Scientists at a federal facility have created more energy from nuclear fusion reactions than they used to start the process, Energy Secretary Jennifer Granholm confirmed on Tuesday.

Granholm said the development moved the country significantly closer to the possibility of fusion energy, a carbon-free source, with officials calling the discovery a breakthrough.

“This is one of the most impressive scientific feats of the 21st century,” Granholm said at a press conference, adding that researchers have been working on the effort for 60 years. 

Nuclear fusion refers to fusing atoms together to produce energy. The type of nuclear energy that is commonly used today does the opposite, deriving energy from splitting atoms apart.

For decades, scientists have sought to advance nuclear fusion as a clean energy source that doesn’t produce the radioactive waste that occurs when atoms are split apart. Yet it may have some radioactive byproducts that stay at the power plant site and do not require long-term storage like current nuclear waste, an expert recently told The Hill.

Granholm said that the administration had a goal of achieving commercial fusion within a decade.

“The president has a decadal vision to get to a commercial fusion reactor within, obviously, ten years, so we’ve got to get to work,” she told reporters. 

However, at the press conference, Kim Budil, director of the Lawrence Livermore National Laboratory where the breakthrough occurred, said it could take “decades” before the technology is commercialized. 

“There are very significant hurdles” in both science and technology, Budil said. 

But, she added, “with real investment and real focus, that timescale can move closer.”

Marvin Adams, deputy administrator for defense programs at the National Nuclear Security Administration, said fusion is also “an essential process in modern nuclear weapons.”

He said it would support the country’s national security by bolstering the image that “we know what we’re doing” to deter other countries from attacking the U.S.

On the clean energy side, Granholm also said that private investment, as well as public research, will be important in scaling the technology. 

“We need the private sector to get in the game. It’s really important that there has been this incredible amount of U.S. public dollars going into this breakthrough, but all of the steps that…will be necessary to get this to commercial level will still require public research and private research,” she said.  

She said there has been “a huge interest among the private funding community” like startups.

The breakthrough also won praise from the other side of the aisle. 

“Today’s announcement by Lawrence Livermore National Lab is incredibly exciting,” Rep. Frank Lucas (Okla.), the top Republican on the House Science, Space and Technology Committee, said in a statement.

“The fundamental knowledge we gain through federally funded experiments like this will ultimately be translated into commercial energy sources by the private sector. This approach to research and development is what has kept America at the cutting edge of technological development for generations,” Lucas added.

The experiment consisted of using laser technology to fuse atoms together to create energy. It used  2.05 megajoules of energy input and had an output of 3.15 megajoules. 

It follows an experiment last year where scientists came relatively close to breaking even, generating 70 percent of the energy they put in. 

Updated: 1:26 p.m.