Heat transfer from a totally blocked fuel subassembly of a liquid metal fast breeder reactor: Part I. Experimental investigation

The safety issues of liquid metal fast breeder reactors (LMFBR) are crucial due to the fact that a highly reactive and hazardous fluid like liquid sodium is used as coolant. One of the extreme cases, which can occur in a fuel subassembly of an LMFBR, is a total blockage of liquid inside the subassembly, which may lead to boiling of sodium. The present study addresses this problem by conducting experiments on a 19-rod bundle assembly enclosed inside a tall hexagonal enclosure. Liquid sodium is used as the heat transfer fluid. The natural convection mode of heat transfer is the main focus of investigation with a co-flowing air through an annular packed bed to simulate the neighbouring subassemblies. The maximum temperature achieved under different rates of power generations and air flow conditions are observed. Also the radial temperature distributions at different planes under different operating conditions of power and air flow rates have been observed. The results are of significant importance for validating analysis for the purpose of prediction of boiling incipience in an LMFBR subassembly under totally blocked condition.