UPDATE 3-Quake-hit US plant sees restart without retrofits
* Virginia plant near epicenter shut down after quake * No required modifications expected to prevent restart * But eventual changes expected in broader review-expert * Cosmetic damage found in containment structure at plant By Ayesha Rascoe and Roberta Rampton MINERAL, Va., Sept 2 (Reuters) - After a week of detailed inspections, Dominion Resources Inc has not yet found any severe damage that would prevent its quake-hit North Anna plant from restarting, a senior official said on Friday. Dominion does not expect to have to do any major retrofits before resuming operations at its plant, only miles from the epicenter of last week's record earthquake in the Eastern United States, said Dan Stoddard, the company's senior vice president for nuclear operations. The force of the brief earthquake may have gone beyond the design specifications for the two reactors -- the first time that has happened for an operating U.S. nuclear power plant. Despite the lack of damage, the Virginia quake comes at a sensitive juncture for the U.S. nuclear sector. A nuclear disaster in Japan that followed an earthquake and tsunami in March prompted a major regulatory review in the United States. Operators such as Dominion, Exelon , Entergy and PG&E have been assessing costs of fixes to aging plants. This week, the Nuclear Regulatory Commission announced it wants the country's 104 reactors to model earthquake risks using updated data, the latest step in a decades-long process that hasn't uncovered any "imminent" dangers but could eventually result in expensive "backfits" for plants. "I think what the East Coast earthquake demonstrated is the design parameters might be changing," said Dale Klein, a mechanical engineer at the University of Texas, and a former chairman at the NRC. "This is probably going to be plant-by-plant, and they'll probably say, 'These are the requirements you now have to meet,'" Klein said in an interview.VIRGINIA PLANT EXPECTS RESTART Reporters stepped over cracked floor tiles in the North Anna plant's administrative building during a tour of the plant on Friday, an example of the minor damage seen from the quake that Dominion official Stoddard said speaks to the extra engineering "safety margins" built into the plant. The most severe damage was to seals at the base of high-voltage "porcelain bushings" that connect the plant's transformer to the power grid, and Dominion has already begun replacing the damaged equipment. Preliminary reviews indicated that while the ground may have shaken more than the plant was designed to handle at points during the earthquake, the strongest ground motions only lasted a few seconds. "One acceleration for very short time over design (specifications) does nothing to plant and that's consistent with what we've seen," Stoddard said. "That tells me that earthquake was non-damaging ... and that we have significant margin over and above the design of the plant," he added. While the company stressed that the quake had done little harm to the plant, officials declined to provide any specific measurements of ground acceleration at the plant during the historic tremor, saying the company's analysis is not yet complete. Workers at the plant did find at small crack in an interior wall within a containment structure at the plant. Officials described it as "cosmetic" damage, however. The company will complete its analysis of the quake's impact next week, but does not yet have a timeline for when it will resume producing power -- something that will require sign-off from the regulator. The Nuclear Regulatory Commission is also inspecting the plant and its review is expected to take a few weeks. NRC Chairman Gregory Jaczko told Reuters on Thursday that the regulator has not yet seen any sign of equipment damaged in the quake, but he said it was too soon to say what changes the regulator might require. There's nothing so far to suggest that the regulator would move to permanently shut down the plant, said Nathan Ives, an industry consultant with Ernst & Young. "I'd expect North Anna to be fully inspected and rigorously inspected, but then to be back online, operating at capacity," said Ives, who formerly worked with the Institute of Nuclear Power Operation, the industry's self-regulatory body.
© Thomson Reuters 2017 All rights reserved