Dealing a blow to the most advanced small modular nuclear reactor project in the U.S., the city of Logan, Utah, has announced that it is pulling out of the UAMPS Carbon Free Power Project, an effort to build a compact NuScale Power LLC power plant at the Idaho National Laboratory.

Located in northern Utah, Logan is a member of Utah Associated Municipal Power Systems, or UAMPS, a nonprofit organization that provides wholesale electricity to 47 members, mostly smaller municipalities, in Utah, California, Idaho, Nevada, New Mexico and Wyoming. UAMPS in 2015 signed on to be the first customer for the NuScale project, which is scheduled to come online in 2029 and comprise 12 60-MW reactors. Small modular reactors have long been seen as the successor to the massive nuclear plants, mostly built in the 1970s and 1980s, that make up the U.S. nuclear fleet, offering lower costs and enhanced safety features.

But some of UAMPS' member cities have expressed reservations about the project, which requires them to put up millions of dollars in funding for a promising technology that remains largely untested.

Logan becomes the most prominent city to drop out; the city council of Lehi, Utah, was reportedly considering a resolution to exit the project at its meeting Aug. 25.

The Logan City Council's resolution cited "increased projected costs" as the primary reason for the city's withdrawal. "We don't have the experience to be swimming in these waters," Logan Finance Director Richard Anderson told the Deseret News, a Salt Lake City newspaper, in an Aug. 24 article. "I didn't feel good about it."

"NuScale remains committed to and excited for the UAMPS Carbon Free Power Project and the installation of one of our 12-module, 720-MW small modular reactor power plants," said NuScale spokesperson Tiffany Austin, in an email. "UAMPS is one of the most innovative and forward-thinking organizations, and the CFPP’s long-term strategy to reduce carbon emissions and replace aging coal-fired plants with non-fossil fuel, and medium-sized, flexible power generating sources such as our power plant has not changed."

NuScale, a subsidiary of Fluor Corp., has received millions of dollars in financial support from the U.S. Department of Energy to develop small modular reactors. The company has completed the third phase of its design certification application with the U.S. Nuclear Regulatory Commission. Like other highly touted nuclear power developments, the Carbon Free Power Project could have trouble competing against the falling price of power from wind and solar power facilities.

In early August the Utah Taxpayers Association, an advocacy group that supports lower state and local taxes, announced its opposition to the project, saying that it will be costly compared to solar, wind and energy storage alternatives and presents unacceptable risks to Utah ratepayers.

The UAMPS will hold a budget meeting in September and could decide to end its participation in the project then. Other UAMPS members, such as the county of Los Alamos, N.M., are also considering whether to continue their participation.

"The sad fact is, this is an experiment, it is not a tried and true design that is ready for production," wrote George Chandler, a Los Alamos lawyer and former municipal judge, in an op-ed in the Los Alamos Reporter.

"If a few [cities] drop out, the project could still go forward," UAMPS spokesman LaVarr Webb said in an email. "Obviously, there must to be enough subscriptions or power sales contracts to make the project viable."