The states have known for years that this day would come. But because of political opposition, environmental fears and cost concerns, most of them have done almost nothing to construct new landfills in the meantime.
At issue is the Barnwell County dump site, a 235-acre expanse that opened in 1971 close to the Georgia line. The equivalent of more than 40 tractor-trailers full of radioactive trash from 39 states was buried there each year before South Carolina lawmakers in 2000 ordered the place to scale back because they no longer wanted the state to be the nation's dumping ground.
As of July 1, the landfill will take waste only from South Carolina and the two states with which it formed a partnership, New Jersey and Connecticut.
State and industry officials say the not-in-my-backyard resistance will ironically lead to "temporary" storage sites in backyards across the nation.
"I'm concerned about it, that my hospitals in my neighborhood will have to store this stuff on site," said Rita Houskie, administrator for disposal of the waste in Arkansas, Kansas, Louisiana and Oklahoma. Other states affected by the shutdown include California, New York, Illinois, Florida and Texas.
The danger, some officials say, is that storing the waste in potentially hundreds of locations across the country could allow radiation to escape.
While none of the trash could be used to make a nuclear bomb, some experts fear it could be stolen to make "dirty bombs," which use conventional explosives to scatter radioactive debris.
"As a matter of national security, health and safety, it makes good sense to ultimately dispose of this stuff and not just store it all over the country," said Rick Jacobi, a nuclear engineer and former general manager of the Texas Low-Level Radioactive Waste Disposal Authority.
"There will be hundreds, maybe thousands of them. People won't want to pay others to store the material. They'll find a closet or warehouse or a shed out back and stick it in there and see what happens."
The trash sent to Barnwell includes protective clothing and gloves, tools, cleaning rags, lab equipment, industrial measuring devices and equipment used to treat cancer patients. It does not include spent fuel from nuclear power plants. The waste is stored in steel containers that are put in concrete vaults and then buried in long trenches.
Most waste from hospitals, universities and power plants falls into the lowest-hazard class, which means it decays to nonradioactive levels within 100 years.
The closing of Barnwell will mean roughly 20,000 cubic feet of trash per year, or enough to fill six tractor-trailers, will be turned away.
Only two other landfills now exist nationwide for low-level nuclear waste.
One, in Clive, Utah, takes only the least hazardous trash, such as slightly contaminated clothing. It accepts waste from all states. The other landfill, in Richland, Wash., receives such material along with hotter waste that decays to non-hazardous levels within 500 years. But it accepts shipments from only 11 states, including Idaho, Nevada and Colorado.