Millstone only U.S. plant inspecting possibly compromised component
Waterford — Millstone Power Station will voluntarily allow an inspection of a critical component in the Unit 2 cooling system by an independent contractor next week, making the plant the only one to do so among the nation’s 17 nuclear reactors with parts made by a French company under scrutiny for manufacturing flaws and document falsification.
Beyond Nuclear, a Maryland-based watchdog group, is calling on the Nuclear Regulatory Commission to require inspections like the one planned at Millstone at all U.S. plants that contain parts made at the Le Creusot Forge in France.
Paul Gunter, director of the Reactor Oversight Project at Beyond Nuclear, also said Monday that he believes the Millstone part in question, a pressurizer, should undergo more extensive testing than is currently planned. An ultrasound test of the component is planned, but not a test of the carbon content of the steel used in the part. Excess carbon has been cited as one of the main flaws found in parts in French reactors.
“We’re concerned that ultrasound testing may not be complete,” Gunter said.
Ken Holt, spokesman for Millstone, said plant owner Dominion Resources decided to inspect the pressurizer at Unit 2 after discussions with the state Department of Energy and Environmental Protection’s Radiation Division about revelations late last year that parts made by AREVA’s Le Creusot Forge and used in French reactors are defective.
The company is under investigation by French nuclear regulators for making substandard parts and falsifying documents, according to a March 16 article by Reuters. Two plants in France are shut down as a result of the investigation thus far, and 12 other plants were shut down temporarily but have since restarted.
The ultrasonic testing on the pressurizer will be done while Unit 2 is shut down for refueling, Holt said. The plant has been shut down since Saturday.
Jeff Semancik, director of the DEEP Radiation Division, said representatives of his office hope to observe the testing and will review the images, data and reports afterwards.
“They’ve hired an independent third party to review everything,” he said. “We’re happy that Dominion is doing this even though they’re not required to. They’re taking prudent action.”
Semancik said he has reviewed the plan for the testing and agreed that the scope and methods will be able to determine whether there are flaws or cracks in the pressurizer that could cause it to fail. The pressurizer is essential for maintaining constant pressure in the reactor coolant system.
Neil Sheehan, spokesman for the NRC, said the agency is aware of the inspection plans at Millstone and will review the results and follow up on any findings. An NRC specialist inspector will be on the site during the outage, in addition to resident inspectors.
“We do not have any current safety concerns with the Millstone Unit 2 pressurizer,” Sheehan said.
The NRC, he said, has conducted “preliminary structural evaluations” of reactor components made at the Le Creusot forge and has participated in multinational inspections of the forge, among other steps, he said.
“The components supplied to U.S. plants have performed well and inspections during their operating life have revealed no safety issues,” he said.
The pressurizer at Unit 2 has been in service since 2006. After an earlier review of documents about parts from the forge, AREVA notified the NRC that the pressurizer’s shells receive three heat treatments instead of the two required by design specifications. The heat treatments are designed to relieve stress. The NRC concluded that the additional heat treatment did not affect the integrity of the pressurizer and that it still met the design code.
During a presentation last month about Millstone and the issues with Le Creusot Forge, an NRC official said the excess carbon problem occurred in very large components such as reactor vessel heads, but was not found in smaller parts such as the pressurizer. The excess carbon diminished the “fracture toughness” of the large parts, said David Rudland, branch chief of the vessels and internals integration branch of the NRC.
Another NRC official, Kerri Kavanaugh, branch chief of the quality assurance vendor inspection branch of the agency, said there had been “a significant deficiency in the safety culture” at Le Creusot Forge.
Gunter said he believes that all Le Creusot parts at U.S. plants should undergo the carbon content tests using scrapings of metal from “surplus” areas.
“The carbon content is critical to telling you how embrittled they are,” he said.
If excess carbon or cracks are found in the pressurizer and other parts, Gunter said, “it would certainly raise questions about whether the plant can continue to operate.” The pressurizer, he said, is considered a “critical component” needed for the reactor to operate safely.
Holt said the results of the ultrasound tests will be compared against similar tests done when the pressurizer was first forged.
“We’re confident the pressurizer is fully operational and will continue to be through the life of the plant,” he said. “We are proactively doing this test to provide additional assurance.”
He said the testing can be completed in less than a day, and that a written report will be generated that will be shared with DEEP and the NRC.
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