Bruce A Unit 1 Moderator to End Shield Cooling Leak Repairs

Abstract

In October 1994, a leak developed between the heavy water Moderator System and the light water End Shield CoolingSystem at Ontario Hydro's Bruce A Generating Station Unit 1. The interface between these two systems consists ofnumerous reactor components all within the reactor vessel. This paper describes the initial discovery anddetermination of the leak source. The techniques used to pinpoint the leak location are described. The repairstrategies and details are outlined. Flushing and refilling of the Moderator system are discussed. The current status ofthe Unit 1 End Shield Cooling System is given with possible remedial measures for clean-up. Recommendatiot~s andobservations are provided for future reference.