Savannah River MOX Plant: Plutonium Disposition

Reference article · Updated 2026-11-06

Key facts

The US-Russia Plutonium Management and Disposition Agreement of 2000 committed each side to dispose of 34 tonnes of weapon-grade plutonium.
In May 2018 the Energy Secretary notified Congress of a waiver to end MOX construction; the NNSA formally terminated the project on 10 October 2018.
One DOE cost report put dilute and dispose at no more than 19.9 billion dollars against 49.4 billion for continuing MOX.
Russia suspended the agreement in October 2016 and formally ended its participation in October 2025.

What the MOX project was meant to do

Mixed-oxide (MOX) fuel combines plutonium oxide with uranium oxide, usually depleted uranium, to make fuel pellets that can be burned in power reactors designed or licensed for it. The US Mixed Oxide Fuel Fabrication Facility at the Savannah River Site in South Carolina was planned to convert surplus weapon-grade plutonium into such fuel, so that burning it in reactors would leave the plutonium in spent fuel, a form that is less attractive for reuse in weapons. The role of depleted uranium as a feed material links this project to the DU basics page, and the broader fuel cycle context appears on the fuel cycle overview.

MOX fuel is not unique to weapons plutonium. Plutonium recovered by reprocessing civilian spent fuel has been fabricated into MOX and loaded into reactors in several countries, and the technology is established in principle. What was new at Savannah River was the scale of the feed (weapon-grade plutonium from dismantled weapons), the need to remove impurities such as gallium from it, and the licensing of a new plant in the United States, where commercial MOX fuel use had not been established. These first-of-a-kind features are among those that observers have linked with the cost growth described below.

The facility was built by a contractor consortium, at the time CB&I AREVA MOX Services, under an NRC construction authorisation, and it was to be supplied with plutonium from the National Nuclear Security Administration (NNSA), part of the Department of Energy.

The US-Russia plutonium agreement

The project originated in a bilateral commitment. In 1998 the United States and Russia each announced that they would convert 34 tonnes of surplus weapon-grade plutonium into a form that could not readily be returned to weapons, and the Plutonium Management and Disposition Agreement (PMDA) formalised this in 2000. A protocol in 2010 revised the agreement and set the method for disposal as irradiation in reactors. Under it, each side would remove 34 tonnes from its defence programme, and the two sides would cooperate on verification with the IAEA.

On 3 October 2016 the Russian President signed a decree suspending the agreement, citing what Moscow described as unfriendly actions by Washington and the US failure to meet its commitments. A federal law of 31 October 2016 formalised the suspension. Russia stated it intended to keep its 34 tonnes out of weapons use. In October 2025 Russian legislation formally ended Russia's participation. The US dilute-and-dispose programme does not depend on the agreement.

From cost growth to termination

The project suffered from rising costs, delays and doubts about its financial feasibility. In early 2016 the Department of Energy sought to terminate it and in May 2018 Energy Secretary Rick Perry notified Congress that he was executing a waiver to end construction. The NNSA formally terminated the project on 10 October 2018, beginning a winding-down period of about a year. Congress had resisted termination for several years: the fiscal year 2019 defense authorization act signed in August 2018 mandated continued construction and authorised 220 million dollars for the purpose, but like the previous year's act it allowed the Secretary to waive the requirement.

About 600 workers, roughly one third of the project's workforce, were notified of layoffs beginning in January 2019. The NRC later granted a request from the contractor to terminate the construction authorisation for the partly built facility.

Date	Event
2000	PMDA signed; 34 tonnes each
2010	PMDA protocol revises disposal method to reactor irradiation
Early 2016	DOE seeks to terminate the MOX project
3 October 2016	Russia suspends PMDA
May 2018	Energy Secretary notifies Congress of waiver to end construction
10 October 2018	NNSA formally terminates the project
October 2025	Russia formally ends participation in PMDA

The dilute-and-dispose alternative

Why the choice mattered for disposition can be stated simply. Under the PMDA the aim was not to produce electricity but to make the plutonium unusable for weapons and subject to verification. Both MOX irradiation and dilution with disposal can meet that aim in principle, and they differ mainly in cost, schedule, residual radioactivity and what the end product is: spent fuel in one case and transuranic waste packages in the other.

After the waiver, DOE said it would pursue dilute and dispose for the surplus plutonium. In this approach plutonium oxide is mixed with inert materials to make it difficult to recover, packaged, and sent to the Waste Isolation Pilot Plant in New Mexico, a deep geological repository for defence transuranic waste. DOE reported analysis in which dilute and dispose cost at most 19.9 billion dollars over its lifetime, compared with 49.4 billion dollars for continuing with MOX, and that figure is cited by arms control analysts as a rationale for the switch. The numbers are estimates produced at a given time and have been debated.

The choice has trade-offs that independent observers have discussed. MOX would have produced fuel with some energy value, but it required a working fabrication plant, reactor customers and an operating supply chain. Dilute and dispose is simpler technically, but it relies on repository capacity and on state-level agreements about WIPP's role, and some critics have argued that it treats plutonium as waste, which may hinder future use. Others point out that this was a practical decision about cost. This page reports the positions without adopting one.

Why the case matters for the fuel cycle

The MOX story is a case study in the scale and difficulty of large nuclear construction projects with first-of-a-kind features. It also illustrates how linked political and technical commitments, here an arms-control agreement and a domestic construction project, can unravel together. For readers interested in how the US enrichment sites and their legacy fit into the same federal programme, see the US enrichment page, and for the stockpile of depleted uranium that would have served as MOX feed material see the inventories page.

Frequently asked questions

What was the MOX facility at Savannah River?

A plant planned to convert 34 tonnes of surplus US weapon-grade plutonium into mixed-oxide fuel for reactors. It was partly built when the project was terminated.

When was the project terminated?

The Energy Secretary notified Congress of a waiver in May 2018 and NNSA formally terminated the project on 10 October 2018.

What replaced MOX?

Dilute and dispose, in which plutonium is diluted with other material and sent to the Waste Isolation Pilot Plant in New Mexico.

What happened to the US-Russia agreement?

Russia suspended the PMDA in October 2016, with a federal law following on 31 October 2016, and formally ended its participation in October 2025.

Why was MOX terminated?

Official reasons were sharply rising costs, long delays and doubts about financial feasibility. One DOE estimate put dilute and dispose at 19.9 billion dollars against 49.4 billion for continuing MOX.