Fabrication and characteristic of the 316L(N)-IG forged block and rolled plate for application to ITER blanket shield block

The austenitic stainless steel 316L(N)-IG (ITER Grade) is mainly employed for the structural material of the core machine considered for the in-vessel components of the ITER, which require good resistance to corrosion, weldability and mechanical properties at elevated temperature. The ITER blanket Shield Block (SB) is one of the in-vessel components and, it has to be made with 316L(N)-IG. The SB has a rather complex internal cooling channel to remove the nuclear heat from cooling water. For this structural reason, it is necessary to weld with dozens of small cover plates after manufacturing the cooling channel to make a closed circuit. This could cause a risk of possible water leakage due to technical difficulties and/or limitations of volumetric non-destructive inspection on small welded cover plates with geometrical constraints. Therefore, it is important to have verification of the Ultrasonic Testing (UT) for more accurate defect detection. The present study describes the entire fabrication process and characteristic of the 316 L(N)-IG, which are different fabrication types of the forged block and rolled plate. The study also provides the microstructure on the welded joint between the forged block and rolled plate using the Electron BackScattered Diffraction (EBSD) analysis. Based on this results, we dicussed that the effects of change of grain size on the UT signal in the weldment.