MOX, PMDA, Russia

An aerial view of the terminated Mixed Oxide Fuel Fabrication Facility, which is located at the Savannah River Site.

The federal government's decision last year to cancel the knotty and never-completed Mixed Oxide Fuel Fabrication Facility did not violate a roughly two-decades old plutonium disposition agreement that gave rise to the project, according to a newly published U.S. State Department arms control and nonproliferation document.

The so-called 2019 Compliance Report, handled by the Bureau of Arms Control, Verification and Compliance, states the termination of MOX at the Savannah River Site was not "inconsistent" with the U.S.'s obligations under the Plutonium Management and Disposition Agreement.

The Trump administration's pursuit of dilute-and-dispose – the MOX alternative that involves mixing plutonium with inert material for burial in New Mexico – is also in bounds, though immature, the report notes.

The U.S. and Russia years ago signed off on the PMDA, consenting to each eliminate 34 metric tons of plutonium from their defense programs. That's enough material for thousands of nuclear weapons.

The PMDA was amended in 2010, leading to MOX. The facility, in which billions of dollars and years of work were sunk, was designed to turn the surplus cache into fuel for commercial nuclear reactors. That won't be happening now.

Russia in recent years suspended its participation in the plutonium pact, citing Washington's shift away from MOX and toward dilute-and-dispose.

"The U.S. Department of State actually admits that the U.S. administration tried to change the disposition method from irradiating its excessive plutonium in nuclear reactors to the dilution-burial method," reads an April 2018 statement from the Russian foreign affairs ministry.

Russia's position that the U.S. has breached the PMDA "remains without merit," according to the 2019 Compliance Report.

National Nuclear Security Administration chief Lisa Gordon-Hagerty in a June interview with the Aiken Standard said the U.S. was not retracting from the agreement – "No, I would say absolutely not" – and welcomed interactions with Moscow.

"Yet, the Russians haven't necessarily indicated that they would be interested in talking to us about that," said Gordon-Hagerty, who is also the U.S. Department of Energy's under secretary for nuclear security.

The international impasse doesn't change U.S. plans to pivot away from MOX, according to Gordon-Hagerty.

"But nonetheless, our plan is to dilute and dispose of 34 metric tons of excess plutonium, and that is our stance, and that will continue to be our stance," she said.

Colin Demarest covers the Savannah River Site, the U.S. Department of Energy, the National Nuclear Security Administration and government in general. Follow him on Twitter: @demarest_colin