摘要:

AbstractNatural 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 each containing 141 full-size U-tubes of 9 different heights. Transition of the natural circulation mode was observed in the experiments as the primary side mass inventory was decreased. Three major circulation modes were observed: single-phase liquid natural circulation, two-phase natural circulation, and reflux condensation. For all these circulation modes, and during the transitions between the modes, the mass flow distribution among the steam generator U-tubes was significantly nonuniform. The longer U-tubes indicated reversed flow at higher primary side mass inventories and also tended to empty earlier than the shorter U-tubes when the primary side mass inventory was decreased.

ISSN:0029-5639    

DOI:10.13182/NSE99-289

出版商:Taylor&Francis    

年代:1988

数据来源: Taylor

摘要:

AbstractUsing the substitution method combined with the pulsed neutron technique, coolant void reactivities of PuO2-UO2fuel lattices in pressure-tube-type heavy water reactors have been determined as functions of PuO2enrichment in PuO2-UO2(0.54 and 0.87 wt%), fissile content of plutonium (91 and 75% fissile plutonium), lattice pitch (Vm/Vf: 7.4 and 9.9), and coolant void fraction (0, 30, 70, 87, and 100%). The reference loading of 1.2 wt% enriched UO2clusters was progressively replaced by PuO2-UO2test clusters.The void reactivities were obtained from Simmons and King’s formula in which correction was made for a change of the prompt generation time. As decay constants can be maintained invariable due to substitution, buckling differences were analyzed by the first-order perturbation method, on the assumption that lattices are homogeneous and no difference in diffusion coefficients exists between the two lattices.Void reactivities of test lattices were determined with an accuracy of∼10% when the minimum number of test fuel clusters was∼5% of the total. The void reactivity shifted farther to the negative side as the proportion of fissile plutonium was increasingly in the PuO2-UO2fuel of the same enrichment of plutonium.

ISSN:0029-5639    

DOI:10.13182/NSE88-A23560

出版商:Taylor&Francis    

年代:1988

数据来源: Taylor

摘要:

AbstractIn 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 this paper.

ISSN:0029-5639    

DOI:10.13182/NSE88-A23561

出版商:Taylor&Francis    

年代:1988

数据来源: Taylor

摘要:

AbstractA systematic and automated approach for biasing Monte Carlo shielding calculations is described. In particular, adjoint fluxes from a one-dimensional discrete ordinates calculation are used to generate biasing parameters for a Monte Carlo calculation. The entire procedure of adjoint calculation, biasing parameters generation, and Monte Carlo calculation has been automated.The automated biasing procedure has been applied to several realistic deep-penetration shipping cask problems. The results obtained for neutron and gamma-ray transport indicate that with the automated biasing procedure Monte Carlo shielding calculations of spent-fuel casks can be easily performed with minimum effort and that accurate results can be obtained at reasonable computing cost.

ISSN:0029-5639    

DOI:10.13182/NSE88-A23562

出版商:Taylor&Francis    

年代:1988

数据来源: Taylor

摘要:

AbstractA 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.

ISSN:0029-5639    

DOI:10.13182/NSE88-A23563

出版商:Taylor&Francis    

年代:1988

数据来源: Taylor

摘要:

AbstractThe 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.

ISSN:0029-5639    

DOI:10.13182/NSE99-353

出版商:Taylor&Francis    

年代:1988

数据来源: Taylor

摘要:

AbstractOn the basis of an evaporation model in which preequilibrium emission is considered under some approximations, analytical expressions including two adjustable parameters for excitation function of (n, charged-particle) reactions have been derived. Fitting these expressions to the available measured data, these parameters have been extracted and the systematic behavior of the parameters has been studied.

ISSN:0029-5639    

DOI:10.13182/NSE88-A23565

出版商:Taylor&Francis    

年代:1988

数据来源: Taylor

摘要:

AbstractThe average number of prompt neutronspemitted per fission event has been evaluated for239Pu 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, thepcurve 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 calculatepfrom 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.

ISSN:0029-5639    

DOI:10.13182/NSE88-A23566

出版商:Taylor&Francis    

年代:1988

数据来源: Taylor

摘要:

AbstractThe radiolytic gas production rate in boiling water reactors has been reevaluated. The results of recent measurements of the dissolved gases in the main steam samples agree very well with the average production rate measured from the off-gas samples. The best estimate total gas (H2and O2) production rate is 19.3±0.06 cm3/s-MW(thermal)−1, and the average O2content in steam is 17.5 ppm. The observed G(H2) and G(O2) values in the reactor core are estimated to be 0.24 and 0.12 molecule/100 eV, respectively.

ISSN:0029-5639    

DOI:10.13182/NSE88-A23567

出版商:Taylor&Francis    

年代:1988

数据来源: Taylor