The U.S. Department of Energy plans to announce Tuesday that scientists have succeeded for the first time in a fusion reaction that produces a net increase in energy, a major milestone in the multibillion-dollar, decades-long quest to develop a technology that provides unlimited, cheap, clean energy, reports The Washington Post.

The goal of nuclear fusion research is to recreate the nuclear reaction that creates energy on the Sun. This is the “holy grail” of carbon-free energy that scientists have been chasing since the 1950s. Its commercial use is still at least a decade away, but the latest development is likely to be touted by the Biden administration as a vindication of the government’s massive investment over the years.

Huge amounts of public and private money have been invested in the fusion race around the world to create fusion equipment that can supply electricity to the grid with no carbon footprint, no radioactive waste, and with far fewer resources than solar and wind power. Besides the climate benefits, organizers say it could help provide cheap electricity to poor parts of the world.

“To most of us, this was only a matter of time,” said a senior fusion scientist familiar with the work of the National Ignition Facility at the Lawrence Livermore National Laboratory in California, where the discovery was made.

The development was first reported by the Financial Times newspaper on Sunday. It was confirmed by two people familiar with the research, who spoke on the condition of anonymity to avoid getting ahead of the official announcement. Energy Secretary Jennifer Granholm was slated to make the announcement Tuesday at a media event billed as the unveiling of “a major scientific breakthrough.”

The department and the lab declined to comment. A lab official said the researchers were still finalizing their analysis and would not release any official findings until Tuesday.

The science of nuclear fusion is based on colliding two atoms at incredibly high speeds and converting the energy of that reaction into electricity that can power homes and offices without emitting carbon into the air or releasing radioactive waste into the environment.

Scientists have been experimenting with fusion reactions for decades, but so far they have not been able to create a reaction that produces more energy than it consumes. While the achievement is significant, monumental engineering and scientific challenges still lie ahead.

Creating a net increase in energy required one of the largest lasers in the world, and the resources required to reproduce the reaction on the scale needed to make fusion practical for energy production are enormous. More importantly, engineers have yet to develop equipment that can affordably convert this reaction into electricity that can be practically used in the power system.

According to the scientists, creating devices large enough to generate fusion energy on a large scale would require materials that are extremely difficult to manufacture.