Washington — China's Sanmen-2 nuclear reactor, the third US-designed Westinghouse AP1000 unit to begin operating in the world, has been shut temporarily because of a defect in a reactor coolant pump, which is being replaced, a top Chinese nuclear regulator said Thursday.
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A replacement reactor coolant pump has been shipped from the US and is expected to arrive at the Sanmen site in the next several weeks, Shirong Zhou of China's National Nuclear Safety Administration said during the US Nuclear Regulatory Commission's annual conference in Washington.
The unit is the third of four US-designed reactors to operate in China. Chinese companies gained ownership of the technology for the design for domestic use as part of a deal to acquire four units from Westinghouse.
The AP1000 design is a next-generation reactor model that is also being built at Georgia Power's Vogtle plant in the US.
Each AP1000 includes four of the sealed reactor coolant pumps, which have had design and quality problems before.
The AP1000 design at one time had been considered for widespread deployment in China, but delays in construction related to earlier issues with the US-built reactor coolant pumps have reportedly led Chinese decision-makers to favor a domestic reactor design for deployment in larger numbers.
The problem appears to be related to the motor for the giant pump, Zhou said. An initial investigation shows there was leakage around supports for the pump, but a full investigation will have to wait until the defective pump is disassembled and examined after removal, he said.
The reactor coolant pumps, which move coolant around the primary cooling circuit of the reactor, are the largest so-called "canned pumps" to ever be used in a nuclear reactor. The hermetically sealed pumps are designed to operate without leakage and contain a sealed motor system.
The pumps were manufactured by US-based Curtiss-Wright. During construction of the Sanmen and Haiyang units in China, several of the pumps were returned from China to the US for repairs after a defect was discovered that resulted in localized heating of the pumps.
Westinghouse and Curtiss-Wright are engaged in a dispute over responsibility for delivery delays for the pumps in China and the US, Curtiss-Wright has said in financial filings.
With the exception of the pump problem, the overall operating experience of the four AP1000 reactors in China has been good, Zhou said.
Two AP1000 units each at the Sanmen and Haiyang nuclear plants entered commercial operation between the middle of 2018 and January. China is the world's third-largest operator of nuclear units after the US and France. The country has 45 power reactors with a gross capacity of 45.8 GW operating, with an additional 11 units totaling 12.2 GW of capacity under construction, Zhou said.
Westinghouse spokeswoman Courtney Boone confirmed Thursday that the operator of the Sanmen plant had identified an issue with a reactor coolant pump and a replacement had been shipped to the site. "We are working with the customer as they investigate this," she said.
She referred further questions to operator China National Nuclear Power.
Construction on Sanmen-2 began in December 2009 and the unit entered commercial operation in November after a period of test operation.
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