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An Aging Nuclear Plant in Minnesota Is Leaking Radiation: Should You Be Concerned?

Hundreds of thousands of gallons of radioactive tritium-tainted water were released not far from the Mississippi River.

Eric Mack Contributing Editor
Eric Mack has been a CNET contributor since 2011. Eric and his family live 100% energy and water independent on his off-grid compound in the New Mexico desert. Eric uses his passion for writing about energy, renewables, science and climate to bring educational content to life on topics around the solar panel and deregulated energy industries. Eric helps consumers by demystifying solar, battery, renewable energy, energy choice concepts, and also reviews solar installers. Previously, Eric covered space, science, climate change and all things futuristic. His encrypted email for tips is ericcmack@protonmail.com.
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Eric Mack
7 min read
The Monticello nuclear power plant in Minnesota.

The Monticello nuclear power plant in Minnesota.


A nuclear power plant on the banks of the Mississippi River in Minnesota is temporarily powering down to fix a leaking pipe that's been releasing contaminated water. 

The leak of tritium-tainted water from the facility run by Xcel Energy in Monticello, Minnesota, was discovered in November after it had released about 400,000 gallons. The company says it put a temporary fix in place to catch the leaking water and route it back into the plant until permanent repairs could be done during a planned refueling shutdown in April. But late Thursday it announced that the fix was no longer capturing 100% of the tainted water.

"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," Chris Clark, president of Xcel Energy–Minnesota, North Dakota and South Dakota, said in a release.

Regulators are keeping tabs on the leak and the potential dangers.

"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," the Minnesota Pollution Control Agency said in a separate statement. "Should an imminent risk arise, we will inform the public promptly."

Though Xcel found the source of the leak in November and immediately reported it to state and federal regulators, it was announced to the general public only last week. The incident is raising questions about what should be communicated to the public, and how soon, when it comes to the release of dangerous materials from aging nuclear plants. 

Worries about nuclear plants have been a constant for decades, sparked by major accidents at Three Mile Island in Pennsylvania in the 1970s and Chernobyl in Ukraine in the 1980s. Tighter regulations led to a drastic slowdown in the expansion of nuclear power in the US, with only one new reactor coming online in the past 25 years. The Nuclear Regulatory Commission oversees 95 operating nuclear power reactors in the US, with two new units in Georgia currently under construction. 

The climate crisis has put a new spotlight on nuclear power as an alternative to the burning of fossil fuels, which generates huge volumes of greenhouse gases. But critics say that safety concerns continue to outweigh the benefits, pointing to more recent accidents, like the 2011 release of radiation from the Fukushima nuclear power plant in Japan. 

The source of the leak at the Minnesota plant is a pipe running over a narrow gap between two buildings at the facility. The company says it's recovered almost a third of the radioactive material, but levels of tritium on the site remain well above the Environmental Protection Agency's threshold for safe drinking water. Tritium is a radioactive form of hydrogen and a byproduct of nuclear power generation. Xcel says the contaminated water has been fully contained on site and poses no risk to local communities or the environment. 

"Currently, there is no health risk due to this situation," the Minnesota Department of Health's website says about the leak, adding that the department doesn't expect the leak to lead to levels of tritium above the EPA limit anywhere beyond the nuclear plant itself. 

According to the Nuclear Regulatory Commission, there have been at least six leaks at US commercial nuclear power plants in the past 20 years that released even higher concentrations of tritium into on-site groundwater.  

"Tritium rapidly disperses and dissipates in the environment, and as a result, tritium from leaks and spills is typically not detected outside the facility boundary," says an NRC report from 2020

Xcel hasn't yet determined when the plant will be able to resume regular operations. The utility says it doesn't anticipate that the repairs will affect services for its energy customers. 

A delayed notification

Elevated levels of tritium in groundwater at the plant were detected by monitoring wells in September. Xcel says it discovered the source of the leak in November and reported it to state and federal agencies the same day, Nov. 22. Yet few others seemed to notice or care for the next several months. 

Edwin Lyman was among those who noticed right away. 

"The Nuclear Regulatory Commission (NRC) posted the news on its daily event reports page at the time. I even tweeted about it," Lyman, director of nuclear power safety for the Union of Concerned Scientists, told me. "But neither the NRC nor state agencies are required to further publicize these types of incidents through more widely accessible channels."

NRC spokesperson Viktoria Mitlyng told CNET that whenever tritium leaks occur at nuclear plants, NRC inspectors work to determine the potential impact on public health. 

"If the NRC determines that a leak could negatively impact the plant, people or the environment, we would immediately inform the public," Mitlyng said. 

Aside from the leak report being posted on the NRC page in November, it wasn't made public by Xcel or the Minnesota Pollution Control Agency until an MPCA press release went out last Thursday. 

"The situation at Xcel Energy's Monticello plant did not, and still does not, pose (a current or imminent) risk," the MPCA said in an emailed statement Tuesday. "We understand the public's interest in learning about such events as soon as possible and we must balance the need to inform the public of such events with the potential for causing undue fear by releasing incomplete information."

Before publicizing the leak last week, nearly four months after its source was discovered, the agency says it "strongly encouraged Xcel to be more transparent about the leak and its remediation actions."

The MPCA added that it chose to inform the public last week after gathering more details about the leak and cleanup and learning that the contamination within the facility was moving in the direction of the nearby Mississippi River.

Xcel also said it needed to gather more information before releasing information about the leak.

"We live and work in the Monticello community, too, and the safety of our hundreds of employees and the surrounding area is a top priority," Xcel spokesperson Kevin Coss said via email Tuesday, before the decision to power down the plant. "Now that we have thoroughly investigated the issue, contained the leak, and mapped out a path forward, we are at a place where we can share with the public not only what has already been done, but what we're going to do next. This timing allows us to provide the most accurate and complete understanding of the situation."

How concerned should you be about leaks from aging nuclear facilities?

It's important to reiterate that every source and everyone I contacted for this story emphasized that there's likely little reason for concern that the leak will impact the health or safety of the nearby environment. 

Though cleanup is expected to take months, the movement of the plume of contamination in the groundwater beneath the site is monitored through a system of two dozen wells and the contamination is still being pumped out. The wells are arranged in concentric circles so the movement of contaminants in the direction of the river can be tracked.

Tritium is typically the first radioactive material to be detected after a spill or leak at a nuclear plant, according to the NRC. As radioactive materials go, tritium is far from the scariest. It occurs naturally in the environment, and the ionizing radiation it emits in the form of beta particles is so weak that it typically won't penetrate human skin. If you were to drink large amounts of tritium-tainted, or triated, water, there's a chance it could slightly increase your odds of developing cancer at some point in your life, but it's difficult to connect a cancer diagnosis to a specific exposure.

Lyman, from the Union of Concerned Scientists, agrees that there's probably little to fear from this specific situation, but he says it points to a worrying trend. 

"Leaks of contaminated water are becoming more common as nuclear plants age and as piping that is hard to maintain or replace degrades," he explained. "These incidents should serve as warnings that greater regulatory oversight and better management of aging nuclear plant infrastructure may be needed."

D.J. LeClear, a nuclear safety specialist who goes by "The Rad Guy" on TikTok, told me that tritium leaks were on the rise until 2010 when there was a spike with five incidents in the same year.

"This gained the attention of the NRC and the industry as a whole and led to an industrywide change and focus on eliminating tritium spills," LeClear said. "Thankfully, the result was a dramatic decrease in spills across the industry. ... Spills peaked in 2010 and the recent spill was the first in seven years."

A chart showing tritium leaks in recent years

The recent tritium leak was the first in years. 

D.J. LeClear, NRC

Though LeClear thinks there's no need for new rules or regulations, he said on Twitter that he believes a more timely public announcement about the leak should've happened in the case of Monticello. 

"A response needs timeliness, context/education, and empathy," LeClear said. "Admitting mistakes, even when you followed the rules to the t, is also necessary. This gains trust which is key in these situations."  

While the situation in Minnesota may be contained and little reason for concern, it still points to the importance of keeping a close eye on a vital part of the energy sector. 

"Far more serious events occur at nuclear plants that the NRC does not notify the public about beyond posting an event report," Lyman said.

The NRC's Mitlyng says nonemergencies end up posted in the event reports on the NRC's website. 

If you're interested, you can check out those event reports on the NRC's website here. (Be advised, though: They don't exactly make for casual reading.) You can view new reports for each day, but if you don't want to make this part of your daily routine, you can instead download one large text file of reports from the last month, then do a search within the file for the names of nuclear reactors near you. Here's a map and full list of the reactors overseen by the NRC.

"Situations that could potentially impact the plant or the public are clearly communicated," Mitlyng said. "Our inspectors follow up and review a wide range of issues at a nuclear power plant every day."