The Nuclear Regulatory Commission took steps this week to ensure that easily clogged sumps aren't a problem at nuclear plants around the nation.
The commission sent a bulletin to 68 operational plants asking them to report on the condition of their sumps, which collect water used to cool nuclear reactors during emergencies.
Nuclear plant officials have 60 days to report that their sumps meet regulations making clogs unlikely or describe plans to reduce the chance of clogs.
“We don't know at the moment how much of an issue this could be at the various plants,” Scott Burnell, an NRC spokesman, said.
Mr. Burnell said information from the Davis-Besse plant near Oak Harbor, Ohio, brought more attention to the possibility of sumps being blocked by debris.
Last year, an investigation of Davis-Besse revealed a small gap in the screen covering the plant's sump.
The gap could allow debris to enter the sump circulatory system and block it, preventing water flow.
The plant must have an adequate supply of water to cool the reactor in certain emergencies.
Mr. Burnell said the nationwide bulletin was necessary “just to make sure the Davis-Besse information was not indicative of a possible widespread issue.”
The NRC has studied the likelihood of clogged sumps since the mid-1990s, but Mr. Burnell said the nation's nuclear oversight agency has little information about what measures specific plants take to avoid the problem.
Richard Wilkins, a spokesman for FirstEnergy, which operates Davis-Besse, said nuclear plants with designs similar to Davis-Besse have discussed the possibility of sump blockages for the last decade.
“Everybody has been grappling with it,” he said. “Is it an issue, or isn't it? And if it is, how do you deal with it?”
During its recent overhaul, Davis-Besse replaced the screen covering its sump with an eye toward making the system extra safe.
The new screen is 1,200 square feet, 24 times the size of the former 50-square-foot screen.
“We wanted to go to the NRC and say that for Davis-Besse, the sump issue is at rest,” Mr. Wilkins said.
For nuclear plants that have not addressed the issue, the NRC has several recommendations, including more aggressively cleaning the area around the sump, frequently checking that sump screens and drainage areas are not blocked, training operators on responses to sump clogging, and ensuring that alternate water sources are available to cool the reactor if the sump is blocked.
Mr. Burnell said if plants ignore the problem, the NRC could demand that certain plants upgrade their equipment and take other measures to reduce the chance of sump clogs.
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