Development of OPR1000 RCS Hot-leg surge nozzle thermal sleeve remote removal system

Abstract

The OPR1000-type reactor incorporates seven thermal sleeves (T/S) within the reactor cooling system (RCS) piping line, constructed from Inconel-600 or Inconel-690 material, depending on the power plant. In instances involving T/S made of Inconel-690 material, certain issues were identified either initially or at the commencement of operations. Consequently, the T/S installed on the safety injection nozzle was promptly removed. However, the T/S affixed to the hot-leg surge nozzle remained in operation without removal. Subsequent ultrasonic testing, conducted as part of the scheduled preventive maintenance period, revealed that the T/S associated with the hot-leg surge nozzle in the RCS pipe exhibited protrusions attributable to eccentricity and groove wear. Consequently, the removal of the T/S became imperative. This study delineates the development timeline of a remote system and highlights significant milestones achieved in the removal of the hot-leg surge nozzle T/S during the planned preventive maintenance period.