High Temperature Fuel Channel Simulations Using CATHENA

Abstract

In postulated loss of coolant accidents with loss of emergency core cooling (LOCA/LOECC) events in a CANDU reactor; the loss of coolant from the heat transport system results in core voiding and, eventually, steam cooling of the fuel channels. At low channel steam flow rates, fuel and pressure tubes heat up and the pressure tubes may balloon or sag into contact with their calandria tubes, transferring heat to the moderator: A model has been developed to simulate the behaviour of CANDU 9 fuel channels under these low flow and high temperature conditions using the CATHENA themalhydraulics code. Typical predictions are given to illustrate the capabilities of the model. The model is used to predict fuel and pressure tube temperatures, hydrogen generation and heat load to the moderator: A comparison of the predictions of an open pin and a closed ring radiation model is also presented.