New WIMS Library Generation from ENDF/B6 and Effect of Resonance Group Structure on Cell Parameters

摘要

Due to inaccessibilty to NJOY, steps were taken to create WIMS library, which can be extracted from ENDF/B6 without using NJOY. In addition to using preprocessing codes few programs were written to calculate integral resonance, slowing down power per unit lethargy, potential scattering, and differential scattering cross section, scattering matrices. For neutrons with energy above 4eV, isotropic elastic scattering was assumed. For neutrons below 4eV the free gas model was used, except for light elements, which tabulated values of S(α,β) in ENDF/B6 used. The Goldstein-Cohen factors are taken from WIMKAL88. Lib. The integral resonance with self absorption per unit lethargy was obtained from GROUPIE output. The P_1 scattering matrices are calculated only for four elements, namely H,D,C and O at 300K In order to examine the created libraries, k_(eff), δ~(28), ρ~(28), ρ~(25) and CR are calculated using new WIMS library, WIMKAL88.Lib and NEA329.Lib The results showed general agreement. The controversial issue of WIMS library group structure, particularly in resonance region has raised the question of whether the number of resonance group i.e., 13 is optimized. We generated different WIMS libraries consisting of 5, 8, 13, 18 and 23 resonance groups. The main aim was to examine the effect of resonance group structure on calculated core parameters, mainly k_(eff), δ~(28), ρ~(28), ρ~(25) and CR. These parameters are also calculated and compared with those obtained using WIMKAL88, and NEA329 libraries.