A leaking double-shell radioactive waste tank at the government’s Hanford, Wash., nuclear complex spawned questions Tuesday about the integrity of similar tanks at Savannah River Site.
Though both sites store large quantities of waste from Cold War nuclear weapons production, the leak at Hanford is not a predictor of new problems at SRS, said Terry Spears, the South Carolina site’s assistant manager for waste disposition.
“We do have double-shell tanks at SRS,” he told members of the SRS Citizens Advisory Board. “But because there were no design standards around Department of Energy sites, they were built at different times and with different designs.”
A 40-year-old tank at Hanford failed because of defective welds, he said, and the minor leakage involved material that seeped from the interior to the secondary wall.
“It was all contained inside,” he said.
Hanford’s 177 waste tanks include 28 double-shell tanks that store waste moved from single-wall tanks found to be leaking, according to the Tri-City Herald in Washington.
By comparison, SRS once had 51 underground tanks holding up to 1.3 million gallons apiece. Two were closed in the 1990s, and two more were closed this year.
Though some of the site’s single-wall tanks are leaking, no issues have surfaced with double-shell tanks at SRS, Spears said.
The recent tank closures included final approval from the South Carolina Department of Health and Environmental Control to clean up and close the remaining tanks. The next group of four closures is set for 2014-15, with remaining single-wall tanks closed by 2022. All closures are to be done by 2028.
The high-level waste in the tanks includes thick liquids, sludge with a consistency similar to peanut butter and a caustic material that turns to salt. The salt waste accounts for much of the volume, but the sludge is the most radioactive and much more dangerous. That material is sent to the Defense Waste Processing Facility at SRS, where it is “vitrified” in glass and sealed in steel canisters.