THE SWAN CODE FOR MINIMUM CRITICAL MASS AND MAXIMUM K_(eff) DETERMINATION

摘要

The perturbation theory based methodology incorporated in the code SWAN to make it applicable to minimum critical mass (MCM) or maximum K_(eff) determination is described. The applicability of the upgraded SWAN to MCM determination is illustrated for thermal systems consisting of ~(239)Pu and any possible combination of H_2O, polyethylene, Be, SiC and Pb. The smallest MCM is obtained using polyethylene for the inner 8cm and Be for the outer 3 cm of a spherical core, and Be for the reflector; it is less than 1/4 of the MCM obtained using H_2O for both the moderator and reflector. The optimal ~(239)Pu distribution has a pronounced peak at the polyethylene boundary with the Be. The upgraded SWAN code can be a very useful tool for criticality safety analysis.