MONTICELLO, Minn. — A nuclear reactor produces steam to rotate a giant turbine, every day and night, at a plant between St. Cloud and the Twin Cities.

Xcel Energy's Monticello Nuclear Generating Plant operates nearly constantly and has for 48 years.

The turbine itself and the walls of the control room are still retro-green shades of avocado and mint.

But the plant was updated between 2009 and 2013, and it is situated to play an important role in Minnesota's transitioning energy landscape.

Nuclear power holds an important place in Xcel's energy output now, and that will continue in the near future.

Xcel, Minnesota's largest electric utility, hopes to expand the Monticello plant's license from 2030 to 2040, as it closes its coal plants and moves toward carbon-free energy production by 2050.

"It's a carbon-free energy source," said Xcel Energy President Chris Clark about nuclear power. "It's a very efficient process, as far as being able to get a lot of energy out of a very small amount of fuel."

Businesses and governments are working to limit greenhouse gas emissions, which trap heat in the atmosphere and speed up climate change. Fossil fuels, like the natural gas and coal used for electricity production, are a primary source of the greenhouse gas carbon dioxide.

Nuclear power is carbon free, but it carries its own baggage. Nuclear waste is long-lasting and toxic and, therefore, requires special storage.

The conversation about nuclear has shifted to some extent as the effects of climate change become more apparent in Minnesota and across the globe.

Nuclear power makes up 20% of the energy output in the U.S. as a whole, according to the federal Nuclear Regulatory Commission.

Within Xcel, nuclear made up 30% of energy in 2018, a number expected to drop to 25% by 2024, according to an Xcel Energy information sheet.

Xcel plans to run its Prairie Island nuclear reactors until those licenses expire in 2033 and 2034. The company has not made a decision on the future of that plant, according to spokesman Randy Fordice.

"I think there's a mix of views on nuclear in the climate movement," said Noa Shavit-Lonstein, an organizer on staff with MN350, a nonprofit that promotes climate justice. "It is an energy source we can use without this climate-damaging pollution, but there are a lot of problems that come up."

To Republicans like state Sen. Jerry Relph, R-St. Cloud, nuclear power fits into an "all-of-the-above" energy strategy.

"I'm a big supporter of nuclear," Relph said at a June event held by the St. Cloud Times. "I think we made a big mistake back in the '80s when we stopped building nuclear plants. It's clean. And you can deal with the byproduct."

Former Minnesota Gov. Mark Dayton, a Democrat, was opposed to nuclear power, said Ellen Anderson, director of the Energy Transition Lab at the University of Minnesota and a former DFL state senator.

Gov. Tim Walz, also a Democrat, proposed that the state get to 100% clean energy by 2050. "Clean" meaning free from fossil fuels.

A lot of experts believe nuclear is needed to get to a carbon-free future, Anderson said.

And nuclear energy tends to have bipartisan support these days, she said. But she doesn't know which lawmakers support or oppose nuclear power.

Walz's clean energy plan had support in the DFL-led House but didn't make it into the session's final omnibus bills.

"It's really hard to find that bipartisan solution," Anderson said.

Early this month Xcel shared its 15-year plan with the state Public Utilities Commission. Plans for the Monticello nuclear plant also have to go through the NRC.

Three of Xcel's coal plants are in Becker, not far from Monticello. And all three of those coal plants are slated to close by 2030, along with the Allen S. King plant in Oak Park Heights.

The towering coal chimneys in Becker are visible from U.S. Highway 10 and Interstate 94. But the nuclear site is more subtle.

St. Cloud Times reporters toured it July 18.

One large stack vents hydrogen and other gases from the plant, and cooling towers line part of the campus along the Mississippi River.

The plant uses river water in cooling processes, but big pipes of river water weren't enough to cool the large room in the Turbine Building. It was hot in there during the tour due to high outside temperatures and heat generated by the turbine.

It generates enough energy to power near 800,000 homes, said Jason Kindred, the plant's general manager.

In coming years, Xcel plans to ramp up its solar and wind power generation and build a natural gas plant in Becker. Natural gas and nuclear will help the company provide service when wind and solar can't meet demand, such as during polar vortex temperatures.

"It's critical that we keep a reliable system and an affordable system," Clark said. "It's a major change to take that coal out of that system."

By 2034, three-quarters of Xcel's energy may come from carbon-free sources, including 18% nuclear, 37% wind and 17% solar, according to Xcel's 15-year plan. Natural gas would make up the other quarter of that mix.

Not everyone supports the construction of a new gas plant.

"When you build a new plant you are locking in fossil fuel emissions for decades to come," Anderson said.

Shavit-Lonstein made the same point.

"I think our community deserves better and our climate deserves better than that," she said.

If Xcel is allowed to execute its plan, Monticello's plant will be the only nuclear generator in the state after 2034. It would be licensed through 2040 and possibly again through 2050.

Clark said the utility wants to revisit the license after 10 years to see how technologies have changed.

"There's a lot of exciting things happening in our industry on the technology side," Clark said, mentioning battery storage and other innovations.

"We're not trying to prejudge it," Clark said. "We're trying to be open."

The future of nuclear power in Minnesota is unclear after 2050.

There are new nuclear technologies in the works, such as small modular reactors, Clark said.

The reactor in Monticello is about five stories tall and encased in several protective layers, including thick concrete. Next to the reactor is a special pool that stores spent, radioactive fuel, before it's moved to dry storage.

"I think there's a role for nuclear in the long term," Clark said.

Anderson, with the Energy Transition Lab, is not sure.

"It's very much up in the air," she said.

Correction: This story has been changed to indicate that the future of the Prairie Island nuclear reactors is undecided for the years after their licenses expire.

An AP Member Exchange shared by the St. Cloud Times.