Valcor Engineering Corporation of Springfield, New Jersey, provided an update to the Nuclear Regulatory Commission (NRC) on a defect in a solenoid operated valve used in the Westinghouse AP-1000 nuclear reactor design approved by the NRC in 2005. The defect, a crack through the thickness of the valve seat in a test model operated at high temperature, was first reported to the NRC in Jan. 2014. At that time Valcor said that the crack “caused the valve to leak in the closed position beyond its Technical Specification requirement.”
In the update, Valcor said that initial computer flow and thermal analysis “suggest that the design is adequate and that stress induced by rapid temperature rise would not cause the seat to crack.” But when two more valves was actually tested under high temperature:
Contrary to all stress/thermal analysis, cracking of (the) valve seat was reproduced (in) early June when one of the above mentioned bodies was subjected to the same thermal shock condition that caused the initial observed cracking.
Valcor’s Event Report said that solenoid controlled valves of the type that failed “have been delivered to Westinghouse for installation in the Sanmen and Haiyang nuclear power plants located in the People’s Republic of China.” What Valcor didn’t report is that there are a number of AP-1000 reactors that have been approved, including the Vogtle 3 & 4 reactors currently under construction in Georgia, and the V.C. Summer Units 2 & 3, currently being built in South Carolina.
You can view Event Notification Reports by going to the Nuclear Regulatory Commission home page. Click on Read more under the Event Reports banner on the right side of the page. This will take you to the Reports Associated with Events page. On that page, click on Current next to Event Notification Report for the latest set of incidents.