WASHINGTON — The Trump administration is settling a long-running dispute with South Carolina over cleaning up weapons-grade plutonium stashed in the state.

The agreement is set to be announced Monday by Energy Secretary Dan Brouillette and South Carolina Attorney General Alan Wilson, said two people familiar with the matter who asked not to be identified because the deal hasn’t been formally unveiled.

Under the terms of the deal, the government will make an up-front payment to the state. In return, South Carolina will agree for several years not to pursue additional litigation on the matter. It wasn’t immediately clear how much the U.S. will be paying South Carolina under the deal, but it was described by the people as significant and the largest single settlement in the state’s history.

The development comes 17 years after the federal government first committed to clean up more than 11 million tons of radioactive material by 2016, or pay the state $100 million in penalties.

At issue is waste plutonium at a Cold War-era nuclear weapons manufacturing site near the Savannah River. The federal government initially planned to build a reprocessing facility and convert 34 metric tons of the material for re-use as fuel in nuclear power plants.

But in 2018, after the government spent years and some $8 billion of taxpayer money constructing the so-called Mixed Oxide Fuel Fabrication Facility, the Trump administration said it was canceling the project because it would be more cost effective to dilute and dispose of the plutonium than to reprocess it.

The settlement comes after a series of lawsuits by South Carolina over the stalled nuclear cleanup. In one suit filed three years ago, Wilson accused the federal government of trying to make South Carolina a “dumping ground” for plutonium.

The U.S. and South Carolina last month asked the U.S. Court of Appeals for the Federal Circuit to stay proceedings until Aug. 31, because they had entered into settlement negotiations.

Under the administration’s dilute-and-dispose plan for dealing with the plutonium waste, the radioactive material could ultimately be stored in other states. But it’s unclear how many other states would go along with that.

Already, the Energy Department has been forced to backtrack on a plan to put at least 1 metric ton of plutonium in Nevada, after a quiet shipment of some of the material from South Carolina sparked outrage there.

In a legal filing last year, Nevada’s attorney general accused the Energy Department of conducting a “secret plutonium smuggling operation” to send the state highly radioactive waste it didn’t want. Under a settlement agreement reached between Nevada and the Energy Department in June, the U.S. government committed to remove the 0.5 metric ton of plutonium it put in the state by the end of 2026, and won’t ship another batch it had planned to stash there.