Monticello Nuclear Generating Plant accident

The Monticello Nuclear Generating Plant accident was a radiation accident that occurred in November 2022 at the Monticello Nuclear Generating Plant in Monticello, Minnesota, U.S., during which over 1,500 cubic meters of radioactive water leaked.^[1]

Background

The Monticello Nuclear Generating Plant is a nuclear power plant with a single boiling water reactor (BWR) with a nominal capacity of 671 MW, built and commissioned in 1971. The power plant is located in Wright County, Minnesota, United States, on the banks of the Mississippi River. At the time of the accident, the plant had been in operation for over 50 years,^[2] and its license expires in 2030.^[3] In 2023, Xcel Energy planned to extend the plant's life by another 20 years.^[4][5] The plant has previously experienced radioactive water leaks. In May 1982, 4.9 cubic meters of water leaked into the nearby Mississippi River. Regulators deemed the leak as "minor."^[6]

Accident

According to a March 16, 2023, statement from plant operator Xcel Energy, a leak of radioactive tritium-contaminated water was detected on November 21, 2022, from a pipeline that pumps water between buildings at the power plant. The leak, the operator said, contained more than 400,000 gallons (more than 1,500 cubic meters of radioactive water).^[1] The Nuclear Regulatory Commission was notified the following day, but the circumstances of the accident were not made public until March 2023, four months after the accident.^[7][1][8][9]

Since the leak, only 20% of the radioactive material that leaked through the drilled wells had been removed and decontaminated at the time of the accident’s public disclosure.^[10] As of March 17, 2023, cleanup efforts are still ongoing. The company explained that it kept the accident quiet for four months by assessing the environmental impact of the accident. Since, according to a Xcel Energy representative, the threat was minimal, the company did not consider it necessary to immediately make the incident public.^[10]

According to officials, radioactive water did not leave the borders of the enterprise, did not penetrate the Mississippi River basin and did not get into the sources of drinking water.^[10] The company explained the silence of the accident for a period of four months by an assessment of the impact of the consequences of the accident on the environment. Since, according to the representative of Xcel Energy, the threat was minimal, the company considered it unnecessary to immediately publish the incident.^[8]

On March 24, another leak of "several hundred gallons" of tritium-contaminated water was discovered reaching the groundwater. The utility said there was no environmental threat but shut down the plant to fix the leaks.^[9]