BWR MOX Core Physics Experiments and Preliminary Analysis

An experimental program, BASALA, has been planned to measure the main neutronic parameters of high moderation 100% MOX BWR mock up cores in the CEA-EOLE critical facility. The first part of the experiments that simulates hot operating conditions of BWR was completed by June 2001 The experiments include five critical cores: a reference core, an increased void core, two different type burnable poison cores and an increased water rod core. The measurement parameters are the critical mass and the core power distribution and the worth of the above-mentioned heterogeneities. The analysis has been done by NUPEC with a deterministic code, SRAC and a continuous energy Monte Carlo code, MVP, combined with the JENDL-3.2 nuclear data library. The preliminary results show that the critical keffs of the five cores are 1.004 to 1.008 for SRAC and about 1.009 for MVP, and the radial power distribution and the worth of the increased void, the burnable poisons and the increased water rods are well reproduced by both SRAC and MVP. The general trend of the analysis results has a good consistency with the previous experiments of the MISTRAL program.