A team of experts has confirmed what the Energy Department has been saying for two years — that burying 34 tons of weapons-grade plutonium would be far cheaper and more practical than completing a multibillion-dollar plant that would turn the radioactive material into commercial reactor fuel.

The report raises pressure on Congress to walk away from a costly project that has been plagued by rapidly escalating costs and an absence of any customers for the fuel it is supposed to produce.

The Department of Energy tried to kill the project in 2013, but Congress has kept it on budgetary life support, with the strong support of South Carolina’s congressional delegation. The study says essentially that sooner or later the Energy Department will be forced to abandon the fuel plant, and the sooner it does so the better.

“The downward performance spiral [expected for the plant] is accompanied by an upward cost escalation spiral that would eventually make DOE’s path-forward decision for them,” the report concluded, “but only after a great deal of money has been wasted.”

The report was delivered to Energy Secretary Ernest Moniz this week by an Energy Department “Red Team” led by Oak Ridge National Laboratory Director Thomas Mason. It was posted online Thursday by the nuclear safety advocacy group the Union of Concerned Scientists.

The maligned Mixed-Oxide Fuel Fabrication Facility at the Savannah River Site near Aiken, South Carolina, is part of a 15-year-old agreement between the U.S. and Russia to each dispose of 34 tons of plutonium taken from nuclear weapons. The aim of the post-Cold War accord was twofold: to discourage another arms race and to prevent the plutonium from being stolen and sold on the black market.

While President Bill Clinton’s administration initially sought to turn some of the surplus plutonium into fuel and dispose of the rest, President George W. Bush’s administration eventually agreed to follow Russia’s lead and convert all of it to a mixed-oxide fuel, called MOX. The 64 tons the two nations vowed to dispose of could be used to make 17,000 bombs.

Construction snafus, high turnover and management problems on the project have slowed progress on the MOX plant, and escalated the estimated cost to build and operate it. In 2013, the Energy Department estimated the project would cost $27 billion. An outside assessment ordered by Congress and published in the spring concluded it could cost up to $47 billion.

Meanwhile, a dueling June 29 study by consultants retained by CBI-AREVA MOX, which is building the South Carolina plant, concluded that the cost of completing and operating the MOX plant was roughly equal to the cost of disposal. The study priced each option at about $20 billion.

Mason’s 19-member team, which included officials at Los Alamos, other national labs and the United Kingdom, said the congressional study overstated the cost of the MOX project while the contractor-funded study understated them.

The Red Team concluded that building and operating the plant over the life of the program would cost between $700 and $800 million per year, while diluting the plutonium and shelving in in an underground facility would cost about $400 million per year – approximately the amount budgeted for the project this year and proposed for next year. It does not provide a bottom-line figure.

The Energy Department has spent more than $4 billion since work on the mixed-oxide facility in South Carolina began eight years ago. It is about 70 percent complete.

While Mason’s Red Team favors diluting the plutonium and storing it in an underground repository in New Mexico, this solution faces serious problems of its own.

The Waste Isolation Pilot Plant, where diluted plutonium would be stored as an alternative to MOX, has been closed for a year and a half following a series of accidents. It’s a deep salt cavern in the desert of Southern New Mexico already used as a repository for low to mid-level nuclear waste generated during the Cold War by weapons production from the nation’s labs.

In February 2014, a truck caught fire below ground at the repository, known as WIPP, limiting activity at the site. Nine days later, a chemical reaction inside a drum of waste at WIPP from Los Alamos National Laboratory in New Mexico caused it to burst. Radioactive contamination spread throughout the repository and some escaped outside, even though WIPP had been heralded as leak-proof. The accident exposed more than 20 workers to radiation.

Follow-up investigations determined that waste packaging policies at Los Alamos created the conditions that led to the release. Organic kitty litter had been used as an absorbent and mixed with the nuclear waste. A mix-up in the transcription of a 2012 technical manual led to the switch from inorganic kitty litter to organic.

The DOE has estimated the cost of restoring WIPP to working order at $500 million, with an eye on resuming some activities by early 2016. But this month WIPP’s manager acknowledged that reopening is going to take longer and cost more than originally announced.

Despite the problems at WIPP, the Union of Concerned Scientists has thrown its support behind the repository as an alternative to MOX.

“Obviously, they have to deal with the safety and environmental issues associated with the accident [at WIPP], but it’s not a showstopper,” said Edwin Lyman, a senior scientist with the global security program at the Union of Concerned Scientists, said.

He said the time for studies has passed, and it’s time for the Energy Department and Congress to commit to a new course for disposing of the plutonium.

Don Hancock of the Albuquerque-based Southwest Information and Research Center, a nonprofit that closely monitors WIPP, also opposes the MOX project.

But he’s skeptical about WIPP as a viable alternative and said the Energy Department should review other options, including storing the plutonium at the Savannah River Site or the Pantex Plant near Amarillo, Texas, where thousands of plutonium pits are already warehoused.

“The Red Team or the Union of Concerned Scientists may be confident that WIPP will reopen in a few years, but I don’t see any real basis for that,” Hancock said. “Going from one bad idea to another bad idea is not the solution to this problem.”

The Center for Public Integrity is a nonprofit, nonpartisan investigative news organization in Washington, D.C.