摘要:

AbstractFor a heterogeneous multiplying system, a one-group diffusion model is shown to exhibit two spatial eigenvalues (inverse relaxation lengths). The smallest root, which describes the long-range behavior of the neutron flux, is that eigenvalue that would be exhibited by an equivalent homogeneous system. The largest root corresponds to the inverse relaxation length of the moderator. The existence of these two eigenvalues is relevant to interpretation of neutron noise measurements in boiling water reactors.

ISSN:0029-5639    

DOI:10.13182/NSE82-A21425

出版商:Taylor&Francis    

年代:1982

数据来源: Taylor

摘要:

AbstractCalculations of neutron wave propagation across a temperature discontinuity in graphite using a multigroup approach are reported. Diffusion, as well as thermalization properties of the medium, are investigated near the interface. As the interface is crossed from the higher to the lower temperature region, a depletion of sub-Bragg neutrons is observed. There is a buildup of neutrons as one crosses the interface from the lower to the higher temperature side.

ISSN:0029-5639    

DOI:10.13182/NSE82-A21426

出版商:Taylor&Francis    

年代:1982

数据来源: Taylor

摘要:

AbstractThe AMPX-KENO computer code package is commonly used to evaluate criticality in high-density spent fuel storage rack designs. Consequently, it is important to know the reliability that can be placed on such calculations and whether or not the results are conservative. Recent critical experiments by the Babcock&Wilcox Company (B&W) provide data on configurations with thin absorbers containing boron that are more nearly representative of poisoned spent fuel storage rack designs than were earlier critical experiments.A series of AMPX-KENO calculations has been made on selected critical experiments and the results compared with similar analyses reported in the literature by the Oak Ridge National Laboratory and B&W. Within the normal statistical variation of KENO calculations, results confirm that there is no apparent difference in the versions of AMPX-KENO and the 123-group GAM-THERMOS libraries used at three different computer installations.Evaluation of the calculational results provides evidence for a statistically significant trend toward overprediction of reactivity with increasing reactivity worth of thin plates of boron-containing material. Similarly, statistical analyses reveal a trend toward underprediction of reactivity with increasing water-gap spacing between fuel assemblies. For most realistic spent fuel storage rack designs including neutron absorbers, these results imply that AMPX-KENO calculations are conservative and could possibly overpredict reactivity by as much as 2 to 5%Δk, based on a linear extrapolation of observed trends.Statistical analyses in support of these contentions are provided, and additional critical experiments with boron absorbers of higher reactivity worth are recommended.

ISSN:0029-5639    

DOI:10.13182/NSE82-A21427

出版商:Taylor&Francis    

年代:1982

数据来源: Taylor

摘要:

AbstractGroup parameters (abundances and half-lives) and group spectra have been derived from the nuclear data and fission yields of the individual precursors for six delayed-neutron groups and for the fissionable nuclides232Th,233U,235U,236U,238U,237Np,239Pu,240Pu,241Pu,242Pu, and252Cf. The results can be combined into a calculation of the resulting delayed-neutron energy spectrum at any cooling time and for any mixture of the above-mentioned nuclides.The validity of the method is checked in various ways such as comparing total neutron yields and group yields with the corresponding experimental quantities and comparing neutron spectra for half-life groups 2, 3, and 4 with integral experimental measurements. The outcome of these tests puts confidence in using the spectra obtained for applications within nuclear technology.

ISSN:0029-5639    

DOI:10.13182/NSE82-A21428

出版商:Taylor&Francis    

年代:1982

数据来源: Taylor

摘要:

AbstractNeutron cross sections have been measured for10B and11B. Elastic angular distribution data for10B are reported for incident neutron energies of 8.0, 9.0, 10.0, 11.0, 12.0, 13.0, and 14.0 MeV. Elastic scattering data and inelastic scattering data for states at excitation energies of 2.14, 4.46, and 5.04 MeV in11B are reported for incident neutron energies of 8.0, 9.0, 9.7, 9.9, 11.0, 12.0, 13.0, and 14.0 MeV. Legendre coefficients for angular distributions are obtained. All data are corrected for finite geometry and multiple scattering effects through a light-element Monte Carlo code. The angle integrated data for11B are in disagreement with ENDF/B-IV for the higher neutron energies.

ISSN:0029-5639    

DOI:10.13182/NSE82-A21429

出版商:Taylor&Francis    

年代:1982

数据来源: Taylor

摘要:

AbstractNeutron self-indication measurements simulating238U capture in reactors have been carried out over the energy range from 3 eV to 3 keV using shielding samples at 77, 293, and 873 K. The data have been reduced to open and self-shielded capture yields provided on magnetic tape as benchmark data for comparison with nuclear design calculations. The important energy range below 100 eV has been analyzed in detail both to obtain improved resonance parameters for the levels at 6.67, 20.9, 36.8, 66.1, and 80.7 eV and to examine the accuracy with which cross sections are calculated from resonance formalisms. The improved resonance parameters, when used with an accurate but practical multilevel formalism, reduce by about one-half the long-standing discrepancy between calculated and measured238U resonance capture integrals.

ISSN:0029-5639    

DOI:10.13182/NSE82-A21430

出版商:Taylor&Francis    

年代:1982

数据来源: Taylor

摘要:

AbstractThe235U neutron-induced fission cross section was measured at a neutron energy of 14.1 MeV using the time-correlated associated-particle technique with the3H(d,α) n reaction at the National Bureau of Standards 3-MV Van de Graaff Laboratory. The areal density and total mass of the235U deposits were measured relative to the standard235U reference deposit (Los Alamos National Laboratory Spare Number 1) using thermal-neutron-induced fission counting. The total mass was also determined from the alpha-particle decay rate. The measured235U cross section at 14.1±0.1 MeV is 2.080±0.030 b where the uncertainty is one standard deviation. This value agrees within 1% with other recent measurements using this technique and with the ENDF/B-V evaluation.

ISSN:0029-5639    

DOI:10.13182/NSE82-A21431

出版商:Taylor&Francis    

年代:1982

数据来源: Taylor

摘要:

AbstractThe effects of bubble interaction and boundary surfaces on the radial oscillation dynamics of multiple air bubbles in a liquid pool are analyzed. Quantitative predictions are obtained for the coupling between bubble phasing and the distribution of power over a range of frequencies, the crowding effect on bubble frequency when multiple bubbles are formed in a single pool, the effect on frequency of a bubble's rise from a point near the floor of a pool toward the free surface, and the frequency correction for test tank data when the design condition of interest is a discharge in a larger pool.

ISSN:0029-5639    

DOI:10.13182/NSE82-A21432

出版商:Taylor&Francis    

年代:1982

数据来源: Taylor

摘要:

AbstractA new approach in the application of modern system identification and estimation techniques is proposed to help nuclear reprocessing facilities meet the nuclear accountability requirement proposed by the International Atomic Energy Agency. The proposed identification and estimation method considers the material inventory in a portion of the chemical separations area of a reprocessing facility. The method addresses the nonlinear aspects of the problem, the time delay through the separation facility, and the lack of measurement access. The method utilizes only input-output measured data and knowledge of the uncertainties associated with the process and measured data.The approach of accurate materials accountability presented could also be applied to other processes exhibiting the same characteristics such as time delays, nonlinear process, and the lack of measurement access.

ISSN:0029-5639    

DOI:10.13182/NSE82-A21433

出版商:Taylor&Francis    

年代:1982

数据来源: Taylor

摘要:

AbstractParallel computations of the finite difference approximation to the neutron diffusion equation, especially for three-dimensional problems, are investigated in anticipation of the use of high-speed vector computers such as the CRAY-1. Several general methods of solution of the seven-point formula are numerically studied from the viewpoint of the feasibility of their simultaneous calculations on vector computers.The time required for diffusion calculations can be reduced by a factor of 3 through vectorizing the inner iteration by the multidimensional ADC code. It is found that a checkerboard ordering in the overrelaxation method and a recently developed modified SLOR method avoid the degradation of convergence in vector iterations compared with traditional SOR and SLOR.

ISSN:0029-5639    

DOI:10.13182/NSE82-A21434

出版商:Taylor&Francis    

年代:1982

数据来源: Taylor