摘要:

AbstractThe potential role of dense plasma focus devices as compact neutron sources for fissile fuel breeding in conjunction with existing fission reactors is considered. It is found that advanced plasma focus devices can be used effectively in conjunction with neutronically efficient fission reactors to constitute“self-sufficient”breeders. Correlations among the various parameters such as the power output and conversion ratio of the fission reactor with the neutron yield and capacitor bank energy of the dense plasma focus device are presented and discussed.

ISSN:0029-5639    

DOI:10.13182/NSE78-A15182

出版商:Taylor&Francis    

年代:1978

数据来源: Taylor

摘要:

AbstractThe optimum inspection strategy of an m-out-of-n:G nuclear reactor protective system with nonidentical units is analyzed in this work. A 2-out-of-4:G system is used to formulate a multi-variable optimization problem to determine (a) the optimum order of supervision of the units and (b) the optimum supervision intervals between units. The case of systems with identical units is a special case of the above. Numerical results are derived using a computer algorithm.

ISSN:0029-5639    

DOI:10.13182/NSE78-A15183

出版商:Taylor&Francis    

年代:1978

数据来源: Taylor

摘要:

AbstractIn the use of large computers to analyze severe accidents in liquid-metal fast breeder reactors (LMFBRs), it has long been recognized that many of the fundamental phenomena cannot be precisely predicted because of uncertainty in the parameters that govern them. As a direct result, mechanistic analysis of such accidents has proceeded along a parametric path in which these variables are fixed at a certain constant value for the entire calculation: The influence of variation of this value is assessed by making a series of complete calculations with the parameter set at a different value for each such element of the series. While some parameters may be thought of as“correlated”or fixed for an entire calculation, very few are in fact constant throughout a reactor, and many are (for practical purposes) nearly completely uncorrected, either in space or time, during the hypothetical accident. Thus, such analysis has created a set of results that are not indicative or representative of an accident involving uncorrected or only partially correlated variable parameters. We describe here a methodology for dealing with various degrees of uncertainty or incoherence in these parameters. By using two very different mechanistic codes (FX2-POOL and EPIC), we demonstrate that the treatment of uncorrected parameters, such as droplet/particle size in a hypothetical core disruptive accident, as random variables with a certain probability distribution during each complete calculation of a series of calculations produces as much as an order of magnitude less uncertainty in the end result than had been obtained assuming perfect correlation. Finally, we categorize a small list of parameters as either correlated or uncorrected for some of the other LMFBR accident analysis codes. The technique we demonstrate can be easily implemented in a broad spectrum of accident analysis codes with similar benefits.

ISSN:0029-5639    

DOI:10.13182/NSE78-A15184

出版商:Taylor&Francis    

年代:1978

数据来源: Taylor

摘要:

AbstractMeasurements have been made of the angular distribution of fission fragments from235U at three fast-neutron energies. Results are fit by the expression W(θ) = 1 + A2cos2θ, with the anisotropy factor, A2, found to be−0.010±0.014 at 265 keV, +0.137±0.016 at 770 keV, and +0.157±0.019 at 964 keV.

ISSN:0029-5639    

DOI:10.13182/NSE78-A15185

出版商:Taylor&Francis    

年代:1978

数据来源: Taylor

摘要:

AbstractThe theory of a method of determination of reactivity from power spectral density measurements with252Cf and the results of experiments with a critical assembly mockup of a liquid-metal fast breeder reactor (LMFBR) and with uranium (93.2 wt%235U) metal cylinders and a sphere are presented. This method of reactivity determination has an advantage over existing methods in that it determines the reactivity only from properties of the reactor at the subcritical state of interest and thus does not require a calibration near delayed criticality. In these experiments, the reactivity was varied by changing the fissile loading or the amount of neutron absorber inserted; for the LMFBR mockup, the reactivity varied to∼75 dollars subcritical, and for the uranium metal assemblies to∼30 dollars subcritical. These experiments verified for the first time the predictions of theory that could be tested in the measurements. This method has potential use in the fuel loading of reactors to determine the reactivity far subcritical before initial criticality is achieved. It has the advantage of not requiring a calibration at known reactivity by another method; furthermore, the interpretation of the measured data to obtain the reactivity does not depend on relative or absolute values of the source intensity or detection efficiency. It can also be used to determine the reactivity of assemblies where loading to criticality is undesirable or where sufficient material to achieve criticality is not available.

ISSN:0029-5639    

DOI:10.13182/NSE78-A15186

出版商:Taylor&Francis    

年代:1978

数据来源: Taylor

摘要:

AbstractIn this paper, a Monte Carlo method for the calculation of the change in the neutron multiplication factor of a reactor due to cross-section perturbations is developed. Although similar to the perturbation source method developed by Matthes, this method is not limited to problems in which first-order perturbation theory is applicable. This method has been implemented in the KENO computer code and applied to a variety of problems. The results of these calculations are presented in this paper. This approach should prove useful in the solution of problems in which other Monte Carlo methods, such as Matthes' first-order perturbation source method and correlated sampling, fail.

ISSN:0029-5639    

DOI:10.13182/NSE78-A15187

出版商:Taylor&Francis    

年代:1978

数据来源: Taylor

摘要:

AbstractIn this paper, the probability table method, originally developed for unresolved resonance calculations, is adapted to the calculation of bubble worths in a reactor core. Unlike previous approaches to this problem, this method is applicable to a broad class of problems, avoids a high variance Monte Carlo calculation, and preserves the main features of a random bubble distribution. This approach is illustrated by the solution to several problems of varying degrees of complexity.

ISSN:0029-5639    

DOI:10.13182/NSE78-A15188

出版商:Taylor&Francis    

年代:1978

数据来源: Taylor

摘要:

AbstractThe gamma-ray production cross section of oxygen has been measured at incident neutron energies between 7 and 10.5 MeV. The production of the 6.13-, 6.92-, and 7.12-MeV gamma rays by the (n,n′γ) reaction in16O and the 3.09-, 3.68-, and 3.85-MeV gamma rays by the (n,αγ) reaction has been studied. In addition, the production cross section of the 4.44-MeV gamma ray from inelastic neutron scattering on carbon has been measured at one neutron energy, since many earlier measurements of gamma-ray production cross sections have been performed relative to this cross section. Monoenergetic neutrons were produced by the2H(d,n)3He and3H(p,n)3He reactions. The gamma radiation was detected by a large Nal(Tl) scintillator using time-of-flight techniques. The neutron flux was measured by means of a proton-recoil telescope using the n-p scattering cross section. The differential gamma-ray production cross sections were measured at 90 deg. In addition, the angular distribution for the 6.13-MeV gamma ray was determined at one neutron energy. The results for oxygen, which show pronounced structure of the cross section for the 6.13-MeV gamma ray over the whole energy region, are in disagreement with current data files, whereas the results for carbon are in agreement with a number of recent investigations of the12C(n,n′γ)12C and12C(n,n′)12C reactions.

ISSN:0029-5639    

DOI:10.13182/NSE78-A15189

出版商:Taylor&Francis    

年代:1978

数据来源: Taylor

摘要:

AbstractThis paper deals with the application of the finite element method to solve the momentum equation for the central subchannel of a fuel rod bundle. The Galerkin procedure in the method of weighted residuals is used to form the nonlinear algebraic equations that are solved by means of the Newton-Raphson approach. For turbulent flow, the eddy diffusivities are determined by Prandtl's mixing length hypothesis. The mixing lengths perpendicular and parallel to the wall are calculated from geometrical conditions using relations obtained by various authors. The results obtained are critically compared with experimental data and also with those obtained by finite difference procedures. There is a close agreement between the finite element results and other calculated data. Corresponding results also show a good agreement with experimental data available.

ISSN:0029-5639    

DOI:10.13182/NSE78-A15190

出版商:Taylor&Francis    

年代:1978

数据来源: Taylor

摘要:

AbstractThe occurrence and significance of complex characteristics in two-phase flow equation systems are clarified by a detailed analysis of separated two-phase flow between two parallel plates. The basic system of one-dimensional two-phase flow equations for this problem possesses complex characteristics, exhibits unbounded instabilities in the short-wavelength limit, and constitutes an improperly posed initial value problem. These difficulties have led some workers to propose major modifications to the basic equation system. We show that the relatively minor modification of introducing surface tension is sufficient to render the characteristics real, stabilize short-wavelength disturbances, and produce a properly posed problem. For a given value of the surface tension, the basic equation system thus modified is shown to correctly predict the evolution of small-amplitude disturbances having wavelengths long compared to the plate spacing. A formula is given for the artificial surface tension necessary to stabilize wavelengths on the order of the mesh spacing in a finite difference numerical calculation. A brief discussion is given concerning the expected behavior of surface tension as compared to viscosity in the nonlinear regime. The general relation between characteristics and stability is discussed in an appendix.

ISSN:0029-5639    

DOI:10.13182/NSE78-A15191

出版商:Taylor&Francis    

年代:1978

数据来源: Taylor