After Xcel Energy revealed a winter 2022 spill that saw more than 400,000 gallons of tritium contaminated water leak onto the grounds of the Monticello Nuclear Plant, state agencies and local media were informed of an additional leak discovered this week, seeing another several hundred gallons of radioactive water spilled onto the site. As a result, Xcel Energy announced Friday, March 24 that it will take steps to take the plant “offline,” shutting it down nearly a month prior to a schedule outage, in order to completely fix the leak.
The November 2022 spill was confirmed by the Nuclear Regulatory Commission and Minnesota Department of Health – in cooperation with Xcel – just last week. The March 16 statement said the company and regulators both agreed no water was spilled into the drinking water supply – which for millions of Twin Cities residents is the Mississippi River – despite the plant’s proximity to the waterway.
The nuclear plant uses water to power the plant’s generating turbines, but that water is burned off as steam as uranium rods are heated, with some cycling back into the plant’s tanks. The tainted water has been diverted to an in-plant treatment system until a permanent solution is installed sometime this spring.
According to Xcel, the process since November includes working with the NRC, the MDH and Xcel’s own regulatory staff and managers to fix the pipe and contain the spill.
According to the company:
“We are now monitoring, pumping, storing, processing and reusing the leaked water, which contains levels of tritium that are below the Nuclear Regulatory Commission (NRC) safety thresholds. Tritium is a compound that is naturally present in the environment and is commonly created in the operation of nuclear power plants. It emits low levels of radiation, as do everyday materials people use and the food we all eat. The water is fully contained on-site and has not been detected in any drinking water.
We live and work in this community and understand the importance of quickly informing the communities we serve if a situation poses an immediate threat to health and safety. In this case, there was no such threat. We promptly reported the issue to the state of Minnesota and the NRC, which was made available to the public. Every step of the way, we have worked with our regulators to manage the issue and ensure the safety of the local community and surrounding environment.
Quick Facts (as of March 22, 2023):
- Estimated tritium released: 8 curies
- Tritium recovered: 2.5 curies (over 30%)
- Highest off-site tritium measurement: Not detected
When was this leak identified?
The leak was discovered in November 2022, and Xcel Energy notified regulatory agencies the same day it was confirmed. The company continues to work closely with these agencies. We identified and isolated the source in December 2022, and we have been monitoring the tritium levels in the water since the leak was discovered.
MPR News created this sketch of the operational system at the Monticello plant.
What is the current status and what steps is Xcel Energy taking to fix the situation?
We acted quickly to isolate the leak and safely pump, store and process the impacted groundwater. These actions have succeeded in containing the impacts on-site at the facility. The company has partnered with local groundwater specialists, drilled over a dozen new monitoring and recovery wells and increased the frequency of measurements to help enhance our underground monitoring and recovery of affected groundwater. Groundwater and river water in the area are monitored and tested routinely, either daily, twice weekly, or weekly, depending on the location of the monitoring well.
We are pumping and storing tritium impacted groundwater so that it can be processed and reused on-site. We expect pumping activities to continue throughout the year. As of March 2023, we have recovered about 30% of the tritium from the groundwater and will continue recovery over the course of the next year. The highest concentrations of tritium are directly under the plant at the point of the leak. The highest measurement at that point was about 5 million picocuries per liter; as of March 22, this was down to 2.5 million picocuries per liter. The monitoring well closest to where we are conducting most of our pumping has read as high as 1.6 million picocuries per liter and, as of March 22, was down to 16,000 picocuries per liter.
What are the risks?
The leak poses no health and safety risk to the local community or the environment. Tritium occurs naturally in the environment in very low concentrations. It emits a low level of radiation, as do everyday materials people use and the food we all eat. Ongoing monitoring confirms that the leaked water is fully contained on-site and has not been detected beyond the facility or in any local drinking water. The radiation levels in the leaked water are so low that, even if it were to enter a drinking water source, a person could drink it and it would be as safe as the food they eat on an average day. For reference, learn how the risk compares to other everyday activities opens a file in a new window.
What was the source of the leak?
Xcel Energy identified the source of the leak as a water pipe running between two buildings. To contain the leak, the facility was diverting the water to an in-plant water treatment system, preventing additional water from leaving the plant. The plant is now in the process of making permanent repairs to the pipe. A thorough inspection was conducted of all piping in all locations where a leak could occur to verify that no other area of the facility was facing this issue. The company will also be examining the one pipe that did leak in a laboratory to better understand why this happened. These findings will help Xcel Energy ensure it does not encounter the same issue in the future.”
MPCA/MDH Release Joint Statement
The Minnesota Pollution Control Agency and MDH issued a statement Friday, March 24, regarding the shutdown:
The Minnesota Pollution Control Agency and Minnesota Department of Health are encouraged that Xcel Energy is taking immediate action to address the recurring issue of water containing tritium leaking from the Monticello Nuclear Generating Plant.
State agencies were made aware this afternoon of an additional water leak at the Monticello facility following previous news about the leak of 400,000 gallons of water containing tritium. In the State Duty Office report filed today, Xcel Energy states that the new leak, located near the spot of the previously reported release, is still ongoing.
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.
We encourage the U.S. Nuclear Regulatory Commission (NRC), which has regulatory oversight of the plant’s operations, to share ongoing public communications on the leak and on mitigation efforts to help residents best understand the situation.
The Minnesota Pollution Control Agency and the Minnesota Department of Health will continue to review Xcel’s response to the groundwater contamination and oversee the recovery, storage, and disposal of the impacted groundwater. We will also continue to coordinate with city, county, and other local officials to make sure the public is kept informed of developments.