摘要:

AbstractAn autoregressive (AR) model with pseudo-random binary sequence (PRBS) test signals was applied to the dynamics of the Japan Power Demonstration Reactor, a boiling water reactor (BWR). The decision of the order of the AR model was based on the Akaike criterion. Multi-input test signals of the PRBS were applied to the steam-flow control valve and the forced circulation pump speed control terminal. Seventeen variables including the instrumented fuel assemblies were observed. The AR model identification facilitated building the BWR dynamics model as a multivariable system. The experiment indicated that the BWR dynamics with rather intensive nonwhite noise interference was effectively represented by the AR model, which was compared with a linear theoretical dynamics model. The results suggested that the identified AR model plays an important role in verifying, modifying, and improving the theoretical dynamics model.

ISSN:0029-5639    

DOI:10.13182/NSE78-A27121

出版商:Taylor&Francis    

年代:1978

数据来源: Taylor

摘要:

AbstractAn analytical and experimental investigation of void distribution in internally heated boiling pools is presented. The experimental investigation involved measurement of the vertical profile of the void fraction and the average void fraction in an aqueous solution of ZnSO4. The observed void fractions were found to be adequately correlated byIf the results of this investigation are extended to a boiling pool of UO2, it is predicted that substantial voiding will occur even when only a very small fraction of nominal operating power density in nuclear reactors is consumed in internal vaporization.

ISSN:0029-5639    

DOI:10.13182/NSE78-A27122

出版商:Taylor&Francis    

年代:1978

数据来源: Taylor

摘要:

AbstractNeutrons and gamma rays emitted by a test fuel element were imaged through a linear array of pinholes. The ionizing radiations formed optical images on a plastic scintillator that was viewed by an intensified television (TV) system. The TV records provided a sequence of twelve 16-ms frames spanning a 2860-MW, 315-MW-s Transient Reactor Test Facility transient. Data show radial expansion of the test fuel pin.

ISSN:0029-5639    

DOI:10.13182/NSE78-A27123

出版商:Taylor&Francis    

年代:1978

数据来源: Taylor

摘要:

AbstractThere is a continuing interest in the use of fixed neutron absorbers (poisons) for criticality control, since their use would permit safely handling larger quantities of nuclear materials with reduced probability of criticality. The effectiveness of such absorbers as neutron poisons depends on self-shielding effects, which in turn are determined by the magnitude of the absorption cross sections and their variation with energy, the thickness of material, and the neutron energy spectrum. Criticality experiments were performed to obtain data on the reactivity worths of several thicknesses of the following materials in two different neutron energy spectra:BoralCadmiumType 304-L stainless steel containing 1.6 wt% boronType 304-L stainless steel containing 1.1 wt% boronType 304-L stainless steelUranium depleted to 0.2 wt%235ULead.The measurement data reported are limited to a single region of a given absorber material in each critical assembly. Combinations of absorber materials or multiregions were not investigated; however, material thicknesses were varied from 0 to∼60 mm. The data are presented as sets of clean, well-defined, poisoned critical assemblies that can be used to check calculational techniques and cross-section data in two different neutron energy spectra. The materials are listed above in the order of their measured relative worth as fixed poisons in either neutron energy spectrum.

ISSN:0029-5639    

DOI:10.13182/NSE78-A27124

出版商:Taylor&Francis    

年代:1978

数据来源: Taylor

摘要:

AbstractCross sections for the production of gamma rays by bombardment with 14.2-MeV neutrons were measured for 20 samples ranging from beryllium to plutonium. Differential cross sections are given as a function of gamma-ray energy over the region from 0.2 to 9.0 MeV for angles between the incident neutrons and emitted photons of 90 to 130 deg. For some of the light elements, cross sections are also presented for individual gamma rays. Pulsed-beam neutron time-of-flight techniques were employed to reduce background effects in the large NaI(Tl) gamma-ray spectrometer.

ISSN:0029-5639    

DOI:10.13182/NSE78-A27125

出版商:Taylor&Francis    

年代:1978

数据来源: Taylor

摘要:

AbstractDifferential neutron cross sections of10B for elastic scattering have been measured for∼30 incident neutron energies between 4 and 8 Me V. Neutrons inelastically scattered from the 0.717-MeV level were completely resolved from the elastic group except at the most forward angles at energies above 7.5 MeV. Generally, the differential cross sections are slowly varying with energy, indicating little resonance structure in this region. These data are consistent with earlier lower energy measurements done at Edwards Accelerator Laboratory and provide detailed data in a region where only sparse data were previously available to evaluators and designers in the nuclear energy field.

ISSN:0029-5639    

DOI:10.13182/NSE78-A27126

出版商:Taylor&Francis    

年代:1978

数据来源: Taylor

摘要:

AbstractThe differential elastic and inelastic neutron scattering cross sections of238U at 144 keV were measured using a silicon neutron filtered beam and a spherical proton recoil counter. The absolute magnitudes were obtained by comparison with the measured lead cross section. Both integrated values show excellent agreement with the ENDF/B-IV file.

ISSN:0029-5639    

DOI:10.13182/NSE78-A27127

出版商:Taylor&Francis    

年代:1978

数据来源: Taylor

摘要:

AbstractHigh-resolution total neutron cross-section measurements in natural vanadium. manganese, and cobalt were made in the energy range up to a few hundred keV with the Columbia University Nevis neutron velocity spectrometer using a 200-m flight path and a nominal resolution of 0.5 ns/m. These cross-section data were analyzed with an R-matrix multilevel code, and the resonance parameters (Eλ,Γπ. S0,〈D〉) were obtained. In addition, making use of the published thermal energy data, the parameters of the bound levels were determined. From these measurements the values of S0up to 215-keV neutron energy for vanadium [= 8.62±2.45,= 8.79±2.50, and= 8.7±1.81; up to 200 keV for manganese [= 3.10±0.70,= 4.75±1.10, and= 3.93±0.651, and up to 80 keV for cobalt [= 4.02±0.96,= 2.94±0.75. and= 3.48±0.65 in units of 10−4eV−1/2] have been obtained. The corresponding mean level spacings up to 215 keV for vanadium are= 8.7±1.25 keV and= 8.33±1.25 keV, up to 100 keV for manganese are= 3.85±0.55 keV and= 4.00±0.59 keV, and up to 80 keV for cobalt are= 2.29±0.28 keV and= 2.67±0.36 keV. The value of spin cut-off factor a is found to vary from 2.7 to 4 for these nuclei. These results do not show any J dependence on the strength function.

ISSN:0029-5639    

DOI:10.13182/NSE78-A27128

出版商:Taylor&Francis    

年代:1978

数据来源: Taylor

摘要:

AbstractA class of stochastic models for the Monte Carlo integration of the adjoint neutron transport equation is described. Some current general methods are brought within this class, thus preparing the ground for subsequent comparisons. Monte Carlo integration of the adjoint Boltzmann equation can be seen as a simulation of the transport of mathematical particles with reaction kernels not normalized to unity. This last feature is a source of difficulty: It can influence the variance of the result negatively and also often leads to preparation of special“libraries”consisting of tables of normalization factors as functions of energy, presently used by several methods. These are the two main points that are discussed and that are taken into account to devise a nonmultigroup method of solution for a certain class of problems. Reactions considered in detail are radiative capture, elastic scattering, discrete levels and continuum inelastic scattering, for which the need for tables has been almost completely eliminated. The basic policy pursued to avoid a source of statistical fluctuations is to try to make the statistical weight of the traveling particle dependent only on its starting and current energies, at least in simple cases. The effectiveness of the sampling schemes proposed is supported by numerical comparison with other more general adjoint Monte Carlo methods. Computation of neutron flux at a point by means of an adjoint formulation is the problem taken as a test for numerical experiments. Very good results have been obtained in the difficult case of resonant cross sections.

ISSN:0029-5639    

DOI:10.13182/NSE78-A27129

出版商:Taylor&Francis    

年代:1978

数据来源: Taylor

摘要:

AbstractA method of analysis is developed for nuclear reactor accident initiating events that are localized in space. The method is based on a flux factorization technique, accounting for the flux shape changes taking place near the region of perturbation. In the steady state, the neutron shape functions are expanded in a series of eigenfunctions of the steady-state group removal operator. During the unsteady state, the time-dependent group shape functions are expanded in a series of the same stationary eigenfunctions with time-dependent Fourier coefficients. An auxiliary function is added to this expansion to take account of the spatial variation of the spectral hardening of neutrons in the immediate vicinity of the disturbed region. From the resulting representation of the group shape functions, the equations to be satisfied by the time-dependent Fourier coefficients and the time-dependent auxiliary shape function due to the disturbed region are developed consistently. A typical large [1000-MW(e)] liquid-metal fast breeder reactor with two radial core zones of different enrichments is analyzed by the above method. The transient initiating perturbation is taken to be a specified rate of coolant voiding from a single subassembly in the reactor core. The results show a strong dependence of the reactivity added on the radial location of the voiding perturbation and on the rate of voiding.

ISSN:0029-5639    

DOI:10.13182/NSE78-A27130

出版商:Taylor&Francis    

年代:1978

数据来源: Taylor