Reliability in NDT of Canister for the Swedish Spent Nuclear Fuel

摘要

The Swedish KBS-3 design for the disposal of spent fuel is based on encapsulation of the fuel in canisters consisting of cast iron inserts and an outer 5 cm thick shield of copper. The canisters are embedded in bentonite clay and will be disposed in crystalline bedrock at a depth of about 500 m. To verify that the canisters fulfil the requirements, an extensive program for quality control is developed. In this program the use of NDT is vital and therefore it is very important to determine the reliability of the developed NDT methods. The reliability of the NDT methods has been studied for six years and the results are used in several ways. One task is to identify areas where further optimizations of the NDT methods are necessary and another is to study the effect of influencing parameters prior to the upcoming qualifications. Furthermore, the reliability analyses of the NDT are combined with analyses of the manufacturing and welding processes to give input to the overall safety analyses of the long-term properties of the canisters.