Fatigue evaluation of PHTS pumps for a domestic CANDU nuclear power plant

Fatigue evaluation on primary heat transport system pumps (33122) for a domestic CANDU nuclear power plant ware carried out as a part of a Plant Lifetime Management (PLIM) study. A methodology used in performing the evaluations was based on the NUREG-1800 and the evaluating were carried out for the pressure boundary regions based on the number of design and operating transients with consideration of environmental effects. The cumulative usage factors(CUFs) of PHTS pumps were identified high in order of Stuffing Box's Cooling Hole, Cutwater Region, Outlet Region, and etc. The stuffing box's cooling hole among these regions was evaluated that the fatigue usage factor for 50 years operation based on the design transients exceeded 1.0. But, the reevaluated cumulative usage factor based on the operating experience was below allowable limit. From the results of fatigue evaluations for the PHTS pumps, it is concluded that the fatigue will not be a significant safety issue even considering additionary 20 years continued operation