BWR control blade depletion modeling in MICROBURN-B2

Control blade depletion is rigorously treated through microscopic depletion of B-10 atoms in the B₄C compound of neutron absorber. The depletion method is implemented in the MICROBURN-B2 core simulator and tested for actual BWR fuel cycles which have seen many control blade replacements. The effect on the hot operating condition is relatively small but not negligible if there is a large number of CR blades replaced during a fuel shuffle. The effect on cold critical cores, especially local critical state points, is favorable for eliminating some abnormal cold critical k-effective results. Combined with multiple control blade type simulation capability, the new model improves the accuracy of cold critical prediction. (author)