Peripatetic Plutonium

The US government has 34 tons of plutonium it wants to dispose of.

By 1990, the US and Russia held something like 65,000 nuclear weapons. The dissolution of the Soviet Union led to significant decreases on both sides. Bill Clinton negotiated an agreement that the US and Russia would each dispose of 34 tons of plutonium from those weapons in a way that would eliminate the plutonium so that it could never be used in weapons again.

The plutonium would be used to power nuclear reactors through what is called mixed-oxide, or MOX, fuel, which contains both plutonium and uranium. Russia had used MOX fuel, but the US had never been successful at it. A facility was to be built at Savannah River, South Carolina, ro produce the fuel.

The Los Alamos ARIES project developed operations to convert the classified plutonium weapons components into unclassified metal pucks. I was part of that project, in charge of the canning module. My team developed a design for plutonium storage cans that I believe is still in use.

Two factors led to the failure of the project in the US, and eventually Russia abandoned the agreement. First was the insistence of a few organizations that the plutonium must be disposed of by deep burial, which would be much more expensive than the reactor fuel route. Second was the ballooning costs and schedule for the Savannah River plant.

Meanwhile, nuclear weapons continued to be taken out of service, and the total plutonium increased to about 50 tons.

Another scheme was developed to dispose of the plutonium. It would be mixed with a diluent whose composition was classified, packaged, and stored in the Waste Isolation Pilot Plant near Carlsbad, New Mexico. Modifications would have to be made to the WIPP license to allow this.

And now come the Silicon Valley boys who want to build reactors and those in the post-DOGE government who want to accommodate them.

Plutonium must be processed inside glove boxes. That applies to ARIES, manufacturing reactor fuel, building nuclear weapon pits, any operation with plutonium until it is thoroughly sealed. Our cans had an internal slip-cover can and two welded stainless steel cans outside of that.

There are many things that can go wrong with plutonium operations, including criticality accidents and fires. There is only one facility in the US that can work with plutonium metal, Los Alamos’s PF-4. It has been beefed up to produce plutonium components for nuclear weapons. The failed Savannah River plant is being reworked for the same purpose. Neither will have much slack.

The ARIES line probably no longer exists at Los Alamos. Much of the surplus plutonium is still in the classified form of weapons components. It is not clear how they would be converted to a form that could be given to the start-up companies, as has been proposed.

Five companies are interested in the plutonium. Oklo has been chosen for initial discussions. Jacob and Carol DeWitt are the founders of the company, and Jacob is CEO. The board has one other person with experience in nuclear science, with the others coming from finance, general management, and utilities. I will borrow from Dan Yurman’s summary of the companies.

In September 2025 Oklo announced plans to design, build, and operate a fuel recycling facility in Tennessee as the first phase of an advanced fuel center. The firm will organize an investment totaling up to $1.68 billion. The initial investment will be for the construction of a facility in Tennesse to recycle used nuclear fuel into fuel for fast reactors like Oklo’s Aurora powerhouse advanced reactor. The recycling facility will recover usable fuel material from used nuclear fuel and fabricate it into fuel for advanced reactors. 

I should emphasize that these are Oklo’s plans. Oklo’s website talks about “proven technology,” but all its examples are from other operations, some of them decades ago. There is no mention of operating Oklo facilities. The website also mentions a number of possible fuels, including high-assay, low-enriched uranium (HALEU), spent fuel from other reactors, and the surplus plutonium. Fabrication and reactor behavior of those fuels will be different, but the website slides over that. The use of plutonium will require a great deal more of the fabrication facility, which will mean more costs.

Exodys “is developing a liquid-fueled fast reactor that uses low-pressure, high-temperature liquid chloride salt. They claim that this kind of reactor can accept many types of fuel. They plan to blend the plutonium with spent reactor fuel or depleted uranium into their salt fuel. I should say here that I have done a small amount of work with liquid salts and fail to see why anyone thinks this is a good idea for a nuclear reactor. Yurman gives additional information about their plans.

Carl Perez is the CEO and has a bachelor’s degree. His bio includes nuclear work, but his degree major is not given. Jean-Christophe Piroux, the chief technology officer, has a background in France’s nuclear industry. Like Oklo, apparently no facilities of their own.

In addition to the 34 tons of plutonium, the government has a large quantity of depleted uranium from weapons production that it would like to dispose of. Depleted uranium is mostly U-238, with even less U-235 than in natural uranium. It resides in giant cylinders of UF6.

From Yurman,

In July 2025 SHINE Technologies LLC and Standard Nuclear, announced a strategic partnership to develop mehtods of nuclear fuel recycling, The agreement reportedly establishes a framework and lays the groundwork for domestic nuclear fuel production. SHINE expects to begin construction of its first commercial recycling facility in the early 2030s, with an initial capacity to process 100 metric tons per year.

Greg Piefer is the founder and CEO and holds a Ph.D. in nuclear engineering.  Their website lists several directors with backgrounds in nuclear issues, along with others in finance and management. SHINE seems to be a bit older company than the others, although there is no indication that they have handled plutonium.

Standard Nuclear has agreed to work with Shine Technologies on nuclear fuel recycling. It claims to have a process to re-enrich depleted uranium but keeps this information proprietary. Standard Nuclear does not have a website of its own.

Flibe Energy is developing another molten-salt reactor, a thorium fuel cycle in lithium fluoride. Thorium fuel cycles require something beyond thorium to begin the fuel cycle, and Flibe sees the plutonium as that source. Kirk Sorensen is founder, CEO, and Chief Technologist. Flibe has a four-person board of directors, with one other person with a technical background. Again, no facilities, no plutonium experience. My own prejudice again, but combining a thorium fuel cycle with molten salt makes two losers.

The boards are overwhelmingly, stiflingly male. A couple have retired military officers.

None of this sounds good to me. The national laboratories are overwhelmed with requirements for weapons pit production. The companies have no experience or facilities for handling plutonium. And this is being done as the Trump administration guts the Nuclear Regulatory Commission and other health and safety regulations.

Photo: Cherenkov radiation, Idaho National Laboratory

Cross-posted to Nuclear Diner