It will take at least three months longer than expected for a new salt waste treatment method at the Department of Energy’s Savannah River Site to complete a demonstration period that began in January.
That is because the method, known as tank closure cesium removal (TCCR), has had difficulties dissolving the salt waste, a DOE spokesperson said via email. The issue has pushed back the schedule for Savannah River Remediation (SRR), the liquid waste contractor at the 310-square-mile DOE facility in South Carolina.
The cesium removal method was expected to process a minimum of 600,000 gallons of radioactive waste in a nine-month demonstration period. Officials hope the demonstration will prove TCCR as a complement to the Salt Waste Processing Facility (SWPF), a larger-scale facility that is expected to begin operations in December.
It will now take until the end of the year, and possibly into 2020, to complete the demonstration, because the salt material has been found to be thick and dense, making it harder to process through TCCR. “The ability to effectively dissolve salt could result in additional delay. SRR is aggressively deploying other mechanisms to dissolve the salt waste,” the spokesperson said.
One of SRR’s methods to remedy the issue is installation of a recirculating system on the tank that stores the salt waste. The system mixes the waste with small amounts of water, making it easier to feed into TCCR. “Additional activities are being evaluated to promote efficient dissolution,” the spokesperson said, though she did not elaborate on what those activities might involve.
Savannah River houses about 35 million gallons of Cold War-era liquid waste, stored in more than 40 underground tanks. All told, the site’s liquid waste disposal mission is expected to run until 2039 and cost between $33 billion and $57 billion. It includes the treatment of liquid waste, cleaning and closing of the storage tanks, and deactivation and decommissioning of waste facilities.
About 90 percent of the waste volume is salt waste, which has been treated for years using a pilot process that also includes cesium removal. The Energy Department has pressed to increase treatment via TCCR and Salt Waste Processing Facility. The salt dissolution issue will not impact SWPF startup, the spokesperson said.
The Energy Department in July 2016 awarded Westinghouse Electric Co. $12.4 million to operate TCCR at the site’s tank farms. It is unclear how much was spent preparing the removal process for operations.
Equipment for TCCR includes two large enclosures that house exchange columns. Salt waste is transferred into the enclosures and passed through the columns, which filter out the cesium. The removal of cesium is key because its radioactivity makes it unfit for final disposition with the salt waste.
During the demonstration, waste from one Savannah River storage tank is undergoing the removal process. Once complete, the final solution of salt waste is taken to the Saltstone Production Facility for permanent disposal. Meanwhile, the cesium and the materials used to treat the waste are taken to a temporary location for close monitoring.
Since the Jan. 16 start date, TCCR has processed about 152,000 gallons of salt waste. That includes processing during Campaigns 1 and 2, with the first beginning on Jan. 16 and the second starting on Feb. 23 and slated to end later this month. It is unclear how much of that waste was processed during each campaign, but Campaign 2 is expected to process 65,000 total gallons.
The rest of the salt waste will be spread out among four other treatment campaigns over the demonstration period. At the end of the demonstration, the Energy Department and SRR will evaluate TCCR’s effectiveness and decide if the process should continue.
A similar cesium removal process is being implemented at DOE’s Hanford Site in Washington state. There, a Tank-Side Cesium Removal (TSCR) demonstration is expected to pretreat waste before the material is sent to Direct Feed Low-Activity Waste system at Hanford’s vitrification plant. That facility is to supposed to begin treating low-level waste as early as 2022.
