The U.S. Nuclear Regulatory Commission (NRC) said that the operators of the 913 MWe Davis-Besse nuclear power plant, FirstEnergy Nuclear Operating Corp. (FENOC), have provided “reasonable assurance” that the shield building is capable of performing its safety functions and that the utility can proceed with restarting the plant.
On Oct. 10, the NRC was informed by FENOC that while conducting work to replace the reactor vessel head, workers identified cracks in the shield building. The shield building is a 2.5 foot thick reinforced concrete building that surrounds a 1.5 inch thick steel containment vessel that encloses the reactor. The two buildings are separated by a 4.5 foot space.
The NRC said it’s independent assessment evaluated a range of information such as technical details ranging from the size of the cracks, the utility’s sampling and testing of the concrete in the building to determine the extent of the cracks, and its structural analysis.
The NRC, though, has issued a Confirmatory Action Letter (CAL) to FENOC. The CAL details and confirms FENOC’s agreement to take certain actions to monitor and ensure the cracks in the shield building continue to not adversely impact safety going forward. The NRC will review and evaluate FENOC’s actions in response to the CAL in order to make sure they are thorough and complete.
The FENOC commitments to the NRC include:
- Determine and provide the root cause of the cracks in the shield building, corrective
actions, and develop a long-term monitoring program;
- Select multiple areas in the shield building that have no cracks but are adjacent to
known cracks to determine whether the area of the cracks has spread;
- Perform additional analysis in known cracked areas to determine whether the width of
the cracks has increased.
The NRC said it will continue to inspect whether the shield building in its current condition meets all design requirements in the plant’s license. Failure to meet the commitments in the CAL may result in additional regulatory action if the utility does not provide reasonable assurance that the NRC can rely on the FENOC to meet the NRC’s requirements and protect public health and safety.
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