DOE Headquarters, Forrestal Building, DC (copy)

The James Forrestal Building, the headquarters of the U.S. Department of Energy in Washington, D.C.

In its latest legal maneuver, the state of Nevada has accused the U.S. Department of Energy of going rogue and conducting what it deems to be "plutonium smuggling" – trucking a half-metric ton of weapons-grade plutonium from the Savannah River Site into the state sometime last year.

"Congress did not mandate that DOE move this weapons plutonium from South Carolina to Nevada," the state's legal team wrote in a Dec. 16 federal court filing. "Nor did Congress dictate that this plutonium be stored indefinitely in unsafe storage conditions at the Nevada National Security Site."

The Nevada security site is northwest of Las Vegas. The Silver State contends keeping the plutonium at NNSS endangers the state and its residents, and the shipments there violated environmental law.

The aggressive language Nevada employed recently follows a monthslong pattern. In a March 4 brief filed with a federal appeals court, the state conflated the plutonium – meant to be introduced into the defense stockpile for nuclear weapons work – with "irradiated garbage."

"The United States Department of Energy … is attempting to turn the state of Nevada into the nation's radioactive dump," the same federal appeals filing reads.

The DOE has pushed back on those characterizations repeatedly. In a Nov. 20, 2018, letter to Nevada leaders, then-National Nuclear Security Administration Chief of Staff William "Ike" White (who now leads the Energy Department's nuclear cleanup office) described the material as "vital" to national security missions and "not waste."

And both Rick Perry and Dan Brouillette – the former and current secretary of energy, respectively – have promised to move the half-metric ton of plutonium out of Nevada by the end of 2026. Those efforts would begin, Perry promised, in 2021.

The Energy Department's National Nuclear Security Administration before November 2018 trucked a half-metric ton of defense plutonium to the Nevada National Security Site for staging, partially satisfying a 2017 court mandate.

The shipments were analyzed and publicized in a July 2018 environmental study: A total 1 metric ton of weapons-grade plutonium would be sent to Texas, to the Pantex Plant, or Nevada, to NNSS, for staging, the study stated. The cache would then be relocated to Los Alamos National Laboratory in northern New Mexico – a plutonium center of excellence – for the production of nuclear weapon cores, or pits.

A letter from Perry to U.S. Sen. Catherine Cortez Masto, a Nevada Democrat, described the plutonium as expressly "not nuclear waste."

Nevada sued the federal government to prevent the shipments from happening in the first place. But, as it was later revealed, the suit was filed after the shipments had been completed – a fact the Energy Department and judges have often pointed to when discussing the case's relevance.

Nevada lawmakers and elected officials have described the whole ordeal as furtive. In February, Nevada Gov. Steve Sisolak said the campaign destroyed "any semblance of trust" that existed between his state and the DOE.

"Nevada did not want to become the new South Carolina," the state has argued, referencing the Palmetto State's rolling tug-of-war with the Energy Department.

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