SCC Tests of the canister for spent nuclear fuel storage using full scale lid model

To verify the effectiveness of surface treatment techniques to the commercialized canister, the mock-up lid part of the canister made of SUS304L with a full-scale diameter was manufactured. Parts of the weld line were treated by the Low Plasticity Burnishing (LPB) technique to mitigate the residual tensile stress. An accelerated corrosion test was executed with the mock-up canister, in which the salt concentration on the surface of the weld lines was set to 4g/m2 as chloride. The test conditions were set at a constant temperature of 80°C with relative humidity RH=35% over 5000 hours. After the test, visual inspections and fluorescent penetration tests (PT) were executed along all of the weld lines and the suspicious areas for the occurrence of SCC were detected. The suspicious areas were selected by PT indications and cut into small plates. Using these plates, surface cracks and cross-section of the cracks were observed with optical microscope. This paper presents the results of the investigation and the effectiveness of the LPB technique.