Development of evaluation method of long-term confinement performance for canister. Part 2. Helium leak analyses and proposition of simpler helium leak detection method

The management of long term storage for spent fuel and the monitoring method of the integrity are attracting interest more than ever in the world. In a concrete cask, a phenomenon that the temperature at the top of a canister decreases and the temperature at its bottom increases as the helium gas in the canister leaks has been confirmed by experiment. We performed two dimensional compressible gas analysis using models having heat source and heat conductive solid in a cavity for the phenomenon. Then, we verified the mechanism of the phenomenon that was observed in the experiments by the numerical analysis. In the previous study, we have proposed a helium leak detecting method using the temperature deference between the top and the bottom of the canister. However, the temperatures at the top and bottom surfaces of the canister are needed in this method, which will be difficult to install temperature sensors in some cask structures. To resolve this problem, we proposed easy detecting methods using temperature information only at one side of the top or the bottom of the canister. (author)