摘要:

AbstractAn investigation of the stability of a nuclear power reactor subject to random macroscopic parameter variations is performed.An analysis procedure for determining the effect of stochastic coefficients on the stability in the mean and mean square of linear systems is presented. The procedure is based on Gaussian white process variations which can be shown to be governed by the Fokker-Planck equation. Moment equations are extracted from the Fokker-Planck equation and serve as system equations used for the stability analysis.It is shown that for some simple space-independent reactor models it is possible for random macroscopic parameter variation to destabilize in the mean and mean square a deterministically stable system. Conversely, the study has shown that under certain conditions random macroscopic variation of system parameters can also stabilize in the mean and mean square, a system which is deterministically unstable.A coupled-core spatial reactor model is utilized for the investigation of xenon instability. The results of this analysis again indicate that random macroscopic parameter variation can be a stabilizing or destabilizing influence.Analog simulations of linear systems with stochastic coefficients and a simple reactor model are used to verify the analysis procedure developed in this research.

ISSN:0029-5639    

DOI:10.13182/NSE73-A23272

出版商:Taylor&Francis    

年代:1973

数据来源: Taylor

摘要:

AbstractThe neutron-induced fission cross section of249Cf was measured from 13 eV to 3 MeV. Neutrons from the Physics-8 underground nuclear explosion traversed a 240-m vertical evacuated flight path and interacted at ground level with a249Cf sample and with neutron flux monitors. Abundant fission was observed throughout the neutron energy region studied, although the several-MeV cross section was lower than expected on the basis of systematics. Forty-three resonances between 15 and 70 eV were parameterized using a multilevelR-matrix formalism. In this energy region, the average level spacing, corrected for five postulated unobserved levels, was 1.07±0.14 eV, both spin states of the compound nucleus being taken together. Assuming both spin states to have the same properties, thes-wave neutron strength function per spin state〈Γ0n〉/〈D〉was (1.5±0.3)×The average reduced neutron width〈Γ0n〉was 0.31±0.08 meV. For 35 well-defined resonances between 15 and 70 eV, the average fission width〈Γƒ〉was 180 meV.

ISSN:0029-5639    

DOI:10.13182/NSE73-A23273

出版商:Taylor&Francis    

年代:1973

数据来源: Taylor

摘要:

AbstractThe neutron capture cross section of238U was measured for incident neutron energies between 5 eV and 100 keV using a pulsed electron Linac neutron source and the time-of-flight technique. Capture gamma rays were detected by a large liquid scintillator located on a 40-m flight path. The incident neutron flux was monitored by a10BF3ionization chamber. The cross section was normalized by the saturated resonance technique.The data have uncertainties which increase from∼5% at 1 keV to 10% at 100 keV. These data are compared with results from other measurements and with various evaluations.

ISSN:0029-5639    

DOI:10.13182/NSE73-1

出版商:Taylor&Francis    

年代:1973

数据来源: Taylor

摘要:

AbstractThermal-neutron spectrum indexes in uranium and uranium-plutonium clustered fuel elements, organic-cooled and D2O-moderated, were measured in the temperature range from 20 to 200°C, by activation of239Pu-235U and176Lu-164Dy detector pairs. The experimental results were used to test the multigroup transport code HEROIC and associated cross-section libraries.

ISSN:0029-5639    

DOI:10.13182/NSE73-A23275

出版商:Taylor&Francis    

年代:1973

数据来源: Taylor

摘要:

AbstractAn extensive series of measurements has been made in the Demonstration Reactor benchmark, the Zero Power Plutonium Reactor (ZPPR) Assembly 2, to provide physics data necessary for LMFBR design. An important objective of the program was to test the applicability of data obtained in the plate-fueled critical to a power reactor design with a more homogeneous composition. Sufficient, fuel inventory was obtained in the form of rods which were used, within sodium-filled calandria, to build large zones in which direct comparisons of parameters could be made with those in the plate zones. A variety of quantities worth of Compared in the two environments. In addition to the direct reactivity worth of rod-for-plate substitution, comparisons are given for small sample and rates,reaction Worths’neutron spectrum, reaction rate ratios, in-cell reaction rates, reaction rate scans, sodium-void coefficient, and238U Doppler coefficient. The experiments are Compared With calculations using the ARC system and NDFB/Version-I data. It is found that many parameters of interest can be adequately studied in the plate geometry and that the calculation methods, in genidentified a good representation of the heterogeneity effects. Some areas are identified in which further experimental and analytical study is needed.

ISSN:0029-5639    

DOI:10.13182/NSE73-A23276

出版商:Taylor&Francis    

年代:1973

数据来源: Taylor

摘要:

AbstractA practical method is derived for calculating the effective resonance cross sections in fast reactor assemblies with complicated geometry. The conventional equivalence relation between homogeneous and heterogeneous resonance integrals is extended to the complicated geometries which are composed of various types of plates, including two types of fuel plates with different compositions. This extended equivalence relation indicates that the effective cross sections in a heterogeneous system can be calculated by using a cross-section set of the Bondarenko type. The numerical results for the effective cross sections given by the present method are in good agreement with the exact values obtained by the RABID code.

ISSN:0029-5639    

DOI:10.13182/NSE73-A23277

出版商:Taylor&Francis    

年代:1973

数据来源: Taylor

摘要:

AbstractThe application of the finite element method to problems in neutron diffusion in space, energy, and time is studied. The use of piecewise polynomials with a variational form of the diffusion equation leads to algebraic systems of equations with characteristics similar to the usual finite difference equations. In Part I, a theoretical analysis of the finite element method, with Hermite polynomials, is presented and rigorous error bounds for the approximate solution are developed. In Part II, numerical studies are presented for problems in space and time. The results confirm the theoretical analysis and indicate the power of the method for diffusion problems.

ISSN:0029-5639    

DOI:10.13182/NSE73-A23278

出版商:Taylor&Francis    

年代:1973

数据来源: Taylor

摘要:

AbstractGamma-ray yields as a function of neutron energy from thermal to 1 MeV for iron have been generated with a combined experimental and theoretical approach. The theoretical part is to a large extent statistical; however, parameters are introduced to compensate for the nonstatistical behavior. Experimental information used to evaluate these parameters are the branching ratios among discrete levels and the gamma-ray primary transitions from thermal and available resonance capture. A discussion of the implications of additional resonance capture yield data, which was made available after the completion of the calculation, is included. The results have been compared with integral experiments, and the agreement is favorable. Considerable variations in the capture gamma-ray yields as a function of incident neutron energy are noticed.

ISSN:0029-5639    

DOI:10.13182/NSE73-A23279

出版商:Taylor&Francis    

年代:1973

数据来源: Taylor

摘要:

AbstractThe classical elastic scattering probability function,ƒs(vu',vu), and corresponding speed and angular functions are simply generalized to any arbitrary coordinate system moving with velocity u. Unified consideration leads to new mixed, but equivalent, representations ofƒs(vu',vu) which recover earlier results. The general treatment is concise and maintains the fundamental features of the binary collision in three dimensions. Extension of the analysis to anisotropic scattering is discussed briefly.

ISSN:0029-5639    

DOI:10.13182/NSE73-A23280

出版商:Taylor&Francis    

年代:1973

数据来源: Taylor

摘要:

AbstractThe intermediate resonance approximation of resonance absorption is applied to a heterogeneous fast reactor assembly to see how each resonance of238U deviates from the narrow resonance approximation. The resonance integral is calculated for the 50 resonances of238U in ENDF/B-II below 1.9 keV. The averaged deviation of these resonances from the narrow resonance extreme was found to be∼4%. It is concluded that the effective group cross sections in heterogeneous fast systems can be estimated reasonably well by the narrow resonance approximation, even though this approximation tends to underestimate the resonance integrals noticeably for a handful of resonances with extremely large neutron widths.

ISSN:0029-5639    

DOI:10.13182/NSE73-A23281

出版商:Taylor&Francis    

年代:1973

数据来源: Taylor