CANDU PHWR Feeder Pipe FAC Mitigation Design Modification and Validation During Operation

Flow accelerated corrosion (FAC) is the main reason for Feeder pipe wall thinning in CANDU pressured heavy water reactor (PHWR). Atomic Energy of Canada Limited (AECL) made design modification for Third Qinshan Nuclear Power Plant (TQNPP) to mitigate Feeder pipe FAC rate by increasing Cr content to more than 0.2 wt % and control primary heat transport system (PHTS) pH value between 10.2–10.4, more than 4 years laboratory verification test proved the modification was effective. More than 10 years in-service inspection performed by TQNPP proved that real Feeder pipes FAC rate is less than designed value; TQNPP Feeder pipe can meet the design life and even extend the service life.