Abstract

A laser desorption mass spectrometer microprobe has been utilized to map Li distributions in CANDU^® nuclear reactor components. Lithium is present in the Heat Transport System (HTS) of the reactor and can be used as a tracer of HTS leakage. Leakage (in the form of both liquid D₂O and steam) into component crevices, introduces uncontrolled and unknown chemistry within the crevices. One such area is the rolled joint, where the zirconium pressure tube is rolled into the stainless steel end fitting hub. HTS leakage, occurring through cracks and crevices under the rolled joint, may lead to deuterium ingress into the Zr pressure tube and subsequently to pressure tube embrittlement. It is hoped that the results from the laser desorption microprobe, can be used to correlate the HTS leakage through the cracks and crevices under the rolled joint with the deuterium profile in the pressure tube. The laser desorption technique was found to be very sensitive and could provide semi-quantitative Li distributions either at low spatial resolution (the length of the 20 cm hub section) or high spatial resolution (revealing Li in micron sized cracks). Other traditional surface science techniques like SAM and XPS are not sensitive to Li, and commercial SIMS instruments cannot accommodate the large hub samples nor allow for profiling over the hub length.

© 1998 Optical Society of America