NRC launches special inspection at Davis-Besse

The six-person inspection team will review the response from Energy Harbor to the diesel generator failures, the NRC said, including the company’s cause analysis, extent of condition reviews, maintenance practices, and system design. The inspectors will also look into the circumstances surrounding the reactor trip (triggered by a trip of the main turbine), assessing equipment performance and operator response.

Davis-Besse, a single-unit facility located in Oak Harbor, Ohio, has two emergency diesel generators, which would provide emergency power during the loss of off-site power, and one station blackout diesel generator, which would provide power in the event that both emergency diesel generators failed.

Zooming in: According to the NRC, in the past 24 months Davis-Besse experienced four failures of emergency diesel generators to operate in accordance with specifications during testing, as well as one failure of the plant’s blackout diesel generator during maintenance.

Further, “While the agency was planning the special inspection on diesel failures, the reactor experienced an unplanned trip,” the NRC said in its announcement. “During the plant’s response to the trip, certain pieces of equipment did not function as designed. Operators took action to address the equipment issues, and the reactor was shut down safely and placed in a stable condition. After making the necessary repairs, the reactor returned to power. Based on the complications of the trip, the agency chose to expand the special inspection to better understand equipment performance issues and operator response.”