NRC says 11 nuclear plants need to provide information on effects of irradiation on nuclear fuel

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The Nuclear Regulatory Commission has requested information from 11 nuclear power plants, mainly concerning analyses of the effects of irradiation on nuclear fuel’s physical properties under certain postulated accident conditions.

The agency is requesting the licensees evaluate a phenomenon known as “thermal conductivity degradation” – the fact that older fuel has a reduced capacity to transfer heat, potentially changing its performance during various accident scenarios, including loss-of-coolant accidents. The NRC is concerned that this phenomenon may not have been accounted for in realistic performance models for nuclear fuel developed by Westinghouse Electric Co.

“The NRC alerted the industry to this problem in 2009, and Westinghouse needs to do more to account for thermal conductivity degradation in its fuel performance codes,” said Eric Leeds, director of the NRC’s Office of Nuclear Reactor Regulation. “We need information from a few nuclear power plant licensees to maintain assurance that they can continue to operate safely with sufficient margin.”

In December, Westinghouse notified the NRC that an analysis it had conducted for a power plant indicated that thermal conductivity degradation could cause peak cladding
temperature to increase by more than 100 degrees F during a worst-case loss-of-coolant accident at a Westinghouse pressurized water reactor.

The 11 plants named in the RFI are those Westinghouse clients with currently reported peak cladding temperatures above 2,000 degrees F. Accounting for thermal conductivity degradation in their analyses could result in peak temperatures approaching or exceeding the 2,200 degree limit. These plants are Beaver Valley 1 and 2, Braidwood 2, Byron 2, Catawba 1 and 2, Donald C. Cook 1 and 2, Kewaunee, and McGuire 1 and 2. An additional 23 plants that use the Westinghouse performance models also received informational copies of the RFI, to ensure that they are aware of their obligations to address this error.

The plants have until March 19thto provide the requested information to the NRC staff. If the information received does not demonstrate that NRC regulations are met, the staff will recommend imposing restrictions on reactor operating limits until acceptable action has been taken.

Source: NRC


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