Monticello taken off line due to tritium leak

March 27, 2023, 12:01PMNuclear News

A recurring leak of water containing tritium has led to the temporary shutdown of Xcel Energy's Monticello nuclear power plant, in Minnesota.

“While the leak continues to pose no risk to the public or the environment, we determined the best course of action is to power down the plant and perform the permanent repairs immediately,” said Chris Clark, president of Xcel Energy–Minnesota, North Dakota, and South Dakota, in a March 23 news release. “We are continuing to work with and inform our state, federal, city, and county leaders in the process.”

Powering down the reactor to shutdown condition started last Friday.

A failed fix: After reporting an initial leak of 400,000 gallons of water to state officials and the Nuclear Regulatory Commission in November of last year and identifying the source in mid-December, Xcel implemented a “short-term solution to capture water from the leaking pipe and reroute it back into the plant for reuse,” the release stated. It added that the company hoped the temporary fix would keep any additional tritium from reaching the groundwater until a replacement pipe could be installed during Monticello’s scheduled refueling outage in mid-April.

As it turned out, the “short-term solution” was shorter than expected. On March 22, monitoring equipment at the plant indicated a small amount of new water had made its way to the groundwater. According to Xcel, upon investigation, operators discovered the that temporary repair was no longer capturing all of the leaking water. The new leak, estimated to be in the hundreds of gallons, will not materially increase the amount of tritium the company is working to recover, Xcel said.

State scrutiny: In its own March 23 news release, the Minnesota Pollution Control Agency said that it is “encouraged that Xcel Energy is taking immediate action” to deal with the leak and that “state agencies have no evidence at this point to indicate a current or imminent risk to the public and will continue to monitor groundwater samples. Should an imminent risk arise, we will inform the public promptly.”

In addition, the agency recommended that the NRC “share ongoing public communications on the leak and on mitigation efforts to help residents best understand the situation.”

A low-level beta emitter, tritium is a common byproduct of nuclear reactor operation.

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