Helium leak detection methods using temperatures of a canister bottom and air at an inlet

摘要

The aging management of spent nuclear fuel has received increasing attention worldwide. The loss of containment by stress corrosion cracking (SCC) on the canister surface of the concrete cask has been concerned. However, a detector of a helium leak from the canister has not been installed. In light of further improvement of the safety, the containment of the concrete cask should be monitored on a steady basis as well as the metal cask. For development of the detector, we experimentally confirmed that when the internal pressure of the canister decreased, the temperature of the upper part of the canister decreased and the temperature of the bottom of the canister increased. Based on this phenomenon, we had proposed a method using the temperature difference between the top and bottom of the canister for leak detection. This method requires the temperatures at two points on the canister surface; however, it would be difficult to install a temperature sensor on the canister bottom in the case of an air flow channel with a complicated shape. Thus, we have been investigating an easier technique that the leak could be detected by temperature information only at one of the two points on the canister. A method using ambient temperature at the top of the canister has already been developed, and this paper introduced new detection methods using the temperatures of the bottom of the canister and air at its inlet.