Further Simulation of the Pressure Tube Circumferential Temperature Distribution Experiments (Make-up Water Experiments)

Abstract

Under some postulated accident scenarios in a CANDU reactor, some fuel channels may experience periods of stratified flow in which the top portion of the pressure tube and fuel elements are exposed to superheated steam while the bottom portion is cooled with water. As a result, the upper part heats up and a temperature gradient is developed around the circumference of the pressure tube. This temperature gradient could result in a nonuniform or localized pressure tube strain which could lead to failure of the pressure tube prior to contacting the calandria tube. The pressure tube circumferential temperature gradient experimental program (PT-DELTA n has been ongoing at AECL-WNRE under COG to investigate the potential of pressure tube rupture during ballooning, prior to contacting the calandria tube, in pressure tubes exposed to stratified coolant conditions. The main objective of this paper is to discuss the simulation results of three of the Make-Up Water experiments using the SMARTT (Simulation Method for Azimuthal and Radial Temperature Transients) [l] computer code and to compare with the experimental results for code verification. A discussion and analysis of the information gained from these experiments are presented.