Xcel Energy to build underground barrier to contain radioactive water leak at Monticello NPP22 August 2023
US power utility Xcel Energy announced that it will build an underground metal barrier at the Monticello NPP in Minnesota to contain a leak of water containing tritium and prevent it entering contaminated groundwater from entering the nearby Mississippi River. Xcel expects construction to last for several weeks.
Workers have been pumping and storing water from the ground at the plant since a faulty pipe caused a leak of about 400,000 gallons of water contaminated with tritium in November 2022. Xcel temporarily shut down the plant and repaired the leak in March. However, in May Xcel notified the Minnesota state duty officer that 300 to 600 gallons of pumped groundwater had overflowed a holding tank and returned to the ground. Overall, Xcel said it had made “substantial” progress in recovering the contaminated groundwater. In may it had pumped over 1.1m gallons of water and recovered more than half of the tritium released, officials said, adding that the concentration of tritium in the groundwater had declined.
Xcel has now said in a statement: “Constructing the barrier wall is another step the company is taking to try and ensure that the small amount of tritium still present in the groundwater remains within the plant boundaries and can be safely recovered, stored and reused on site.” The Xcel website said: “We will continue recovering impacted groundwater until our monitoring wells indicate the groundwater meets the EPA’s [Environmental Protection Agency’s] Safe Drinking Water Act standards.”
According to the EPA, water is safe enough to drink if the amount of tritium is less than 20,000 picocuries per litre. In November 2022, the tritium level in groundwater within the plant’s boundaries was about 5m picocuries per litre, the Xcel website said. By August, the highest tritium level was 900,000 picocuries per litre within the plant’s boundaries. However, in water adjacent to the Mississippi River, the highest tritium level was only 1,000 picocuries per litre. As yet, tritium has not been detected in the river, Xcel noted.