The National Nuclear Security Administration (NNSA) “before November 2018” moved roughly half a ton of weapon-usable plutonium to the Nevada National Security Site from the Savannah River Site, in Aiken, S.C., the agency said Wednesday in a bombshell court filing.

The plutonium is part of a 1-metric-ton cache a federal judge in South Carolina ordered the NNSA to move out of that state by Jan. 1, 2020. The agency plans to keep about half of that plutonium at the Nevada National Security Site’s Device Assembly Facility into the next decade, according to the Wednesday filing.

Nevada thought plutonium shipments from Savannah River might begin by the end of January. As it turned out, shipments finished at least a month before the Silver State sued the NNSA in the U.S. District Court in Nevada to stop them.

“DoE may now publicly state that it has completed all shipment of plutonium (approximately ½ metric ton) to Nevada pursuant to its efforts to comply with the South Carolina U.S. District Court order,” Bruce Diamond, NNSA general counsel, wrote in a declaration filed with the U.S. District Court for Nevada in Reno.

Diamond told the court he would not reveal further details of the shipment to Nevada “for reasons of operational security.”

The roughly half-ton of plutonium from Savannah River that was not sent to Nevada will go — if it has not gone already — to the Pantex weapons assembly plant in Texas, according to the NNSA’s plans. 

Sometime in the 2020s, the Los Alamos National Laboratory in New Mexico, which has no room for the material now, will take custody of the plutonium now in Nevada and turn it into cores for future intercontinental ballistic missile warheads. Plutonium stored at Pantex would also be used for cores. The fissile material could shuttle between the Nevada National Security Site and the Pantex Plant before it goes to Los Alamos, NNSA has said. 

In its Nov. 30 lawsuit, Nevada alleged the NNSA needed to do a more detailed environmental review before transporting any of the plutonium at issue to the Device Assembly Facility. The NNSA told the Nevada court that the agency had done all the required reviews.

Nevada Gov. Steve Sisolak (D) said in a statement he was “beyond outraged by this completely unacceptable deception from the U.S. Department of Energy,” which “led the State of Nevada to believe that they were engaging in good-faith negotiations with us.”

Nevada’s senior U.S. Senator promised she would haul NNSA into her office in Washington for an explanation.

In December 2017, the District Court in South Carolina ordered the NNSA to remove the ton of plutonium from the state because the agency missed a deadline set by federal law to turn the material into commercial reactor fuel using the Savannah River Site’s now-canceled Mixed Oxide Fuel Fabrication Facility (MFFF).