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“The NRC has been dragging its feet for a long time on dealing with this,” says Lyman. “It has been locked in a kind of dance with the utility about how to interpret and react to that. It seems like the preferred view these days is to acknowledge there is a higher risk but say that it's still small, then use cost-benefit analysis to decide there is no need to spend on the upgrade.”Three years ago a 5.8 magnitude earthquake shook Mineral, Virginia, 11 miles from the North Anna Nuclear Station. It was a shock the plant was never built to withstand. Its operator, Dominion, claimed there was no functional damage (despite a small crack) and that spent fuel canisters had shifted no more than four inches during the tremor.A preliminary NRC review made public in 2011 concluded that North Anna's two reactors are among 27 in need of upgrades because they are at risk of being struck by an earthquake more powerful than they were designed to bear. Nonetheless, two months after the earthquake, the regulator, which approved North Anna's licence renewal in 2003, permitted the plant to go back online.“Some people look at [the North Anna earthquake] and say, 'The way we build these reactors leaves a lot of extra margin,'" says Lyman. "The problem is that because there hasn't been a full analysis to understand all of the potential impacts, you can't really just extrapolate. What the NRC has done since Fukushima is to ask all of the utilities to re-examine the size of the seismic and flooding risks and that process is ongoing. The problem is, no one really knows how to do that because, to plug into the formulas that the NRC uses to decide whether a reactor is risky enough to impose new regulations, you need a pretty good knowledge of what that risk is, and no one can predict with any certainty what the seismic risk of any site is. It's an exercise in futility."
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