A nuclear power plant released contaminated water in Minnesota. Here’s what we know: NPR

Minnesota officials are overseeing the cleanup of a 400,000 gallon leak of contaminated water from a Monticello nuclear power plant operated by energy giant Xcel Energy. Authorities said there was no danger from the leak.

The leak was discovered nearly four months ago and reported to state and federal regulators. The Federal Nuclear Regulatory Commission issued a public notice at the time, but the company and state agencies did not notify the general public until last week.

“Xcel Energy took swift action to contain the spill to the plant site, which did not pose a risk to the health and safety of the local community or the environment,” the company said in a statement Thursday. Ongoing monitoring has confirmed that the leak “is fully contained on-site and has not been detected off-site or in local drinking water,” the company said.

Xcel confirmed the leak of water containing tritium in November 2022 and notified employees the same day, according to the company’s release. Authorities attributed the leak to a water main running between two buildings on the plant site. The amount of contaminated water leaked is enough to fill about 60% of an Olympic-sized swimming pool.

Xcel is based in Minneapolis, Minnesota and operates in eight US states. Both nuclear power plants are based in Minnesota. Monticello is about 40 miles northwest of Minneapolis and has a population of about 15,000.

Because there was no immediate threat to public health and safety, “we focused on investigating the situation and containing the affected water in agreement with our regulatory agencies,” Xcel spokeswoman Lacey Nygaard said in an email to NPR when asked why there was almost four months late in notifying the public. “We are now in a place where we can share with the public not only what has already been done, but also what we are going to do next.” This timeline allows us to provide the most accurate and complete understanding of the situation.”

In 2009, the same Xcel plant in Monticello had a small leak of tritium, which Nygard said was smaller in scale than the 2022 leak and came from a shaft, not a pipe.

“Many operating nuclear plants have had some level of tritium leakage at some point during their operation,” Nygaard said.

Michael Rafferty, a spokesman for the Minnesota Pollution Control Agency, told NPR that the agency was waiting to get more information before making it public.

“Minnesota state agencies are deeply committed to our role in protecting human health and the environment and take seriously our responsibility to promptly inform the public when a situation presents any ongoing or imminent risk,” Rafferty said. “The situation at the Xcel Energy site in Monticello did not – and does not – pose an immediate threat to the health of residents.”

Officials with the Federal Nuclear Regulatory Commission did not immediately respond to requests for comment. NRC spokeswoman Victoria Mittling told a local news station that the public’s concern was “very understandable” and stressed that “the community in Minnesota, the people, the community near the plant were not and are not in danger. “

What is tritium?

Tritium is a naturally occurring form of hydrogen that emits a weak form of radiation that cannot travel far in the air or penetrate the skin, according to the NRC.

Tritium is also a byproduct of electricity production at nuclear power plants, and the dose of tritium that comes from nuclear power plants is much lower than radiation exposures in the natural environment, according to the NRC. Xcel said the tritium levels in the leaked water were below NRC safety thresholds.

“Everyone is exposed to small amounts of tritium every day because it occurs naturally in the environment and the foods we eat,” according to the NRC fact sheet.

Any exposure to radiation can pose some health risk, including an increased incidence of cancer. Exposure risks are linear, meaning that lower levels of radiation pose less risk.

Eating or drinking food or water with tritium is the most common way it enters the body. It can also be absorbed through the skin. About half of it leaves the body within 10 days of exposure.

The cleanup will take months

Xcel says it has recovered about 25 percent of the tritium-contaminated water that leaked, and recovery efforts will continue into the next year.

“While this spill does not pose a risk to the public or the environment, we are taking this very seriously and are working to address the situation safely,” said Chris Clark, president of Xcel Energy–Minnesota, North Dakota and South Dakota, in a company statement. “We continue to collect and treat any potentially affected water while regularly monitoring nearby groundwater sources.”

To limit leakage, water is diverted to a treatment system inside the plant that prevents water from leaving the plant. Xcel said it also checked all of its pipelines to make sure it wasn’t happening elsewhere in the facility.

The Minnesota Pollution Control Agency said Xcel is considering building above-ground storage tanks or installing a retention pond to store the tritium-containing water that is recovered, as well as considering treatment, reuse and disposal options. Minnesota regulators will review any options the company chooses, the MPCA said.

“Our top priority is protecting residents and the environment, and the MPCA is working closely with other state agencies to oversee Xcel Energy’s monitoring data and cleanup activities,” said Kirk Kudelka, MPCA Assistant Commissioner for Land and Strategic Initiatives . “We are working to ensure that this cleanup is completed as thoroughly as possible with minimal or no risk to drinking water supplies.”