Proposal of new U nuclear data to improve k biases on U enrichment and temperature for low enriched uranium fueled lattices moderated by light water

Wu, H.; Okumura, Keisuke ; Shibata, Keiichi

The under prediction of k depending on U enrichment in low enriched uranium fueled systems was studied in this report. Benchmark testing was carried out with several evaluated nuclear data files, including the new uranium evaluations from preliminary ENDF/B-VII and CENDL-3.1. Another problem reviewed here was k underestimation vs. temperature increase, which was observed in the slightly enriched system with recent JENDL and ENDF/B uranium evaluations. Through the substitute analysis of nuclear data of U and U, we propose a new evaluation of U data to solve both of the problems. The new evaluation was tested for various uranium fueled systems including low or highly enriched metal and solution benchmarks in the ICSBEP handbook. As a result, it was found that the combination of the new evaluation of U and the U data from the preliminary ENDF/B-VII gives quite good results for most of benchmark problems.