By Timothy Gardner

WASHINGTON, Jan 20 (Reuters) - The U.S. nuclear power regulator has certified the design for the NuScale Power Corp's small modular reactor, the first such approval in the country for the next generation technology.

The Nuclear Regulatory Commission's approval, published in the Federal Register late on Thursday, clears a hurdle for NuScale. The company plans to build a demonstration small modular reactor (SMR) power plant at the Idaho National Laboratory. NuScale says the six-reactor, 462 megawatt Carbon Free Power Project will be fully running in 2030.

There are significant questions about rising costs of the demonstration plant, expected to provide electricity to the Utah Associated Municipal Power Systems (UAMPS). NuScale said this month the target price for power from the plant is $89 per megawatt hour, up 53% from the previous estimate of $58 per MWh.

Backers of next generation reactors including President Joe Biden's administration and many Republican lawmakers, say they are crucial in curbing climate change. NuScale says they will be safer than today's far larger conventional reactors, but the reactors, like conventional nuclear plants, are expected to produce highly toxic waste, for which no permanent fix has been developed.

The U.S. Department of Energy has provided more than $600 million since 2014 to support the design, licensing and siting of NuScale's power plant and other small modular reactors. NuScale and other companies that succeed in building next generation reactors could receive for the first time lucrative production tax credits contained in last year's Inflation Reduction Act signed by Biden.

"SMRs are no longer an abstract concept," said Kathryn Huff, assistant secretary for nuclear energy at the Energy Department. "This is innovation at its finest and we are just getting started here in the U.S."

NuScale also hopes to build SMRs in Romania, Kazakhstan and Poland, despite concerns from nuclear safety experts who say Russia's invasion of Ukraine and occupation of the Zaporizhzhia plant should make the industry think seriously about developing plants in the region. (Reporting by Timothy Gardner; Editing by David Gregorio)