Minnesota power plant to temporarily shut down after new leak of radioactive water detected

A Minnesota nuclear plant where 400,000 gallons of radioactive water leaked last year is temporarily shutting down after discovering a smaller leak this week.

Xcel Energy said it will begin powering down its plant in Monticello on Friday to expedite repairs needed to permanently resolve a leak of tritium-contaminated water. The length of the shutdown has not yet been determined but should not impact customers' electric service, the Minneapolis-based utility company said.

Xcel Energy and state agencies publicly announced last week the initial leak of roughly 400,000 gallons of water containing tritium -- a byproduct of the production of electricity by nuclear power plants that emits low levels of radiation.

The initial leak was detected in late November through routine groundwater monitoring systems and occurred in a water pipe that runs between two buildings at the plant, which is located along the Mississippi River about 40 miles northwest of Minneapolis.

The leak does not pose any health and safety risk to the local community or the environment and the tritium levels are below Nuclear Regulatory Commission safety thresholds, Xcel Energy said. State officials monitoring the cleanup of the water also said the leak had not reached the Mississippi River or contaminated drinking water sources.

Xcel Energy said it had been capturing the water from the leaking pipe and rerouting it back into the plant for re-use until it could install a replacement pipe in mid-April. Though on Wednesday, monitoring equipment indicated that over the past two days "a small amount of new water from the original leak had reached the groundwater," the company said in a press release on Thursday.

The new leakage is estimated to be in the "hundreds of gallons" and "will not materially increase the amount of tritium the company is working to recover and does not pose any risk to health or the environment," Xcel Energy said.

Continued monitoring has determined that the leaked water "remains fully contained on-site and has not been detected beyond the facility or in any local drinking water," the company said.

"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 statement. "We are continuing to work with and inform our state, federal, city and county leaders in the process."

The company reported to state officials on Thursday that the new leak was still ongoing, according to the Minnesota Pollution Control Agency, which is overseeing the cleanup of the impacted groundwater along with the Minnesota Department of Health.

The agencies said they are "encouraged" by the "immediate action" taken by Xcel Energy to address the leak.

"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," the Minnesota Pollution Control Agency said in a statement Thursday.

So far about 32% of the released tritium has been recovered, Xcel Energy said Thursday.