Use of integral experiments for the assessment of a new²³⁵U IRSN-CEA evaluation

Abstract

Abstract. The Working Party on International Nuclear Data Evaluation Co-operation (WPEC) subgroup 29 (SG 29) was established to investigate an issue with the 235 U capture cross-section in the energy range from 0.1 to 2.25 keV, due to a possible overestimation of 10% or more. To improve the 235 U capture crosssection, a new 235 U evaluation has been proposed by the Institut de Radioprotection et de Sûreté Nucléaire (IRSN) and the CEA, mainly based on new time-of-flight 235 U capture cross-section measurements and recent fission cross-section measurements performed at the n TOF facility from CERN. IRSN and CEA Cadarache were in charge of the thermal to 2.25 keV energy range, whereas the CEA DIF was responsible of the high energy region. Integral experiments showing a strong 235 U sensitivity are used to assess the new evaluation, using Monte-Carlo methods. The k ef f calculations were performed with the 5.D.1 beta version of the MORET 5 code, using the JEFF-3.2 library and the new 235 U evaluation, as well as the JEFF-3.3T1 library in which the new 235 U has been included. The benchmark selection allowed highlighting a significant improvement on k ef f due to the new 235 U evaluation. The results of this data testing are presented here.

The joint evaluated fission and fusion nuclear data library, JEFF-3.3

“…A total of 238 ICSBEP benchmark cases [374] were selected by IRSN for the thermal, intermediate and fast energy range. The diversity of media and configurations makes these benchmarks representative of criticality safety considerations for fuel cycle operations.…”