Validation study of the cell code WIMS-D and a 69 group library based on JENDL-3.2

A new 69-group library of multigroup constants for the lattice code WIMS-D/4 has been generated, processing nuclear data from JENDL-3.2 using NJOY91.108. A parallel ENDF/B-VI based library has also been constructed for inter-comparison of results. Benchmark calculations for a number of thermal reactor critical assemblies having both uranium and plutonium fuels have been performed with the code WIMS-D/4.1 with three different libraries: the 1986 WIMS library (NEA-0329/10) and the new JENDL-3.2 and ENDF/B-VI based libraries. The benchmark parameters calculated with the two new libraries show similar tendencies and are found in better agreement with the experimental values compared to those with the 1986 WIMS library. Benchmark parameters are further calculated with the comprehensive lattice code SRAC95. The results from WIMS-D/4.1 and SRAC95 agree well with each other as well as to the other previously published values except for lattices with higher plutonium contents. The disagreement is well resolved by an improved resonance treatment and ended up with a clear indication that the 1986 WIMS library with 13-resonance groups is not at all reliable for analysis of mixed oxide (MOX) cores of varying plutonium contents and for burn-up calculation of uranium-fueled cores.