Effect of incoherency on voiding dynamics in LMFBR wire-wrapped subassemblies

Current accident analysis tools (SAS, etc.) are based upon one-dimensional treatment of the sodium behavior in wire-wrapped subassemblies under accident conditions. As such, calculated values of sodium voiding rates (in the case of loss of flow (LOF) with failure to scram) and dryout and cladding failures (in the case of loss-of-pipe integrity (LOPI) with scram) are on the conservative side in view of the large radial temperature gradients existing at boiling inception. The purpose of this paper is to discuss the intrasubassembly incoherence effects including proposed modeling and experiments to determine the magnitude of these effects in a full-size LMFBR subassembly