The U.S. Nuclear Regulatory Commission (NRC) rated as yellow, or of substantial safety significance, two flood protection violations at a nuclear power plant owned by Entergy (NYSE: ETR).
The flooding issue came up following a fatal incident that occurred at Arkansas Nuclear One in March 2013. Workers were moving a 525-ton component from the plant’s turbine building during a maintenance outage when the lifting rig collapsed, dropping the component and damaging a fire main in the Unit 1 turbine building. Fire pumps began pumping water into the building, and some of the water leaked past degraded floor seals and flowed down onto the lowest level of the Unit 1 auxiliary building, covering the floor in two inches of water. Water also entered one of the safety-related pump rooms because a valve in an adjacent hallway was not fully closed.
After the event, Entergy and the NRC began a comprehensive inspection of flood barriers, and numerous deficiencies were identified and subsequently documented in a Sept. 9 NRC report. In the unlikely event of extreme flooding at the site, the NRC determined that significant amounts of water could potentially have entered auxiliary buildings and vaults where fuel for the emergency diesel generators is stored, due to the degraded condition of numerous flood barriers.
Entergy has resolved all of the issues by replacing all of the degraded seals or parts, installing new penetration seals, implementing compensatory measures, or adding appropriate instructions to procedures to ensure the protection of vital safety-related equipment.
Subscribe to Nuclear Power International magazine