Criticality calculation for cluster fuel bundles using grey Dancoff factor

This paper applies the grey Dancoff factor calculated by Monte Carlo method to the criticality calculation for cluster fuel bundles, Dancoff factors f or five symmetrically different pin positions of CANDU37 and CANFLEX fuel b undles in full three-dimensional geometry are calculated by Monte Carlo met hod. The concept of equivalent Dancoff factor is introduced to use the grey Dancoff factor in the resonance calculation based on equivalence theorem. The equivalent Dancoff factor which is based on the realistic model produce s an exact fuel collision probability and can be used in the resonance calc ulation just as the black Dancoff factor. The infinite multiplication facto rs based on the black Dancoff factors calculated by collision probability o r Monte Carlo method are overestimated by about 2 mk for normal condition a nd 4 mk for void condition of CANDU37 and CANFLEX fuel bundles in compariso n with those based on the equivalent Dancoff factors. (C) 1999 Elsevier Sci ence Ltd. All rights reserved.