An Experimental Investigation of the Creep SAG of Pressure Tubes under LOCA Conditions

Abstract

During a postulated loss-of-coolant accident with impaired emergency cooling, the heat generated in the fuel will be transferred to the moderator. In the process, the pressure tube will heat and may deform into contact with its calandria tube. This paper describes experiments that were performed to investigate the sagging deformation of a pressure tube when a transient temperature is applied. The pressure-tube deflection and temperature were monitored. The contact between the pressure tube and calandria tube was observed, and the resulting type of boiling on the calandria-tube surface was noted, since this controls the rate of heat removal from the fuel channel. The experimental results were compared with computer predictions of the deformation. The computer models predicted the behaviour well.