Assessment of the consequences of boiling in the radial blanket due to hypothetical major pipe leaks

Boiling initiation in a liquid-metal fast breeder reactor (LMFBR) has in the past been assumed to lead inevitably to the potential for loss of coolable geometry. To ensure conservatism, it was necessary to preclude boiling under all accident conditions. Limited boiling in the radial blanket of the Clinch River Breeder Reactor due to a hypothetical major leak in the primary heat transport system is not likely to lead to assembly-wide dryout and cladding melting. A series of scoping calculations based on applicable physical processes has shown that (a) boiling is likely to be limited to only six subchannels, (b) flow reversal is unlikely, (c) there are ample heat sinks for condensation of sodium vapor, (d) film dryout is unlikely, and (e) cladding melting is unlikely. The consequences listed are of continuously decreasing likehood, hence providing confidence that coolable geometry is not threatened by limited boiling in the radial blanket. This analysis was performed for a conventional LMFBR core arrangement