Blocking all plutonium shipments to Nevada, as the state desires, would disrupt experiments there that help the government determine whether U.S. nuclear weapons still work as intended, the National Nuclear Security Administration argued in federal court this week.

U.S. District Judge Miranda Du should deny injunction requested by the state in part because it “would require [the Department of Energy] to cease subcritical experiments performed by the Stockpile Stewardship Program (which helps to ensure the Nation’s nuclear weapons stockpile remains safe),” lawyers for the NNSA wrote in a Thursday response to Nevada’s Feb. 6 injunction motion.

Subcritical experiments explosively compress weapon-usable plutonium without creating a nuclear blast. The tests help the agency observe how aging plutonium behaves under stress. The NNSA completed one such experiment, called Ediza, at the Nevada National Security Site this week, Mark Martinez, president of site operator Mission Support and Test Services, said Wednesday at the ExchangeMonitor’s annual Nuclear Deterrence Summit in Arlington, Va.

The NNSA’s Thursday filing is part of a lawsuit Nevada filed Nov. 30 to stop the agency from shipping weapon-usable plutonium to the Nevada National Security Site (NNSS) from the Savannah River Site in Aiken, S.C. In January, the semiautonomous Department of Energy branch acknowledged it had brought about 500 kilograms, or roughly 1,110 pounds, of plutonium to NNSS’ Device Assembly Building well before Nevada sued. 

Du has already shot down one post-shipment injunction request from Nevada, but the state has kept the injunction strategy on life support by appealing Du’s decision to the Ninth Circuit Court of Appeals and asking Du to enjoin further shipments until the higher court rules.

In its Thursday filing, the NNSA said Nevada’s appeal is likely to fail, and that Du has already ruled Nevada is not irreparably harmed by the agency’s transport of plutonium to the Nevada National Security Site. 

Nevada claims the NNSA did not perform a federally required environmental review before shipping the plutonium; the agency claims it completed all the reviews necessary.The Savannah River plutonium that spurred the state lawsuit is not intended for subcritical tests, but material that is needed for tests would be covered by the injunction.

The NNSA has to move 1 metric ton of plutonium out of South Carolina by Jan. 1, 2020, following a December 2017 court ordered in a separate federal lawsuit brought by the state of South Carolina. The half-ton not already in Nevada is bound for the Pantex Plant in Amarillo, Texas, if it has not gone there already. The NNSA has refused to comment on the details of the shipping campaigns, citing national security concerns associated with transport of bomb-grade material.

Meanwhile, in a declaration that accompanied the NNSA’s Thursday filing, Nevada Field Office Manager Steve Lawrence said the agency would not shuttle any of the 1 metric ton of exiled plutonium between Texas and Nevada. Around August, as part of an environmental document called a supplement analysis, the NNSA said it might move the 1 ton of plutonium between the two sites.

The NNSA is shipping plutonium out of South Carolina after failing to turn the material into commercial reactor fuel using the now-canceled Mixed Oxide Fuel Fabrication Facility at the Savannah River Site. The 1 metric ton of plutonium at issue in Nevada’s lawsuit will by the mid-2020s be sent to the Los Alamos National Laboratory in New Mexico to be turned into plutonium pits suitable for use in intercontinental ballistic missile warheads. Los Alamos currently has no space to store the material, hence the sojourn in Nevada, the NNSA has said.

Nevada’s elected officials have been outraged about the shipment to their state since well before the NNSA admitted it happened. The outrage rolled on through this week, when the state’s congressional delegation met with NNSA officials about the shipment and came away with nothing more than a press release about how the agency lied to Nevadans.

“The Department of Energy has lied to Nevadans and their elected representatives for decades, and I have no reason to believe that will change,” Rep. Dina Titus (D-Nev.) said in a prepared statement after a classified briefing Thursday on Capitol Hill. Five NNSA officials including Administrator Lisa Gordon-Hagerty, plus two Department of Energy officials, met with five of Nevada’s six members of Congress.

Only the lone GOP member of the delegation, Rep. Mark Amodei (R-Nev.), sat out the meeting, according to a Titus spokesperson. The spokesperson said Titus had no further meetings planned with the NNSA, at deadline Friday for Nuclear Security & Deterrence Monitor.

On Thursday, Titus said she “learned nothing new” from the NNSA, and will “continue to work with Governor [Steve] Sisolak [D] and the Nevada Delegation to hold the [Department of Energy’s] feet to the fire and protect our state and its people.”