With President Donald Trump’s promise to “modernize and rebuild our nuclear arsenal,” his administration is moving to end Savannah River Site’s mission to convert surplus uranium and plutonium into fuel for commercial reactors — part of a long-term plan to rid the nuclear lab near Aiken of up to 34 metric tons of weapons-grade fissionable material.

Instead, the administration wants to dilute the radioactive matter with inert materials and bury it at the Waste Isolation Pilot Plant in New Mexico and start producing nuclear cores, or “pits,” at SRS. They’re the fissionable, grapefruit-size plutonium spheres that produce the chain reaction in a nuclear bomb.

At the same time, the administration is working toward reviving the Yucca Mountain project in Nevada as a means of providing the nation with a permanent nuclear waste repository.

So there are a lot of moving parts, and billions of dollars are at stake. Congress has the ultimate say in which way SRS goes, but the Pentagon and the Energy Department have made clear their intentions.

While parts of the overall plan may be palatable to Gov. Henry McMaster and South Carolina’s congressional delegation, which have supported SRS and its mission to ultimately rid the state of excess plutonium, converting SRS into a production plant for nuclear triggers is a hard sell.

The MOX facility is intended to turn weapons-grade plutonium into commercial fuel for nuclear reactors generating electricity, as part of a 2000 agreement with Russia. However, Russia has since withdrawn from the pact, and U.S. support for the MOX facility has declined.

Thousands of “pits” are already stockpiled and can be reprocessed for new bombs. The about-face at SRS has the potential to strand even more nuclear waste in South Carolina, where weapons-grade plutonium was shipped from Department of Defense sites around the country.

South Carolinians want to see SRS cleaned up.

Responding to the plan announced last week by the Pentagon and the Energy Department, Gov. McMaster vowed to fight the shutdown of the MOX facility.

“I will utilize all available options to protect South Carolina from becoming a permanent plutonium waste repository,” he wrote in a letter to the Energy Secretary Rick Perry.

Yes, converting SRS into a production facility for pits would save some jobs at SRS, but it would do little toward fulfilling the federal government’s promise to remove radioactive materials from the site.

The shift would, however, take some pressure off the Los Alamos National Laboratory in New Mexico, the only place where plutonium pits have been made since a Cold War-era plant in Colorado shut down. But Los Alamos hasn’t made any pits since producing 29 for Navy submarines in 2011 because the work there has been stalled by a series of safety lapses involving the handling of radioactive material. Safety violations have also slowed the completion of SRS’ MOX facility.

Under the plan endorsed by the Pentagon, SRS would start producing pits, eventually turning out 50 per year by 2030. Los Alamos would produce 30 per year.

Dealing with radioactive waste demands taking a long view. Gov. McMaster and the state’s congressional delegation should work toward a solution in which SRS can contribute to the nation’s defense, get cleaned up and reduce to a minimum the amount of dangerous nuclear waste stored there.