Study on spent fuel storage by concrete cask for practical use. Applicability evaluation of ultrasonic test with imaging analysis for type304L stainless steel canister lid weldment

For the practical use of the multi-purpose canister made of austenite stainless steel, remaining issue is its demonstration of the ultrasonic test (UT) inspection methodology for the lid weldment to verify the confinement ability of the canister. In this study, the full-scale canister lid model made of type 304L stainless steel with artificial defect by electro-discharge machining weld defects was fabricated. Image reading technique using ultrasonic images collected by phase array ultrasonic examination equipment was applied at room temperature and the collected images were compared with macroscopic test results. As a result, the accuracy of the UT with imaging analysis was verified and the detectable flaw size-limit was proposed. Finally, as the applicability of the proposed method to faulty weld defects was also demonstrated, the feasibility of the UT inspection method application to the canister lid weldment was confirmed. Moreover, the problems to be solved, such as the reliability under the high temperature condition and the countermeasures for the excess surface lid weldment, were discussed. (author)