The Nuclear Regulatory Commission will push for more data on the effects of a recent earthquake at Virginia’s North Anna nuclear plant before it will be allowed to come back online.On Friday, an NRC release summarized a confirmatory action letter that placed the onus on Dominion Virginia Power to prove “to the commission that no functional damage occurred to those features necessary for continued operation without undue risk to the health and safety of the public.”The epicenter of a 5.8 magnitude earthquake August 23 was 12 miles from the plant, causing both reactors to shut down automatically. Dominion has reported no significant damage during ongoing inspections. But ground motion recorded at parts of the plant exceeded design limits, the NRC said, prompting additional scrutiny from federal regulators.The NRC release did not outline the steps it has asked Dominion to take, but the agency also published correspondence Friday requesting additional information from the plant. Among the details sought regarding the plant’s steam generators, the letter asked for further information on an "ongoing investigation into the source/origin of the loose parts found in the SG A hot leg channel head. Could the loose parts have broken off from a reactor coolant system (RCS) component (as opposed to having been introduced as a foreign object during a maintenance/inspection activity)?”Multiple questions also addressed the structural integrity of piping, including a leak found on a control rod drive mechanism canopy seal weld on the unit 2 reactor vessel head that might or might not have been present before the earthquake.
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