The first two main coolant pumps for the Sanmen AP1000 plant are on their way back to China after repair work and re-testing, China's State Nuclear Power Technology Corp (SNPTC) has announced.
|Each AP1000 requires four main pumps
Each AP1000 employs four main reactor coolant pumps, which circulate reactor coolant through the core, loop piping and steam generators. The pumps were manufactured by Curtiss-Wright and initially passed qualification testing in June 2012 at Curtiss-Wright Flow Control business segment's Electro-Mechanical Division (CW-EMD) facility in Cheswick, Pennsylvania. However, final testing of a similar pump in January 2013 revealed potential quality problems.
As a result of the problems, SNPTC decided to ship three of the four main pumps it had already received from CW-EMD back to the USA for replacement of components including the impeller and guide vanes and factory re-testing. That work has now been completed on the first two main pumps. SNPTC expects the re-shipped components to reach Shanghai in early October.
Westinghouse is currently constructing four AP1000 units in China, two each at Sanmen in Zhejiang province and Haiyang in Shandong. Curtiss-Wright was awarded a contract by Westinghouse to produce 16 reactor coolant pumps for the units in 2007. Sanmen unit 1 is currently expected to begin generating electricity in 2014; it is not clear what effect - if any - the coolant pump issue will have on the construction schedule.
Curtiss-Wright Flow Control filed an event notification with the US Nuclear Regulatory Commission in May 2013, detailing the issues revealed during final testing of the defective pump. According to that filing, a piece of impeller blade was discovered to have separated from the main impeller casting. The physical cause of the failure, the report concluded, was most likely to be a flaw present in both the cast material and weld overlay applied to the impeller blade, and could not be remediated by subsequent weld repairs. CW-EMD expressed concern at a lack of process control in the sand casting process at Wollaston Alloys, the sub-contractor which had manufactured the defective part.
Researched and written
by World Nuclear News