Pueblo County Commissioners are urging Xcel Energy to consider converting its coal-fired Comanche power plant near Pueblo to use nuclear power to spin the existing generators instead of demolishing the plant.

Xcel has proposed closing the last of three generating units at the plant by 2040 to help meet Governor Jared Polis’ carbon-free by 2050 mandate.

“Pueblo County has been the home of our Comanche Station for more than 40 years, and Xcel Energy remains committed to the area,” said Michelle Aguayo, Media Relations Representative for Xcel Energy in a statement to The Denver Gazette. “We are actively engaging with stakeholders on how our proposed plans will impact the community, while working towards our clean energy goals.”

The Commissioners touted new small modular reactor (SMR) technology as a potential alternative to razing the Comanche plant and billing ratepayers for the demolition and site renovation.

Saving that infrastructure for use with SMRs would not only save millions by reusing much of the existing infrastructure, but the converted plant would also continue to support Pueblo and Pueblo County with more than $15 million per year in tax revenues and more than 100 high-paying jobs, according to the commissioners.

While not committing to any particular plan for the plant, Xcel will be presenting its plan to the Colorado Public Utilities Commission in November, which ultimately will decide the fate of the plant and its possible closing date.

Environmental groups argue that phasing out fossil fuels-fired plants like Comanche by the end of the decade is key to preventing the worst effects of climate change.

“We continue to evaluate all of these proposals and suggestions and will reply in total when our response is due in November,” said Aguayo.

The new SMR technology developed by Portland, Oregon, company NuScale Power, LLC, promises scalable generating capacity of up to 12 small, individual modular reactors that can be combined in a common reactor building.

NuScale’s patented technology received U.S. Nuclear Regulatory Commission (NRC) design approval in August 2020, but no plants have been completed, though there is interest in Canada and Poland.

Each module stands 76 feet tall and 15 feet in diameter and uses only one-twentieth of the amount of nuclear fuel used in a large-scale reactor.

Any module in an array can be taken offline for maintenance or refueling while the other modules are operating, something not possible in traditional nuclear power plants.

The internal design circulates water through the core and into a heat exchanger that boils outside water for steam generation without using any electrically powered pumps. The water circulation inside the reactor uses natural convection, with heated water rising upward into the heat exchanger where it creates steam to turn the generators, and cooler, denser water descending back to the reactor core in a continuous loop. Cooled water from condensed steam is also recirculated.

The entire module is submerged below ground in a pool of water sized to provide long-term external heat absorption that keeps the reactor from overheating as it cools during a shutdown, again without the need for pumps.

The safety implication is that there is always sufficient external cooling capacity to prevent a meltdown such as the one at the 2011 incident at the Fukushima, Japan, nuclear power plant that was caused by failures in coolant circulating pumps. In that event, tsunami flooding destroyed backup generators and emergency power battery banks that ran the pumps for a time were quickly exhausted, leading to a core meltdown.

NuScale’s design does not require electricity to safely shut down the reactor. Gravity drops the control rods into the nuclear core, shutting down the fission reaction if power to the electromagnets holding the control rods up is interrupted.

“NuScale SMRs are particularly well-suited to siting at retiring coal plants, helping host communities like Pueblo County and plant workers participate in the transition to a decarbonized energy system, while also preserving local tax base and continuing to provide local economic benefits,” said NuScale Director of Sales Cheryl Collins. “Additionally, some coal plant infrastructure can be repurposed and reused, such as cooling water delivery systems, potable water, site fire protection, switchyard, and buildings, leading to critical capital cost savings.”

“Looking forward, there are several different technologies that could meet the need for firm generation including fossil gas with carbon capture, green hydrogen use in turbines, long-term storage, and modular reactors,” said Will Toor, Colorado Energy Office executive director in a statement to The Denver Gazette. “As these technologies come forward into resource planning, the state will look at the cost of the technologies, the timing of when they could come online, and whether they support other state environmental and energy policies.”

Not everyone is happy with the proposal, however.

In a guest column in the Pueblo Chieftain, Renewable Energy Coalition of America president Ken Danti accused the county of an “assault” on renewable energy “with no public input.”

Danti had several complaints about the prospect of using nuclear generators at the Comanche plant including:

“Nuclear generation can’t be turned on or off quickly during regular operation,” Danti said. “It can be turned off fast during an emergency but at great expense.”

But an April 2021 report by the Pacific Northwest National Laboratory analyzing NuScale and another SMR system describes several ways to reduce or increase capacity fairly quickly depending on demand, including taking modules offline for extended periods of low grid demand or changing power output from one or more modules while keeping the output high on others.

Danti also stated that nuclear power

is “the most expensive form” of electricity. That has been true in the past, but the new SMR technology substantially closes that gap because, for one thing, the reactors are built in a factory and can be shipped to the site by ship, rail or truck as complete units needing only to be installed and fueled, the PNNL report says.

Danti also points out that the major elephant in the room when it comes to nuclear power is storage of the spent nuclear fuel (SNF).

In 1982 Congress passed the Nuclear Waste Policy Act and in 1987 designated Yucca Mountain, Nevada, as the location that the Department of Energy was allowed to consider for the construction of a national high-level waste repository situated inside the mountain more than a thousand feet below its summit and a thousand feet above the nearest water table.

Yucca Mountain is adjacent to the Nevada Test Site, where nuclear bombs were tested and is 90 miles from Las Vegas. The facility has been kept closed by what the Government Accountability Office said is political reasons, not technical or safety reasons.

This leaves spent nuclear fuel sitting in water-filled pools or in dry-cask storage at 80 reactor sites around the nation, 23 of which are not producing electricity using nuclear fuel, including the Fort St. Vrain generating station near Platteville.

Fort St. Vrain was built in 1979 as one of only two high temperature gas-cooled nuclear power reactors in the United States. After technical problems created financial problems for Public Service Co., now part of Xcel Energy, the plant was shut down in 1989 and was converted to natural gas in 1996, but the spent fuel rods remain underwater on the site.

The handling and storage of spent nuclear fuel has been a problem since nuclear power was invented.

France, whose 56 nuclear power plants produce some 75% of its carbon-free electricity, concluded that underground storage is the optimal plan.

The French government has committed 25 billion Euros to excavating storage tunnels 500 meters below ground that will cover 25 square kilometers and will be able to accept spent nuclear fuels for a century.