# Showing papers in "Nuclear Science and Engineering in 1988"

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TL;DR: An overview of the main methods used in the code for (a) multidimensional collision probability calculations, (b) leakage calculations, and (c) homogenization procedures is given.

Abstract: APOLLO II is a new, multigroup transport code under development at the Commissariat a I’Energie Atomique. The code has a modular structure and uses sophisticated software for data structuralization...

168 citations

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TL;DR: In this paper, the DORT Two-Dimensional Discrete Ordinates Transport Code (DORT-TOC) has been proposed for two-dimensional discrete ordinates transport codes.

Abstract: (1988). The DORT Two-Dimensional Discrete Ordinates Transport Code. Nuclear Science and Engineering: Vol. 99, No. 1, pp. 88-89.

159 citations

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TL;DR: The Integral Fast Reactor concept employs a pool layout, a uranium-plutonium-zirconium metal alloy fuel, and a closed fuel cycle based on pyrometallurgical reprocessing and injection casting refabr...

Abstract: The Integral Fast Reactor concept employs a pool layout, a uranium-plutonium-zirconium metal alloy fuel, and a closed fuel cycle based on pyrometallurgical reprocessing and injection casting refabr...

108 citations

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TL;DR: A reliability analysis methodology, GO-FLOW, is presented and detailed explanations and two examples of GO- FLOW analysis are given.

Abstract: A reliability analysis methodology, GO-FLOW, is presented. Detailed explanations and two examples of GO-FLOW analysis are given.The GO-FLOW is a success-oriented system analysis technique. The mode...

97 citations

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TL;DR: A general order, general dimensionality nodal transport method cast in a simple, compact, singleweight, weighted diamond-difference form is derived and is a consistently formulated nodal method, which can be solved using either the discrete nodal-transport method or the nodsal-equivalent finite difference algorithms without any approximations.

Abstract: Very high computational efficiencies have been achieved recently by introducing higher order approximations to nodal formalisms for the discrete ordinates, neutron transport equation. However, the ...

71 citations

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TL;DR: In this paper, a model for small-scale single droplet fuel/coolant interactions (FCIs) is proposed, which considers the growth of a coolant vapor/liquid interfacial disturbance into a cooledant liquid jet during the flight.

Abstract: A model for small-scale single droplet fuel/coolant interactions (FCIs) is proposed, which considers the growth of a coolant vapor/liquid interfacial disturbance into a coolant liquid jet during th...

70 citations

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TL;DR: In this paper, an interpolation of buildup factors for an arbitrary elemental material is examined using geometric-progression (G-P) parameters for an equivalent atomic number for a specific energy above KAPPA edges and penetration distance vary smoothly with respect to atomic number.

Abstract: The values of buildup factors for a specific energy above KAPPA edges and penetration distance vary smoothly with respect to atomic number. An interpolation of buildup factors for an arbitrary elemental material is examined using geometric-progression (G-P) parameters for an equivalent atomic number. The G-P parameters are data fitted to the proposed American National Standard Buildup factor data compilation of 17 elements from beryllium to molybdenum and are calculated by the moments method.

58 citations

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TL;DR: In this article, natural circulation experiments were conducted in a large-scale (scale in volume) full-height simulator of a Westinghouse-type pressurized water reactor with two steam generators.

Abstract: Natural circulation experiments were conducted in a large-scale ( scale in volume) full-height simulator of a Westinghouse-type pressurized water reactor. This facility has two steam generators eac...

56 citations

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TL;DR: Motivated by the enhancement of heat transfer under oscillating flow conditions in single-phase heated channels and by stability problems in two-phase systems such as those in boiling water reactor, the work in this paper was proposed.

Abstract: Motivated by the enhancement of heat transfer under oscillating flow conditions in single-phase heated channels and by stability problems in two-phase systems such as those in boiling water reactor...

53 citations

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TL;DR: Three previously derived approximations to the linear-linear nodal transport method are reexamined, together with a new approximation that takes into account the bilinear nodal flux moment and are found to have comparable accuracies for the problems studies, especially on meshesmore that are sufficiently fine.

Abstract: Two previously derived approximations to the linear-linear nodal transport method, the linear-nodal (LN) and the linear-linear (LL) methods, are reexamined, together with a new approximation, the bilinear (BL) method, that takes into account the bilinear nodal flux moment. The three methods differ in the degree of analyticity retained in the final discrete variable equations; however, they all possess the very high accuracy characteristic of nodal methods. Unlike previous work, the final equations are manipulated and cast in the form of the classical weighted diamond-difference (WDD) equations (not just a WDD algorithm). This makes them simple to implement in a computer code, especially for those users who have experience with WDD algorithms. Other algorithms, such as the nodal algorithm, also can be used to solve the WDD-form equations. A computer program that solves two-dimensional transport problems using the LN, LL, or the BL method is used to solve three test problems. The results are used to confirm our algebraic manipulations of the nodal equations and also to compare the performance of the three methods from the computational, as well as the theoretical, point of view. The three methods are found to have comparable accuracies for the problems studies, especially on meshesmore » that are sufficiently fine.« less

33 citations

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TL;DR: The effects of including incoherent and coherent scattering in a calculation of the exposure buildup factors for plane normal gamma-ray sources have been investigated by using an electron-gamma-ray shower Monte Carlo code, EGS4, for water, iron and lead in the 40- to 200-keV range.

Abstract: The effects of including incoherent and coherent scattering in a calculation of the exposure buildup factors for plane normal gamma-ray sources have been investigated by using an electron-gamma-ray shower Monte Carlo code, EGS4, for water, iron, and lead in the 40- to 200-keV range The ''true'' buildup factors for practical uses are defined to clarify the effects of bound-electron Compton (incoherent) and coherent scattering and are tabulated for penetration depths up to 10 mfp The pseudo buildup factor increases by including incoherent scattering and decreases by including coherent scattering The degree of each effect varies with the atomic number of the material The effect of incoherent scattering is large for materials of small atomic number, and the effect of coherent scattering is large for materials of large atomic number

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TL;DR: A computerized heuristic search method for the generation and optimization of fuel reload configurations is proposed and investigated and the heuristic knowledge is expressed modularly in the form of ''IF-THEN'' production rules.

Abstract: A computerized heuristic search method for the generation and optimization of fuel reload configurations is proposed and investigated. The heuristic knowledge is expressed modularly in the form of ''IF-THEN'' production rules. The method was implemented in a program coded in the Franz LISP programming language and executed under the UNIX operating system. A test problem was formulated, based on a typical light water reactor reload problem with a few simplifications assumed, in order to allow formulation of the reload strategy into a relatively small number of rules. A computer run of the problem was performed with a VAX-780 machine. A set of 312 solutions was generated in -- 20 min of execution time. Testing of a few arbitrarily chosen configurations demonstrated reasonably good performance for the computer-generated solutions. A computerized generator of reload configurations may be used for the fast generation or modification of reload patterns and as a tool for the formulation, tuning, and testing of the heuristic knowledge rules used by an ''expert'' fuel manager.

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TL;DR: In this paper, two new low-and high-order nodal-integral methods have been developed and applied to both incompressible fluid flow and natural convection, respectively.

Abstract: Two new “low-” and “high-order” time-dependent nodal-integral methods were developed and applied to both incompressible fluid flow and natural convection. These new methods have a high level of acc...

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TL;DR: In this article, a self-consistent nodal method was developed that directly computes the in-node flux shapes, which rendered the use of an approximation for the transverse leakages no longer necessary.

Abstract: A self-consistent nodal method has been developed that directly computes the in-node flux shapes. The method renders the use of an approximation for the transverse leakages no longer necessary. The...

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TL;DR: The authors present a class of acceleration methods that can be applied to transport problems, regardless of geometry, mesh shape, or discretization scheme and show that the simplest methods in this class are stable and effective.

Abstract: A new class of synthetic acceleration methods, which can be applied to transport calculations regardless of geometry, discretization scheme, or mesh shape, is presented. Unlike other synthetic acce...

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TL;DR: In this article, the generalized perturbation theory was developed to accommodate constant power core depletion and the resulting adjoint equations are distinguished from the corresponding constant flux depletion system by the coupling of adjacent time intervals in the source of the generalized adjoint flux equation.

Abstract: The generalized perturbation theory was developed to accommodate constant power core depletion. The resulting adjoint equations are distinguished from the corresponding constant flux depletion system by the coupling of adjacent time intervals in the source of the generalized adjoint flux equation. The method is demonstrated first with an analytic solution to an infinite medium problem. A system of numerical equations is then formulated to be consistent with the number density iteration scheme used to simulate constant power depletion in the code REBUS at Argonne National Laboratory. A two-dimensional (R-Z) fast reactor example similar to that used by previous authors for constant flux depletion is solved here to provide a consistent basis for evaluating the present work. The sensitivity coefficients predicted by constant power depletion perturbation theory are consistently within a few percent of the exact calculation.

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TL;DR: In this paper, it is shown how highly accurate results can be obtained by using trial functions based on the eigenfunctions of the relevant integrodifferential equations, such choices of trial functions should apply equally effectively to problems in curved geometries.

Abstract: In several problems of particle transport, quantities of macroscopic interest can be related to stationary values of variational functionals based on general integro-differential equations and boundary conditions. Within the context of the jump (Milne's) problem, it is shown how highly accurate results can be obtained by using trial functions based on the eigenfunctions of the relevant integrodifferential equations. Such choices of trial functions should apply equally effectively to problems in curved geometries, both internal and external.

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TL;DR: An implementation of Wielandt's method of eigenvalue shifting to accelerate the convergence of nodal expansion method (NEM) reactor calculations is presented in this paper, where a particular formulation of the met...

Abstract: An implementation of Wielandt’s method of eigenvalue shifting to accelerate the convergence of nodal expansion method (NEM) reactor calculations is presented. This particular formulation of the met...

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TL;DR: In this article, the prompt neutron emission multiplicity distribution and its average value were determined at the standard neutron energy of 0.0253 eV for the neutron-induced fission of...

Abstract: The prompt neutron emission multiplicity distribution Pv and its average value 〈v〉 (i.e., nubar) have been determined at the standard neutron energy of 0.0253 eV for the neutron-induced fission of ...

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TL;DR: In this article, the average number of prompt neutrons emitted per fission event has been evaluated for 239Pu with a special emphasis on the fluctuations experimentally observed in the low-energy range.

Abstract: The average number of prompt neutrons p emitted per fission event has been evaluated for 239Pu with a special emphasis on the fluctuations experimentally observed in the low-energy range. These fluctuations have a significant impact on applications, especially the reactivity coefficient of advanced water reactors. Consequently, the p curve has to be defined in the same fine energy mesh as the fission cross section for accurate neutron source calculations. In this range, formalisms are proposed to calculate p from the resonance parameters, resolved or averaged. Using the JEF-1 library as a data base, an analysis of several thermal, low-moderated, or fast systems shows a good convergence of the selected microscopic and integral information.

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TL;DR: It is concluded that, at least in this particular application, the approximations used in the model were allowable in a case of practical interest.

Abstract: In the first two papers of this series, a complete algorithm was elaborated and tested for the diagnostics of vibrating control rods in pressurized water reactors (PWRs). Although the method was thoroughly tested in numerical experiments where even the effects of background noise were accounted for, the influence of the several approximations regarding the underlying neutron physical and mechanical model of the applicability of the method in real applications could not be properly estimated. In August 1985, in-core self-powered neutron detector spectra taken at Paks-2, a PWR in Hungary, indicated the presence of an excessively vibrating control rod. With these measured noise data as input, the previously reported localization algorithm was applied in its original form. The algorithm singled out one control rod out of the possible seven, and independent investigations performed before and during the subsequent refueling showed the correctness of the localization results. It is therefore concluded that, at least in this particular application, the approximations used in the model were allowable in a case of practical interest. The algorithm was developed further to facilitate the automatization and reliability of the localization procedure. These developments and the experiences in the application of the algorithm are reported in thismore » paper.« less

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TL;DR: A successful hardware/software demonstrator has been introduced, paving the way for development of a broadly expert system program that would provide a directed path for solving the low-leakage problem.

Abstract: The fuel shuffling problem is posed by the need to reposition partially burned assemblies to achieve minimum X-Y pin power peaks reload cycles of pressurized water reactors. This problem is a classic artificial intelligence (AI) problem and is highly suitable for AI expert system solution assistance, in contrast to the conventional solution, which ultimately depends solely on trial and error. Such a fuel shuffling assistant would significantly reduce engineering and computer execution time for conventional loading patterns and, much more importantly, even more significantly for low-leakage loading patterns. A successful hardware/software demonstrator has been introduced, paving the way for development of a broadly expert system program. Such a program, upon incorporating the recently developed technique perverse depletion, would provide a directed path for solving the low-leakage problem.

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TL;DR: The QPANDA nodal models have been extensively tested and benchmarked in the SIMULATE-3 code as discussed by the authors, and they have been shown to have a high degree of accuracy with which power distributions are predicted.

Abstract: The QPANDA nodal models, which are embodied in the SIMULATE-3 code have been extensively tested and benchmarked. Comparisons to quarter-core PDQ depletion calculations demonstrate the high degree of accuracy with which power distributions are predicted. Even though SIMULATE-3 contains no user-adjusted normalizations. The QPANDA pin power reconstruction model is introduced, and comparisons (versus CASMO colorset and PDQ quarter-core calculations) demonstrate that accurate pin power distributions are obtained by modulating the intranodal power distributions with single-assembly CASMO pin power distributions. Comparisons of SIMULATE-3 calculations to measured reactor fission rate integrals are presented. Also, the overall accuracy of the CASMO-3 cross sections, the QPANDA nodal model, and the QPANDA pin power reconstruction model is demonstrated.

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TL;DR: In this article, a consistently formulated differencing approach is applied to the diffusion-synthetic acceleration of discrete ordinates calculations based on various spatial differenced schemes and the diffusion coupling equations derived for each scheme are contrasted to conventional coupling relations and are shown to permit derivation of either point- or box-centered diffusion difference equations.

Abstract: A consistently formulated differencing approach is applied to the diffusion-synthetic acceleration of discrete ordinates calculations based on various spatial differencing schemes. The diffusion ''coupling'' equations derived for each scheme are contrasted to conventional coupling relations and are shown to permit derivation of either point- or box-centered diffusion difference equations. The resulting difference equations are shown to be mathematically equivalent, in slab geometry, to equations derived by applying Larsen's four-step procedure to the S/sub 2/ equations. Fourier stability analysis of the acceleration method applied to slab model problems is used to demonstrate that, for any S/sub n/ differencing scheme (a) the upper bound on the spectral radius of the method occurs in the fine-mesh limit and equals that of the spatially continuous case (0.22466), and (b) the spectral radius decreases with increasing mesh size to an asymptotic value <0.13135. This model problem performance is somewhat superior to that of Larsen's approach, for which the spectral radius is bounded by 0.25 in the wide-mesh limit. Numerical results of multidimensional, heterogeneous, scattering-dominated problems are also presented to demonstrate the rapid convergence of accelerated discrete ordinates calculations using various spatial differencing schemes.

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TL;DR: The isomer 242mAm with a half-life of 141 yr was obtained from an (n, γ) capture reaction with 241 Am as mentioned in this paper, which is a decay product of 241Pu.

Abstract: The isomer 242mAm with a half-life of 141 yr is obtained from an (n, γ) capture reaction with 241 Am. The latter is a decay product of 241Pu. The isomer 242mAm has the highest known thermal fission...

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TL;DR: In this paper, a new direction-basing approach to a target point and to finite detectors for Monte Carlo simulation is developed, presented, and tested, which properly accounts for the weight adjustments that must be made for the combined choice of a particular scattering (polar) and rotational (azimuthal) angle to obtain a given biasing angle about either target point or a finite detector.

Abstract: In this paper a new direction biasing approach to a target point and to finite detectors for Monte Carlo simulation is developed, presented, and tested. It properly accounts for the weight adjustments that must be made for the combined choice of a particular scattering (polar) and rotational (azimuthal) angle to obtain a given biasing angle about either a target point or a finite detector. Sample Monte Carlo simulations for a neutron transport problem with isotropic center-of-mass scattering and a gamma-ray transport problem with Klein-Nishina scattering have been done by both the analog and new direction biasing methods. The results indicate that the direction biasing approach is valid and will be very efficient for deep-penetration problems of these two types.

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TL;DR: In this paper, both experimental and analytical studies have been performed on the temperature coefficient of reactivity in a light water moderated and reflected core loaded with highly enriched uranium fuel at t

Abstract: Both experimental and analytical studies have been performed on the temperature coefficient of reactivity in a light water moderated and reflected core loaded with highly enriched uranium fuel at t...

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TL;DR: In this paper, an improved method for calculating the total probability of particle scattering within the solid angle subtended by finite detectors is developed, presented, and tested, where the limiting polar and azimuthal angles are measured from the direction that most simplifies their calculation rather than from the incident particle direction.

Abstract: An improved method for calculating the total probability of particle scattering within the solid angle subtended by finite detectors is developed, presented, and tested. The limiting polar and azimuthal angles subtended by the detector are measured from the direction that most simplifies their calculation rather than from the incident particle direction. A transformation of the particle scattering probability distribution function (pdf) is made to match the transformation of the direction from which the limiting angles are measured. The particle scattering probability to the detector is estimated by evaluating the integral of the transformed pdf over the range of the limiting angles measured from the preferred direction. A general formula for transforming the particle scattering pdf is derived from basic principles and applied to four important scattering pdf's; namely, isotropic scattering in the Lab system, isotropic neutron scattering in the center-of-mass system, thermal neutron scattering by the free gas model, and gamma-ray Klein-Nishina scattering. Some approximations have been made to these pdf's to enable analytical evaluations of the final integrals. These approximations are shown to be valid over a wide range of energies and for most elements. The particle scattering probability to spherical, planar circular, and right circular cylindrical detectors hasmore » been calculated using the new and previously reported direct approach. Results indicate that the new approach is valid and is computationally faster by orders of magnitude.« less

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TL;DR: In this article, the reactive constraint approach is described and demonstrated to be an effective and reliable means for the automatic control of power in nuclear reactors, which functions by restricti cation.

Abstract: The “reactivity constraint approach” is described and demonstrated to be an effective and reliable means for the automatic control of power in nuclear reactors. This approach functions by restricti...

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TL;DR: SMART as mentioned in this paper is a scattering matrix designed to eliminate angular and possible energy discretization errors without resorting to negative matrix elements, and it has been used in one-dimensional streaming ray and two-dimensional S/sub N/ codes in lieu of Fokker-Planck or extended transport correction techniques.

Abstract: SMART (simulation of many accumulative Rutherford trajectories) scattering theory is based on a scattering matrix designed to eliminate angular and possible energy discretization errors. This is done without resorting to negative matrix elements. In effect, the true scattering law is replaced by one with fewer collisions but larger deflections per collision. The two scattering laws are equivalent, at least in space-independent calculations. To the extent that this equivalence holds true for space-dependent problems, the major numerical obstacle to electron transport modeling is removed. SMART scattering theory has been used in one-dimensional streaming ray and two-dimensional S/sub N/ codes in lieu of Fokker-Planck or extended transport correction techniques, and in a one-dimensional discrete angle Monte Carlo code in place of the condensed history approach. Excellent results have been obtained.