Studies on Inspection Technology of Welding Joints for Spent Fuel Dry Casks

Japan Nuclear Energy Safety Organization (JNES) will perform a welding inspection of dry cask for the spent fuel which will be one of supporting activities on the regulatory body. It has been clearly demonstrated in laboratory and field studies plus field experience with actual and simulated components that the stress corrosion cracking (SCC) of stainless steel could occur at salinity simulating typical cask environment. A SCC-resistant stainless steel would be used for a canister of a concrete cask. The regulatory body required a multi-layered dye penetrant test (PT) and an ultrasonic test (UT) at a canister closure weld inspection of the canister because of difficulty of a radiographic inspection. Therefore applicability of the PT and the UT will be confirmed at the canister closure weld inspection of the canister, which is expected to be high humidity and high temperature at the welding and high temperature at the inspection, for new type of the stainless steel. JNES has planned and been performing experiments for welding inspection technology and procedures. The studies from 2005 to 2009 consist of a welding technology, material property test of canister body and welding portion, applicability experiments of the multi-layered PT and the UT using test peaces, welding technology test and welding inspection test by mock-up model and an evaluation of a critical flaw size at welding joints. Analyses results of canister temperatures are shown in Fig 1. These results were used for an establishment of welding experiment condition. This paper describes the experiment plan and results from studies in 2005 and 2006 which were material property test of canister body and preliminary experiments of the PT and the UT.