Thickness reduction of hydraulic connectors in ITER blanket shield block based on feasibility verification through mock-up testing

The hydraulic connectors of ITER shield block are joined to connectors of first wall and manifold using TIG welding, performed using a remote handling module. However, the originally designed 3 mm thickness imposes spatial constraints on the remote handling module, and non-destructive testing using eddy current inspection becomes increasingly challenging for thickness exceeding 3 mm. Therefore, a reduction of hydraulic connectors thickness was required. This study evaluates the feasibility of reducing the hydraulic connector thickness from 3 mm to 2.5 mm during series production, including 54 Sield Blocks already manufactured. Mock-up tests, consisting of machining and a hot helium leak test, were conducted to assess potential risk in dimensional accuracy such as concentricity and inner diameter deviations. The results indicated that the re-machining process for thickness reduction was the most significant factor affecting dimensional accuracy. In contrast, in the hot helium leak test, the reduced thickness had negligible effect on dimensional accuracy. Based on these findings, a support jig was implemented during re-machining process to prevent deformation caused by cutting forces and to ensure compliance with the required specifications. As a results, not only were all shield blocks successfully manufactured, but the re-machining process also benefited the ITER project by avoiding the significant time and budget expenditures that would have been required for more complex process involving cutting, re-welding, machining and inspection.