摘要:

AbstractA new evaluation of the“resolved resonance range”for the neutron cross sections of235U is described. Up to 110 eV, the evaluation is based on anR-matrix analysis of several fission, capture, and transmission measurements. Levels above 110 eV are no longer resolved so that many resonances are missed; from 110 to 500 eV, most of the important resonances can be identified and analyzed so that the cross section and transmission data are well represented by the proposed parameters. From 500 to 2250 eV, fictitious parameters are provided that describe fairly well the results of thick sample transmission measurements and recent fission cross-section data. Such a parameterization is likely to yield a better approximation of resonance self-shielding than the current ENDF/B- V unresolved resonance treatment.

ISSN:0029-5639    

DOI:10.13182/NSE89-A28500

出版商:Taylor&Francis    

年代:1989

数据来源: Taylor

摘要:

AbstractThe state of the JEF-2 evaluation of238U + n cross sections in the region of unresolved resonances (∼10 to 300 keV) is reported with special emphasis on recent progress in theory (rigorous expressions for resonance-averaged cross sections with arbitrary level overlap), which permits reliable model-aided evaluation and parameterization by simultaneous fits to total, capture, and inelastic scattering cross-section data. Formalized inclusion of information from resolved resonances via Bayes’theorem has helped to remove discrepancies between resolved and unresolved parameters and has improved resonance statistics. Comparison with the latest ENDF/B-VI (pointwise) evaluations of the capture and the total cross sections shows agreement within 1 to 3%.

ISSN:0029-5639    

DOI:10.13182/NSE89-A28501

出版商:Taylor&Francis    

年代:1989

数据来源: Taylor

摘要:

AbstractThe quality and quantity of delayed neutron precursor data have greatly improved over the past decade and a half. Supplementation of the data with model calculations and the use of models to extend the number of precursors to 271 is now practical. These data, along with other improved fission product parameters, permit direct calculations of aggregate behavior for many fissioning nuclides. The results can still be approximated using a few (usually six) temporal groups, including corresponding spectra, as in past practice for reactor physics. An extensive effort to provide a complete set of evaluated data is summarized, with an emphasis on its use to generate the temporal approximations; precursor data and group values are intended for inclusion in ENDF/B-VI.

ISSN:0029-5639    

DOI:10.13182/NSE103-129

出版商:Taylor&Francis    

年代:1989

数据来源: Taylor

摘要:

AbstractA cobalt test assembly containing yttrium hydride pins for neutron moderation was irradiated in the Fast Flux Test Facility (FFTF) during cycle 9A for 137.7 equivalent full-power days at a power level of 291 MW. The 36 test pins consisted of a batch of 32 pins containing cobalt metal used to produce60Co and a set of four pins with europium oxide to produce153Gd, a radioisotope used in detection of the bone disease osteoporosis. Postirradiation examination of the cobalt pins determined the60Co production to be predictable to an accuracy of∼5 %. The measured60Co spatially distributed concentrations were within 20% of the calculated concentrations. The assembly average60Co measured activity was 4% less than the calculated value. The europium oxide pins were gamma scanned for the europium isotopes152Eu and154Eu to an absolute accuracy of -10%. The measured europium radioisotope andI53Gd concentrations were within 20% of calculated values. The hydride assembly performed well and is an excellent vehicle for many FFTF isotope production applications. The results also demonstrate the accuracy of the calculational methods developed by the Westinghouse Hanford Company for predicting isotope production rates in this type of assembly.

ISSN:0029-5639    

DOI:10.13182/NSE89-A28503

出版商:Taylor&Francis    

年代:1989

数据来源: Taylor

摘要:

AbstractFormulas for predicting the uncertainty of neutronic performance parameters are derived for three methods: the bias factor method, the adjustment method, and the combined method. The prediction uncertainties are obtained by including both experimental and method errors. The adjustment method, in principle, yields the same uncertainty as the combined method. The derived formulas are applied to a large homogeneous l000-MW(electric) liquid-metal fast breeder reactor core.

ISSN:0029-5639    

DOI:10.13182/NSE89-1

出版商:Taylor&Francis    

年代:1989

数据来源: Taylor

摘要:

AbstractThe reactor physics problems in core designs for high-burnup and long-operating-cycle length are clarified. Two core concepts are proposed to deal with these problems:1.the advanced homogeneous core (A-HOC) in which the power distribution is flattened by dividing the core into two regions with different fuel volume fractions2.the advanced axial heterogeneous core (A-AHC) in which a thin internal blanket is introduced at the core midplane in the inner core region of the A-HOC.Core performance parameters such as fissile inventory, breeding ratio, and power and flux distributions are evaluated in detail by discrete burnup analyses. The results show that the A-AHC has more uniform power and flux distributions and a more stable power shape than the A-HOC, and the A-AHC seems to be a good candidate for achieving high-burnup and long-operating-cycle length.

ISSN:0029-5639    

DOI:10.13182/NSE89-A28505

出版商:Taylor&Francis    

年代:1989

数据来源: Taylor

摘要:

AbstractFavorable passive reactivity shutdown performance in response to unprotected accident initiators has been shown to be achievable when several measurable, integral reactivity parameters related to the power, flow, and inlet temperature coefficients of reactivity satisfy certain simple constraints among their dimensionless ratios. The trends in these dimensionless ratios with reactor size for both oxide- and metal-fueled cores have been developed, based on a data base of∼24 reactor designs in the range from 400 to 3600 MW(thermal). Based on the trends, it is possible to conclude that the favorable passive reactivity shutdown features that accrue to the metallic-fueled reactors in the mod-ular-size range can be achieved as well in the larger commercial sizes.

ISSN:0029-5639    

DOI:10.13182/NSE89-6

出版商:Taylor&Francis    

年代:1989

数据来源: Taylor

摘要:

AbstractExperiments done in several critical assemblies of the liquid-metal-cooled fast reactor type simulated core axial expansion, core radial expansion and bowing, coolant expansion, and control driveline expansion. For the most part, new experimental techniques were developed to perform these experiments. Calculations of the experiments basically used design-level methods except when it was necessary to investigate complexities peculiar to the experiments. It was found that these feedback reactivities generally are overpredicted, but the predictions are within 30% of the experimental values.

ISSN:0029-5639    

DOI:10.13182/NSE89-5

出版商:Taylor&Francis    

年代:1989

数据来源: Taylor

摘要:

AbstractGamma-dose analysis was performed on an absolute-value basis at the zero-power plutonium reactor (ZPPR)-13B/4 critical assembly, which was one of the benchmark radially heterogeneous 650-MW(electric) liquid-metal reactor cores, to validate the current data and methods applicable to power reactor design calculations. Discussions of particular aspects inherent to the critical measurements, such as heterogeneity in the ZPPR plate cells and delayed fission product gamma effect, are included. The results showed that the gamma-energy deposition distribution was reproduced within an accuracy of∼10% in cores that had complicated fuel and internal blanket layouts.

ISSN:0029-5639    

DOI:10.13182/NSE89-A28508

出版商:Taylor&Francis    

年代:1989

数据来源: Taylor