows good safety margin. The greatest challenge of this reactor may be the decades irradiation time of the pebble fuel.

  14. Final Report on Utilization of TRU TRISO Fuel as Applied to HTR Systems Part I: Pebble Bed Reactors

    Energy Technology Data Exchange (ETDEWEB)

    Brian Boer; Abderrafi M. Ougouag

    2011-03-01

    The Deep-Burn (DB) concept [ ] focuses on the destruction of transuranic nuclides from used light water reactor (LWR) fuel. These transuranic nuclides are incorporated into tri-isotopic (TRISO) coated fuel particles and used in gas-cooled reactors with the aim of a fractional fuel burnup of 60 to 70% in fissions per initial metal atom (FIMA). This high performance is expected through the use of multiple recirculation passes of the fuel in pebble form without any physical or chemical changes between passes. In particular, the concept does not call for reprocessing of the fuel between passes. In principle, the DB pebble bed concept employs the same reactor designs as the presently envisioned low-enriched uranium core designs, such as the 400 MWth Pebble Bed Modular Reactor (PBMR-400) [ ]. Although it has been shown in the previous Fiscal Year (FY) (2009) that a PuO2 fueled pebble bed reactor concept is viable, achieving a high fuel burnup while remaining within safety-imposed prescribed operational limits for fuel temperature, power peaking, and temperature reactivity feedback coefficients for the entire temperature range, is challenging. The presence of the isotopes 239Pu, 240Pu, and 241Pu that have resonances in the thermal energy range significantly modifies the neutron thermal energy spectrum as compared to a standard, UO2-fueled core. Therefore, the DB pebble bed core exhibits a relatively hard neutron energy spectrum. However, regions within the pebble bed that are near the graphite reflectors experience a locally softer spectrum. This can lead to power and temperature peaking in these regions. Furthermore, a shift of the thermal energy spectrum with increasing temperature can lead to increased absorption in the resonances of the fissile Pu isotopes. This can lead to a positive temperature reactivity coefficient for the graphite moderator under certain operating conditions. Regarding the coated particle performance, the FY 2009 investigations showed that no

  15. Characterization of constrained beryllium pebble beds after neutron irradiation at HFR at high temperatures up to helium production of 3000 appm

    Energy Technology Data Exchange (ETDEWEB)

    Chakin, V., E-mail: vladimir.chakin@kit.edu [Institute for Applied Materials – Applied Materials Physics, Karlsruhe Institute of Technology, Hermann-von-Helmholtz-Plarz 1, 76344 Eggenstein-Leopoldshafen (Germany); Rolli, R. [Institute for Applied Materials – Materials and Biomechanics, Karlsruhe Institute of Technology, Hermann-von-Helmholtz-Plarz 1, 76344 Eggenstein-Leopoldshafen (Germany); Moeslang, A.; Vladimirov, P.; Kurinskiy, P. [Institute for Applied Materials – Applied Materials Physics, Karlsruhe Institute of Technology, Hermann-von-Helmholtz-Plarz 1, 76344 Eggenstein-Leopoldshafen (Germany); Til, S. van; Magielsen, A.J. [Nuclear Research and Consultancy Group, Westerduinweg 3, Postbus 25, 1755 ZG Petten (Netherlands); Zmitko, M. [The European Joint Undertaking for ITER and the Development of Fusion Energy, c/ Josep Pla, no. 2, Torres Diagonal Litoral, Edificio B3, 08019 Barcelona (Spain)

    2013-10-15

    Highlights: • Defragmentation of beryllium pebbles at irradiation temperatures of 873 and 948 K was detected. • Formation of brittle beryllium oxide layers on neutron irradiated beryllium pebbles was detected. • Strong interaction between beryllium pebbles and platinum foil under neutron irradiation was detected. • Strong interaction between beryllium pebbles and austenitic stainless steel under neutron irradiation was detected. -- Abstract: Small constrained beryllium pebble beds as well as unconstrained beryllium pebbles have been irradiated within HIDOBE-01 experiment at HFR, Petten, the Netherlands. Beryllium pebbles with 1 mm diameter produced by Rotating Electrode Method (REM) were investigated after irradiation at 630, 740, 873, and 948 K up to helium production of 3000 appm. Intensive pore and bubble formation occurs in beryllium after 873 K irradiation. In the contact zones of the pebbles enhanced pore formation takes place. Oxidation of beryllium pebble external surfaces is accompanied by partial destruction of oxide layers owing to their high brittleness. Strong interactions between beryllium pebbles and platinum foil, as well as between beryllium and stainless steel at contact zones occur at 873 and 948 K.

  16. Compilation of reactor physics data of the year 1983, AVR reactor

    International Nuclear Information System (INIS)

    The 'AVR reactor physics data' is a documentation published once a year, the data presented being obtained by a simulation of reactor operation using the AVR-80 numerical model. This model is constantly updated and improved in response to new results and developments in the field of reactor theory and thermohydraulics, and in response to theoretical or practical modifications of reactor operation or in the computer system. The large variety of measured data available in the AVR reactor simulation system also makes it an ideal testing system for verification of the computing programs presented in the compilation. A survey of the history of operations in 1983 and a short explanation of the computerized simulation methods are followed by tables and graphs that serve as a source of topical data for readers interested in the physics of high-temperature pebble-bed reactors. (orig./HP)

  17. Effective Thermal Property Estimation of Unitary Pebble Beds Based on a CFD-DEM Coupled Method for a Fusion Blanket

    Science.gov (United States)

    Chen, Lei; Chen, Youhua; Huang, Kai; Liu, Songlin

    2015-12-01

    Lithium ceramic pebble beds have been considered in the solid blanket design for fusion reactors. To characterize the fusion solid blanket thermal performance, studies of the effective thermal properties, i.e. the effective thermal conductivity and heat transfer coefficient, of the pebble beds are necessary. In this paper, a 3D computational fluid dynamics discrete element method (CFD-DEM) coupled numerical model was proposed to simulate heat transfer and thereby estimate the effective thermal properties. The DEM was applied to produce a geometric topology of a prototypical blanket pebble bed by directly simulating the contact state of each individual particle using basic interaction laws. Based on this geometric topology, a CFD model was built to analyze the temperature distribution and obtain the effective thermal properties. The current numerical model was shown to be in good agreement with the existing experimental data for effective thermal conductivity available in the literature. supported by National Special Project for Magnetic Confined Nuclear Fusion Energy of China (Nos. 2013GB108004, 2015GB108002, 2014GB122000 and 2014GB119000), and National Natural Science Foundation of China (No. 11175207)

  18. Gas Turbine High Temperature Gas (Helium) Reactor Using Pebble Bed Fuel Derived from Spent Fuel

    International Nuclear Information System (INIS)

    Project goals: Build on the $1B investment spent during the NGNP Project for the only true Inherently Safe Small Modular Reactor Design – the only SMR design that can make this claim due to negative temperature coefficient of reactivity - no containment required – less construction cost. NPMC in Partnership with Pebble Bed Modular Group, a fully owned subsidiary of Eskom, RSA to Factory Build Complete Plant in Modular Sections at Factory Site in Oswego, NY for transport to site by rail or shipping for world wide export. NPMC will provide Project and Construction Management of all new builds from plant sites through construction, commissioning and startup using local labor. License and Construct ion of spent fuel processing facility in both NY and South Africa using Proven Technology. Ultimate goals of project: 1. Award of the 2013 US DOE Innovative SMR $452M cost share grant for US NRC License Certification 2.Build Full Scale Demonstration Plant at Koeburg, RSA with World Bank Funding managed by NPMC in collaboration with our legal firm, Haynes and Boone LLP 3. Take Plant Orders Immediately (10% Down Payment) 4. Form Strategic Alliance with Domestic and/or International Utility

  19. Pebble bed modular reactors versus other generation technologies. Costs and challenges for South Africa

    International Nuclear Information System (INIS)

    South Africa is Africa's major economy, with plans to double its electricity generation capacity by 2026. South Africa has spent almost two decades developing a nuclear reactor known as a Pebble Bed Modular Reactor (PBMR), which could provide substantial benefits to the electricity grid but was recently mothballed due to high costs. This work estimates the lifecycle financial costs of South African PBMRs, then compares these costs to those of five other generation options: coal, nuclear as pressurized water reactors (PWRs), wind, and solar as photovoltaics (PV) or concentrating solar power (CSP). Each technology is evaluated with low, base case, and high assumptions for capital costs, construction time, and interest rates. Decommissioning costs, project lifetime, capacity factors, and sensitivity to carbon price are also considered. PBMR could be cost competitive with coal under certain low cost conditions, even without a carbon price. However, international lending practices and other factors suggest that a high capital cost, high interest rate nuclear plant is likely to be competing with a low capital cost, low interest rate coal plant in a market where cost recovery is challenging. PBMR could potentially become more competitive if low rate international loans were available to nuclear projects or became unavailable to coal projects. (author)

  20. Uncertainty and Sensitivity Analyses of a Pebble Bed HTGR Loss of Cooling Event

    Directory of Open Access Journals (Sweden)

    Gerhard Strydom

    2013-01-01

    Full Text Available The Very High Temperature Reactor Methods Development group at the Idaho National Laboratory identified the need for a defensible and systematic uncertainty and sensitivity approach in 2009. This paper summarizes the results of an uncertainty and sensitivity quantification investigation performed with the SUSA code, utilizing the International Atomic Energy Agency CRP 5 Pebble Bed Modular Reactor benchmark and the INL code suite PEBBED-THERMIX. Eight model input parameters were selected for inclusion in this study, and after the input parameters variations and probability density functions were specified, a total of 800 steady state and depressurized loss of forced cooling (DLOFC transient PEBBED-THERMIX calculations were performed. The six data sets were statistically analyzed to determine the 5% and 95% DLOFC peak fuel temperature tolerance intervals with 95% confidence levels. It was found that the uncertainties in the decay heat and graphite thermal conductivities were the most significant contributors to the propagated DLOFC peak fuel temperature uncertainty. No significant differences were observed between the results of Simple Random Sampling (SRS or Latin Hypercube Sampling (LHS data sets, and use of uniform or normal input parameter distributions also did not lead to any significant differences between these data sets.

  1. Design of Complex Systems to Achieve Passive Safety: Natural Circulation Cooling of Liquid Salt Pebble Bed Reactors

    Science.gov (United States)

    Scarlat, Raluca Olga

    This dissertation treats system design, modeling of transient system response, and characterization of individual phenomena and demonstrates a framework for integration of these three activities early in the design process of a complex engineered system. A system analysis framework for prioritization of experiments, modeling, and development of detailed design is proposed. Two fundamental topics in thermal-hydraulics are discussed, which illustrate the integration of modeling and experimentation with nuclear reactor design and safety analysis: thermal-hydraulic modeling of heat generating pebble bed cores, and scaled experiments for natural circulation heat removal with Boussinesq liquids. The case studies used in this dissertation are derived from the design and safety analysis of a pebble bed fluoride salt cooled high temperature nuclear reactor (PB-FHR), currently under development in the United States at the university and national laboratories level. In the context of the phenomena identification and ranking table (PIRT) methodology, new tools and approaches are proposed and demonstrated here, which are specifically relevant to technology in the early stages of development, and to analysis of passive safety features. A system decomposition approach is proposed. Definition of system functional requirements complements identification and compilation of the current knowledge base for the behavior of the system. Two new graphical tools are developed for ranking of phenomena importance: a phenomena ranking map, and a phenomena identification and ranking matrix (PIRM). The functional requirements established through this methodology were used for the design and optimization of the reactor core, and for the transient analysis and design of the passive natural circulation driven decay heat removal system for the PB-FHR. A numerical modeling approach for heat-generating porous media, with multi-dimensional fluid flow is presented. The application of this modeling

  2. A preliminary conceptual design for a 150 MWth pebble bed reactor core using the VSOP94 code package

    International Nuclear Information System (INIS)

    Recently, the hydrogen production using heat source of the high-temperature gas-cooled reactor (HTGR) has been attracting worldwide attention. Since the domestic neutronic design codes for the LWR core design were judged not to be applicable to design of the HTGRs, the VSOP94 code system for the core designs of pebble bed type HTGRs was installed in order to be used in the HTGR design until the domestic code system would be developed. After the VSOP94 was verified against a benchmark calculation for the PRROTEUS experiment, the preliminary conceptual design for a hypothetical bed reator with 150 MWth was performed using the VSOP94

  3. Core and fuel design for Pebble Bed Modular Reactor (PBMR) using SRAC computer code

    International Nuclear Information System (INIS)

    Core and fuel down scale analysis on PBMR-HTR using SRAC program aims to identify the influence of U235 enrichment, burnable poison, coolant flow rate and coolant temperature entered to criticality core and safety aspects of nuclear reactor with the parameters are multiplication factor (keff) and fuel temperature coefficient, moderator temperature coefficient and coolant temperature coefficient. Core PBMR-HTR finite cylindrical with a hole in the middle which contains 334,000 pebble fuel bed. That consist of UO2 fuel, graphite moderator and helium coolant. Down scale the design model performed on the half core represent the whole core. The study was conducted by varying the fuel enrichment of 8%; 8.5%; 9%; 9.5% and 10%, while variation burnable poison enrichment at 5 ppm, 7 ppm, 9 ppm, 11 ppm and 15 ppm. The variation of coolant flow rate of 60%, 80%, 100%, 120% and 140% from its original value at 17.118 kg/s while the variation of coolant temperature input at 673.15 K; 723.15 K; 773.15 K; 823.15 K and 873.15 K. In this research, value of keff without Gd2O3 are 1.026213 (BOL) and 1.004173 (EOL) with excess reactivity of 2.55% with 9% U235 enrichment. While keff on BOL by using 7 ppm Gd2O3 of 1.006968 and 1.004198 for EOL with excess reactivity of 0.69%. Fuel temperature reactivity coefficient, moderator and coolant in a row for -8.597317E-05/K; -2.595284E-05 /K and 1.1496E-06/K. Temperature reactivity coefficient is negative. This indicates inherent safety characteristic have been met. Increasing the input temperature and coolant flow rate reduction lowers the value of keff core, and it will contribute to negative reactivity coefficient. (author)

  4. Examination of the potential for diversion or clandestine dual use of a pebble-bed reactor to produce plutonium

    International Nuclear Information System (INIS)

    This paper explores the susceptibility of Pebble-Bed Reactors (PBRs) to be used overtly or covertly for the production of plutonium for nuclear weapons. The basic assumption made for the consideration of overt production is that a country would purchase a PBR with the ostensible motive of producing electric power; then, after the power plant was built, the country would divert the facility entirely to the production of weapons material. It is assumed that the country would then have to manufacture production pebbles from natural uranium. The basic assumption made for covert production is that the country would obtain and use a PBR for power production, but that it would clandestinely feed plutonium production pebbles through the reactor in such small numbers that the perturbation on power plant operation would be very difficult to detect. This paper shows the potential rate of plutonium production under such constraints. It is demonstrated that the PBR is a very poor choice for either form of proliferation-intent use. (author)

  5. Gas Reactor International Cooperative program. Pebble bed reactor plant: screening evaluation. Volume 2. Conceptual balance of plant design

    International Nuclear Information System (INIS)

    This report consists of three volumes which describe the design concepts and screening evaluation for a 3000 MW(t) Pebble Bed Reactor Multiplex Plant (PBR-MX). The Multiplex plant produces both electricity and transportable chemical energy via the thermochemical pipeline (TCP). The evaluation was limited to a direct cycle plant which has the steam generators and steam reformers in the primary circuit. This volume describes the conceptual balance-of-plant (BOP) design and was prepared by United Engineers and Constructors, Inc. of Philadelphia, Pennsylvania. The major emphasis of the BOP study was a preliminary design of an overall plant to provide a basis for future studies

  6. Parametric study of thorium fuel cycles in a 100MWth pebble bed high temperature reactor / F. Panday

    OpenAIRE

    Panday, Farisha

    2011-01-01

    The current project was conducted in order to select an optimized open Thorium/Uranium fuel cycle for the Pebble Bed Modular Reactor (PBMR) concept in motivation for the 100MWth PBMR Power Plant. A sensitivity study on the heavy metal loading of the fuel sphere was performed to accomplish this task. The effect on various parameters was evaluated to determine the influence of varying the Heavy Metal (HM) from 6 gHM/sphere to 20 gHM/sphere and at different feed fuel enrichment...

  7. Progress in the Development of the Modular Pebble-Bed Advanced High Temperature Reactor

    International Nuclear Information System (INIS)

    This review article summarizes recent progress by students and faculty at U.C. Berkeley working on the development of the Pebble-Bed Advanced High Temperature Reactor (PB-AHTR). The 410-MWe PBAHTR is a liquid salt cooled reactor that operates at near atmospheric pressure and high power density (20 to 30 MW/m3, compared to 4.8 MW/m3 for helium cooled reactors). Operating with a core inlet temperature of 600 deg. C and outlet temperature of 704 deg. C, the PB-AHTR uses well understood materials of construction including Alloy 800H with Hastelloy N cladding for the reactor vessel and primary loop components, and graphite for core and reflector structures. Recent work by the NE 170 senior design class has developed physical arrangements for the major reactor and power conversion components, along with the structural design for the reactor building and turbine hall featuring seismic base isolation, design for aircraft crash protection, shielding analysis, and design of a multiple-zone ventilation and containment system to provide effective control of radioactive and chemical contamination. The resulting total building volume is 260 m3/MWe, compared to 343 m3/MWe to 486 m3/MWe for current large (1150 to 1600 MWe) LWR designs. These results suggest the potential for significant reductions in construction time and cost. Neutronics studies have verified the capability to design the PB-AHTR with negative fuel and coolant temperature reactivity coefficients, for both LEU and deep-burn TRU fuels. Depletion analysis was also performed to identify optimal core designs to maximize fuel utilization. The additional moderation provided by the coolant simplifies design to achieve optimal moderation, and the spent fuel volume is approximately half that of helium cooled reactors. In collaboration with the Czech Nuclear Research Institute, initial zero-power critical tests were performed to validate PB-AHTR neutronics models. Liquid salts are unique among candidate reactor coolants due

  8. From field to factory-Taking advantage of shop manufacturing for the pebble bed modular reactor

    International Nuclear Information System (INIS)

    The move of nuclear plant construction from the field to the factory for small, advanced pebble bed modular reactor (PBMR) designs has significant benefits compared to traditional light water reactor (LWR) field oriented designs. The use of modular factory construction techniques has a growing economic benefit over time through well-established process learning applications. This paper addresses the basic PBMR design objectives and commercialization model that drive this approach; provides a brief technical description of the PBMR design and layout with representative CAD views and discusses derived figures of merit highlighting the relative simplicity of PBMR compared to a modern LWR. The discussion emphasizes that more of PBMR can be built in the factory due to the simple design of a direct helium Brayton cycle compared to an indirect LWR steam cycle with its associated equipment. For the PBMR design there are fewer and less cumbersome auxiliary and safety systems with their attendant support requirements. Additionally, the labor force economic efficiency for nuclear projects is better in the factory than in the field, including consideration of labor costs and nuclear quality programs. Industrial learning is better in the factory because of the more controlled environment, mechanization optimization opportunities and because of the more stable labor force compared to the field. Supply chain benefits are more readily achievable with strategic contracts for module suppliers. Although building a nuclear power plant is not a typical high volume manufacturing process, for the PBMR-type of plant, with its high degree of standardization and relatively small, simplified design, the shift to factory work has a significant impact on overall project cost due to earlier identification and better coordination of parallel construction paths. This is in stark contrast to the construction of a large LWR in the past. Finally, the PBMR modular plant concept continues at the

  9. Theoretical and experimental research of natural convection in the core of the high temperature pebble bed reactor

    International Nuclear Information System (INIS)

    The physical model of the developed THERMIX-2D-code for computing thermohydraulic behaviour of the core of high temperature pebble bed reactors is verified by experiments with natural convection flow. Such fluid flow behaviour can be of very high importance for the real reactor in the case of natural heat removal decay. The experiments are performed in a special set up testing-stand with pressures up to 30 bars and temperatures up to 3000C by using air and helium as fluid. In comparison with the experimental data the numerical results show that a good and useful simulation is given by the program. Pure natural convection flow in packed pebble beds is calculated with a very high degree of reliability. The investigation of flow stability demonstrate that radial-symmetric relations are not given temporarily when national convection is overlayed by forced convection flow. In the discussion it is explained when and to what extent the program leds to useful results in such situations. The test of the effective heat conductivity lambdasub(eff) results in an improvement of the lambdasub(eff)-data used so far for temperatures below 13000C. (orig.)

  10. Fluid flow and heat transfer investigation of pebble bed reactors using mesh adaptive large-eddy simulation

    International Nuclear Information System (INIS)

    A computational fluid dynamics model with anisotropic mesh adaptivity is used to investigate coolant flow and heat transfer in pebble bed reactors. A novel method for implicitly incorporating solid boundaries based on multi-fluid flow modelling is adopted. The resulting model is able to resolve and simulate flow and heat transfer in randomly packed beds, regardless of the actual geometry, starting off with arbitrarily coarse meshes. The model is initially evaluated using an orderly stacked square channel of channel-height-to-particle diameter ratio of unity for a range of Reynolds numbers. The model is then applied to the face-centred cubical geometry. Coolant flow and heat transfer patterns are investigated. (author)

  11. Optimization of coupled multiphysics methodology for safety analysis of pebble bed modular reactor

    Science.gov (United States)

    Mkhabela, Peter Tshepo

    The research conducted within the framework of this PhD thesis is devoted to the high-fidelity multi-physics (based on neutronics/thermal-hydraulics coupling) analysis of Pebble Bed Modular Reactor (PBMR), which is a High Temperature Reactor (HTR). The Next Generation Nuclear Plant (NGNP) will be a HTR design. The core design and safety analysis methods are considerably less developed and mature for HTR analysis than those currently used for Light Water Reactors (LWRs). Compared to LWRs, the HTR transient analysis is more demanding since it requires proper treatment of both slower and much longer transients (of time scale in hours and days) and fast and short transients (of time scale in minutes and seconds). There is limited operation and experimental data available for HTRs for validation of coupled multi-physics methodologies. This PhD work developed and verified reliable high fidelity coupled multi-physics models subsequently implemented in robust, efficient, and accurate computational tools to analyse the neutronics and thermal-hydraulic behaviour for design optimization and safety evaluation of PBMR concept The study provided a contribution to a greater accuracy of neutronics calculations by including the feedback from thermal hydraulics driven temperature calculation and various multi-physics effects that can influence it. Consideration of the feedback due to the influence of leakage was taken into account by development and implementation of improved buckling feedback models. Modifications were made in the calculation procedure to ensure that the xenon depletion models were accurate for proper interpolation from cross section tables. To achieve this, the NEM/THERMIX coupled code system was developed to create the system that is efficient and stable over the duration of transient calculations that last over several tens of hours. Another achievement of the PhD thesis was development and demonstration of full-physics, three-dimensional safety analysis

  12. Cynod: A Neutronics Code for Pebble Bed Modular Reactor Coupled Transient Analysis

    Energy Technology Data Exchange (ETDEWEB)

    Hikaru Hiruta; Abderrafi M. Ougouag; Hans D. Gougar; Javier Ortensi

    2008-09-01

    The Pebble Bed Reactor (PBR) is one of the two concepts currently considered for development into the Next Generation Nuclear Plant (NGNP). This interest is due, in particular, to the concept’s inherent safety characteristics. In order to verify and confirm the design safety characteristics of the PBR computational tools must be developed that treat the range of phenomena that are expected to be important for this type of reactors. This paper presents a recently developed 2D R-Z cylindrical nodal kinetics code and shows some of its capabilities by applying it to a set of known and relevant benchmarks. The new code has been coupled to the thermal hydraulics code THERMIX/KONVEK[1] for application to the simulation of very fast transients in PBRs. The new code, CYNOD, has been written starting with a fixed source solver extracted from the nodal cylindrical geometry solver contained within the PEBBED code. The fixed source solver was then incorporated into a kinetic solver.. The new code inherits the spatial solver characteristics of the nodal solver within PEBBED. Thus, the time-dependent neutron diffusion equation expressed analytically in each node of the R-Z cylindrical geometry sub-domain (or node) is transformed into one-dimensional equations by means of the usual transverse integration procedure. The one-dimensional diffusion equations in each of the directions are then solved using the analytic Green’s function method. The resulting equations for the entire domain are then re-cast in the form of the Direct Coarse Mesh Finite Difference (D-CMFD) for convenience of solution. The implicit Euler method is used for the time variable discretization. In order to correctly treat the cusping effect for nodes that contain a partially inserted control rod a method is used that takes advantage of the Green’s function solution available in the intrinsic method. In this corrected treatment, the nodes are re-homogenized using axial flux shapes reconstructed based on the

  13. Design of Complex Systems to Achieve Passive Safety: Natural Circulation Cooling of Liquid Salt Pebble Bed Reactors

    Science.gov (United States)

    Scarlat, Raluca Olga

    This dissertation treats system design, modeling of transient system response, and characterization of individual phenomena and demonstrates a framework for integration of these three activities early in the design process of a complex engineered system. A system analysis framework for prioritization of experiments, modeling, and development of detailed design is proposed. Two fundamental topics in thermal-hydraulics are discussed, which illustrate the integration of modeling and experimentation with nuclear reactor design and safety analysis: thermal-hydraulic modeling of heat generating pebble bed cores, and scaled experiments for natural circulation heat removal with Boussinesq liquids. The case studies used in this dissertation are derived from the design and safety analysis of a pebble bed fluoride salt cooled high temperature nuclear reactor (PB-FHR), currently under development in the United States at the university and national laboratories level. In the context of the phenomena identification and ranking table (PIRT) methodology, new tools and approaches are proposed and demonstrated here, which are specifically relevant to technology in the early stages of development, and to analysis of passive safety features. A system decomposition approach is proposed. Definition of system functional requirements complements identification and compilation of the current knowledge base for the behavior of the system. Two new graphical tools are developed for ranking of phenomena importance: a phenomena ranking map, and a phenomena identification and ranking matrix (PIRM). The functional requirements established through this methodology were used for the design and optimization of the reactor core, and for the transient analysis and design of the passive natural circulation driven decay heat removal system for the PB-FHR. A numerical modeling approach for heat-generating porous media, with multi-dimensional fluid flow is presented. The application of this modeling

  14. Pebble bed reactors simulation using MCNP: The Chinese HTR-10 reactor

    Directory of Open Access Journals (Sweden)

    SA Hosseini

    2013-09-01

    Full Text Available   Given the role of Gas-Graphite reactors as the fourth generation reactors and their recently renewed importance, in 2002 the IAEA proposed a set of Benchmarking problems. In this work, we propose a model both efficient in time and resources and exact to simulate the HTR-10 reactor using MCNP-4C code. During the present work, all of the pressing factors in PBM reactor design such as the inter-pebble leakage, fuel particle distribution and fuel pebble packing fraction effects have been taken into account to obtain an exact and easy to run model. Finally, the comparison between the results of the present work and other calculations made at INEEL proves the exactness of the proposed model.

  15. HTR-PROTEUS PEBBLE BED EXPERIMENTAL PROGRAM CORES 9 & 10: COLUMNAR HEXAGONAL POINT-ON-POINT PACKING WITH A 1:1 MODERATOR-TO-FUEL PEBBLE RATIO

    Energy Technology Data Exchange (ETDEWEB)

    John D. Bess

    2013-03-01

    PROTEUS is a zero-power research reactor based on a cylindrical graphite annulus with a central cylindrical cavity. The graphite annulus remains basically the same for all experimental programs, but the contents of the central cavity are changed according to the type of reactor being investigated. Through most of its service history, PROTEUS has represented light-water reactors, but from 1992 to 1996 PROTEUS was configured as a pebble-bed reactor (PBR) critical facility and designated as HTR-PROTEUS. The nomenclature was used to indicate that this series consisted of High Temperature Reactor experiments performed in the PROTEUS assembly. During this period, seventeen critical configurations were assembled and various reactor physics experiments were conducted. These experiments included measurements of criticality, differential and integral control rod and safety rod worths, kinetics, reaction rates, water ingress effects, and small sample reactivity effects (Ref. 3). HTR-PROTEUS was constructed, and the experimental program was conducted, for the purpose of providing experimental benchmark data for assessment of reactor physics computer codes. Considerable effort was devoted to benchmark calculations as a part of the HTR-PROTEUS program. References 1 and 2 provide detailed data for use in constructing models for codes to be assessed. Reference 3 is a comprehensive summary of the HTR-PROTEUS experiments and the associated benchmark program. This document draws freely from these references. Only Cores 9 and 10 are evaluated in this benchmark report due to similarities in their construction. The other core configurations of the HTR-PROTEUS program are evaluated in their respective reports as outlined in Section 1.0. Cores 9 and 10 were evaluated and determined to be acceptable benchmark experiments.

  16. HTR-PROTEUS PEBBLE BED EXPERIMENTAL PROGRAM CORES 9 & 10: COLUMNAR HEXAGONAL POINT-ON-POINT PACKING WITH A 1:1 MODERATOR-TO-FUEL PEBBLE RATIO

    Energy Technology Data Exchange (ETDEWEB)

    John D. Bess

    2014-03-01

    PROTEUS is a zero-power research reactor based on a cylindrical graphite annulus with a central cylindrical cavity. The graphite annulus remains basically the same for all experimental programs, but the contents of the central cavity are changed according to the type of reactor being investigated. Through most of its service history, PROTEUS has represented light-water reactors, but from 1992 to 1996 PROTEUS was configured as a pebble-bed reactor (PBR) critical facility and designated as HTR-PROTEUS. The nomenclature was used to indicate that this series consisted of High Temperature Reactor experiments performed in the PROTEUS assembly. During this period, seventeen critical configurations were assembled and various reactor physics experiments were conducted. These experiments included measurements of criticality, differential and integral control rod and safety rod worths, kinetics, reaction rates, water ingress effects, and small sample reactivity effects (Ref. 3). HTR-PROTEUS was constructed, and the experimental program was conducted, for the purpose of providing experimental benchmark data for assessment of reactor physics computer codes. Considerable effort was devoted to benchmark calculations as a part of the HTR-PROTEUS program. References 1 and 2 provide detailed data for use in constructing models for codes to be assessed. Reference 3 is a comprehensive summary of the HTR-PROTEUS experiments and the associated benchmark program. This document draws freely from these references. Only Cores 9 and 10 are evaluated in this benchmark report due to similarities in their construction. The other core configurations of the HTR-PROTEUS program are evaluated in their respective reports as outlined in Section 1.0. Cores 9 and 10 were evaluated and determined to be acceptable benchmark experiments.

  17. One-dimensional modeling of radial heat removal during depressurized heatup transients in modular pebble-bed and prismatic high temperature gas-cooled reactors

    International Nuclear Information System (INIS)

    A one-dimensional computational model was developed to evaluate the heat removal capabilities of both prismatic-core and pebble-bed modular HTGRs during depressurized heatup transients. A correlation was incorporated to calculate the temperature- and neutron-fluence-dependent thermal conductivity of graphite. The modified Zehner-Schluender model was used to determine the effective thermal conductivity of a pebble bed, accounting for both conduction and radiation. Studies were performed for prismatic-core and pebble-bed modular HTGRs, and the results were compared to analyses performed by GA and GR, respectively. For the particular modular reactor design studied, the prismatic HTGR peak temperature was 2152.20C at 38 hours following the transient initiation, and the pebble-bed peak temperature was 1647.80C at 26 hours. These results compared favorably with those of GA and GE, with only slight differences caused by neglecting axial heat transfer in a one-dimensional radial model. This study found that the magnitude of the initial power density had a greater effect on the temperature excursion than did the initial temperature

  18. US/FRG joint report on the pebble bed high temperature reactor resource conservation potential and associated fuel cycle costs

    International Nuclear Information System (INIS)

    Independent analyses at ORNL and KFA have led to the general conclusion that the flexibility in design and operation of a high-temperature gas-cooled pebble-bed reactor (PBR) can result in favorable ore utilization and fuel costs in comparison with other reactor types, in particular, with light-water reactors (LWRs). Fuel reprocessign and recycle show considerable promise for reducing ore consumption, and even the PBR throwaway cycle is competitive with fuel recycle in an LWR. The best performance results from the use of highly enriched fuel. Proliferation-resistant measures can be taken using medium-enriched fuel at a modest ore penalty, while use of low-enriched fuel would incur further ore penalty. Breeding is possible but net generation of fuel at a significant rate would be expensive, becoming more feasible as ore costs increase substantially. The 233U inventory for a breeder could be produced by prebreeders using 235U fuel

  19. Core design of NPP Pebble Bed Modular Reactor (PBMR) type using computer code MCNP-5 for beginning of life (BOL)

    International Nuclear Information System (INIS)

    The core design of Nuclear Power Plant for Pebble Bed Modular Reactor (PBMR) type with 70 MWe capacity power in Beginning of Life (BOL) has been performed. The aim of this analysis, to know percent enrichment, temperature distribution and safety value by negative temperature coefficient at type PBMR if reactor power become lower equal to 70 MWe. This analysis was expected become one part of overview project development the power plant with 10.000 MWe of total capacity, spread evenly in territory of Indonesia especially to support of smelter industries. The results showed that, effective multiplication factor (keff) with power 70 MWe critical condition at enrichment 5,626 % is 1,00031±0, 00087, based on enrichment result, a value of the temperature coefficient reactivity is 10,0006 pcm/K. Based on the results of these studies, it can be concluded that the PBMR 70 MWe design is theoretically safe. (author)

  20. The modular pebble bed nuclear reactor - the preferred new sustainable energy source for electricity, hydrogen and potable water production?

    International Nuclear Information System (INIS)

    This paper describes a joint project of Massachusetts Institute of technology, Nu-Tec Inc. and Proto Power. The elegant simplicity of graphite moderated pebble bed reactor is the basis for the 'generation four' nuclear power plants. High Temperature Gas Cooled (HTGC) nuclear power plant have the potential to become the preferred base load sustainable energy source for the new millennium. The great attraction of these helium cooled 'Generation Four' nuclear plant can be summarised as follows: Factory assembly line production; Modularity and ease of delivery to site; High temperature Brayton Cycle ideally suited for cogeneration of electricity, potable water and hydrogen; Capital and operating costs competitive with hydrocarbon plant; Design is inherently meltdown proof and proliferation resistant

  1. KUGEL: a thermal, hydraulic, fuel performance, and gaseous fission product release code for pebble bed reactor core analysis

    International Nuclear Information System (INIS)

    The KUGEL computer code is designed to perform thermal/hydraulic analysis and coated-fuel particle performance calculations for axisymmetric pebble bed reactor (PBR) cores. This computer code was developed as part of a Department of Energy (DOE)-funded study designed to verify the published core performance data on PBRs. The KUGEL code is designed to interface directly with the 2DB code, a two-dimensional neutron diffusion code, to obtain distributions of thermal power, fission rate, fuel burnup, and fast neutron fluence, which are needed for thermal/hydraulic and fuel performance calculations. The code is variably dimensioned so that problem size can be easily varied. An interpolation routine allows variable mesh size to be used between the 2DB output and the two-dimensional thermal/hydraulic calculations

  2. Loss-of-water accident analysis of the pebble-bed modular high temperature gas-cooled reactor

    International Nuclear Information System (INIS)

    The high pressure helium and water/steam are respectively used as the primary and secondary coolant for the pebble-bed modular high temperature gas-cooled reactor (HTGR). Loss-of-water accident is one of the typical design basis accident (DBA), which would be caused by malfunction or current failure of the feed water pump, as well as the false action of the feed water valve. During the loss-of-water accident, due to the loss of the secondary heat sink, the temperature and pressure of primary coolant will increase. Subsequently, the reactor scram will be triggered by the protective signal of the “high flow rate proportion of primary circuit and secondary circuit” or the “high core inlet helium temperature”. For this type of the accident, the earlier open of the safety valve of the primary circuit should be avoided by reactor design. Based on the preliminary design of the 250 MW pebble-bed modular high temperature gas-cooled reactor (HTR-PM), with the coupled analysis code TINTE-BLAST, accidents with different slowdown rate of the feed water supply have been studied. The important parameters, including the reactor power, fuel element temperature, inlet/outlet helium temperature of the core, and especially the primary pressure, are analyzed. The consequences with first scram signal succeeding or failing are compared. The results can prove that, according to the current design of the protection system, this kind of accident can be detected in time. The scram signal will trigger the reactor shut down quickly, without causing the earlier open of the safety valve. After the reactor is successfully shut down, due to the inherent safety feature of the HTGR, the temperature and the pressure in the primary circuit will increase very slowly. The temperature of the fuel element, as well as that of the components, will not exceed the design limitations. (author)

  3. Transmutation of nuclear wastes with gas-cooled pebble-bed ads

    International Nuclear Information System (INIS)

    Transmutation of nuclear wastes is being explored for its application to waste management, a fundamental issue for nuclear industry. Several concepts are under consideration, mainly fast breeder reactors and accelerator driven systems (ADS). Inside this second category, we are analysing a helium-cooled graphite moderated sub-critical assembly, which uses as fuel units a small amount of transuranics diluted, in the form of TRISO coated particles, in graphite pebbles. This configuration (PBT) allows for neutron spectra that, taking advantage of the existence of huge capture resonances in the epithermal region, increase in a substantial factor the system transmutation efficiency. Neutronic studies to determine transmutation performance and thermal behaviour are presented and discussed together with an analysis of the additional studies to address before going into detailed design activities. (author)

  4. Experimental Study and Computational Simulations of Key Pebble Bed Thermo-mechanics Issues for Design and Safety

    Energy Technology Data Exchange (ETDEWEB)

    Tokuhiro, Akira; Potirniche, Gabriel; Cogliati, Joshua; Ougouag, Abderrafi

    2014-07-08

    An experimental and computational study, consisting of modeling and simulation (M&S), of key thermal-mechanical issues affecting the design and safety of pebble-bed (PB) reactors was conducted. The objective was to broaden understanding and experimentally validate thermal-mechanic phenomena of nuclear grade graphite, specifically, spheres in frictional contact as anticipated in the bed under reactor relevant pressures and temperatures. The contact generates graphite dust particulates that can subsequently be transported into the flowing gaseous coolent. Under postulated depressurization transients and with the potential for leaked fission products to be adsorbed onto graphite 'dust', there is the potential for fission products to escape from the primary volume. This is a design safety concern. Furthermore, earlier safety assessment identified the distinct possibility for the dispersed dust to combust in contact with air if sufficient conditions are met. Both of these phenomena were noted as important to design review and containing uncertainty to warrant study. The team designed and conducted two separate effects tests to study and benchmark the potential dust-generation rate, as well as study the conditions under which a dust explosion may occure in a standardized, instrumented explosion chamber.

  5. Criticality calculations on pebble-bed HTR-PROTEUS configuration as a validation for the pseudo-scattering tracking method implemented in the MORET 5 Monte Carlo code

    Energy Technology Data Exchange (ETDEWEB)

    Forestier, Benoit; Miss, Joachim; Bernard, Franck; Dorval, Aurelien [Institut de Radioprotection et Surete Nucleaire, Fontenay aux Roses (France); Jacquet, Olivier [Independent consultant (France); Verboomen, Bernard [Belgian Nuclear Research Center - SCK-CEN (Belgium)

    2008-07-01

    The MORET code is a three dimensional Monte Carlo criticality code. It is designed to calculate the effective multiplication factor (k{sub eff}) of any geometrical configuration as well as the reaction rates in the various volumes and the neutron leakage out of the system. A recent development for the MORET code consists of the implementation of an alternate neutron tracking method, known as the pseudo-scattering tracking method. This method has been successfully implemented in the MORET code and its performances have been tested by mean of an extensive parametric study on very simple geometrical configurations. In this context, the goal of the present work is to validate the pseudo-scattering method against realistic configurations. In this perspective, pebble-bed cores are particularly well-adapted cases to model, as they exhibit large amount of volumes stochastically arranged on two different levels (the pebbles in the core and the TRISO particles inside each pebble). This paper will introduce the techniques and methods used to model pebble-bed cores in a realistic way. The results of the criticality calculations, as well as the pseudo-scattering tracking method performance in terms of computation time, will also be presented. (authors)

  6. Gas Reactor International Cooperative program. Pebble bed reactor plant: screening evaluation. Volume 3. Appendix A. Equipment list

    International Nuclear Information System (INIS)

    This report consists of three volumes which describe the design concepts and screening evaluation for a 3000 MW(t) Pebble Bed Reactor Multiplex Plant (PBR-MX). The Multiplex plant produces both electricity and transportable chemical energy via the thermochemical pipeline (TCP). The evaluation was limited to a direct cycle plant which has the steam generators and steam reformers in the primary circuit. Volume 1 reports the overall plant and reactor system and was prepared by the General Electric Company. Core scoping studies were performed which evaluated the effects of annular and cylindrical core configurations, radial blanket zones, burnup, and ball heavy metal loadings. The reactor system, including the PCRV, was investigated for both the annular and cylindrical core configurations. Volume 3 is an Appendix containing the equipment list for the plant and was also prepared by United Engineers and Constructors, Inc. It tabulates the major components of the plant and describes each in terms of quantity, type, orientation, etc., to provide a basis for cost estimation

  7. Gas Reactor International Cooperative program. Pebble bed reactor plant: screening evaluation. Volume 3. Appendix A. Equipment list

    Energy Technology Data Exchange (ETDEWEB)

    1979-11-01

    This report consists of three volumes which describe the design concepts and screening evaluation for a 3000 MW(t) Pebble Bed Reactor Multiplex Plant (PBR-MX). The Multiplex plant produces both electricity and transportable chemical energy via the thermochemical pipeline (TCP). The evaluation was limited to a direct cycle plant which has the steam generators and steam reformers in the primary circuit. Volume 1 reports the overall plant and reactor system and was prepared by the General Electric Company. Core scoping studies were performed which evaluated the effects of annular and cylindrical core configurations, radial blanket zones, burnup, and ball heavy metal loadings. The reactor system, including the PCRV, was investigated for both the annular and cylindrical core configurations. Volume 3 is an Appendix containing the equipment list for the plant and was also prepared by United Engineers and Constructors, Inc. It tabulates the major components of the plant and describes each in terms of quantity, type, orientation, etc., to provide a basis for cost estimation.

  8. A comparison of experimental thermal stratification parameters for an oil/pebble-bed thermal energy storage (TES) system during charging

    International Nuclear Information System (INIS)

    Highlights: → Six experimental thermal stratification parameters are evaluated in a TES system. → Stratification number and temperature difference evaluate stratification adequately. → Exergy efficiency and Reynolds number evaluate stratification qualitatively. → Richardson number and energy efficiency not clearly related with stratification. -- Abstract: Six different experimental thermal stratification evaluation parameters during charging for an oil/pebble-bed TES system are presented. The six parameters are the temperature distribution along the height of the storage tank at different time intervals, the charging energy efficiency, the charging exergy efficiency, the stratification number, the Reynolds number and the Richardson number. These parameters are evaluated under six different experimental charging conditions. Temperature distribution along the height of the storage tank at different time intervals and the stratification number are parameters found to describe thermal stratification quantitatively adequately. On the other-hand, the charging exergy efficiency and the Reynolds number give important information about describing thermal stratification qualitatively and should be used with care. The charging energy efficiency and the Richardson number have no clear relationship with thermal stratification.

  9. Study on the Calculation of Pebble-Bed Reactor Multiplication Factor As a Function of Fuel Kernel Radius at Various Enrichments

    International Nuclear Information System (INIS)

    Main characteristics of PBR comes from utilization of coated particle fuels dispersed in pebble fuels . Because of vibration, fuel kernel can be grouped into cluster and in these cases, neutronic characteristics of pebble fuel significantly changes . In this study, cluster is modeled structural form consisting of uniform cubic cells with eight neighborhood TRISO particles . Neutronic characteristics was investigated by calculating pebble-bed reactor multiplication factor as a function of fuel kernel radius at various enrichments . The calculation results using MCNP5 code with ENDF/BVI neutron library show that keff value depends on the average fuel radius and reaches its minimum when all kernels have the same radius, i.e. 0.0280 cm . With this radius, the total kernel surface area achieves maximum value . The dependence of keff on fuel kernel radius decreases in relation to the increase in uranium enrichment . However, keff value is not affected by fuel kernel radius when the uranium is 100% enriched . From these result, it can be concluded that, exception of uranium enrichment, the selection of fuel kernel radius should be considered thoroughly in designing a PBR, since this parameter provides significant influences on neutronic characteristics of the reactor. (author)

  10. Installation of a programme system for determination of HEU/LEU-equilibrium-combined cores for pebble bed reactors and applicaton to the AVR-reactor

    International Nuclear Information System (INIS)

    In this work different HEU/LEU-equilibrium-combined core configurations were calculated. By analysis of these results the optimum operation strategy and the accompanying equilibrium core are determined and the essential influence quantities on temperature profiles and shut-down balance are worked out: 1) The neutron-physical and thermodynamic properties of the combined core are adjustable in broad limits by changing the operating conditions of fuelling. 2) The shut-down balance is strongly dependent on the part of LEU-fuel elements; it is running short with increasing LEU-part among other things because of the comparatively higher absorption in the core. 3) The thermodynamic behaviour is getting more favourable with increasing LEU-part. 4) The influence of the eliminating age of the HEU-fuel elements on the neutron physical and thermodynamic behaviour is much more stronger than that of the LEU-elements. 5) The temperature profiles of the core become much more favourable with increasing elimination age of the LEU-fuel elements and with decreasing elimination age of the HEU-fuel elements. (orig.)

  11. Design and construction of a prototype advanced on-line fuel burn-up monitoring system for the modular pebble bed reactor

    Energy Technology Data Exchange (ETDEWEB)

    Su, Bingjing; Hawari, Ayman, I.

    2004-03-30

    Modular Pebble Bed Reactor (MPBR) is a high temperature gas-cooled nuclear power reactor currently under study as a next generation reactor system. In addition to its inherently safe design, a unique feature of this reactor is its multi-pass fuel circulation in which the fuel pebbles are randomly loaded and continuously cycled through the core until they reach their prescribed End-of-Life burn-up limit. Unlike the situation with a conventional light water reactor, depending solely on computational methods to perform in-core fuel management for MPBR will be highly inaccurate. An on-line measurement system is needed to accurately assess whether a given pebble has reached its End-of-Life burn-up limit and thereby provide an on-line, automated go/no-go decision on fuel disposition on a pebble-by-pebble basis. This project investigated approaches to analyzing fuel pebbles in real time using gamma spectroscopy and possibly using passive neutron counting of spontaneous fission neutrons to provide the speed, accuracy, and burn-up range required for burnup determination of MPBR. It involved all phases necessary to develop and construct a burn-up monitor, including a review of the design requirements of the system, identification of detection methodologies, modeling and development of potential designs, and finally, the construction and testing of an operational detector system. Based upon the research work performed in this project, the following conclusions are made. In terms of using gamma spectrometry, two possible approaches were identified for burnup assay. The first approach is based on the measurement of the absolute activity of Cs-137. However, due to spectral interference and the need for absolute calibration of the spectrometer, the uncertainty in burnup determination using this approach was found to range from {approx} {+-}40% at beginning of life to {approx} {+-}10% at the discharge burnup. An alternative approach is to use a relative burnup indicator. In this

  12. PBMR radionuclide source term analysis validation based on AVR operating experience

    Energy Technology Data Exchange (ETDEWEB)

    Stoker, C.C. [PBMR, Lake Buena Vista Building, 1267 Gordon Hood Avenue, Centurion 0046 (South Africa); Olivier, L.D. [Independent Nuclear Consultants, Grahamstown (South Africa); Stassen, E.; Reitsma, F. [PBMR, Lake Buena Vista Building, 1267 Gordon Hood Avenue, Centurion 0046 (South Africa); Merwe, J.J. van der, E-mail: hanno.vdmerwe@pbmr.co.z [PBMR, Lake Buena Vista Building, 1267 Gordon Hood Avenue, Centurion 0046 (South Africa)

    2010-10-15

    The determination of radionuclide source terms is vital for any reactor design and licensing safety evaluation. This paper provides an overview of the PBMR analysis tools with specific focus on the modelling of mobile and deposited radionuclide source terms within the pressure boundary of a typical pebble-bed high temperature reactor (HTR). The main focus is on the Dust and Activity Migration and Distribution (DAMD) software code system that models the activation, migration and time-dependent distribution of dust and atomic particles in an HTR such as the AVR and PBMR. Since DAMD provides a time-dependent systems integrated model of HTR designs, most of the obvious physical phenomena relevant to source terms are at play. These include the neutron flux, activation cross-sections, radioactive decay, dust production rates, dust impurity levels, dust filter capabilities, dust particle size distributions, thermal-hydraulic parameters influencing the migration and distribution of particles throughout the main power system and subsystems, and helium coolant leakage and make-up rates. At this stage the DAMD calibration and validation is mainly based on the operational data, experiments and measurements made during 21 years of operating life of the AVR. The comparisons of the DAMD results with various AVR measurements provide confidence in the use of DAMD for the PBMR design and safety evaluations. In addition, sensitivity analyses are performed with DAMD to determine the bounding system parameters that drive the migration and distribution of radionuclides. The use of DAMD to evaluate design configurations, e.g. the effect of the introduction and placement of filters on the radionuclide distribution, is also shown. In conclusion, the importance of a systems modelling approach for radionuclide transport and distribution within the pressure boundary of a typical HTR system, is demonstrated. Since the DAMD code system is calibrated and validated against the AVR measurements it

  13. SHOVAV-JUEL. A one dimensional space-time kinetic code for pebble-bed high-temperature reactors with temperature and Xenon feedback

    International Nuclear Information System (INIS)

    The present report describes the modelling basis and the structure of the neutron kinetics-code SHOVAV-Juel. Information for users is given regarding the application of the code and the generation of the input data. SHOVAV-Juel is a one-dimensional space-time-code based on a multigroup diffusion approach for four energy groups and six groups of delayed neutrons. It has been developed for the analysis of the transient behaviour of high temperature reactors with pebble-bed core. The reactor core is modelled by horizontal segments to which different materials compositions can be assigned. The temperature dependence of the reactivity is taken into account by using temperature dependent neutron cross sections. For the simulation of transients in an extended time range the time dependence of the reactivity absorption by Xenon-135 is taken into account. (orig./RW)

  14. User's manual for ASTERIX-2: A two-dimensional modular code system for the steady state and xenon transient analysis of a pebble bed high temperature reactor

    International Nuclear Information System (INIS)

    The ASTERIX modular code package was developed at KFA Laboratory-Juelich for the steady state and xenon transient analysis of a pebble bed high temperature reactor. The code package was implemented on the Stanford Linear Accelerator Center Computer in August, 1980, and a user's manual for the current version of the code, identified as ASTERIX-2, was prepared as a cooperative effort by KFA Laboratory and GE-ARSD. The material in the manual includes the requirements for accessing the program, a description of the major subroutines, a listing of the input options, and a listing of the input data for a sample problem. The material is provided in sufficient detail for the user to carry out a wide range of analysis from steady state operations to the xenon induced power transients in which the local xenon, temperature, buckling and control feedback effects have been incorporated in the problem solution. (orig.)

  15. Analytical Solution of Fick's Law of the TRISO-Coated Fuel Particles and Fuel Elements in Pebble-Bed High Temperature Gas-Cooled Reactors

    International Nuclear Information System (INIS)

    Two kinds of approaches are built to solve the fission products diffusion models (Fick's equation) based on sphere fuel particles and sphere fuel elements exactly. Two models for homogenous TRISO-coated fuel particles and fuel elements used in pebble-bed high temperature gas-cooled reactors are presented, respectively. The analytical solution of Fick's equation for fission products diffusion in fuel particles is derived by variables separation. In the fuel element system, a modification of the diffusion coefficient from D to D/r is made to characterize the difference of diffusion rates in distinct areas and it is shown that the Laplace and Hankel transformations are effective as the diffusion coefficient in Fick's equation is dependant on the radius of the fuel element. Both the solutions are useful for the prediction of the fission product behaviors and could be programmed in the corresponding engineering calculations. (general)

  16. Analytical solution of Fick's law of the TRISO-coated fuel particles and fuel elements in pebble-bed high temperature gas-cooled reactors

    International Nuclear Information System (INIS)

    Two kinds of approaches are built to solve the fission products diffusion models (Fick's equation) based on sphere fuel particles and sphere fuel elements exactly. Two models for homogenous TRISO-coated fuel particles and fuel elements used in pebble-bed high temperature gas-cooled reactors are presented, respectively. The analytical solution of Fick's equation for fission products diffusion in fuel particles is derived by variables separation. In the fuel element system, a modification of the diffusion coefficient from D to D/r is made to characterize the difference of diffusion rates in distinct areas and it is shown that the Laplace and Hankel transformations are effective as the diffusion coefficient in Fick's equation is dependant on the radius of the fuel element. Both the solutions are useful for the prediction of the fission product behaviors and could be programmed in the corresponding engineering calculations. (authors)

  17. Analytical Solution of Fick's Law of the TRISO-Coated Fuel Particles and Fuel Elements in Pebble-Bed High Temperature Gas-Cooled Reactors

    Institute of Scientific and Technical Information of China (English)

    CAO Jian-Zhu; FANG Chao; SUN Li-Feng

    2011-01-01

    T wo kinds of approaches are built to solve the fission products diffusion models (Fick's equation) based on sphere fuel particles and sphere fuel elements exactly. Two models for homogenous TRISO-coated fuel particles and fuel elements used in pebble-bed high temperature gas-cooled reactors are presented, respectively. The analytica,solution of Fick's equation for fission products diffusion in fuel particles is derived by variables separation.In the fuel element system, a modification of the diffusion coefficient from D to D/r is made to characterize the difference of diffusion rates in distinct areas and it is shown that the Laplace and Hankel transformations are effective as the diffusion coefficient in Fick's equation is dependant on the radius of the fuel element. Both the solutions are useful for the prediction of the fission product behaviors and could be programmed in the corresponding engineering calculations.%@@ Two kinds of approaches are built to solve the fission products diffusion models(Fick's equation) based on sphere fuel particles and sphere fuel elements exactly.Two models for homogenous TRISO-coated fuel particles and fuel elements used in pebble-bed high temperature gas-cooled reactors are presented,respectively.The analytical solution of Fick's equation for fission products diffusion in fuel particles is derived by variables separation.In the fuel element system,a modification of the diffusion coefficient from D to D/r is made to characterize the difference of diffusion rates in distinct areas and it is shown that the Laplace and Hankel transformations are effective as the diffusion coefficient in Fick's equation is dependant on the radius of the fuel element.Both the solutions are useful for the prediction of the fission product behaviors and could be programmed in the corresponding engineering calculations.

  18. 球床型固体燃料熔盐堆计算软件开发%Software Development for Pebble-bed MSR Calculation

    Institute of Scientific and Technical Information of China (English)

    庄坤; 曹良志; 吴宏春; 郑友琦

    2013-01-01

    Molten salt reactor (MSR ) , the unique liquid fuel reactor in the fourth generation nuclear power system , has great advantages in terms of inherent safety , neutron economy ,nuclear non-proliferation ,nuclear waste transmutation and thorium fuel breeding ,compared with other solid fuel reactors .At present ,there are two main types of molten salt reactor in domestic:Hexagonal assembly MSR and pebble-bed MSR .In this paper , the pebble-bed MSR fuel sphere homogenization method was studied with double heterogeneity characteristics taken into consideration ,and the core fuel management code BORAGE was developed based on SIXTUS 3-D hexagonal node diffusion code . Numerical results suggest that the developed code achieves good accuracy ,efficiency and can be used in MSR steady analytical calculation .%熔盐堆是第四代核能系统中唯一的液体燃料反应堆,在安全性、经济性、核不扩散、核废料嬗变和钍燃料增殖特性方面与其他反应堆相比具有很大的优势。目前国内的熔盐堆主要有两种堆型:液态燃料熔盐堆和球床式固体燃料熔盐堆。本文考虑到球床熔盐堆燃料球的双重非均匀性特点研究了其组件均匀化方法。基于SISXTUS三维六角形节块程序开发了堆芯燃料管理程序BORAGE ,并进行了数值验证。验证结果表明,本文所开发的程序具有很好的精度和效率,可用于熔盐堆稳态计算。

  19. Influence of power level and fuel type on safety and economy of the simplified pebble bed HTR concept

    International Nuclear Information System (INIS)

    For three different power levels, 20, 40 and 150 MWth, the PAP-HTR has been studied. This is an HTR Module concept that has been simplified in such a way that the continuously defuelling system has been eliminated and no defuelling takes place during a period of several years. Two core heatup scenarios have been simulated. It has been shown that in all cases the maximum fuel pebble temperature remains below 1600C, the temperature above which fuel degradation would start to occur, also after the reactor has gone critical again and the power level has been stabilized by itself. Fuel and gas temperature distributions are compared as well. The maximum pebble temperature before recriticality is higher for the loss of coolant (LOCA) scenario than for the loss of flow (LOFA) case, but the equilibrium maximum temperature after recriticality turns out to be higher for the pressurized case, because of the higher equilibrium power level. The equilibrium power level is a much smaller fraction of the nominal power level for the large 150 MWth system than for the smaller systems, due to the lower rate of cooling down of the large system after initiation of the accident. Therefore the equilibrium maximum temperature stays within acceptable limits for the large system too. The effects of the use of thorium fuel on the core height and waste radiotoxicity have been compared with the case of uranium fuel. Although it is widely believed that burnt thorium fuel would be cleaner than spent uranium fuel in terms of radiotoxicity, this did not appear to be more pronounced for this reactor concept than for e.g. PWRs. The relationship of power level and energy price is obvious for this power range. The use of thorium with highly enriched uranium could bring an additional economical advantage because of the lower core height needed for the same power level as the uranium case. With thorium a higher burnup can be attained, through which fuel pebbles can be added at a slower rate. The size of

  20. HTR-Proteus Pebble Bed Experimental Program Cores 5,6,7,&8: Columnar Hexagonal Point-on-Point Packing with a 1:2 Moderator-to-Fuel Pebble Ratio

    Energy Technology Data Exchange (ETDEWEB)

    Bess, John D. [Idaho National Lab. (INL), Idaho Falls, ID (United States); Sterbentz, James W. [Idaho National Lab. (INL), Idaho Falls, ID (United States); Snoj, Luka [Idaho National Lab. (INL), Idaho Falls, ID (United States); Lengar, Igor [Idaho National Lab. (INL), Idaho Falls, ID (United States); Koberl, Oliver [Idaho National Lab. (INL), Idaho Falls, ID (United States)

    2015-03-01

    PROTEUS is a zero-power research reactor based on a cylindrical graphite annulus with a central cylindrical cavity. The graphite annulus remains basically the same for all experimental programs, but the contents of the central cavity are changed according to the type of reactor being investigated. Through most of its service history, PROTEUS has represented light-water reactors, but from 1992 to 1996 PROTEUS was configured as a pebble-bed reactor (PBR) critical facility and designated as HTR-PROTEUS. The nomenclature was used to indicate that this series consisted of High Temperature Reactor experiments performed in the PROTEUS assembly. During this period, seventeen critical configurations were assembled and various reactor physics experiments were conducted. These experiments included measurements of criticality, differential and integral control rod and safety rod worths, kinetics, reaction rates, water ingress effects, and small sample reactivity effects (Ref. 3). HTR-PROTEUS was constructed, and the experimental program was conducted, for the purpose of providing experimental benchmark data for assessment of reactor physics computer codes. Considerable effort was devoted to benchmark calculations as a part of the HTR-PROTEUS program. References 1 and 2 provide detailed data for use in constructing models for codes to be assessed. Reference 3 is a comprehensive summary of the HTR-PROTEUS experiments and the associated benchmark program. This document draws freely from these references. Only Cores 9 and 10 are evaluated in this benchmark report due to similarities in their construction. The other core configurations of the HTR-PROTEUS program are evaluated in their respective reports as outlined in Section 1.0. Cores 9 and 10 were evaluated and determined to be acceptable benchmark experiments.

  1. HTR-PROTEUS PEBBLE BED EXPERIMENTAL PROGRAM CORES 5, 6, 7, & 8: COLUMNAR HEXAGONAL POINT-ON-POINT PACKING WITH A 1:2 MODERATOR-TO-FUEL PEBBLE RATIO

    Energy Technology Data Exchange (ETDEWEB)

    John D. Bess

    2013-03-01

    PROTEUS is a zero-power research reactor based on a cylindrical graphite annulus with a central cylindrical cavity. The graphite annulus remains basically the same for all experimental programs, but the contents of the central cavity are changed according to the type of reactor being investigated. Through most of its service history, PROTEUS has represented light-water reactors, but from 1992 to 1996 PROTEUS was configured as a pebble-bed reactor (PBR) critical facility and designated as HTR-PROTEUS. The nomenclature was used to indicate that this series consisted of High Temperature Reactor experiments performed in the PROTEUS assembly. During this period, seventeen critical configurations were assembled and various reactor physics experiments were conducted. These experiments included measurements of criticality, differential and integral control rod and safety rod worths, kinetics, reaction rates, water ingress effects, and small sample reactivity effects (Ref. 3). HTR-PROTEUS was constructed, and the experimental program was conducted, for the purpose of providing experimental benchmark data for assessment of reactor physics computer codes. Considerable effort was devoted to benchmark calculations as a part of the HTR-PROTEUS program. References 1 and 2 provide detailed data for use in constructing models for codes to be assessed. Reference 3 is a comprehensive summary of the HTR-PROTEUS experiments and the associated benchmark program. This document draws freely from these references. Only Cores 9 and 10 are evaluated in this benchmark report due to similarities in their construction. The other core configurations of the HTR-PROTEUS program are evaluated in their respective reports as outlined in Section 1.0. Cores 9 and 10 were evaluated and determined to be acceptable benchmark experiments.

  2. Large modular pebble-bed reactors with passive safety properties as a contribution for catastrophe-free nuclear technology. Flexibility in design and application

    International Nuclear Information System (INIS)

    Worldwide investigations are carried out for different reactor concepts, in order to realize nuclear energy production in modular power plants. In that concept several small or middle sized reactors are joined together in a modular way to form one power plant. The size of MODUL-reactors is designed in such a way, that exclusively inherent safety properties perform the control of accidents without active technical proceedings. In order to achieve this, the reactor should be relatively small. On the other hand, it should be relatively large for economic and competitive reasons. The range of possible development of the modular pebble-bed reactor for raising the power output are discussed in this study. Based on the MODUL 200 MW concept, the design of the 'Great-Modul-Medul' reactor (GMM) with a power output of 500 MWth is introduced, in which the loading modus MEDUL is applied with repeated circulation of the spheres through the core. A 'Great-Modul-OTTO' GMO with a power output of 400 MWth is designed with only one pass of the pebbles (OTTO). In comparison to the GMM, that has the advantage of being simpler in construction and in the method of operation. Furthermore, another simplification is studied consisting of the combination (PO) of 'Peu a Peu' and 'OTTO' loading modus. All designed cases show a favourable flexibility when changing the application of the reactor from steam cycle to gas turbine cycle or to seawater desalination. The study outlines, that the inherently determined limitation of the excess temperature in case of a loss coolant accident and the ability for controling the water ingress reactivity are maintained for all variants being considered. (orig.)

  3. Modelling of HTR (High Temperature Reactor Pebble-Bed 10 MW to Determine Criticality as A Variations of Enrichment and Radius of the Fuel (Kernel With the Monte Carlo Code MCNP4C

    Directory of Open Access Journals (Sweden)

    Hammam Oktajianto

    2014-12-01

    Full Text Available Gas-cooled nuclear reactor is a Generation IV reactor which has been receiving significant attention due to many desired characteristics such as inherent safety, modularity, relatively low cost, short construction period, and easy financing. High temperature reactor (HTR pebble-bed as one of type of gas-cooled reactor concept is getting attention. In HTR pebble-bed design, radius and enrichment of the fuel kernel are the key parameter that can be chosen freely to determine the desired value of criticality. This paper models HTR pebble-bed 10 MW and determines an effective of enrichment and radius of the fuel (Kernel to get criticality value of reactor. The TRISO particle coated fuel particle which was modelled explicitly and distributed in the fuelled region of the fuel pebbles using a Simple-Cubic (SC lattice. The pebble-bed balls and moderator balls distributed in the core zone using a Body-Centred Cubic lattice with assumption of a fresh fuel by the fuel enrichment was 7-17% at 1% range and the size of the fuel radius was 175-300 µm at 25 µm ranges. The geometrical model of the full reactor is obtained by using lattice and universe facilities provided by MCNP4C. The details of model are discussed with necessary simplifications. Criticality calculations were conducted by Monte Carlo transport code MCNP4C and continuous energy nuclear data library ENDF/B-VI. From calculation results can be concluded that an effective of enrichment and radius of fuel (Kernel to achieve a critical condition was the enrichment of 15-17% at a radius of 200 µm, the enrichment of 13-17% at a radius of 225 µm, the enrichments of 12-15% at radius of 250 µm, the enrichments of 11-14% at a radius of 275 µm and the enrichment of 10-13% at a radius of 300 µm, so that the effective of enrichments and radii of fuel (Kernel can be considered in the HTR 10 MW. Keywords—MCNP4C, HTR, enrichment, radius, criticality 

  4. Pebble Bed Reactor Power Systems for Lunar Outposts: Long Operation Life and End-of Life Storage

    Science.gov (United States)

    El-Genk, Mohamed S.; Schriener, Timothy M.

    2010-09-01

    The Pellet Bed Reactor(PeBR) and power system for supporting future lunar outposts offer many desirable design, operation and safety features and address post operation storage of spent nuclear fuel. In addition to its long, full power operation life of 66 year, the PeBR is launched without fuel and loaded after placement below grade on the lunar surface with spherical fuel pellets, designed to fully contain fission products. The fuel pellets(~1.0 cm dia.) are launched separately in subcritical canisters. The post-operation PeBR is stored below grade for > 300 year to allow the radioactivity in the spent fuel to decay to a sufficiently low level. The PeBR power system, designed for avoidance of single point failures in reactor cooling and energy conversion, nominally generates ~100 kWe at a thermal efficiency of ~ 21%. In addition to the sectored reactor core, it uses three Closed Brayton Cycle loops with centrifugal flow turbo-machines for energy conversion and He-Xe(40 g/mol) binary gas mixture working fluid and reactor coolant.

  5. Development Status of the PEBBLES Code for Pebble Mechanics: Improved Physical Models and Speed-up

    International Nuclear Information System (INIS)

    PEBBLES is a code for simulating the motion of all the pebbles in a pebble bed reactor. Since pebble bed reactors are packed randomly and not precisely placed, the location of the fuel elements in the reactor is not deterministically known. Instead, when determining operating parameters the motion of the pebbles can be simulated and stochastic locations can be found. The PEBBLES code can output information relevant for other simulations of the pebble bed reactors such as the positions of the pebbles in the reactor, packing fraction change in an earthquake, and velocity profiles created by recirculation. The goal for this level three milestone was to speedup the PEBBLES code through implementation on massively parallel computer. Work on this goal has resulted in speeding up both the single processor version and creation of a new parallel version of PEBBLES. Both the single processor version and the parallel running capability of the PEBBLES code have improved since the fiscal year start. The hybrid MPI/OpenMP PEBBLES version was created this year to run on the increasingly common cluster hardware profile that combines nodes with multiple processors that share memory and a cluster of nodes that are networked together. The OpenMP portions use the Open Multi-Processing shared memory parallel processing model to split the task across processors in a single node that shares memory. The Message Passing Interface (MPI) portion uses messages to communicate between different nodes over a network. The following are wall clock speed up for simulating an NGNP-600 sized reactor. The single processor version runs 1.5 times faster compared to the single processor version at the beginning of the fiscal year. This speedup is primarily due to the improved static friction model described in the report. When running on 64 processors, the new MPI/OpenMP hybrid version has a wall clock speed up of 22 times compared to the current single processor version. When using 88 processors, a

  6. Quantitative similarity analysis of the fluoride salt-cooled pebble bed reactor with HTR-10 and MSRE%氟盐冷却球床堆与HTR-10和MSRE的定量相似性分析

    Institute of Scientific and Technical Information of China (English)

    杨群; 于世和; 邹杨; 周波; 严睿; 徐洪杰

    2016-01-01

    Background: The fluoride salt-cooled pebble bed reactor which has not yet been built so far is a new international research reactor, so the selection of similar reactors with operation experience as benchmark is one important part of the applicability analysis for its reactor core nuclear design software. Purpose:This study aims to determine quantitatively the rationality of the 10 MW high-temperature gas-cooled test reactor (HTR-10) and the Molten Salt Reactor Experiment (MSRE) to be the benchmarks for the fluoride salt-cooled pebble bed reactor. Methods:The similarities of the fluoride salt-cooled pebble bed reactor with HTR-10 and MSRE were analyzed with the adoption of the similarity analysis software that is often used. Results: The results show that the fluoride salt-cooled pebble bed reactor and MSRE have a high similarity because they have the close spectrum peak energies and almost the same elements in core. The fluoride salt-cooled pebble bed reactor and HTR-10 have the different coolant and more differences in spectrum peak energies, hence the low similarity. Conclusion: MSRE is an ideal benchmark of the reactor core nuclear design software for the fluoride salt-cooled pebble bed reactor.%氟盐冷却球床堆是当前国际上一种新的研究堆型,尚无已经建造完成的反应堆,因此,选择相似且具有运行经验的反应堆作为基准题有助于堆芯核设计软件适用性分析。利用国际上常采用的相似性分析软件,可对熔盐实验堆(Molten Salt Reactor Experiment, MSRE)及10 MW高温气冷堆(10 MW high-temperature gas-cooled test reactor, HTR-10)与氟盐冷却球床堆的相似性进行分析,定量判断它们作为基准题的合理性。分析结果表明, MSRE和氟盐冷却球床堆的能谱峰位能量接近且堆内元素种类相近,二者相似程度较高;常温临界HTR-10和氟盐冷却球床堆冷却剂不同,且能谱峰位能量差异较大,二者相似程

  7. Image reconstruction of single photon emission computed tomography (SPECT) on a pebble bed reactor (PBR) using expectation maximization and exact inversion algorithms: Comparison study by means of numerical phantom

    Science.gov (United States)

    Razali, Azhani Mohd; Abdullah, Jaafar

    2015-04-01

    Single Photon Emission Computed Tomography (SPECT) is a well-known imaging technique used in medical application, and it is part of medical imaging modalities that made the diagnosis and treatment of disease possible. However, SPECT technique is not only limited to the medical sector. Many works are carried out to adapt the same concept by using high-energy photon emission to diagnose process malfunctions in critical industrial systems such as in chemical reaction engineering research laboratories, as well as in oil and gas, petrochemical and petrochemical refining industries. Motivated by vast applications of SPECT technique, this work attempts to study the application of SPECT on a Pebble Bed Reactor (PBR) using numerical phantom of pebbles inside the PBR core. From the cross-sectional images obtained from SPECT, the behavior of pebbles inside the core can be analyzed for further improvement of the PBR design. As the quality of the reconstructed image is largely dependent on the algorithm used, this work aims to compare two image reconstruction algorithms for SPECT, namely the Expectation Maximization Algorithm and the Exact Inversion Formula. The results obtained from the Exact Inversion Formula showed better image contrast and sharpness, and shorter computational time compared to the Expectation Maximization Algorithm.

  8. AVR RISC microcontroller handbook

    CERN Document Server

    Kuhnel, Claus

    1998-01-01

    The AVR RISC Microcontroller Handbook is a comprehensive guide to designing with Atmel's new controller family, which is designed to offer high speed and low power consumption at a lower cost. The main text is divided into three sections: hardware, which covers all internal peripherals; software, which covers programming and the instruction set; and tools, which explains using Atmel's Assembler and Simulator (available on the Web) as well as IAR's C compiler.Practical guide for advanced hobbyists or design professionalsDevelopment tools and code available on the Web

  9. Behavior of beryllium pebbles under irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Dalle-Donne, M.; Scaffidi-Argentina, F. [Forschungszentrum Karlsruhe GmbH Technik und Umwelt (Germany). Inst. fuer Neutronenphysik und Reactortechnik; Baldwin, D.L.; Gelles, D.S.; Greenwood, L.R.; Kawamura, H.; Oliver, B.M.

    1998-01-01

    Beryllium pebbles are being considered in fusion reactor blanket designs as neutron multiplier. An example is the European `Helium Cooled Pebble Bed Blanket.` Several forms of beryllium pebbles are commercially available but little is known about these forms in response to fast neutron irradiation. Commercially available beryllium pebbles have been irradiated to approximately 1.3 x 10{sup 22} n/cm{sup 2} (E>1 MeV) at 390degC. Pebbles 1-mm in diameter manufactured by Brush Wellman, USA and by Nippon Gaishi Company, Japan, and 3-mm pebbles manufactured by Brush Wellman were included. All were irradiated in the below-core area of the Experimental Breeder Reactor-II in Idaho Falls, USA, in molybdenum alloy capsules containing helium. Post-irradiation results are presented on density change measurements, tritium release by assay, stepped-temperature anneal, and thermal ramp desorption tests, and helium release by assay and stepped-temperature anneal measurements, for Be pebbles from two manufacturing methods, and with two specimen diameters. The experimental results on density change and tritium and helium release are compared with the predictions of the code ANFIBE. (author)

  10. 球床高温气冷堆闭式循环特性%Characteristics of closed fuel cycles in the pebble bed high temperature gas cooled reactor

    Institute of Scientific and Technical Information of China (English)

    位金锋; 孙玉良; 李富

    2012-01-01

    The reuse of uranium and plutonium from high temperature gas-cooled reactor(HTGR) spent fuel will improve resource usage and minimize waste.The characteristics of different closed fuel cycles were studied here for uranium and plutonium recycled from 250 MWth high-temperature gas-cooled reactor pebble-bed-module(HTR-PM) spent fuel from a U-Pu fueled core.PuO2 and MOX fuel elements using recycled plutonium and uranium were then used in new PuO2 or MOX fueled cores with the same geometry as the original reactor.PuO2 from LWR spent fuel was also evaluated.The characteristics of the fuel utilization and transuranic incineration in these closed fuel cycles were studied with the VSOP program.The natural uranium utilization closed fuel for these closed fuel cycle is increased by 6%,8% and 20%,while the plutonium burn rates are 40%,41% and 63%,respectively.Thus,these HTGR closed fuel cycles can effectively burn plutonium isotopes and increase natural uranium utilization.%从提高天然铀利用率和改进废物管理方面考虑,研究球床高温气冷堆乏燃料中铀钚的再利用和不同闭式燃料循环的特性。在250MW热功率球床模块式高温气冷堆示范电站铀钚循环的乏燃料中提取铀和钚为核燃料,设计了PuO2和混合氧化物(MOX)燃料元件,将新设计的燃料元件重新装入与示范电站有同样结构和尺寸的堆芯,分别形成纯钚燃料循环和MOX燃料循环。还研究了基于轻水堆级钚的燃料循环。采用了高温气冷堆物理设计程序VSOP,研究了高温气冷堆不同闭式循环的燃料利用和超铀元素焚烧特性。不同闭式循环钚消耗率分别为50%、46%和71%,天然铀的电利用率分别提高了6%、8%和20%。结果表明:高温气冷堆闭式燃料循环能有效焚烧钚同位素,适度提高天然铀的利用率。

  11. 球床式高温气冷堆的余热不确定性分析%Uncertainty Analysis on Decay Heat of Pebble-bed High Temperature Gas-cooled Reactor

    Institute of Scientific and Technical Information of China (English)

    贠相羽; 郑艳华; 经荥清; 李富

    2013-01-01

    反应堆在停堆后相当长时间内仍具有较高的剩余发热是核电站的重要特性,也是核电站安全分析的关键.因此,对反应堆余热及其不确定性进行分析,对于合理设计余热排出系统、研究论证燃料元件在事故后的安全特性等均具有重要意义.本工作结合德国针对球床式高温气冷堆制定的余热计算标准,介绍了球床式高温气冷堆剩余发热及其不确定性的计算方法,并结合200 MWe球床模块式高温气冷堆示范工程(HTR-PM)的初步物理设计,对长期运行在满功率平衡堆芯状态下的反应堆停堆后的余热及其不确定性进行了计算分析,为进一步的事故分析提供依据.%The large amount of decay heat in a quite long time after reactor shutdown,which is an important characteristic of the nuclear power plants,should be considered seriously during the safety analysis.Therefore,the study on the decay heat and its uncertainty analysis play an important role in the design of decay heat removal system,as well as in the safety verification of the fuel element during the accident.In referenced to the standard of Germany entitled "Decay Heat Power in Nuclear Fuels of Hightemperature Reactors with Spherical Fuel Elements" especially for pebble-bed high temperature gas-cooled reactor (HTGR),the calculation method of decay heat and its uncertainty of pebble-bed HTGR were introduced.On the basis of the preliminary physical design of Chinese 200 MWe high temperature gas-cooled reactor pebble-bed module (HTR-PM),the decay heat and its uncertainty after reactor shutdown from long-term operation at rated power were analyzed,so as to provide a basis for further accident analysis.

  12. Analysis of the effect of random errors in burnup measurements in a pebble bed HTR%球床式高温气冷堆燃耗测量随机误差的影响分析

    Institute of Scientific and Technical Information of China (English)

    郝琛; 李富

    2013-01-01

    The fuel pebbles pass through the reactor core several times in a pebble bed high temperature gas cooled reactor (HTR).The burnup of the fuel balls is measured after they are discharged from the core bottom by a burnup measurement device.Those whose burnup does not reach the threshold are returned to the top of the core to pass through the core again,with the others transferred to the spent fuel storage tank.However,these random errors in the burnup measurement affect the fuel cycle.The MCPHS code,which is based on the Monte Carlo method,was used to analyze the characteristics of the pebble bed flow to simulate the random error in burnup measurement and its effect on the fuel cycle.The results show that the average discharge burnup and the distribution of the burnup in the core are not sensitive to the random error,while the distribution of the discharge burnup and the maximum and minimum discharge burnups are particularly sensitive to the random error in the burnup measurement.%球床式高温气冷堆燃料球多次通过堆芯,卸出堆芯的燃料球将由燃耗测量装置测量其燃耗,达到设定阈值的将按乏燃料处理,否则将返回堆芯继续裂变发热.而燃耗测量会具有随机误差,从而可能对燃料循环过程产生影响.该文改进了球床高温气冷堆燃料球运行历史的Monte Carlo模拟程序MCPHS,对燃耗测量的随机误差进行了模拟,对燃料循环过程的影响进行了分析.结果表明卸料燃耗均值、燃料球通过堆芯次数均值、堆芯燃耗分布对于燃耗测量误差并不敏感,而燃料球卸料燃耗分布、卸料燃耗最大值和最小值及燃料球通过堆芯最大值和最小值对于燃耗测量误差很敏感.

  13. "Smart pebble" design for environmental monitoring applications

    Science.gov (United States)

    Valyrakis, Manousos; Pavlovskis, Edgars

    2014-05-01

    Sediment transport, due to primarily the action of water, wind and ice, is one of the most significant geomorphic processes responsible for shaping Earth's surface. It involves entrainment of sediment grains in rivers and estuaries due to the violently fluctuating hydrodynamic forces near the bed. Here an instrumented particle, namely a "smart pebble", is developed to investigate the exact flow conditions under which individual grains may be entrained from the surface of a gravel bed. This could lead in developing a better understanding of the processes involved, while focusing on the response of the particle during a variety of flow entrainment events. The "smart pebble" is a particle instrumented with MEMS sensors appropriate for capturing the hydrodynamic forces a coarse particle might experience during its entrainment from the river bed. A 3-axial gyroscope and accelerometer registers data to a memory card via a microcontroller, embedded in a 3D-printed waterproof hollow spherical particle. The instrumented board is appropriately fit and centred into the shell of the pebble, so as to achieve a nearly uniform distribution of the mass which could otherwise bias its motion. The "smart pebble" is powered by an independent power to ensure autonomy and sufficiently long periods of operation appropriate for deployment in the field. Post-processing and analysis of the acquired data is currently performed offline, using scientific programming software. The performance of the instrumented particle is validated, conducting a series of calibration experiments under well-controlled laboratory conditions. "Smart pebble" allows for a wider range of environmental sensors (e.g. for environmental/pollutant monitoring) to be incorporated so as to extend the range of its application, enabling accurate environmental monitoring which is required to ensure infrastructure resilience and preservation of ecological health.

  14. Pebble Puzzle Solved

    Science.gov (United States)

    2004-01-01

    [figure removed for brevity, see original site] Figure 1 In the quest to determine if a pebble was jamming the rock abrasion tool on NASA's Mars Exploration Rover Opportunity, scientists and engineers examined this up-close, approximate true-color image of the tool. The picture was taken by the rover's panoramic camera, using filters centered at 601, 535, and 482 nanometers, at 12:47 local solar time on sol 200 (August 16, 2004). Colored spots have been drawn on this image corresponding to regions where panoramic camera reflectance spectra were acquired (see chart in Figure 1). Those regions are: the grinding wheel heads (yellow); the rock abrasion tool magnets (green); the supposed pebble (red); a sunlit portion of the aluminum rock abrasion tool housing (purple); and a shadowed portion of the rock abrasion tool housing (brown). These spectra demonstrated that the composition of the supposed pebble was clearly different from that of the sunlit and shadowed portions of the rock abrasion tool, while similar to that of the dust-coated rock abrasion tool magnets and grinding heads. This led the team to conclude that the object disabling the rock abrasion tool was indeed a martian pebble.

  15. Mechanical performance of irradiated beryllium pebbles

    Energy Technology Data Exchange (ETDEWEB)

    Scaffidi-Argentina, F.; Dalle-Donne, M.; Werle, H. [Forschungszentrum Karlsruhe GmbH Technik und Umwelt (Germany). Inst. fuer Neutronenphysik und Reaktortechnik

    1998-01-01

    For the Helium Cooled Pebble Bed (HCPB) Blanket, which is one of the two reference concepts studied within the European Fusion Technology Programme, the neutron multiplier consists of a mixed bed of about 2 and 0.1-0.2 mm diameter beryllium pebbles. Beryllium has no structural function in the blanket, however microstructural and mechanical properties are important, as they might influence the material behavior under neutron irradiation. The EXOTIC-7 as well as the `Beryllium` experiments carried out in the HFR reactor in Petten are considered as the most detailed and significant tests for investigating it. This paper reviews the present status of beryllium post-irradiation examinations performed at the Forschungszentrum Karlsruhe with samples from these irradiation experiments, emphasizing the effects of irradiation of essential material properties and trying to elucidate the processes controlling the property changes. The microstructure, the porosity distribution, the impurity content, the behavior under compression loads and the compatibility of the beryllium pebbles with lithium orthosilicate (Li{sub 4}SiO{sub 4}) during the in-pile irradiation are presented and critically discussed. Qualitative information on ductility and creep obtained by hardness-type measurements are also supplied. (author)

  16. Li ceramic pebbles chemical compatibility with Eurofer samples in fusion relevant conditions

    International Nuclear Information System (INIS)

    Information on the chemical compatibility between Li ceramic breeders and reactor structural materials is an important issue for fusion reactor technology. In this work, Eurofer samples were placed inside a Li ceramic pebble bed and kept at 600 deg. C under a reducing atmosphere obtained by the flow of a purging gas (He + 0.1vol.%H2). Titanate and orthosilicate Li pebble beds were used in the experiments and exposure time ranged from 50 to 2000 h. Surface chemical reactions were investigated with nuclear microprobe techniques. The orthosilicate pebbles present chemical reactions even with the gas mixture, whereas for the samples in close contact with Eurofer there is evidence of Eurofer elemental diffusion into the pebbles and the formation of different types of compounds. Although the titanate pebbles used in the chemical compatibility experiments present surface alterations with increasing surface irregularities along the annealing time, there is no clear indication of Eurofer constituents diffusion

  17. Fuel cycle of the AVR

    International Nuclear Information System (INIS)

    All the stages of development were secured by irradiation tests and by the use of the elements concerned in the AVR. Summarising, these were: The first charge with fuel elements from Union Carbide, with U-Th mixed carbide particles, wallpaper variants, U-Th mixed carbide particles, the pressed fuel element with U-Th mixed carbide particles, the pressed fuel element with U-Th mixed oxide particles, with an intermediate boundary layer; the present THTR element, the pressed fuel element with U-Th mixed oxide particles and low temperature PyC coating, the pressed fuel element with U-Th mixed oxide particles, with PyC and SiC layers, i.e.: TRISO particles, the pressed fuel element with pure uranium oxide particles for the low enrichment cycle, one coated only by 2 PyC layers, the other coated with PyC and SiC, i.e.: TRISO coating. (orig.)

  18. Tritium release from highly neutron irradiated constrained and unconstrained beryllium pebbles

    Energy Technology Data Exchange (ETDEWEB)

    Chakin, V., E-mail: vladimir.chakin@kit.edu; Rolli, R.; Vladimirov, P.; Moeslang, A.

    2015-06-15

    Highlights: • For the irradiated constrained beryllium pebbles, the tritium release occurs easier than for the unconstrained ones. • Tritium retention in the irradiated constrained and unconstrained beryllium pebbles decreases with increasing irradiation temperature. • Formation of sub-grains in the constrained beryllium pebbles facilitate the open porosity network formation. - Abstract: Beryllium is the reference neutron multiplier material in the Helium Cooled Pebble Bed (HCPB) breeding blanket of fusion power plants. Significant tritium inventory accumulated in beryllium as a result of neutron-induced transmutations could become a safety issue for the operation of such blankets as well as for the nuclear waste utilization. To provide a related materials database, a neutron irradiation campaign of beryllium pebbles with diameters of 0.5 and 1 mm at 686–1006 K, the HIDOBE-01 experiment, has been performed in the HFR in Petten, the Netherlands, producing up to 3020 appm helium and 298 appm tritium. Thermal desorption tests of irradiated unconstrained and constrained beryllium pebbles were performed in a purge gas flow using a quadrupole mass-spectrometer (QMS) and an ionization chamber. Compared to unconstrained pebbles, constrained beryllium pebbles have an enhanced tritium release at all temperatures investigated. Small elongated sub-grains formed under irradiation in the constrained pebbles promote formation of numerous channels for facilitated tritium release.

  19. From Pebbles to Planets

    Science.gov (United States)

    Johansen, Anders

    2013-10-01

    Planets form in protoplanetary discs around young stars as dust and ice particles collide to form ever larger bodies. Particle concentration in the turbulent gas flow may be necessary to form the planetesimals which are the building blocks of both the terrestrial planets and the cores of the gas giants and the ice giants. The streaming instability, which feeds off the relative motion of gas and particles, is a powerful mechanism to create overdense particle filaments. These filaments contract under their own gravity to form planetesimals with a wide range of sizes. I will also discuss how the pebbles left over from the planetesimal formation stage can lead to rapid formation of the cores of gas giants, well within the protoplanetary disc life-time, even in wide orbits.

  20. High temperature gas-cooled reactor (HTGR) graphite pebble fuel: Review of technologies for reprocessing

    Energy Technology Data Exchange (ETDEWEB)

    Mcwilliams, A. J. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL)

    2015-09-08

    This report reviews literature on reprocessing high temperature gas-cooled reactor graphite fuel components. A basic review of the various fuel components used in the pebble bed type reactors is provided along with a survey of synthesis methods for the fabrication of the fuel components. Several disposal options are considered for the graphite pebble fuel elements including the storage of intact pebbles, volume reduction by separating the graphite from fuel kernels, and complete processing of the pebbles for waste storage. Existing methods for graphite removal are presented and generally consist of mechanical separation techniques such as crushing and grinding chemical techniques through the use of acid digestion and oxidation. Potential methods for reprocessing the graphite pebbles include improvements to existing methods and novel technologies that have not previously been investigated for nuclear graphite waste applications. The best overall method will be dependent on the desired final waste form and needs to factor in the technical efficiency, political concerns, cost, and implementation.

  1. TEM study of impurity segregations in beryllium pebbles

    Energy Technology Data Exchange (ETDEWEB)

    Klimenkov, M., E-mail: michael.klimenkov@kit.edu [Institute for Applied Materials – Applied Materials Physics, Karlsruhe Institute of Technology, Hermann-von-Helmholz-Platz 1, 76344 Eggenstein-Leopoldshafen (Germany); Chakin, V.; Moeslang, A. [Institute for Applied Materials – Applied Materials Physics, Karlsruhe Institute of Technology, Hermann-von-Helmholz-Platz 1, 76344 Eggenstein-Leopoldshafen (Germany); Rolli, R. [Institute for Applied Materials – Materials and Biomechanics, Karlsruhe Institute of Technology, Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen (Germany)

    2014-12-15

    Beryllium is planned to be used as a neutron multiplier in the Helium-cooled Pebble Bed European concept of a breeding blanket of demonstration power reactor DEMO. In order to evaluate the irradiation performance, individual pebbles and constrained pebble beds were neutron-irradiated at temperatures typical of fusion blankets. Beryllium pebbles 1 mm in diameter produced by the rotating electrode method were subjected to a TEM study before and after irradiation at High Flux Reactor, Petten, Netherlands at 861 K. The grain size varied in a wide range from sub-micron size up to several tens of micrometers, which indicated formation bimodal grain size distribution. Based on the application of combined electron energy loss spectroscopy and energy dispersive X-ray spectroscopy methods, we suggest that impurity precipitates play an important role in controlling the mechanical properties of beryllium. The impurity elements were present in beryllium at a sub-percent concentration form beryllide particles of a complex (Fe/Al/Mn/Cr)B composition. These particles are often ordered along dislocations lines, forming several micron-long chains. It can be suggested that fracture surfaces often extended along these chains in irradiated material.

  2. TEM study of impurity segregations in beryllium pebbles

    Science.gov (United States)

    Klimenkov, M.; Chakin, V.; Moeslang, A.; Rolli, R.

    2014-12-01

    Beryllium is planned to be used as a neutron multiplier in the Helium-cooled Pebble Bed European concept of a breeding blanket of demonstration power reactor DEMO. In order to evaluate the irradiation performance, individual pebbles and constrained pebble beds were neutron-irradiated at temperatures typical of fusion blankets. Beryllium pebbles 1 mm in diameter produced by the rotating electrode method were subjected to a TEM study before and after irradiation at High Flux Reactor, Petten, Netherlands at 861 K. The grain size varied in a wide range from sub-micron size up to several tens of micrometers, which indicated formation bimodal grain size distribution. Based on the application of combined electron energy loss spectroscopy and energy dispersive X-ray spectroscopy methods, we suggest that impurity precipitates play an important role in controlling the mechanical properties of beryllium. The impurity elements were present in beryllium at a sub-percent concentration form beryllide particles of a complex (Fe/Al/Mn/Cr)B composition. These particles are often ordered along dislocations lines, forming several micron-long chains. It can be suggested that fracture surfaces often extended along these chains in irradiated material.

  3. Pebble Fuel Handling and Reactivity Control for Salt-Cooled High Temperature Reactors

    Energy Technology Data Exchange (ETDEWEB)

    Peterson, Per [Univ. of California, Berkeley, CA (United States). Dept. of Nuclear Engineering; Greenspan, Ehud [Univ. of California, Berkeley, CA (United States). Dept. of Nuclear Engineering

    2015-02-09

    This report documents the work completed on the X-PREX facility under NEUP Project 11- 3172. This project seeks to demonstrate the viability of pebble fuel handling and reactivity control for fluoride salt-cooled high-temperature reactors (FHRs). The research results also improve the understanding of pebble motion in helium-cooled reactors, as well as the general, fundamental understanding of low-velocity granular flows. Successful use of pebble fuels in with salt coolants would bring major benefits for high-temperature reactor technology. Pebble fuels enable on-line refueling and operation with low excess reactivity, and thus simpler reactivity control and improved fuel utilization. If fixed fuel designs are used, the power density of salt- cooled reactors is limited to 10 MW/m3 to obtain adequate duration between refueling, but pebble fuels allow power densities in the range of 20 to 30 MW/m3. This can be compared to the typical modular helium reactor power density of 5 MW/m3. Pebble fuels also permit radial zoning in annular cores and use of thorium or graphite pebble blankets to reduce neutron fluences to outer radial reflectors and increase total power production. Combined with high power conversion efficiency, compact low-pressure primary and containment systems, and unique safety characteristics including very large thermal margins (>500°C) to fuel damage during transients and accidents, salt-cooled pebble fuel cores offer the potential to meet the major goals of the Advanced Reactor Concepts Development program to provide electricity at lower cost than light water reactors with improved safety and system performance.This report presents the facility description, experimental results, and supporting simulation methods of the new X-Ray Pebble Recirculation Experiment (X-PREX), which is now operational and being used to collect data on the behavior of slow dense granular flows relevant to pebble bed reactor core designs. The X

  4. A linear optimization technique for graph pebbling

    CERN Document Server

    Hurlbert, Glenn

    2011-01-01

    Graph pebbling is a network model for studying whether or not a given supply of discrete pebbles can satisfy a given demand via pebbling moves. A pebbling move across an edge of a graph takes two pebbles from one endpoint and places one pebble at the other endpoint; the other pebble is lost in transit as a toll. It has been shown that deciding whether a supply can meet a demand on a graph is NP-complete. The pebbling number of a graph is the smallest t such that every supply of t pebbles can satisfy every demand of one pebble. Deciding if the pebbling number is at most k is \\Pi_2^P-complete. In this paper we develop a tool, called the Weight Function Lemma, for computing upper bounds and sometimes exact values for pebbling numbers with the assistance of linear optimization. With this tool we are able to calculate the pebbling numbers of much larger graphs than in previous algorithms, and much more quickly as well. We also obtain results for many families of graphs, in many cases by hand, with much simpler and...

  5. Evidence for Pebbles in Comets

    CERN Document Server

    Kretke, K A

    2015-01-01

    When the EPOXI spacecraft flew by Comet 103P/Hartley 2, it observed large particles floating around the comet nucleus. These particles are likely low-density, centimeter- to decimeter-sized clumps of ice and dust. While the origin of these objects remains somewhat mysterious, it is possible that they are giving us important information about the earliest stages of our Solar System's formation. Recent advancements in planet formation theory suggest that planetesimals (or cometestimals) may grow directly from the gravitational collapse of aerodynamically concentrated small particles, often referred to as "pebbles." Here we show that the particles observed in the coma of 103P are consistent with the sizes of pebbles expected to efficiently form planetesimals in the region that this comet likely formed, while smaller pebbles are may be expected in the majority of comets, whose chemistry is often indicative of formation in the colder, outer regions of the protoplanetary disk.

  6. TEM study of beryllium pebbles after neutron irradiation up to 3000 appm helium production

    Energy Technology Data Exchange (ETDEWEB)

    Klimenkov, M., E-mail: michael.klimenkov@kit.edu [Institute for Applied Materials – Applied Materials Physics, Karlsruhe Institute of Technology, Hermann-von-Helmholz-Platz 1, 76344 Eggenstein-Leopoldshafen (Germany); Chakin, V.; Moeslang, A. [Institute for Applied Materials – Applied Materials Physics, Karlsruhe Institute of Technology, Hermann-von-Helmholz-Platz 1, 76344 Eggenstein-Leopoldshafen (Germany); Rolli, R. [Institute for Applied Materials – Materials and Biomechanics, Karlsruhe Institute of Technology, Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen (Germany)

    2013-11-15

    Beryllium is planned to be used as a neutron multiplier in the Helium Cooled Pebble Bed (HCPB) European concept of a breeding blanket of DEMO. In order to evaluate the irradiation performance, individual pebbles and constrained pebble beds were neutron irradiated at temperatures typical for fusion blanket. Beryllium pebbles with a diameter of 1 mm produced by the Rotating Electrode Method were subjected to a TEM study after irradiation at the HFR, Petten, at temperatures of 686, 753, 861, and 968 K. The helium production in the pebbles was calculated in the range from 2090 to 3090 appm. Gas bubbles as disks of hexagonal shape were observed for all four irradiation temperatures. The disks were oriented in the (0 0 0 1) basal plane with a height directed along the [0 0 0 1] “c” axis. The average diameters of the bubbles increase from 7.5 to 80 nm with increasing irradiation temperature, the bulk densities accordingly decrease from 4.4 × 10{sup 22} to 3.8 × 10{sup 20} m{sup −3}. With increasing irradiation temperature, the swelling of the pebbles increases from 0.6% at 686 K up to 6.5% at 968 K.

  7. Progress in the development of Li{sub 2}ZrO{sub 3} and Li{sub 2}TiO{sub 3} pebbles

    Energy Technology Data Exchange (ETDEWEB)

    Lulewicz, J.D.; Roux, N. [CEA Centre d`Etudes de Saclay, 91 - Gif-sur-Yvette (France)

    1998-03-01

    Li{sub 2}ZrO{sub 3} and Li{sub 2}TiO{sub 3} pebbles are being developed as ceramic breeder for the European Helium-cooled pebble bed DEMO blanket concept. Status is given of the fabrication work, and of the properties characteristics determination. (author)

  8. A smoother pebble mathematical explorations

    CERN Document Server

    Benson, Donald C

    2003-01-01

    Introduction. I. BRIDGING THE GAP. 1. The Ancient Fractions. 2. Greek Gifts. 3. The Music of the Ratios. II. THE SHAPE OF THINGS. 4. Tubeland. 5. The Calculating Eye. III. THE GREAT ART. 6. Algebra Rules. 7. The Root of the Problem. 8. Symmetry Without Fear. 9. The Magic Mirror. IV. A SMOOTHER PEBBLE. 10. On the Shoulders of Giants. 11. Six-Minute Calculus. 12. Roller-Coaster Science. Glossary. References. Index

  9. Electrical behaviour of ceramic breeder blankets in pebble form after γ-radiation

    Directory of Open Access Journals (Sweden)

    E. Carella

    2015-07-01

    Full Text Available Lithium orthosilicate (Li4SiO4 ceramics in from of pebble bed is the European candidate for ITER testing HCPB (Helium Cooled Pebble Bed breeding modules. The breeder function and the shielding role of this material, represent the areas upon which attention is focused. Electrical measurements are proposed for monitoring the modification created by ionizing radiation and at the same time provide information on lithium movement in this ceramic structure. The electrical tests are performed on pebbles fabricated by Spray-dryer method before and after gamma-irradiation through a 60Co source to a fluence of 4.8 Gy/s till a total dose of 5 ∗ 105 Gy. The introduction of thermal annealing treatments during the electrical impedance spectroscopy (EIS measurements points out the recombination effect of the temperature on the γ-induced defects.

  10. Information from water ingress accident on AVR

    International Nuclear Information System (INIS)

    An ingress of water occurred in the AVR reactor in May 1978. The reactor had been shut down and cooled by forced circulation; liquid water entered the primary circuit from a leak in the superheater, evaporated in passing through the core and condensed in the lower part of the primary circuit and in the ball handling region. Various fission product activities were measured in the water by the AVR scientists and a study was started to identify the sources of these activities and to derive information which could be used in the analyses of water ingress accidents in general. The first part of this study is reported in this note. The possible source terms are considered separately and estimates of their contributions are made, supported by data from previous laboratory experiments where possible. The main conclusion is that valuable information has been derived concerning the desorption of iodine, cesium and strontium from dust and primary circuit surfaces. A minimum programme of measurements and analytical work necessary to increase this information has been identified. An example of the application of the data to a particular accident to a power reactor is given to indicate how the information can affect the calculation of consequences. For the second part of the study, better estimates of the fission product concentrations in the primary circuit prior to the accident and various measurements when the reactor is operating again are required. (orig.)

  11. Postirradiation examination of beryllium pebbles

    Energy Technology Data Exchange (ETDEWEB)

    Gelles, D.S. [Pacific Northwest National Lab., Richland, WA (United States)

    1998-03-01

    Postirradiation examinations of COBRA-1A beryllium pebbles irradiated in the EBR-II fast reactor at neutron fluences which generated 2700--3700 appm helium have been performed. Measurements included density change, optical microscopy, scanning electron microscopy, and transmission electron microscopy. The major change in microstructure is development of unusually shaped helium bubbles forming as highly non-equiaxed thin platelet-like cavities on the basal plane. Measurement of the swelling due to cavity formation was in good agreement with density change measurements.

  12. Pebble red modular reactor - South Africa

    International Nuclear Information System (INIS)

    In 1995 the South African Electricity Utility, ESKOM, was convinced of the economical advantages of high temperature gas-cooled reactors as viable supply side option. Subsequently planning of a techno/economic study for the year 1996 was initiated. Continuation to the construction phase of a prototype plant will depend entirely on the outcome of this study. A reactor plant of pebble bed design coupled with a direct helium cycle is perceived. The electrical output is limited to about 100 MW for reasons of safety, economics and flexibility. Design of the reactor will be based on internationally proven, available technology. An extended research and development program is not anticipated. New licensing rules and regulations will be required. Safety classification of components will be based on the merit of HTGR technology rather than attempting to adhere to traditional LWR rules. A medium term time schedule for the design and construction of a prototype plant, commissioning and performance testing is proposed during the years 2002 and 2003. Pending the performance outcome of this plant and the current power demand, series production of 100 MWe units is foreseen. (author)

  13. Formation of pebble-pile planetesimals

    CERN Document Server

    Jansson, Karl Wahlberg

    2014-01-01

    The first stage of planet formation is the accumulation of dust and ice grains into mm-cm-sized pebbles. These pebbles can clump together through the streaming instability and form gravitationally bound pebble 'clouds'. Pebbles inside such a cloud will undergo mutual collisions, dissipating energy into heat. As the cloud loses energy, it gradually contracts towards solid density. We model this process and investigate two important properties of the collapse: (i) the timescale of the collapse and (ii) the temporal evolution of the pebble size distribution. Our numerical model of the pebble cloud is zero-dimensional and treats collisions with a statistical method. We find that planetesimals with radii larger than 100 km collapse on the free-fall timescale of about 25 years. Lower-mass clouds have longer pebble collision timescales and collapse much more slowly, with collapse times of a few hundred years for 10-km-scale planetesimals and a few thousand years for 1-km-scale planetesimals. The mass of the pebble c...

  14. Genetics of avirulence genes in Blumeria graminis f.sp. hordei and physical mapping of AVR(a22) and AVR(a12).

    Science.gov (United States)

    Skamnioti, Pari; Pedersen, Carsten; Al-Chaarani, Ghias R; Holefors, Anna; Thordal-Christensen, Hans; Brown, James K M; Ridout, Christopher J

    2008-03-01

    Powdery mildew fungi are parasites that cause disease on a wide range of important crops. Plant resistance (R) genes, which induce host defences against powdery mildews, encode proteins that recognise avirulence (AVR) molecules from the parasite in a gene-for-gene manner. To gain insight into how virulence evolves in Blumeria graminis f.sp. hordei, associations between segregating AVR genes were established. As a prerequisite to the isolation of AVR genes, two loci were selected for further analysis. AVR(a22) is located in a tightly linked cluster comprising AVR(a10) and AVR(k1) as well as up to five other AVR genes. The ratio between physical and genetic distance in the cluster ranged between 0.7 and 35 kB/cM. The AVR(a22) locus was delimited by the previously isolated gene AVR(a10) and two cleaved amplified polymorphic sequence (CAPS) markers, 19H12R and 74E9L. By contrast, AVR(a12) was not linked to other AVR genes in two crosses. Bulk segregant analysis of over 100,000 AFLP fragments yielded two markers, ETAMTG-285 and PAAMACT-473, mapping 10 and 2cM from AVR(a12), respectively, thus delimiting AVR(a12) on one side. All markers obtained for AVR(a12) mapped proximal to it, indicating that the gene is located at the end of a chromosome. Three more AVR(a10) paralogues were identified at the locus interspersed among genes for metabolic enzymes and abundant repetitive elements, especially those homologous to the CgT1 class of retrotransposons. The flanking and close markers obtained will facilitate the isolation of AVR(a22) and AVR(a12) and provide useful tools for studies of the evolution of powdery mildew fungi in agriculture and nature. PMID:18036855

  15. Formation of planetesimals in collapsing pebble clouds

    Science.gov (United States)

    Wahlberg Jansson, K.; Johansen, A.

    2014-07-01

    Asteroids and Kuiper belt objects are remnant planetesimals from the epoch of planet formation. Their physical properties hold important clues to understanding how minor bodies formed in the Solar Nebula. The first stage of the planet formation process is the accumulation of dust and ice grains into mm-cm-sized pebbles. Due to the interaction with the gas in the protoplanetary disk, these pebbles can clump together through the streaming instability and form gravitationally bound particle pebble 'clouds'. Pebbles in the cloud collide with each other, dissipating energy into heat. As the cloud loses energy, it contracts, and one would expect the particles to move faster and faster due to the negative heat capacity nature of self-gravitating systems. However, for high-mass clouds, the collapse is limited by free-fall and the cloud does not have time to virialize. This in turn leads to lower collision speeds but thanks to increased density also to increased collision rates and a runaway collapse. We investigate three important properties of the collapse: (i) the time-scale to collapse to solid density, (ii) the temporal evolution of the size spectrum of the pebbles, and (iii) the multiplicity of the resulting planetesimals. We find that planetesimals larger than 100 km in radius collapse on the free-fall time-scale of about 25 years. Lower-mass clouds have longer pebble collision time-scales and hence collapse much more slowly, with collapse times of a few hundred years for 10-km-scale planetesimals and a few thousand years for 1-km-scale planetesimals. The mass of the pebble cloud also determines the structure of the resulting planetesimal. The collision speed among the pebbles in low- mass clouds is below the threshold for fragmentation, forming pebble- pile planetesimals consisting of the primordial pebbles from the nebula. Planetesimals above 100 km in radius, on the other hand, consist of mixtures of dust (pebble fragments) and pebbles which have undergone

  16. Significance of lead aVR in acute coronary syndrome

    Institute of Scientific and Technical Information of China (English)

    Akira; Tamura

    2014-01-01

    The 12-lead electrocardiogram(ECG)is a crucial tool in the diagnosis and risk stratification of acute coronary syndrome(ACS).Unlike other 11 leads,lead aVR has been long neglected until recent years.However,recent investigations have shown that an analysis of ST-segment shift in lead aVR provides useful information on the coronary angiographic anatomy and risk stratification in ACS.ST-segment elevation in lead aVR can be caused by(1)transmural ischemia in the basal part of the interventricular septum caused by impaired coronary blood flow of the first major branch originating from the left anterior descending coronary artery;(2)transmural ischemia in the right ventricular outflow tract caused by impaired coronary blood flow of the large conal branch originating from the right coronary artery;and(3)reciprocal changes opposite to ischemic or non-ischemic ST-segment depression in the lateral limb and precordial leads.On the other hand,ST-segment depression in lead aVR can be caused by transmural ischemia in the inferolateral and apical regions.It has been recently shown that an analysis of T wave in lead aVR also provides useful prognostic information in the general population and patients with prior myocardial infarction.Cardiologists should pay more attention to the tracing of lead aVR when interpreting the12-lead ECG in clinical practice.

  17. Radiolysis of Slightly Overstoichiometric Lithium Orthosilicate Pebbles

    OpenAIRE

    Zarins, A.; Supe, A; Kizane, G; Knitter, R.; Reinholds, I; Vitins, A; Tilika, V; Actins, A; Baumane, L

    2010-01-01

    : One of the technological problems of a fusion reactor is the change in composition and structure of ceramic breeder (Li4SiO4 or Li2TiO3 pebbles) during long-term operation. Changes in the composition and structure of the Li4SiO4 ceramic pebbles at fast electron irradiation (E = 5 MeV, dose rate up to 88 MGy•h-1, absorbed dose up to 10.6 GGy) at 543-573 K were investigated in this study. Overstoichiometric (2.5 weight % of additional SiO2) lithium orthosilicate pebbles were fabricated by...

  18. Demo aplikace s procesorem Atmel AVR32 UC

    OpenAIRE

    Zajíc, Jakub

    2010-01-01

    Tato diplomová práce vytváří stručný přehled architektury procesoru Atmel AVR32 UC. Zabývá se především procesorem AVR32 UC3A což je mikroarchitektura procesoru AVR32 UC. Z mikroarchitektury AVR32 UC3A je odvozen procesor AT32UC3A0512. Tento procesor je použit na vývojové desce EVK1100. Možnosti této desky jsou také zkoumány. Jsou uvedeny základní informace o programovacím a vývojovém prostředí AVR32 Studio pro tyto procesory. Po osvojení ovládání vývojového prostředí a studiu připojených uká...

  19. Rice Exo70 interacts with a fungal effector, AVR-Pii, and is required for AVR-Pii-triggered immunity.

    Science.gov (United States)

    Fujisaki, Koki; Abe, Yoshiko; Ito, Akiko; Saitoh, Hiromasa; Yoshida, Kentaro; Kanzaki, Hiroyuki; Kanzaki, Eiko; Utsushi, Hiroe; Yamashita, Tetsuro; Kamoun, Sophien; Terauchi, Ryohei

    2015-09-01

    Vesicle trafficking including the exocytosis pathway is intimately associated with host immunity against pathogens. However, we still have insufficient knowledge about how it contributes to immunity, and how pathogen factors affect it. In this study, we explore host factors that interact with the Magnaporthe oryzae effector AVR-Pii. Gel filtration chromatography and co-immunoprecipitation assays identified a 150 kDa complex of proteins in the soluble fraction comprising AVR-Pii and OsExo70-F2 and OsExo70-F3, two rice Exo70 proteins presumably involved in exocytosis. Simultaneous knockdown of OsExo70-F2 and F3 totally abrogated Pii immune receptor-dependent resistance, but had no effect on Pia- and Pik-dependent resistance. Knockdown levels of OsExo70-F3 but not OsExo70-F2 correlated with reduction of Pii function, suggesting that OsExo70-F3 is specifically involved in Pii-dependent resistance. Under our current experimental conditions, over-expression of AVR-Pii or knockdown of OsExo70-F2 and -F3 genes in rice did not affect the virulence of compatible isolates of M. oryzae. AVR-Pii interaction with OsExo70-F3 appears to play a crucial role in immunity triggered by Pii, suggesting a role for OsExo70 as a decoy or helper in Pii/AVR-Pii interactions. PMID:26186703

  20. Investigating the advantages and disadvantages of realistic approach and porous approach for closely packed pebbles in CFD simulation

    Energy Technology Data Exchange (ETDEWEB)

    Wu, C.Y. [Department of Engineering and System Science, Institute of Nuclear Engineering and Science, National Tsing Hua University, 101, Sec. 2, Kuang-Fu Rd., Hsingchu 30013, 325 Taiwan (China); Ferng, Y.M., E-mail: ymferng@ess.nthu.edu.t [Department of Engineering and System Science, Institute of Nuclear Engineering and Science, National Tsing Hua University, 101, Sec. 2, Kuang-Fu Rd., Hsingchu 30013, 325 Taiwan (China); Chieng, C.C.; Liu, C.C. [Department of Engineering and System Science, Institute of Nuclear Engineering and Science, National Tsing Hua University, 101, Sec. 2, Kuang-Fu Rd., Hsingchu 30013, 325 Taiwan (China)

    2010-05-15

    A pebble bed geometry is usually adopted for high-temperature gas-cooled reactors (HTGRs), which exhibits inherently safe performance, high conversion efficiency, and low power density design. It is important to understand the thermal-hydraulic characteristics of HTGR core for optimum design and safe operation. Therefore, this study investigates the thermal-hydraulic behaviors in a segment of pebbles predicted by the Reynolds-averaged Navier-Stokes (RANS) computational fluid dynamics (CFD) model using porous and realistic approaches for the complicated geometry. The advantages of each approach's methodology for the closely packed pebble geometry can be revealed by comparing the calculated results. In an engineering application, a CFD simulation with the porous approach for the pebble geometry can quickly and reasonably capture the averaged behaviors of the thermal-hydraulic parameters as the gas flows through the core, including the pressure drop and temperature increase. However, it is necessary to utilize the realistic approach for this complicated geometry to obtain the detailed and localized characteristics within the fluid and solid fuel regions. The present simulation results can provide useful information to help CFD researchers to determine an appropriate approach to be used when investigating the thermal-hydraulic characteristics within the reactor core of a closely packed pebble bed.

  1. A Pebble-Bed Breed-and-Burn Reactor

    Energy Technology Data Exchange (ETDEWEB)

    Greenspan, Ehud [Univ. of California, Berkeley, CA (United States)

    2016-03-31

    The primary objective of this project is to use three-dimensional fuel shuffling in order to reduce the minimum peak radiation damage of ~550 dpa present Breed-and-Burn (B&B) fast nuclear reactor cores designs (they feature 2-D fuel shuffling) call for to as close as possible to the presently accepted value of 200 dpa thereby enabling earlier commercialization of B&B reactors which could make substantial contribution to energy sustainability and economic stability without need for fuel recycling. Another objective is increasing the average discharge burnup for the same peak discharge burnup thereby (1) increasing the fuel utilization of 2-D shuffled B&B reactors and (2) reducing the reprocessing capacity required to support a given capacity of FRs that are to recycle fuel.

  2. New reactor programs from passive to pebble bed

    Energy Technology Data Exchange (ETDEWEB)

    Bruschi, H.J. [Westinghouse Electric Corp., Pittsburgh, PA (United States)

    2002-07-01

    The market for new nuclear power plants is small and challenged by alternative means of electric power generation. Customers and countries may vary in their requirements for a new nuclear plant; but all have a common theme of seeking a design that possesses favorable economics. This paper sets forth the economic challenges a new nuclear plant must overcome. In particular, it delineates the capital cost, construction time, and generation cost required to compete with combined cycle gas electric power generation. The U.S. power generation market is used as a point of comparison. Following this, the portfolio of BNFL/ Westinghouse plant designs are described and the methods by which they will meet the economic challenges previously delineated will be discussed. The portfolio includes the family of passive plants originated by the AP600 Design Certification process in the U.S. These plants are marked by a high degree of safety and simplicity, short construction times, and superior economics. In addition, the effort to meet European requirements for passive plants will be described. Lastly, the paper explores some advanced nuclear designs that are not yet licensed, and the hope that they hold for meeting the industry challenge ahead. (author)

  3. A Pebble-Bed Breed-and-Burn Reactor

    International Nuclear Information System (INIS)

    The primary objective of this project is to use three-dimensional fuel shuffling in order to reduce the minimum peak radiation damage of ~550 dpa present Breed-and-Burn (B&B) fast nuclear reactor cores designs (they feature 2-D fuel shuffling) call for to as close as possible to the presently accepted value of 200 dpa thereby enabling earlier commercialization of B&B reactors which could make substantial contribution to energy sustainability and economic stability without need for fuel recycling. Another objective is increasing the average discharge burnup for the same peak discharge burnup thereby (1) increasing the fuel utilization of 2-D shuffled B&B reactors and (2) reducing the reprocessing capacity required to support a given capacity of FRs that are to recycle fuel.

  4. Pebble Bed Modular Reactor. Executive summary, Issue D

    International Nuclear Information System (INIS)

    The PBMR Project has been under active investigation by Eskom, as part of the Integrated Electricity Planning process, since 1993. The overall objectives of these investigations have been to establish whether such a system could form part of Eskom's expansion planning and what specific advantages it would bring over current options. This would include a technical performance and economic evaluation associated with the project. A comprehensive evaluation was performed as to the international interest existing within this field of technology, including the availability of this technology. The first phase of this investigation is now complete and the results have been compiled in a comprehensive set of technical and costing reports. A basic engineering simulator is being developed which provides engineering design support. The present results of this study show that the design has been established in enough detail to support key safety studies, confirm operating limits and estimated costing. The costing includes: - Production costs for a single module and a unit (unit = 10 x module) cost; - Operation and maintenance costing; - Fuel plant costing ? Design and development costing The studies showed that the technology required for the design has been demonstrated adequately to avoid fundamental technical risk. The increased level of inherent safety (over current designs) is fundamental to the cost reductions achieved over other nuclear designs. By demonstrating a catastrophe free design the requirements for both safety grade backup systems and an off-site emergency plan are removed

  5. Fabrication of Li{sub 2}TiO{sub 3} pebbles using PVA–boric acid reaction for solid breeding materials

    Energy Technology Data Exchange (ETDEWEB)

    Park, Yi-Hyun, E-mail: yhpark@nfri.re.kr; Cho, Seungyon; Ahn, Mu-Young

    2014-12-15

    Highlights: • Li{sub 2}TiO{sub 3} pebbles were successfully fabricated by the slurry droplet wetting method. • Boron was used as hardening agent of PVA and completely removed during sintering. • Microstructure of fabricated Li{sub 2}TiO{sub 3} pebble was exceptionally homogeneous. • Suitable process conditions for high-quality Li{sub 2}TiO{sub 3} pebble were summarized. - Abstract: Lithium metatitanate (Li{sub 2}TiO{sub 3}) is a candidate breeding material of the Helium Cooled Ceramic Reflector (HCCR) Test Blanket Module (TBM). The breeding material is used in pebble-bed form to reduce the uncertainty of the interface thermal conductance. In this study, Li{sub 2}TiO{sub 3} pebbles were successfully fabricated by the slurry droplet wetting method using the cross-linking reaction between polyvinyl alcohol (PVA) and boric acid. The effects of fabrication parameters on the shaping of Li{sub 2}TiO{sub 3} green body were investigated. In addition, the basic characteristics of the sintered pebble were also evaluated. The shape of Li{sub 2}TiO{sub 3} green bodies was affected by slurry viscosity, PVA content and boric acid content. The grain size and average crush load of sintered Li{sub 2}TiO{sub 3} pebble were controlled by the sintering time. The boron was completely removed during the final sintering process.

  6. Transcriptome sequencing uncovers the Avr5 avirulence gene of the tomato leaf mold pathogen Cladosporium fulvum.

    Science.gov (United States)

    Mesarich, Carl H; Griffiths, Scott A; van der Burgt, Ate; Okmen, Bilal; Beenen, Henriek G; Etalo, Desalegn W; Joosten, Matthieu H A J; de Wit, Pierre J G M

    2014-08-01

    The Cf-5 gene of tomato confers resistance to strains of the fungal pathogen Cladosporium fulvum carrying the avirulence gene Avr5. Although Cf-5 has been cloned, Avr5 has remained elusive. We report the cloning of Avr5 using a combined bioinformatic and transcriptome sequencing approach. RNA-Seq was performed on the sequenced race 0 strain (0WU; carrying Avr5), as well as a race 5 strain (IPO 1979; lacking a functional Avr5 gene) during infection of susceptible tomato. Forty-four in planta-induced C. fulvum candidate effector (CfCE) genes of 0WU were identified that putatively encode a secreted, small cysteine-rich protein. An expressed transcript sequence comparison between strains revealed two polymorphic CfCE genes in IPO 1979. One of these conferred avirulence to IPO 1979 on Cf-5 tomato following complementation with the corresponding 0WU allele, confirming identification of Avr5. Complementation also led to increased fungal biomass during infection of susceptible tomato, signifying a role for Avr5 in virulence. Seven of eight race 5 strains investigated escape Cf-5-mediated resistance through deletion of the Avr5 gene. Avr5 is heavily flanked by repetitive elements, suggesting that repeat instability, in combination with Cf-5-mediated selection pressure, has led to the emergence of race 5 strains deleted for the Avr5 gene.

  7. The Cladosporium fulvum virulence protein Avr2 inhibits host proteases required for basal defense.

    Science.gov (United States)

    van Esse, H Peter; Van't Klooster, John W; Bolton, Melvin D; Yadeta, Koste A; van Baarlen, Peter; Boeren, Sjef; Vervoort, Jacques; de Wit, Pierre J G M; Thomma, Bart P H J

    2008-07-01

    Cladosporium fulvum (syn. Passalora fulva) is a biotrophic fungal pathogen that causes leaf mold of tomato (Solanum lycopersicum). During growth in the apoplast, the fungus establishes disease by secreting effector proteins, 10 of which have been characterized. We have previously shown that the Avr2 effector interacts with the apoplastic tomato Cys protease Rcr3, which is required for Cf-2-mediated immunity. We now show that Avr2 is a genuine virulence factor of C. fulvum. Heterologous expression of Avr2 in Arabidopsis thaliana causes enhanced susceptibility toward extracellular fungal pathogens, including Botrytis cinerea and Verticillium dahliae, and microarray analysis showed that Avr2 expression triggers a global transcriptome reflecting pathogen challenge. Cys protease activity profiling showed that Avr2 inhibits multiple extracellular Arabidopsis Cys proteases. In tomato, Avr2 expression caused enhanced susceptibility toward Avr2-defective C. fulvum strains and also toward B. cinerea and V. dahliae. Cys protease activity profiling in tomato revealed that, in this plant also, Avr2 inhibits multiple extracellular Cys proteases, including Rcr3 and its close relative Pip1. Finally, silencing of Avr2 significantly compromised C. fulvum virulence on tomato. We conclude that Avr2 is a genuine virulence factor of C. fulvum that inhibits several Cys proteases required for plant basal defense.

  8. Genomic organization and sequence dynamics of the AvrPiz-t locus in Magnaporthe oryzae

    Institute of Scientific and Technical Information of China (English)

    Ping LI; Bin BAI; Hong-yan ZHANG; Heng ZHOU; Bo ZHOU

    2012-01-01

    Plants utilize multiple layers of defense mechanisms to fight against the invasion of diverse pathogens.The R gene mediates resistance,in most cases,dependent on the co-existence of its cognate pathogen-derived avirulence (Avr) gene.The rice blast R gene Piz-t corresponds in gene-for-gene fashion to the Magnaporthe oryzae Avrgene AvrPiz-t.In this study,we determined and compared the genomic sequences surrounding the AvrPiz-t gene in both avirulent and virulent isolates,designating as AvrPiz-t-ZB15 and avrPiz-t-70-15 regions,respectively.The sequence of the AvrPiz-t-ZB15 region is 120966 bp whereas avrPiz-t-70-15 is 146292 bp in length.The extreme sequence similarity and good synteny in gene order and content along with the absence of two predicted genes in the avrPiz-t-70-15 region were observed in the predicted protein-coding regions in the AvrPiz-t locus.Nevertheless,frequent presence/absence and highly dynamic organization of transposable elements (TEs) were identified,representing the major variation of the AvrPiz-t locus between different isolates.Moreover,TEs constitute 27.3% and 43.2%of the genomic contents of the AvrPiz-t-ZB15 and avrPiz-t-70-15 regions,respectively,indicating that TEs contribute largely to the organization and evolution of AvrPiz-t locus.The findings of this study suggest that M.oryzae could benefit in an evolutionary sense from the presence of active TEs in genes conferring avirulence and provide an ability to rapidly change and thus to overcome host R genes.

  9. Specific recognition of AVR4 and AVR9 results in distinct patterns of hypersensitive cell death in tomato, but similar patterns of defence-related gene expression

    NARCIS (Netherlands)

    Cai, X.; Takken, F.L.W.; Joosten, M.H.A.J.; Wit, De P.J.G.M.

    2001-01-01

    Hypersensitive cell death occurs in tomato seedlings that are derived from a cross between plants that express a resistance (Cf) gene against the pathogenic fungus Cladosporium fulvum and plants that contain the matching avirulence (Avr) gene originating from this fungus. The pattern of Cf-9/Avr9- a

  10. Conversion of an AVR reactor into a process heat reactor

    International Nuclear Information System (INIS)

    The proposal to convert the Juelich AVR into a process heat reactor aims at achieving a low-cost demonstration and system test of uncoupling process heat from a high-temperature reactor at a high useful temperature. The conversion is planned in such a way that the AVR can serve various conversion processes in succession as a nuclear source. For the first operational phase a methane-water vapor reformation by means of a tube fission furnace and a process steam generator as an element of direct heat uncoupling in a technical process is envisaged. For further operational phases, other coal processing methods are planned. The concept, safety features, licensability, cost, utilization and deadlines are outlined. (orig./DG)

  11. Pebble Accretion and the Diversity of Planetary Systems

    CERN Document Server

    Chambers, J E

    2016-01-01

    I examine the standard model of planet formation, including pebble accretion, using numerical simulations. Planetary embryos large enough to become giant planets do not form beyond the ice line within a typical disk lifetime unless icy pebbles stick at higher speeds than in experiments using rocky pebbles. Systems like the Solar System (small inner planets, giant outer planets) can form if (i) icy pebbles are stickier than rocky pebbles, and (ii) the planetesimal formation efficiency increases with pebble size, which prevents the formation of massive terrestrial planets. Growth beyond the ice line is dominated by pebble accretion. Most growth occurs early, when the surface density of pebbles is high due to inward drift of pebbles from the outer disk. Growth is much slower after the outer disk is depleted. The outcome is sensitive to the disk radius and turbulence level, which control the lifetime and maximum size of pebbles. The outcome is sensitive to the size of the largest planetesimals since there is a th...

  12. The Salmonella effector AvrA mediates bacterial intracellular survival during infection in vivo.

    Science.gov (United States)

    Wu, Huixia; Jones, Rheinallt M; Neish, Andrew S

    2012-01-01

    The enteric pathogen Salmonella typhimurium secretes the preformed AvrA effector protein into host cells. This acetyltransferase has been shown to modulate mammalian intestinal immune and survival responses by inhibition of JNK MAPK. To study the role of this effector in natural enteric infection, we used a mouse model to compare wild-type S. typhimurium to an isogenic AvrA null Salmonella mutant. Salmonella lacking AvrA induced increased intestinal inflammation, more intense systemic cytokine responses, and increased apoptosis in epithelial cells. Increased apoptosis was also observed in extra epithelial macrophages. AvrA null-infected mice consistently showed higher bacterial burden within mucosal lymphoid tissues, spleen and liver by 5 days post infection, which indicated a more severe clinical course. To study the molecular mechanisms involved, recombinant adenoviruses expressing AvrA or mutant AvrA proteins were constructed, which showed appropriate expression and mediated the expected inhibition of JNK signalling. Cultured epithelial cells and macrophages transduced with AvrA expressing adenovirus were protected from apoptosis induced by exogenous stimuli. In conclusion, the results demonstrated that Salmonella AvrA modulates survival of infected macrophages likely via JNK suppression, and prevents macrophage death and rapid bacterial dissemination. AvrA suppression of apoptosis in infected macrophages may allow for establishment of a stable intracellular niche typical of intracellular pathogens.

  13. Cladosporium fulvum Avr4 protects fungal cell walls against hydrolysis by plant chitinases accumulating during infection.

    Science.gov (United States)

    van den Burg, Harrold A; Harrison, Stuart J; Joosten, Matthieu H A J; Vervoort, Jacques; de Wit, Pierre J G M

    2006-12-01

    Resistance against the leaf mold fungus Cladosporium fulvum is mediated by the tomato Cf proteins which belong to the class of receptor-like proteins and indirectly recognize extracellular avirulence proteins (Avrs) of the fungus. Apart from triggering disease resistance, Avrs are believed to play a role in pathogenicity or virulence of C. fulvum. Here, we report on the avirulence protein Avr4, which is a chitin-binding lectin containing an invertebrate chitin-binding domain (CBM14). This domain is found in many eukaryotes, but has not yet been described in fungal or plant genomes. We found that interaction of Avr4 with chitin is specific, because it does not interact with other cell wall polysaccharides. Avr4 binds to chitin oligomers with a minimal length of three N-acetyl glucosamine residues. In vitro, Avr4 protects chitin against hydrolysis by plant chitinases. Avr4 also binds to chitin in cell walls of the fungi Trichoderma viride and Fusarium solani f. sp. phaseoli and protects these fungi against normally deleterious concentrations of plant chitinases. In situ fluorescence studies showed that Avr4 also binds to cell walls of C. fulvum during infection of tomato, where it most likely protects the fungus against tomato chitinases, suggesting that Avr4 is a counter-defensive virulence factor.

  14. Perturbation of maize phenylpropanoid metabolism by an AvrE family type III effector from Pantoea stewartii.

    Science.gov (United States)

    Asselin, Jo Ann E; Lin, Jinshan; Perez-Quintero, Alvaro L; Gentzel, Irene; Majerczak, Doris; Opiyo, Stephen O; Zhao, Wanying; Paek, Seung-Mann; Kim, Min Gab; Coplin, David L; Blakeslee, Joshua J; Mackey, David

    2015-03-01

    AvrE family type III effector proteins share the ability to suppress host defenses, induce disease-associated cell death, and promote bacterial growth. However, despite widespread contributions to numerous bacterial diseases in agriculturally important plants, the mode of action of these effectors remains largely unknown. WtsE is an AvrE family member required for the ability of Pantoea stewartii ssp. stewartii (Pnss) to proliferate efficiently and cause wilt and leaf blight symptoms in maize (Zea mays) plants. Notably, when WtsE is delivered by a heterologous system into the leaf cells of susceptible maize seedlings, it alone produces water-soaked disease symptoms reminiscent of those produced by Pnss. Thus, WtsE is a pathogenicity and virulence factor in maize, and an Escherichia coli heterologous delivery system can be used to study the activity of WtsE in isolation from other factors produced by Pnss. Transcriptional profiling of maize revealed the effects of WtsE, including induction of genes involved in secondary metabolism and suppression of genes involved in photosynthesis. Targeted metabolite quantification revealed that WtsE perturbs maize metabolism, including the induction of coumaroyl tyramine. The ability of mutant WtsE derivatives to elicit transcriptional and metabolic changes in susceptible maize seedlings correlated with their ability to promote disease. Furthermore, chemical inhibitors that block metabolic flux into the phenylpropanoid pathways targeted by WtsE also disrupted the pathogenicity and virulence activity of WtsE. While numerous metabolites produced downstream of the shikimate pathway are known to promote plant defense, our results indicate that misregulated induction of phenylpropanoid metabolism also can be used to promote pathogen virulence. PMID:25635112

  15. Perturbation of Maize Phenylpropanoid Metabolism by an AvrE Family Type III Effector from Pantoea stewartii1[OPEN

    Science.gov (United States)

    Asselin, Jo Ann E.; Lin, Jinshan; Perez-Quintero, Alvaro L.; Gentzel, Irene; Majerczak, Doris; Opiyo, Stephen O.; Zhao, Wanying; Paek, Seung-Mann; Kim, Min Gab; Coplin, David L.; Blakeslee, Joshua J.; Mackey, David

    2015-01-01

    AvrE family type III effector proteins share the ability to suppress host defenses, induce disease-associated cell death, and promote bacterial growth. However, despite widespread contributions to numerous bacterial diseases in agriculturally important plants, the mode of action of these effectors remains largely unknown. WtsE is an AvrE family member required for the ability of Pantoea stewartii ssp. stewartii (Pnss) to proliferate efficiently and cause wilt and leaf blight symptoms in maize (Zea mays) plants. Notably, when WtsE is delivered by a heterologous system into the leaf cells of susceptible maize seedlings, it alone produces water-soaked disease symptoms reminiscent of those produced by Pnss. Thus, WtsE is a pathogenicity and virulence factor in maize, and an Escherichia coli heterologous delivery system can be used to study the activity of WtsE in isolation from other factors produced by Pnss. Transcriptional profiling of maize revealed the effects of WtsE, including induction of genes involved in secondary metabolism and suppression of genes involved in photosynthesis. Targeted metabolite quantification revealed that WtsE perturbs maize metabolism, including the induction of coumaroyl tyramine. The ability of mutant WtsE derivatives to elicit transcriptional and metabolic changes in susceptible maize seedlings correlated with their ability to promote disease. Furthermore, chemical inhibitors that block metabolic flux into the phenylpropanoid pathways targeted by WtsE also disrupted the pathogenicity and virulence activity of WtsE. While numerous metabolites produced downstream of the shikimate pathway are known to promote plant defense, our results indicate that misregulated induction of phenylpropanoid metabolism also can be used to promote pathogen virulence. PMID:25635112

  16. Mechanics of a crushable pebble assembly using discrete element method

    Energy Technology Data Exchange (ETDEWEB)

    Annabattula, R.K., E-mail: ratna.annabattula@kit.edu [Institute for Applied Materials (IAM-WBM), Karlsruhe Institute of Technology (KIT), D-76344 Eggenstein-Leopoldshafen (Germany); Gan, Y., E-mail: yixiang.gan@sydney.edu.au [School of Civil Engineering, University of Sydney, 2006 NSW, Sydney (Australia); Zhao, S. [College of Mechanical and Electronics Engineering, Hebei University of Science and Technology, Shijiazhuang, Hebei 050018 (China); Kamlah, M., E-mail: marc.kamlah@kit.edu [Institute for Applied Materials (IAM-WBM), Karlsruhe Institute of Technology (KIT), D-76344 Eggenstein-Leopoldshafen (Germany)

    2012-11-15

    The influence of crushing of individual pebbles on the overall strength of a pebble assembly is investigated using discrete element method. An assembly comprising of 5000 spherical pebbles is assigned with random critical failure energies with a Weibull distribution in accordance with the experimental observation. Then, the pebble assembly is subjected to uni-axial compression ({epsilon}{sub 33}=1.5%) with periodic boundary conditions. The crushable pebble assembly shows a significant difference in stress-strain response in comparison to a non-crushable pebble assembly. The analysis shows that a ideal plasticity like behaviour (constant stress with increase in strain) is the characteristic of a crushable pebble assembly with sudden damage. The damage accumulation law plays a critical role in determining the critical stress while the critical number of completely failed pebbles at the onset of critical stress is independent of such a damage law. Furthermore, a loosely packed pebble assembly shows a higher crush resistance while the critical stress is insensitive to the packing factor ({eta}) of the assembly.

  17. Tritium analyses of COBRA-1A2 beryllium pebbles

    Energy Technology Data Exchange (ETDEWEB)

    Baldwin, D.L. [Pacific Northwest National Lab., Richland, WA (United States)

    1998-03-01

    Selected tritium measurements have been completed for the COBRA-1A2 experiment C03 and D03 beryllium pebbles. The completed results, shown in Tables 1, 2, and 3, include the tritium assay results for the 1-mm and 3-mm C03 pebbles, and the 1-mm D03 pebbles, stepped anneal test results for both types of 1-mm pebbles, and the residual analyses for the stepped-anneal specimens. All results have been reported with date-of-count and are not corrected for decay. Stepped-anneal tritium release response is provided in addenda.

  18. Chronic effects of a Salmonella type III secretion effector protein AvrA in vivo.

    Directory of Open Access Journals (Sweden)

    Rong Lu

    Full Text Available BACKGROUND: Salmonella infection is a common public health problem that can become chronic and increase the risk of inflammatory bowel diseases and cancer. AvrA is a Salmonella bacterial type III secretion effector protein. Increasing evidence demonstrates that AvrA is a multi-functional enzyme with critical roles in inhibiting inflammation, regulating apoptosis, and enhancing proliferation. However, the chronic effects of Salmonella and effector AvrA in vivo are still unknown. Moreover, alive, mutated, non-invasive Salmonella is used as a vector to specifically target cancer cells. However, studies are lacking on chronic infection with non-pathogenic or mutated Salmonella in the host. METHODS/PRINCIPAL FINDINGS: We infected mice with Salmonella Typhimurium for 27 weeks and investigated the physiological effects as well as the role of AvrA in intestinal inflammation. We found altered body weight, intestinal pathology, and bacterial translocation in spleen, liver, and gallbladder in chronically Salmonella-infected mice. Moreover, AvrA suppressed intestinal inflammation and inhibited the secretion of cytokines IL-12, IFN-gamma, and TNF-alpha. AvrA expression in Salmonella enhanced its invasion ability. Liver abscess and Salmonella translocation in the gallbladder were observed and may be associated with AvrA expression in Salmonella. CONCLUSION/SIGNIFICANCE: We created a mouse model with persistent Salmonella infection in vivo. Our study further emphasizes the importance of the Salmonella effector protein AvrA in intestinal inflammation, bacterial translocation, and chronic infection in vivo.

  19. Radiochemical characterization of graphite from Juelich experimental reactor (AVR)

    International Nuclear Information System (INIS)

    Nuclear reactors which have in-built graphite may receive a high neutron dose for a long period. Depending on the chemical composition of the graphite, numerous activation products may result. In addition, the amount of fission product contamination will depend on the location of the graphite. The migration of fission products may be supported by the high temperatures which occur in high-temperature reactors. At the Juelich 15 MWe high-temperature gas-cooled experimental AVR (Arbeitsgemeinschaft Versuchsreaktor) reactor, two different types of nuclear graphite had been in use. High-purity graphite was used as a basic material for core structures of the AVR. Insulation layers of carbon bricks (graphite with larger amounts of impurities) surrounding the graphite reflector were used to protect the metallic structures from high temperatures. For various reasons it is important to know the degree of contamination of graphite and carbon bricks from activation and fission products. The optimum method for nuclear graphite analysis in decommissioning is by incineration. Volatile activities (14C, 3H, 36Cl, ...) have to be captured for analysis. In cases where dust-like samples are handled, the incineration furnace has to be small enough to be operated in a glove-box. The resulting ashes can be used for determining all non-volatile nuclides by different radiochemical methods. In early 1999, some graphite and carbon brick samples from the AVR reactor were obtained by drilling. The samples were then analysed in the laboratories at the Juelich research centre. For incineration a vertical quartz tube was used which dips at the bottom into a small electric furnace. Tritium, 14C and 36Cl were captured in washing bottles. After further preparation, they were analysed by liquid scintillation counting (LSC). After dissolving the ashes, the elements were separated by ion exchange, extraction methods and HPLC. The radionuclides were then determined by alpha-spectrometry, LSC, low

  20. Atmel AVR Microcontroller Primer Programming and Interfacing, Second Edition

    CERN Document Server

    Barrett, Steven F

    2012-01-01

    This textbook provides practicing scientists and engineers a primer on the Atmel AVR microcontroller. In this second edition we highlight the popular ATmega164 microcontroller and other pin-for-pin controllers in the family with a complement of flash memory up to 128 kbytes. The second edition also adds a chapter on embedded system design fundamentals and provides extended examples on two different autonomous robots. Our approach is to provide the fundamental skills to quickly get up and operating with this internationally popular microcontroller. We cover the main subsystems aboard the ATmega

  1. Comparison of Automated Image-Based Grain Sizing to Standard Pebble Count Methods

    Science.gov (United States)

    Strom, K. B.

    2009-12-01

    This study explores the use of an automated, image-based method for characterizing grain-size distributions (GSDs) of exposed, open-framework gravel beds. This was done by comparing the GSDs measured with an image-based method to distributions obtained with two pebble-count methods. Selection of grains for the two pebble-count methods was carried out using a gridded sampling frame and the heel-to-toe Wolman walk method at six field sites. At each site, 500-partcle pebble-count samples were collected with each of the two pebble-count methods and digital images were systematically collected over the same sampling area. For the methods used, the pebble counts collected with the gridded sampling frame were assumed to be the most accurate representations of the true grain-size population, and results from the image-based method were compared to the grid derived GSDs for accuracy estimates; comparisons between the grid and Wolman walk methods were conducted to give an indication of possible variation between commonly used methods for each particular field site. Comparison of grain sizes were made at two spatial scales. At the larger scale, results from the image-based method were integrated over the sampling area required to collect the 500-particle pebble-count samples. At the smaller sampling scale, the image derived GSDs were compared to those from 100-particle, pebble-count samples obtained with the gridded sampling frame. The comparisons show that the image-based method performed reasonably well on five of the six study sites. For those five sites, the image-based method slightly underestimate all grain-size percentiles relative to the pebble counts collected with the gridded sampling frame. The average bias for Ψ5, Ψ50, and Ψ95 between the image and grid count methods at the larger sampling scale was 0.07Ψ, 0.04Ψ, and 0.19Ψ respectively; at the smaller sampling scale the average bias was 0.004Ψ, 0.03Ψ, and 0.18Ψ respectively. The average bias between the

  2. The chitin-binding Cladosporium fulvum effector protein Avr4 is a virulence factor.

    Science.gov (United States)

    van Esse, H Peter; Bolton, Melvin D; Stergiopoulos, Ioannis; de Wit, Pierre J G M; Thomma, Bart P H J

    2007-09-01

    The biotrophic fungal pathogen Cladosporium fulvum (syn. Passalora fulva) is the causal agent of tomato leaf mold. The Avr4 protein belongs to a set of effectors that is secreted by C. fulvum during infection and is thought to play a role in pathogen virulence. Previous studies have shown that Avr4 binds to chitin present in fungal cell walls and that, through this binding, Avr4 can protect these cell walls against hydrolysis by plant chitinases. In this study, we demonstrate that Avr4 expression in Arabidopsis results in increased virulence of several fungal pathogens with exposed chitin in their cell walls, whereas the virulence of a bacterium and an oomycete remained unaltered. Heterologous expression of Avr4 in tomato increased the virulence of Fusarium oxysporum f. sp. lycopersici. Through tomato GeneChip analyses, we demonstrate that Avr4 expression in tomato results in the induced expression of only a few genes. Finally, we demonstrate that silencing of the Avr4 gene in C. fulvum decreases its virulence on tomato. This is the first report on the intrinsic function of a fungal avirulence protein that has a counter-defensive activity required for full virulence of the pathogen.

  3. AvrXa3:A novel member of avrBs3 gene family from Xanthomonas oryzae pv.oryzae has a dual function

    Institute of Scientific and Technical Information of China (English)

    LI Ping; LONG Juying; HUANG Yingchun; ZHANG Yan; WANG Jinsheng

    2004-01-01

    Two positive clones pUAV45 and pUAV47 were identified from the cDNA library of JxoⅢ, a race 3 strain of Xanthomonas oryzae pv. Oryzae Dye (Xoo) in Japanese system, using Tn5 based technology. pUAV45 clone contained a 25.4 kb Xoo genomic DNA insert. Southern blot analysis with avrXa10 as the probe showed that DNA insert in pUAV45 shares homology with avrX10. Furthermore within the Xoo insert, a smaller 5.7 kb KpnI fragment (pUAVSk) was identified through hybridization with avrXa10. The transformation of pUAV45 and pUAV5k into the strain Pxo99 (race 6 in Philippine system) led to the decrease of Pxo99pathogenicity on rice cultivar Wase Aikoku 3 (Xa3) and the increase of the pathogen pathogenicity on Cas209 (Xa10). The result of sequence analysis showed that there is a 2598 bp open reading frame (ORF) within the 5.7 kb Kpn 1 fragment (pUAVSk). The ORF shared high identity (97 % ) with avrXa10. The deduced sequence of the ORF contained 8.5 tandem repeat units of 34-amino-acids, one leucine zipper (LZ), three nuclear localization signal (NLS) motifs, and an acidic activation transcriptional domain (AAD) at C-terminus.We named this ORF avrXa3 and it is classified as a new member of avrBs3 (avr/pth) family with the dual-function determined by alternations of avirulence and aggressiveness on rice cultivars carrying different ‘ R' genes.

  4. Utility of lead aVR for identifying the culprit lesion in acute myocardial infarction

    DEFF Research Database (Denmark)

    Kühl, Jørgen Tobias; Berg, Ronan M G

    2009-01-01

    BACKGROUND: Lead aVR is a neglected, however, potentially useful tool in electrocardiography. Our aim was to evaluate its value in clinical practice, by reviewing existing literature regarding its utility for identifying the culprit lesion in acute myocardial infarction (AMI). METHODS: Based......). The studies were too heterogeneous to pool, but the individual studies all showed that STE in aVR has a high negative predictive value (NPV) for LMS. Six studies evaluated if STE in aVR is valuable for distinguishing proximal from distal lesions in the left anterior descending artery (LAD) in anterior ST...

  5. Building massive compact planetesimal disks from the accretion of pebbles

    CERN Document Server

    Moriarty, John

    2015-01-01

    We present a model in which planetesimal disks are built from the combination of planetesimal formation and accretion of radially drifting pebbles onto existing planetesimals. In this model, the rate of accretion of pebbles onto planetesimals quickly outpaces the rate of direct planetesimal formation in the inner disk. This allows for the formation of a high mass inner disk without the need for enhanced planetesimal formation or a massive protoplanetary disk. Our proposed mechanism for planetesimal disk growth does not require any special conditions to operate. Consequently, we expect that high mass planetesimal disks form naturally in nearly all systems. The extent of this growth is controlled by the total mass in pebbles that drifts through the inner disk. Anything that reduces the rate or duration of pebble delivery will correspondingly reduce the final mass of the planetesimal disk. Therefore, we expect that low mass stars (with less massive protoplanetary disks), low metallicity stars and stars with gian...

  6. On the growth of pebble-accreting planetesimals

    CERN Document Server

    Visser, Rico G

    2015-01-01

    Pebble accretion is a new mechanism to quickly grow the cores of planets. In pebble accretion, gravity and gas drag conspire to yield large collisional cross sections for small particles in protoplanetary disks. However, before pebble accretion commences, aerodynamical deflection may act to prevent planetesimals from becoming large, because particles tend to follow gas streamlines. We derive the planetesimal radius where pebble accretion is initiated and determine the growth timescales of planetesimals by sweepup of small particles. We obtain the collision efficiency factor as the ratio of the numerically-obtained collisional cross section to the planetesimal surface area, from which we obtain the growth timescales. Integrations are conducted in the potential flow limit (steady, inviscid) and in the Stokes flow regime (steady, viscid). Only particles of stopping time $t_s \\ll t_X$ where $t_X\\approx10^3$ s experience aerodynamic deflection. Even in that case, the planetesimal's gravity always ensures positive ...

  7. Mechanics, kinematics and geometry of pebble abrasion from binary collisions

    Science.gov (United States)

    Miller, K. L.; Jerolmack, D. J.

    2014-12-01

    As sediment is transported downstream as bedload, it collides with the bed causing sharp edges to chip and wear away, rounding the rock through the process of abrasion. Previous work has linked abrasion to downstream fining and rounding of grains, however, there has been little attempt to understand the underlying kinematics of abrasion. Furthermore, most studies neglect the fine particle produced during the abrasion process, as the initial grain gets smaller and rounder. In this research, we preform well-controlled laboratory experiments to determine the functional dependence between impact energy and mass lost from abrasion. We use a double-pendulum "Newton's Cradle" set-up to examine the abrasion between two grains and with a high-speed camera, we can quantify the impact energies during collision. Results from experiments verify that mass loss is proportional to kinetic energy. We define a material parameter that incorporates material density, Young's modulus, and tensile stress and show that this parameter is directly related to the proportionality between mass loss and energy. We identify an initial region of the mass loss curves in which abrasion is independent of energy and material properties; results suggest this region is determined by shape. We show that grain size distributions of daughter products are universal and independent of material; they follow a Weibull distribution, which is expected distribution from brittle fracture theory. Finally, scanning electron microscope (SEM) images show a thin damage zone near the surface, suggesting that collision energy is attenuated over some small skin depth. Overall, we find that pebble abrasion by collision can be characterized by two universal scaling relations - the mass loss versus energy curves and the size distribution of daughter products. Results will be useful for estimating expected abrasion rates in the field, and additionally demonstrate that low-energy collisions produce large quantities of sand

  8. ST segment elevation in lead aVR during exercise testing is associated with LAD stenosis

    Energy Technology Data Exchange (ETDEWEB)

    Neill, Johanne; Harbinson, Mark [Royal Victoria Hospital, Regional Medical Cardiology Centre, Belfast (United Kingdom); Queens University, Belfast (United Kingdom); Shannon, Heather J.; Morton, Amanda; Muir, Alison R.; Adgey, Jennifer A. [Royal Victoria Hospital, Regional Medical Cardiology Centre, Belfast (United Kingdom)

    2007-03-15

    To evaluate, in patients with chest pain, the diagnostic value of ST elevation (STE) in lead aVR during stress testing prior to {sup 99m} Tc-sestamibi scanning correlating ischaemic territory with angiographic findings. Consecutive patients attending for {sup 99m} Tc-sestamibi myocardial perfusion imaging (MPI) completed a treadmill protocol. Peak exercise ECGs were coded. STE {>=}0.05 mV in lead aVR was considered significant. Gated perfusion images and findings at angiography were assessed. STE in lead aVR occurred in 25% (138/557) of the patients. More patients with STE in aVR had a reversible defect on imaging compared with those who had no STE in aVR (41%, 56/138 vs 27%, 114/419, p=0.003). Defects indicating a left anterior descending artery (LAD) culprit lesion were more common in the STE in aVR group (20%, 27/138 vs 9%, 39/419, p=0.001). There was a trend towards coronary artery stenosis (>70%) in a double vessel distribution involving the LAD in those patients who had STE in aVR compared with those who did not (22%, 8/37 vs 5%, 4/77, p=0.06). Logistic regression analysis demonstrated that STE in aVR (OR 1.36, p=0.233) is not an independent predictor of inducible abnormality when adjusted for STD >0.1 mV (OR 1.69, p=0.026). However, using anterior wall defect as an end-point, STE in aVR (OR 2.77, p=0.008) was a predictor even after adjustment for STD (OR 1.43, p=0.281). STE in lead aVR during exercise does not diagnose more inducible abnormalities than STD alone. However, unlike STD, which is not predictive of a territory of ischaemia, STE in aVR may indicate an anterior wall defect. (orig.)

  9. Comparison of intelligent fuzzy based AGC coordinated PID controlled and PSS controlled AVR system

    Energy Technology Data Exchange (ETDEWEB)

    Mukherjee, V. [Department of Electrical Engineering, Asansol Engineering College, Asansol, West Bengal (India); Ghoshal, S.P. [Department of Electrical Engineering, National Institute of Technology, Durgapur, West Bengal (India)

    2007-11-15

    This paper attempts to investigate the performance of intelligent fuzzy based coordinated control of the Automatic Generation Control (AGC) loop and the excitation loop equipped with Proportional Integral Derivative (PID) controlled Automatic Voltage Regulator (AVR) system and Power System Stabilizer (PSS) controlled AVR system. The work establishes that PSS controlled AVR system is much more robust in dynamic performance of the system over a wide range of system operating configurations. Thus, it is revealed that PSS equipped AVR is much more superior than PID equipped AVR in damping the oscillation resulting in improved transient response. The paper utilizes a novel class of Particle Swarm Optimization (PSO) termed as Craziness based Particle Swarm Optimization (CRPSO) as optimizing tool to get optimal tuning of PSS parameters as well as the gains of PID controllers. For on-line, off-nominal operating conditions Takagi Sugeno Fuzzy Logic (TSFL) has been applied to obtain the off-nominal optimal gains of PID controllers and parameters of PSS. Implementation of TSFL helps to achieve very fast dynamic response. Fourth order model of generator with AVR and high gain thyristor excitation system is considered for PSS controlled system while normal gain exciter is considered for PID controlled system. Simulation study also reveals that with high gain exciter, PID control is not at all effective. Transient responses are achieved by using modal analysis. (author)

  10. From Actual Reality to Virtual Reality-AVR Theory, Techniques and Application

    Institute of Scientific and Technical Information of China (English)

    LIU Weibin; ZHANG Chao; YUAN Baozong

    2001-01-01

    In this paper, the basic theory and core techniques of AVR (from Actual Reality to Virtual Reality) have been expounded. AVR is a development of VR technique. In AVR, the virtual objects in virtual environment are modeled directly from the shape information of their counterparts in real world based on computer graphics and computer vision techniques, which provides the virtual environment with a higher level realism and preciseness. In order to achieve the integration of computer vision and computer graphics, superquadric based (SQ-based) model as the universal description of virtual objects is chosen and PAMVISION (Part-based Multiple-layer Visual Information Organization Model) model providing a general framework for vision recognition and reconstruction in AVR modeling is developed. As the core techniques of AVR, two approaches for virtualizing the real objects from either 2D images or 3D data are im plemented. As an application of AVR, an interactive 3D superquadric based modeling software package is developed for creating virtual environment.

  11. Pto- and Prf-mediated recognition of AvrPto and AvrPtoB restricts the ability of diverse pseudomonas syringae pathovars to infect tomato.

    Science.gov (United States)

    Lin, Nai-Chun; Martin, Gregory B

    2007-07-01

    The molecular basis underlying the ability of pathogens to infect certain plant species and not others is largely unknown. Pseudomonas syringae is a useful model species for investigating this phenomenon because it comprises more than 50 pathovars which have narrow host range specificities. Tomato (Solanum lycopersicum) is a host for P. syringae pv. tomato, the causative agent of bacterial speck disease, but is considered a nonhost for other P. syringae pathovars. Host resistance in tomato to bacterial speck disease is conferred by the Pto protein kinase which acts in concert with the Prf nucleotide-binding lucine-rich repeat protein to recognize P. syringae pv. tomato strains expressing the type III effectors AvrPto or AvrPtoB (HopAB2). The Pto and Prf genes were isolated from the wild tomato species S. pimpinellifolium and functional alleles of both of these genes now are known to exist in many species of tomato and in other Solanaceous species. Here, we extend earlier reports that avrPto and avrPtoB genes are widely distributed among pathovars of P. syringae which are considered nonhost pathogens of tomato. This observation prompted us to examine the possibility that recognition of these type III effectors by Pto or Prf might contribute to the inability of many P. syringae pathovars to infect tomato species. We show that 10 strains from presumed nonhost P. syringae pathovars are able to grow and cause pathovar-unique disease symptoms in tomato leaves lacking Pto or Prf, although they did not reach the population levels or cause symptoms as severe as a control P. syringae pv. tomato strain. Seven of these strains were found to express avrPto or avrPtoB. The AvrPto- and AvrPtoB-expressing strains elicited disease resistance on tomato leaves expressing Pto and Prf. Thus, a gene-for-gene recognition event may contribute to host range restriction of many P. syringae pathovars on tomato species. Furthermore, we conclude that the diverse disease symptoms caused by

  12. Multiple Activities of the Plant Pathogen Type III Effector Proteins WtsE and AvrE1 require WxxxE Motifs

    OpenAIRE

    Ham, Jong Hyun; Majerczak, Doris R.; Nomura, Kinya; Mecey, Christy; Uribe, Francisco de, (S.I.) (1613-1667); He, Sheng-Yang; Mackey, David; Coplin, David L.

    2009-01-01

    The broadly conserved AvrE-family of type III effectors from Gram-negative plant pathogenic bacteria includes important virulence factors, yet little is known about the mechanisms by which these effectors function inside plant cells to promote disease. We have identified two conserved motifs in AvrE-family effectors: a WxxxE motif and a putative C-terminal endoplasmic reticulum membrane retention/retrieval signal (ERMRS). The WxxxE and ERMRS motifs are both required for the virulence activiti...

  13. Giant planet formation via pebble accretion

    CERN Document Server

    Guilera, O M

    2015-01-01

    In the standard model of core accretion, the formation of giant planets occurs by two main processes: first, a massive core is formed by the accretion of solid material; then, when this core exceeds a critical value (typically greater than 10 Earth masses) a gaseous runaway growth is triggered and the planet accretes big quantities of gas in a short period of time until the planet achieves its final mass. Thus, the formation of a massive core has to occur when the nebular gas is still available in the disk. This phenomenon imposes a strong time-scale constraint in giant planet formation due to the fact that the lifetimes of the observed protoplanetary disks are in general lower than 10 Myr. The formation of massive cores before 10 Myr by accretion of big planetesimals (with radii > 10 km) in the oligarchic growth regime is only possible in massive disks. However, planetesimal accretion rates significantly increase for small bodies, especially for pebbles, particles of sizes between mm and cm, which are strong...

  14. Phytophthora sojae avirulence effector Avr3b is a secreted NADH and ADP-ribose pyrophosphorylase that modulates plant immunity.

    Directory of Open Access Journals (Sweden)

    Suomeng Dong

    2011-11-01

    Full Text Available Plants have evolved pathogen-associated molecular pattern (PAMP-triggered immunity (PTI and effector-triggered immunity (ETI to protect themselves from infection by diverse pathogens. Avirulence (Avr effectors that trigger plant ETI as a result of recognition by plant resistance (R gene products have been identified in many plant pathogenic oomycetes and fungi. However, the virulence functions of oomycete and fungal Avr effectors remain largely unknown. Here, we combined bioinformatics and genetics to identify Avr3b, a new Avr gene from Phytophthora sojae, an oomycete pathogen that causes soybean root rot. Avr3b encodes a secreted protein with the RXLR host-targeting motif and C-terminal W and Nudix hydrolase motifs. Some isolates of P. sojae evade perception by the soybean R gene Rps3b through sequence mutation in Avr3b and lowered transcript accumulation. Transient expression of Avr3b in Nicotiana benthamiana increased susceptibility to P. capsici and P. parasitica, with significantly reduced accumulation of reactive oxygen species (ROS around invasion sites. Biochemical assays confirmed that Avr3b is an ADP-ribose/NADH pyrophosphorylase, as predicted from the Nudix motif. Deletion of the Nudix motif of Avr3b abolished enzyme activity. Mutation of key residues in Nudix motif significantly impaired Avr3b virulence function but not the avirulence activity. Some Nudix hydrolases act as negative regulators of plant immunity, and thus Avr3b might be delivered into host cells as a Nudix hydrolase to impair host immunity. Avr3b homologues are present in several sequenced Phytophthora genomes, suggesting that Phytophthora pathogens might share similar strategies to suppress plant immunity.

  15. Multiple activities of the plant pathogen type III effector proteins WtsE and AvrE require WxxxE motifs.

    Science.gov (United States)

    Ham, Jong Hyun; Majerczak, Doris R; Nomura, Kinya; Mecey, Christy; Uribe, Francisco; He, Sheng-Yang; Mackey, David; Coplin, David L

    2009-06-01

    The broadly conserved AvrE-family of type III effectors from gram-negative plant-pathogenic bacteria includes important virulence factors, yet little is known about the mechanisms by which these effectors function inside plant cells to promote disease. We have identified two conserved motifs in AvrE-family effectors: a WxxxE motif and a putative C-terminal endoplasmic reticulum membrane retention/retrieval signal (ERMRS). The WxxxE and ERMRS motifs are both required for the virulence activities of WtsE and AvrE, which are major virulence factors of the corn pathogen Pantoea stewartii subsp. stewartii and the tomato or Arabidopsis pathogen Pseudomonas syringae pv. tomato, respectively. The WxxxE and the predicted ERMRS motifs are also required for other biological activities of WtsE, including elicitation of the hypersensitive response in nonhost plants and suppression of defense responses in Arabidopsis. A family of type III effectors from mammalian bacterial pathogens requires WxxxE and subcellular targeting motifs for virulence functions that involve their ability to mimic activated G-proteins. The conservation of related motifs and their necessity for the function of type III effectors from plant pathogens indicates that disturbing host pathways by mimicking activated host G-proteins may be a virulence mechanism employed by plant pathogens as well. PMID:19445595

  16. A method for estimating maximum static rainfall retention in pebble mulches used for soil moisture conservation

    Science.gov (United States)

    Peng, Hongtao; Lei, Tingwu; Jiang, Zhiyun; Horton, Robert

    2016-06-01

    Mulching of agricultural fields and gardens with pebbles has long been practiced to conserve soil moisture in some semi-arid regions with low precipitation. Rainfall interception by the pebble mulch itself is an important part of the computation of the water balance for the pebble mulched fields and gardens. The mean equivalent diameter (MED) was used to characterize the pebble size. The maximum static rainfall retention in pebble mulch is based on the water penetrating into the pores of pebbles, the water adhering to the outside surfaces of pebbles and the water held between pebbles of the mulch. Equations describing the water penetrating into the pores of pebbles and the water adhering to the outside surface of pebbles are constructed based on the physical properties of water and the pebble characteristics. The model for the water between pebbles of the mulch is based on the basic equation to calculate the water bridge volume and the basic coordination number model. A method to calculate the maximum static rainfall retention in the pebble mulch is presented. Laboratory rain simulation experiments were performed to test the model with measured data. Paired sample t-tests showed no significant differences between the values calculated with the method and the measured data. The model is ready for testing on field mulches.

  17. A new biotype of Fusarium oxysporum f. sp. lycopersici race 2 emerged by a transposon-driven mutation of avirulence gene AVR1.

    Science.gov (United States)

    Kashiwa, Takeshi; Suzuki, Tatsuya; Sato, Akira; Akai, Kotaro; Teraoka, Tohru; Komatsu, Ken; Arie, Tsutomu

    2016-07-01

    Emergence of races in Fusarium oxysporum f. sp. lycopersici (Fol) is caused by loss or mutation of at least one avirulence (AVR) gene. The product of AVR1 is a small protein (Avr1) secreted by Fol in tomato xylem sap during infection. This protein triggers Fol race 1 specific resistance (I) in tomato, indicating that AVR1 is an AVR gene. Deletion of AVR1 in race 1 resulted in the emergence of race 2, and an additional mutation in AVR2 generated race 3. Previously, we reported a new biotype of race 3, KoChi-1, in which AVR1 was truncated by a transposon Hormin, which suggested a new route to evolution of races in Fol However, to date no race 2 isolate carrying Hormin-truncated AVR1 has been reported. In this report, we describe such isolates, represented by Chiba-5, in which Hormin insertion occurred in AVR1 at a position different from that in KoChi-1. AVR1 truncation in both isolates resulted in production of defective Avr1 proteins. Chiba-5 and KoChi-1 belong to different phylogenetic clades, A1 and A2, respectively, suggesting that insertion of Hormin in AVR1 in Chiba-5 and KoChi-1 occurred as independent evolutionary events. PMID:27190160

  18. Analysis of Reversible Simulation of Irreversible Computation by Pebble Games

    CERN Document Server

    Li, Maozhen; Vitanyi, P; Li, Ming; Tromp, John; Vitanyi, Paul

    1998-01-01

    Reversible simulation of irreversible algorithms is analyzed in the stylized form of a `reversible' pebble game. While such simulations incur little overhead in additional computation time, they use a large amount of additional memory space during the computation. The reacheable reversible simulation instantaneous descriptions (pebble configurations) are characterized completely. As a corollary we obtain the reversible simulation by Bennett and that among all simulations that can be modelled by the pebble game, Bennett's simulation is optimal in that it uses the least auxiliary space for the greatest number of simulated steps. One can reduce the auxiliary storage overhead incurred by the reversible simulation at the cost of allowing limited erasing leading to an irreversibility-space tradeoff. We show that in this resource-bounded setting the limited erasing needs to be performed at precise instants during the simulation. We show that the reversible simulation can be modified so that it is applicable also whe...

  19. On the effect of AVR gain on bifurcations of subsynchronous resonance in power systems

    Energy Technology Data Exchange (ETDEWEB)

    Widyan, Mohammad S. [Electrical Engineering Department, The Hashemite University, 13115 Zarqa (Jordan)

    2010-07-15

    This paper presents the effect of the automatic voltage regulator (AVR) gain on the bifurcations of subsynchronous resonance (SSR) in power systems. The first system of the IEEE second benchmark model of SSR is chosen for numerical investigations. The dynamics of both axes damper windings of the generator and that of the power system stabilizer (PSS) are included. The bifurcation parameter is the compensation factor. Hopf bifurcation, where a pair of complex conjugate eigenvalues of the linearized model around the operating point transversally crosses from left- to right-half of the complex plane, is detected in all AVR gains. It is shown that the Hopf bifurcation is of subcritical type. The results also show that the location of the Hopf bifurcation point i.e. the stable operating point regions are affected by the value of the AVR gain. The variation of the location of the Hopf bifurcation point as function of the AVR gain for two operating conditions is obtained. Time domain simulation results based on the nonlinear dynamical mathematical model carried out at different compensation factors and AVR gains agree with that of the bifurcation analysis. (author)

  20. Conceptual study of ferromagnetic pebbles for heat exhaust in fusion reactors with short power decay length

    OpenAIRE

    Gierse, N.; Coenen, J W; C. Thomser; Panin, A.; Ch. Linsmeier; Unterberg, B.; Philipps, V

    2015-01-01

    Ferromagnetic pebbles are investigated as high heat flux (q∥) plasma facing components in fusion devices with short power decay length (λq) on a conceptual level. The ability of a pebble concept to cope with high heat fluxes is retained and extended by the acceleration of ferromagnetic pebbles in magnetic fields. An alloying concept suited for fusion application is outlined and the compatibility of ferromagnetic pebbles with plasma operation is discussed. Steel grade 1.4510 is chosen as a ...

  1. Conceptual study of ferromagnetic pebbles for heat exhaust in fusion reactors with short power decay length

    Directory of Open Access Journals (Sweden)

    N. Gierse

    2015-03-01

    The key results of this study are that very high heat fluxes are accessible in the operation space of ferromagnetic pebbles, that ferromagnetic pebbles are compatible with tokamak operation and current divertor designs, that the heat removal capability of ferromagnetic pebbles increases as λq decreases and, finally, that for fusion relevant values of q∥ pebble diameters below 100 μm are required.

  2. A novel reusable nanocomposite for complete removal of dyes, heavy metals and microbial load from water based on nanocellulose and silver nano-embedded pebbles.

    Science.gov (United States)

    Suman; Kardam, Abhishek; Gera, Meeta; Jain, V K

    2015-01-01

    The present work proposed a nanocellulose (NC)-silver nanoparticles (AgNPs) embedded pebbles-based composite material as a novel reusable cost-effective water purification device for complete removal of dyes, heavy metals and microbes. NC was prepared using acid hydrolysis of cellulose. The AgNPs were generated in situ using glucose and embedded within the porous concrete pebbles by the technique of inter-diffusion of ion, providing a very strong binding of nanoparticles within the porous pebbles and thus preventing any nanomaterials leaching. Fabrication of a continual running water purifier was achieved by making different layering of NC and Ag nano-embedded pebbles in a glass column. The water purifier exhibited not only excellent dye and heavy metal adsorption capacity, but also long-term antibacterial activity against pathogenic and non-pathogenic bacterial strains. The adsorption mainly occurred through electrostatic interaction and pore diffusion also contributed to the process. The bed column purifier has shown 99.48% Pb(II) and 98.30% Cr(III) removal efficiency along with 99% decontamination of microbial load at an optimum working pH of 6.0. The high adsorption capacity and reusability, with complete removal of dyes, heavy metals and Escherichia coli from the simulated contaminated water of composite material, will provide new opportunities to develop a cost-effective and eco-friendly water purifier for commercial application.

  3. Intelligent particle swarm optimized fuzzy PID controller for AVR system

    Energy Technology Data Exchange (ETDEWEB)

    Mukherjee, V. [Department of Electrical Engineering, Asansol Engineering College, Asansol, West Bengal (India); Ghoshal, S.P. [Department of Electrical Engineering, National Institute of Technology, Durgapur, West Bengal (India)

    2007-10-15

    In process plants like thermal power plants, biomedical instrumentation the popular use of proportional-integral-derivative (PID) controllers can be noted. Proper tuning of such controllers is obviously a prime priority as any other alternative situation will require a high degree of industrial expertise. So in order to get the best results of PID controllers the optimal tuning of PID gains is required. This paper, thus, deals with the determination of off-line, nominal, optimal PID gains of a PID controller of an automatic voltage regulator (AVR) for nominal system parameters and step reference voltage input. Craziness based particle swarm optimization (CRPSO) and binary coded genetic algorithm (GA) are the two props used to get the optimal PID gains. CRPSO proves to be more robust than GA in performing optimal transient performance even under various nominal operating conditions. Computational time required by CRPSO is lesser than that of GA. Factors that have influenced the enhancement of global searching ability of PSO are the incorporation of systematic and intelligent velocity, position updating procedure and introduction of craziness. This modified from of PSO is termed as CRPSO. For on-line off-nominal system parameters Sugeno fuzzy logic (SFL) is applied to get on-line terminal voltage response. The work of SFL is to extrapolate intelligently and linearly, the nominal optimal gains in order to determine off-nominal optimal gains. The on-line computational burden of SFL is noticeably low. Consequently, on-line optimized transient response of incremental change in terminal voltage is obtained. (author)

  4. Induction of avirulence by AVR-Pita1 in virulent U.S. field isolates of Magnaporthe oryzae’

    Institute of Scientific and Technical Information of China (English)

    Yuntao; Dai; Eugenia; Winston; James; C.Correll; Yulin; Jia

    2014-01-01

    The AVR-Pita1 gene,from the Chinese isolate O-137 of Magnaporthe oryzae,is an effector that determines the efficacy of the Pi-ta rice blast resistance gene.In the present study,the avirulence function of AVR-Pita1 was induced by transformation of field isolates(TM2,ZN19,B2 and B8)that originally were collected from the U.S.and are virulent on Pi-ta-carrying rice cultivars.The presence of AVR-Pita1 from O-137 in independent transformants was detected by PCR using AVR-Pita1 specific primers and verified by DNA sequencing and Southern blot analysis using the AVR-Pita1 coding region as a probe.The results of pathogenicity assays showed that the AVR-Pita1-transformed isolates were not able to infect rice cultivars Katy and Drew carrying Pi-ta.Control isolates that were transformed with inserts lacking the AVR-Pita1gene remained virulent.Our findings demonstrate that AVR-Pita1 can be used to induce novel gene-specific blast resistance in nature.

  5. Velocity relaxed and craziness-based swarm optimized intelligent PID and PSS controlled AVR system

    Energy Technology Data Exchange (ETDEWEB)

    Chatterjee, A.; Mukherjee, V. [Department of Electrical Engineering, Asansol Engineering College, Asansol, Vivekananda Sarani, Kanyapur, West Bengal 713305 (India); Ghoshal, S.P. [Department of Electrical Engineering, National Institute of Technology, Durgapur, West Bengal 713209 (India)

    2009-09-15

    This paper explores a comparative performance study of two new classes of particle swarm optimization techniques, one with velocity update relaxation (VURPSO) and the other based on novel position, velocity updating strategy and craziness (CRPSO). Both VURPSO and CRPSO highly enhance searching ability. Genetic algorithm (GA) is considered for the sake of comparison. Finally, it is revealed that while applying in two power systems applications (PID controlled AVR system, PSS controlled AVR system), VURPSO exhibits better transient performance than CRPSO/GA. For on-line, off-nominal conditions, Takagi Sugeno fuzzy logic is applied to obtain on-line responses for both the system models. (author)

  6. AVR: ПРОГРАММИРОВАНИЕ В СРЕДЕ AVR STUDIO

    OpenAIRE

    Королев, Николай; Королев, Дмитрий

    2004-01-01

    Для программирования AVR-микроконтроллеров существует немало средств разработки, однако, наиболее популярным, несомненно, следует признать пакет AVR Studio.

  7. 基于AVR Studio的STK500协议的实现%Implementation of Protocol STK500 Based on AVR Studio

    Institute of Scientific and Technical Information of China (English)

    刘平; 张志; 臧振刚; 张海东

    2008-01-01

    STK500协议是ATMEL公司为实现主机与STK500开发板之间相互通信而制定的协议,该协议的主机端软件平台是其官方软件AVR Studio,通过该软件能够很方便地对AVR器件进行仿真调试及下栽.本文使用AVR系列单片机ATMEGA16L完成了STK500协议的主要功能,从而能够通过AVR Studio方便地对AVR系列单片机进行编程和配置.

  8. Analyse de l’interaction entre les gènes d’avirulence AvrLm3 et AvrLm4-7 chez Leptosphaeria maculans

    OpenAIRE

    Plissonneau, Clémence; Balesdent, Marie-Helene; Fudal, Isabelle; Rouxel, Thierry

    2014-01-01

    Leptosphaeria maculans est un champignon ascomycète responsable de la nécrose du collet du colza, principale maladie sur cette culture. La méthode de lutte la plus utilisée contre cet agent pathogène est la lutte génétique. Celle-ci repose sur l'interaction entre un gène de résistance Rlm chez la plante et un gène d'avirulence AvrLm chez le champignon. L’un d’eux, AvrLm4-7, joue un rôle important dans la fitness fongique1 et a été cloné2. Récemment, nous avons mis en évidence une corrélation ...

  9. A review on packed bed solar energy storage systems

    Energy Technology Data Exchange (ETDEWEB)

    Singh, Harmeet; Saini, R.P. [Alternate Hydro Energy Centre, Indian Institute of Technology Roorkee, Roorkee 247667 (India); Saini, J.S. [Mechanical and Industrial Engineering Department, Indian Institute of Technology Roorkee, Roorkee 247667 (India)

    2010-04-15

    Because of intermittent nature of solar energy, storage is required for uninterrupted supply in order to match the needs. Packed beds are generally used for storage of thermal energy from solar air heaters. A packed bed is a volume of porus media obtained by packing particles of selected material into a container. A number of studies carried out on packed beds for their performance analysis were reported in the literature. These studies included the design of packed beds, materials used for storage, heat transfer enhancement, flow phenomenon and pressure drop through packed beds. This paper presents an extensive review on the research carried out on packed beds. Based on the literature review, it is concluded that most of the studies carried out are on rocks and pebbles as packing material. A very few studies were conducted on large sized packing materials. Further no study has been reported so far on medium sized storage elements in packed beds. (author)

  10. Modification of the AVR for high temperature process heat systems-demonstration

    International Nuclear Information System (INIS)

    The objectives for modification of the AVR for high temperature process heat systems were: systems demonstration for high temperature process heat application; systems demonstration for refinement of fossil fuels; contribution to products specifications, licensing procedures and approach to zero emissions. Investigations of horizontal integration were considered as well

  11. Evolution of an avirulence gene, AVR1-CO39, concomitant with the evolution and differentiation of Magnaporthe oryzae.

    Science.gov (United States)

    Tosa, Yukio; Osue, Jun; Eto, Yukiko; Oh, Hong-Sik; Nakayashiki, Hitoshi; Mayama, Shigeyuki; Leong, Sally A

    2005-11-01

    The significance of AVR1-CO39, an avirulence gene of the blast fungus corresponding to Pi-CO39(t) in rice cultivars, during the evolution and differentiation of the blast fungus was evaluated by studying its function and distribution in Pyricularia spp. When the presence or absence of AVR1-CO39 was plotted on a dendrogram constructed from ribosomal DNA sequences, a perfect parallelism was observed between its distribution and the phylogeny of Pyricularia isolates. AVR1-CO39 homologs were exclusively present in one species, Pyricularia oryzae, suggesting that AVR1-CO39 appeared during the early stage of evolution of P. oryzae. Transformation assays showed that all the cloned homologs tested are functional as an avirulence gene, indicating that selection has maintained their function. Nevertheless, Oryza isolates (isolates virulent on Oryza spp.) in P. oryzae were exceptionally noncarriers of AVR1-CO39. All Oryza isolates suffered from one of the two types of known rearrangements at the Avr1-CO39 locus (i.e., G type and J type). These types were congruous to the two major lineages of Oryza isolates from Japan determined by MGR586 and MAGGY. These results indicate that AVR1-CO39 was lost during the early stage of evolution of the Oryza-specific subgroup of P. oryzae. Interestingly, its corresponding resistance gene, Pi-CO39(t), is not widely distributed in Oryza spp. PMID:16353550

  12. Universal scaling relations for pebble abrasion

    Science.gov (United States)

    Litwin, K. L.; Jerolmack, D. J.

    2012-12-01

    The process of abrasion of gravel in bed load transport results from particle-to-particle collisions, where the energy involved is sufficient to cause chipping and spallation but not fragmentation of parent grains. The removed rock material is not infinitesimal; daughter products as large as coarse sand can be produced. Although previous work has shown that lithology, grain shape, and energy of collision are contributing factors that control abrasion rates of river-bed material, little is known regarding the relationship between these factors and diminution rates. Here we explicitly isolate and investigate how these three factors influence rates of abrasion and the size distribution of daughter products, with laboratory experiments. The apparatus is a double pendulum (Newton's cradle) that produces well-controlled binary collisions. A high-speed camera precisely measures collision energy, while mass of parent rocks. and the size and shape distributions of daughter products, are measured periodically. We examined abrasion of initially square-cut 'rocks' as they underwent successive collisions in the binary collision apparatus. We have examined mass loss rate for varied lithologies, and observe a similar power-law relationship between impact energy and mass abraded. When normalized by sensible material properties, mass loss curves for all materials collapse onto a single curve, suggesting that the underlying mechanics of abrasion for different materials are the same. The relationship does not display the linear trend expected from pure energetics, and we suggest that this is a shape effect as protruding - and hence easily eroded - corners are worn away. Analysis of daughter-product particle size distributions for different lithology fragments - including natural rocks and also bricks - show the same functional form. Surprisingly, it is the power-law relation expected for brittle materials undergoing fragmentation. This suggests that brittle fracture theory also

  13. Tritium release from EXOTIC-7 orthosilicate pebbles. Effect of burnup and contact with beryllium during irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Scaffidi-Argentina, F.; Werle, H. [Forschungszentrum Karlsruhe GmbH Technik und Umwelt (Germany). Inst. fuer Neutronenphysik und Reaktortechnik

    1998-03-01

    EXOTIC-7 was the first in-pile test with {sup 6}Li-enriched (50%) lithium orthosilicate (Li{sub 4}SiO{sub 4}) pebbles and with DEMO representative Li-burnup. Post irradiation examinations of the Li{sub 4}SiO{sub 4} have been performed at the Forschungszentrum Karlsruhe (FZK), mainly to investigate the tritium release kinetics as well as the effect of Li-burnup and/or contact with beryllium during irradiation. The release rate of Li{sub 4}SiO{sub 4} from pure Li{sub 4}SiO{sub 4} bed of capsule 28.1-1 is characterized by a broad main peak at about 400degC and by a smaller peak at about 800degC, and that from the mixed beds of capsule 28.2 and 26.2-1 shows again these two peaks, but most of the tritium is now released from the 800degC peak. This shift of release from low to high temperature may be due to the higher Li-burnup and/or due to contact with Be during irradiation. Due to the very difficult interpretation of the in-situ tritium release data, residence times have been estimated on the basis of the out-of-pile tests. The residence time for Li{sub 4}SiO{sub 4} from caps. 28.1-1 irradiated at 10% Li-burnup agrees quite well with that of the same material irradiated at Li-burnup lower than 3% in the EXOTIC-6 experiment. In spite of the observed shift in the release peaks from low to high temperature, also the residence time for Li{sub 4}SiO{sub 4} from caps. 26.2-1 irradiated at 13% Li-burnup agrees quite well with the data from EXOTIC-6 experiment. On the other hand, the residence time for Li{sub 4}SiO{sub 4} from caps. 28.2 (Li-burnup 18%) is about a factor 1.7-3.8 higher than that for caps. 26.2-1. Based on these data on can conclude that up to 13% Li-burnup neither the contact with beryllium nor the Li-burnup have a detrimental effect on the tritium release of Li{sub 4}SiO{sub 4} pebbles, but at 18% Li-burnup the residence time is increased by about a factor three. (J.P.N.)

  14. Use of Single-Chip Microprocessors AVR ATMEL for Measurement of Distance

    OpenAIRE

    JŮZA, Zdeněk

    2011-01-01

    The bachelor's thesis deals with the construction of a measuring tool that will probably enable substitution of the vernier scale in manually controlled machine tools. It also treats a possible use of the AVR ATMEL circuit for these applications. The sensor used for measuring the distance is the magnetic linear encoder AS5311. The thesis also presents the analysis of a prototype design using an AT MEGA 32 microcontroller and a AS5311 sensor . The output of the measuring device is displayed on...

  15. Positive selection in AvrP4 avirulence gene homologues across the genus Melampsora.

    Science.gov (United States)

    Van der Merwe, Marlien M; Kinnear, Mark W; Barrett, Luke G; Dodds, Peter N; Ericson, Lars; Thrall, Peter H; Burdon, Jeremy J

    2009-08-22

    Pathogen genes involved in interactions with their plant hosts are expected to evolve under positive Darwinian selection or balancing selection. In this study a single copy avirulence gene, AvrP4, in the plant pathogen Melampsora lini, was used to investigate the evolution of such a gene across species. Partial translation elongation factor 1-alpha sequences were obtained to establish phylogenetic relationships among the Melampsora species. We amplified AvrP4 homologues from species pathogenic on hosts from different plant families and orders, across the inferred phylogeny. Translations of the AvrP4 sequences revealed a predicted signal peptide and towards the C-terminus of the protein, six identically spaced cysteines were identified in all sequences. Maximum likelihood analysis of synonymous versus non-synonymous substitution rates indicated that positive selection played a role in the evolution of the gene during the diversification of the genus. Fourteen codons under significant positive selection reside in the C-terminal 28 amino acid region, suggesting that this region interacts with host molecules in most sequenced accessions. Selection pressures on the gene may be either due to the pathogenicity or avirulence function of the gene or both.

  16. High temperature chemical compatibility between SiC composites and Be pebbles

    International Nuclear Information System (INIS)

    SiC composite reinforced fibres are still considered to be an important material to be used in nuclear fusion reactors due to their high temperature and low neutron activation properties. Two different kinds of SiC/SiCf composite were manufactured, one of them presenting an extra SiC coating obtained by chemical vapour deposition technique. Several samples of both materials were placed inside a Be pebble bed and the whole set-up annealed at 800 deg. C for 550 h in a reducing atmosphere, simulating fusion reactor conditions. Surface chemical reactions were investigated with nuclear microprobe analyses techniques and complemented with SEM analysis. For the uncoated samples, surface oxidation is accompanied by a strong C depletion and a Be diffusion. Two different behaviours were found for the coated samples. One of those samples showed extended regions where surface was left almost unaltered. The general behaviour, however, was an increase in the number and extension of the cracks already observed at the surface of the coated virgin samples

  17. Stepped-anneal helium release in 1-mm beryllium pebbles from COBRA-1A2

    Energy Technology Data Exchange (ETDEWEB)

    Oliver, B.M. [Pacific Northwest National Lab., Richland, WA (United States)

    1998-03-01

    Stepped-anneal helium release measurements on two sets of fifteen beryllium pebbles irradiated in the Experimental Breeder Reactor-II (EBR-II) at Argonne National Laboratory-West (ANL-w), are reported. The purpose of the measurements was to determine the helium release characteristics of the beryllium using larger sample sizes and longer anneal times relative to earlier measurements. Sequential helium analyses were conducted over a narrower temperature range from approximately 800 C to 1100 C in 100 C increments, but with longer anneal time periods. To allow for overnight and unattended operation, a temperature controller and associated circuitry were added to the experimental setup. Observed helium release was nonlinear with time at each temperature interval, with each step being generally characterized by an initial release rate followed by a slowing of the rate over time. Sample Be-C03 showed a leveling off in the helium release after approximately 3 hours at a temperature of 890 C. Sample Be-D03, on the other hand, showed a leveling off only after {approximately}12 to 24 hours at a temperature of 1100 C. This trend is consistent with that observed in earlier measurements on single microspheres from the same two beryllium lots. None of the lower temperature steps showed any leveling off of the helium release. Relative to the total helium concentrations measured earlier, the total helium releases observed here represent approximately 80% and 92% of the estimated total helium in the C03 and D03 samples, respectively.

  18. Coevolutionary Dynamics of Rice Blast Resistance Gene Pi-ta and Magnaporthe oryzae Avirulence Gene AVR-Pita 1.

    Science.gov (United States)

    Jia, Yulin; Zhou, Erxun; Lee, Seonghee; Bianco, Tracy

    2016-07-01

    The Pi-ta gene in rice is effective in preventing infections by Magnaporthe oryzae strains that contain the corresponding avirulence gene, AVR-Pita1. Diverse haplotypes of AVR-Pita1 have been identified from isolates of M. oryzae from rice production areas in the United States and worldwide. DNA sequencing and mapping studies have revealed that AVR-Pita1 is highly unstable, while expression analysis and quantitative resistance loci mapping of the Pi-ta locus revealed complex evolutionary mechanisms of Pi-ta-mediated resistance. Among these studies, several Pi-ta transcripts were identified, most of which are probably derived from alternative splicing and exon skipping, which could produce functional resistance proteins that support a new concept of coevolution of Pi-ta and AVR-Pita1. User-friendly DNA markers for Pi-ta have been developed to support marker-assisted selection, and development of new rice varieties with the Pi-ta markers. Genome-wide association studies revealed a link between Pi-ta-mediated resistance and yield components suggesting that rice has evolved a complicated defense mechanism against the blast fungus. In this review, we detail the current understanding of Pi-ta allelic variation, its linkage with rice productivity, AVR-Pita allelic variation, and the coevolution of Pi-ta and AVR-Pita in Oryza species and M. oryzae populations, respectively. We also review the genetic and molecular basis of Pi-ta and AVR-Pita interaction, and its value in marker-assisted selection and engineering resistance. PMID:27070427

  19. Production of various sizes and some properties of beryllium pebbles by the rotating electrode method

    Energy Technology Data Exchange (ETDEWEB)

    Iwadachi, T.; Sakamoto, N.; Nishida, K. [NGK Insulators Ltd., Nagoya (Japan); Kawamura, H.

    1998-01-01

    The particle size distribution of beryllium pebbles produced by the rotating electrode method was investigated. Particle size depends on some physical properties and process parameters, which can practicaly be controlled by varying electrode angular velocities. The average particle sizes produced were expressed by the hyperbolic function with electrode angular velocity. Particles within the range of 0.3 and 2.0 mm in diameter are readily produced by the rotating electrode method while those of 0.2 mm in diameter are also fabricable. Sphericity and surface roughness were good in each size of pebble. Grain sizes of the pebbles are 17 {mu} m in 0.25 mm diameter pebbles and 260 {mu} m in 1.8 mm diameter pebbles. (author)

  20. Challenges in Forming the Solar System's Giant Planet Cores via Pebble Accretion

    CERN Document Server

    Kretke, K A

    2014-01-01

    Though ~10 Earth mass rocky/icy cores are commonly held as a prerequisite for the formation of gas giants, theoretical models still struggle to explain how these embryos can form within the lifetimes of gaseous circumstellar disks. In recent years, aerodynamic-aided accretion of "pebbles," objects ranging from centimeters to meters in size, has been suggested as a potential solution to this long-standing problem. While pebble accretion has been demonstrated to be extremely effective in local simulations that look at the detailed behavior of these pebbles in the vicinity of a single planetary embryo, to date there have been no global simulations demonstrating the effectiveness of pebble accretion in a more complicated, multi-planet environment. Therefore, we have incorporated the aerodynamic-aided accretion physics into LIPAD, a Lagrangian code which can follow the collisional / accretional / dynamical evolution of a protoplanetary system, to investigate the how pebble accretion manifests itself in the larger ...

  1. Conceptual Design Studies of a Passively Safe Thorium Breeder Pebble Bed Reactor

    OpenAIRE

    Wols, F.J.

    2015-01-01

    Nuclear power plants are expected to play an important role in the worldwide electricity production in the coming decades, since they provide an economically attractive, reliable and low-carbon source of electricity with plenty of resources available for at least the coming hundreds of years. However, the design of nuclear reactors can be improved significantly in terms of safety, by designing reactors with fully passive safety systems, and sustainability, by making more efficient use of natu...

  2. Conceptual Design Studies of a Passively Safe Thorium Breeder Pebble Bed Reactor

    NARCIS (Netherlands)

    Wols, F.J.

    2015-01-01

    Nuclear power plants are expected to play an important role in the worldwide electricity production in the coming decades, since they provide an economically attractive, reliable and low-carbon source of electricity with plenty of resources available for at least the coming hundreds of years. Howeve

  3. Some simulation aspects, from molecular systems to stochastic geometries of pebble bed reactors

    International Nuclear Information System (INIS)

    After a brief presentation of his teaching and supervising activities, the author gives an overview of his research activities: investigation of atoms under high intensity magnetic field (investigation of the electronic structure under these fields), studies of theoretical and numerical electrochemistry (simulation coupling molecular dynamics and quantum calculations, comprehensive simulations of molecular dynamics), and studies relating stochastic geometry and neutron science

  4. South Africa's Pebble Bed Modular Reactor, a new design for our nuclear future

    International Nuclear Information System (INIS)

    Power Utilities will in the future need to look at various means of generating power during the 21st century. The demands regarding new generation are challenged by such issues as; costs, time to construct, the add on safety requirements of present day nuclear power plant designs and the emissions generated by fossil fuels as reflected in the Kyoto Protocol. These challenges are also aligned with the deforestation, land decimation and releases of methane gas caused by the so-called 'clean' Hydro power plants in many parts of the world. Presently South Africa is looking at various generation mixes for the future. Although the demand in South Africa is currently lower than the capacity, it is anticipated that new capacity will have to be commissioned by about 2008. Even the moderate growth of 2,5% (as was experienced in our last fiscal year) will result in peak electricity demand exceeding capacity between 2005 and 2010. In addition, Eskom's older power stations reach the end of their design life after 2025. South Africa will, therefore, need to access and use all natural resources to produce the additional 20,000MW of electricity that will be needed by 2025 this will of course include a nuclear option. Throughout the world, it is noted that, along with the environmental issues affecting power generation the real leading issue is cost. South Africa has one of the lowest power costs in the world, based on its abundant low-cost coal. As with other Eskom low cost options such as, coal fired generation situated at the pit-head and imported hydro, the PBMR costs will have to meet these demanding cost targets set by Eskom's existing power plants. However, PBMR is virtually independent of location and the intention is that PBMR costs will be in the order of US 2,0c/kWh. The costs of decommissioning, long-term storage of radioactive waste and insurance are included in these estimates. This cost per unit of electricity produced would, however, be much lower than a coal-fired plant at the South African coast or the world average cost of US 3,4c/kWh. The paper presented will discuss the PBMR technology designed to meet the various demands and challenges placed upon power producers world wide; that is: - the need for Low Cost, Environmentally Friendly and Safe power production

  5. Molecular screening for avirulence alleles AvrLm1 and AvrLm6 in airborne inoculum of Leptosphaeria maculans and winter oilseed rape (Brassica napus) plants from Poland and the UK.

    Science.gov (United States)

    Kaczmarek, Joanna; Latunde-Dada, Akinwunmi O; Irzykowski, Witold; Cools, Hans J; Stonard, Jenna F; Brachaczek, Andrzej; Jedryczka, Malgorzata

    2014-11-01

    A combination of staining, light microscopy and SYBR green- and dual-labelled fluorescent probe-based qPCR chemistries with species- and gene-specific primers was employed to evaluate fluctuations in the aerial biomass of Leptosphaeria maculans spores captured by volumetric spore trappings in Poznan, Poland (2006, 2008) and Harpenden, UK (2002, 2006). Arising from these surveys, DNA samples extracted from Burkard spore-trap tapes were screened for fluctuation patterns in the frequencies of AvrLm1 and AvrLm6, the most prominent of the 15 genes that code for avirulence effectors in this Dothideomycete cause of the destructive phoma stem canker disease of oilseed rape worldwide. In Poznan, very low frequencies of AvrLm1 allele were found in the autumn of both 2006 and 2008, reflecting significantly increased cultivation of rape seed with Rlm1-based resistance. In contrast, at least six folds-higher frequencies of AvrLm6, which were also confirmed by end-point PCR bioassays on phoma-infected leaves from the same region of Poland, were obtained during both years. In the UK, however, relatively higher AvrLm1 allele titres were found in L. maculans spores captured in air samples from the autumn of 2002 on the experimental fields of Rothamsted Research, Harpenden, that were historically sown to genetically heterogeneous B. napus cultivars. In the 2006 screen these levels had plummeted, to a 1:4 ratio, in favour of frequencies of the AvrLm6 allele. Patterns of fluctuations in erg11 (CYP51) fragments coding for sterol 14α-demethylase suggest October as the month with the most viable wind-dispersed L. maculans propagules of each season of the screens. PMID:25081837

  6. The Pseudomonas syringae Type III Effector AvrRpt2 Promotes Pathogen Virulence via Stimulating Arabidopsis Auxin/Indole Acetic Acid Protein Turnover1[C][W][OA

    Science.gov (United States)

    Cui, Fuhao; Wu, Shujing; Sun, Wenxian; Coaker, Gitta; Kunkel, Barbara; He, Ping; Shan, Libo

    2013-01-01

    To accomplish successful infection, pathogens deploy complex strategies to interfere with host defense systems and subvert host physiology to favor pathogen survival and multiplication. Modulation of plant auxin physiology and signaling is emerging as a common virulence strategy for phytobacteria to cause diseases. However, the underlying mechanisms remain largely elusive. We have previously shown that the Pseudomonas syringae type III effector AvrRpt2 alters Arabidopsis (Arabidopsis thaliana) auxin physiology. Here, we report that AvrRpt2 promotes auxin response by stimulating the turnover of auxin/indole acetic acid (Aux/IAA) proteins, the key negative regulators in auxin signaling. AvrRpt2 acts additively with auxin to stimulate Aux/IAA turnover, suggesting distinct, yet proteasome-dependent, mechanisms operated by AvrRpt2 and auxin to control Aux/IAA stability. Cysteine protease activity is required for AvrRpt2-stimulated auxin signaling and Aux/IAA degradation. Importantly, transgenic plants expressing the dominant axr2-1 mutation recalcitrant to AvrRpt2-mediated degradation ameliorated the virulence functions of AvrRpt2 but did not alter the avirulent function mediated by the corresponding RPS2 resistance protein. Thus, promoting auxin response via modulating the stability of the key transcription repressors Aux/IAA is a mechanism used by the bacterial type III effector AvrRpt2 to promote pathogenicity. PMID:23632856

  7. A large family of AvrLm6-like genes in the apple and pear scab pathogens, Venturia inaequalis and Venturia pirina

    Directory of Open Access Journals (Sweden)

    Jason eShiller

    2015-11-01

    Full Text Available Venturia inaequalis and V. pirina are Dothideomycete fungi that cause apple scab and pear scab disease respectively. Whole genome sequencing of V. inaequalis and V. pirina isolates has revealed predicted proteins with sequence similarity to AvrLm6, a Leptosphaeria maculans effector that triggers a resistance response in Brassica napus and Brassica juncea carrying the resistance gene, Rlm6. AvrLm6-like genes are present as large families (> 16 members in all sequenced strains of V. inaequalis and V. pirina, while in L. maculans, only AvrLm6 and a single paralogue have been identified. The Venturia AvrLm6-like genes are located in gene poor regions of the genomes, and mostly in close proximity to transposable elements which may explain the expansion of these gene families. An AvrLm6-like gene from V. inaequalis with the highest sequence identity to AvrLm6 was unable to trigger a resistance response in Rlm6 carrying Brassica juncea. RNA-seq and qRT-PCR gene expression analyses, of in planta and in vitro grown V. inaequalis, has revealed that many of the AvrLm6-like genes are expressed during infection. An AvrLm6 homologue from V. inaequalis that is up-regulated during infection was shown (using a YFP-fusion protein construct to be localized to the sub-cuticular stroma during infection of apple hypocotyls.

  8. Results of the safety evaluation for the AVR-modification into a nuclear process heat plant

    International Nuclear Information System (INIS)

    In 1983 the Juelich Nuclear Research Center (KFA) proposed the modification of the AVR for high-temperature process heat systems demonstration. This would represent the achievement of an important HTR target. The work for the modification performed so far has given evidence that the plant will continue to run reliably and has led to an optimized plant concept. Most of the investigations were devoted to safety issues. The safety and licensing questions were discussed by an advisory group of the German Federal Ministry of the Interior which gave its vote in March 1985 and came to very positive conclusions. The AVR fulfils the current safety and licensing requirements; for the proposed plant modification no severe backfitting has to be taken into account. The AVR-building and the reactor itself turned out to be earthquake-proof, even according to current licensing demands if realistic site-specific earthquake spectra are applied. Risk assessment of an airplane crash show that the public risk is negligible even in the case of unrealistically pessimistic assumptions concerning the release of radioactivity. The modified plant will have a confinement similar to the modern German HTR-design. The investigations have shown that the safety questions related to a steam reformer in a primary circuit system are solved. All consequences of process gas release into the safety enclosure or into the primary system are controlled effectively by active and passive measures. Process gas release in the vicinity of the nuclear plant is excluded by the plant concept. Furthermore, even the hypothetical assumption of process gas explosions cannot damage the essential safety functions. (author)

  9. AVR microcontroller simulator for software implemented hardware fault tolerance algorithms research

    Science.gov (United States)

    Piotrowski, Adam; Tarnowski, Szymon; Napieralski, Andrzej

    2008-01-01

    Reliability of new, advanced electronic systems becomes a serious problem especially in places like accelerators and synchrotrons, where sophisticated digital devices operate closely to radiation sources. One of the possible solutions to harden the microprocessor-based system is a strict programming approach known as the Software Implemented Hardware Fault Tolerance. Unfortunately, in real environments it is not possible to perform precise and accurate tests of the new algorithms due to hardware limitation. This paper highlights the AVR-family microcontroller simulator project equipped with an appropriate monitoring and the SEU injection systems.

  10. Fabrication of Li{sub 2}TiO{sub 3} pebbles by a freeze drying process

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Sang-Jin, E-mail: lee@mokpo.ac.kr [Department of Advanced Materials Science and Engineering, Mokpo National University, Muan 534-729 (Korea, Republic of); Park, Yi-Hyun [National Fusion Research Institute, Daejeon 305-806 (Korea, Republic of); Yu, Min-Woo [Department of Advanced Materials Science and Engineering, Mokpo National University, Muan 534-729 (Korea, Republic of)

    2013-11-15

    Li{sub 2}TiO{sub 3} pebbles were successfully fabricated by using a freeze drying process. The Li{sub 2}TiO{sub 3} slurry was prepared using a commercial powder of particle size 0.5–1.5 μm and the pebble pre-form was prepared by dropping the slurry into liquid nitrogen through a syringe needle. The droplets were rapidly frozen, changing their morphology to spherical pebbles. The frozen pebbles were dried at −10 °C in vacuum. To make crack-free pebbles, some glycerin was employed in the slurry, and long drying time and a low vacuum condition were applied in the freeze drying process. In the process, the solid content in the slurry influenced the spheroidicity of the pebble green body. The dried pebbles were sintered at 1200 °C in an air atmosphere. The sintered pebbles showed almost 40% shrinkage. The sintered pebbles revealed a porous microstructure with a uniform pore distribution and the sintered pebbles were crushed under an average load of 50 N in a compressive strength test. In the present study, a freeze drying process for fabrication of spherical Li{sub 2}TiO{sub 3} pebbles is introduced. The processing parameters, such as solid content in the slurry and the conditions of freeze drying and sintering, are also examined.

  11. Uranium deposits in Proterozoic quartz-pebble conglomerates

    International Nuclear Information System (INIS)

    This report is the result of an effort to gather together the most important information on uranium deposits in Proterozoic quartz-pebble conglomerates in the United States of America, Canada, Finland, Ghana, South Africa and Australia. The paper discusses the uranium potential (and in some cases also the gold potential in South Africa, Western Australia and Ghana) in terms of ores, sedimentation, mineralization, metamorphism, placers, geologic formations, stratigraphy, petrology, exploration, tectonics and distribution. Geologic history and application of geologic models are also discussed. Glacial outwash and water influx is also mentioned. The uranium deposits in a number of States in the USA are covered. The Witwatersrand placers are discussed in several papers. Refs, figs, tabs

  12. Multiple translocation of the AVR-Pita effector gene among chromosomes of the rice blast fungus Magnaporthe oryzae and related species.

    Directory of Open Access Journals (Sweden)

    Izumi Chuma

    2011-07-01

    Full Text Available Magnaporthe oryzae is the causal agent of rice blast disease, a devastating problem worldwide. This fungus has caused breakdown of resistance conferred by newly developed commercial cultivars. To address how the rice blast fungus adapts itself to new resistance genes so quickly, we examined chromosomal locations of AVR-Pita, a subtelomeric gene family corresponding to the Pita resistance gene, in various isolates of M. oryzae (including wheat and millet pathogens and its related species. We found that AVR-Pita (AVR-Pita1 and AVR-Pita2 is highly variable in its genome location, occurring in chromosomes 1, 3, 4, 5, 6, 7, and supernumerary chromosomes, particularly in rice-infecting isolates. When expressed in M. oryzae, most of the AVR-Pita homologs could elicit Pita-mediated resistance, even those from non-rice isolates. AVR-Pita was flanked by a retrotransposon, which presumably contributed to its multiple translocation across the genome. On the other hand, family member AVR-Pita3, which lacks avirulence activity, was stably located on chromosome 7 in a vast majority of isolates. These results suggest that the diversification in genome location of AVR-Pita in the rice isolates is a consequence of recognition by Pita in rice. We propose a model that the multiple translocation of AVR-Pita may be associated with its frequent loss and recovery mediated by its transfer among individuals in asexual populations. This model implies that the high mobility of AVR-Pita is a key mechanism accounting for the rapid adaptation toward Pita. Dynamic adaptation of some fungal plant pathogens may be achieved by deletion and recovery of avirulence genes using a population as a unit of adaptation.

  13. The receptor-like kinase SOBIR1 interacts with Brassica napus LepR3 and is required for Leptosphaeria maculans AvrLm1-triggered immunity

    Directory of Open Access Journals (Sweden)

    Lisong eMa

    2015-10-01

    Full Text Available AbstractThe fungus Leptosphaeria maculans (L. maculans is the causal agent of blackleg disease of canola/oilseed rape (Brassica napus worldwide. We previously reported cloning of the B. napus blackleg resistance gene, LepR3, which encodes a receptor-like protein. LepR3 triggers localised cell death upon recognition of its cognate Avr protein, AvrLm1. Here, we exploited the Nicotiana benthamiana model plant to investigate the recognition mechanism of AvrLm1 by LepR3. Co-expression of the LepR3/AvrLm1 gene pair in N. benthamiana resulted in development of a hypersensitive response (HR. However, a truncated AvrLm1 lacking its indigenous signal peptide was compromised in its ability to induce LepR3-mediated HR, indicating that AvrLm1 is perceived by LepR3 extracellularly. Structure-function analysis of the AvrLm1 protein revealed that the C-terminal region of AvrLm1 was required for LepR3-mediated HR in N. benthamiana and for resistance to L. maculans in B. napus. LepR3 was shown to be physically interacting with the B. napus receptor like kinase, SOBIR1 (BnSOBIR1. Silencing of NbSOBIR1 or NbSERK3 (BAK1 compromised LepR3-AvrLm1-dependent HR in N. benthamiana, suggesting that LepR3-mediated resistance to L. maculans in B. napus requires SOBIR1 and BAK1/SERK3. Using this model system, we determined that BnSOBIR1 and SERK3/BAK1 are essential partners in the LepR3 signalling complex and were able to define the AvrLm1 effector domain.

  14. Measurement of after-heat production and dose rates of spent AVR fuel elements

    International Nuclear Information System (INIS)

    Data on the afterheat production and dose rate of spent AVR fuel elements prepared by the ORIGEN computer program are verified by measurements. Individual measurements of afterheat and dose rate were implemented on 17 AVR fuel elements with decay periods of 150 days and more than four years, and burnups between 4.1 and 16.4% fima were implemented in the HOT CELLS at the Juelich Nuclear Research Centre. The radiation energy absorbed in the fuel elements and converted into heat was measured with a calorimeter, whereas the emitted radiation fraction was determined via dose rate measurements. The measured results for fuel elements with decay periods of more than one year are in good agreement with the data from ORIGEN. In the case of fuel elements with shorter decay periods (approx. 150 days) in part considerably lower values were measured which can be explained by the fact that the power gradient in time of the fuel elements in the reactor can vary considerably whereas mean are included in the ORIGEN computations assuming full-load operation. (orig./HP))

  15. Implementation of a Microcode-controlled State Machine and Simulator in AVR Microcontrollers (MICoSS

    Directory of Open Access Journals (Sweden)

    S. Korbel

    2005-01-01

    Full Text Available This paper describes the design of a microcode-controlled state machine and its software implementation in Atmel AVR microcontrollers. In particular, ATmega103 and ATmega128 microcontrollers are used. This design is closely related to the software implementation of a simulator in AVR microcontrollers. This simulator communicates with the designed state machine and presents a complete design environment for microcode development and debugging. These two devices can be interconnected by a flat cable and linked to a computer through a serial or USB interface.Both devices share the control software that allows us to create and edit microprograms and to control the whole state machine. It is possible to start, cancel or step through the execution of the microprograms. The operator can also observe the current state of the state machine. The second part of the control software enables the operator to create and compile simulating programs. The control software communicates with both devices using commands. All the results of this communication are well arranged in dialog boxes and windows. 

  16. The role of pebble fragmentation in planetesimal formation II. Numerical simulations

    CERN Document Server

    Jansson, Karl Wahlberg; Syed, Mohtashim Bukhari; Blum, Jürgen

    2016-01-01

    Some scenarios for planetesimal formation go through a phase of collapse of gravitationally bound clouds of mm-cm-sized pebbles. Such clouds can form for example through the streaming instability in protoplanetary disks. We model the collapse process with a statistical model to obtain the internal structure of planetesimals with solid radii between 10 and 1,000 km. In the collapse, pebbles collide and, depending on relative speed, collisions have different outcomes. A mixture of particle sizes inside a planetesimal leads to better packing capabilities and higher densities. In this paper we apply results from new laboratory experiments of dust aggregate collisions (presented in a companion paper) to model collision outcomes. We find that the internal structure of a planetesimal is strongly dependent on both its mass and the applied fragmentation model. Low-mass planetesimals have no/few fragmenting pebble collisions in the collapse phase and end up as porous pebble-piles. The amount of fragmenting collisions i...

  17. The crystal structure of Pseudomonas avirulence protein AvrPphB: A papain-like fold with a distinct substrate binding site

    Energy Technology Data Exchange (ETDEWEB)

    Zhu, M.; Shao, F.; Innes, R.W.; Dixon, J.E.; Xu, Z. (Mighigan); (Michigan); (UCSD)

    2010-03-08

    AvrPphB is an avirulence (Avr) protein from the plant pathogen Pseudomonas syringae that can trigger a disease-resistance response in a number of host plants including Arabidopsis. AvrPphB belongs to a novel family of cysteine proteases with the charter member of this family being the Yersinia effector protein YopT. AvrPphB has a very stringent substrate specificity, catalyzing a single proteolytic cleavage in the Arabidopsis serine/threonine kinase PBS1. We have determined the crystal structure of AvrPphB by x-ray crystallography at 1.35-{angstrom} resolution. The structure is composed of a central antiparallel {beta}-sheet, with {alpha}-helices packing on both sides of the sheet to form a two-lobe structure. The core of this structure resembles the papain-like cysteine proteases. The similarity includes the AvrPphB active site catalytic triad of Cys-98, His-212, and Asp-227 and the oxyanion hole residue Asn-93. Based on analogy with inhibitor complexes of the papain-like proteases, we propose a model for the substrate-binding mechanism of AvrPphB. A deep and positively charged pocket (S2) and a neighboring shallow surface (S3) likely bind to aspartic acid and glycine residues in the substrate located two (P2) and three (P3) residues N terminal to the cleavage site, respectively. Further implications about the specificity of plant pathogen recognition are also discussed.

  18. Wild-type and mutant AvrA- Salmonella induce broadly similar immune pathways in the chicken ceca with key differences in signaling intermediates and inflammation.

    Science.gov (United States)

    Arsenault, Ryan J; Genovese, Kenneth J; He, Haiqi; Wu, Huixia; Neish, Andrew S; Kogut, Michael H

    2016-02-01

    Salmonella enterica serovar Typhimurium (ST) is a serious infectious disease throughout the world, and a major reservoir for Salmonella is chicken. Chicken infected with Salmonella do not develop clinical disease, this may be the result of important host interactions with key virulence proteins. To study this, we inoculated chicken with mutant Salmonella Typhimurium that lacked the virulence protein AvrA (AvrA(-)). AvrA is referred to as an avirulence factor, as it moderates the host immune response. The lack of the AvrA virulence gene in ST resulted in reduced weight gain, enhanced persistence and greater extraintestinal organ invasion in chickens, as compared to wild-type (WT) ST. Kinome analysis was performed on inoculated cecal tissue. The majority of the signal transduction pathways induced by AvrA(-) and WT ST were similar; however, we observed alterations in innate immune system signaling. In addition, a leukocyte migration pathway was altered by AvrA(-) ST that may allow greater gut barrier permeability and invasion by the mutant. Cytokine expression did not appear significantly altered at 7 d post-inoculation; at 14 d post-inoculation, there was an observed increase in the expression of anti-inflammatory IL-10 in the WT inoculated ceca. This study is the first to describe mutant AvrA(-) ST infection of chicken and provides further insight into the Salmonella responses observed in chicken relative to other species such as humans and cattle.

  19. Structural Analysis of Pseudomonas syringae AvrPtoB Bound to Host BAK1 Reveals Two Similar Kinase-Interacting Domains in a Type III Effector

    Science.gov (United States)

    Cheng, Wei; Munkvold, Kathy R.; Gao, Haishan; Mathieu, Johannes; Schwizer, Simon; Wang, Sha; Yan, Yong-bin; Wang, Jinjing; Martin, Gregory B.; Chai, Jijie

    2013-01-01

    SUMMARY To infect plants, Pseudomonas syringae pv. tomato delivers ~30 type III effector proteins into host cells, many of which interfere with PAMP-triggered immunity (PTI). One effector, AvrPtoB, suppresses PTI using a central domain to bind host BAK1, a kinase that acts with several pattern recognition receptors to activate defense signaling. A second AvrPtoB domain binds and suppresses the PTI-associated kinase Bti9 but is conversely recognized by the protein kinase Pto to activate effector-triggered immunity. We report the crystal structure of the AvrPtoB-BAK1 complex, which revealed structural similarity between these two AvrPtoB domains, suggesting that they arose by intragenic duplication. The BAK1 kinase domain is structurally similar to Pto, and a conserved region within both BAK1 and Pto interacts with AvrPtoB. BAK1 kinase activity is inhibited by AvrPtoB, and mutations at the interaction interface disrupt AvrPtoB virulence activity. These results shed light on a structural mechanism underlying host-pathogen coevolution. PMID:22169508

  20. AvrRxo1 Is a Bifunctional Type III Secreted Effector and Toxin-Antitoxin System Component with Homologs in Diverse Environmental Contexts.

    Science.gov (United States)

    Triplett, Lindsay R; Shidore, Teja; Long, John; Miao, Jiamin; Wu, Shuchi; Han, Qian; Zhou, Changhe; Ishihara, Hiromichi; Li, Jianyong; Zhao, Bingyu; Leach, Jan E

    2016-01-01

    Toxin-antitoxin (TA) systems are ubiquitous bacterial systems that may function in genome maintenance and metabolic stress management, but are also thought to play a role in virulence by helping pathogens survive stress. We previously demonstrated that the Xanthomonas oryzae pv. oryzicola protein AvrRxo1 is a type III-secreted virulence factor that has structural similarities to the zeta family of TA toxins, and is toxic to plants and bacteria in the absence of its predicted chaperone Arc1. In this work, we confirm that AvrRxo1 and its binding partner Arc1 function as a TA system when expressed in Escherichia coli. Sequences of avrRxo1 homologs were culled from published and newly generated phytopathogen genomes, revealing that avrRxo1:arc1 modules are rare or frequently inactivated in some species and highly conserved in others. Cloning and functional analysis of avrRxo1 from Acidovorax avenae, A. citrulli, Burkholderia andropogonis, Xanthomonas translucens, and Xanthomonas euvesicatoria showed that some AvrRxo1 homologs share the bacteriostatic and Rxo1-mediated cell death triggering activities of AvrRxo1 from X. oryzae. Additional distant putative homologs of avrRxo1 and arc1 were identified in genomic or metagenomic sequence of environmental bacteria with no known pathogenic role. One of these distant homologs was cloned from the filamentous soil bacterium Cystobacter fuscus. avrRxo1 from C. fuscus caused watersoaking and triggered Rxo1-dependent cell collapse in Nicotiana benthamiana, but no growth suppression in E. coli was observed. This work confirms that a type III effector can function as a TA system toxin, and illustrates the potential of microbiome data to reveal new environmental origins or reservoirs of pathogen virulence factors. PMID:27391081

  1. AvrRxo1 Is a Bifunctional Type III Secreted Effector and Toxin-Antitoxin System Component with Homologs in Diverse Environmental Contexts

    Science.gov (United States)

    Triplett, Lindsay R.; Shidore, Teja; Long, John; Miao, Jiamin; Wu, Shuchi; Han, Qian; Zhou, Changhe; Ishihara, Hiromichi; Li, Jianyong; Zhao, Bingyu; Leach, Jan E.

    2016-01-01

    Toxin-antitoxin (TA) systems are ubiquitous bacterial systems that may function in genome maintenance and metabolic stress management, but are also thought to play a role in virulence by helping pathogens survive stress. We previously demonstrated that the Xanthomonas oryzae pv. oryzicola protein AvrRxo1 is a type III-secreted virulence factor that has structural similarities to the zeta family of TA toxins, and is toxic to plants and bacteria in the absence of its predicted chaperone Arc1. In this work, we confirm that AvrRxo1 and its binding partner Arc1 function as a TA system when expressed in Escherichia coli. Sequences of avrRxo1 homologs were culled from published and newly generated phytopathogen genomes, revealing that avrRxo1:arc1 modules are rare or frequently inactivated in some species and highly conserved in others. Cloning and functional analysis of avrRxo1 from Acidovorax avenae, A. citrulli, Burkholderia andropogonis, Xanthomonas translucens, and Xanthomonas euvesicatoria showed that some AvrRxo1 homologs share the bacteriostatic and Rxo1-mediated cell death triggering activities of AvrRxo1 from X. oryzae. Additional distant putative homologs of avrRxo1 and arc1 were identified in genomic or metagenomic sequence of environmental bacteria with no known pathogenic role. One of these distant homologs was cloned from the filamentous soil bacterium Cystobacter fuscus. avrRxo1 from C. fuscus caused watersoaking and triggered Rxo1-dependent cell collapse in Nicotiana benthamiana, but no growth suppression in E. coli was observed. This work confirms that a type III effector can function as a TA system toxin, and illustrates the potential of microbiome data to reveal new environmental origins or reservoirs of pathogen virulence factors. PMID:27391081

  2. Sex-specific effects of NLRP6/AVR and ADM loci on susceptibility to essential hypertension in a Sardinian population.

    Directory of Open Access Journals (Sweden)

    Nicola Glorioso

    Full Text Available Coronary artery disease, heart failure, fatal arrhythmias, stroke, and renal disease are the most common causes of mortality for humans, and essential hypertension remains a major risk factor. Elucidation of susceptibility loci for essential hypertension has been difficult because of its complex, multifactorial nature involving genetic, environmental, and sex- and age-dependent nature. We investigated whether the 11p15.5 region syntenic to rat chromosome 1 region containing multiple blood pressure quantitative trait loci (QTL detected in Dahl rat intercrosses harbors polymorphisms that contribute to susceptibility/resistance to essential hypertension in a Sardinian population. Initial testing performed using microsatellite markers spanning 18 Mb of 11p15.5 detected a strong association between D11S1318 (at 2.1 Mb, P = 0.004 and D11S1346 (at 10.6 Mb, P = 0.00000004, suggesting that loci in close proximity to these markers may contribute to susceptibility in our Sardinian cohort. NLR family, pyrin domain containing 6/angiotensin-vasopressin receptor (NLRP6/AVR, and adrenomedullin (ADM are in close proximity to D11S1318 and D11S1346, respectively; thus we tested single nucleotide polymorphisms (SNPs within NLRP6/AVR and ADM for their association with hypertension in our Sardinian cohort. Upon sex stratification, we detected one NLRP6/AVR SNP associated with decreased susceptibility to hypertension in males (rs7948797G, P = 0.029; OR = 0.73 [0.57-0.94]. For ADM, sex-specific analysis showed a significant association between rs4444073C, with increased susceptibility to essential hypertension only in the male population (P = 0.006; OR = 1.44 [1.13-1.84]. Our results revealed an association between NLRP6/AVR and ADM loci with male essential hypertension, suggesting the existence of sex-specific NLRP6/AVR and ADM variants affecting male susceptibility to essential hypertension.

  3. Pebble heater suppresses synthesis of dioxins and furans in off-gas generated by incineration of halogen-rich fuel from WEEE

    Energy Technology Data Exchange (ETDEWEB)

    Schlummer, M.; Gruber, L.; Maeurer, A.; Wolz, G. [Fraunhofer Institute for Process Engineering and Packaging IVV, Freising (Germany); Fischer, W.; Quicker, P. [ATZ-EVUS, Development Center for Process Engineering, Sulzbach-Rosenberg (Germany)

    2004-09-15

    Changes in German and European legislation have led to altered approaches for the disposal of polymer-rich shredding residues (SR). Whereas disposal in landfills was the strategy of choice in the last decades, thermal treatment is supported now. However, when waste electric and electronic equipment (WEEE) is the source of SR, thermal treatment is complicated by a bromine and chlorine load in the lower percent range the presence of polybrominated dioxins and furans (PBDD/F) in the ppb range and by brominated flame retardants including polybrominated biphenyl ethers, which serve as dioxin precursors. Here we present data of a pilot application of the pebble heater technology for the treatment of raw gas derived from the incineration of polymeric materials from WEEE. Since the pilot experiments were performed on an existing pebble heater test plant in the small-technical scale, waste throughput and experimental design had to be adjusted to the given circumstances. As the study focussed on exhaust treatment and not on the incineration process itself, a liquid fuel was applied as a model for SR from WEEE. The incineration of a liquid fuel was preferred, since it could be implemented in the given test plant by spray injection, thus minimising technical modifications of the test plant and optimising the combustion efficiency compared to incineration of solid polymer granulates. Fuel and exhaust gases, which passed the pebble heater bed, were sampled and analysed for PCDD/F and PBDD/F. The pilot incineration was tested for the compliance with the PCDD/F emission limits given by European directive 2000/76/EC, and overall mass balances were calculated for PCDD/F and PBDD/F.

  4. A chemical screen for suppressors of the avrRpm1-RPM1-dependent hypersensitive cell death response in Arabidopsis thaliana

    OpenAIRE

    Serrano, M; Hubert, D.; Dangl, J.; Schulze-Lefert, P; Kombrink, E.

    2010-01-01

    Arabidopsis thaliana RPM1 encodes an intracellular immune sensor that conditions disease resistance to Pseudomonas syringae expressing the type III effector protein AvrRpm1. Conditional expression of this type III effector in a transgenic line carrying avrRpm1 under the control of a steroid-inducible promoter results in RPM1-dependent cell death that resembles the cell death response of the incompatible RPM1-avrRpm1 plant–bacterium interaction. This line was previously used in a genetic scree...

  5. Characteristics of microstructure and tritium release properties of different kinds of beryllium pebbles for application in tritium breeding modules

    Energy Technology Data Exchange (ETDEWEB)

    Kurinskiy, P.; Vladimirov, P.; Moeslang, A. [Karlsruhe Institute of Technology (KIT), Karlsruhe (Germany). Inst. for Applied Materials - Applied Materials Physics (IAM-AWP); Rolli, R. [Karlsruhe Institute of Technology (KIT), Karlsruhe (Germany). Inst. for Applied Materials - Materials Biomechanics (IAM-WBM); Zmitko, M. [The European Joint Undertaking for ITER and the Development of Fusion Energy, Barcelona (Spain)

    2013-07-01

    Beryllium pebbles with diameters of 1 mm are considered to be perspective material for the use as neutron multiplier in tritium breeding modules of fusion reactors. Up to now, the main concept of helium-cooled breeding blanket in ITER project foresees the use of 1 mm beryllium pebbles fabricated by company NGK, Japan. It is notable that beryllium pebbles of other types are commercially available at the market. Presented work is dedicated to a study of characteristics of microstructure, packaging density and parameters of tritium release of beryllium pebbles produced by Bochvar Institute, Russian Federation, and Company Materion, USA. (orig.).

  6. Penn State geoPebble system: Design,Implementation, and Initial Results

    Science.gov (United States)

    Urbina, J. V.; Anandakrishnan, S.; Bilen, S. G.; Fleishman, A.; Burkett, P.

    2014-12-01

    The Penn State geoPebble system is a new network of wirelessly interconnected seismic and GPS sensor nodes with flexible architecture. This network will be used for studies of ice sheets in Antarctica and Greenland, as well as to investigate mountain glaciers. The network will consist of ˜150 geoPebbles that can be deployed in a user-defined spatial geometry. We present our design methodology, which has enabled us to develop these state-of- the art sensors using commercial-off-the-shelf hardware combined with custom-designed hardware and software. Each geoPebble is a self- contained, wirelessly connected sensor for collecting seismic measurements and position information. Key elements of each node encompasses a three-component seismic recorder, which includes an amplifier, filter, and 24- bit analog-to-digital converter that can sample up to 10 kHz. Each unit also includes a microphone channel to record the ground-coupled airwave. The timing for each node is available from GPS measurements and a local precision oscillator that is conditioned by the GPS timing pulses. In addition, we record the carrier-phase measurement of the L1 GPS signal in order to determine location at sub-decimeter accuracy (relative to other geoPebbles within a few kilometers radius). Each geoPebble includes 16 GB of solid-state storage, wireless communications capability to a central supervisory unit, and auxiliary measurements capability (including tilt from accelerometers, absolute orientation from magnetometers and temperature). A novel aspect of the geoPebble is a wireless charging system for the internal battery (using inductive coupling techniques). The geoPebbles include all the sensors (geophones, GPS, microphone), communications (WiFi), and power (battery and charging) internally, so the geoPebble system can operate without any cabling connections (though we do provide an external connector so that different geophones can be used). We report initial field-deployment results and

  7. Comet 67P/Churyumov-Gerasimenko preserved the pebbles that formed planetesimals

    Science.gov (United States)

    Fulle, Marco; Della Corte, V.; Rotundi, A.; Rietmeijer, F. J. M.; Green, S. F.; Weissman, P.; Accolla, M.; Colangeli, L.; Ferrari, M.; Ivanovski, S.; Lopez-Moreno, J. J.; Epifani, E. Mazzotta; Morales, R.; Ortiz, J. L.; Palomba, E.; Palumbo, P.; Rodriguez, J.; Sordini, R.; Zakharov, V.

    2016-09-01

    Solar System formation models predict that the building-blocks of planetesimals were mm- to cm-sized pebbles, aggregates of ices and non-volatile materials, consistent with the compact particles ejected by comet 67P/Churyumov-Gerasimenko (67P hereafter) and detected by GIADA (Grain Impact Analyzer and Dust Accumulator) on-board the Rosetta spacecraft. Planetesimals were formed by the gentle gravitational accretion of pebbles, so that they have an internal macroporosity of 40%. We measure the average dust bulk density ρ _D = 795_{-65}^{+840} kg m-3 that, coupled to the 67P nucleus bulk density, provides the average dust-to-ices mass ratio δ = 8.5. We find that the measured densities of the 67P pebbles are consistent with a mixture of (15 ± 6)% of ices, (5 ± 2)% of Fe-sulfides, (28 ± 5)% of silicates, and (52 ± 12)% of hydrocarbons, in average volume abundances. This composition matches both the solar and CI-chondritic chemical abundances, thus showing that GIADA has sampled the typical non-volatile composition of the pebbles that formed all planetesimals. The GIADA data do not constrain the abundance of amorphous silicates vs. crystalline Mg,Fe-olivines and pyroxenes. We find that the pebbles have a microporosity of (52 ± 8)% (internal volume filling factor φP = 0.48 ± 0.08), implying an average porosity for the 67P nucleus of (71 ± 8)%, lower than previously estimated.

  8. Formation of dust-rich planetesimals from sublimated pebbles inside of the snow line

    CERN Document Server

    Ida, Shigeru

    2016-01-01

    Content: For up to a few millions of years, pebbles must provide a quasi-steady inflow of solids from the outer parts of protoplanetary disks to their inner regions. Aims: We want to understand how a significant fraction of the pebbles grow into planetesimals rather than being lost to the host star. Methods: We examine analytically how the inward flow of pebbles is affected by the presence of a snow line and under which conditions dust-rich (rocky) planetesimals form. When calculating the inward drift of solids due to gas drag, we include the back-reaction of the gas to the motion of the solids. Results: We show that in low-viscosity protoplanetary disks (with a monotonous surface density similar to that of the minimum-mass solar nebula), the flow of pebbles does not usually reach the required surface density to form planetesimals by streaming instability. We show however that if the pebble-to-gas mass flux exceeds a critical value, no steady solution can be found for the solid-to-gas ratio. Conclusions: This...

  9. On the water delivery to terrestrial embryos by ice pebble accretion

    CERN Document Server

    Sato, Takao; Ida, Shigeru

    2015-01-01

    Standard accretion disk models suggest that the snow line in the solar nebula migrated interior to the Earth's orbit in a late stage of nebula evolution. In this late stage, a significant amount of ice could have been delivered to 1 AU from outer regions in the form of mm to dm-sized "pebbles." This raises the question why the present Earth is so depleted of water (with the ocean mass being as small as 0.023% of the Earth mass). Here we quantify the amount of icy pebbles accreted by terrestrial embryos after the migration of the snow line assuming that no mechanism halts the pebble flow in outer disk regions. We use a simplified version of the coagulation equation to calculate the formation and radial inward drift of icy pebbles in a protoplanetary disk. The pebble accretion cross section of an embryo is calculated using analytic expressions presented by recent studies. We find that the final mass and water content of terrestrial embryos strongly depends on the radial extent of the gas disk, the strength of d...

  10. Study of the fracture behavior of mortar and concretes with crushed rock or pebble aggregates

    Directory of Open Access Journals (Sweden)

    Sebastião Ribeiro

    2011-03-01

    Full Text Available The objective of this work was to compare the fracture energy of mortar and concretes produced with crushed rock and pebble aggregates using zero, 10, 20, 30 and 40% of aggregates mixed with standard mortar and applying the wedge splitting method to achieve stable crack propagation. The samples were cast in a special mold and cured for 28 days, after which they were subjected to crack propagation tests by the wedge splitting method to determine the fracture energies of the mortar and concrete. The concretes showed higher fracture energy than the mortar, and the concretes containing crushed rock showed higher resistance to crack propagation than all the compositions containing pebbles. The fracture energy varied from 38 to 55 J.m-2. A comparison of the number of aggregates that separated from the two concrete matrices with the highest fracture energies indicated that the concrete containing pebbles crumbled more easily and was therefore less resistant to crack propagation.

  11. The growth of planets by pebble accretion in evolving protoplanetary discs

    CERN Document Server

    Bitsch, Bertram; Johansen, Anders

    2015-01-01

    The formation of planets depends on the underlying protoplanetary disc structure, which influences both the accretion and migration rates of embedded planets. The disc itself evolves on time-scales of several Myr during which both temperature and density profiles change as matter accretes onto the central star. Here we use a detailed model of an evolving disc to determine the growth of planets by pebble accretion and their migration through the disc. Cores that reach their pebble isolation mass accrete gas to finally form giant planets with extensive gas envelopes, while planets that do not reach pebble isolation mass are stranded as ice giants and ice planets containing only minor amounts of gas in their envelopes. Unlike earlier population synthesis models, our model works without any artificial reductions in migration speed and for protoplanetary discs with gas and dust column densities similar to those inferred from observations. We find that in our nominal disc model the emergence of planetary embryos pr...

  12. Statistical investigations of the failure behaviour of components in the AVR experimental nuclear power plant. Vol. 2

    International Nuclear Information System (INIS)

    From operational records of the years 1977 to 1986, service life distributions of helium valves in gas circuits of the AVR were determined. Results are constant failure rates in the range from 3 to 6x10-6/h and, for some populations, indications of time dependent failure rates. Nonparametric methods showed only limited efficiency. For a Bayesian approach the necessary prior information was missing. Furthermore, the main failure causes could be determined. (orig./HP)

  13. Challenges in forming the solar system's giant planet cores via pebble accretion

    Energy Technology Data Exchange (ETDEWEB)

    Kretke, K. A.; Levison, H. F., E-mail: kretke@boulder.swri.edu [Southwest Research Institute, 1050 Walnut Street, Suite 300, Boulder, CO 80302 (United States)

    2014-12-01

    Though ∼10 M {sub ⊕} mass rocky/icy cores are commonly held as a prerequisite for the formation of gas giants, theoretical models still struggle to explain how these embryos can form within the lifetimes of gaseous circumstellar disks. In recent years, aerodynamic-aided accretion of 'pebbles', objects ranging from centimeters to meters in size, has been suggested as a potential solution to this long-standing problem. While pebble accretion has been demonstrated to be extremely effective in local simulations that look at the detailed behavior of these pebbles in the vicinity of a single planetary embryo, to date there have been no global simulations demonstrating the effectiveness of pebble accretion in a more complicated, multi-planet environment. Therefore, we have incorporated the aerodynamic-aided accretion physics into LIPAD, a Lagrangian code that can follow the collisional/accretional/dynamical evolution of a protoplanetary system, to investigate how pebble accretion manifests itself in the larger planet formation picture. We find that under generic circumstances, pebble accretion naturally leads to an 'oligarchic' type of growth in which a large number of planetesimals grow to similar-sized planets. In particular, our simulations tend to form hundreds of Mars- and Earth-mass objects between 4 and 10 AU. While merging of some oligarchs may grow massive enough to form giant planet cores, leftover oligarchs lead to planetary systems that cannot be consistent with our own solar system. We investigate various ideas presented in the literature (including evaporation fronts and planet traps) and find that none easily overcome this tendency toward oligarchic growth.

  14. Challenges in forming the solar system's giant planet cores via pebble accretion

    International Nuclear Information System (INIS)

    Though ∼10 M ⊕ mass rocky/icy cores are commonly held as a prerequisite for the formation of gas giants, theoretical models still struggle to explain how these embryos can form within the lifetimes of gaseous circumstellar disks. In recent years, aerodynamic-aided accretion of 'pebbles', objects ranging from centimeters to meters in size, has been suggested as a potential solution to this long-standing problem. While pebble accretion has been demonstrated to be extremely effective in local simulations that look at the detailed behavior of these pebbles in the vicinity of a single planetary embryo, to date there have been no global simulations demonstrating the effectiveness of pebble accretion in a more complicated, multi-planet environment. Therefore, we have incorporated the aerodynamic-aided accretion physics into LIPAD, a Lagrangian code that can follow the collisional/accretional/dynamical evolution of a protoplanetary system, to investigate how pebble accretion manifests itself in the larger planet formation picture. We find that under generic circumstances, pebble accretion naturally leads to an 'oligarchic' type of growth in which a large number of planetesimals grow to similar-sized planets. In particular, our simulations tend to form hundreds of Mars- and Earth-mass objects between 4 and 10 AU. While merging of some oligarchs may grow massive enough to form giant planet cores, leftover oligarchs lead to planetary systems that cannot be consistent with our own solar system. We investigate various ideas presented in the literature (including evaporation fronts and planet traps) and find that none easily overcome this tendency toward oligarchic growth.

  15. Characteristics of microstructure and tritium release properties of different kinds of beryllium pebbles for application in tritium breeding modules

    Energy Technology Data Exchange (ETDEWEB)

    Kurinskiy, P., E-mail: petr.kurinskiy@kit.edu [Karlsruhe Institute of Technology, Institute for Applied Materials – Applied Materials Physics (IAM-AWP), P.O. Box 3640, Karlsruhe 76021 (Germany); Vladimirov, P.; Moeslang, A. [Karlsruhe Institute of Technology, Institute for Applied Materials – Applied Materials Physics (IAM-AWP), P.O. Box 3640, Karlsruhe 76021 (Germany); Rolli, R. [Karlsruhe Institute of Technology, Institute for Applied Materials – Materials and Biomechanics (IAM-WBM), P.O. Box 3640, Karlsruhe 76021 (Germany); Zmitko, M. [The European Joint Undertaking for ITER and the Development of Fusion Energy, c/Josep Pla, no. 2, Torres Diagonal Litoral, Edificio B3, Barcelona 08019 (Spain)

    2014-10-15

    Highlights: • Tritium release properties and characteristics of microstructure of beryllium pebbles having different sizes of grains were studied. • Fine-grained beryllium pebbles showed the best ability to release tritium compared to pebbles from another charges. • Be pebbles with the grain sizes exceeding 100 μm contain a great number of small pores and inclusions presumably referring to the history of material fabrication. • The sizes of grains are one of a key characteristic of microstructure which influences the parameters of tritium release. - Abstract: Beryllium pebbles with diameters of 1 mm are considered to be perspective material for the use as neutron multiplier in tritium breeding modules of fusion reactors. Up to now, the design of helium-cooled breeding blanket in ITER project foresees the use of 1 mm beryllium pebbles fabricated by NGK Insulators Ltd., Japan. It is notable that beryllium pebbles from Russian Federation and USA are also available and the possibility of their large-scale fabrication is under study. Presented work is dedicated to a study of characteristics of microstructure and parameters of tritium release of beryllium pebbles produced by Bochvar Institute, Russian Federation, and Materion Corporation, USA.

  16. Apply Burnable Poison For Fuel Pebble Of PBMR-400 With OTTO Refueling

    International Nuclear Information System (INIS)

    A new fuel pebble was designed by adding spherical Gd2O3 particles for obtaining the minimum reactivity swing. Optimization is done in a lattice model to determine the combination of radius and number of burnable poison (BP) particles per pebble to obtain the minimum reactivity swing. The numerical calculation so that with 740 μm and 13 particles of Gd2O3. The reactivity swing is reduced from 38% to 2.0%, whereas the k∞ is 1.06 - 1.08 for a fuel lattice with the target burnup of 55 GWd/t. (author)

  17. Catalyst functionalized buffer sorbent pebbles for rapid separation of carbon dioxide from gas mixtures

    Energy Technology Data Exchange (ETDEWEB)

    Aines, Roger D

    2015-03-31

    A method for separating CO.sub.2 from gas mixtures uses a slurried media impregnated with buffer compounds and coating the solid media with a catalyst or enzyme that promotes the transformation of CO.sub.2 to carbonic acid. Buffer sorbent pebbles with a catalyst or enzyme coating are provided for rapid separation of CO.sub.2 from gas mixtures.

  18. Growing the gas-giant planets by the gradual accumulation of pebbles

    CERN Document Server

    Levison, Harold F; Duncan, Martin J

    2015-01-01

    It is widely held that the first step in forming the gas giant planets, such as Jupiter and Saturn, is to form solid `cores' of roughly 10 M$_\\oplus$. Getting the cores to form before the solar nebula dissipates ($\\sim\\!1-10\\,$Myr) has been a major challenge for planet formation models. Recently models have emerged in which `pebbles' (centimeter- to meter-size objects) are first concentrated by aerodynamic drag and then gravitationally collapse to form 100 --- 1000 km objects. These `planetesimals' can then efficiently accrete leftover pebbles and directly form the cores of giant planets. This model known as `pebble accretion', theoretically, can produce 10 M$_\\oplus$ cores in only a few thousand years. Unfortunately, full simulations of this process show that, rather than creating a few 10 M$_\\oplus$ cores, it produces a population of hundreds of Earth-mass objects that are inconsistent with the structure of the Solar System. Here we report that this difficulty can be overcome if pebbles form slowly enough t...

  19. Catalyst functionalized buffer sorbent pebbles for rapid separation of carbon dioxide from gas mixtures

    Science.gov (United States)

    Aines, Roger D.

    2013-03-12

    A method for separating CO.sub.2 from gas mixtures uses a slurried media impregnated with buffer compounds and coating the solid media with a catalyst or enzyme that promotes the transformation of CO.sub.2 to carbonic acid. Buffer sorbent pebbles with a catalyst or enzyme coating are provided for rapid separation of CO.sub.2 from gas mixtures.

  20. Thermal ramp tritium release in COBRA-1A2 C03 beryllium pebbles

    Energy Technology Data Exchange (ETDEWEB)

    Baldwin, D.L. [Pacific Northwest National Lab., Richland, WA (United States)

    1998-03-01

    Tritium release kinetics, using the method of thermal ramp heating at three linear ramp rates, were measured on the COBRA-1A2 C03 1-mm beryllium pebbles. This report includes a brief discussion of the test, and the test data in graph format.

  1. Separating gas-giant and ice-giant planets by halting pebble accretion

    CERN Document Server

    Lambrechts, Michiel; Morbidelli, Alessandro

    2014-01-01

    In the Solar System giant planets come in two flavours: 'gas giants' (Jupiter and Saturn) with massive gas envelopes and 'ice giants' (Uranus and Neptune) with much thinner envelopes around their cores. It is poorly understood how these two classes of planets formed. High solid accretion rates, necessary to form the cores of giant planets within the life-time of protoplanetary discs, heat the envelope and prevent rapid gas contraction onto the core, unless accretion is halted. We find that, in fact, accretion of pebbles (~ cm-sized particles) is self-limiting: when a core becomes massive enough it carves a gap in the pebble disc. This halt in pebble accretion subsequently triggers the rapid collapse of the super-critical gas envelope. As opposed to gas giants, ice giants do not reach this threshold mass and can only bind low-mass envelopes that are highly enriched by water vapour from sublimated icy pebbles. This offers an explanation for the compositional difference between gas giants and ice giants in the S...

  2. Mikrokontroléry Atmel AVR, použití HW vývojového kitu STK 500 a vývojového prostředí AVR Studio a programovacího jazyka Bascom

    OpenAIRE

    VOLF, Jiří

    2009-01-01

    Goal of this work is a description of 8-bit microprocessors of AVR series with RISC architecture, instruction set and programming environment, Bascom and AVR Studio. Furthermore, this work deals with communications with the microcontroller environment, focusing on a specific type ATmega32. The work is divided into four parts. The first section deal with the general history and development of programmable logic circuits. The second part is attended to the micro{$\

  3. Pto kinase binds two domains of AvrPtoB and its proximity to the effector E3 ligase determines if it evades degradation and activates plant immunity.

    Directory of Open Access Journals (Sweden)

    Johannes Mathieu

    2014-07-01

    Full Text Available The tomato--Pseudomonas syringae pv. tomato (Pst--pathosystem is one of the best understood models for plant-pathogen interactions. Certain wild relatives of tomato express two closely related members of the same kinase family, Pto and Fen, which recognize the Pst virulence protein AvrPtoB and activate effector-triggered immunity (ETI. AvrPtoB, however, contains an E3 ubiquitin ligase domain in its carboxyl terminus which causes degradation of Fen and undermines its ability to activate ETI. In contrast, Pto evades AvrPtoB-mediated degradation and triggers ETI in response to the effector. It has been reported recently that Pto has higher kinase activity than Fen and that this difference allows Pto to inactivate the E3 ligase through phosphorylation of threonine-450 (T450 in AvrPtoB. Here we show that, in contrast to Fen which can only interact with a single domain proximal to the E3 ligase of AvrPtoB, Pto binds two distinct domains of the effector, the same site as Fen and another N-terminal domain. In the absence of E3 ligase activity Pto binds to either domain of AvrPtoB to activate ETI. However, the presence of an active E3 ligase domain causes ubiquitination of Pto that interacts with the domain proximal to the E3 ligase, identical to ubiquitination of Fen. Only when Pto binds its unique distal domain can it resist AvrPtoB-mediated degradation and activate ETI. We show that phosphorylation of T450 is not required for Pto-mediated resistance in vivo and that a kinase-inactive version of Pto is still capable of activating ETI in response to AvrPtoB. Our results demonstrate that the ability of Pto to interact with a second site distal to the E3 ligase domain in AvrPtoB, and not a higher kinase activity or T450 phosphorylation, allows Pto to evade ubiquitination and to confer immunity to Pst.

  4. The growth of planets by pebble accretion in evolving protoplanetary discs

    Science.gov (United States)

    Bitsch, Bertram; Lambrechts, Michiel; Johansen, Anders

    2015-10-01

    The formation of planets depends on the underlying protoplanetary disc structure, which in turn influences both the accretion and migration rates of embedded planets. The disc itself evolves on time scales of several Myr, during which both temperature and density profiles change as matter accretes onto the central star. Here we used a detailed model of an evolving disc to determine the growth of planets by pebble accretion and their migration through the disc. Cores that reach their pebble isolation mass accrete gas to finally form giant planets with extensive gas envelopes, while planets that do not reach pebble isolation mass are stranded as ice giants and ice planets containing only minor amounts of gas in their envelopes. Unlike earlier population synthesis models, our model works without any artificial reductions in migration speed and for protoplanetary discs with gas and dust column densities similar to those inferred from observations. We find that in our nominal disc model, the emergence of planetary embryos preferably should occur after approximately 2 Myr in order to not exclusively form gas giants, but also ice giants and smaller planets. The high pebble accretion rates ensure that critical core masses for gas accretion can be reached at all orbital distances. Gas giant planets nevertheless experience significant reduction in semi-major axes by migration. Considering instead planetesimal accretion for planetary growth, we show that formation time scales are too long to compete with the migration time scales and the dissipation time of the protoplanetary disc. All in all, we find that pebble accretion overcomes many of the challenges in the formation of ice and gas giants in evolving protoplanetary discs. Appendices are available in electronic form at http://www.aanda.org

  5. Serial communication between AVR single chip and PC under environment of Delphi%Delphi环境下实现与AVR单片机的串行通信

    Institute of Scientific and Technical Information of China (English)

    李凯; 左文香; 夏国明; 郭玉霞; 张铁壁

    2012-01-01

    With the data acquisition and control system of material testing machine as example, a hardware actualization method of serial communication between PC and AVR single chip processor was introduced. The using method and software programming of TComm component under environment of Delphi were detailedly described. And serial communication programming methods for ATmegal6 single chip microcomputer under environment of AVR Studio+AVR GCC was emphatically discussed. Physically application indicates that this scheme got powerful stability and credibility and has superior engineering value.%以材料试验机数据采集及控制系统为实例,介绍了PC机与AVR单片机串行通信的硬件实现方法.详细说明了在Delphi环境下,TComm串行通信组件的使用和软件编程方法.阐述了在AVR Studio+AVR GCC编程环境下,ATmega16单片机串口通信的软件编程.实际应用表明,该方案稳定、可靠、易于实现,具有很好的工程实用价值.

  6. Control System for Fruits and Vegetables Fresh-keeping Cabinet Based on AVR%基于 AVR 的果蔬保鲜陈列柜控制系统

    Institute of Scientific and Technical Information of China (English)

    岑康华; 王海林; 吕恩利; 傅涛; 唐本源

    2015-01-01

    Taking open type fruit and vegetable fresh-keeping display cabinet as design platform , a kind of control sys-tem regarded AVR series of ATmega 16 microprocessor as the core was developed , it based on ICCV7 for AVR software development platform and using C programming language .Through the acquisition of preservation parameters of tempera-ture and relative humidity , using the method of double limit to control cooling and humidifying equipment work , which a-chieve integrated control of temperature and relative humidity on the storage rack of fruits and vegetables fresh -keeping display cabinet .The experimental results showed that:the system could correctly collect the fresh-keeping parameters of fruits and vegetables in the fresh environment , and according to the result of logical judgment to control the work of asso-ciated actuator real-time and accurately , and the stability of control system is good .%以敞开式果蔬保鲜陈列柜为设计平台,开发了以 AVR 系列 ATmega 16微处理器为核心的控制系统。系统基于ICCV 7 for AVR 软件开发平台,使用C语言编程实现。通过采集保鲜环境温度和相对湿度保鲜参数,使用双限值控制方法,控制制冷、加湿等执行设备工作,实现对果蔬保鲜陈列柜货架区温度和相对湿度的综合调控。试验结果表明:该系统能准确地采集保鲜环境内各保鲜参数的变化,且能够根据逻辑判断结果实时、准确地控制相应执行机构工作,工作稳定性良好。

  7. Relationship of acute left main coronary artery occlusion and ST-segmentelevation in lead aVR

    Institute of Scientific and Technical Information of China (English)

    于富军; 傅向华; 卫亚丽; 李寿霖; 肖蕴陟; 丁超; 赵战勇

    2004-01-01

    @@It is well known that acute left main coronary artery (LMCA) occlusion is one of the most severe lesions associated with coronary artery disease. A large number of LMCA patients die suddenly at the very beginning of a heart attack. Noninvasive identification of acute LMCA occlusion is very important for patient prognosis and survival, especially to predict the need of the invasive procedure of coronary artery reconstruction. In this study, we sought to evaluate retrospectively the value of ST-segment elevation in lead aVR in predicting acute myocardial infarction (AMI) and acute LMCA obstruction.

  8. Intramolecular interaction influences binding of the Flax L5 and L6 resistance proteins to their AvrL567 ligands.

    Directory of Open Access Journals (Sweden)

    Michael Ravensdale

    Full Text Available L locus resistance (R proteins are nucleotide binding (NB-ARC leucine-rich repeat (LRR proteins from flax (Linum usitatissimum that provide race-specific resistance to the causal agent of flax rust disease, Melampsora lini. L5 and L6 are two alleles of the L locus that directly recognize variants of the fungal effector AvrL567. In this study, we have investigated the molecular details of this recognition by site-directed mutagenesis of AvrL567 and construction of chimeric L proteins. Single, double and triple mutations of polymorphic residues in a variety of AvrL567 variants showed additive effects on recognition strength, suggesting that multiple contact points are involved in recognition. Domain-swap experiments between L5 and L6 show that specificity differences are determined by their corresponding LRR regions. Most positively selected amino acid sites occur in the N- and C-terminal LRR units, and polymorphisms in the first seven and last four LRR units contribute to recognition specificity of L5 and L6 respectively. This further confirms that multiple, additive contact points occur between AvrL567 variants and either L5 or L6. However, we also observed that recognition of AvrL567 is affected by co-operative polymorphisms between both adjacent and distant domains of the R protein, including the TIR, ARC and LRR domains, implying that these residues are involved in intramolecular interactions to optimize detection of the pathogen and defense signal activation. We suggest a model where Avr ligand interaction directly competes with intramolecular interactions to cause activation of the R protein.

  9. Genetic and physical mapping of AvrPi7, a novel avirulence gene of Magnaporthe oryzae using physical position-ready markers

    Institute of Scientific and Technical Information of China (English)

    FENG ShuJie; WANG Ling; MA JunHong; LIN Fei; PAN QingHua

    2007-01-01

    Rice blast, caused by the fungal pathogen Magnaporthe oryzae, is one of the most devastating crop diseases worldwide. The avirulence gene corresponding to rice blast resistance gene Pi7 in field isolate CHL346 was inherited as a single gene, designated AvrPi7, in a segregating population consisting of 189 ascospore progenies derived from a cross between field isolates CHL346 and CHL42. In order to determine the chromosomal location of the AvrPi7 locus, a total of 121 simple sequence repeat (SSR) markers were developed based on the whole-genome sequence of reference isolate 70-15 of M. oryzae.Linkage analysis of the locus with these SSR markers showed that eight SSR markers on chromosome1 were linked to the locus, among which the closest flanking markers MS1-9 and MS1-15 were 3.2 and 16.4 cM from the locus, respectively. For fine mapping, additional PCR-based makers including eight SSR markers and three candidate avirulence gene (CAG) markers were developed in the region flanking both markers. The AvrPi7 locus was genetically delimited within a 1.6-cM region flanked by markers MS1-21 and MS1-22, and co-segregated with the marker CAG2. To construct a physical map of the AvrPi7 locus, molecular markers linked to the Avr gene were mapped on the supercontigs of the reference isolate 70-15 through bioinformation analysis (BIA). Consequently, the AvrPi7 locus was delimited to a 75-kb interval flanked by markers MS1-21 and MS1-22 based on the reference sequence.Merodiploids observed in this study are also discussed.

  10. Design and Realization of Micromouse Software Based on AVR ATmega128%基于AVR ATmega128的迷宫电脑鼠软件设计与实现

    Institute of Scientific and Technical Information of China (English)

    李龙; 林桂泉

    2014-01-01

    根据IEEE标准电脑鼠走迷宫的比赛需求,介绍了一个基于AVR ATmega128的电脑鼠软件算法的设计与实现,主要包括底层驱动算法和顶层软件算法两个部分。该电脑鼠实现了在迷宫内快速稳定的行走及对迷宫最优路径的搜索。电脑鼠迷宫竞赛有一定的难度,这是一种具有挑战性和趣味性的竞技比赛。Micromouse是一个涉及多个学科领域的理论与应用的综合性系统。%According to the IEEE standard computer mouse maze game needs, introduces the design and implementation of a computer mouse AVR ATmega128-based software algorithms, including algorithms underlying drivers and top software algo-rithms in two parts. The computer mouse to achieve a rapid and stable within walking labyrinth and maze searching for the opti-mal path. Computer mouse maze race with some difficulty, this is a challenging and interesting contests. Micromouse is a multi-disciplinary field involving theory and application of the integrated system.

  11. A Preliminary MCNP Solution to the IAEA CRP-5 Pebble Box Benchmark Problem

    Energy Technology Data Exchange (ETDEWEB)

    Qian, Hong; Lee, Hyun Chul; Kim, Kang Seog; Noh, Jae Man [Korea Atomic Energy Research Institute, Taejon (Korea, Republic of)

    2006-07-01

    Recently, the IAEA CRP-5 Pebble Box benchmark problem was proposed for a code-to-code comparison. To investigate the effect of the core/reflector spectral interaction and the effect of heterogeneity, the problem defines four cases(extended to six cases later) depending on the presence of reflector and the level of heterogeneity. The core in the problem consists of a box with dimensions of 1m x 1m x 1m. For some cases, there is a graphite reflector with a thickness of 1m around the core and the resultant dimension of the problem becomes 3m x 3m x 3m in those cases. In this paper, we present two geometry models for the IAEA CRP-5 Pebble Box benchmark problem and a preliminary MCNP2 solution to the problem with the two models.

  12. The role of pebble fragmentation in planetesimal formation I. Experimental study

    CERN Document Server

    Syed, M Bukhari; Jansson, K Wahlberg; Johansen, A

    2016-01-01

    Previous work on protoplanetary dust growth shows halt at centimeter sizes owing to the occurrence of bouncing at velocities of $\\geq$ 0.1 $ms^{-1}$ and fragmentation at velocities $\\geq$ 1 $ms^{-1}$. To overcome these barriers, spatial concentration of cm-sized dust pebbles and subsequent gravitational collapse have been proposed. However, numerical investigations have shown that dust aggregates may undergo fragmentation during the gravitational collapse phase. This fragmentation in turn changes the size distribution of the solids and thus must be taken into account in order to understand the properties of the planetesimals that form. To explore the fate of dust pebbles undergoing fragmenting collisions, we conducted laboratory experiments on dust-aggregate collisions with a focus on establishing a collision model for this stage of planetesimal formation. In our experiments, we analysed collisions of dust aggregates with masses between 1.4 g and 180 g, mass ratios between target and projectile from 125 to 1 ...

  13. Studies on crude oil removal from pebbles by the application of biodiesel.

    Science.gov (United States)

    Xia, Wen-xiang; Xia, Yan; Li, Jin-cheng; Zhang, Dan-feng; Zhou, Qing; Wang, Xin-ping

    2015-02-15

    Oil residues along shorelines are hard to remove after an oil spill. The effect of biodiesel to eliminate crude oil from pebbles alone and in combination with petroleum degrading bacteria was investigated in simulated systems. Adding biodiesel made oil detach from pebbles and formed oil-biodiesel mixtures, most of which remained on top of seawater. The total petroleum hydrocarbon (TPH) removal efficiency increased with biodiesel quantities but the magnitude of augment decreased gradually. When used with petroleum degrading bacteria, the addition of biodiesel (BD), nutrients (NUT) and BD+NUT increased the dehydrogenase activity and decreased the biodegradation half lives. When BD and NUT were replenished at the same time, the TPH removal efficiency was 7.4% higher compared to the total improvement of efficiency when BD and NUT was added separately, indicating an additive effect of biodiesel and nutrients on oil biodegradation.

  14. Thermo-mechanical and neutron lifetime modeling and design of Be pebbles in the neutron multiplier for the LIFE engine

    Energy Technology Data Exchange (ETDEWEB)

    DeMange, P; Marian, J; de Caro, M S; Caro, A

    2009-03-16

    Concept designs for the laser-initiated fusion/fission engine (LIFE) include a neutron multiplication blanket containing Be pebbles flowing in a molten salt coolant. These pebbles must be designed to withstand the extreme irradiation and temperature conditions in the blanket to enable a safe and cost-effective operation of LIFE. In this work, we develop design criteria for spherical Be pebbles on the basis of their thermomechanical behavior under continued neutron exposure. We consider the effects of high fluence/fast flux on the elastic, thermal and mechanical properties of nuclear-grade Be. Our results suggest a maximum pebble diameter of 30 mm to avoid tensile failure, coated with an anti-corrosive, high-strength metallic shell to avoid failure by pebble contact. Moreover, we find that the operation temperature must always be kept above 450 C to enable creep to relax the stresses induced by swelling, which we estimate to be at least 16 months if uncoated and up to six years when coated. We identify the sources of uncertainty on the properties used and discuss the advantages of new intermetallic beryllides and their use in LIFE's neutron multiplier. To establish Be-pebble lifetimes with improved confidence, reliable experiments to measure irradiation creep must be performed.

  15. The radial dependence of pebble accretion rates: a source of diversity in planetary systems I. Analytical formulation

    CERN Document Server

    Ida, Shigeru; Morbidelli, Alessandro

    2016-01-01

    Context. The classical "planetesimal" accretion scenario for the formation of planets has recently evolved with the idea that "pebbles", centimeter- to meter-sized icy grains migrating in protoplanetary disks, can control planetesimal and/or planetary growth. Aims. We investigate how pebble accretion depends on disk properties and affects the formation of planetary systems Methods. We construct analytical models of pebble accretion onto planetary embryos that consistently account for the mass and orbital evolution of the pebble flow and reflect disk structure. Results. We derive simple formulas for pebble accretion rates in the so-called "settling" regime for planetary embryos with more than 100 km in size. For relatively smaller embryos or in outer disk regions, the accretion mode is 3D, meaning that the thickness of the pebble flow must be taken into account, and resulting in an accretion rate that is independent of the embryo mass. For larger embryos or in inner regions, the accretion is in a 2D mode, i.e....

  16. Alexa Fluor 488 as an iron sensing molecule and its application in PEBBLE nanosensors.

    Science.gov (United States)

    Sumner, James P; Kopelman, Raoul

    2005-04-01

    Molecular Probes' Alexa Fluor dyes are generally used for biological labeling because of their ideal fluorescent properties, but here we detail Alexa Fluor 488's nanomolar sensitivity to free iron. Furthermore, the dye has been encapsulated into a polymer nanosphere by a microemulsion method, producing <100 nm particles. These nanosensors, PEBBLEs (Probe Encapsulated By Biologically Localized Embedding) have micromolar sensitivity and are non-responsive to other metal ions of biological interest.

  17. Design of Complex Systems to Achieve Passive Safety: Natural Circulation Cooling of Liquid Salt Pebble Bed Reactors

    OpenAIRE

    Scarlat, Raluca Olga

    2012-01-01

    This dissertation treats system design, modeling of transient system response, and characterization of individual phenomena and demonstrates a framework for integration of these three activities early in the design process of a complex engineered system. A system analysis framework for prioritization of experiments, modeling, and development of detailed design is proposed. Two fundamental topics in thermal-hydraulics are discussed, which illustrate the integration of modeling and experimentat...

  18. The pebble-bed high-temperature reactor as a source of nuclear process heat. Vol. 4

    International Nuclear Information System (INIS)

    In this volume the design conditions for a helium-heated steam reformer in the primary circuit of a high-temperature reactor are explained as far as today's knowledge allows. For the realization of helium-heated steam reformers, some fundamental questions at first occur regarding the heating temperature, heat fluxes, suitable materials and design solutions for steam reformers. It is shown that following the development program carried out until now, solutions to these questions can be seen. Moreover, details are given about the heat transfer, the mechanical design and the behaviour of reformer materials in helium with regard to H2- and T-permeation as well as corrosion. Furthermore, questions about the choice of the lay-out data, the design form, the arrangement in the helium circuits of the nuclear reactor and the necessary development steps are handled. Some design examples of heat exchangers for a 3,000 MW(th)-plant are given, too. (orig.)

  19. Thorium–based fuel cycles : saving uranium in a 200 MWth pebble bed high temperature reactor / S.K. Gintner

    OpenAIRE

    Gintner, Stephan Konrad

    2010-01-01

    The predominant nuclear fuel used globally at present is uranium which is a finite resource. Thorium has been identified as an alternative nuclear fuel source that can be utilized in almost all existing uranium–based reactors and can significantly help in conserving limited uranium reserves. Furthermore, the elimination of proliferation risks associated with thorium–based fuel cycles is a key reason for re–evaluating the possible utilization of thorium in high temperature reactors. In additio...

  20. Nonlinear Coordinated Control of AVR, SVC and TCSC%AVR、SVC与TCSC的非线性协调控制

    Institute of Scientific and Technical Information of China (English)

    翁利国; 李小腾; 夏彦辉

    2014-01-01

    The article establishes the integrated dynamic model of power systems including AVR, SVC and TCSC considering disturbance and then applies DFL and control theory to design a robust controller. The experiment in six generators system indicates the coordinated controller can improve the dynamic per-formance and transient stability of power systems, hence enhance the power transfer capacity of power systems.%本文致力于建立包含AVR( Automatic Voltage Regulator)、SVC( Static Var Compensator)和TCSC( Flexible Alternative Current Transmission Systems)的电力系统综合动态模型,模型中考虑了电力系统运行中可能遭受到的干扰;应用直接反馈线性化方法将系统的非线性状态方程精确线性化,再对线性化后的状态方程运用控制理论设计了鲁棒控制器。对六机系统的仿真实验证明了本文提出的AVR、SVC与TCSC的协调控制策略能够明显改善电力系统的动态性能、提高系统的暂态稳定水平,从而提高了系统的输电能力。

  1. Intracolonic multiple pebbles in young adults: Radiographic imaging and conventional approach to a case

    Institute of Scientific and Technical Information of China (English)

    Mehmet Eryilmaz; Orkun Ozturk; Oner Mentes; Kenan Soylu; Murat Durusu; K(o)ksal Oner

    2006-01-01

    Most of the foreign bodies detected in adult gastrointestinal systems are accidentally swallowed pins. In this study, we presented a case with intracolonic multiple pebbles. A 20-year-old man was admitted to emergency surgery policlinic for abdominal pain for 2 d without any alleviation or aggravation. His upright plain abdominal radiographic imaging revealed about 30-40 overt dense opacities in lumen of colonic segments, with oval and well shaped contours, each approximately 1cm x 1cm in size. The multiplanar reconstructions and threedimensional images combined with sectional screening showed that all pebbles had passed completely into the colon and no foreign bodies had remained in the ileal segments. On psychiatric assessment, he was found to have immature personality features, difficulty in overcoming stressors and adaptation disorder. He recovered by conservative management and radiographic monitoring applied during his follow-up. Thus, it can be concluded that, in differential diagnosis of abdominal pain in adult ages, though less frequently seen than in children,gastrointestinal system foreign bodies should always be kept in mind and it should be considered that ingestion of pebbles may be one of the factors contributing to abdominal pain particularly in young adults with psychiatric problems. In such cases suspected of having foreign bodies which cannot be detected by plain films, abdominal tomography can be an alternative for diagnostic imaging.

  2. Pomocný nástroj pro programování mikrokontrolérů AVR v jazyce C

    OpenAIRE

    ŠEVČÍK, Radek

    2008-01-01

    Tato práce popisuje program AVR Wizard, který byl vyvinut k vývojovému prostředí AVR Studio. Software AVR Wizard slouží k usnadnění programování tím, že po zadání používaných periférií vygeneruje kostru programu v jazyce C, která obsahuje přednastavení registrů a funkcí. Vytvořená kostra se zkopíruje do vývojového prostředí AVR Studio a zde je doprogramována do finální podoby. Výhodou programu je snadné ovládání a rychlé nastavení periférií bez nutnosti zdlouhavého vyhledávání v dokumentaci k...

  3. Validation of In-Situ Iron-Manganese Oxide Coated Stream Pebbles as Sensors for Arsenic Source Monitoring

    Science.gov (United States)

    Blake, J.; Peters, S. C.; Casteel, A.

    2013-12-01

    Locating nonpoint source contaminant fluxes can be challenging due to the inherent heterogeneity of source and of the subsurface. Contaminants such as arsenic are a concern for drinking water quality and ecosystem health. Arsenic contamination can be the result of several natural and anthropogenic sources, and therefore it can be difficult to trace and identify major areas of arsenic in natural systems. Identifying a useful source indicator for arsenic is a crucial step for environmental remediation efforts. Previous studies have found iron-manganese oxide coated streambed pebbles as useful source indicators due to their high attraction for heavy metals in water. In this study, pebbles, surface water at baseflow and nearby rocks were sampled from the Pennypack Creek and its tributaries, in southwestern Pennsylvania, to test the ability of coated streambed pebbles as environmental source indicators for arsenic. Quartz pebbles, 5-7 cm in diameter, were sampled to minimize elemental contamination from rock chemistry. In addition, quartz provides an excellent substrate for iron and manganese coatings to form. These coatings were leached from pebbles using 4M nitric acid with 0.1% concentrated hydrochloric acid. Following sample processing, analyses were performed using an ICP-MS and the resulting data were spatially organized using ArcGIS software. Arsenic, iron and manganese concentrations in the leachate are normalized to pebble surface area and each location is reported as a ratio of arsenic to iron and manganese. Results suggest that iron-manganese coated stream pebbles are useful indicators of arsenic location within a watershed.

  4. Improvement of hydrogen isotope exchange reactions on Li4SiO4 ceramic pebble by catalytic metals

    Institute of Scientific and Technical Information of China (English)

    Cheng Jian Xiao; Chun Mei Kang; Xiao Jun Chen; Xiao Ling Gao; Yang Ming Luo; Sheng Hu; Xiao Lin Wang

    2012-01-01

    Li4SiO4 ceramic pebble is considered as a candidate tritium breeding material of Chinese Helium Cooled Solid Breeder Test Blanket Module (CH HCSB TBM) for the International Thermonuclear Experimental Reactor (ITER).In this paper,Li4SiO4 ceramic pebbles deposited with catalytic metals,including Pt,Pd,Ru and Ir,were prepared by wet impregnation method.The metal particles on Li4SiO4 pebble exhibit a good promotion of hydrogen isotope exchange reactions in H2-DzO gas system,with conversion equilibrium temperature reduction of 200-300 ℃.The out-of-pile tritium release experiments were performed using 1.0 wt% Pt/Li4SiO4 and Li4SiO4 pebbles irradiated in a thermal neutron reactor.The thermal desorption spectroscopy shows that Pt was effective to increase the tritium release rate at lower temperatures,and the ratio of tritium molecule (HT) to tritiated water (HTO) of 1.0 wt% Pt/Li4SiO4 was much more than that of Li4SiO4,which released mainly as HTO.Thus,catalytic metals deposited on Li4SiO4 pebble may help to accelerate the recovery of bred tritium particularly in low temperature region,and increase the tritium molecule form released from the tritium breeding materials.

  5. Accretion of Cometary Nuclei in the Solar Nebula: Boulders, Not Pebbles

    Science.gov (United States)

    Weissman, Paul R.; A'Hearn, Michael

    2015-11-01

    Comets are the most primitive bodies in the solar system. They retain a largely unprocessed record of conditions in the primordial solar nebula 4.56 Gyr ago, including the initial accretion of dust and ice particles into macroscopic bodies. Current accretion theory suggests that ice and dust aggregates grew to pebble (cm) sizes before streaming instabilities and gravitational collapse brought these pebble swarms together as km-sized (or larger) bodies. Recent imaging of the nucleus of comet 67P/Churyumov-Gerasimenko by the Rosetta OSIRIS camera team has revealed the existence of “goose bump” terrain on the nucleus surface and lining the interior walls of large, ~200 m diameter and 180 m deep cylindrical pits. These pits are believed to be sinkholes, formed when near-surface materials collapse into voids within the nucleus, revealing the fresh comet interior on the walls of the pits. The goose bump terrain consists of 3-4 m diameter “boulders” randomly stacked one on top of another. We propose that these boulders, likely with an icy-conglomerate composition, are the basic building blocks of cometary nuclei. This is the first observational confirmation of current accretion theories, with the caveat that rather than pebbles, the preferred size range is 3-4 m boulders for objects formed in the giant planets region of the solar system. The presence of icy grains beyond the solar nebula snow-line and the large heliocentric range of the giant planets region likely contribute to the formation of these larger boulders, before they are incorporated into cometary nuclei. This work was supported by NASA through the U.S. Rosetta Project.

  6. Utilidad de la derivación aVR en la identificación de la arteria responsable en el infarto inferior

    Directory of Open Access Journals (Sweden)

    Yanina B. Castillo Costa

    2006-01-01

    Full Text Available El ECG es el método más simple para el diagnóstico de infarto inferior (IAMinf; sin embargo, su utilidad disminuye para determinar el vaso responsable. Objetivos 1. Analizar la utilidad del desnivel del ST en aVR en la identificación de oclusión de las arterias coronaria derecha (CD o circunfleja (CX. 2. Evaluar la utilidad agregada a los criterios clásicos. Material y métodos Se incluyeron en el estudio 65 pacientes con IAMinf a quienes se les realizó una cinecoronariografía (CCG durante la internación. Se analizaron los criterios clásicos, así como el desnivel del ST en aVR: ?ST =?1 mm, ?ST =?1 mm o nivelado (isoST a 0,08 seg del punto J y se calcularon la sensibilidad (S, la especificidad (E, el valor predictivo positivo (VPP, el valor predictivo negativo (VPN y el likelihood ratio (LR. Se incluyó la derivación aVR en un análisis multivariado para determinar su valor agregado a los criterios clásicos. Resultados La CD fue responsable de la oclusión en 47 pacientes (72% y la CX en 18 (28%. Signos clásicos : CD : la relación del ?STD3/D2 =?1 se halló en 52 pacientes (91,5%; p = 0,001 e ?STD1-aVL =?1 mm en 34 (61%; p 1 en 13 pacientes (50%; p = 0,001 y ?STV5-V6 =?1 mm en 12 (44%; p < 0,001. Derivación aVR : CD : ?ST o isoST en 46 pacientes (81%; p < 0,001; CX : ?ST =?1 mm en 19 (56%; p < 0,001. En el análisis multivariado, el ?ST o isoST en aVR identificó a la CD (OR IC 95% 4,7 (1,1-19,8; p = 0,03, mientras que el ?ST aVR identificó a la CX. Se propone un algoritmo diagnóstico para CD que refleja el valor aditivo de aVR a la presencia de los signos clásicos: ?ST o isoST en aVR (VPP 94%; LR+: 2. Conclusión La derivación aVR es una herramienta útil para la identificación de la arteria responsable en el IAMinf, ya que brinda información diagnóstica adicional a los signos clásicos.

  7. Making Planet Nine: Pebble Accretion at 250--750 AU in a Gravitationally Unstable Ring

    CERN Document Server

    Kenyon, Scott J

    2016-01-01

    We investigate the formation of icy super-Earth mass planets within a gravitationally unstable ring of solids orbiting at 250-750 AU around a 1 solar mass star. Coagulation calculations demonstrate that a system of a few large oligarchs and a swarm of pebbles generates a super-Earth within 100-200 Myr at 250 AU and within 1-2 Gyr at 750 AU. Systems with more than ten oligarchs fail to yield super-Earths over the age of the solar system. As these systems evolve, destructive collisions produce detectable debris disks with luminosities of $10^{-5}$ to $10^{-3}$ relative to the central star.

  8. Evidence of fast pebble growth near condensation fronts in the HL Tau protoplanetary disk

    OpenAIRE

    Zhang, Ke; Blake, Geoffrey A.; Bergin, Edwin A.

    2015-01-01

    Water and simple organic molecular ices dominate the mass of solid materials available for planetesimal and planet formation beyond the water snow line. Here we analyze ALMA long baseline 2.9, 1.3 and 0.87 mm continuum images of the young star HL Tau, and suggest that the emission dips observed are due to rapid pebble growth around the condensation fronts of abundant volatile species. Specifically, we show that the prominent innermost dip at 13 AU is spatially resolved in the 0.87 mm image, a...

  9. Brilliant Pebbles: A Method for Detection of Very Large Interstellar Grains

    CERN Document Server

    Socrates, Aristotle

    2008-01-01

    A photon of wavelength lambda ~ 1 micron interacting with a dust grain of radius a_p ~ 1 mm -- in other words, a "pebble" -- undergoes scattering in the forward direction, largely within a small characteristic diffraction angle theta_s ~ lambda/a_p ~100". Though mm-size dust grains contribute negligibly to the interstellar medium's visual extinction, the signal they produce in scattered light may be detectable for variable sources. Observations of variable light scattered into small angles allows for a direct measurement of the large grain population while also yielding tomographic information of the interstellar medium's mass distribution.

  10. Top Ten Bed Bug Tips

    Science.gov (United States)

    ... have bed bugs, not fleas, ticks or other insects. You can compare your insect to the pictures on our Identifying bed bugs ... bedbugs Bed Bugs Home Learn about Bed Bugs — Characteristics of Bed Bugs — Finding Bed Bugs Protecting Your ...

  11. Comparison of two-step diffusion solutions and Monte Carlo solutions to the IAEA CRP-5 pebble box benchmark problem

    Energy Technology Data Exchange (ETDEWEB)

    Hyun Chul, Lee; Qian, Hong; Kang-Seog, Kim; Jae Man, Noh [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2007-07-01

    This paper compares the two-step diffusion solutions and the Monte Carlo (MC) solutions to the recently proposed IAEA CRP-5 Pebble Box benchmark problem. MCNP code and a cross section library based on ENDF/B-VI were used for the reference MC solution. The pebbles in the cubic box were located in a Body Centered Cubic (BCC) lattice structure. Two MCNP geometry models for the problem were used in this work. No broken pebble is allowed in one model while broken pebbles are allowed at the boundary of the pebble box in the other model. HELIOS code was used for the cross section generation. For the singly heterogeneous cases, the Equivalent Cylinder Model (ECM) was used to transform a spherical pebble into an equivalent cylindrical fuel. For the doubly heterogeneous cases, the Reactivity-equivalent Physical Transformation (RPT) was used together with ECM to transform the doubly heterogeneous spherical pebble fuels into equivalent singly heterogeneous cylindrical fuels. For the graphite-reflected cases, infinite slab spectral geometries were used to generate the cross-sections. Space-dependent two-group cross-sections were generated from the spectral geometry problems with the help of the Equivalence Theory (ET). A transverse leakage (TL) correction technique was adopted, in which the transverse leakage was simulated in the HELIOS model by using an albedo boundary condition in the core region. CAPP (Core Analyzer for Pebble and Prism type VHTR reactors) code was used for the whole core diffusion calculation. The relative power density distributions of the two MCNP models were quite different from each other near the core/reflector boundary while the multiplication factors of the two models were very similar. Relatively large errors of diffusion solution in the homogeneous and singly heterogeneous cases were observed. The errors in the graphite-reflected cases were reduced considerable by the TL correction. The maximum multiplication factor errors and the RMS power errors

  12. Gas Reactor International Cooperative Program. Interim report. Construction and operating experience of selected European Gas-Cooled Reactors

    Energy Technology Data Exchange (ETDEWEB)

    1978-09-01

    The construction and operating experience of selected European Gas-Cooled Reactors is summarized along with technical descriptions of the plants. Included in the report are the AVR Experimental Pebble Bed Reactor, the Dragon Reactor, AGR Reactors, and the Thorium High Temperature Reactor (THTR). The study demonstrates that the European experience has been favorable and forms a good foundation for the development of Advanced High Temperature Reactors.

  13. Building the giant planet cores by convergent migration of pebble-accreting embryos

    Science.gov (United States)

    Chrenko, Ondrej; Broz, Miroslav

    2016-10-01

    An explanation of the accretion buildup of giant planet cores on rather short (~Myr) time scales remains a long-standing challenge for scenarios of planetary system formation. One of the recently proposed processes that can take part during this evolutionary stage is the convergent Type I migration of Earth-sized embryos towards the zero-torque radius, occurring at an opacity transition within the dusty-gaseous protoplanetary disk (e.g. Pierens et al. 2013). Inconveniently, simulations show that such groups of embryos do not merge easily because they often get locked in mutual mean-motion resonances and consequently form an inward-migrating convoy.We revise this possibility of merging embryos while taking into account their ongoing growth by pebble accretion. Our aim is to check whether the rapid changes of masses combined with the migration of embryos through the feeding zone can break the resonant chain and allow for the giant planet core formation.The environment of the protoplanetary disk is modeled with the 2D FARGO code (Masset 2000), which we modified in order to perform non-isothermal hydrodynamic simulations, assuming flux-limited radiative diffusion (Levermore & Pomraning 1981). The embedded massive bodies are evolved simultaneously in 3D using the hybrid Wisdom-Holman/Gauss-Radau integrator from the Rebound package (Rein & Spiegel 2015). A semi-analytic method is used to evolve the masses of embryos by pebble accretion (e.g. Levison et al. 2015).

  14. Surface energy equation for heat transfer process in a pebble fuel

    Energy Technology Data Exchange (ETDEWEB)

    Espinosa-Paredes, G., E-mail: gepe@xanum.uam.mx [Área de Ingeniería en Recursos Energéticos, Universidad Autónoma Metropolitana-Iztapalapa, Av. San Rafael Atlixco 186 Col. Vicentina, México, DF 09340 (Mexico); Castillo-Jiménez, V. [Área de Ingeniería en Recursos Energéticos, Universidad Autónoma Metropolitana-Iztapalapa, Av. San Rafael Atlixco 186 Col. Vicentina, México, DF 09340 (Mexico); Herranz-Puebla, L.E. [División de Fisión Nuclear, Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas, Avda. Complutense, 22, 28040 Madrid (Spain); Vázquez-Rodríguez, R. [Área de Ingeniería en Recursos Energéticos, Universidad Autónoma Metropolitana-Iztapalapa, Av. San Rafael Atlixco 186 Col. Vicentina, México, DF 09340 (Mexico)

    2014-12-15

    Highlights: • Steady and transient behaviors of the interfacial heat transfer in a fuel element. • Non-local averaging volume method for deriving the surface energy equation. • The method captures significant physical phenomena of the interfacial heat transfer. • Closure relationships are proposed in order to obtain the temperatures distribution. • The derived average equation represents an upscaling regarding the local description. - Abstract: In this paper the surface energy equation for the heat transfer process (HT) between the mixture of fuel (TRISO particles and graphite matrix) and coating in a fuel pebble is derived. The fuel pebble can be treated as a heterogeneous region (mixture of microspheres and graphite) interacting thermally with the homogeneous region (the coating or cladding). These two regions are separated by a boundary region where the properties and behavior differ from those of the adjoining regions. The methodology applied for deriving the surface energy equation is based on the classical theory on interfacial transport phenomena. The surface energy equation derived in this work is an average equation that represents an upscaling respect to the local description. The regions around the surface where changes in the physical phenomena are important are of the order of microns, in contrast with interfacial mass transfer between phases that may be several molecular diameters. The numerical analysis regarding the application of surface energy equation is presented in this work.

  15. AVR单片机实现以太网通信的研究%Reaching for the serial of AVR Microchip about Ethernet communication

    Institute of Scientific and Technical Information of China (English)

    于海波; 付江波; 李金涛

    2012-01-01

    This paper introduced the design of Ethernet communication based on the serial of AVR microchip,at the same time reaching for driver program about the chip of ENC28J60 and designed the system software on the serial of AVR microchip.%研究基于Atmega16单片机与网络接口芯片ENC28J60实现以太网通信技术,详述ENC28J60网络接口芯片的特点及其应用,同时讨论ENC28J60驱动程序和系统软件程序的设计。

  16. Pebble Dumplings

    Institute of Scientific and Technical Information of China (English)

    1999-01-01

    Ingredients:Polished glutinous rice powder, yellow cheese powder,cocoa powder, and red bean paste or other for stuffing.Method:1. Mix the rice powder with cheese and cocoa powdersrespectively, add in water and roll a yellow dough and abrown dough; prepare another pure rice powder

  17. A comparison between different methods for determining grain distribution in coarse channel beds

    Institute of Scientific and Technical Information of China (English)

    Alessio Cislaghi; Enrico Antonio Chiaradia; Gian Battista Bischetti

    2016-01-01

    The determination of grain size distribution in alluvial channels plays a crucial role in understanding fluvial dynamics and processes (e.g., hydraulic resistance, sediment transport and erosion, and habitat suitability). However, to determine an accurate distribution, tremendous field efforts are often required. Traditionally, the grain size distribution of channel beds have been obtained by manually counting a set of randomly selected stones (the“pebble count”). Based on this elementary principle, many authors have proposed different adaptations to overcome weaknesses and problems with the original method; with the development of digital technology, photographic methods have been developed in order to sig-nificantly reduce the time spent in the field. Two of these“image-assisted”methods include Automated Grain Sizing, AGS, and Manual Photo Sieving, MPS. In this study, AGS and MPS were applied under ideal laboratory conditions, to be used as reference, and in two field conditions with different degrees of difficulty in terms of visual determination of the grain size distribution; these included an artificial unlined channel and two natural mountainous streams. The results were compared with those obtained with the pebble-count method. In general, strong agreement between the methods was found when they were applied under favorable conditions (”the laboratory”), and the differences between the image-assisted and pebble count methods were similar to those found in previous studies. Despite being more time consuming, MPS was deemed preferable to AGS when conditions are not optimal;in these cases, the time spent on image elaboration significantly increased in the AGS method (approximately three-fold), but the estimation error of the median grain size decreased by approximately 37%. The use of image-assisted analysis has proven to be robust for characterizing sediment in watercourse beds and reducing fieldwork time, but because field conditions can

  18. WtsE, an AvrE-family type III effector protein of Pantoea stewartii subsp. stewartii, causes cell death in non-host plants.

    Science.gov (United States)

    Ham, Jong Hyun; Majerczak, Doris; Ewert, Sophie; Sreerekha, Mysore-Venkatarau; Mackey, David; Coplin, David

    2008-09-01

    Pantoea stewartii subsp. stewartii (Pnss) causes Stewart's bacterial wilt of sweet corn and leaf blight of maize. The pathogenicity of Pnss depends on synthesis of extracellular polysaccharide and an Hrp type III secretion system. WtsE, a type III secreted effector protein, is essential for the virulence of Pnss on corn. It belongs to the AvrE family of effectors, which includes DspA/E from Erwinia amylovora and AvrE1 from Pseudomonas syringae. Previously, WtsE was shown to cause disease-associated cell death in its host plant, sweet corn. Here, we examine the biological activity of WtsE in several non-host plants. WtsE induced cell death in Nicotiana benthamiana, tobacco, beet and Arabidopsis thaliana when it was transiently produced in plant cells following agroinfiltration or translocated into plant cells from Pnss, Escherichia coli or Pseudomonas syringae pv. phaseolicola (Pph). WtsE-induced cell death in N. benthamiana, tobacco and beet resembled a hypersensitive response and in N. benthamiana it was delayed by cycloheximide. Interestingly, WtsE strongly promoted the growth of Pnss in N. benthamiana prior to the onset of cell death. Deletion derivatives of WtsE that failed to induce cell death in N. benthamiana and tobacco also did not complement wtsE mutants of Pnss for virulence in sweet corn, indicating a correlation between the two activities. WtsE also induced cell death in A. thaliana, where it suppressed basal defences induced by Pph. Thus, WtsE has growth-promoting, defence-suppressing and cell death-inducing activities in non-host plants. Expression of WtsE also prevented the growth of yeast, possibly due to an innate toxicity to eukaryotic cells. PMID:19018993

  19. Leptosphaeria maculans effector AvrLm4-7 affects salicylic acid (SA) and ethylene (ET) signalling and hydrogen peroxide (H2 O2 ) accumulation in Brassica napus.

    Science.gov (United States)

    Nováková, Miroslava; Šašek, Vladimír; Trdá, Lucie; Krutinová, Hana; Mongin, Thomas; Valentová, Olga; Balesdent, Marie-HelEne; Rouxel, Thierry; Burketová, Lenka

    2016-08-01

    To achieve host colonization, successful pathogens need to overcome plant basal defences. For this, (hemi)biotrophic pathogens secrete effectors that interfere with a range of physiological processes of the host plant. AvrLm4-7 is one of the cloned effectors from the hemibiotrophic fungus Leptosphaeria maculans 'brassicaceae' infecting mainly oilseed rape (Brassica napus). Although its mode of action is still unknown, AvrLm4-7 is strongly involved in L. maculans virulence. Here, we investigated the effect of AvrLm4-7 on plant defence responses in a susceptible cultivar of B. napus. Using two isogenic L. maculans isolates differing in the presence of a functional AvrLm4-7 allele [absence ('a4a7') and presence ('A4A7') of the allele], the plant hormone concentrations, defence-related gene transcription and reactive oxygen species (ROS) accumulation were analysed in infected B. napus cotyledons. Various components of the plant immune system were affected. Infection with the 'A4A7' isolate caused suppression of salicylic acid- and ethylene-dependent signalling, the pathways regulating an effective defence against L. maculans infection. Furthermore, ROS accumulation was decreased in cotyledons infected with the 'A4A7' isolate. Treatment with an antioxidant agent, ascorbic acid, increased the aggressiveness of the 'a4a7' L. maculans isolate, but not that of the 'A4A7' isolate. Together, our results suggest that the increased aggressiveness of the 'A4A7' L. maculans isolate could be caused by defects in ROS-dependent defence and/or linked to suppressed SA and ET signalling. This is the first study to provide insights into the manipulation of B. napus defence responses by an effector of L. maculans. PMID:26575525

  20. Numerical simulation of the facility behaviour of a high temperature reactor under water ingress accidents at the example of the AVR

    International Nuclear Information System (INIS)

    Detailed analysis of massive water ingress accidents in high temperature reactors supposes a numerical simulation of the whole facility behaviour. For the AVR-reactor such a model was developed to describe both, the graphite corrosion processes and the accident transients for different releasing events as well as resulting accident profiles. The variable consideration of regulating facilities of the safety circuit being influenced in reality, enables an optimization of the accident profiles in the way of a least possible facility damage. It results that in spite of extremely conservative input data with authorization legal relevance even the possible water ingress accidents can safely be controlled after 15 years of operation with steadily increasing safety requirements. First investigations on a selected facility concept for the AVR-reequipment show, that with the definition up to now of the AVR-steam generator failure the accident profiles ''reactor under pressure'' are conservatively coped with. An increasing degree of detail of the concept proposals, however, requires an examination of this statement. (orig.)

  1. Density improvement of Li{sub 2}TiO{sub 3} pebbles fabricated by wet process

    Energy Technology Data Exchange (ETDEWEB)

    Tsuchiya, K.; Kawamura, H. [Japan Atomic Energy Research Inst., Oarai, Ibaraki (Japan). Oarai Research Establishment; Fuchinoue, K.; Sawada, H.; Watarumi, K.

    1998-03-01

    Lithium titanate (Li{sub 2}TiO{sub 3}) has attracted the attention of many researchers from a point of tritium recovery at low temperature, chemical stability, etc.. The application of small Li{sub 2}TiO{sub 3} sphere has been proposed in some designs of fusion blanket. On the other hand, the wet process is most advantageous as the fabrication method of Li{sub 2}TiO{sub 3} pebbles from a point of mass production, and of reprocessing necessary for effective use of resources and reduction of radioactive wastes. In the preliminary fabrication test, density of Li{sub 2}TiO{sub 3} pebbles was about 40%T.D.. Therefore, in this study, density improvement tests and preliminary characterization of Li{sub 2}TiO{sub 3} pebbles by wet process were performed, noting the aging condition and sintering condition in the fabrication process of the gel-spheres. This study yielded Li{sub 2}TiO{sub 3} pebbles in target range of 80-85%T.D.. (author)

  2. Characterization of PEBBLEs as a Tool for Real-Time Measurement of Dictyostelium discoideum Endosomal pH

    Directory of Open Access Journals (Sweden)

    Everett Moding

    2009-01-01

    Full Text Available The measurement of intracellular ion concentration change is important for understanding the cellular mechanisms for communication. Recently developed nanosensors, (Photonic Explorers for Biomedical use with Biologically Localized Embedding PEBBLEs, have a number of advantages for measuring ions in cells over established methods using microelectrodes, unbound fluorescent dyes, or NMR. PEBBLE sensors have been shown to work in principle for measuring dynamic ion changes, but few in vivo applications have been demonstrated. We modified the protocol for the fabrication of pH sensing PEBBLEs and developed a protocol for the utilization of these sensors for the monitoring of dynamic pH changes in the endosomes of slime mold Dictyostelium discoideum (D. discoideum. Oregon Green 514-CdSe Quantum Dot PEBBLEs were used to measure real-time pH inside D. discoideum endosomes during cAMP stimulation. Endosomal pH was shown to decrease during cAMP signaling, demonstrating a movement of protons into the endosomes of D. discoideum amoebae.

  3. AVR-51单片机多功能实验开发板的研制及实验教学应用%Development of Multi-function Experiment and Development Board Based on AVR-51 MCU

    Institute of Scientific and Technical Information of China (English)

    李庆利; 马潮; 金豫; 刘中元

    2013-01-01

    A multi-function experiment and development board based on AVR MCU is developed. The hardware structure of the board adopts the form of functional module, and individual part is independent mutually to integrate flexibly so as to provide the basic function of the experiment board. Practical application shows that the experiment and development board improves the technical level of the MCU experiment and students' design ability..%  研制了AVR单片机多功能实验开发板,实验板的硬件结构采用功能模块的形式,各单元相互独立,可以灵活组合并给出了实验板的基本功能。实际应用表明,该实验板提高了实验技术水平,锻炼了学生综合设计能力。

  4. 基于 AVR 单片机的直流电机控制系统设计%Dc Motor Control System Based on AVR Single-chip Computer Design

    Institute of Scientific and Technical Information of China (English)

    姜颖韬

    2013-01-01

    MUC-controlled motor drive platform has been demanded widely in engineering field ,so the author designed a new scheme with AVR single chip microcomputer as main control chip .By using this scheme ,the motor drive platform has some advantages ,such as lightweight ,efficient ,low consumption ,good real-time performance ,which can be widely used in indus-trial and agricultural production ,civil life ,education ,scientific research and other fields .%针对在工程领域内具有广泛需求的MUC控制电动机驱动的动力平台,开发了一种以AVR单片机作为主控芯片的新方案。应用该方案设计的动力平台系统具有轻量化、高效低耗、实时性好等优点,可广泛应用于工农业生产、民用生活、教育科研等领域。

  5. Using pebble lithology and roundness to interpret gravel provenance in piedmont fluvial systems of the Rocky Mountains, USA

    Science.gov (United States)

    Lindsey, D.A.; Langer, W.H.; Van Gosen, B. S.

    2007-01-01

    Clast populations in piedmont fluvial systems are products of complex histories that complicate provenance interpretation. Although pebble counts of lithology are widely used, the information provided by a pebble count has been filtered by a potentially large number of processes and circumstances. Counts of pebble lithology and roundness together offer more power than lithology alone for the interpretation of provenance. In this study we analyze pebble counts of lithology and roundness in two contrasting fluvial systems of Pleistocene age to see how provenance varies with drainage size. The two systems are 1) a group of small high-gradient incised streams that formed alluvial fans and terraces and 2) a piedmont river that formed terraces in response to climate-driven cycles of aggradation and incision. We first analyze the data from these systems within their geographic and geologic context. After this is done, we employ contingency table analysis to complete the interpretation of pebble provenance. Small tributary streams that drain rugged mountains on both sides of the Santa Cruz River, southeast Arizona, deposited gravel in fan and terrace deposits of Pleistocene age. Volcanic, plutonic and, to a lesser extent, sedimentary rocks are the predominant pebble lithologies. Large contrasts in gravel lithology are evident among adjacent fans. Subangular to subrounded pebbles predominate. Contingency table analysis shows that hard volcanic rocks tend to remain angular and, even though transport distances have been short, soft tuff and sedimentary rocks tend to become rounded. The Wind River, a major piedmont stream in Wyoming, drains rugged mountains surrounding the northwest part of the Wind River basin. Under the influence of climate change and glaciation during the Pleistocene, the river deposited an extensive series of terrace gravels. In contrast to Santa Cruz tributary gravel, most of the Wind River gravel is relatively homogenous in lithology and is rounded to

  6. Synthesis and fabrication of lithium-titanate pebbles for ITER breeding blanket by solid state reaction and spherodization

    Energy Technology Data Exchange (ETDEWEB)

    Mandal, D., E-mail: dmandal@barc.gov.i [Chemical Engineering Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085 (India); Shenoi, M.R.K.; Ghosh, S.K. [Chemical Engineering Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085 (India)

    2010-08-15

    {sup 6}Li produces tritium by (n, {alpha}) nuclear reaction, {sup 6}Li + {sup 1}n {yields} {sup 4}He + {sup 3}H. Lithium titanate (Li{sub 2}TiO{sub 3}) enriched with {sup 6}Li, is the most promising candidate for solid test blanket module (TBM) material for fusion reactors. Various processes are reported in literature for the fabrication of Li{sub 2}TiO{sub 3} pebbles for its use as TBM material. A process has been developed based on the solid state reaction of lithium-carbonate and titanium-dioxide for the synthesis of lithium titanate and pebble fabrication by extrusion, spherodization and sintering. This paper discusses the sequence of steps followed in this process and the properties obtained. Analytical grade titanium-dioxide and lithium-carbonate were taken in stoichiometric ratio and were milled to ensure thorough intimate mixing and obtain fine particles less than 45 {mu}m before its calcination at 900 {sup o}C. Following calcination, the agglomerated product was again milled to fine particles of size less than 45 {mu}m. Aqueous solution of ploy-vinyl-alcohol was added as binder prior to its feeding in the extruder. The extruded strips were spherodized and spherical pebbles were dried and sintered at 900 {sup o}C for different duration. Pebbles of desired density and porosity were obtained by suitable combination of sintering temperature and duration of sintering. Properties of the prepared pebbles were also characterized for sphericity, pore size distribution, grain size, crushing load strength, etc. The values were found to be conforming to the desired properties for use as solid breeder. The attractive feature of this process is almost no waste generation.

  7. Bed In Summer

    Institute of Scientific and Technical Information of China (English)

    2011-01-01

    In winter I get up at night And dress by yellow candle-light. In summer, quite the other way, I have to go to bed by day. I have to go to bed and see The birds still hopping on the tree, Or hear the grown-up people' s feet Still going past me in the stree

  8. Fluidized bed incinerator development

    International Nuclear Information System (INIS)

    A fluidized bed incinerator is being developed for burning rad contaminated solid and liquid waste materials. In situ neutralization of acid gases by the bed material, catalytic afterburning, and gas filtration are used to produce a clean flue gas without the use of aqueous scrubbing

  9. Fluidized bed calciner apparatus

    Science.gov (United States)

    Owen, Thomas J.; Klem, Jr., Michael J.; Cash, Robert J.

    1988-01-01

    An apparatus for remotely calcining a slurry or solution feed stream of toxic or hazardous material, such as ammonium diurante slurry or uranyl nitrate solution, is disclosed. The calcining apparatus includes a vertical substantially cylindrical inner shell disposed in a vertical substantially cylindrical outer shell, in which inner shell is disposed a fluidized bed comprising the feed stream material to be calcined and spherical beads to aid in heat transfer. Extending through the outer and inner shells is a feed nozzle for delivering feed material or a cleaning chemical to the beads. Disposed in and extending across the lower portion of the inner shell and upstream of the fluidized bed is a support member for supporting the fluidized bed, the support member having uniform slots for directing uniform gas flow to the fluidized bed from a fluidizing gas orifice disposed upstream of the support member. Disposed in the lower portion of the inner shell are a plurality of internal electric resistance heaters for heating the fluidized bed. Disposed circumferentially about the outside length of the inner shell are a plurality of external heaters for heating the inner shell thereby heating the fluidized bed. Further, connected to the internal and external heaters is a means for maintaining the fluidized bed temperature to within plus or minus approximately 25.degree. C. of a predetermined bed temperature. Disposed about the external heaters is the outer shell for providing radiative heat reflection back to the inner shell.

  10. Rotation angles and angular velocities study of pebble-shaped fuel element based on a detection system%球形燃料元件累积旋转角度和角速度问题研究

    Institute of Scientific and Technical Information of China (English)

    赵颖; 朱兴望; 曲世祥; 陈堃

    2016-01-01

    Background: Pebble Bed Reactor (PBR), most often used in Generation IV high-temperature gas-cooled nuclear reactor, employs pebble-shaped fuel elements. As pebbles flow through the reactor, they will slide and rotate against each other and the wall, causing generation of graphite dust.Purpose:This study aims to investigate the rotation angles and angular velocities of pebble-shaped fuel elements (PSFE). Methods: The rotation angle and angular velocity were studied by using a simulated transparent cylinder to replace the reactor core. A pebble-shaped detection system is employed to test the angular velocities and accumulated rotation angles of PSFEs with wireless interface. The generation of graphite particles by rotational abrasion was also studied.Results:The experimental results show that the initial seeding position has influence on rotation angles and angular velocities. The distribution of rotation angles and angular velocities from the center to the wall can be described as an inverted V-type distribution. The calculation results show that wear mass by rotation accounts for 11%?27% of the total graphite dust.Conclusion: Sliding abrasion is stronger than rotation abrasion in general, graphite generation tends to be overestimated if we only take sliding abrasion into consideration and ignore rotation abrasion.%球床堆采用球形燃料元件,其在循环过程中存在滚动磨损以及滑动磨损并产生石墨粉尘.本文借助一种球形无线探测系统量化了角速度及累计旋转角度,并量化了滚动磨损对石墨粉尘产生的影响.实验结果表明,累计旋转角度和角速度与初始径向位置有关,随着初始径向位置由里向外,呈V字型分布,与仓筒边壁接触的球累计旋转角度和角速度远大于其他位置,边壁滚动效应显著.计算结果表明,滚动磨损对石墨粉尘产生量的贡献在11%?27%,且靠近仓筒边壁处该百分比高于其他位置,边壁效应明显.一般情况下,滚动磨

  11. Fabrication of Li{sub 2}TiO{sub 3} pebbles with small grain size via hydrothermal and improved dry-rolling methods

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Wen; Zhou, Qilai; Xue, Lihong, E-mail: xuelh@mail.hust.edu.cn; Yan, Youwei

    2015-09-15

    Highlights: • The fabricated pebbles can be densified (81% T.D.) at a low sintering temperature (850 °C). • The pebbles’ size can be controlled during the fabrication process. • Average grain size of the Li{sub 2}TiO{sub 3} pebbles is less than 1 μm (0.82 μm). • The molar ratio of Li to Ti of the pebbles sintered at 850 °C keeps the value of 1.97 after sintering. - Abstract: Lithium titanate (Li{sub 2}TiO{sub 3}) ceramic pebbles were successfully fabricated by using hydrothermal and improved dry-rolling method. In the present work, ultra-fine Li{sub 2}TiO{sub 3} powder of high reactivity was prepared via hydrothermal reaction, using anatase titania and lithium hydroxide as raw materials. The as-synthesized Li{sub 2}TiO{sub 3} powder exhibits an average crystalline size as small as 100 nm. Improved dry-rolling method was employed to fabricate Li{sub 2}TiO{sub 3} pebbles. The green pebbles can be well-sintered (81% T.D.) at a temperature as low as 850 °C for 3 h. The pebbles have good sphericity (1.08) and narrow diameter distribution (1.0–1.2 mm) with a crush load of 35 N. Scanning electron microscope (SEM) observations of pebbles showed that the ceramic grain size was below 1 μm and atomic emission spectrometer fitted with inductively coupled plasma (ICP-AES) results confirmed that atomic ratio of Li to Ti in the fabricated pebbles was 1.97.

  12. A pebbles accretion model with chemistry and implications for the solar system

    CERN Document Server

    Ali-Dib, Mohamad

    2016-01-01

    We investigate the chemical composition of the solar system's giant planets atmospheres using a physical formation model with chemistry. The model incorporate disk evolution, pebbles and gas accretion, type I and II migration, simplified disk photoevaporation and solar system chemical measurements. We track the chemical compositions of the formed giant planets and compare them to the observed values. Two categories of models are studied: with and without disk chemical enrichment via photoevaporation. Predictions for the Oxygen and Nitrogen abundances, core masses, and total amount of heavy elements for the planets are made for each case. We find that in the case without disk PE, both Jupiter and Saturn will have a small residual core and comparable total amounts of heavy elements in the envelopes. We predict oxygen abundances enrichments in the same order as carbon, phosphorus and sulfur for both planets. Cometary Nitrogen abundances does not allow to easily reproduce Jupiter's nitrogen observations. In the c...

  13. An orientation soil survey at the Pebble Cu-Au-Mo porphyry deposit, Alaska

    Science.gov (United States)

    Smith, Steven M.; Eppinger, Robert G.; Fey, David L.; Kelley, Karen D., (Edited By); Giles, S.A.

    2009-01-01

    Soil samples were collected in 2007 and 2008 along three traverses across the giant Pebble Cu-Au-Mo porphyry deposit. Within each soil pit, four subsamples were collected following recommended protocols for each of ten commonly-used and proprietary leach/digestion techniques. The significance of geochemical patterns generated by these techniques was classified by visual inspection of plots showing individual element concentration by each analytical method along the 2007 traverse. A simple matrix by element versus method, populated with a value based on the significance classification, provides a method for ranking the utility of methods and elements at this deposit. The interpretation of a complex multi-element dataset derived from multiple analytical techniques is challenging. An example of vanadium results from a single leach technique is used to illustrate the several possible interpretations of the data.

  14. Cloning and functional analysis of the genes involved in signal transduction in tomato Cf-4-Avr4 pathosystem

    Institute of Scientific and Technical Information of China (English)

    LIU Qing; FENG Dongxin; WANG Xiaowu; DU Yongchen

    2007-01-01

    Hypersensitive response(HR)is one of the most efficient and common resistance mechanisms in plants.Cloning signaling genes are very important to elucidate the resistance mechanisms.A gene in tomato homologous to several resistance proteins in plant was involved in HR and named as RGL(Resistance Gene Like).RGL protein was used as a bait to screen interacting protein(s)from tomato cDNA library through the yeast two-hybrid system.Two interacting proteins were found,which were called as RGLIP-I and RGLIP2(RGL Interacting Protein),respectively.RGLIP-1 is a protein of 291 amino acids with significant homology with thylakoid lumen protein.RGLIP-2 is a protein of 248 amino acids with significant homology with transducin protein.Virus-Induced Gene Silencing(VIGS)of the two genes results in a partial and complete suppression of Avr4induced HR,which indicates that both genes are involved in hypersensitive response.

  15. Optimum Design of Fractional Order PID Controller for an AVR System Using an Improved Artificial Bee Colony Algorithm

    Institute of Scientific and Technical Information of China (English)

    ZHANG Dong-Li; TANG Ying-Gan; GUAN Xin-Ping

    2014-01-01

    Fractional order proportional-integral-derivative (FOPID) controller generalizes the standard PID controller. Compared to PID controller, FOPID controller has more pa-rameters and the tuning of parameters is more complex. In this paper, an improved artificial bee colony algorithm, which com-bines cyclic exchange neighborhood with chaos (CNC-ABC), is proposed for the sake of tuning the parameters of FOPID con-troller. The characteristic of the proposed CNC-ABC exists in two folds: one is that it enlarges the search scope of the solution by utilizing cyclic exchange neighborhood techniques, speeds up the convergence of artificial bee colony algorithm (ABC). The other is that it has potential to get out of local optima by exploit-ing the ergodicity of chaos. The proposed CNC-ABC algorithm is used to optimize the parameters of the FOPID controller for an automatic voltage regulator (AVR) system. Numerical sim-ulations show that the CNC-ABC FOPID controller has better performance than other FOPID and PID controllers.

  16. Bathing a patient in bed

    Science.gov (United States)

    Bed bath; Sponge bath ... Some patients cannot safely leave their beds to bathe. For these people, daily bed baths can help keep their skin healthy, control odor, and increase comfort. If moving the ...

  17. HTR-2000: Computer program to accompany calculations during reactor operation of HTGR's

    International Nuclear Information System (INIS)

    HTR-2000 - developed for arithmetical control of pebble bed high temperature reactors with multiple process - is closely coupled to the actual operation of the reactor. Using measured nuclear and thermo-hydraulical parameters as well as detailed model of pebble flow and exact information and fuel burnup, loading and discharge it obtains an excellent simulation of the status of the reactor. The geometry is modelled in three dimensions, so asymmetries in core texture can be taken into account for nuclear and thermohydraulical calculations. A continuous simulation was performed during five years of AVR operation. The comparison between calculated and measured data was very satisfying. In addition, experiments which had been performed at AVR for re-calculating the control rod worth were simulated. The arithmetical analysis shows that at presence of a compensating-absorber in the reactor core the split reactivity worth for single absorbers can be determined by calculation but not by methods of measuring. (orig.)

  18. A fully automatic control photovoltaic pumping system based on AVR microcontroller%基于 AVR 单片机的全自动光伏水泵系统

    Institute of Scientific and Technical Information of China (English)

    施爱平; 许冠杰; 施健

    2016-01-01

    A control structure based on AVR microcontroller was proposed to explore a novel adaptive maximum power point tracking (MPPT)algorithm for photovoltaic (PV)pumping systems.DC -AC converter duty cycle was derived according to the principle of genetic algorithm and by combining the genetic algorithm and perturbation and the observation (P &O)method for duty cycle to search the maximum power point of the photovoltaic pumping system quickly and overcome interference on the controller caused by the dramatic changes in the external environment.The adaptability and stability of the MPPT method based on the genetic algorithm were validated in Simulink environment.Water pum-ping experiment was made on a test rig built for the designed photovoltaic pumping system to realize MPPT.It is shown that the system can respond the continuous change in climate exactly,causing a stable overall efficiency as good as 60%.There is a 10% improvement in comparison with the 50% ef-ficiency of ordinary PV systems.Therefore,the developed system can provide a reliable control on the load of PV pump,but also its operation is stable with a higher overall efficiency.The work can provide a reference for optimal control of photovoltaic pumping systems.%为探究一种新型的自适应最大功率跟踪算法,提出了基于 AVR 单片机的光伏水泵系统控制结构。将遗传算法与占空比扰动观察法(P&O)相结合,根据遗传算法的原理计算推导出 DC -AC 变换器的占空比,可以实现快速搜索到光伏水泵系统的最大功率跟踪点,以克服外界环境的剧烈变化对控制器造成的干扰。通过 Simulink 环境下的仿真试验,验证了基于遗传算法实现的MPPT 方法具有良好的自适应性以及稳定性。在光伏水泵系统的试验平台上进行相关的抽水试验,结果表明:建立于遗传算法进而实现 MPPT 算法而设计的系统,对于外界不断的气候变化,该光伏水泵系统都可以较

  19. Tapered bed bioreactor

    Science.gov (United States)

    Scott, Charles D.; Hancher, Charles W.

    1977-01-01

    A vertically oriented conically shaped column is used as a fluidized bed bioreactor wherein biologically catalyzed reactions are conducted in a continuous manner. The column utilizes a packing material a support having attached thereto a biologically active catalytic material.

  20. Particle fuel bed tests

    International Nuclear Information System (INIS)

    Gas-cooled reactors, using packed beds of small diameter coated fuel particles have been proposed for compact, high-power systems. The particulate fuel used in the tests was 800 microns in diameter, consisting of a thoria kernel coated with 200 microns of pyrocarbon. Typically, the bed of fuel particles was contained in a ceramic cylinder with porous metallic frits at each end. A dc voltage was applied to the metallic frits and the resulting electric current heated the bed. Heat was removed by passing coolant (helium or hydrogen) through the bed. Candidate frit materials, rhenium, nickel, zirconium carbide, and zirconium oxide were unaffected, while tungsten and tungsten-rhenium lost weight and strength. Zirconium-carbide particles were tested at 2000 K in H2 for 12 hours with no visible reaction or weight loss

  1. Enuresis (Bed-Wetting)

    Science.gov (United States)

    ... get out of bed to go to the bathroom. When do most children achieve bladder control? Children ... ask questions about your child's daytime and nighttime bathroom habits. Then your doctor will do a physical ...

  2. Recovery and recycling of lithium value from spent lithium titanate (Li2TiO3) pebbles

    Science.gov (United States)

    Mandal, D.

    2013-09-01

    In the first generation fusion reactors the fusion of deuterium (D) and tritium (T) is considered to produce energy to meet the future energy demand. Deuterium is available in nature whereas, tritium is not. Lithium-6 (Li6) isotope has the ability to produce tritium in the n, α nuclear reaction with neutrons. Thus lithium-based ceramics enriched by Li6 isotope are considered for the tritium generation for its use in future fusion reactors. Lithium titanate is one such Li-based ceramic material being considered for its some attractive properties viz., high thermal and chemical stability, high thermal conductivity, and low tritium solubility. It is reported in the literature, that the burn up of these pebbles in the fusion reactor will be limited to only 15-17 atomic percentage. At the end of life, the pebbles will contain more than 45% unused Li6 isotope. Due to the high cost of enriched Li6 and the waste disposal considerations, it is necessary to recover the unused Li from the spent lithium titanate pebbles. Till date, only the feasibilities of different processes are reported, but no process details are available. Experiments were carried out for the recovery of Li from simulated Li2TiO3 pebbles and to reuse of lithium in lithium titanate pebble fabrication. The details of the experiments and results are discussed in this paper. Simulated lithium titanate (Li2TiO3) pebbles. The objective of the study is to develop a process which can be used to recover lithium value form the spent Li2TiO3 pebbles from future fusion reactor. The Li2TiO3 pebbles used in the study were synthesized and fabricated by the solid state reaction process developed by Mandal et al. described in details somewhere else [1,2]. Spherical Li2TiO3 pebbles of size 1.0 mm were used and the properties of the Li2TiO3 pebbles used in the study are shown in Table 1. Hydrochloric acid (HCl), of 99.8% purity, purchased from Merck and Loba Chemicals, Mumbai, India. To leach lithium from Li2TiO3

  3. Bed rest and immunity

    Science.gov (United States)

    Sonnenfeld, Gerald; Aviles, Hernan; Butel, Janet S.; Shearer, William T.; Niesel, David; Pandya, Utpal; Allen, Christopher; Ochs, Hans D.; Blancher, Antoine; Abbal, Michel

    2007-02-01

    Space flight has been shown to result in altered immune responses. The current study was designed to investigate this possibility by using the bed rest model of some space flight conditions. A large number of women are included as subjects in the study. The hypothesis being tested is: 60 days head-down tilt bed rest of humans will affect the immune system and resistance to infection. Blood, urine and saliva samples will be obtained from bed rest subjects prior to, at intervals during, and after completion of 60 days of head-down tilt bed rest. Leukocyte blastogenesis, cytokine production and virus reactivation will be assessed. The ability of the subjects to respond appropriately to immunization with the neoantigen bacteriophage φX-174 will also be determined. Bed rest is being carried out at MEDES, Toulouse France, and the University of Texas Medical Branch, Galveston, TX. The studies to be carried out in France will also allow assessment of the effects of muscle/bone exercise and nutritional countermeasures on the immune system in addition to the effects of bed rest.

  4. Design of Rotating LED Display Screen Based on AVR%基于AVR的LED旋转屏设计

    Institute of Scientific and Technical Information of China (English)

    张立霞; 周立余; 冯新

    2011-01-01

    In order to gain a small size and low cost display screen and achieve a more abundant display effect, a cylindrical new LED display screen was designed. This screen comes true with a line of SMD LED lightings which is rotated by a DC motor and controlled by ATmega16L which is the key control chip based on AVR MCU. The wireless Lnfrared remote control is used to switch display content at any moment to show different letters, patterns and system time. With the equivalent display effects , using less number of LEDs instead of mass LEDs is achieved. Meanwhile, the screen shows that the angle of view becomes wider, and is up to 360-degree in the process of rotation.%为了使显示屏的体积更小,成本更低,同时又能有较丰富的显示效果,采用AVR微处理嚣ATmegal6L作为核心控制芯片,由直流电机带动一列贴片LED旋转设计了圆柱形LED显示屏,可以由无线红外遥控装置随时切换显示的内容,可显示不同的文字,图案、系统时间等.利用少量发光二极管实现海量发光二极管才能实现的显示屏,同时该屏在旋转过程中显示,使得可视角更广,可以达到360.全方位.

  5. USGS exploration geochemistry studies at the Pebble porphyry Cu-Au-Mo deposit, Alaska-pdf of presentation

    Science.gov (United States)

    Eppinger, Robert G.; Kelley, Karen D.; Fey, David L.; Giles, Stuart A.; Minsley, Burke J.; Smith, Steven M.

    2010-01-01

    From 2007 through 2010, scientists in the U.S. Geological Survey (USGS) have been conducting exploration-oriented geochemical and geophysical studies in the region surrounding the giant Pebble porphyry Cu-Au-Mo deposit in southwestern Alaska. The Cretaceous Pebble deposit is concealed under tundra, glacial till, and Tertiary cover rocks, and is undisturbed except for numerous exploration drill holes. These USGS studies are part of a nation-wide research project on evaluating and detecting concealed mineral resources. This report focuses on exploration geochemistry and comprises illustrations and associated notes that were presented as a case study in a workshop on this topic. The workshop, organized by L.G. Closs and R. Glanzman, is called 'Geochemistry in Mineral Exploration and Development,' presented by the Society of Economic Geologists at a technical conference entitled 'The Challenge of Finding New Mineral Resources: Global Metallogeny, Integrative Exploration and New Discoveries,' held at Keystone, Colorado, October 2-5, 2010.

  6. The role of autophagy in chloroplast degradation and chlorophagy in immune defenses during Pst DC3000 (AvrRps4 infection.

    Directory of Open Access Journals (Sweden)

    Junjian Dong

    Full Text Available BACKGROUND: Chlorosis of leaf tissue normally observed during pathogen infection may result from the degradation of chloroplasts. There is a growing evidence to suggest that the chloroplast plays a significant role during pathogen infection. Although most degradation of the organelles and cellular structures in plants is mediated by autophagy, its role in chloroplast catabolism during pathogen infection is largely unknown. RESULTS: In this study, we investigated the function of autophagy in chloroplast degradation during avirulent Pst DC3000 (AvrRps4 infection. We examined the expression of defensive marker genes and suppression of bacterial growth using the electrolyte leakage assay in normal light (N and low light (L growing environments of wild-type and atg5-1 plants during pathogen treatment. Stroma-targeted GFP proteins (CT-GFP were observed with LysoTracker Red (LTR staining of autophagosome-like structures in the vacuole. The results showed that Arabidopsis expressed a significant number of small GFP-labeled bodies when infected with avirulent Pst DC3000 (AvrRps4. While barely detectable, there were small GFP-labeled bodies in plants with the CT-GFP expressing atg5-1 mutation. The results showed that chloroplast degradation depends on autophagy and this may play an important role in inhibiting pathogen growth. CONCLUSION: Autophagy plays a role in chloroplast degradation in Arabidopsis during avirulent Pst DC3000 (AvrRps4 infection. Autophagy dependent chloroplast degradation may be the primary source of reactive oxygen species (ROS as well as the pathogen-response signaling molecules that induce the defense response.

  7. Sistema infórmatico para análisis modal : Cálculo de la matriz A usando modelos de generadores, AVR y PSS

    OpenAIRE

    Biteznik, Carlos E.; Agüero, Jorge Luis; Beroqui, Mario César; Canalis, Ramiro; Barbero, Santiago

    2013-01-01

    En este trabajo se presentan la segunda etapa de desarrollo del Sistema Informatico para Análisis Modal (SIAM), en la cual se incorpora, a sus características ya presentadas, el cálculo de la matriz de estado A del sistema, basado en los datos de flujo y en los datos de los modelos linealizados de Generador, AVR y PSS. Asimismo, se realiza una comparación de resultados entre el SIAM y el PSS/E para un caso de referencia publicado.

  8. Magnaporthe oryzae Effector AVR-Pii Helps to Establish Compatibility by Inhibition of the Rice NADP-Malic Enzyme Resulting in Disruption of Oxidative Burst and Host Innate Immunity.

    Science.gov (United States)

    Singh, Raksha; Dangol, Sarmina; Chen, Yafei; Choi, Jihyun; Cho, Yoon-Seong; Lee, Jea-Eun; Choi, Mi-Ok; Jwa, Nam-Soo

    2016-05-31

    Plant disease resistance occurs as a hypersensitive response (HR) at the site of attempted pathogen invasion. This specific event is initiated in response to recognition of pathogen-associated molecular pattern (PAMP) and subsequent PAMP-triggered immunity (PTI) and effector-triggered immunity (ETI). Both PTI and ETI mechanisms are tightly connected with reactive oxygen species (ROS) production and disease resistance that involves distinct biphasic ROS production as one of its pivotal plant immune responses. This unique oxidative burst is strongly dependent on the resistant cultivars because a monophasic ROS burst is a hallmark of the susceptible cultivars. However, the cause of the differential ROS burst remains unknown. In the study here, we revealed the plausible underlying mechanism of the differential ROS burst through functional understanding of the Magnaporthe oryzae (M. oryzae) AVR effector, AVR-Pii. We performed yeast two-hybrid (Y2H) screening using AVR-Pii as bait and isolated rice NADP-malic enzyme2 (Os-NADP-ME2) as the rice target protein. To our surprise, deletion of the rice Os-NADP-ME2 gene in a resistant rice cultivar disrupted innate immunity against the rice blast fungus. Malic enzyme activity and inhibition studies demonstrated that AVR-Pii proteins specifically inhibit in vitro NADP-ME activity. Overall, we demonstrate that rice blast fungus, M. oryzae attenuates the host ROS burst via AVR-Pii-mediated inhibition of Os-NADP-ME2, which is indispensable in ROS metabolism for the innate immunity of rice. This characterization of the regulation of the host oxidative burst will help to elucidate how the products of AVR genes function associated with virulence of the pathogen. PMID:27126515

  9. 3.3 cm JVLA observations of transitional disks: searching for centimeter pebbles

    CERN Document Server

    Zapata, Luis A; Palau, Aina

    2016-01-01

    We present sensitive (rms-noises $\\sim$ 4 -- 25 $\\mu$Jy) and high angular resolution ($\\sim$1--2$"$) 8.9 GHz (3.3 cm) Karl G. Jansky Very Large Array (JVLA) radio continuum observations of 10 presumed transitional disks associated with young low-mass stars. We report the detection of radio continuum emission in 5 out of the 10 objects (RXJ1615, UX Tau A, LkCa15, RXJ1633, and SR24s). In the case of LkCa15, the centimeter emission is extended, and has a similar morphology to that of the transitional disk observed at mm wavelengths with an inner depression. For these five detections, we construct the Spectral Energy Distributions (SEDs) from the centimeter to submillimeter wavelengths, and find that they can be well fitted with a single (RXJ 1633 and UX Tau A) or a two component power-law (LkCa 15, RXJ 1615, and SR24s). For the cases where a single power-law fits well the data, the centimeter emission is likely produced by optically thin dust with large grains i.e. centimeter-size pebbles) present in the transit...

  10. Two-Step Diffusion Solutions to the IAEA CRP5 Pebble Box Benchmark Problem

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Hyun Chul; Qian, Hong; Kim, Kang Seog; Noh, Jae Man [Korea Atomic Energy Research Institute, Taejon (Korea, Republic of)

    2006-07-01

    Recently, the IAEA CRP-5 Pebble Box benchmark problem was proposed for a code-to-code comparison. To investigate the effect of the core/reflector spectral interaction and the effect of heterogeneity, the problem defines seven cases depending on the presence of a reflector and the level of heterogeneity. We presented a preliminary MCNP solution to this problem by using definitions of the problem in reference 3. In this study, the two-step diffusion solutions as well as the MCNP solutions to the problem by using the final specifications of the problem are presented. The results are compared with those from MCNP calculations. Since the problem size is very small when compared to that of a power reactor, a transverse leakage (TL) correction was needed for the infinite slab spectral geometry for the equivalent homogenization that was proposed for the analysis of large power reactors. Analysis results show that the errors can be reduced by using the transverse-leakage correction.

  11. Evidence of fast pebble growth near condensation fronts in the HL Tau protoplanetary disk

    CERN Document Server

    Zhang, Ke; Bergin, Edwin A

    2015-01-01

    Water and simple organic molecular ices dominate the mass of solid materials available for planetesimal and planet formation beyond the water snow line. Here we analyze ALMA long baseline 2.9, 1.3 and 0.87 mm continuum images of the young star HL Tau, and suggest that the emission dips observed are due to rapid pebble growth around the condensation fronts of abundant volatile species. Specifically, we show that the prominent innermost dip at 13 AU is spatially resolved in the 0.87 mm image, and its center radius is coincident with the expected mid-plane condensation front of water ice. In addition, two other prominent dips, at distances of 32 and 63 AU, cover the mid-plane condensation fronts of pure ammonia or ammonia hydrates and clathrate hydrates (especially with CO and N$_2$) formed from amorphous water ice. The spectral index map of HL Tau between 1.3 and 0.87 mm shows that the flux ratios inside the dips are statistically larger than those of nearby regions in the disk. This variation can be explained ...

  12. The orbital evolution of asteroids, pebbles and planets from giant branch stellar radiation and winds

    CERN Document Server

    Veras, Dimitri; Gaensicke, Boris T

    2015-01-01

    The discovery of over 50 planets around evolved stars and more than 35 debris discs orbiting white dwarfs highlight the increasing need to understand small body evolution around both early and asymptotic giant branch (GB) stars. Pebbles and asteroids are susceptible to strong accelerations from the intense luminosity and winds of GB stars. Here, we establish equations that can model time-varying GB stellar radiation, wind drag and mass loss. We derive the complete three-dimensional equations of motion in orbital elements due to (1) the Epstein and Stokes regimes of stellar wind drag, (2) Poynting-Robertson drag, and (3) the Yarkovsky drift with seasonal and diurnal components. We prove through averaging that the potential secular eccentricity and inclination excitation due to Yarkovsky drift can exceed that from Poynting-Robertson drag and radiation pressure by at least three orders of magnitude, possibly flinging asteroids which survive YORP spin-up into a widely dispersed cloud around the resulting white dw...

  13. Applying Pebble-Rotating Game to enhance the robustness of DHTs.

    Directory of Open Access Journals (Sweden)

    Liyong Ren

    Full Text Available Distributed hash tables (DHTs are usually used in the open networking environment, where they are vulnerable to Sybil attacks. Pebble-Rotating Game (PRG mixes the nodes of the honest and the adversarial randomly, and can resist the Sybil attack efficiently. However, the adversary may have some tricks to corrupt the rule of PRG. This paper proposes a set of mechanisms to make the rule of PRG be obliged to obey. A new joining node must ask the Certificate Authority (CA for its signature and certificate, which records the complete process on how a node joins the network and obtains the legitimacy of the node. Then, to prevent the adversary from accumulating identifiers, any node can make use of the latest certificate to judge whether one identifier is expired with the help of the replacement property of RPG. This paper analyzes in details the number of expired certificates which are needed to store in every node, and gives asymptotic solution of this problem. The analysis and simulations show that the mean number of the certificates stored in each node are [Formula: see text], where n is the size of the network.

  14. Applying Pebble-Rotating Game to enhance the robustness of DHTs.

    Science.gov (United States)

    Ren, Liyong; Nie, Xiaowen; Dong, Yuchi

    2013-01-01

    Distributed hash tables (DHTs) are usually used in the open networking environment, where they are vulnerable to Sybil attacks. Pebble-Rotating Game (PRG) mixes the nodes of the honest and the adversarial randomly, and can resist the Sybil attack efficiently. However, the adversary may have some tricks to corrupt the rule of PRG. This paper proposes a set of mechanisms to make the rule of PRG be obliged to obey. A new joining node must ask the Certificate Authority (CA) for its signature and certificate, which records the complete process on how a node joins the network and obtains the legitimacy of the node. Then, to prevent the adversary from accumulating identifiers, any node can make use of the latest certificate to judge whether one identifier is expired with the help of the replacement property of RPG. This paper analyzes in details the number of expired certificates which are needed to store in every node, and gives asymptotic solution of this problem. The analysis and simulations show that the mean number of the certificates stored in each node are [Formula: see text], where n is the size of the network. PMID:23776485

  15. Design of intelligent minimally invasive coagulation knife control system based on AVR microcontroller%基于 AVR 单片机的微创智能切凝刀系统的设计

    Institute of Scientific and Technical Information of China (English)

    尹婉; 叶兵; 张静雅; 余海东; 王立伟

    2015-01-01

    According to the development trend of minimally invasive surgery ,a portable minimally in‐vasive coagulation knife control system is designed .AVR microcontroller is selected as the core pro‐cessor ,and pulse width modulation(PWM ) control mode is used to complete the change of the average electric current of the electric wire so as to change the heat of the tip .This control method is different from the existing products which directly change the voltage of the electric wire ,and it is energy‐effi‐cient ,sensitive and precise .Finally ,the testing experiments on the developed system and the cutting test with minimally invasive knife are carried out .The result shows that the developed portable coagu‐lation knife works well while cutting tissue and closed blood vessels ,with the characteristics of no e‐lectric conduction ,little injury(average burn width of less than 1 mm) ,compact design ,strong porta‐bility and less smoke during surgery w hich makes clear vision .%文章根据微创手术的发展趋势,设计了一款便携式微创切凝刀控制系统。该系统选用AVR单片机作为微控制器,采用脉冲宽度调制(PWM )的控制方式,通过改变刀头电热丝通过的平均电流改变刀头的发热量。该控制方式相比于现有产品直接改变刀头电热丝电压的方式,具有节能、灵敏、精确的优点。对研制的系统进行了测试实验和用切凝刀实物进行了切割实验,结果表明研制的便携式切凝刀运行良好,具有电热传导损伤小(平均烫伤宽度小于1 mm)、设计精巧、便携性强、手术时烟雾少和视野清晰等优点。

  16. Bed bug deterrence

    Directory of Open Access Journals (Sweden)

    Haynes Kenneth F

    2010-09-01

    Full Text Available Abstract A recent study in BMC Biology has determined that the immature stage of the bed bug (the nymph signals its reproductive status to adult males using pheromones and thus avoids the trauma associated with copulation in this species. The success of this nymphal strategy of deterrence is instructive. Against the background of increasing problems with bed bugs, this research raises the question whether pheromones might be used to control them. See research article http://www.biomedcentral.com/1741-7007/8/121

  17. in Spouted Bed

    Directory of Open Access Journals (Sweden)

    Bronislaw Buczek

    2013-01-01

    Full Text Available Samples of active coke, fresh and spent after cleaning flue gases from communal waste incinerators, were investigated. The outer layers of both coke particles were separately removed by comminution in a spouted bed. The samples of both active cokes were analysed by means of densities, mercury porosimetry, and adsorption technique. Remaining cores were examined to determine the degree of consumption of coke by the sorption of hazardous emissions (SO2, HCl, and heavy metals through its bed. Differences in contamination levels within the porous structure of the particles were estimated. The study demonstrated the effectiveness of commercial active coke in the cleaning of flue gases.

  18. Efficient 13C/15N double labeling of the avirulence protein AVR4 in a methanol-utilizing strain (Mut+) of Pichia pastoris

    Energy Technology Data Exchange (ETDEWEB)

    Burg, Harrold A. van den [Wageningen University, Laboratory of Biochemistry (Netherlands); Wit, Pierre J.G.M. de [Wageningen University, Laboratory of Phytopathology (Netherlands); Vervoort, Jacques [Wageningen University, Laboratory of Biochemistry (Netherlands)

    2001-07-15

    Cost effective {sup 13}C/{sup 15}N-isotope labeling of the avirulence protein AVR4 (10 kDa) of the fungal tomato pathogen Cladosporium fulvum was achieved with the methylotrophic yeast Pichia pastoris in a fermentor. The {sup 13}C/{sup 15}N-labeled AVR4 protein accumulated to 30 mg/L within 48 h in an initial fermentation volume of only 300 mL, while prolonged optimized overexpressions yielded 126 mg/L. These protein yields were 24-fold higher in a fermentor than in flask cultures. In order to achieve these protein expression levels, we used the methanol-utilizing strain (Mut{sup +}) of Pichia pastoris which has a high growth rate while growing on methanol as the only carbon source. In contrast, the methanol-sensitive strain (Mut{sup S}) could intrinsically yield comparable protein expression levels, but at the expense of additional carbon sources. Although both strains are generally used for heterologous protein expression, we show that the costs for {sup 13}C-isotope labeling can be substantially reduced using the Mut{sup +} strain compared to the Mut{sup S} strain, as no {sup 13}C{sub 3}-glycerol is required during the methanol-induction phase. Finally, nitrogen limitations were precluded for {sup 15}N-labeling by an optimal supply of 10 g/L ({sup 15}NH{sub 4}){sub 2}SO{sub 4} every 24 h.

  19. Design of data acquisition system based on AVR microcontroller%基于AVR单片机的数据采集系统的设计

    Institute of Scientific and Technical Information of China (English)

    叶军

    2013-01-01

    介绍了基于AVR单片机的数据采集系统的硬件和软件设计。该系统分为数据采集传输和数据显示两部分。数据采集以ATMEGA328P为核心,利用该单片机进行多路数据采集。通过CH340T芯片的USB转串口的功能,实现AVR单片机与PC机间采集数据的传输。数据显示模块,通过Visual studio开发环境下的C#语言,运用.Net Framework提供的SerialPort类实现上位机采集数据的收集和显示。%The paper introduces the hardware design and the software design of a data acquisition system based on AVR Microcontroller. The whole system can be divided into data acquisition module and data display module. In data acquisition module, ATMEGA328P is used to collect data in multi-channels. In order to send the converted data to PC port, the communication between AVR microcontroller and pc is achieved by utilizing the serial port function of CH340T chip. In the data display module, data is collected by and displayed in Visual studio environment.

  20. Expression of RPS4 in tobacco induces an AvrRps4-independent HR that requires EDS1, SGT1 and HSP90.

    Science.gov (United States)

    Zhang, Yan; Dorey, Stephan; Swiderski, Michal; Jones, Jonathan D G

    2004-10-01

    The Arabidopsis RPS4 gene belongs to the Toll/interleukin-1 receptor/nucleotide-binding site/leucine-rich repeat (TIR-NB-LRR) class of plant resistance (R) genes. It confers resistance to Pseudomonas syringae carrying the avirulence gene avrRps4. Transient expression of genomic RPS4 driven by the 35S promoter in tobacco leaves induces an AvrRps4-independent hypersensitive response (HR). The same phenotype is seen after expression of a full-length RPS4 cDNA. This indicates that alternative splicing of RPS4 is not involved in this HR. The extent of HR is correlated with RPS4 protein levels. Deletion analyses of RPS4 domains show the TIR domain is required for the HR phenotype. Mutations in the P-loop motif of the NB domain abolish the HR. Using virus-induced gene silencing, we found that the cell death resulting from RPS4 expression is dependent on the three plant signalling components EDS1, SGT1 and HSP90. All these data suggest that heterologous expression of an R gene can result in activation of cell death even in the absence of its cognate avirulence product, and provides a system for studying the RPS4 domains required for HR.

  1. Maximum spoutable bed height of spout-fluid bed

    Energy Technology Data Exchange (ETDEWEB)

    Wenqi Zhong; Mingyao Zhang; Baosheng Jin [Southeast University, Nanjing (China). Key Laboratory on Clean Coal Power Generation and Combustion Technology of Ministry of Education

    2006-11-15

    Experimental study on the maximum spoutable bed height of a spout-fluid bed (cross-section of 0.3 m x 0.03 m and height of 2 m) packed with Geldart group D particles has been carried out. The effects of particle size, spout nozzle size and fluidizing gas flow rate on the maximum spoutable bed height were studied. Experimental data were compared to some published experiments and predictions. The results show that the maximum spoutable bed height of spout-fluid bed decreases with increasing particle size and spout nozzle size, which appears the same trend to that of spouted beds. The increasing of fluidizing gas flow rate leads to a sharply decrease in the maximum spoutable bed height. The existent correlations of the maximum spoutable bed height in the literature were observed to involve large discrepancies. Additionally, the flow characteristics when bed materials deeper than the maximum spoutable height were summarized. Under this condition, the spout-fluid bed operated without a stable and coherent spout or fountain assembles the characteristics of jetting fluidized bed. Besides, the mechanisms of spout termination were investigated. It was found that slugging in the spout and growth of instabilities would cause the spout termination in spout-fluid bed.

  2. The intracellular domain of Dumbfounded affects myoblast fusion efficiency and interacts with Rolling pebbles and Loner.

    Directory of Open Access Journals (Sweden)

    Sarada Bulchand

    Full Text Available Drosophila body wall muscles are multinucleated syncytia formed by successive fusions between a founder myoblast and several fusion competent myoblasts. Initial fusion gives rise to a bi/trinucleate precursor followed by more fusion cycles forming a mature muscle. This process requires the functions of various molecules including the transmembrane myoblast attractants Dumbfounded (Duf and its paralogue Roughest (Rst, a scaffold protein Rolling pebbles (Rols and a guanine nucleotide exchange factor Loner. Fusion completely fails in a duf, rst mutant, and is blocked at the bi/trinucleate stage in rols and loner single mutants. We analysed the transmembrane and intracellular domains of Duf, by mutating conserved putative signaling sites and serially deleting the intracellular domain. These were tested for their ability to translocate and interact with Rols and Loner and to rescue the fusion defect in duf, rst mutant embryos. Studying combinations of double mutants, further tested the function of Rols, Loner and other fusion molecules. Here we show that serial truncations of the Duf intracellular domain successively compromise its function to translocate and interact with Rols and Loner in addition to affecting myoblast fusion efficiency in embryos. Putative phosphorylation sites function additively while the extreme C terminus including a PDZ binding domain is dispensable for its function. We also show that fusion is completely blocked in a rols, loner double mutant and is compromised in other double mutants. These results suggest an additive function of the intracellular domain of Duf and an early function of Rols and Loner which is independent of Duf.

  3. Precambrian uranium-bearing quartz-pebble conglomerates: exploration model and United States resource potential

    International Nuclear Information System (INIS)

    Uranium has been discovered in fluvial quartz-pebble conglomerates in most of the Precambrian shield areas of the world, including the Canadian, African, South American, Indian, Baltic, and Australian shields. Occurrences in these and other areas are shown. Two of these occurrences, the Huronian supergroup of Canada and the Witwatersrand deposit of South Africa contain 20 to 30 percent of the planet's known uranium reserves. Thus it is critical that we understand the origin of these deposits and develop exploration models that can aid in finding new deposits. Inasmuch as these uranium-bearing conglomerates are confined almost entirely to rocks of Precambrian age, Part I of this review begins with a discussion of Precambrian geology as it applies to the conglomerates. This is followed by a discussion of genetic concepts, a discussion of unresolved problems, and finally a suggested exploration model. Part II summarizes known and potential occurrences of Precambrian fossil placers in the world and evaluates them in terms of the suggested exploration model. Part III discusses the potential for important Precambrian fossil-placer uranium deposits in the United States and includes suggestions that may be helpful in establishing an exploration program in this country. Part III also brings together new (1975-1978) data on uranium occurrences in the Precambrian of the Wyoming Province. Part IV is a complete bibliography of Precambrian fossil placers, divided according to geographical areas. In total, this paper is designed to be a comprehensive review of Precambrian uranium-bearing fossil placers which will be of use to uranium explorationists and to students of Precambrian geology

  4. Precambrian uranium-bearing quartz-pebble conglomerates: exploration model and United States resource potential

    Energy Technology Data Exchange (ETDEWEB)

    Houston, R.S.; Karlstrom, K.E.

    1979-11-01

    Uranium has been discovered in fluvial quartz-pebble conglomerates in most of the Precambrian shield areas of the world, including the Canadian, African, South American, Indian, Baltic, and Australian shields. Occurrences in these and other areas are shown. Two of these occurrences, the Huronian supergroup of Canada and the Witwatersrand deposit of South Africa contain 20 to 30 percent of the planet's known uranium reserves. Thus it is critical that we understand the origin of these deposits and develop exploration models that can aid in finding new deposits. Inasmuch as these uranium-bearing conglomerates are confined almost entirely to rocks of Precambrian age, Part I of this review begins with a discussion of Precambrian geology as it applies to the conglomerates. This is followed by a discussion of genetic concepts, a discussion of unresolved problems, and finally a suggested exploration model. Part II summarizes known and potential occurrences of Precambrian fossil placers in the world and evaluates them in terms of the suggested exploration model. Part III discusses the potential for important Precambrian fossil-placer uranium deposits in the United States and includes suggestions that may be helpful in establishing an exploration program in this country. Part III also brings together new (1975-1978) data on uranium occurrences in the Precambrian of the Wyoming Province. Part IV is a complete bibliography of Precambrian fossil placers, divided according to geographical areas. In total, this paper is designed to be a comprehensive review of Precambrian uranium-bearing fossil placers which will be of use to uranium explorationists and to students of Precambrian geology.

  5. WtsE, an AvrE-family effector protein from Pantoea stewartii subsp. stewartii, causes disease-associated cell death in corn and requires a chaperone protein for stability.

    Science.gov (United States)

    Ham, Jong Hyun; Majerczak, Doris R; Arroyo-Rodriguez, Angel S; Mackey, David M; Coplin, David L

    2006-10-01

    The pathogenicity of Pantoea stewartii subsp. stewartii to sweet corn and maize requires a Hrp type III secretion system. In this study, we genetically and functionally characterized a disease-specific (Dsp) effector locus, composed of wtsE and wtsF, that is adjacent to the hrp gene cluster. WtsE, a member of the AvrE family of effector proteins, was essential for pathogenesis on corn and was complemented by DspA/E from Erwinia amylovora. An intact C-terminus of WtsE, which contained a putative endoplasmic reticulum membrane retention signal, was important for function of WtsE. Delivery of WtsE into sweet corn leaves by an Escherichia coli strain carrying the hrp cluster of Erwinia chrysanthemi caused water-soaking and necrosis. WtsE-induced cell death was not inhibited by cycloheximide treatment, unlike the hypersensitive response caused by a known Avr protein, AvrRxol. WtsF, the putative chaperone of WtsE, was not required for secretion of WtsE from P. stewartii, and the virulence of wtsF mutants was reduced only at low inoculum concentrations. However, WtsF was required for full accumulation of WtsE within the bacteria at low temperatures. In contrast, WtsF was needed for efficient delivery of WtsE from E. coli via the Erwinia chrysanthemi Hrp system. PMID:17022173

  6. Getting Rid of Bed Bugs

    Science.gov (United States)

    ... how you select a company. Related Information Collaborative Strategy on Bed Bugs - highlights ways that all levels of government, community, academia and private industry can work together to reduce bed bugs across ...

  7. Comet formation in collapsing pebble clouds. What cometary bulk density implies for the cloud mass and dust-to-ice ratio

    CERN Document Server

    Lorek, S; Lacerda, P; Blum, J

    2016-01-01

    Comets are remnants of the icy planetesimals that formed beyond the ice line in the Solar Nebula. Growing from micrometre-sized dust and ice particles to km-sized objects is, however, difficult because of growth barriers and time scale constraints. The gravitational collapse of pebble clouds that formed through the streaming instability may provide a suitable mechanism for comet formation. We study the collisional compression of cm-sized porous ice/dust-mixed pebbles in collapsing pebble clouds. For this, we developed a collision model for pebbles consisting of a mixture of ice and dust, characterised by their dust-to-ice mass ratio. Using the final compression of the pebbles, we constrain combinations of initial cloud mass, initial pepple porosity, and dust-to-ice ratio that lead to cometesimals which are consistent with observed bulk properties of cometary nuclei. We find that observed high porosity and low density of ~0.5 g/cc of comet nuclei can only be explained if comets formed in clouds with mass appro...

  8. Geomechanics of bedded salt

    Energy Technology Data Exchange (ETDEWEB)

    Serata, S.; Milnor, S.W.

    1979-06-08

    Creep data from the literature search is reinterpreted by SGI, resulting in a better understanding of the temperature and stress state dependence of the octahedral creep rate and the octahedral shear strength. The concept of a transition strength between the elastic and the plastic states is in agreement with the data. The elastic and rheological properties of salt are described, and a set of constitutive equations is presented. The dependence of material properties on parameters such as temperature is considered. Findings on the permeability of salt are summarized, and the in-situ behavior of openings in bedded salt is described based on extensive engineering experience. A stress measuring system utilizing a finite element computer code is discussed. Geological factors affecting the stability of salt openings are considered, and the Stress Control Technique for designing stable openings in bedded salt formations is explained.

  9. Geomechanics of bedded salt

    International Nuclear Information System (INIS)

    Creep data from the literature search is reinterpreted by SGI, resulting in a better understanding of the temperature and stress state dependence of the octahedral creep rate and the octahedral shear strength. The concept of a transition strength between the elastic and the plastic states is in agreement with the data. The elastic and rheological properties of salt are described, and a set of constitutive equations is presented. The dependence of material properties on parameters such as temperature is considered. Findings on the permeability of salt are summarized, and the in-situ behavior of openings in bedded salt is described based on extensive engineering experience. A stress measuring system utilizing a finite element computer code is discussed. Geological factors affecting the stability of salt openings are considered, and the Stress Control Technique for designing stable openings in bedded salt formations is explained

  10. Design of Boiler Level Acquisition System with AVR Single-chip%AVR单片机锅炉液位采集系统设计

    Institute of Scientific and Technical Information of China (English)

    梅欣丽; 梅报春

    2012-01-01

    Efficient AVR single-chip ATMEGA8 is selected to design boiler level acquisition system.The system completes fluid position collection,two-color and LED data display modes,remote data uploading and many other features.System design has flexibility,high reliability and a wide functionality room for expansion.%选用高效的AVR单片机ATMEGA8,实现了锅炉液位采集系统功能.系统完成液位采集、双色和LED数码管数据显示、远程数据上传等多种任务.系统设计灵活、可靠性高,具有较宽的功能扩展空间.

  11. Atmel: новые возможности пакета avr Studio

    OpenAIRE

    Королев, Николай

    2011-01-01

    Программная среда разработки AVR Studio появилась практически одновременно с выходом AVR-микроконтроллеров и за время своего существования прошла большой путь. Первые версии пакета содержали текстовый редактор, ассемблер, компоновщик и симулятор. В качестве внешнего языка высокого уровня использовался коммерческий C-компилятор шведской компании IAR, впоследствии добавилась возможность подключать бесплатный компилятор GCC, версия WinAVR. К началу выпуска микроконтроллеров на ядре AVR32 был раз...

  12. Safeguards-by-Design: Guidance for High Temperature Gas Reactors (HTGRs) With Pebble Fuel

    Energy Technology Data Exchange (ETDEWEB)

    Philip Casey Durst; Mark Schanfein

    2012-08-01

    The following is a guidance document from a series prepared for the U.S. Department of Energy (DOE) National Nuclear Security Administration (NNSA), under the Next Generation Safeguards Initiative (NGSI), to assist facility designers and operators in implementing international Safeguards-by-Design (SBD). SBD has two main objectives: (1) to avoid costly and time consuming redesign work or retrofits of new nuclear fuel cycle facilities and (2) to make the implementation of international safeguards more effective and efficient at such facilities. In the long term, the attainment of these goals would save industry and the International Atomic Energy Agency (IAEA) time, money, and resources and be mutually beneficial. This particular safeguards guidance document focuses on pebble fuel high temperature gas reactors (HTGR). The purpose of the IAEA safeguards system is to provide credible assurance to the international community that nuclear material and other specified items are not diverted from peaceful nuclear uses. The safeguards system consists of the IAEA’s statutory authority to establish safeguards; safeguards rights and obligations in safeguards agreements and additional protocols; and technical measures implemented pursuant to those agreements. Of foremost importance is the international safeguards agreement between the country and the IAEA, concluded pursuant to the Treaty on the Non-Proliferation of Nuclear Weapons (NPT). According to a 1992 IAEA Board of Governors decision, countries must: notify the IAEA of a decision to construct a new nuclear facility as soon as such decision is taken; provide design information on such facilities as the designs develop; and provide detailed design information based on construction plans at least 180 days prior to the start of construction, and on "as-built" designs at least 180 days before the first receipt of nuclear material. Ultimately, the design information will be captured in an IAEA Design Information

  13. The presence of diverse IS elements and an avrPphD homologue that acts as a virulence factor on the pathogenicity plasmid of Erwinia herbicola pv. gypsophilae.

    Science.gov (United States)

    Guo, Ming; Manulis, Shulamit; Mor, Henia; Barash, Isaac

    2002-07-01

    The pathogenicity of Erwinia herbicola pv. gypsophilae (Ehg) and Erwinia herbicola pv. betae (Ehb) is dependent on a native plasmid (pPATH(Ehg) or pPATH(Ehb)) that harbors the hrp gene cluster, genes encoding type III effectors, phytohormones, biosynthetic genes, and several copies of IS1327. Sequence analysis of the hrp-flanking region in pPATH(Ehg) (cosmid pLA150) revealed a cluster of four additional IS elements designated as ISEhel, ISEhe2, ISEhe3, and ISEhe4. Two copies of another IS element (ISEhe5) were identified on the upstream region of the indole-3-acetic acid operon located on the same cosmid. Based on homology of amino acids and genetic organization, ISEhe1 belongs to the IS630 family, ISEhe2 to the IS5 family, ISEhe3 and ISEhe4 to different groups of the IS3 family, and ISEhe5 to the IS1 family. With the exception of ISEhe4, one to three copies of all the other IS elements were identified only in pathogenic strains of Erwinia herbicola pv. gypsophilae and Erwinia herbicola pv. betae whereas ISEhe4 was present in both pathogenic and nonpathogenic strains. An open reading frame that exhibited high identity (89% in amino acids) to AvrPphD of Pseudomonas syringae pv. phaseolicola was present within the cluster of IS elements. An insertional mutation in the AvrPphDEh, reduced gall size in gypsophila by approximately 85%. In addition, remnants of known genes from four different bacteria were detected on the same cosmid. PMID:12118887

  14. A pebbles accretion model with chemistry and implications for the solar system in the lights of Juno

    Science.gov (United States)

    Ali-Dib, Mohamad

    2016-10-01

    The chemical compositions of the solar system giant planets are a major source of informations on their origins. Since the measurements by the Galileo probe, multiple models have been put forward to try and explain the noble gases enrichment in Jupiter. The most discussed among these are its formation in the outer cold nebula and its formation in a partially photoevaporated disk. In this work I couple a pebbles accretion model to the disk's chemistry and photoevaporation in order to make predictions from both scenarios and compare them to the upcoming Juno measurements. The model include pebbles and gas accretion, type I and II migration, photoevaporation and chemical measurements from meteorites, comets and disks. Population synthesis simulations are used to explore the models free parameters (planets initial conditions), where then the results are narrowed down using the planets chemical, dynamical and core mass costraints. We end up with a population that fits all of the constrains. These are then used to predict the oxygen abundance and core mass in Jupiter, to be compared to results of Juno. Same calculations are also done for Saturn and Neptune for comparison. I will present the results from these simulations as well as the predictions from all of the different models.Ali-Dib, M. (2016ab, submitted to MNRAS)

  15. Thermal-Hydraulic System Study of the Helium Cooled Pebble Bed (HCPB) Test Blanket Module (TBM) for ITER Using System Code RELAP5

    Institute of Scientific and Technical Information of China (English)

    Jin Xuezhou; R. Meyder

    2005-01-01

    The HCPB concept has been a European DEMO reference concept for nearly one decade. Detailed thermal-hydraulic study on the control behavior of the whole system is one of the important parts of this development. The thermal-hydraulic effect of the TBM-combined cooling circuit during a cyclic operation in ITER has been studied using the system code RELAP5. The RELAP5 is based on an one-dimensional, transient two-fluid model for the flow of a two-phase steam-water mixture that can contain noncondensable components like Helium. The RELAP5-models are modified to take the cyclic operation of the circulator, heat exchanger, bypass, valves etc in to account. A sequence of operational phases is investigated, starting from the cold state through the heating phase that brings the system to a stand-by condition, followed by typical power cycles applied in ITER. The results show that the implemented control mechanisms keep the inlet temperature to the TBM and the total mass flow rate at the required values through all phases.

  16. Normal and Accidental Scenarios Analyses with MELCOR 1.8.2 and MELCOR 2.1 for the DEMO Helium-Cooled Pebble Bed Blanket Concept

    Directory of Open Access Journals (Sweden)

    Bruno Gonfiotti

    2015-01-01

    Full Text Available As for Light Water Reactors (LWRs, one of the most challenging accidents for the future DEMOnstration power plant is the Loss of Coolant Accident, which can trigger the pressurization of the confinement structures and components. Hence, careful analyses have to be executed to demonstrate that the confinement barriers are able to withstand the pressure peak within design limits and the residual cooling capabilities of the Primary Heat Transfer System are sufficient to remove the decay heat. To do so, severe accident codes, as MELCOR, can be employed. In detail, the MELCOR code has been developed to cope also with fusion reactors, but unfortunately, these fusion versions are based on the old 1.8.x source code. On the contrary, for LWRs, the newest 2.1.x versions are continuously updated. Thanks to the new features introduced in these latest 2.1.x versions, the main phenomena occurring in the helium-cooled blanket concepts of DEMO can be simulated in a basic manner. For this purpose, several analyses during normal and accidental DEMO conditions have been executed. The aim of these analyses is to compare the results obtained with MELCOR 1.8.2 and MELCOR 2.1 in order to highlight the differences among the results of the main thermal-hydraulic parameters.

  17. Bed Rest Muscular Atrophy

    Science.gov (United States)

    Greenleaf, John E.

    2000-01-01

    A major debilitating response from prolonged bed rest (BR) is muscle atrophy, defined as a "decrease in size of a part of tissue after full development has been attained: a wasting away of tissue as from disuse, old age, injury or disease". Part of the complicated mechanism for the dizziness, increased body instability, and exaggerated gait in patients who arise immediately after BR may be a result of not only foot pain, but also of muscular atrophy and associated reduction in lower limb strength. Also, there seems to be a close association between muscle atrophy and bone atrophy. A discussion of many facets of the total BR homeostatic syndrome has been published. The old adage that use determines form which promotes function of bone (Wolff's law) also applies to those people exposed to prolonged BR (without exercise training) in whom muscle atrophy is a consistent finding. An extreme case involved a 16-year-old boy who was ordered to bed by his mother in 1932: after 50 years in bed he had "a lily-white frame with limbs as thin as the legs of a ladder-back chair". These findings emphasize the close relationship between muscle atrophy and bone atrophy. In addition to loss of muscle mass during deconditioning, there is a significant loss of muscle strength and a decrease in protein synthesis. Because the decreases in force (strength) are proportionately greater than those in fiber size or muscle cross-sectional area, other contributory factors must be involved; muscle fiber dehydration may be important.

  18. Coal Bed Methane Primer

    Energy Technology Data Exchange (ETDEWEB)

    Dan Arthur; Bruce Langhus; Jon Seekins

    2005-05-25

    During the second half of the 1990's Coal Bed Methane (CBM) production increased dramatically nationwide to represent a significant new source of income and natural gas for many independent and established producers. Matching these soaring production rates during this period was a heightened public awareness of environmental concerns. These concerns left unexplained and under-addressed have created a significant growth in public involvement generating literally thousands of unfocused project comments for various regional NEPA efforts resulting in the delayed development of public and fee lands. The accelerating interest in CBM development coupled to the growth in public involvement has prompted the conceptualization of this project for the development of a CBM Primer. The Primer is designed to serve as a summary document, which introduces and encapsulates information pertinent to the development of Coal Bed Methane (CBM), including focused discussions of coal deposits, methane as a natural formed gas, split mineral estates, development techniques, operational issues, producing methods, applicable regulatory frameworks, land and resource management, mitigation measures, preparation of project plans, data availability, Indian Trust issues and relevant environmental technologies. An important aspect of gaining access to federal, state, tribal, or fee lands involves education of a broad array of stakeholders, including land and mineral owners, regulators, conservationists, tribal governments, special interest groups, and numerous others that could be impacted by the development of coal bed methane. Perhaps the most crucial aspect of successfully developing CBM resources is stakeholder education. Currently, an inconsistent picture of CBM exists. There is a significant lack of understanding on the parts of nearly all stakeholders, including industry, government, special interest groups, and land owners. It is envisioned the Primer would being used by a variety of

  19. The application of radioactive isotopes to the study of motion of silt and pebbles in the rivers and in the sea

    International Nuclear Information System (INIS)

    The application of radioactive tracers to the study of sediments drift has received considerable attention since 1954 in various countries. A comparative review is made of a number of techniques of labelling, immersing and detecting silts, sands, and pebbles. The influence of the burying of the active material is emphasized. The different experiments which have been so far carried out are described. (author)

  20. Variability of bed drag on cohesive beds under wave action

    Science.gov (United States)

    Safak, Ilgar

    2016-01-01

    Drag force at the bed acting on water flow is a major control on water circulation and sediment transport. Bed drag has been thoroughly studied in sandy waters, but less so in muddy coastal waters. The variation of bed drag on a muddy shelf is investigated here using field observations of currents, waves, and sediment concentration collected during moderate wind and wave events. To estimate bottom shear stress and the bed drag coefficient, an indirect empirical method of logarithmic fitting to current velocity profiles (log-law), a bottom boundary layer model for combined wave-current flow, and a direct method that uses turbulent fluctuations of velocity are used. The overestimation by the log-law is significantly reduced by taking turbulence suppression due to sediment-induced stratification into account. The best agreement between the model and the direct estimates is obtained by using a hydraulic roughness of 10  m in the model. Direct estimate of bed drag on the muddy bed is found to have a decreasing trend with increasing current speed, and is estimated to be around 0.0025 in conditions where wave-induced flow is relatively weak. Bed drag shows an increase (up to fourfold) with increasing wave energy. These findings can be used to test the bed drag parameterizations in hydrodynamic and sediment transport models and the skills of these models in predicting flows in muddy environments.

  1. Towards evidence-based emergency medicine: best BETs from the Manchester Royal Infirmary. BET 2: Is ST elevation in aVR a sure sign of left main coronary artery stenosis?

    Science.gov (United States)

    Morris, Niall; Body, Richard

    2016-01-01

    A shortcut review was carried out to establish whether ST elevation in aVR accurately identifies acute myocardial infarction caused by left main coronary artery stenosis. 141 unique papers were found in Medline, EMBASE, Cochrane Database of Systematic Reviews, ACP Journal Club and the Database of Abstracts of Reviews of Effects using the reported searches. Of these, 12 presented the best evidence to answer the clinical question. The author, date and country of publication, patient group studied, study type, relevant outcomes, results and study weaknesses of these best papers are tabulated. It is concluded that ST elevation in aVR can identify high-risk patients for early intensive investigation, particularly when found alongside widespread ST depression. It has insufficient utility to identify patients who require immediate revascularisation. PMID:26699191

  2. The Application of CH341 in Fulfilling the ISP Function of AVR Serial Single Microcontroller by Using USB Port%CH341在实现AVR单片机USB口ISP功能中的应用

    Institute of Scientific and Technical Information of China (English)

    马金祥; 关静

    2011-01-01

    ATMEL公司研发的AVR单片机提供一个同步串行通信接口SPI(Serial Peripheral Interface),用户能够通过计算机的并口、串口或USB口对其内部程序存储器编程。实际上,利用并口、串口或USB口实现AVR单片机ISP(In System Programmable)功能就是使用计算机的并口、串口或USB口来驱动AVR单片机ISP串行编程所需的时序信号,从而实现计算机对AVR单片机的编程。文章介绍了USB总线转接芯片CH341的引脚功能和工作原理,讨论了基于USB口的AVR单片机ISP编程电缆原理图及相关编程工具软件的使用。%The Single Microcontroller in AVR Series issued by ATMEL provides a Serial Peripheral Interface(SPI),with which clients are able to do programming through computer parallel port,serial port or USB port to its internal program memory.In fact,to fulfill the function of In System Programmable(ISP) in AVR single microcontroller by using computer port is to force signal wave needed by the single microcontroller,achieving the AVR single microcontroller programmed by computer.With an introduction of the pins function and the principle of the USB transfer chip CH341,this paper discusses ISP programming cable principle map of AVR single microcontroller based on USB port and introduces the usage of relevant programming software.

  3. LSP Composite Test Bed Design

    Science.gov (United States)

    Day, Arthur C.; Griess, Kenneth H.

    2013-01-01

    This document provides standalone information for the Lightning Strike Protection (LSP) Composite Substrate Test Bed Design. A six-sheet drawing set is reproduced for reference, as is some additional descriptive information on suitable sensors and use of the test bed.

  4. The German Brown Boveri, a center of the company's nuclear activities

    International Nuclear Information System (INIS)

    The main activity of the German Brown Boveri Comp. is the pebble-bed reactor system. The experimental power unit AVR-15 went into operation in 1967 and has been demonstrating for the last 20 years the excellent behaviour of a helium-cooled pebble-bed reactor (15 MWe). The 300 MWe Thorium High Temperature Reactor (THTR-300) has been in full operation since September 1986. The follow-up projects HTR-500 (550 MWe) and HTR-100 (100 MWe) are under development. The Gas-Cooled Heating Reactor of 10 MW thermal power (GHR-10th) is under evaluation in Switzerland together with two other concepts of small heating reactors. LWR systems were also taken up by Brown Boveri in the mid sixties when BBC, as an experienced supplier of turbine generators and electrical and control equipment, formed partnerships with experienced reactor suppliers for example, Westinghouse and General Electric, to deliver turnkey nuclear power plants

  5. 基于AVR单片机的智能家居监控系统%The Intelligent Household Monitoring System Based on AVR MCU

    Institute of Scientific and Technical Information of China (English)

    孔壮

    2013-01-01

      Intelligent household is a kind of living environment for people, it uses advanced network communication technology, embedded technology to meet the needs of people. Compared with ordinary household it transfers original stationary structure into active intelligent structure tool, so as to provide a full range of information exchange function, to help families keep communication smoothly with external environment. AVR MCU is commonly used unit used for sensor data acquisition and the control of actuator, having advantages of easy to use and good reliability. In view of the traditional intelligent household security system featuring single function, low intelligence, high error rate, and being unable to realize remote alarm function. Therefore, the system uses AVR microcontroller Atmega128L processor, together with the door magnetic sensor and infrared sensor to realize security monitoring, and uses CO sensor to realize gas security function. Furthermore the system adopts message form to make users real-time understanding of household security situation.%  智能家居是人们的一种居住环境,利用先进的网络通信技术,嵌入式技术以满足人们的需要,与普通家居相比由原来静止的结构转化为具有能动智能的结构工具,提供全方位的信息交换功能,帮助家庭与外部保持信息交流畅通。AVR单片机对于常用传感器的数据采集和执行器的控制,易用性和可靠性俱佳。鉴于传统的智能家居安防系统功能单一、智能化低下、误报率高,而且不能够实现远程报警的功能。因此,本系统采用AVR单片机Atmega128L处理器,通过门磁传感器并配有红外传感器实现防盗监测以及利用CO传感器实现煤气安全保障的功能。并且通过短信形式使用户实时的了解家居安防情况。

  6. Wall-to-bed heat transfer in circulating fluidized beds

    Energy Technology Data Exchange (ETDEWEB)

    Fox, W.B.; Grewal, N.S.; Moen, D.A. [Univ. of North Dakota, Grand Forks, ND (United States). Mechanical Engineering Dept.

    1999-05-01

    Circulating fluidized beds (CFBs) have become increasingly important in recent years for coal combustion and gas-solid reactions. Here, heat transfer from the wall of a circulating fluidized bed to the fast bed suspension has been investigated for several materials. The range of investigation includes dense and dilute phase fast fluidization and pneumatic transport. The overall heat transfer coefficient was found to be a function mainly of cross-sectional average suspension density. Effects of superficial velocity and solids mass flux were obscured by their interrelationship to the suspension density. Two models from the literature are evaluated using present and published data.

  7. HCLL and HCPB coolant purification system: Design of the copper oxide bed

    Energy Technology Data Exchange (ETDEWEB)

    Liger, K., E-mail: karine.liger@cea.fr [CEA, DEN, Cadarache DTN/STPA/LIPC, F-13108 Saint-Paul-lez-Durance (France); European TBM Consortium of Associates (Country Unknown); Lefebvre, X. [CEA, DEN, Cadarache DTN/STPA/LIPC, F-13108 Saint-Paul-lez-Durance (France); European TBM Consortium of Associates (Country Unknown); Ciampichetti, A.; Aiello, A. [ENEA CR Brasimone, 40032 Camugnano (Italy); European TBM Consortium of Associatesm (Country Unknown); Ricapito, I. [Fusion for Energy, 08019 Barcelona (Spain)

    2011-10-15

    The coolant purification system (CPS) together with the tritium extraction system (TES) and helium cooling system (HCS) are the principal auxiliary circuits of helium-cooled-lithium-lead (HCLL) and helium-cooled-pebble-bed (HCPB) test blanket modules (TBMs). To extract heat from TBMs, Helium is used as primary coolant. CPS is used to extract tritium from the helium primary circuit as well as to guarantee removal of impurities which could interact with structural material. The reference process proposed for CPS is composed of 3 main successive steps. Step 1 consists in oxidation of Q{sub 2} and CO to Q{sub 2}O and CO{sub 2} using a copper oxide bed (Q represents either: H, D or T). Step 2 is dedicated to the removal of water which is adsorbed together with CO{sub 2} on molecular sieve bed. Step 3 will remove residual impurities using a heated getter. Based on the operating conditions of CPS (pressure, flowrate, temperature) and on an estimation of the impurities foreseen, this paper presents a design of the oxidising bed which fulfils all requirements in terms of efficiency and lifespan. The design is obtained using a phenomenological approach taking into account competition between oxidation of CO and Q{sub 2} on the metal oxide. The model was implemented in matlab software. A column of 0.41 m large and 2 m long containing 480 kg of CuO is proposed to assure complete oxidation of Q{sub 2} for 16 months long.

  8. Pulling a patient up in bed

    Science.gov (United States)

    Moving a patient in bed ... You must move or pull someone up in bed the right way to avoid injuring the patient's ... people to safely move a patient up in bed. Friction from rubbing can scrape or tear the ...

  9. Automatizované programování více mikrokontrolérů AVR přes SPI sběrnici

    OpenAIRE

    Boštík, Jiří

    2014-01-01

    Cílem této práce je sestavit obvod pro automatizované programování více mikrokontrolérů Atmel AVR přes SPI sběrnici a navrhnout a realizovat demonstrační přípravek, který bude schopen tento úkol alespoň částečně automatizovat, tedy ideálně bez lidského zásahu jedním programátorem nahrát firmware do více mikrokontrolérů. V teoretické části budou popsány součástky, které se v práci využívají, bude popsána jejich funkce a využitelnost. Pro přepínání mezi mikrokontroléry a tudíž i vyřešení dané p...

  10. Multifunctional Resistance Welding Controller Based on AVR Single Chip Microcomputer%基于AVR单片机的多功能阻焊控制器

    Institute of Scientific and Technical Information of China (English)

    张秀峰; 管功湖; 李祥; 黄晓明; 黄珍锡

    2012-01-01

    According to the control principle of the resistance welding, a multifunctional resistance welding controller using the AVR single chip microcomputer was developed. The main functions of epol welding and seam welding were implied through the design of the hardware circuit and software program, so as to precise control of the welding current and time. The power supply voltage automatic compensation was applied to improve the quality of welding. The multifunctional resistance welding controller was easy to use,and the operation was stable and reliable. It had the functions of automatic fault alarm and single SCR switching on protection.%根据阻焊控制原理,研制以AVR单片机为核心的多功能阻焊控制器.通过软硬件设计,主要实现了点焊、缝焊等焊接功能,做到对焊接时间和焊接电流进行精确控制,同时采取网压自动补偿的措施,以提高焊接质量.多功能阻焊控制器使用方便,运行稳定可靠,具备故障自动报警、单管导通保护等功能.

  11. Torsion testing of bed joints

    DEFF Research Database (Denmark)

    Hansen, Klavs Feilberg; Pedersen, Carsten Mørk

    2008-01-01

    This paper describes a simple test method for determining the torsion strength of a single bed joint between two bricks and presents results from testing using this test method. The setup for the torsion test is well defined, require minimal preparation of the test specimen and the test can...... be carried out directly in a normal testing machine. The torsion strength is believed to be the most important parameter in out-of-plane resistance of masonry walls subjected to bending about an axis perpendicular to the bed joints. The paper also contains a few test results from bending of small walls about...... an axis perpendicular to the bed joints, which indicate the close connection between these results and results from torsion tests. These characteristics make the torsion strength well suited to act as substitute parameter for the bending strength of masonry about an axis perpendicular to the bed joints....

  12. Sea bed mapping and inspection

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2006-07-01

    The conference has 24 presentations on the topics: Sea bed mapping, inspection, positioning, hydrography, marine archaeology, remote operation vehicles and computerized simulation technologies, oil field activities and plans, technological experiences and problems. (tk)

  13. Bed Bugs: The Australian Response

    Directory of Open Access Journals (Sweden)

    Richard C. Russell

    2011-04-01

    Full Text Available Australia has experienced a sudden and unexpected resurgence in bed bug infestations from both Cimex lectularius L. and Cimex hemipterus F. A survey in 2006 revealed that infestations had increased across the nation by an average of 4,500% since the start of the decade. In response, a multi-disciplinary approach to combat the rise of this public health pest was implemented and involved the coordinated efforts of several organizations. The key components of the strategy included the introduction of a pest management standard ‘A Code of Practice for the Control of Bed Bug Infestations in Australia’ that defines and promotes ‘best practice’ in bed bug eradication, the development of a policy and procedural guide for accommodation providers, education of stakeholders in best management practices, and research. These strategies continue to evolve with developments that lead to improvements in ‘best practice’ while bed bugs remain problematic in Australia.

  14. Better backs by better beds?

    DEFF Research Database (Denmark)

    Bergholdt, Kim; Fabricius, Rasmus N; Bendix, Tom

    2008-01-01

    using the probably most relevant "worst case" data. There were no relevant difference between the effects of the water bed and the foam bed. CONCLUSION: The Waterbed and foam mattress' did influence back symptoms, function and sleep more positively as apposed to the hard mattress, but the differences...... mattresses have a positive effect on LBP, and especially a hard mattress is commonly believed to have a positive effect. METHODS: One hundred sixty CLBP patients were randomized to 1 of 3 groups, having a mattress/bed mounted in their sleeping room for 1 month. The beds were: (1) waterbed (Akva), (2) body......-conforming foam mattress (Tempur), and (3) a hard mattress (Innovation Futon). At baseline and after 4 weeks, a blinded observer interviewed the patients on LBP levels (0-10), daily function (activities of daily living, 0-30), and on the amount of sleeping hours/night. RESULTS: Because of dropout of 19 patients...

  15. The Siemens-Argonaut reactor as a driver zone for a high-temperature reactor cell. Der Siemens-Argonaut-Reaktor als Treiberzone fuer eine Hochtemperaturreaktorzelle

    Energy Technology Data Exchange (ETDEWEB)

    Mueller, H.; Schuerrer, F.; Ninaus, W.; Oswald, K.; Rabitsch, H.; Kreiner, H. (Technische Univ., Graz (Austria). Inst. fuer Theoretische Physik und Reaktorphysik); Neef, R.D. (Kernforschungsanlage Juelich G.m.b.H. (Germany, F.R.). Inst. fuer Reaktorentwicklung)

    1984-12-15

    To enable a validation of neutron physics calculation methods for pebble bed reactors the inner reflector of an Argonaut research reactor was substituted by a full of about 1200 fuel elements of the AVR-Juelich type. The report describes the measuring instruments and the reactor physical layout of the arrangement by the code packages GAMTEREX, ZUT-D.G.L. and MUPO. Comparison of calculated reaction rates with measurements show good agreement. Application of the codes to high-temperature reactors in abnormal states is envisaged. (Author, translated by G.Q.)

  16. Bed-exit alarm effectiveness

    Science.gov (United States)

    Capezuti, Elizabeth; Brush, Barbara L.; Lane, Stephen; Rabinowitz, Hannah U.; Secic, Michelle

    2009-01-01

    This study describes the accuracy of two types of bed-exit alarms to detect bed-exiting body movements: pressure-sensitive and a pressure sensitive combined with infrared beam detectors (dual sensor system). We also evaluated the occurrence of nuisance alarms, or alarms that are activated when a participant does not attempt to get out of bed. Fourteen nursing home residents were directly observed for a total of 256 nights or 1,636.5 hours; an average of 18.3 ± 22.3 (± S.D.) nights/participant for an average of 6.4 ± 1.2 hours/night. After adjusting for body movements via repeated measures, Poisson regression modeling, the least squares adjusted means show a marginally significant difference between the type of alarm groups on the number of true positives (mean/S.E.M. = 0.086/1.617) for pressure-sensitive vs. dual sensor alarm (0.593/1.238; p = 0.0599) indicating that the dual sensor alarm may have a higher number of true positives. While the dual sensor bed-exit alarm was more accurate than the pressure sensitive alarm in identifying bed-exiting body movements and reducing the incidence of false alarms, false alarms were not eliminated altogether. Alarms are not a substitute for staff; adequate staff availability is still necessary when residents need or wish to exit bed. PMID:18508138

  17. Northern European Satellite Test Bed

    Science.gov (United States)

    Schuster-Bruce, Alan; Lawson, James; Quinlan, Michael; McGregor, Andrew

    Satellite Based Augmentation Systems are being developed in Europe (EGNOS), the USA (WAAS), and in Japan (MSAS). As part of their support to EGNOS, NATS and Racal have developed and deployed a prototype SBAS system called the Northern European Satellite Test Bed (NEST Bed). NEST Bed uses GPS L1/L2 reference stations at: Aberdeen, Rotterdam, Ankara, Cadiz, Keflavik, and Bronnoysund. Data is sent to the Master Control Centre at NATS Gatwick Services Management Centre for processing. The resulting 250 bits-per-second message is sent to Goonhilly for up-linking by BT to the Navigation Payload of either the Inmarsat AOR-E or F5 spare satellite. NEST Bed was deployed and commissioned during summer 1998, and flight tests were successfully demonstrated at the September 1998 Farnborough Air Show where approaches were flown to Boscombe Down on the DERA BAC1-11 aircraft. In October 1998, a NATS/FAA flight trial was held in Iceland involving NEST Bed and the FAA NSTB. NEST Bed is also being used for SARPS validation.

  18. Pb-Sr-Nd isotopes in surficial materials at the Pebble Porphyry Cu-Au-Mo Deposit, Southwestern Alaska: can the mineralizing fingerprint be detected through cover?

    Science.gov (United States)

    Ayuso, Robert A.; Kelley, Karen D.; Eppinger, Robert G.; Forni, Francesca

    2013-01-01

    The Cretaceous Pebble porphyry Cu-Au-Mo deposit is covered by tundra and glacigenic sediments. Pb-Sr-Nd measurements were done on sediments and soils to establish baseline conditions prior to the onset of mining operations and contribute to the development of exploration methods for concealed base metal deposits of this type. Pebble rocks have a moderate range for 206Pb/204Pb = 18.574 to 18.874, 207Pb/204Pb = 15.484 to 15.526, and 208,Pb/204Pb = 38.053 to 38.266. Mineralized granodiorite shows a modest spread in 87Sr/86Sr (0.704354–0.707621) and 143Nd/144Nd (0.512639–0.512750). Age-corrected (89 Ma) values for the granodiorite yield relatively unradiogenic Pb (e.g., 207Pb/204Pb 87Sr/86Sr, and positive values of ɛNd (1.00–4.52) that attest to a major contribution of mantle-derived source rocks. Pond sediments and soils have similar Pb isotope signatures and 87Sr/86Sr and 143Nd/144Nd values that resemble the mineralized granodiorites. Glacial events have obscured the recognition of isotope signatures of mineralized rocks in the sediments and soils. Baseline radiogenic isotope compositions, prior to the onset of mining operations, reflect natural erosion, transport and deposition of heterogeneous till sheets that included debris from barren rocks, mineralized granodiorite and sulfides from the Pebble deposit, and other country rocks that pre- and postdate the mineralization events. Isotopic variations suggest that natural weathering of the deposit is generally reflected in these surficial materials. The isotope data provide geochemical constraints to glimpse through the extensive cover and together with other geochemical observations provide a vector to concealed mineralized rocks genetically linked with the Pebble deposit.

  19. Contingency table analysis of pebble lithology and roundness: A case study of Huangshui River, China and comparison to rivers in the Rocky Mountains, USA

    Science.gov (United States)

    Miao, X.; Lindsey, D.A.; Lai, Z.; Liu, Xiuying

    2010-01-01

    Contingency table analysis of pebble lithology and roundness is an effective way to identify the source terrane of a drainage basin and to distinguish changes in basin size, piracy, tectonism, and other events. First, the analysis to terrace gravel deposited by the Huangshui River, northeastern Tibet Plateau, China, shows statistically contrasting pebble populations for the oldest terrace (T7, Dadongling, 1.2. Ma) and the youngest terraces (T0-T3, ?. 0.15. Ma). Two fluvial processes are considered to explain the contrast in correlation between lithology and roundness in T7 gravel versus T0-T3 gravel: 1) reworking of T7 gravel into T0-T3 gravel and 2) growth in the size of the river basin between T7 and T0-T3 times. We favor growth in basin size as the dominant process, from comparison of pebble counts and contingency tables. Second, comparison of results from Huangshui River of China to three piedmont streams of the Rocky Mountains, USA highlights major differences in source terrane and history. Like Rocky Mountain piedmont gravel from Colorado examples, the Huangshui gravels show a preference (observed versus expected frequency) for rounded granite. But unlike Rocky Mountain gravel, Huangshui gravel shows a preference for angular quartzite and for rounded sandstone. In conclusion, contrasting behavior of lithologies during transport, not always apparent in raw pebble counts, is readily analyzed using contingency tables to identify the provenance of individual lithologies, including recycled clasts. Results of the analysis may help unravel river history, including changes in basin size and lithology. ?? 2009.

  20. 49 CFR 236.336 - Locking bed.

    Science.gov (United States)

    2010-10-01

    ... 49 Transportation 4 2010-10-01 2010-10-01 false Locking bed. 236.336 Section 236.336 Transportation Other Regulations Relating to Transportation (Continued) FEDERAL RAILROAD ADMINISTRATION... Instructions § 236.336 Locking bed. The various parts of the locking bed, locking bed supports, and tappet...

  1. Annular core liquid-salt cooled reactor with multiple fuel and blanket zones

    Science.gov (United States)

    Peterson, Per F.

    2013-05-14

    A liquid fluoride salt cooled, high temperature reactor having a reactor vessel with a pebble-bed reactor core. The reactor core comprises a pebble injection inlet located at a bottom end of the reactor core and a pebble defueling outlet located at a top end of the reactor core, an inner reflector, outer reflector, and an annular pebble-bed region disposed in between the inner reflector and outer reflector. The annular pebble-bed region comprises an annular channel configured for receiving pebble fuel at the pebble injection inlet, the pebble fuel comprising a combination of seed and blanket pebbles having a density lower than the coolant such that the pebbles have positive buoyancy and migrate upward in said annular pebble-bed region toward the defueling outlet. The annular pebble-bed region comprises alternating radial layers of seed pebbles and blanket pebbles.

  2. Particle motion in fluidised beds

    International Nuclear Information System (INIS)

    Gas fluidised beds are important components in many process industries, e.g. coal combustors and granulators, but not much is known about the movement of the solids. Positron Emission Particle Tracking (PEPT) enables the movement of a single, radioactive tracer particle to be followed rapidly and faithfully. Experiments were carried out in columns sized between 70 and 240mm. diameter, operating in the bubbling regime at ambient process conditions using particles of group B and D (Geldart Classification). Particle motion was tracked and the data applied to models for particle movement at the gas distributor as well as close to other surfaces and to models for particle circulation in beds of cohesive particles. In the light of these data, models for particle and bubble interaction, particle circulation, segregation, attrition, erosion, heat transfer and fluidised bed scale-up rules were reassessed. Particle motion is directly caused by bubble motion, and their velocities were found to be equal for particles travelling in a bubble. PEPT enables particle circulation to be measured, giving a more accurate correlation for future predictions. Particle motion follows the scale-up rules based on similarities of the bubble motion in the bed. A new group of parameters was identified controlling the amount of attrition in fluidised beds and a new model to predict attrition is proposed. (author)

  3. Pebble and rock band: heuristic resolution of repeats and scaffolding in the velvet short-read de novo assembler.

    Directory of Open Access Journals (Sweden)

    Daniel R Zerbino

    Full Text Available BACKGROUND: Despite the short length of their reads, micro-read sequencing technologies have shown their usefulness for de novo sequencing. However, especially in eukaryotic genomes, complex repeat patterns are an obstacle to large assemblies. PRINCIPAL FINDINGS: We present a novel heuristic algorithm, Pebble, which uses paired-end read information to resolve repeats and scaffold contigs to produce large-scale assemblies. In simulations, we can achieve weighted median scaffold lengths (N50 of above 1 Mbp in Bacteria and above 100 kbp in more complex organisms. Using real datasets we obtained a 96 kbp N50 in Pseudomonas syringae and a unique 147 kbp scaffold of a ferret BAC clone. We also present an efficient algorithm called Rock Band for the resolution of repeats in the case of mixed length assemblies, where different sequencing platforms are combined to obtain a cost-effective assembly. CONCLUSIONS: These algorithms extend the utility of short read only assemblies into large complex genomes. They have been implemented and made available within the open-source Velvet short-read de novo assembler.

  4. A comprehensive study of noble gases and nitrogen in Hypatia, a diamond-rich pebble from SW Egypt

    CERN Document Server

    Avice, Guillaume; Marty, Bernard; Wieler, Rainer; Kramers, Jan D; Langenhorst, Falko; Cartigny, Pierre; Maden, Colin; Zimmermann, Laurent; Andreoli, Marco A G

    2015-01-01

    This is a follow-up study of a work by Kramers et al. (2013) on an unusual diamond-rich rock found in the SW side of the Libyan Desert Glass strewn field. This pebble, called Hypatia, is composed of almost pure carbon. Transmission Electron Microscopy and X-ray diffraction results reveal that Hypatia is made of defect-rich diamond containing lonsdaleite and deformation bands. These characteristics are compatible with an impact origin on Earth and/or in space. We analyzed concentrations and isotopic compositions of all five noble gases and nitrogen in several mg sized Hypatia samples. These data confirm that Hypatia is extra-terrestrial. The sample is rich in trapped noble gases with an isotopic composition close to the meteoritic Q component. 40Ar/36Ar ratios in individual steps are as low as 0.4. Concentrations of cosmic-ray produced 21Ne correspond to a nominal cosmic-ray exposure age of ca. 0.1 Myr if produced in a typical m-sized meteoroid. Such an atypically low nominal exposure age suggests high shieldi...

  5. 基于AVR单片机的汽车尾气检测系统设计%Design of automobile exhaust gas detection system based on AVR

    Institute of Scientific and Technical Information of China (English)

    姚宁; 郭朝龙; 翁凌云; 葛承滨

    2014-01-01

    针对当前汽车尾气污染加重和检测标准日益完善的现状,为了弥补传统汽车尾气检测系统在测量精度、稳定性、人机操作等方面存在的不足,提出了一种基于AVR单片机的汽车尾气检测系统设计方案。系统以ATMEGA8L为核心控制器,主要由传感器模块、信号采集调理电路、A/D转换器以及显示模块等组成。实验结果表明,系统具有测量精度高、稳定可靠、人机交互性好等优点。%Nowadays the automotive exhaust pollution has been increasing and the detecting standard is increasingly sophis⁃ticated. A design scheme of an automobile exhaust detecting system based on AVR is proposed to overcome the shortage of tradi⁃tional automotive exhaust detection systems in measuring accuracy,stability and man⁃machine operation. ATMEGA8L is taken as the core controller of the system,which is composed of the sensor module,signal acquisition and conditioning circuit,A/D converter,and display module. The tested results show that the system has the advantages of high⁃accuracy,high stability,high reliability and good human⁃computer interaction.

  6. DESIGN OF TEST INSTRUMENT TO DIGITAL CONTROLLER BASED ON AVR%基于AVR的数字控制器测试仪的设计

    Institute of Scientific and Technical Information of China (English)

    刘忠超; 郭抒颖

    2015-01-01

    数字控制器响应快、稳定性好,但是算法复杂. 本文以AVR单片机为控制核心,以ADC0809为模数转换器、TLC7528为数模转换器,设计了数字控制器测试仪的硬件系统. 并以最小拍为控制目的,设计了其算法程序;为了直观显示控制效果,通过LabWindows/CVI软件编程,实现了将控制器输出通过RS-232送到上位机进行波形显示比较的功能. 最后给出了数字控制器测试仪的实际测试效果,证明了该测试系统设计的正确性和可靠性,为数字控制器理论设计提供了一种新的测试验证方案.%The digital controller has quick response, good stability, but the algorithm is complex. The topic uses the AVR single chip microcomputer as control core, using ADC0809 as the ADC, TLC7528 as the digital to analog converter, to design the hardware system of digital controller tester. And with the minimum step as the control objective, the topic designs the algorithm procedure;in order to display the control visually, through the LabWindows/CVI software programming, this paper realized the output of controller through RS-232 sent to the host computer for display waveform comparison function. Finally, the actual test effect of digital controller tester is given, which proves the correctness and reliability of the test system design, and provides a new testing scheme for digital controller de-sign theory.

  7. Powered wheelchair controller based on AVR microcontroller%基于AVR单片机的电动代步车控制器

    Institute of Scientific and Technical Information of China (English)

    盛卫锋; 徐凯

    2011-01-01

    In this paper, a new design plan of powered wheelchair controller with high performance and low cost is presented. The controller is based on Atmel Corporation's AVR microcontroller. The driver of DC motor is H bridge circuit. By using joystick, the user can control the speed and direction of powered wheelchair. The software is consisted of three parts, self-check, joystick detection and motor running. To insure the safty and stability of the system, some useful programming methods are used, such as time mark, event trigger mechanism, and finite-state machine. The application indicates that this system can realize multi-fault diagnosis, the motors run smoothly, joystick is operated flexiblely, which can meet the requirements of actual utilities.%提出一种高性能低成本的电动代步车控制器设计方案.该控制器以Atmel公司的AVR单片机为控制核心,H桥电路作为直流电机驱动器,使用者通过摇杆操控电动代步车的速度和转向.控制器的软件部分由系统自检、摇杆位置检测和电机运动3大部分组成,并灵活使用系统时标,事件触发机制和有限状态机等编程新方法,以确保系统的安全性和稳定性.实践表明,该电动代步车控制器能够实现多种故障诊断功能,电机启动和停止时运行平稳,摇杆操作灵活,系统整体性能良好,能够满足实际使用要求.

  8. Redundancy among phospholipase D isoforms in resistance triggered by recognition of the Pseudomonas syringae effector AvrRpm1 in Arabidopsis thaliana

    Directory of Open Access Journals (Sweden)

    Oskar N Johansson

    2014-11-01

    Full Text Available Plants possess a highly sophisticated system for defense against microorganisms. So called MAMP (Microbe Associated Molecular Patterns triggered immunity (MTI prevents the majority of non-adapted pathogens from causing disease. Adapted plant pathogens use secreted effector proteins to interfere with such signaling. Recognition of microbial effectors or their activity by plant resistance (R-proteins triggers a second line of defense resulting in effector triggered immunity (ETI. The latter usually comprises the hypersensitive response (HR which includes programmed cell death at the site of infection. Phospholipase D (PLD mediated production of phosphatidic acid (PA has been linked to both MTI and ETI in plants. Inhibition of PLD activity has been shown to attenuate MTI as well as ETI. In this study, we systematically tested single and double knockouts in all 12 genes encoding PLDs in Arabidopsis thaliana for effects on ETI and MTI. No single PLD could be linked to ETI triggered by recognition of effectors secreted by the bacterium Pseudomonas syringae. However, repression of PLD dependent PA production by n-butanol strongly inhibited the HR following P. syringae effector recognition. In addition some pld mutants were more sensitive to n-butanol than wild type. Thus, the effect of mutations of PLDs could become detectable, and the corresponding genes can be proposed to be involved in the HR. Only knockout of PLDδ caused a loss of MTI-induced cell wall based defense against the non-host powdery mildew Erysiphe pisi. This is thus in stark contrast to the involvement of a multitude of PLD isoforms in the HR triggered by AvrRpm1 recognition.

  9. Designing a CR Test bed

    DEFF Research Database (Denmark)

    Cattoni, Andrea Fabio; Buthler, Jakob Lindbjerg; Tonelli, Oscar;

    2014-01-01

    Research on intelligent and reconfigurable wireless systems is in continuous evolution. Nevertheless, in order to fix some keystones, more and more researchers are entering the idea of research-oriented test beds. Unfortunately, it is very difficult for a wide number of research groups to start...... with their own set up, since the potential costs and efforts could not pay back in term of expected research results. Software Defined Radio solutions offer an easy way to communication researchers for the development of customized research test beds. While several hardware products are commercially available...... they are up and running in generating results. With this chapter we would like to provide a tutorial guide, based on direct experience, on how to enter in the world of test bed-based research, providing both insight on the issues encountered in every day development, and practical solutions. Finally...

  10. Quinolone-resistance in Salmonella is associated with decreased mRNA expression of virulence genes invA and avrA, growth and intracellular invasion and survival.

    Science.gov (United States)

    Wang, Yu-Ping; Li, Lin; Shen, Jian-Zhong; Yang, Fu-Jiang; Wu, Yong-Ning

    2009-02-01

    A variety of environmental factors, such as oxygen, pH, osmolarity and antimicrobial agents, modulate the expression of Salmonella pathogenicity islands (SPI) genes. This study investigated SPI-1 gene expression and the pathogenicity of quinolone-resistant Salmonella. mRNA expression levels of the invA and avrA genes, located in SPI-1, in quinolone-susceptible and quinolone-resistant Salmonella strains were determined using real-time fluorescent quantitative reverse transcription-polymerase chain reaction (RT-PCR). Twenty-five quinolone-resistant Salmonella mutants were derived from quinolone-susceptible strains by multiple-passage selection through increasing concentrations of ciprofloxacin in vitro, while an additional 15 strains were quinolone-resistant Salmonella clinical isolates. Sequence analysis showed no gene deletion or point mutations of nine SPI-1 genes (including invA and avrA) occurred in either the selected or clinical quinolone-resistant strains, while a single gyrA point mutation (S83F) was observed in all 40 quinolone-resistant strains. The mRNA expression levels of invA and avrA were significantly decreased (P<0.005) in quinolone-resistant strains (clinically acquired or experimentally selected in vitro), compared to the quinolone-susceptible strains. The resistant strains also had a slower growth rate combined with decreased epithelial cell invasion and intracellular replication in epithelial cells and macrophages. The results suggest that quinolone-resistance may be associated with lower virulence and pathogenicity than in quinolone-susceptible strains.

  11. 基于AVR嵌入式单片机的交通路口控制系统%Research of Traffic Crossing Control System Based On AVR Embedded Single-Chip

    Institute of Scientific and Technical Information of China (English)

    张文增

    2010-01-01

    AVR 单片机是高性能的嵌入式微控制器系列.本文介绍以其中的AT90S8518为控制核心,建立一套实用稳定的高性能控制系统,实现对现代城市交通路口多种类型信号指示的自动化、智能化、人性化实时控制,以改善城市交通.

  12. EMERGING TECHNOLOGY BULLETIN: SPOUTED BED REACTOR

    Science.gov (United States)

    The Spouted Bed Reactor (SBR) technology utilizes the unique attributes of the "spouting " fluidization regime, which can provide heat transfer rates comparable to traditional fluid beds, while providing robust circulation of highly heterogeneous solids, concurrent with very agg...

  13. [Historical analysis of the hospital bed].

    Science.gov (United States)

    Fajardo-Ortiz, Guillermo; Fajardo-Dolci, Germán

    2010-01-01

    Until now the bed has been the basic physical resource in hospitals. This type of furniture has served to study and treat patients, through out the centuries it has undergone changes in the materials they are made of dimensions, functionality, accessories, aesthetic, and design. The hospital bed history is not well known, there are thousands of documents about the evolution of hospitals, but not enough is known about hospital beds, a link between the past and the present. The medical, anthropological, technological, social, and economic dynamics and knowledge have produced a variety of beds in general and hospital beds in particular. From instinctive, rustic, poor and irregular "sites" that have differed in shape and size they had evolved into ergonomic equipment. The history of the hospital bed reflects the culture, techniques and human thinking. Current hospital beds include several types: for adults, for children, for labor, for intensive therapy, emergency purposes, census and non census beds etc.

  14. Chinese Bedding Technology Standard under Drafting

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    National Home Textile Standardization Technology Committee(NHTSTC)set up its Bedding Branch Committee. This will promote the work of Chinese bedding technology standardization and a symbol that China step up to meet the

  15. Magnetic fabric of sheared till: A strain indicator for evaluating the bed deformation model of glacier flow

    Science.gov (United States)

    Hooyer, T.S.; Iverson, N.R.; Lagroix, F.; Thomason, J.F.

    2008-01-01

    Wet-based portions of ice sheets may move primarily by shearing their till beds, resting in high sediment fluxes and the development of subglacial landforms. This model of glacier movement, which requires high bed shear strains, can be tested using till microstructural characteristics that evolve during till deformation. Here we examine the development of magnetic fabric using a ring shear device to defom two Wisconsin-age basal tills to shear strains as high as 70. Hysteresis experiments and the dependence of magnetic susceptibility of these tills on temperature demonstrate that anisotropy of magnetic susceptibility (AMS) develops during shear due to the rotation of primarily magnetite particles that are silt sized or smaller. At moderate shear strains (???6-25), principal axes of maximum magnetic susceptibility develop a strong fabric (S1 eignevalues of 0.83-0.96), without further strengthening at higher strains, During deformation, directions of maximum susceptibility cluster strongly in the direction of shear and plunge 'up-glacier,' consistent with the behavior of pebbles and sand particles studied in earlier experiments. In contrast, the magnitude of AMS does not vary systematically with strain and is small relative to its variability among samples; this is because most magnetite grains are contained as inclusions in larger particles and hence do not align during shear. Although processes other than pervasive bed deformation may result in strong flow parallel fabrics, AMS fabrics provide a rapid and objective means of identifying basal tills that have not been sheared sufficiently to be compatible with the bed deformation model. Copyright 2008 by the American Geophysical Union.

  16. 基于AVR多功能报警系统的温湿度模块的设计%The Design of Temperature and Humidity Module in Multi-Functional Alarm System Based on AVR

    Institute of Scientific and Technical Information of China (English)

    陈龙; 张志达

    2011-01-01

    In order to achieve the multi-functional home alarm system, the design of controlling modules such as temperature and humidity by the AVR Mega 16 microcontroller as the core with the LCD display is studied. It plays the role of real-time alarm monitoring, and makes the system complete the default requirements. After the hardware and software debugging, the results show that the system can work successfully, the interface is good, the functions can be extended, and the design is an ideal multi-functional alarm system.%为了实现家庭多功能报警系统,本设计由AVR Mega16单片机作为控制核心,控制温湿度等模块的正常工作,同时由液晶LCD显示,起到实时的监控报警作用,使系统完成预设的要求.经过软硬件调试,结果表明系统成功工作,而且界面良好,功能还可以扩展,是理想的显示报警系统的设计.

  17. Analyses of wrky18 wrky40 plants reveal critical roles of SA/EDS1 signaling and indole-glucosinolate biosynthesis for Golovinomyces orontii resistance and a loss-of resistance towards Pseudomonas syringae pv. tomato AvrRPS4.

    Science.gov (United States)

    Schön, Moritz; Töller, Armin; Diezel, Celia; Roth, Charlotte; Westphal, Lore; Wiermer, Marcel; Somssich, Imre E

    2013-07-01

    Simultaneous mutation of two WRKY-type transcription factors, WRKY18 and WRKY40, renders otherwise susceptible wild-type Arabidopsis plants resistant towards the biotrophic powdery mildew fungus Golovinomyces orontii. Resistance in wrky18 wrky40 double mutant plants is accompanied by massive transcriptional reprogramming, imbalance in salicylic acid (SA) and jasmonic acid (JA) signaling, altered ENHANCED DISEASE SUSCEPTIBILITY1 (EDS1) expression, and accumulation of the phytoalexin camalexin. Genetic analyses identified SA biosynthesis and EDS1 signaling as well as biosynthesis of the indole-glucosinolate 4MI3G as essential components required for loss-of-WRKY18 WRKY40-mediated resistance towards G. orontii. The analysis of wrky18 wrky40 pad3 mutant plants impaired in camalexin biosynthesis revealed an uncoupling of pre- from postinvasive resistance against G. orontii. Comprehensive infection studies demonstrated the specificity of wrky18 wrky40-mediated G. orontii resistance. Interestingly, WRKY18 and WRKY40 act as positive regulators in effector-triggered immunity, as the wrky18 wrky40 double mutant was found to be strongly susceptible towards the bacterial pathogen Pseudomonas syringae DC3000 expressing the effector AvrRPS4 but not against other tested Pseudomonas strains. We hypothesize that G. orontii depends on the function of WRKY18 and WRKY40 to successfully infect Arabidopsis wild-type plants while, in the interaction with P. syringae AvrRPS4, they are required to mediate effector-triggered immunity.

  18. Fluidized Bed Reactor as Solid State Fermenter

    OpenAIRE

    Krishnaiah, K.; Janaun, J.; Prabhakar, A.

    2005-01-01

    Various reactors such as tray, packed bed, rotating drum can be used for solid-state fermentation. In this paper the possibility of fluidized bed reactor as solid-state fermenter is considered. The design parameters, which affect the performances are identified and discussed. This information, in general can be used in the design and the development of an efficient fluidized bed solid-state fermenter. However, the objective here is to develop fluidized bed solid-state fermenter for palm kerne...

  19. 基于VLSI平台的AVR处理器仿真与设计%Simulation and design of AVR processor based on VLSI platform

    Institute of Scientific and Technical Information of China (English)

    2013-01-01

    Internal limited logic resources and external fixed⁃pin package of traditional microprocessors greatly limit their application range. The internal structure,memory management structure and instruction set architecture of micro control unit (MCU)are described. The abundant logic resources of field programmable gate array(FPGA)are used to virtualize the proces⁃sor core of traditional MCU. Wishbone bus is added to connect processor core with common peripherals to form a virtual MCU platform. Moreover,the bottom⁃up design of AVR core is performed with hardware description languages such as Verilog and VHDL,which is connected with common peripherals to build a system. Board level validation was carried out with XILINX Vir⁃tex⁃II Pro chip. The result shows that the set objective is achieved and the system which runs stable is compatible with standard MCU. This method continues the vitality of traditional MCU,and makes it further progressed.%  传统的微处理器由于内部有限的逻辑资源和外部固定的引脚封装,大大限制了应用范围。为此,在阐述微控制器的内部结构、存储器管理结构和指令集结构后,利用现场可编程门阵列丰富的逻辑资源,虚拟出传统微控制器的处理器核心,添加Wishbone总线,将处理器核心与通用外设连接构成一个虚拟的微控制器平台,并使用硬件描述语言Verilog和VHDL,自底向上设计AVR处理器核心,与通用外设互连组成系统,使用XILINX Virtex⁃Ⅱ Pro芯片进行板级验证。结果表明,实现了既定目标,与标准的微控制器兼容,系统运行稳定。该方法延续了传统微控制器的生命力,能使其得到更大发展。

  20. Design of anti bedsore cushion controller based on AVR MCU%基于AVR的防褥疮气垫控制器设计

    Institute of Scientific and Technical Information of China (English)

    周平; 单纯玉

    2012-01-01

    Objective The anti bedsore cushions have certain disadvantages such as simple work mode, unfriendly user interface,lack of fault alarm measurement. This paper presents a microcontroller of anti bedsore cushion based on AVR MCU. Methods The microcontroller consists of Atemegal6 as the core and peripheral circuits including pressure sensor,air pressure detection circuit,LCD display circuit,air pump drive circuit and other circuits. The microcontroller controls the air pump to make the air cushion produce adjustable fluctuations following the input parameters such as weight, period, work time. We connect an air pump to inflate the air cushion under different work parameters for test. Results The test results show that the microcontroller works steadily and makes air cushion produce regular fluctuations that could prevent bedsores. Conclusions The user interface of the anti bedsore cushion with the microcontroller is friendly, the work mode is various and steady, and the cost is low.%目的 针对防褥疮气垫工作模式单一、故障报警措施缺乏、操作界面呆板等不足,本文提出基于AVR单片机的防褥疮气垫微控制器设计方案.方法 该微控制器以Atmega16为核心,外设电路包括压力传感器、气压检测电路、液晶显示电路、气泵驱动电路等,可根据体重、周期、工作时间参数设置不同,控制气泵使气垫产生幅度、周期、时间可调的波动式翻滚达到防治褥疮的作用.连接气泵对气垫充气测试,设置不同的工作参数,观察并比较测试结果.结果 控制器运行稳定,可使气垫产生规律的波动式翻滚,符合防治褥疮的要求.结论 基于该微控制器的防褥疮气垫操作界面友好,工作模式多样,并且工作安全可靠,成本低廉.

  1. Bed Bug Education for School Maintenance

    Science.gov (United States)

    Henriksen, Missy

    2012-01-01

    Bed bugs are a growing problem, not only in homes and hotels, but also in schools and colleges. Facility administrators and staff need to understand the bed bug resurgence and develop best practices to deal with an infestation. In this article, the author offers tips for preventing and treating bed bugs in school and university settings.

  2. 21 CFR 868.5180 - Rocking bed.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Rocking bed. 868.5180 Section 868.5180 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES ANESTHESIOLOGY DEVICES Therapeutic Devices § 868.5180 Rocking bed. (a) Identification. A rocking bed is a...

  3. Evaluation of the Accumulation of Trace Metals (as, U, CR, CU, PB, Zn) on Iron-Manganese Coatings on in Situ Stream Pebbles and Emplaced Substrates

    Science.gov (United States)

    Turpin, M. M.; Blake, J.; Crossey, L. J.; Ali, A.; Hansson, L.

    2015-12-01

    Exposure to trace metals (As, U, Cr, Cu, Pb, Zn) has potential negative health effects on human populations and wildlife. Geothermal waters often have elevated concentrations of trace elements and understanding the geochemical cycling of these elements can be challenging. Previous studies have utilized in situ stream pebbles and glass or ceramic substrates with iron-manganese oxide coatings to understand contamination and or chemical cycling. This project's main focus is to develop an ideal tracing method using adsorption onto substrate surfaces and to define key parameters that are necessary for the phenomenon of adsorption between trace metals and these surface coatings to occur. Sampling locations include the Jemez River and Rio San Antonio in the Jemez mountains, northern New Mexico. Both streams have significant geothermal inputs. Pebbles and cobbles were gathered from the active stream channel and 6mm glass beads and 2 X1 in. ceramic plates were placed in streams for three weeks to allow for coating accumulation. Factors such as leachate type, water pH, substrate type, coating accumulation period and leach time were all considered in this experiment. It was found that of the three leachates (aqua regia, 10% aqua regia and hydroxylamine), hydroxylamine was the most effective at leaching coatings without dissolving substrates. Samples leached with aqua regia and 10% aqua regia were found to lose weight and mass over the following 5, 7, and 10 day measurements. Glass beads were determined to be more effective than in stream pebbles as an accumulation substrate: coatings were more easily controlled and monitored. Samples leached with hydroxylamine for 5 hours and 72 hours showed little difference in their leachate concentrations, suggesting that leach time has little impact on the concentration of leachate samples. This research aims to find the best method for trace metal accumulation in streams to aid in understanding geochemical cycling.

  4. Comparison of the Effects of No Tillage, Minimum Tillage and Conventional Tillage on Dry Land Wheat Yield in Pebbly Field in Tropical Region

    OpenAIRE

    N Loveimi; M. Safari; N Heidarpour

    2016-01-01

    The current study was conducted to compare different tillage methods on wheat yield in pebbly dry land areas done within three years (2006-2008) in north Khouzestan (Baghmalek city) in randomized block design with five treatments and four replications. The experimental treatments were:(1)chisel plow +seed-drill, (2)Semi plow(mold board plow with remove mold board)+seed-drill, (3)no-till-drill, (4)sweep plow +seed-drill and (5)conventional method(mold board plow+ broadcasting seed and fertiliz...

  5. Review of acute cancer beds.

    LENUS (Irish Health Repository)

    Evans, D S

    2012-01-01

    A review of admissions to cancer services at University Hospital Galway (UHG) was undertaken to assess the appropriateness of hospital usage. All cancer specialty patients admitted from 26-28 May 2009 were reviewed (n = 82). Chi square tests, Exact tests, and One-way ANOVA were utilised to analyse key issues emerging from the data. Fifty (61%) were classified as emergencies. Twenty three (67%) occupied a designated cancer bed with 24 (30%) in outlying non-oncology wards. The mean length of stay was 29.3 days. Possible alternatives to admission were identified for 15 (19%) patients. There was no evidence of discharge planning for 50 (60%) admissions. There is considerable potential to make more appropriate utilisation of UHG for cancer patients, particularly in terms of reducing bed days and length of stay and the proportion of emergency cancer admissions, and further developing integrated systems of discharge planning.

  6. Bed bathing patients in hospital

    OpenAIRE

    L Downey; Lloyd, Hilary

    2008-01-01

    There are a number of circumstances that may affect an individual's ability to maintain personal hygiene. Hospitalised patients, and in particular those who are bedridden, may become dependent on nursing staff to carry out their hygiene needs. Assisting patients to maintain personal hygiene is a fundamental aspect of nursing care. However, it is a task often delegated to junior or newly qualified staff. This article focuses on the principles of bed bathing patients in hospital, correct proced...

  7. THE BAUXITES AND JELAR - BEDS

    Directory of Open Access Journals (Sweden)

    Krešimir Sakač

    1993-12-01

    Full Text Available Minor bauxite deposits and occurrences were formed in technically disturbed environments in the middle part of the Adriatic geotectonic unit in Dinarides, contemporary with the clastic Jelar-beds in the Late Lutetian time. Uneven chemical composition of these Eocene bauxites, their sporadic occurrences in developed paleorelief as well as characteristic petrographic composition of the immediate overlying rocks point out at different genetical conditions (the paper is published in Croatian.

  8. Solids mixing in spouted beds

    OpenAIRE

    Cook, H. H.; Bridgwater, J.; Professor J. Bridgwater

    1981-01-01

    Many industrial processes require contact between particles and a fluid or spray in order to effect drying, coating or granulation. One device capable of contacting fluid and particles efficiently is a spouted bed in which a jet of fluid is injected into solid particles. This forms an open channel or spout and induces material circulation in a downward moving annulus. For the continuous throughput of solids, knowledge is required of the mixing and particle motions within th...

  9. The statistical character of packed-bed heat transport properties

    OpenAIRE

    Wijngaarden, R.J.; Westerterp, K. R.

    1992-01-01

    Packed beds are essentially heterogeneous on a pellet scale. For random packed beds this heterogeneity causes a statistical character both on a pellet and bed scale. We discuss experimental results which deal with bed-scale statistics.

  10. Method and apparatus for a combination moving bed thermal treatment reactor and moving bed filter

    Energy Technology Data Exchange (ETDEWEB)

    Badger, Phillip C.; Dunn, Jr., Kenneth J.

    2015-09-01

    A moving bed gasification/thermal treatment reactor includes a geometry in which moving bed reactor particles serve as both a moving bed filter and a heat carrier to provide thermal energy for thermal treatment reactions, such that the moving bed filter and the heat carrier are one and the same to remove solid particulates or droplets generated by thermal treatment processes or injected into the moving bed filter from other sources.

  11. Equilibrium bed-concentration of nonuniform sediment

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    Knowledge of the equilibrium bed-concentration is vital to mathematical modeling of the river-bed deformation associated with suspended load but previous investigations only dealt with the reference concentration of uniform sediment because of difficulties in observation of the bed-concentration. This work is a first attempt to develop a theoretical formula for the equilibrium bed-concentration of any fraction of nonuniform sediment defined at the bed-surface. The formula is based on a stochastic-mechanistic model for the exchange of nonuniform sediment near the bed, and described as a function of incipient motion probability, non-ceasing probability, pick-up probability, and the ratio of the average single-step continuous motion time to static time. Comparison of bed-concentration calculated from the proposed formula with the measured data showed satisfactory agreement, indicating the present formula can be used for solving the differential equation governing the motion of suspended load.

  12. Bed bug aggregation pheromone finally identified.

    Science.gov (United States)

    Gries, Regine; Britton, Robert; Holmes, Michael; Zhai, Huimin; Draper, Jason; Gries, Gerhard

    2015-01-19

    Bed bugs have become a global epidemic and current detection tools are poorly suited for routine surveillance. Despite intense research on bed bug aggregation behavior and the aggregation pheromone, which could be used as a chemical lure, the complete composition of this pheromone has thus far proven elusive. Here, we report that the bed bug aggregation pheromone comprises five volatile components (dimethyl disulfide, dimethyl trisulfide, (E)-2-hexenal, (E)-2-octenal, 2-hexanone), which attract bed bugs to safe shelters, and one less-volatile component (histamine), which causes their arrestment upon contact. In infested premises, a blend of all six components is highly effective at luring bed bugs into traps. The trapping of juvenile and adult bed bugs, with or without recent blood meals, provides strong evidence that this unique pheromone bait could become an effective and inexpensive tool for bed bug detection and potentially their control. PMID:25529634

  13. A comprehensive study of noble gases and nitrogen in "Hypatia", a diamond-rich pebble from SW Egypt

    Science.gov (United States)

    Avice, Guillaume; Meier, Matthias M. M.; Marty, Bernard; Wieler, Rainer; Kramers, Jan D.; Langenhorst, Falko; Cartigny, Pierre; Maden, Colin; Zimmermann, Laurent; Andreoli, Marco A. G.

    2015-12-01

    This is a follow-up study of a work by Kramers et al. (2013) on a very unusual diamond-rich rock fragment found in the area of south west Egypt in the south-western side of the Libyan Desert Glass strewn field. This pebble, called Hypatia, is composed of almost pure carbon. Transmission Electron Microscopy (TEM) and X-ray diffraction (XRD) results reveal that Hypatia is mainly made of defect-rich diamond containing lonsdaleite and multiple deformation bands. These characteristics are compatible with an impact origin on Earth and/or in space. We also analyzed concentrations and isotopic compositions of all five noble gases and nitrogen in several ∼mg sized Hypatia samples. These data confirm the conclusion by Kramers et al. (2013) that Hypatia is extra-terrestrial. The sample is relatively rich in trapped noble gases with an isotopic composition being close to the Q component found in many types of meteorites. 40Ar/36Ar ratios in individual steps are as low as 0.4 ± 0.3. Cosmic-ray produced "cosmogenic" 21Ne is present in concentrations corresponding to a nominal cosmic-ray exposure (CRE) age of roughly 0.1 Myr if produced in a typical meter-sized meteoroid. Such an atypically low nominal CRE age suggests high shielding in a considerably larger body. In addition to the Xe-Q composition, an excess of radiogenic 129Xe (from the decay of short-lived radioactive 129I) is observed (129Xe /132Xe = 1.18 + / - 0.03). Two isotopically distinct N components are present, an isotopically heavy component (δ15N ∼ + 20 ‰) released at low temperatures and a major isotopically light component (δ15N ∼ - 110 ‰) at higher temperatures. This disequilibrium in N suggests that the diamonds in Hypatia were formed in space rather than upon impact on Earth (δN15atm = 0 ‰). All our data are broadly consistent with concentrations and isotopic compositions of noble gases in at least three different types of carbon-rich meteoritic materials: carbon-rich veins in ureilites

  14. Tritium breeding mock-up experiments containing lithium titanate ceramic pebbles and lead irradiated with DT neutrons

    Energy Technology Data Exchange (ETDEWEB)

    Jakhar, Shrichand; Abhangi, M.; Tiwari, S. [Institute for Plasma Research, Bhat, Gandhinagar 382 428 (India); Makwana, R. [Department of Physics, MS University, Vadodara (India); Chaudhari, V.; Swami, H.L.; Danani, C.; Rao, C.V.S.; Basu, T.K. [Institute for Plasma Research, Bhat, Gandhinagar 382 428 (India); Mandal, D.; Bhade, Sonali; Kolekar, R.V.; Reddy, P.J. [Bhabha Atomic Research Center, Trombay, Mumbai 400 085 (India); Bhattacharyay, R.; Chaudhuri, P. [Institute for Plasma Research, Bhat, Gandhinagar 382 428 (India)

    2015-06-15

    Highlights: • Breeding benchmark experiment on LLCB TBM in ITER was performed. • Nuclear responses measured are TPR and reaction rate of {sup 115}In(n, n′){sup 115m}In reaction. • Measured responses are compared with calculations by MCNP and FENDL 2.1 library. • TPR measurements agree with calculations in the estimated error bar. • Measured {sup 115}In(n, n′){sup 115m}In reaction rates are underestimated by the calculations. - Abstract: Experiments were conducted with breeding blanket mock-up consisting of two layers of breeder material lithium titanate pebbles and three layers of pure lead as neutron multiplier. The radial dimensions of breeder, neutron multiplier and structural material layers are similar to the current design of the Indian Lead–Lithium cooled Ceramic Breeder (LLCB) blanket. The mock-up assembly was irradiated with 14 MeV neutrons from DT neutron generator. The local tritium production rates (TPR) from {sup 6}Li and {sup 7}Li in breeder layers were measured with the help of two different compositions of Li isotopes (60.69% {sup 6}Li and 7.54% {sup 6}Li) in Li{sub 2}CO{sub 3}. Tritium production in the multiplication layers were also measured with above mentioned two types of pellets to compare the experimental tritium production with calculations. TPR from {sup 6}Li at one location in the breeder layer was also measured by direct online measurement of tritons from {sup 6}Li(n, t){sup 4}He reaction using silicon surface barrier detector and {sup 6}Li to triton converter. Additional verification of neutron spectra (E{sub n} > 0.35 MeV) in the mock-up zones were obtained by measuring {sup 115}In(n, n′){sup 115m}In reaction rate and comparing it with calculated values in all five layers of mock-up. All the measured nuclear responses were compared with transport calculations using code MCNP with FENDL2.1 and FENDL3.0 cross-section libraries. The average C/E ratio for tritium production in enriched Li{sub 2}CO{sub 3} pellets was 1

  15. Bootloader AVR-arkkitehtuurin mikrokontrollerille

    OpenAIRE

    Kaivola, Tommi

    2013-01-01

    TreLab Oloni on mittalaitejärjestelmä, jota voidaan soveltaa muun muassa terveyden huollossa, henkilökohtaisessa hyvinvoinnissa, yksilövalmennuksessa, rakennusautomaatiossa ja logistiikassa. Järjestelmän osana olevan langattoman monitoimilaitteen tulee toimia luotettavasti 24 päivää vuorokaudessa ja seitsemän päivää viikossa pitkän aikaa. Ohjelmistolle asetettujen suurten luotettavuusvaatimusten ja runsaan toiminnallisuuden johdosta laitteeseen on haluttu mahdollisuus päivittää ohjelmisto...

  16. Application of Dual-port RAM in Design of Interface between PCI Bus and AVR%双口RAM在PCI总线与AVR接口设计中的应用

    Institute of Scientific and Technical Information of China (English)

    邓江涛; 傅煊

    2011-01-01

    In order to improve the speed of data transmission between PCI bus and AVR microcontroller, the high-speed data exchange between PCI bus and AVR microcontroller is realized by the dual-port RAM and sharing mode. A way of finite state machine (FSM) is used in this system to convert the PCI interface chip's local logic signal into read-write control signal andaddress data signal. The interface current is validated by the simulation tool ModelSim SE. The simulated waveform ob-tained is in accordance with the requirement. A method of Ping-Pong Operation (PPO) is used in this system to effectively im-prove the speed of data transmission between PCI bus and AVR microcontroller by alternately read and write data storage are-a. Practice has proved that the design method of this paper is an effective method of solving the bottleneck problem of data transmission between high-speed equipment and low-speed equipment.%为了提高PCI总线与AVR单片机之问的数据传输速度,利用双口RAM通过共享的方式实现PCI总线与AVR单片机之间的高速数据交换.利用有限状态机方法将PCI接口芯片局部端逻辑转换为双口RAM读写控制信号和地址数据信号,并通过仿真工具Modelsim Se对接口电路进行了验证,得出的仿真波形符合要求;利用乒乓操作方法实现PCI接口芯片和AVR单片机交替读/写数据存储区,有效提高了PCI总线与AVR单片机之间的数据传输速度.实践证明该设计方法是解决高低速设备的传输瓶颈问题的有效途径.

  17. The Berlin emissivity database (BED)

    Science.gov (United States)

    Maturilli, A.; Helbert, J.; Moroz, L.

    2008-03-01

    Remote-sensing infrared spectroscopy is the principal field of investigation for planetary surfaces composition. Past, present and future missions to the solar system bodies include in their payload, instruments measuring the emerging radiation in the infrared range. Apart from measuring the reflected radiance, more and more spacecrafts are equipped with instruments measuring directly the emitted radiation from the planetary surface. The emitted radiation is not only a function of the composition of the material but also of its texture and especially the grain size distribution. For the interpretation of the measured data an emissivity spectral library of planetary analogue materials in grain size fractions appropriate for planetary surfaces is needed. The Berlin emissivity database (BED) presented here is focused on relatively fine-grained size separates, providing thereby a realistic basis for the interpretation of thermal emission spectra of planetary regoliths. The BED is therefore complimentary to existing thermal emission libraries, like the ASU library for example. BED currently contains emissivity spectra of plagioclase and potassium feldspars, low Ca and high Ca pyroxenes, olivine, elemental sulfur, Martian analogue minerals and volcanic soils, and a lunar highland soil sample measured in the wavelength range from 7 to 22 μm as a function of particle size. For each sample we measured the spectra of four particle size separates ranging from <25 to 250 μm. The device we used is built at DLR (Berlin) and is coupled to a Fourier-transform infrared spectrometer Bruker IFS 88 purged with dry air and equipped with a nitrogen-cooled MCT detector. All spectra were acquired with a spectral resolution of 4 cm -1. We are currently working on upgrading our emissivity facility. A new spectrometer (Bruker VERTEX 80 V) and new detectors will allow us to measure the emissivity of samples in the wavelength range from 1 to 50 μm in a vacuum environment. This will be

  18. MICROTURBULENCE IN GRAVEL BED STREAMS

    Science.gov (United States)

    Papanicolaou, T.; Tsakiris, A. G.; Kramer, C. M.

    2009-12-01

    The overarching objective of this investigation was to evaluate the role of relative submergence on the formation and evolution of cluster microforms in gravel bed streams and its implications to bedload transport. Secondary objectives of this research included (1) a detailed analysis of mean flow measurements around a clast; and (2) a selected number of experimental runs where the mean flow characteristics are linked together with the bed micro-topography observations around a clast. It is hypothesized that the relative submergence is an important parameter in defining the feedback processes between the flow and clasts, which governs the flow patterns around the clasts, thus directly affecting the depositional patterns of the incoming sediments. To examine the validity of the hypothesis and meet the objectives of this research, 19 detailed experimental runs were conducted in a tilting, water recirculating laboratory flume under well-controlled conditions. A fixed array of clast-obstacles were placed atop a well-packed bed with uniform size glass beads. During the runs, multifractional spherical particles were fed upstream of the clast section at a predetermined rate. State-of-the-art techniques/instruments, such as imaging analysis software, Large Scale Particle Velocimeter (LSPIV) and an Acoustic Doppler Velocimetry (ADV) were employed to provide unique quantitative measurements for bedload fluxes, clast/clusters geomorphic patterns, and mean flow characteristics in the vicinity of the clusters. Different flow patterns were recorded for the high relative submergence (HRS) and low relative submergence (LRS) experimental runs. The ADV measurements provided improved insight about the governing flow mechanisms for the HRS runs. These mechanisms were described with flow upwelling at the center of the flume and downwelling occurring along the flume walls. Flow downwelling corresponded to an increase in the free surface velocity. Additionally, the visual observations

  19. [Special beds. Pulmonary therapy system].

    Science.gov (United States)

    Calixto Rodríguez, Joaquín; Rodríguez Martínez, Xavier; Marín i Vivó, Gemma; Paunellas Albert, Josep

    2008-10-01

    To be bedridden reduces one's capacity to move and produces muscular debility that affects the respiratory system leading to a decreased effectiveness in expectoration, the ability to spit up sputum. The pulmonary therapy system integrated in a bed is the result of applying motorized elements to the articulation points of the bad in order to achieve safe positions at therapeutic angles, which improve the breathing-perfusion (blood flow) relationship. This system also makes it possible to apply vibration waves to the patient which favor the elimination of bronchial-pulmonary secretions, the rehabilitation of the bedridden patient and decrease the work load for nursing personnel.

  20. Classifying bed inclination using pressure images.

    Science.gov (United States)

    Baran Pouyan, M; Ostadabbas, S; Nourani, M; Pompeo, M

    2014-01-01

    Pressure ulcer is one of the most prevalent problems for bed-bound patients in hospitals and nursing homes. Pressure ulcers are painful for patients and costly for healthcare systems. Accurate in-bed posture analysis can significantly help in preventing pressure ulcers. Specifically, bed inclination (back angle) is a factor contributing to pressure ulcer development. In this paper, an efficient methodology is proposed to classify bed inclination. Our approach uses pressure values collected from a commercial pressure mat system. Then, by applying a number of image processing and machine learning techniques, the approximate degree of bed is estimated and classified. The proposed algorithm was tested on 15 subjects with various sizes and weights. The experimental results indicate that our method predicts bed inclination in three classes with 80.3% average accuracy.

  1. Gruppebaseret behandling af BED - et faseopdelt behandlingstilbud

    DEFF Research Database (Denmark)

    Laust, Jakob; Lau, Marianne Engelbrecht; Waaddegaard, Mette

    2015-01-01

    Titel: Afrapportering vedr. SATS-puljemidler til behandling og erfaringsopsamling vedr. BED for perioden 1. marts 2013 – 1. maj 2015. Baggrund: Binge Eating Disorder (BED), på dansk tvangsoverspisning, er en udbredt, men overset spiseforstyrrelse med alvorlige psykiske, fysiske og sociale...... konsekvenser. BED blev i 2013 optaget i DSM-5 (Diagnostic and Statistical Manual of Mental Disorders) som en selvstændig diagnose og BED forventes medtaget i den forestående revision af det internationale diagnose system, ICD-11. Sundhedsstyrelsen gav på denne baggrund satspuljemidler til erfaringsopsamling...... vedr. BED. I den forbindelse ansøgte Ambulatorium for Spiseforstyrrelser på Psykoterapeutisk Center Stolpegård ovenstående midler til at udvikle en ambulant, primært psykoterapeutisk gruppebehandling til patienter med moderat til svær BED med fokus på såvel spiseforstyrrelse såvel som overvægt. Metode...

  2. Fluid-bed process for SYNROC production

    International Nuclear Information System (INIS)

    SYNROC is a titanate-based ceramic waste developed for the immobilization of high-level nuclear reactor waste. Lawrence Livermore National Laboratory (LLNL) has investigated a fluid-bed technique for the large-scale production of SYNROC precursor powders. Making SYNROC in a fluid bed permits slurry drying, calcination and reduction-oxidation reactions to be carried out in a single unit. We present the results of SYNROC fluid-bed studies from two fluid-bed units 10 cm in diameter: an internally heated fluid-bed unit developed by Exxon Idaho and an externally heated unit constructed at LLNL. Bed operation over a range of temperatures, feed rates, fluidizing rates, and redox conditions indicate that SYNROC powders of a high density and a uniform particle size can be produced. These powders facilitate the densification step and yield dense ceramics (greater than 95% theoretical density) with well-developed phases and low leaching rates

  3. The WCSAR telerobotics test bed

    Science.gov (United States)

    Duffie, N.; Zik, J.; Teeter, R.; Crabb, T.

    1988-01-01

    Component technologies for use in telerobotic systems for space are being developed. As part of this effort, a test bed was established in which these technologies can be verified and integrated into telerobotic systems. The facility consists of two slave industrial robots, an articulated master arm controller, a cartesian coordinate master arm controller, and a variety of sensors, displays and stimulators for feedback to human operators. The controller of one of the slave robots remains in its commercial state, while the controller of the other robot has been replaced with a new controller that achieves high-performance in telerobotic operating modes. A dexterous slave hand which consists of two fingers and a thumb is being developed, along with a number of force-reflecting and non-force reflecting master hands, wrists and arms. A tactile sensing finger tip based on piezo-film technology has been developed, along with tactile stimulators and CAD-based displays for sensory feedback and sensory substitution. The telerobotics test bed and its component technologies are described, as well as the integration of these component technologies into telerobotic systems, and their performance in conjunction with human operators.

  4. 基于AVR单片机的数字式耳温测量仪的设计%Design of Digital Ear Thermometer Based on AVR Single Chip Microcomputer

    Institute of Scientific and Technical Information of China (English)

    钱明理; 谢海源

    2014-01-01

    Although its popularity in hospital, quality problem of electronic thermometer still needs to be considered. According to application needs, this paper develops a new digital ear thermometer based on AVR single chip microcomputer(SCM). After examination, this device shows good features in stability and accuracy, and could satisfy clinical use.%电子体温计的应用在医院已经逐渐普及,但产品市场良莠不齐。作者根据医院的使用要求,设计了一套基于AVR单片机的数字式耳温测量仪。该仪器经测试,其稳定性、准确性良好,能满足医院使用要求。

  5. Spring packed particle bed fuel element

    International Nuclear Information System (INIS)

    This patent describes a gas cooled particle bed nuclear fuel element. It comprises: a porous inner frit; a porous outer frit attached to the inner frit by an end cap t a first end and radially guided by a shoulder at a second end, forming an annulus between the frits; a fuel particle bed in the annulus; a first compressive device at each end of the annulus; and a second compressive device positioned in the annulus within the fuel particle bed

  6. Fluidized Bed Reactor as Solid State Fermenter

    Directory of Open Access Journals (Sweden)

    Krishnaiah, K.

    2005-01-01

    Full Text Available Various reactors such as tray, packed bed, rotating drum can be used for solid-state fermentation. In this paper the possibility of fluidized bed reactor as solid-state fermenter is considered. The design parameters, which affect the performances are identified and discussed. This information, in general can be used in the design and the development of an efficient fluidized bed solid-state fermenter. However, the objective here is to develop fluidized bed solid-state fermenter for palm kernel cake conversion into enriched animal and poultry feed.

  7. Metabolic Resistance in Bed Bugs

    Directory of Open Access Journals (Sweden)

    Omprakash Mittapalli

    2011-03-01

    Full Text Available Blood-feeding insects have evolved resistance to various insecticides (organochlorines, pyrethroids, carbamates, etc. through gene mutations and increased metabolism. Bed bugs (Cimex lectularius are hematophagous ectoparasites that are poised to become one of the major pests in households throughout the United States. Currently, C. lectularius has attained a high global impact status due to its sudden and rampant resurgence. Resistance to pesticides is one factor implicated in this phenomenon. Although much emphasis has been placed on target sensitivity, little to no knowledge is available on the role of key metabolic players (e.g., cytochrome P450s and glutathione S-transferases towards pesticide resistance in C. lectularius. In this review, we discuss different modes of resistance (target sensitivity, penetration resistance, behavioral resistance, and metabolic resistance with more emphasis on metabolic resistance.

  8. Fluidized bed heat treating system

    Energy Technology Data Exchange (ETDEWEB)

    Ripley, Edward B; Pfennigwerth, Glenn L

    2014-05-06

    Systems for heat treating materials are presented. The systems typically involve a fluidized bed that contains granulated heat treating material. In some embodiments a fluid, such as an inert gas, is flowed through the granulated heat treating medium, which homogenizes the temperature of the heat treating medium. In some embodiments the fluid may be heated in a heating vessel and flowed into the process chamber where the fluid is then flowed through the granulated heat treating medium. In some embodiments the heat treating material may be liquid or granulated heat treating material and the heat treating material may be circulated through a heating vessel into a process chamber where the heat treating material contacts the material to be heat treated. Microwave energy may be used to provide the source of heat for heat treating systems.

  9. Status of the EXOTIC-8 programme and first in-pile results for Li{sub 2}TiO{sub 3} pebbles

    Energy Technology Data Exchange (ETDEWEB)

    Van der Laan, J.G.; Stijkel, M.P. [Netherlands Energy Research Foundation (ECN), Petten (Netherlands); Conrad, R.

    1998-03-01

    After renewal of the Tritium Measuring Station the HFR is again fully operational for in-pile breeder irradiations. The EXOTIC-8 series has started with first three experiments on June 12, 1997. First in-pile results have been obtained for Li{sub 2}TiO{sub 3}-pebbles supplied by CEA: preliminary analyses indicate satisfactory in-pile behaviour with fast recovery from transient conditions. Five further experiments have been defined which implies that in the present planning EXOTIC-8 is filled completely up to Fall`98 and 2 of 4 positions are occupied up to Spring`99. P.I.E. results will be obtained from Spring`98 onwards. (J.P.N.)

  10. Particle pressures in fluidized beds. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Campbell, C.S.; Rahman, K.; Jin, C.

    1996-09-01

    This project studies the particle pressure, which may be thought of as the force exerted by the particulate phase of a multiphase mixture, independently of that exerted by other phases. The project is divided into two parts, one concerning gas and the other liquid fluidized beds. Previous work on gas fluidized beds had suggested that the particle pressures are generated by bubbling action. Thus, for these gas fluidized bed studies, the particle pressure is measured around single bubbles generated in 2-D fluidized beds, using special probes developed especially for this purpose. Liquid beds are immune from bubbling and the particle pressures proved too small to measure directly. However, the major interest in particle pressures in liquid beds lies in their stabilizing effect that arises from the effective elasticity (the derivative of the particle pressure with respect to the void fraction), they impart to the bed. So rather than directly measure the particle pressure, the authors inferred the values of the elasticity from measurements of instability growth in liquid beds; the inference was made by first developing a generic stability model (one with all the normally modeled coefficients left undetermined) and then working backwards to determine the unknown coefficients, including the elasticity.

  11. Effective Thermal Conductivity of Adsorbent Packed Beds

    Science.gov (United States)

    Mori, Hideo; Hamamoto, Yoshinori; Yoshida, Suguru

    The effective thermal conductivity of adsorbent packed beds of granular zeolite 13X and granular silica gel A in the presence of stagnant steam or air was measured under different conditions of the adsorbent bed temperature, particle size and filler-gas pressure. The measured effective thermal conductivity showed to become smaller with decreasing particle size or decreasing pressure, but it was nearly independent of the bed temperature. When steam was the filler-gas, the rise in the thermal conductivity of the adsorbent particles due to steam adsorption led to the increase in the effective thermal conductivity of the bed, and this effect was not negligible at high steam pressure for the bed of large particle size. It was found that both the predictions of the effective thermal conductivity by the Hayashi et al.'s model and the Bauer-Schlünder model generally agreed well with the measurements, by considering the particle thermal conductivity rise due to steam adsorption. The thermal conductivity of a consolidated bed of granular zeolite 13X was also measured, and it was found to be much larger than that of the packed bed especially at lower pressure. The above prediction models underestimated the effective thermal conductivity of the consolidated bed.

  12. Bed-levelling experiments with suspended load

    NARCIS (Netherlands)

    Talmon, A.M.; De Graaff, J.

    1991-01-01

    Bed-levelling experiments are conducted in a straight laboratory channel. The experiments involve a significant fraction of suspended sediment transport. The purpose of the experiments is to provide data for modelling of the direction of sediment transport on a transverse sloping alluvial river bed,

  13. Nonlinear dynamical characteristics of bed load motion

    Institute of Scientific and Technical Information of China (English)

    BAI Yuchuan; XU Haijue; XU Dong; Chiu-On Ng

    2006-01-01

    Bed forms of various kinds that evolve naturally on the bottom of sandy coasts and rivers are a result of the kinematics of bed load transport. Based on the group motion of particles in the bed load within the bottom layer, a study on the nonlinear dynamics of bed load transport is presented in this paper. It is found that some development stages, such as the initiation, the equilibrium sediment transport, and the transition from a smooth bed to sand dunes, can be accounted for by different states in the nonlinear system of the bed load transport. It is verified by comparison with experimental data reported by Laboratoire Nationae D'Hydraulique, Chatou, France, that the evolution from a smooth bed to sand dunes is determined by mutation in the bed load transport. This paper presents results that may offer theoretical explanations to the experimental observations. It is also an attempt to apply the state-of-the-art nonlinear science to the classical sediment transport mechanics.

  14. Particle Pressures in Fluidized Beds. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Campbell, C.S.; Rahman, K.; Jin, C.

    1996-09-01

    This project studies the particle pressure, which may be thought of as the force exerted by the particulate phase of a multiphase mixture, independently of that exerted by other phases. The project is divided into two parts, one concerning gas and the other liquid fluidized beds. Previous work on gas fluidized beds had suggested that the particle pressures are generated by bubbling action. Thus, for these gas fluidized bed studies, the particle pressure is measured around single bubbles generated in 2-D fluidized beds, using special probes developed especially for this purpose. Liquid beds are immune from bubbling and the particle pressures proved too small to measure directly. However, the major interest in particle pressures in liquid beds lies in their stabilizing effect that arises from the effective elasticity (the derivative of the particle pressure with respect to the void fraction): they impart to the bed. So rather than directly measure the particle pressure, we inferred the values of the elasticity from measurements of instability growth in liquid beds the inference was made by first developing a generic stability model (one with all the normally modeled coefficients left undetermined)and then working backwards to determine the unknown coefficients, including the elasticity.

  15. Container and Raised-Bed Gardening

    OpenAIRE

    Niemiera, Alexander Xavier, 1951-

    2009-01-01

    Raised beds, while requiring a high initial labor input, offer improved growing conditions and advantages compared to the existing soil. Improved plant growth, increased yields, and better accessibility are reasons to construct raised beds. This publication reviews the proper containers and plants, planting instructions, watering and potting soils, overwintering plants and more.

  16. Prevalence, Knowledge, and Concern About Bed Bugs.

    Science.gov (United States)

    Kaylor, Mary Beth; Wenning, Paul; Eddy, Christopher

    2015-01-01

    Recent research suggests that the resurgence of bed bugs in the U.S. has occurred at an alarming rate. Assumptions have been made that socioeconomic status is not associated with the prevalence of bed bug infestations. Little information is available at the local level, however, about the prevalence of bed bugs in private homes. The authors' pilot study aimed to identify prevalence, knowledge, and concern about bed bugs in one higher income village in Ohio utilizing survey methodology. Responses from 96 individuals who completed the Prevalence, Knowledge, and Concern About Bed Bugs survey were utilized for analysis. The majority of the sample respondents were white and 95% reported that they owned their residence. Only 6% knew someone with bed bugs. Additionally, 52% reported they were somewhat concerned about bed bugs. About 46% reported that they had changed their behavior. For a higher income area, the prevalence was dissimilar to the rate reported in the general public (about 20%). This suggests that bed bugs may be an environmental issue effecting low-income populations disproportionately. Further research is needed in areas of differing socioeconomic levels. PMID:26427264

  17. Determination of true bed thickness using folded bed model and borehole data

    Energy Technology Data Exchange (ETDEWEB)

    Xu, S.S.; Velasquillo-Martinez, L.G.; Grajales-Nishimura, J.M.; Murillo-Muneton, G. [Inst. Mexicano del Petroleo, Mexico City (Mexico); Garcia-Hernandez, J. [Petroleos Mexicanos Exploracion y Produccion, Tamaulipas (Mexico); Nieto-Samaniego, A.F. [Nacional Autonoma de Mexico Univ., Veracruz (Mexico). Centro de Geociencias

    2007-11-15

    The actual thickness of a given formation perpendicular to the bedding plane is known as the true bed thickness. Petroleum engineers rely on information regarding true bed thickness, particularly in dipping beds and in deviated holes because reservoir volume and isochore maps depend on these properties and not on the measured thickness. True bed thickness can be estimated from information gathered from well logs such as the dipmeter and borehole images. However, when deviations and dips exceed 10 degrees, corrections are needed. In this paper, a folded bed model was proposed to calculate the true bed thickness in the subsurface utilizing well log data. The value of true bed thickness (t) was shown to depend on the angle and the direction of the dip of the measured formation, as well as the drift angle and azimuth of the borehole. A case study from the Cantarell oil field in the southern Gulf of Mexico, offshore Campeche, was used to test the folded bed method. The model was shown to yield more uniform spatial change of the values of t, compared to the monoclinal bed model that often overestimates the average value of t. The maximum relative deviation of t from the monoclinal bed model reached 22.3 per cent and the maximum absolute deviation of t reached 34.5 m. The key factors that influence the values of t were found to be the bed dip, the dip difference between the top and base of the bed and the deviated angle of the well. The folded bed model yielded fewer changed values of the true bed thickness. 10 refs., 2 tabs., 9 figs.

  18. Peering inside the granular bed: illuminating feedbacks between bed-load transport and bed-structure evolution

    Science.gov (United States)

    Houssais, M.; Jerolmack, D. J.; Martin, R. L.

    2013-12-01

    The threshold of motion is perhaps the most important quantity to determine for understanding rates of bed load transport, however it is a moving target. Decades of research show that it changes in space and in time within a river, and is highly variable among different systems; however, these differences are not mechanistically understood. Recent researchers have proposed that the critical Shields stress is strongly dependent on the local configuration of the sediment bed [Frey and Church, 2011]. Critical Shields stress has been observed to change following sediment-transporting flood events in natural rivers [e.g., Turowski et al., 2011], while small-scale laboratory experiments have produced declining bed load transport rates associated with slow bed compaction [Charru et al., 2004]. However, no direct measurements have been made of the evolving bed structure under bed load transport, so the connection between granular controls and the threshold of motion remains uncertain. A perspective we adopt is that granular effects determine the critical Shields stress, while the fluid supplies a distribution of driving stresses. In order to isolate the granular effect, we undertake laminar bed load transport experiments using plastic beads sheared by a viscous oil in a small, annular flume. The fluid and beads are refractive index matched, and the fluid impregnated with a fluorescing powder. When illuminated with a planar laser sheet, we are able to image slices of the granular bed while also tracking the overlying sediment transport. We present the first results showing how bed load transport influences granular packing, and how changes in packing influence the threshold of motion to feed back on bed load transport rates. This effect may account for much of the variability observed in the threshold of motion in natural streams, and by extension offers a plausible explanation for hysteresis in bed load transport rates observed during floods. Charru, F., H. Mouilleron, and

  19. Comparison of the Effects of No Tillage, Minimum Tillage and Conventional Tillage on Dry Land Wheat Yield in Pebbly Field in Tropical Region

    Directory of Open Access Journals (Sweden)

    N Loveimi

    2016-04-01

    Full Text Available The current study was conducted to compare different tillage methods on wheat yield in pebbly dry land areas done within three years (2006-2008 in north Khouzestan (Baghmalek city in randomized block design with five treatments and four replications. The experimental treatments were:(1chisel plow +seed-drill, (2Semi plow(mold board plow with remove mold board+seed-drill, (3no-till-drill, (4sweep plow +seed-drill and (5conventional method(mold board plow+ broadcasting seed and fertilizer+ sweep plow. These treatments included minimum tillage (treatments 1, 2 and 4, no tillage (treatment 3 and conventional tillage (treatment 5. Complex variance analyses of three years data showed that there was no significant difference between tillage methods and interaction of tillage methods with year in soil moisture content in different plant growth stages (stem, flowering, and filling seeds stages but years were different in this factor. Variance analyses of data showed that there was no significant difference between different tillage methods in percent of organic materials in different soil depths in the end of the project. However, no difference in tillage methods in the amount of organic material has been analyzed based on the pebbly conditions. The complex variance analyses of data also showed that tillage methods had significant effect on grain yield and other agronomical factors, except plant height and harvest index. According to the results any devices cause to back more gravel and cobblestone into sub soil layer provide more grain yield. Therefore, mold board plow resulted in maximum yield in three experimental years which were different in amount and distribution of rainfall, and also in third year the amount of rainfall was considerably low. The grain yield averages of three years were 1333, 1558, 1190, 1080 and 1787 Kg.ha-1 for chisel plow, semi plow, no-till-drill, sweep plow and mold board plow respectively.

  20. Sand attrition in conical spouted beds

    Institute of Scientific and Technical Information of China (English)

    Aranzazu R. Fernández-Akarregui; Jon Makibar; Isabel Alava; Luis Diaz; Fernando Cueva; Roberto Aguado; Gartzen Lopez; Martin Olazar

    2012-01-01

    A study was carried out on the attrition in conical spouted beds using two sands with different properties for several bed heights and gas flow rates.Furthermore,the influence of a draft tube was studied at ambient and high temperatures.The main objective was to acquire knowledge on the attrition of sand beds for biomass pyrolysis in a pilot plant provided with a conical spouted bed reactor.A first-order kinetic equation is proposed for sand attrition in a conical spouted bed at room temperature.The predicted attrition rate constant depends exponentially on excess air velocity over that for minimum spouting.Both the draft tube and temperature increase contribute to reduction of attrition.

  1. Incipient motion of gravel and coal beds

    Indian Academy of Sciences (India)

    Subhasish Dey; Uddaraju V Raju

    2002-10-01

    An experimental study on incipient motion of gravel and coal beds under unidirectional steady-uniform flow is presented. Experiments were carried out in a flume with various sizes of gravel and coal samples. The critical bed shear stresses for the experimental runs determined using side-wall correction show considerable disagreement with the standard curves. The characteristic parameters affecting the incipient motion of particles in rough-turbulent regime, identified based on physical reasoning and dimensional analysis, are the Shields parameter, particle Froude number, non-dimensional particle diameter and non-dimensional flow depth. Equations of critical bed shear stress for the initial movement of gravel and coal beds were obtained using experimental data. The method of application of critical bed shear stress equations is also mentioned.

  2. Innovative Bed Load Measurement System for Large Alpine Gravel-Bed Rivers

    Science.gov (United States)

    Seitz, H.; Habersack, H. M.

    2009-04-01

    The aim of the work is to figure out the bed load transport processes using direct and surrogate measurement methods for the free flowing reach of the Drau River and its most important tributary Isel River, both large Alpine gravel-bed rivers, situated in the south western part of Austria. There are some techniques for bed load measurements in natural streams; we used collecting moving particles and indirectly determining transport intensity at the study sites. Former measurements in the study reach were performed also using mobile bed load samplers and fixed bed load samplers. Individually they all are adequate bed load measurement instruments - used in combination they are complementing one another, whereas each applied separately leads to specific deficits. The investigation payed special attention on results out of the geophone installations, whereas steel plate vibrations (the plates are mounted on top of concrete structures even with the river bed surface) caused by bed load particles with a diameter larger than about 20 mm are inducing a signal into the geophones. The signal above a defined threshold voltage than is recorded in a computer system as the sum of impacts during one minute intervals. The spatio-temporal distribution of the transported bed load material, its amount and the transport processes itself could be figured out for the first time out of continuous data collection since 2006 for large alpine gravel-bed rivers. Before building up the gauging stations there were no continuous recordings of bed load transport processes in large alpine rivers over their entire cross section, hence the investigation promises a better process understanding and the possibility to determine bed load transport rates and a rough approximation of the grain size distributions of the transported bed load material under different flow conditions. A relation between detected geophone records, the flow discharge and direct bed load sampling methods (Large Helley Smith

  3. OTTO-PAP: An alternative option to the PBMR fuelling philosophy

    International Nuclear Information System (INIS)

    Once Through Then Out, Power Adjusted by Poison (OTTO-PAP) fuelling of a high temperature pebble-bed reactor offers a simple alternative to the MEDUL (Mehrfachdurchlauf = German for multi-pass) fuelling regime followed in pebble bed reactor designs to date. The prerequisite for a modular reactor unit of maximum power output, subject to observing passive safety characteristics is a sufficiently flat axial neutron flux profile. This is achieved by introducing B4C coated particles of pre-calculated size and packing density within the fuel spheres. In accordance with AVR operating practise the temperature profile is radially equalised by introducing a 2-zone core loading. Adding pure graphite spheres loosely into the centre column area of the core effectively reduced the maximum power in the middle. Increasing the reactor diameter is enabled by the introduction of noses. A 3-D geometric modeller developed in cylindrical co-ordinates enables a given flow description of the pebbles adjacent to the nose boundaries and in the vicinity of the shut down/control rods. After translation of the geometric data the neutronic behaviour of the reactor is followed in 3-D by the CITATION code. This study is aimed towards achieving an optimal core layout with a LEU (Low Enriched Uranium) fuel cycle. Physical properties of the OTTO-PAP, 150 MWt reference design is reported, while computations performed observe results obtained by the reference HTR-MODUL design. (author)

  4. Condensation in Nanoporous Packed Beds.

    Science.gov (United States)

    Ally, Javed; Molla, Shahnawaz; Mostowfi, Farshid

    2016-05-10

    In materials with tiny, nanometer-scale pores, liquid condensation is shifted from the bulk saturation pressure observed at larger scales. This effect is called capillary condensation and can block pores, which has major consequences in hydrocarbon production, as well as in fuel cells, catalysis, and powder adhesion. In this study, high pressure nanofluidic condensation studies are performed using propane and carbon dioxide in a colloidal crystal packed bed. Direct visualization allows the extent of condensation to be observed, as well as inference of the pore geometry from Bragg diffraction. We show experimentally that capillary condensation depends on pore geometry and wettability because these factors determine the shape of the menisci that coalesce when pore filling occurs, contrary to the typical assumption that all pore structures can be modeled as cylindrical and perfectly wetting. We also observe capillary condensation at higher pressures than has been done previously, which is important because many applications involving this phenomenon occur well above atmospheric pressure, and there is little, if any, experimental validation of capillary condensation at such pressures, particularly with direct visualization. PMID:27115446

  5. CERTS Microgrid Laboratory Test Bed

    Energy Technology Data Exchange (ETDEWEB)

    Lasseter, R. H.; Eto, J. H.; Schenkman, B.; Stevens, J.; Volkmmer, H.; Klapp, D.; Linton, E.; Hurtado, H.; Roy, J.

    2010-06-08

    CERTS Microgrid concept captures the emerging potential of distributed generation using a system approach. CERTS views generation and associated loads as a subsystem or a 'microgrid'. The sources can operate in parallel to the grid or can operate in island, providing UPS services. The system can disconnect from the utility during large events (i.e. faults, voltage collapses), but may also intentionally disconnect when the quality of power from the grid falls below certain standards. CERTS Microgrid concepts were demonstrated at a full-scale test bed built near Columbus, Ohio and operated by American Electric Power. The testing fully confirmed earlier research that had been conducted initially through analytical simulations, then through laboratory emulations, and finally through factory acceptance testing of individual microgrid components. The islanding and resynchronization method met all Institute of Electrical and Electronics Engineers Standard 1547 and power quality requirements. The electrical protection system was able to distinguish between normal and faulted operation. The controls were found to be robust under all conditions, including difficult motor starts and high impedance faults.

  6. Heat and Mass Transfer Enforcement of Vibrating Fluidized Bed

    Institute of Scientific and Technical Information of China (English)

    ChuZhide; YangJunhong; 等

    1994-01-01

    This paper briefly introduces the development of vibrating fluidized bed at home and abroad,elaborates the vibration properties of vibrating fluidized bed.the fluidizing velocity and pressure drop of the bed layer,it also deduces the non-steady state drying dynamic equations of vibrating fluidized bed,analyzes main factors which influence the drying rate and inquires into drying rules of fixed bed and vibrating fluidized bed.

  7. Paleontologic and stratigraphic relations of phosphate beds in Upper Cretaceous rocks of the Cordillera Oriental, Colombia

    Science.gov (United States)

    Maughan, Edwin K.; Zambrano O., Francisco; Mojica G., Pedro; Abozaglo M., Jacob; Pachon P., Fernando; Duran R., Raul

    1979-01-01

    Phosphorite crops out in the Cordillera Oriental of the Colombian Andes in rocks of Late Cretaceous age as strata composed mostly of pelletal carbonate fluorapatite. One stratum of Santonian age near the base of the Galembo Member of the La Luna Formation crops out at many places in the Departments of Santander and Norte de Santander and may be of commercial grade. This stratum is more than one meter thick at several places near Lebrija and near Sardinata, farther south it is locally one meter thick or more near the base of the Guadalupe Formation in the Department of Boyaca. Other phosphorite beds are found at higher stratigraphic levels in the Galembo Member and the Guadalupe Formation, and at some places these may be commercial also. A stratigraphically lower phosphorite occurs below the Galembo Member in the Capacho Formation (Cenomanian age) in at least one area near the town of San Andres, Santander. A phosphorite or pebbly phosphate conglomerate derived from erosion of the Galembo Member forms the base of the Umir Shale and the equivalent Colon Shale at many places. Deposition of the apatite took place upon the continental shelf in marine water of presumed moderate depth between the Andean geosyncline and near-shore detrital deposits adjacent to the Guayana shield. Preliminary calculations indicate phosphorite reserves of approximately 315 million metric tons in 9 areas, determined from measurements of thickness, length of the outcrop, and by projecting the reserves to a maximum of 1,000 meters down the dip of the strata into the subsurface. Two mines were producing phosphate rock in 1969; one near Turmeque, Boyaca, and the other near Tesalia, Huila.

  8. A PROTOTYPE FOUR INCH SHORT HYDRIDE (FISH) BED AS A REPLACEMENT TRITIUM STORAGE BED

    Energy Technology Data Exchange (ETDEWEB)

    Klein, J.; Estochen, E.; Shanahan, K.; Heung, L.

    2011-02-23

    The Savannah River Site (SRS) tritium facilities have used 1st generation (Gen1) metal hydride storage bed assemblies with process vessels (PVs) fabricated from 3 inch nominal pipe size (NPS) pipe to hold up to 12.6 kg of LaNi{sub 4.25}Al{sub 0.75} metal hydride for tritium gas absorption, storage, and desorption for over 15 years. The 2nd generation (Gen2) of the bed design used the same NPS for the PV, but the added internal components produced a bed nominally 1.2 m long, and presented a significant challenge for heater cartridge replacement in a footprint limited glove-box. A prototype 3rd generation (Gen3) metal hydride storage bed has been designed and fabricated as a replacement candidate for the Gen2 storage bed. The prototype Gen3 bed uses a PV pipe diameter of 4 inch NPS so the bed length can be reduced below 0.7 m to facilitate heater cartridge replacement. For the Gen3 prototype bed, modeling results show increased absorption rates when using hydrides with lower absorption pressures. To improve absorption performance compared to the Gen2 beds, a LaNi{sub 4.15}Al{sub 0.85} material was procured and processed to obtain the desired pressure-composition-temperature (PCT) properties. Other bed design improvements are also presented.

  9. Modelling the bed characteristics in fluidised-beds for top-spray coating processes

    Institute of Scientific and Technical Information of China (English)

    Mike Vanderroost; Frederik Ronsse; Koen Dewettinck; Jan G.Pieters

    2012-01-01

    A particle sub-model describing the bed characteristics of a bubbling fluidised bed is presented.Atomisation air,applied at high pressures via a nozzle positioned above the bed for s pray formation,is incorporated in the model since its presence has a profound influence on the bed characteristics,though the spray itself is not yet considered.A particle sub-model is developed using well-known empirical relations for particle drag force,bubble growth and velocity and particle distribution above the fluidised-bed surface.Simple but effective assumptions and abstractions were made concerning bubble distribution,particle ejection at the bed surface and the behaviour of atomisation air flow upon impacting the surface of a bubbling fluidised bed.The model was shown to be capable of predicting the fluidised bed characteristics in terms of bed heights,voidage distributions and solids volume fractions with good accuracy in less than 5 min of calculation time on a regular desktop PC.It is therefore suitable for incorporation into general process control models aimed at dynamic control for process efficiency and product quality in top-spray fluidised bed coating processes.

  10. Modelling of Devolatilization in Fluidized Bed Combustion

    DEFF Research Database (Denmark)

    Stenseng, Mette; Lin, Weigang; Johnsson, Jan Erik;

    1997-01-01

    A mathematical model is developed to describe the devolatilization process in a circulating fluidized bed combustor. The model is a combination of two submodels: single particle devolatilization and fluid dynamics. The single particle model includes the influence of both chemical kinetics and heat...... of CSTR's and the size and number of CSTR's has been estimated from tracer experiments in an 80 MWth CFB boiler. It was not possible to evaluate the model against experimental data, but the dependence of particle size on the degree of devolatilization in the dense bed agrees qualitative with the expected...... behavior. The model shows that the devolatilization mainly occurs in the dense bed....

  11. Fluidised-bed combustion of gasification residue

    Energy Technology Data Exchange (ETDEWEB)

    Korpela, T.; Kudjoi, A.; Hippinen, I.; Heinolainen, A.; Suominen, M.; Lu Yong [Helsinki Univ. of Technology (Finland). Lab of Energy Economics and Power Plant Engineering

    1996-12-01

    Partial gasification processes have been presented as possibilities for future power production. In the processes, the solid materials removed from a gasifier (i.e. fly ash and bed material) contain unburnt fuel and the fuel conversion is increased by burning this gasification residue either in an atmospheric or a pressurised fluidised-bed. In this project, which is a part of European JOULE 2 EXTENSION research programme, the main research objectives are the behaviour of calcium and sulphur compounds in solids and the emissions of sulphur dioxide and nitrogen oxides (NO{sub x} and N{sub 2}O) in pressurised fluidised-bed combustion of gasification residues. (author)

  12. Bed bug outbreak in a neonatal unit.

    Science.gov (United States)

    Bandyopadhyay, T; Kumar, A; Saili, A

    2015-10-01

    There has been a worldwide increase in bed bug infestations over the last 10-15 years. A major stigma is placed upon the institutions found to be infested. We report our experience with an outbreak of the tropical bed bug, Cimex hemipterus, in a neonatal unit. The outbreak not only affected the admitted newborns and mothers by causing a wide variety of rashes and inducing sleeplessness, but also impinged upon the health professionals and their families by producing similar symptomology. It is important for healthcare providers to be aware of, and for each healthcare facility to have, bed bug prevention and control policies. PMID:25591490

  13. Bed Bug Infestations and Control Practices in China: Implications for Fighting the Global Bed Bug Resurgence

    Directory of Open Access Journals (Sweden)

    Changlu Wang

    2011-04-01

    Full Text Available The bed bug resurgence in North America, Europe, and Australia has elicited interest in investigating the causes of the widespread and increasing infestations and in developing more effective control strategies. In order to extend global perspectives on bed bug management, we reviewed bed bug literature in China by searching five Chinese language electronic databases. We also conducted telephone interviews of 68 pest control firms in two cities during March 2011. In addition, we conducted telephone interviews to 68 pest control companies within two cities in March 2011. Two species of bed bugs (Cimex lectularius L. and Cimex hemipterus (F. are known to occur in China. These were common urban pests before the early1980s. Nationwide “Four-Pest Elimination” campaigns (bed bugs being one of the targeted pests were implemented in China from 1960 to the early 1980s. These campaigns succeeded in the elimination of bed bug infestations in most communities. Commonly used bed bug control methods included applications of hot water, sealing of bed bug harborages, physical removal, and applications of residual insecticides (mainly organophosphate sprays or dusts. Although international and domestic travel has increased rapidly in China over the past decade (2000–2010, there have only been sporadic new infestations reported in recent years. During 1999–2009, all documented bed bug infestations were found in group living facilities (military dormitories, worker dormitories, and prisons, hotels, or trains. One city (Shenzhen city near Hong Kong experienced significantly higher number of bed bug infestations. This city is characterized by a high concentration of migratory factory workers. Current bed bug control practices include educating residents, washing, reducing clutter, putting items under the hot sun in summer, and applying insecticides (pyrethroids or organophosphates. There have not been any studies or reports on bed bug insecticide

  14. AVR-КОНТРОЛЛЕРЫ: РАЗВИТИЕ СЕМЕЙСТВА. ЧАСТЬ 1

    OpenAIRE

    Королев, Николай

    2010-01-01

    С момента начала выпуска в 1998 году микроконтроллеры семейства AVR прошли путь от экзотической новинки до одного из самых популярных семейств на рынке 8-разрядных микроконтроллеров с Flash-памятью на кристалле. Причина популярности — очень удачная архитектура кристалла, недорогие средства отладки, а также достаточно удобная, причем бесплатная, среда программирования AVR Studio. Сегодня микроконтроллеры ATmega и ATtiny можно встретить в самых разнообразных устройствах, начиная от игрушек и за...

  15. PRESSURE FLUCTUATIONS IN GAS-SOLIDS FLUIDIZED BEDS

    Institute of Scientific and Technical Information of China (English)

    Hsiaotao Bi; Aihua Chen

    2003-01-01

    Pressure fluctuation data measured in a series of fluidized beds with diameters of 0.05, 0.1, 0.29, 0.60 and 1.56 m showed that the maximum amplitude or standard deviation increased with increasing the superficial gas velocity and static bed height for relatively shallow beds and became insensitive to the increase in static bed height in relatively deep beds. The amplitude appeared to be less dependent on the measurement location in the dense bed. Predictions based on bubble passage, bubble eruption at the upper bed surface and bed oscillation all failed to explain all observed trends and underestimated the amplitude of pressure fluctuations, suggesting that the global pressure fluctuations in gas-solids bubbling fluidized beds are the superposition of local pressure variations, bed oscillations and pressure waves generated from the bubble formation in the distributor region, bubble coalescence during their rise and bubble eruption at the upper bed surface.

  16. Modular Electric Propulsion Test Bed Aircraft Project

    Data.gov (United States)

    National Aeronautics and Space Administration — An all electric aircraft test bed is proposed to provide a dedicated development environment for the rigorous study and advancement of electrically powered...

  17. Ultra high temperature particle bed reactor design

    Science.gov (United States)

    Lazareth, Otto; Ludewig, Hans; Perkins, K.; Powell, J.

    1990-01-01

    A direct nuclear propulsion engine which could be used for a mission to Mars is designed. The main features of this reactor design are high values for I(sub sp) and very efficient cooling. This particle bed reactor consists of 37 cylindrical fuel elements embedded in a cylinder of beryllium which acts as a moderator and reflector. The fuel consists of a packed bed of spherical fissionable fuel particles. Gaseous H2 passes over the fuel bed, removes the heat, and is exhausted out of the rocket. The design was found to be neutronically critical and to have tolerable heating rates. Therefore, this particle bed reactor design is suitable as a propulsion unit for this mission.

  18. Modular Electric Propulsion Test Bed Aircraft Project

    Data.gov (United States)

    National Aeronautics and Space Administration — A hybrid electric aircraft simulation system and test bed is proposed to provide a dedicated development environment for the rigorous study and advancement of...

  19. IceBridge BedMachine Greenland

    Data.gov (United States)

    National Aeronautics and Space Administration — This data set contains bed topography beneath the Greenland Ice Sheet based on mass conservation derived from airborne radar tracks and satellite radar. The data...

  20. The effect of vibration on bed voidage behaviors in fluidized beds with large particles

    Directory of Open Access Journals (Sweden)

    H. Jin

    2007-09-01

    Full Text Available The effects of vibration parameters, operating conditions and material properties on bed voidage were investigated using an optical fiber probe approach in a vibrating fluidized bed with a diameter of 148 mm. Variables studied included frequency (0-282 s-1, amplitude (0 mm-1 mm, bed height (0.1 m-0.4 m as well as four kinds of particles (belonging to Geldart's B and D groups. The axial and radial voidage distribution with vibration is compared with that without vibration, which shows vibration can aid in the fluidization behaviors of particles. For a larger vibration amplitude, the vibration seriously affects bed voidage. The vibration energy can damp out for particle layers with increasing the bed height. According to analysis of experimental data, an empirical correlation for predicting bed voidage, giving good agreement with the experimental data and a deviation within ±15%, was proposed.

  1. The effect of vibration on bed voidage behaviors in fluidized beds with large particles

    Energy Technology Data Exchange (ETDEWEB)

    Jin, H.; Zhang, J.; Zhang, B.

    2007-07-01

    The effects of vibration parameters, operating conditions and material properties on bed voidage were investigated using an optical fiber probe approach in a vibrating fluidized bed with a diameter of 148 mm. Variables studied included frequency (0-282 s{sup -1}), amplitude (0 mm-1 mm), bed height (0.1 m-0.4 m) as well as four kinds of particles (belonging to Geldart's B and D groups). The axial and radial voidage distribution with vibration is compared with that without vibration, which shows vibration can aid in the fluidization behaviors of particles. For a larger vibration amplitude, the vibration seriously affects bed voidage. The vibration energy can damp out for particle layers with increasing the bed height. According to analysis of experimental data, an empirical correlation for predicting bed voidage, giving good agreement with the experimental data and a deviation within {+-}15%, was proposed. 20 refs., 8 figs., 2 tabs.

  2. Bed dynamics of gas-solid fluidized bed with rod promoter

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    The dynamic characteristics of a gas-solid fluidized bed with different rod promoters have been investigated in terms of bed expansion and fluctuation, minimum fluidization velocity and distributor-to-bed pressure drop ratio at minimum fluidization velocity. Experimentation based on statistical design has been carried out and model equations using factorial design of experiments have been developed for the above mentioned quantities for a promoted gas-solid fluidized bed. The model equations have been tested with additional experimental data. The system variables include four types of rod promoters of varying blockage volume, bed particles of four sizes and four initial static bed heights. A comparison between the predicted values of the output variables using the proposed model equation with their corresponding experimental ones shows fairly good agreement.

  3. Cognitive and emotional functioning in BED

    OpenAIRE

    Kittel, Rebekka; Brauhardt, Anne; Hilbert, Anja

    2016-01-01

    Objective: Binge-eating disorder (BED) is characterized by recurrent episodes of binge eating and is associated with eating disorder and general psychopathology and overweight/obesity. Deficits in cognitive and emotional functioning for eating disorders or obesity have been reported. However, a systematic review on cognitive and emotional functioning for individuals with BED is lacking. Method: A systematic literature search was conducted across three databases (Medline, PubMed, and PsycI...

  4. Suicide following an infestation of bed bugs

    OpenAIRE

    Burrows, Stephanie; Perron, Stéphane; Susser, Stephanie

    2013-01-01

    Patient: Male, 62 Final Diagnosis: Bipolar disorder Symptoms: Bordeline personality disorder Medication: — Clinical Procedure: Bed bug infestation Specialty: Psychiatry Objective: Unusual clinical course Background: In the past decade, bed bug infestations have been increasingly common in high income countries. Psychological consequences of these infestations are rarely examined in the scientific literature. Case Report: We present a case, based on a coroner’s investigation report, of a woman...

  5. Bed Bug Infestations and Control Practices in China: Implications for Fighting the Global Bed Bug Resurgence

    OpenAIRE

    Changlu Wang; Xiujun Wen

    2011-01-01

    The bed bug resurgence in North America, Europe, and Australia has elicited interest in investigating the causes of the widespread and increasing infestations and in developing more effective control strategies. In order to extend global perspectives on bed bug management, we reviewed bed bug literature in China by searching five Chinese language electronic databases. We conducted telephone interviews of staff from 77 Health and Epidemic Prevention Stations in six Chinese cities in November 2...

  6. Investigation of volumetrically heated debris bed quenching

    Energy Technology Data Exchange (ETDEWEB)

    Konovalikhin, M.J.; Sehgal, B.R. [Royal Institute of Technology, Div. of Nuclear Power Safety, Stockholm (Sweden)

    2001-07-01

    A series of experiments were conducted at RIT (Royal Institute of Technology) in which hot homogeneous and stratified particle beds were quenched by establishing a column of water onto the top of the bed and by injection of water from the bottom delivered through downcomers from the water overlayer. For this experimental program the following approach was adopted. Since corium debris have a particle size distribution and are more like sand, the debris beds were built with sand of different particle size distributions, heated with a network of thin heaters, distributed uniformly in the sand bed to produce uniform volumetric heat generation. Low porosity beds were constructed, since they are the most difficult to quench with top flooding. The primary objective was to obtain data, which will provide a phenomenological basis for assessing margins for coolability of a degraded core debris bed in the lower head of an LWR vessel as well as steam generation rate from the interactions between core debris and water. This paper summarizes the experimental results along with related analysis. (authors)

  7. CFD-DEM study of effect of bed thickness for bubbling fluidized beds

    Energy Technology Data Exchange (ETDEWEB)

    Tingwen, Li; Gopalakrishnan, Pradeep; Garg, Rahul; Shahnam, Mehrdad

    2011-10-01

    The effect of bed thickness in rectangular fluidized beds is investigated through the CFD–DEM simulations of small-scale systems. Numerical results are compared for bubbling fluidized beds of various bed thicknesses with respect to particle packing, bed expansion, bubble behavior, solids velocities, and particle kinetic energy. Good two-dimensional (2D) flow behavior is observed in the bed having a thickness of up to 20 particle diameters. However, a strong three-dimensional (3D) flow behavior is observed in beds with a thickness of 40 particle diameters, indicating the transition from 2D flow to 3D flow within the range of 20–40 particle diameters. Comparison of velocity profiles near the walls and at the center of the bed shows significant impact of the front and back walls on the flow hydrodynamics of pseudo-2D fluidized beds. Hence, for quantitative comparison with experiments in pseudo-2D columns, the effect of walls has to be accounted for in numerical simulations.

  8. WTP Pretreatment Facility Potential Design Deficiencies--Sliding Bed and Sliding Bed Erosion Assessment

    Energy Technology Data Exchange (ETDEWEB)

    Hansen, E. K. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL)

    2015-05-06

    This assessment is based on readily available literature and discusses both Newtonian and non-Newtonian slurries with respect to sliding beds and erosion due to sliding beds. This report does not quantify the size of the sliding beds or erosion rates due to sliding beds, but only assesses if they could be present. This assessment addresses process pipelines in the Pretreatment (PT) facility and the high level waste (HLW) transfer lines leaving the PT facility to the HLW vitrification facility concentrate receipt vessel.

  9. CFD-DEM study of effect of bed thickness for bubbling fluidized beds

    Institute of Scientific and Technical Information of China (English)

    Tingwen Li; Pradeep Gopalakrishnana; Rahul Garg; Mehrdad Shahnam

    2012-01-01

    The effect of bed thickness in rectangular fluidized beds is investigated through the CFD-DEM simulations of small-scale systems.Numerical results are compared for bubbling fluidized beds of various bed thicknesses with respect to particle packing,bed expansion,bubble behavior,solids velocities,and particle kinetic energy.Good two-dimensional (2D) flow behavior is observed in the bed having a thickness of up to 20 particle diameters.However,a strong three-dimensional (3D) flow behavior is observed in beds with a thickness of 40 particle diameters,indicating the transition from 2D flow to 3D flow within the range of 20-40 particle diameters.Comparison of velocity profiles near the walls and at the center of the bed shows significant impact of the front and back walls on the flow hydrodynamics of pseudo-2D fluidized beds.Hence,for quantitative comparison with experiments in pseudo-2D columns,the effect of wails has to be accounted for in numerical simulations.

  10. 21 CFR 880.5140 - Pediatric hospital bed.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Pediatric hospital bed. 880.5140 Section 880.5140... Devices § 880.5140 Pediatric hospital bed. (a) Identification. A pediatric hospital bed is a device intended for medical purposes that consists of a bed or crib designed for the use of a pediatric...

  11. 21 CFR 880.5110 - Hydraulic adjustable hospital bed.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Hydraulic adjustable hospital bed. 880.5110... Therapeutic Devices § 880.5110 Hydraulic adjustable hospital bed. (a) Identification. A hydraulic adjustable hospital bed is a device intended for medical purposes that consists of a bed with a hydraulic...

  12. 21 CFR 892.1350 - Nuclear scanning bed.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Nuclear scanning bed. 892.1350 Section 892.1350...) MEDICAL DEVICES RADIOLOGY DEVICES Diagnostic Devices § 892.1350 Nuclear scanning bed. (a) Identification. A nuclear scanning bed is an adjustable bed intended to support a patient during a nuclear...

  13. 21 CFR 880.5120 - Manual adjustable hospital bed.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Manual adjustable hospital bed. 880.5120 Section... Therapeutic Devices § 880.5120 Manual adjustable hospital bed. (a) Identification. A manual adjustable hospital bed is a device intended for medical purposes that consists of a bed with a manual...

  14. Bed and breakfasts in Virginia :identification and success factors

    OpenAIRE

    Kaufman, Tammie J

    1994-01-01

    Virginia bed and breakfast operations were researched in order to determine the attitudes/beliefs which were necessary for success in the bed and breakfast industry. The objectives of the study were to: (1) identify demographics of Virginia bed and breakfast operations; (2) identify successful bed and breakfast operations based upon their self definition of success; (3) identify the attitudes and beliefs operators believe are necessary for success in running a bed and breakf...

  15. Experiments on the dryout behavior of stratified debris beds

    Energy Technology Data Exchange (ETDEWEB)

    Leininger, Simon; Kulenovic, Rudi; Laurien, Eckart [Stuttgart Univ. (Germany). Inst. of Nuclear Technology and Energy Systems (IKE)

    2015-10-15

    In case of a severe accident with loss of coolant and core meltdown a particle bed (debris) can be formed. The removal of decay heat from the debris bed is of prime importance for the bed's long-term coolability to guarantee the integrity of the RPV. In contrast to previous experiments, the focus is on stratified beds. The experiments have pointed out that the bed's coolability is significantly affected.

  16. NONUNIFORM OPEN CHANNEL FLOW WITH UPWARD SEEPAGE THROUGH LOOSE BEDS

    Institute of Scientific and Technical Information of China (English)

    Subhasish DEY

    2003-01-01

    The Reynolds stress and bed shear stress are important parameters in fluvial hydraulics. Steadynonuniform flow in open channels with streamwise sloping beds having upward seepage through loose beds is theoretically analyzed to estimate the Reynolds stress and bed shear stress. Equations of the Reynolds stress and bed shear stress are developed, assuming a modified logarithmic velocity distribution law due to upward seepage, and using the Reynolds and continuity equations of twodimensional flow in open channels.

  17. Theoretical comparison of packed bed and fluidized bed membrane reactors for methane reforming

    NARCIS (Netherlands)

    Gallucci, Fausto; Sint Annaland, van Martin; Kuipers, J.A.M.

    2010-01-01

    In this theoretical work the performance of different membrane reactor concepts, both fluidized bed and packed bed membrane reactors, has been compared for ultra-pure hydrogen production via methane reforming. Using detailed theoretical models, the required membrane area to reach a given conversion

  18. Fluidized-bed and packed-bed characteristics of gel beads

    NARCIS (Netherlands)

    Zessen, van E.; Tramper, J.; Rinzema, A.; Beeftink, H.H.

    2005-01-01

    A liquid-fluidized bed or packed bed with gel beads is attractive as an immobilized-cell bioreactor. The performance of such bioreactors is influenced by the physical behavior of these beads. Three different but related aspects involving the drag force between particles and liquid were studied for f

  19. The thermal conductivity of beds of spheres

    Energy Technology Data Exchange (ETDEWEB)

    McElroy, D.L.; Weaver, F.J.; Shapiro, M.; Longest, A.W.; Yarbrough, D.W.

    1987-01-01

    The thermal conductivities (k) of beds of solid and hollow microspheres were measured using two radial heat flow techniques. One technique provided k-data at 300 K for beds with the void spaces between particles filled with argon, nitrogen, or helium from 5 kPa to 30 MPa. The other technique provided k-data with air at atmospheric pressure from 300 to 1000 K. The 300 K technique was used to study bed systems with high k-values that can be varied by changing the gas type and gas pressure. Such systems can be used to control the operating temperature of an irradiation capsule. The systems studied included beds of 500 ..mu..m dia solid Al/sub 2/O/sub 3/, the same Al/sub 2/O/sub 3/ spheres mixed with spheres of silica--alumina or with SiC shards, carbon spheres, and nickel spheres. Both techniques were used to determine the k-value of beds of hollow spheres with solid shells of Al/sub 2/O/sub 3/, Al/sub 2/O/sub 3//center dot/7 w/o Cr/sub 2/O/sub 3/, and partially stabilized ZrO/sub 2/. The hollow microspheres had diameters from 2100 to 3500 ..mu..m and wall thicknesses from 80 to 160 ..mu..m. 12 refs., 7 figs., 4 tabs.

  20. Nonlinear Mechanism of Bed Load Transport

    Institute of Scientific and Technical Information of China (English)

    XU Haijue; BAI Yuchuan; NG Chiu-On

    2009-01-01

    From the group movement of the bed load within the bottom layer, details of the nonlinear dynamic characteristics of bed load movement are discussed in this paper. Whether the sediment is initiated into motion cor-responds to whether the constant term in the equation is equal to zero. If constant term is zero and no dispersive force is considered, the equation represents the traditional Shields initiation curve, and if constant term is zero with-out the dispersive force being considered, then a new Shields curve which is much lower than the traditional one is got, The fixed point of the equation corresponds to the equilibrium sediment transport of bed load. In the mutation analysis, we have found that the inflection point is the demarcation point of breaking. In theory, the breaking point corresponds to the dividing boundary line, across which the bed form changes from flat bed to sand ripple or sand dune. Compared with the experimental data of Chatou Hydraulic Lab in France, the conclusions are verified.