LWR-PROTEUS verification of reaction rate distributions in modern 10 x 10 boiling water reactor fuel

HELIOS, CASMO-4, and MCNP4B calculations of reaction rate distributions in a modern, fresh 10 x 10 boiling water reactorfuel element have been validat ed using the experimental results of the LWR-PROTEUS Phase I project corres ponding to full-density water moderation conditions (core 1B). The reaction rate distributions measured with a special gamma-scanning machine employin g twin germanium detectors consisted of total fission F-tot and U-238-captu re C-8. The average statistical errors for the gamma scans were better than 0.5% for F-tot and 0.9%for C-8. The rod-by-rod measurements were performed on 60 different fuel rods selected from the central part of a test zone co nsisting of actual, fresh SVEA-96+ fuel elements, thus gaining in realism b y departing from conventional fuel rod mockups. In the case of F-tot, the r oot-mean-square (rms) of the rod-by-rod distribution of differences between calculational and experimental (C-E) values has been found to be 1.1% for HELIOS and for CASMO-4, and 1.3% for MCNP4B. For C8, the rms values of the (C-E) distributions are 1.0, 1.3, and 1.4% as obtained with HELIOS, CASMO-4 , and MCNP4B, respectively. The effects of using different data libraries ( ENDF/B-V, ENDF/B-VI, and JEF-2.2) with MCNP4B were also studied and have be en found to be small.