US utility Xcel Energy has received the necessary approval from the Minnesota Public Utilities Commission (MPUC) to extend operations of the Monticello NPP until 2040, the company said in a statement. MPUC approved Xcel Energy’s application to allow increased storage of used nuclear fuel at the site, paving the way for at least 10 more years of operation. The single-unit boiling water reactor plant began commercial operation in 1971 and has recently completed work to replace key components and increase its generating capacity from 600 MWe to 671 MWe.

As part of extending the use of the Monticello plant, Xcel Energy applied to the Nuclear Regulatory Commission (NRC) to extend the plant’s operating licence. The plant was built in 1970 with a 40-year federal operating licence, and it was relicensed in 2010. Xcel has asked the NRC to extend Monticello for another 20 years after its current license expires in 2030. A decision from federal regulators is expected in late 2024.

Meanwhile, MPUC unanimously permitted Xcel to expand its storage space at Monticello to house an additional 36 canisters of high-level nuclear waste – used fuel. Monticello currently houses 30 steel casks in concrete storage structures. Xcel says it plans to add 14 waste casks at Monticello between 2030 and 2040 if its federal license is renewed. The company wants space for more if the plant continues running beyond 2040, hence its request for 36 more casks.

However, Xcel would have to go back MPUC for any further approvals to extend Monticello's life beyond 2040.

The Monticello plant has been under increased scrutiny since a leak of water containing radioactive tritium last November. In March, Xcel temporarily shut down the plant to repair the leak, and has been pumping groundwater to recover the tritium.

Image: Dry fuel storage at the Monticello NPP (courtesy of Xcel Energy)