METHOD FOR IMPROVING RESIDUAL STRESS IN PIPE AND HIGH-FREQUENCY HEATING APPARATUS

摘要

PROBLEM TO BE SOLVED: To provide a method of conducting an operation for improving the residual stress in a pipe in a nuclear power generation plant, without needing a temporary closure of a nuclear reactor pressure vessel.

SOLUTION: This method for improving the residual stress comprises the steps of: fitting a high-frequency heating coil 16 of a high-frequency heating apparatus 10 to an arranged pipe 2 which is an object of treatment for improving the residual stress; heating the pipe from the external circumferential surface by using the high-frequency heating coil; and at the same time, cooling the pipe at a portion corresponding to the portion being heated, from the internal circumferential surface. The cooling method includes jetting a water jet 28 onto the internal circumferential surface of the pipe from a jet nozzle 27 of a coolant-jetting means 14, which is inserted into the pipe through an opening 29.

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