Simulation and Analysis of the Thermal and Deformation Behaviour of 'As-Received' and 'Hydrided' Pressure Tubes Used in the Circumferential Temperature Distribution Experiments (End of Life/Pressure Tube Behaviour)

Abstract

It is postulated that in-reactor pressure tubes may be subjected to radiation damage and dissolved deuterium which could change the pressure tube characteristics and lead to different behaviour than that of as-received pressure tubes under large LOCA conditions. A hydrided pressure tube was used to study the effect of dissolved hydrogen on thermal-mechanical behaviour. In the experiment, simulating an in-reactor (hydrided) pressure tube with circumferential differential temperature under boil-off conditions, the pressure tube ballooned into contact with the calandria tube. The pressure tube used in this experiment was hydrided in a furnace to a nominal value of 200 pg/g dissolved hydrogen. This test was a repeat of the first supplementary boil-off test (S-5-1) [1] which used an as- received pressure tube. The objective of this paper is to analyze the results obtained from the simulation of this Boil- Off test using the SMART! [2] computer code and to examine the effect of hydriding on the thermal and ballooning behaviour of the pressure tube by comparison with the results obtained from test S-5-1. A discussion of the results obtained from this comparison is presented together with an analysis of their application to the analysis of pressure tube behaviour in CANDU reactors.