Secondary Criticality Evaluations of Postulated Core Melt-Down Accidents in Early-Sized LMFBR's

Secondary criticality analyses have been performed for an early-sized LMFBR. The results indicate that recriticality will occur only as a result of extremely unlikely combinations of failures which lead to meltdown of a large portion of the reactor core, subsequent formation of a relatively pure fuel layer, and/or substantial vessel deformation. Design features were identified that could be used to eliminate recriticality or mitigate its effects if needed to meet safety requirements. The presently existing large uncertainties in the containment response and radiological consequences of single or multiple recriticalities may be reduced with the aid of dynamic analyses that couple neutronic, thermal, and hydrodynamic methods.