摘要:

AbstractAs performed conventionally, nuclear probabilistic risk assessment (PRA) may be criticized as utilizing inscrutable and unjustifiably“precise”quantitative informed judgment or extrapolation from that judgment. To meet this criticism, controlling principles that govern the formulation of probability densities are proposed, given only the informed input that would be required for a simple bounding analysis. These principles are founded upon information theoretic ideas of maximum uncertainty and cover both cases in which there exists a stochastic model of the phenomenon of interest and cases in which these is no such model. In part, the principles are conventional, and such an approach is justified by appealing to certain analogies in accounting practice and judicial decision making. Examples are given. Appropriate employment of these principles is expected to facilitate substantial progress toward PRA scrutability and transparency.

ISSN:0029-5639    

DOI:10.13182/NSE86-A27446

出版商:Taylor&Francis    

年代:1986

数据来源: Taylor

摘要:

AbstractA large cylindrical assembly of6LiD was irradiated by neutrons from a high-intensity deuterium-tritium source. Small samples of6Li,7Li, and6LiH, all encapsulated in lead, were positioned along the assembly axis and served as indicators for4He and tritium production. The amount of4He was determined by isotope dilution mass spectrometry while the tritium content of the6LiH wafers was measured by proportional counting of gas samples. Careful comparison of the results with TART Monte Carlo calculations showed excellent agreement. For4He generation, the experimental values were 1.01±0.06 times those of the calculations, while for tritium the ratio was 1.055±0.07.

ISSN:0029-5639    

DOI:10.13182/NSE86-A27447

出版商:Taylor&Francis    

年代:1986

数据来源: Taylor

摘要:

AbstractTotal4He production cross-section measurements have been made for6Li and7Li for 15-MeV neutrons. Isotopically enriched samples of lithium metal were bombarded with an intense flux of T(d,n) neutrons from a rotating target neutron source. Following the irradiation, the accumulated4He was determined by isotope-dilution mass spectrometry. The lithium samples and the incident neutron spectrum were accurately characterized, both by experimental methods and by calculational simulations. The measured4He production cross sections are 0.512±0.026 b for6Li and 0.336±0.016 b for7Li, at an average neutron energy of 14.95 MeV.

ISSN:0029-5639    

DOI:10.13182/NSE86-A27448

出版商:Taylor&Francis    

年代:1986

数据来源: Taylor

摘要:

AbstractPossible applications of an adaptive control method to a pressurized water reactor nuclear power plant are investigated. A self-tuning control algorithm with the generalized minimum variance strategy is employed. The control system design is based on a second-order linear model with unknown, time-varying parameters. To ensure that this low-order model describes the complex“real”dynamics well enough for control purposes, control parameters are updated on line with a recursive estimation sequence based on an extended least-squares method. The average coolant temperature is held as close as possible to a desired (but changing) reference value in the load-following mode of operation. The control rod position is selected as the control variable. Simulation results for such a system are encouraging and demonstrate the possibility of using this adaptive control method in an actual plant.

ISSN:0029-5639    

DOI:10.13182/NSE86-A27449

出版商:Taylor&Francis    

年代:1986

数据来源: Taylor

摘要:

AbstractA new algorithm for modeling charged-particle transport in a fully ionized plasma is presented. A standard multigroup discretization of the Fokker-Planck-Boltzmann equation is transport-corrected to implicitly include the anisotropic effects of both coulomb scattering and nuclear reactions. This allows the subsequent application of the Levermore flux-limited diffusion theory, which was originally developed for isotropic radiative transfer calculations. A finite differencing of the resulting spatial transport operator is constructed so as to yield centered and upwinded operators in the diffusion and free-streaming limits, respectively. The time integration is performed by the general purpose ordinary differential equation solver TORANAGA. This approach results in a highly vectorizable algorithm that has been implemented on the CRAY-1. Some numerical results are presented that compare this algorithm to the corresponding, but far more expensive, Monte Carlo calculations.

ISSN:0029-5639    

DOI:10.13182/NSE86-A27450

出版商:Taylor&Francis    

年代:1986

数据来源: Taylor

摘要:

AbstractA direct simulation of the density-wave oscillation limit cycle in a boiling flow system has been carried out. An unequal velocity, unequal temperature two-fluid description of boiling flow was used. The simulation procedure is aided considerably by first performing a linear stability analysis of the system in time domain. Comparison with experimental data is reported.

ISSN:0029-5639    

DOI:10.13182/NSE86-A27451

出版商:Taylor&Francis    

年代:1986

数据来源: Taylor

摘要:

AbstractAn application of an automated procedure called GRESS for adding derivative-taking capability to FORTRAN computer codes is presented. The efficiency and usefulness of GRESS for enhancing the point depletion and radioactive decay code ORIGEN2 are discussed. A new version of ORIGEN2 is now available that has the capability of calculating first derivatives and sensitivities of any variable in the code with respect to any other variable. The capabilities of the enhanced version, ORIGEN2G, are exemplified by its use in a sensitivity study of a high-level nuclear waste disposal problem. By using GRESS, the enhanced version ORIGEN2G was produced, tested, and verified in 2 man-months compared to an estimated 1 to 2 man-yr of effort to program a code with comparable capabilities.

ISSN:0029-5639    

DOI:10.13182/NSE86-A27452

出版商:Taylor&Francis    

年代:1986

数据来源: Taylor

摘要:

AbstractEarlier measurements of the kerma factor of carbon have been extended to neutron energies of 18 and 20 MeV. The measured values are lower than published values based on estimated microscopic cross sections.

ISSN:0029-5639    

DOI:10.13182/NSE86-A27453

出版商:Taylor&Francis    

年代:1986

数据来源: Taylor

摘要:

AbstractAn interpolation method is developed for functions of two variables. This approach uses semiempirical formulas with several parameters, avoiding the large data base and repetitious calculations characteristic of the usual interpolation methods. Two examples illustrate the method. In principle, the method can be extended to cases with more than two variables.

ISSN:0029-5639    

DOI:10.13182/NSE86-A27454

出版商:Taylor&Francis    

年代:1986

数据来源: Taylor

摘要:

AbstractFor noise analysis experiments in nuclear reactors, some self-powered neutron detectors with prompt neutron reactions (hafnium and erbium emitters) are investigated. Calculations of neutron physical characteristics using the program REND were carried out. Calculation of the neutron self-shielding factor, the neutron flux depression factor, and the total correction for choice geometry dimensions are shown. Absolute currents and detector sensitivities are presented.

ISSN:0029-5639    

DOI:10.13182/NSE86-A27455

出版商:Taylor&Francis    

年代:1986

数据来源: Taylor