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ENDF/B-V, LIB-V, and the CSEWG benchmarks
[report]

R.B. Kidman

1981
unpublished

A 70-group library, LIB-V, generated with the NJOY processing code from ENDF/B-V, is tested on most of the Cross Section Evaluation Working Group (CSEWG) fast reactor benchmarks. Every experimental measurement reported in the benchmark specifications is compared to both diffusion theory and transport theory calculations. Several comparisons with prior benchmark calculations attempt to assess the effects of data and code improvements. I. INTRODUCTION Periodically, accumulated reactor physics
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... reactor physics improvements need to be tested on standard problems (benchmarks) to mark progress and establish a set of results that can be referred to in the future. This reporr. documents the use of 17 benchmarks to test the combined effects of several improvements: ENDF/B-V data, 2 NJOY 3 processing, and SUPERX, ONETRAN, 4 and SUPERB computations. This report can be considered a sequel to an earlier report 5 in which calculations were based on ENDF/B-IV data, 2 MINX 6 preparation, and IDX, 7 ONETRAN, and PERTV 8 computations. ENDF/B-V is, of course, a more recent version of evaluated nuclear data than is ENDF/B-IV. NJOY is a more comprehensive, updated version of the MINX processing system. SUPERX and SUPERB are unpublished, overhauled versions of 1DX and PERTV, respectively, that incorporate the following changes. 1. Improved f-factor interpolation 2. Improved elastic downscatter iteration 3. Elastic scattering transfer matrices Elastic downscatter f-factors A new transport cross section computation 6. Isotope and region-dependent fission source matrices To study or compare results of this document, Refs. 1 and 5 would be helpful. II. PROCEDURE The NJOY code was used to generate 70-group cross sections in the CCCC-IV 9 format for 93 of the materipls in the ENDF/B-V data tapes. The LINX 10 code was then Used to form a composite 93-isotope CCCC-IV library from the separate materials. This library is called LIB-V * and its documentation contains the details of its generation. The group structure is shown in many of the tables of Appendix B. LIB-V was processed with the weight function (log-log interpolation between points) shown in Table I . The weight function is intended to model the spectra encountered in fast-reactor benchmark testing and the 14-MeV fusion peak. The resulting group-wise function is also shown in Table I . The computer code CINX 12 (modified to pass along elastic removal f-factors, elastic scattering matrices, and isotope chi matrices) was then used to put LIB-V into the format required by SUPERX. The elastic and inelastic transfer cross sections from CINX were arbitrarily limited to 32 downsc^ttering terms (32 includes the in-group term). Composition-and temperature-dependent effective cross sections for each benchmark were then generated by using SUPERX. Finally, effective cross sections, fluxes, and adjoints from SUPERX were fed Into SUPERB for the calculation of diffusion theory material worths. The effective cross sections from SUPERX were also fed into ONETRAN to produce Pl/Zi S ;b transport theory fluxes and adjoints that in turn were fed into SUPERS for the calculation of transport theory material worths. The group velocities and ENDF/B-V delayed neutron data used by SUPERB are presented in Appendix A. This description of procedures and data should enable one to reproduce any of the results reported here. III. RESULTS All of the computed results and comparisons with every experimental measurement are compiled in Appendix B. This compilation contains some additional transport theory results not included with the previous calculations. 5 The 70group central flux, edge flux, central adjoint, and edge adjoint are shown. The 70 x 70 region-dependent chi matrices have been appropriately collapsed (weighted by volume, flux, and neutron production) to 70-group vector chi's for the reactor and each region. These vector chi's allow a better understanding of the Definition Point Energy (eV)

doi:10.2172/6049033
fatcat:cnhqowm6uffx7gtczkrrqyosu4