摘要:

AbstractA pattern recognition algorithm has been developed for systematic generation of shallow knowledge for nuclear power plant transient diagnostics. The algorithm involves feature selection and pattern discovery. The selection of N best features is attained by discarding redundant and nondiscriminatory features. An entropy minimax algorithm is used to discover the patterns by searching an N-dimensional feature space, populated with transient events of the data base, to locate subspaces that discriminate among the event classes. These patterns are then represented as production rules for diagnostics. A series of approximations have been implemented in the algorithm to handle the discovery of patterns in multidimensional space. We have also developed a perturbation algorithm within the entropy minimax framework to update the patterns in an incremental fashion as new data are obtained. The Midland Nuclear Power Plant Unit 2 simulator is used to generate 144 single-failure events. Based on these events, 25 production rules are generated, representing a two-level hierarchical knowledge structure of single-failure events along the critical safety function approach. These rules represent the common characteristics of time-varying features over the diagnostic time, thereby providing diagnostic capability at any time during the transient.

ISSN:0029-5639    

DOI:10.13182/NSE91-A23793

出版商:Taylor&Francis    

年代:1991

数据来源: Taylor

摘要:

AbstractThe transport and release of radioactive fission products in nuclear fuels are described with detailed reaction-rate equations including intragranular precipitation, radiation re-solution, biased diffusion, and nuclear transmutations. An analytical procedure is found to solve these equations that makes it possible to calculate the release and redistribution of the radionuclides with greater accuracy and with much more speed than conventional numerical methods.The method was implemented in the computer code MITRA for the calculation of the radionuclide behavior during stationary and nonstationary reactor operating conditions. The structure of this code is described, and recalculations of experiments are presented. The analytical solutions of the rate equations are reported in the Appendix.

ISSN:0029-5639    

DOI:10.13182/NSE91-A23794

出版商:Taylor&Francis    

年代:1991

数据来源: Taylor

摘要:

AbstractAn angular multigrid method for the Snequations has been developed that is much more effective for highly forward-peaked scattering than the diffusion synthetic acceleration (DSA) method. Only one-dimensional slab geometry is considered in this study, but it appears that this method can be generalized to curvilinear and multidimensional geometries. The new method is derived, theoretically analyzed, and computationally tested. The angular multigrid method costs only about twice as much as the DSA method, but it gives a spectral radius of 0.6 in the asymptotic forward-peaked Fokker-Planck scattering limit, whereas the diffusion synthetic method gives a spectral radius of unity.

ISSN:0029-5639    

DOI:10.13182/NSE91-A23795

出版商:Taylor&Francis    

年代:1991

数据来源: Taylor

摘要:

AbstractThe monoenergetic transport equation with isotropic scattering and vacuum boundary conditions is applied to two-media spherical and plane systems. The mean-free-path is assumed to be the same even though the multiplication factors are different in both media. The two coupled integral equations that are obtained are numerically solved using the spatial Legendre polynomial method (Carlvik’s method). Tables of seven or more eigenvalues for various dimensions of the bodies are given, and the first five flux modes for some cases are plotted. In addition, for homogeneous systems, we present more accurate and higher eigenvalues than those thus far known.

ISSN:0029-5639    

DOI:10.13182/NSE91-A23796

出版商:Taylor&Francis    

年代:1991

数据来源: Taylor

摘要:

AbstractThe variance of the calculation is minimized on the basis of parameters generated by a learning technique. The optimum is obtained if sampling is biased proportionally to the expected root-mean-square score. The method is compared with existing methods, which bias proportionally to the expected score.

ISSN:0029-5639    

DOI:10.13182/NSE91-A23797

出版商:Taylor&Francis    

年代:1991

数据来源: Taylor

摘要:

AbstractCross sections and spectra for the (n,xp) and (n,xα) reactions on targets of54Fe and56Fe are measured at 8-, 9.5-, and 11-MeV bombarding energies. The bulk of the spectra appears to be the result of compound nuclear reactions, based on their angular and emission energy dependence. A single set of level density parameters is deduced which fits not only these data but also the data recently obtained at 15 MeV. Very small (n,d) cross sections are found in this energy region.

ISSN:0029-5639    

DOI:10.13182/NSE88-120

出版商:Taylor&Francis    

年代:1991

数据来源: Taylor

摘要:

AbstractTheoretical and experimental studies of the responses of various self-powered neutron detectors are carried out. Among the emitter materials studied are cobalt, hafnium, erbium, silver, rhodium, and gadolinium. The results are in good agreement with those found in the literature.

ISSN:0029-5639    

DOI:10.13182/NSE91-A23799

出版商:Taylor&Francis    

年代:1991

数据来源: Taylor

摘要:

AbstractThe values of gamma-ray buildup factors and attenuation coefficients rise steeply as the source energy decreases near the K edge in heavy materials and discontinuously fall at the K edge. However, the exposure rate attenuation factor, A(E, r) = D(E)B(E,μr) exp(–μr), given as a function of the penetration depth in centimetres, is relatively constant in the vicinity of the K edge. The development of a model that employs 4 K-shell X rays for the source shows that such behavior results from the large contribution of fluorescence radiation to the buildup factor for source photons of energies just above the K edge. In addition, an uncertainty in the extrapolation formula of the K parameter of the geometric progression buildup factor fitting function was removed for the energy range near the K edge.

ISSN:0029-5639    

DOI:10.13182/NSE91-A23800

出版商:Taylor&Francis    

年代:1991

数据来源: Taylor

摘要:

AbstractThe classic example used to illustrate the solution to the point kinetics equations with one equivalent delayed-neutron group is argued to be inappropriate for real reactors. However, a solution to the equations, altered by the addition of a neutron source, is shown to have qualitative resemblance to a real reactor and to predict that all steady states are subcritical. Reactivity oscillations are cited as another reason for subcritical steady states.

ISSN:0029-5639    

DOI:10.13182/NSE91-A23801

出版商:Taylor&Francis    

年代:1991

数据来源: Taylor

ISSN:0029-5639    

DOI:10.13182/NSE91-A23802

出版商:Taylor&Francis    

年代:1991

数据来源: Taylor