REMOVAL METHOD OF MACHINED LAYER, RESIDUAL STRESS IMPROVEMENT METHOD OF NUCLEAR STRUCTURAL COMPONENT, AND CORE SHROUD REPLACEMENT METHOD

摘要

PROBLEM TO BE SOLVED: To provide a removal method of a machined layer capable of further reducing a stress corrosion cracking of a structural component.SOLUTION: After shutdown of operation of a BWR, a core shroud is cut and taken out (step 33), and inspection inside the RPV is executed (step 34). A stress improvement countermeasure is executed to a weld zone and its periphery of a structure in the RPV (step 35). A compressive residual stress is applied to the weld zone or the like by the stress improvement countermeasure. Then, a machined layer formed by the stress improvement countermeasure is removed (step 36). Removal of the machined layer is performed by electrolytic polishing. Electrolytic polishing liquid is injected up to a prescribed level in the RPV, and a counter electrode is arranged on the periphery of the weld zone to be subjected to electrolytic polishing. A current is sent between the counter electrode and the RPV to remove the machined layer formed on the weld zone. Thereafter, the compressive residual stress is applied to the part from which the machined layer is removed by water jet peening.