(12d) Defense Waste Processing Facility Flowsheet Studies with Simulants to Determine Solvent Build-up in Continuous Runs

The Actinide Removal Process (ARP) facility and the Modular Caustic Side Solvent Extraction Unit (MCU) are scheduled to begin processing salt waste at the Savannah River Site in fiscal year 2007. A portion of the streams generated in these salt processing facilities will be transferred to the Defense Waste Processing Facility (DWPF) to be incorporated in the glass matrix. Before the streams are introduced, a combination of impact analyses and research and development studies must be performed to quantify the impacts on DWPF processing. The Process Science & Engineering (PS&E) section of the Savannah River National Laboratory (SRNL) was requested to evaluate the impacts on DWPF processing.

Initial simulant Chemical Process Cell (CPC) flowsheet studies have indicated unacceptable levels of Isopar®L were collecting in the Sludge Receipt and Adjustment Tank (SRAT) condenser system and unanticipated quantities of modifier were carrying over into the SRAT condenser system. The second round of testing included the incorporation of the MCU stream and identified potential processing issues with the MCU solvent. 3,4 The identified issues included the potential carry-over and accumulation of the MCU solvent components in the CPC condensers and in the recycle stream to the Tank Farm. Solvent retention in the DWPF condensers contradicts the DWPF solvent control strategy. Therefore, DWPF requested SRNL to perform additional MCU flowsheet studies to better quantify the organic distribution in the CPC vessels.

A total of ten 4-liter SRAT runs were performed to meet the objectives of the testing. The first series of five tests evaluated the organic portioning and mass balance for the addition of 50 mg/kg solvent. The second series of five tests evaluated the organic portioning and mass balance for the addition of 125 mg/kg solvent. A solvent concentration of 50 mg/kg is close to the nominal concentration anticipated in the effluent from the Salt Waste Processing Facility (SWPF). All runs targeted 150% acid stoichiometry and 1% mercury in the sludge slurry dried solids. The results of this testing will be reported.