Helium leak detection method using ambient temperature of canister top

The aging management of long-team storage of spent fuel and the monitoring method of integrity of fuel are attracting interest more than ever in the world. In a concrete cask, the loss of sealing performance of a canister, which is caused by stress corrosion cracking (SCC), is concerned in the case of the long-term storage. However, a helium leak detector is not installed to the concrete cask yet. A phenomenon that the temperature at the top of the canister decreases and the temperature at the bottom of the canister increases as helium gas in the canister leaks has been confirmed experimentally. We have proposed the helium leak detection method by using temperature difference between the top and the bottom of the canister. This method requires temperature information at two points of a canister top and bottom; therefore, depending on a flow channel structure for cooling air of the cask, there might be difficulties when temperature sensors are installed initially. To resolve such a problem, we newly devised an easier detection method using only the temperatures of the canister top and its ambient temperatures.