(528e) Innovative Idea to Accelerate Tank Closure in Doe Savannah River Site

Treatment and disposition of salt waste is the critical path to completion of Savannah River Site (SRS) Liquid Waste (LW) Disposition Program. The Salt Waste Processing Facility (SWPF) is the integral part of the overall strategy to complete the SRS tank waste mission to process ~35 Mgal of radioactive salt waste. Some old-style tanks are with known leak sites. Schedule delay for the SWPF project has placed a significant challenge to meet tank closure commitments at SRS in Aiken, South Carolina.

 Actinide Removal Process (ARP) and Modular Caustic Side Cesium Extraction Unit (MCU), interim salt processing facilities, were constructed in 2008 to bridge the crucial period before startup of SWPF.  Current process is to transfer a batch of 3715gal salt solution to a tank, strike the salt batch with MST to absorb actinides. The MST-stricken batch is then transferred to a tank to filter out solids. The filtrate, Clarified Salt Solution (CSS) is then fed to MCU to remove cesium. The filtering process is one of bottlenecks and it requires time consuming chemical cleaning steps once every 20 filtering batches.   The need to increase ARP/MCU throughput to beyond design basis rate becomes more pressing.  The current cycle time for qualifying a one million gallon batch of salt waste for Waste Acceptance Criteria (WAC) program, on average, is about 3 month and 1 week.  To take advantage of the WAC idle time, the “Large Tank Strike” project is proposed.   By adding MST strike to the 1 million gallon batch instead of 3715 gallon mini-batch during the WAC cycle time period while waiting for WAC qualification lab result, a bulk of solids is expected to settle below the pump suction head of Tank 21.  Based on the Particle Settling Rate Calculations (Henley, E.A., Yueng, M.R., 2014), more than 90% of solids are expected to settle out during the 3 months and 1 week WAC cycle time period. The upper CSS solution is transferred to a tank and to be filtering through existing primary and secondary filtration systems. With much lowered solid loadings, it is expected the downtime and filter cleaning time frequency will be significantly less. The project is critical for DOE to mitigate impacts to FAA tank closure dates resulting from SWPF construction delays.