Experimental investigation of heat transfer during LOCA with failure of emergency cooling system

Abstract

Paper presented at the 5th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, South Africa, 1-4 July, 2007.

The pressure tubes (PT) in the Indian Pressurized Heavy Water Reactor (PHWR) are kept concentrically inside horizontal calandria tube (CT), which is submerged in a moderator pool. During postulated loss-of-coolant accident (LOCA) without emergency core cooling system, the temperature of PT could rise significantly. At elevated temperature, the weight of the PT with the weight of fuel pins could cause it to sag. Before sagging heat transfer from the PT to CT is mainly by convection. Once the PT sags and touches the CT, heat transfer mode changes to conduction. Direct contact between the PT and CT increases heat transfer and checks the temperature rise of the PT and limit the fuel heatup and subsequent degradation of the reactor core. An experimental set-up is designed and fabricated at Indian Institute of Technology Roorkee (IITR) to simulate the LOCA in the Indian PHWR. From the experimental investigation, it is found that the contact between the PT and CT occurred at around 300 seconds after the initiation of the simulation with corresponding temperature of the PT at around 680°C. The experiment was continued after the contact between the PT and CT and it is found that the temperature rise of the PT was within 800°C. This work demonstrates the inherent safety feature of Pressurised Heavy Water Reactor.