Two-Dimensional Modeling of Intra-Subassembly Heat Transfer and Buoyancy-Induced Flow Redistribution in LMFBRs (Liquid Metal Fast Breeder Reactors).

摘要

Phenomenological models and numerical techniques for prediction of coolant flow and temperature fields during forced, mixed, and free convection regimes of operation in LMFBR subassemblies are addressed. It is shown that, simplified integral solutions provide an excellent approach to assessing the importance of the intra-subassembly buoyancy induced flow redistribution, and the transverse thermal conduction and mixing effects on the assembly wide peak coolant temperatures. Furthermore, a more detailed steady-state and transient parabolic two-dimensional porous-body model, resulting in the TWIST computer code is developed. Comparison of calculated results and out-of-pile sodium and water test data indicate generally good agreement in cross-assembly temperature profiles. However, the impact of fuel pin distortion and bowing, caused by large transverse power gradients on transverse temperature distributions are found to be significant.