Energy Group Structures and Minimum Critical Mass

The Goertzel reactor construct and the Goertzel-Wilkins theorem proved for this class of reactors are applied to a moderator fuel system at pressurized water reactor temperature and pressure conditions. The viability of the minimum critical mass as a global parameter to assess the integrity of energy group structures is investigated. The calculations are performed in diffusion and transport theory and up to eight energy groups are considered. Some initial guidelines based on the minimum critical mass for attaining nearly equivalent accuracy by using a fewer number of “properly” structured energy groups are discussed. Numerical results are still inconclusive but again suggest that transport theoretical calculations are pointless unless spectral codes that compute group constants include angular dependence.