WASHINGTON, May 29 (Reuters) - The U.S. Nuclear

Regulatory Commission has approved NuScale Power's ( SMR )

design for a 77 megawatt reactor, a document on the regulator's

web site said on Thursday, completing one hurdle the company

needs to build a small modular reactor.

NuScale had originally sought and received NRC approval for

a smaller 50 MW reactor design. The company sought a bigger 77

MW design to improve economics and performance of its planned

small modular reactors (SMRs).

Backers of nuclear power say SMRs will be safer from

proliferation risks and can reduce costs for multiple plants

because they can be built in a factory instead of onsite.

Critics of SMRs say they will be more expensive to operate than

conventional reactors, which are larger and have economy of

scale.

NuScale, the only U.S. company with an approved design,

wants to build the country's first SMR. But in 2023 it axed its

first project with a municipal power group in Utah, despite a

U.S. government promise of $1.35 billion in funding over 10

years for the plant, known as the Carbon Free Power Project. As

costs rose, several towns had pulled out of the project.