Simulation methodology for pressure tube integrity analysis and comparison with experiments

The computer code SMARTT (Simulation Method for Azimuthal and Radial Temperature Transients) is used in safety analysis of CANDU reactors to predict fuel and pressure tube thermal and mechanical behaviour under asymmetric coolant conditions such as stratified flow. This paper presents comparisons of SMARTT predictions with preliminary results of two experiments in which large temperature non-uniformities developed on pressure tubes undergoing heatup and transverse strain at 1.0 MPa internal pressure. Temperature asymmetries developed as a result of slow boil-off of coolant in the channel. The SMARTT temperature predictions are shown to agree well with the experimental results. SMARTT accurately predicts the time at which the pressure tube balloons into contact with the calandria tube. The transient liquid level in the channel can also be accurately predicted using a simple venting/boil-off model