Analysis of benchmarks on the reactivity temperature coefficient using new libraries based on ENDF/B-VI (release 5) and JEF2-2 data

This paper presents, the analysis of discrepancies between calculation and experiments in the prediction of isothermal moderator temperature coefficient of a set of lattice experiments, using WIMSD4, WIMSD5B and APOLLO1 lattice codes. In this analysis we have used the original cross sections libraries (CEA-86 library for APOLLO1 and both of 1981 and 1986 libraries for WIMS) and the updated ones based on JEF2.2 data for APOLLO code and both of ENDF/B6 and JEF2.2 data for WIMS code. We have also analysed the numerical benchmark proposed by Mosteller to evaluate the accuracy in predicting Doppler coefficient in light water type lattices. This study on Doppler coefficient was performed using, in addition to APOLLO and WIMS codes, the Monte Carlo code MCNP4B for which a new library based on ENDF/B6 nuclear data file, have been processed using the NJOY system.