SIMPLIFIED INTERASSEMBLY HEAT-TRANSFER MODEL FOR THE ANALYSIS OF LIQUID-METAL FAST BREEDER REACTOR CORE RESTRAINT SYSTEMS

A simplified interassembly heat transfer model has been developed to satisfy liquid-metal fast breeder reactor core restraint system analysis needs that explicitly treats steady-state intra-assembly and interassembly heat transfer in core assemblies. The intra-assembly heat transfer inside reactor assemblies is modeled based on application of the subchannel concept together with the use of bulk parameters for coolant velocity and coolant temperature within a subchannel. The model utilizes a tri-grid system to treat interassemnbly heat transfer between assemblies. Because of this special nodal scheme, a set of finite difference equations, derived from the energy equation for all the subchannels, duct wall, and gap flow, is actually a rather special system of simultaneous linear algebraic equations which have a tri-diagonal matrix form.