Tooling to Obtain Samples of Pressure Tube Material in Reactor for Deuterium Analysis

Abstract

Pressure tube integrity and life are major long-term concerns in CANDU reactors where recent tube failures have contributed significantly to loss of capacity. Extensive work has been done to demonstrate pressure tube integrity. However, the present method of assessing the useful life of pressure tubes in CANDU reactors requires the periodic removal of a tube. Samples are cut from the removed tube and analysed for deuterium (D2) content. The D2 concentration is then used as a measure of the useful life of the remaining pressure tubes. This approach is very costly because of the long shutdown required to remove and replace a pressure tube. To significantly reduce this cost, special tooling was developed at Chalk River Nuclear Laboratories (CRNL) to cut a sample from a pressure tube without removing the tube from the reactor. Only a small amount of material is removed for D2 analysis (about 50 mg), and the contour of the cut is carefully controlled so that tube integrity is preserved. This paper describes the tool and its development and discusses the results of laboratory and in-reactor tests.