Xcel fined $14K over unpermitted storage of radioactive water at Minnesota nuclear plant

Xcel Energy has been fined $14,000 for storing radioactive water without a permit in the aftermath of a spill last year at its Monticello Nuclear Generating Plant.

Meanwhile, Xcel revealed Thursday that the original spill started a few weeks earlier than the company originally reported, and may have released more than twice as much radioactive water as it originally estimated.

The plant, about a 30-minute drive northwest of the Twin Cities, sprung a leak of tritium-tainted water in late 2022. The utility and the Minnesota Pollution Control Agency (MPCA) didn't reveal the leak to the public until the following March, drawing public criticism and a promise from state officials to be more transparent.

Xcel originally reported that some 400,000 gallons of water had seeped from a broken pipe in a narrow space between two buildings. But on Thursday, it reported that the real amount was more likely between 750,000 and 900,000 gallons — an updated guess based on research the company has done and "signs that the leak may have started a few weeks earlier than previously estimated."

The utility said that its strategy to remediate the site remains the same: pumping tainted water out of the ground, and storing it permanently. So far, 7 million gallons have been pumped up for storage.

According to an MPCA press release on Thursday, the agency fined Xcel for its use of temporary aboveground storage tanks to hold the tritiated water. Xcel broke state regulations by holding more than a million gallons of the water in the tanks without first seeking a permit.

In addition to paying the fine, "Xcel Energy was required to immediately obtain the permit before continuing its response and cleanup. The MPCA issued the appropriate permit in May 2023, requiring the use of temporary tanks to end by Nov. 1," the release said.

Stephen Mikkelson, a spokesman for MPCA, said the agency's investigation started after Xcel got the needed permit in May, and closed last month. He wrote in an email that the agency "communicates about enforcement actions after the entire enforcement process has concluded," and the entity it is investigating has paid a fine, made improvements, or done both.

Kevin Coss, a spokesman for Xcel, wrote in an email that the utility had "temporarily" held more water in the tanks than it was allowed to. "We will remain in close coordination with regulators as we continue to retrieve, store and reuse the leaked water," he wrote.

Tritium is a mildly radioactive isotope of hydrogen that it a common byproduct at nuclear plants. It can only harm people if ingested in significant amounts.

The Monticello plant is located on the banks of the Mississippi River, upstream of the point where the city of Minneapolis collects its source of drinking water. State health officials said that even if the tritiated water did reach the river, it would be so diluted that it would not pose a threat downstream.

Dealing with the leak presented a months-long challenge as Xcel pumped up the tritiated groundwater and tried multiple strategies to stop the plume from reaching the river. Its temporary patch on the original leaky pipe failed at one point, and prompted the plant to shut down, so it could install a more permanent fix.

Xcel also said in July that some of the tritiated water that remained underground had possibly reached the Mississippi, as it showed up in a monitoring well next to the river. But the tritium was detected in levels far below the Environmental Protection Agency's health limit for the isotope in drinking water.

The agency said in its most recent statement that tritium has not been detected in the river to date.

MPCA and Xcel both said the company no longer holding the tritiated water in temporary tanks, and has built a more permanent lined ponds for storage.