The Savannah River Site’s Defense Waste Processing Facility (DWPF) should produce 300 canisters of treated sludge waste per year once the Salt Waste Processing Facility (SWPF) comes online later in 2019.
That would be significantly higher than the 136 canisters produced in fiscal 2016, the 52 in fiscal 2017, and 18 in the last fiscal year that ended on Oct. 1. The latter two years were lower than the site’s usual 100-plus target because of a 15-month outage, among other issues at the facility.
Since 1996, the DWPF has treated sludge waste stored in underground tanks at SRS by mixing it with a sand-like borosilicate glass that converts it into a less radioactive form. Once operational, the SWPF will break down the millions of gallons of salt waste stored in these Cold War-era vessels by removing harmful components of the waste.
Salt and sludge waste must be treated in sync with each other because the liquid waste system, which includes 40-plus underground waste storage tanks and the two treatment facilities, functions as an integrated system, Jim Folk, the assistant manager for waste disposition at Savannah River, said via email last week.
For years, DWPF has worked in sync in with a pilot process that treats salt waste by a means similar to planned operation of the Salt Waste Processing Facility. Once operational, the salt waste facility will tie-in to the rest of the liquid waste system, including DWPF, the pilot salt waste equipment, the storage tanks, and the facilities that store waste after processing.
All of this is why sludge and salt waste have to be processed in sync with each other, Folk said.
An example, he added, is the March 2016 decision to scale back the amount of the sludge waste being treated. That is because the Defense Waste Processing Facility, which handles sludge waste, was experiencing infrastructure issues. These included annual outages for routine maintenance and the replacement of a DWPF melter, which also stalled liquid waste processing. The melter mixes the waste with the glass material to remove contamination.
“This set of circumstances created uncertainty in the amount of salt and sludge that would be available to send (for processing),” Folk said. “Therefore, scaling back operation to focus on optimizing production while simultaneously preparing for SWPF startup was appropriate.”
Salt waste accounts for 90 percent of the 35 million gallons of the liquid waste stored in the tanks at the DOE complex near the city of Aiken, the result of nuclear weapons production during the Cold War. While work continues to ready SWPF for operations, the site has been using a pilot facility to process salt waste by breaking down its components into less radioactive forms. The treated material is stored permanently on-site.
Meanwhile, sludge waste, which accounts for the other 10 percent, is converted at the DWPF into a glassy form through a process called vitrification. The final product is stored on-site temporarily until the federal government decides on a permanent repository.
The Defense Waste Processing Facility is expected to produce 8,000 canisters in its lifetime, including the 4,179 canisters generated since operations began in 1996. To date, that equates to 16.2 million pounds of treated waste.
Usually, the site aims to produce 100 to 110 canisters of sludge waste per year through DWPF operations. But that should change once the salt waste facility becomes operational. Delays have pushed the target startup date to December 2019.
Once SWPF is online, overall liquid waste processing at Savannah River – which includes sludge and salt – should jump from 1.5 million gallons annually to 6 million.
Those figures also assume continued salt waste processing via the pilot process and the recent startup of the tank closure cesium removal (TCCR) mission, which treats salt waste in a similar fashion. If all of this falls in line with no major setbacks, “the liquid waste system will be operating at, or above, historical levels,” Folk wrote.
Overall, the SRS liquid waste mission is expected to last until 2039 and carries a life-cycle cost of $33 billion to $57 billion.
