3-D Monte Carlo and discrete ordinates void coefficient analysis for the Los Alamos National Laboratory Omega west reactor using MCNP and threedant

Three-dimensional Monte Carlo and discrete ordinates computational modeling techniques have been used to characterize void coefficient behavior for three experimental channels and several fuel assemblies in the Los Alamos Omega West nuclear reactor using MCNP and THREEDANT. Good agreement is observed in void coefficient behavior predicted by MCNP and THREEDANT. The experimental-channel gross-voiding calculations predict the existence of positive void coefficients due to overmoderation conditions. The fuel assemblies exhibit, for the most part, negative void coefficients, although the possibility of localized small positive void coefficients for one of the five assemblies analyzed is indicated.