Radial and Azimuthal ~(235)U Fission and ~(238)U Capture Distributions in BWR UO_2 Pins: CASMO-4 and MCNP4C: Versus Activation Foil Measurements

摘要

In the context of the LWR-PROTEUS program, radial and azimuthal ~(235)U fission (F_5) and ~(238)U capture (C_8) rate distributions have been calculated for zero-burnup pins of a Westinghouse SVEA-96 Optima2 boiling water reactor fuel assembly using the stochastic MCNP4C and the deterministic CASMO-4 codes. The within-pin F_5 distributions predicted by the two codes are in very good agreement; the C_8 distributions are more pronounced, and there are significant discrepancies between the codes, both azi-muthally and radially. The calculations have been compared with experimental results obtained from activation foil measurements in two pins of the assembly irradiated in the center of the PROTEUS test zone. The measurements confirm that the two codes can accurately predict the radial and azimuthal F_5 distributions but that MCNP4C within-pin C_8 distributions are much more accurate than those of CASMO-4.