摘要:

AbstractA methodology is developed for the evaluation of the energetic consequences of postulated core disruptive accidents (CDAs), in liquid-metal fast breeder reactors. The methodology provides a framework for integrating the results of mechanistic analyses, including whole-core simulations (SAS, SIMMER), special effects analytical evaluations, and simulant material experiments into a probabilistic appreciation of accident evolution paths and respective likelihoods. Detailed quantitative results are presented for the Clinch River Breeder Reactor heterogeneous core design. As a result of this work, new perspectives were generated in the following areas: role of plenum fission gases, presence and role of small recriticalities in the early stages of core disruption, large annular and cylindrical pool recriticalities and associated disassembly yields, energy partition, and the role of structural response of vessel internal structures. The results indicate that a CDA-induced energetic vessel head failure is physically unreasonable.

ISSN:0029-5639    

DOI:10.13182/NSE86-A17751

出版商:Taylor&Francis    

年代:1986

数据来源: Taylor

摘要:

AbstractA two-phase level swell will occur in pressurizers, steam generators, and others types of nuclear plant equipment holding large volumes of saturated water in response to a pressure reduction such as would be encountered in a line break event or a relief valve actuation.A simplified, but physically based one-dimensional model especially well suited to plant or system analysis is presented. Marviken test T-11 presents a unique source of data for confirmation of the analysis both in terms of the scale of the test itself and the number and variation of instrument locations.

ISSN:0029-5639    

DOI:10.13182/NSE86-A17752

出版商:Taylor&Francis    

年代:1986

数据来源: Taylor

摘要:

AbstractA new equation, called the neutron multiplicity equation (NME), has been derived starting from basic physics principles. Neutron multiplicityυis defined as the integral number of neutrons leaking from a neutron multiplying system for a source neutron introduced into it. Probability distribution of neutron multiplicities (PDNMs) gives the probability of leakage of neutrons as a function of their multiplicity v. The PDNM is directly measurable through statistical correlation techniques. In a specific application, the NME has been solved for PDNM as a function of v for9Be spheres of varying radii and driven by a centrally located 14-MeV deuterium-tritium neutron source. The potential of NME for sensitivity analysis is demonstrated through a particular modification of secondary neutron transfer cross sections of9Be. It turns out that PDNM is very sensitive, even as the“average”neutron leakage is practically insensitive to it.

ISSN:0029-5639    

DOI:10.13182/NSE86-A17753

出版商:Taylor&Francis    

年代:1986

数据来源: Taylor

摘要:

AbstractExposure at 1 m above the ground from isotropic gamma-ray point sources in the soil has been studied by the Monte Carlo method for source energies from 40 keV to 5 MeV. Source depths from 0.1 down to 30 cm and horizontal distances out to 5 mfp have been considered. Considerable deviations were found in the results of different buildup factor methods since such methods do not account for geometric effects at the interface. Moreover, exposures from infinite and finite plane sources have been calculated. It is shown that, for source energies<662 keV, the buildup factor methods underestimate the kerma considerably. It is shown how surface roughness conditions can be accounted for by the introduction of an effective source depth in the soil. The validity of approximations used to describe the exposure from finite or inhomogeneous plane sources with values for infinite homogeneous plane sources was examined.

ISSN:0029-5639    

DOI:10.13182/NSE86-A17754

出版商:Taylor&Francis    

年代:1986

数据来源: Taylor

摘要:

AbstractExperimental and computational studies of the gamma-ray energy deposition rate in the Fast Breeder Blanket Facility (FBBF) were performed with thermoluminescent dosimeters (TLDs). Various corrections including the TLD neutron sensitivities and the f factors (general cavity-ionization theory) were applied to the TLD measurements. Comparisons were made with results of three computer codes—1DX, 2DB, and ANISN—and two nuclear libraries—LIB-IV and EPR. Both neutron and gamma-ray calculations were performed.The previously reported deviations between the gamma-ray energy deposition calculated-toexperiment (C/E) ratios for lead and for stainless steel were resolved. It is believed that the remaining C/E discrepancy comes primarily from the inaccuracies in the neutronics part of the calculations, because similar dropoffs are also reported in the FBBF reaction rate C/E comparisons.Detailed analysis of the deviation between transport (Sn) and diffusion calculations in the FBBF were performed. It was found that the deviation is built up in the blanket region and is largely independent of the curvature of the“independent”source region. Comparisons between Snand diffusion calculations (on a one-dimensional basis) for neutron fluxes and reaction rates indicated that the use of transport calculations should reduce the discrepancies of C/E comparisons.

ISSN:0029-5639    

DOI:10.13182/NSE86-A17755

出版商:Taylor&Francis    

年代:1986

数据来源: Taylor

摘要:

AbstractAn experiment to measure the heat deposition in various materials in the vicinity of a spallation neutron target is described. This experiment has been performed at the Thermal Neutron Facility, TRIUMF.In the analysis of the data, the contributions to the heat deposition from (n,γ) capture processes, fast neutron, and prompt gamma-ray scattering are separated.

ISSN:0029-5639    

DOI:10.13182/NSE86-A17756

出版商:Taylor&Francis    

年代:1986

数据来源: Taylor

摘要:

AbstractA class of finite difference methods, the linear one-cell functional methods, is introduced, and observed to encompass the vast majority of spatial approximations used in one-dimensional transport theory. It is noted that, under minimal additional assumptions, these methods satisfy the classical result, valid for one-step finite difference approximations to initial value problems, that consistency implies both convergence and stability. This explains the observed absence of nonconvergence and instability from ray-tracing calculations, and also indicates the limitations of this result.

ISSN:0029-5639    

DOI:10.13182/NSE86-A17757

出版商:Taylor&Francis    

年代:1986

数据来源: Taylor

摘要:

AbstractA method for solving particle transport problems has been developed. In this method the particle flux is expressed as a linear and separable sum of odd and even components in the direction variables. Then a Bubnov-Galerkin projection technique and an equivalent variational Raleigh-Ritz solution are applied to the second-order transport equation. A dual finite element basis of polynomial splines in space and spherical harmonics in angle is used.The general theoretical and numerical problem formalism is carried out for a seven-dimensional problem with anisotropic scattering, time dependence, three spatial and two angular variables, and with a multigroup treatment of the energy dependence. The boundary conditions for most physical problems of interest are dealt with explicitly and rigorously by a classical minimization (variational) principle. Finally, the computational validation of the method is obtained by a computer solution to the monoenergetic steady-state air-over-ground problem in a cylindrical (r, z) geometry and with an exponentially varying atmosphere.

ISSN:0029-5639    

DOI:10.13182/NSE86-A17758

出版商:Taylor&Francis    

年代:1986

数据来源: Taylor

摘要:

AbstractThe ideas of the FN and transport PNapproximation (TPN) methods in transport theory are suitably combined to formulate an accurate approximation scheme for the monoenergetic transport equation. The method involves the use of the singular integral equation for the surface flux as used in the FNmethod and angular flux representation of the TPNapproximation. This leads to a consistent approximate scheme for the computation of angular flux.

ISSN:0029-5639    

DOI:10.13182/NSE86-A17759

出版商:Taylor&Francis    

年代:1986

数据来源: Taylor

摘要:

AbstractThree models, a linear, exponential or BEST, and a power model, developed using sensitivity theory to predict deep-penetration neutron transport in practical shielding problems, have been generalized into a common expression. One can obtain any of the above three models from this generalized expression simply by choosing the proper index parameters. Subsequently, a scheme for implementation of this into a computer code was adopted in“SENATOR.”SENATOR replaces the SENTINEL module of the Oak Ridge National Laboratory (ORNL) FORSS system. The supporting data bases (i.e., the sensitivity profile) and the Fortran code, along with some utility programs, are assembled in a package identified as CONSENT and can be obtained through the Radiation Shielding Information Center at ORNL.

ISSN:0029-5639    

DOI:10.13182/NSE86-A17760

出版商:Taylor&Francis    

年代:1986

数据来源: Taylor