D.F. Torgerson Award: Electrical resistivity variation assessment

Mark Luloff and Jeffrey Olfert 

For the impact of electrical resistivity variation on the assessment of fuel channel to calandria gap. 

Previously, high-accuracy measurement of electrical resistivity in the hot cell environment was not achievable and the electrical resistivity variations in irradiated material (+/- <5%) had not been observable. This work developed and implemented this capability at CNL. Through the work, electrical resistivity evolution has been correlated with pressure tube microstructure evolution in the reactor, and the electrical resistivity measurements capability are being used to further characterize pressure tube (PT) microstructure, at a fraction of the cost of destructive examinations. Future work is expected to benefit delayed-hydride cracking-rate and hydrogen ingress studies. The in-cell electrical resistivity results have enabled the use of analytical modeling for simulating the PT and calandria tube (CT)

eddy-current gap-probe response, which allows the effect of many influential parameters to be studied. This is at a fraction of the cost of an empirical study with physical samples. Due to this work, improvements to PT/CT gap measurement accuracy are also being undertaken, and this has allowed the utilities to demonstrate high confidence in their PT/CT gap measurements to the Canadian Nuclear Safety Commission.

From the start, this research was 100 per cent funded through the CANDU Owners Group (COG), and its success has enabled further commercial work from COG and follow on work directly with the utilities. In the past two years, the nominees have been routinely asked to present on the topic at industry seminars, and are now recognized as experts by the industry. The nominees’ expertise in this area was specifically recognized by the highest levels of the Bruce Power executive during a recent commercial project. Papers on this topic have also been published in the open literature, and more articles are planned in the coming months / years.