Struggling Portland nuclear energy company NuScale Power laid off 154 or 28% of its workforce Friday, the company said Monday.

NuScale had more than 550 employees at the start of the year. Its headquarters are in Portland but the vast majority of staff is in Corvallis.

The company pioneered a new class of nuclear power plant called a small modular reactor, based on technology developed at Oregon State University. Advocates say smaller reactors are cheaper and safer than conventional nuclear plants and can be readily scaled up to meet growing demand.

NuScale has won key government approvals for its technology and $600 million in federal backing but has struggled to convince utilities that its reactors are practical. It’s announced many agreements to explore the technology but no firm deals to build reactors.

In November, a consortium of western power agencies called off plans to build a NuScale reactor in Idaho. The news triggered a collapse in NuScale’s stock price. Shares closed Friday at $2.62. The stock has traded as high as $11.32 in the past year.

NuScale had $117 million in cash and short-term investments at the end of September, according to its most recent quarterly financial report, down by $150 million from the start of the year.

NuScale’s stock began trading on Wall Street in 2022 through an unconventional mechanism called a special purpose acquisition company, or SPAC. NuScale merged with a publicly traded investment fund and adopted that firm’s stock listing, thereby escaping the investor scrutiny that usually accompanies public offerings.

Mass layoffs have been exceedingly rare in Oregon since the pandemic recession ended and the state’s unemployment rate is at a historic low, 3.6%.