Impact of Salt Waste Processing Facility Streams on the Nitric-Glycolic Flowsheet in the Chemical Processing Cell

Abstract

An evaluation of the previous Chemical Processing Cell (CPC) testing was performed to determine whether the planned concurrent operation, or "coupled" operations, of the Defense Waste Processing Facility (DWPF) with the Salt Waste Processing Facility (SWPF) has been adequately covered. Tests with the nitricglycolic acid flowsheet, which were both coupled and uncoupled with salt waste streams, included several tests that required extended boiling times. This report provides the evaluation of previous testing and the testing recommendation requested by Savannah River Remediation. The focus of the evaluation was impact on flammability in CPC vessels (i.e., hydrogen generation rate, SWPF solvent components, antifoam degradation products) and processing impacts (i.e., acid window, melter feed target, rheological properties, antifoam requirements, and chemical composition).Previous testing did not cover the expected Precipitate Reactor Feed Tank (PRFT) volumes or composition, so minor risks remain regarding the impact of material transferred from SWPF to the PRFT on CPC processing (foaming) and product rheology. This impact is independent of the CPC flowsheet used. The risk of not investigating representative PRFT compositions and volumes related to Sludge Receipt and Adjustment Tank (SRAT) chemistry is relatively minor because the monosodium titanate (MST) is largely inert within the CPC operations and the PRFT is processed prior to SRAT acid addition. The PRFT adds soluble components that change the required acid addition, but the impact to processing with the nitricglycolic flowsheet would be minor. The low hydrogen generation of the nitric-glycolic flowsheet is robust with respect to slurry salt content and excess acid addition.Previous testing covered the expected batch volumes of Strip Effluent Feed Tank (SEFT) material. The successful testing of the nitric-glycolic flowsheet simulating 18,000 gallons of SEFT material exceeded the expected maximum batch volume of 15,600 gallons of SEFT material. Additionally, portions of the testing with high batch volumes of SEFT also simulated DWPF boiling times through periods of boiling and simmering. The risk of increasing boiling time is also lessened by use of the nitric-glycolic acid flowsheet because glycolate does not decompose to the same degree as formate during later stages of boiling. Although nitric-glycolic flowsheet testing used the Next Generation Solvent (NGS) feeds in coupled testing, the chemistry impacts of testing with NGS feeds should bound those of the baseline solvent system.If SWPF integration takes place during Sludge Batch (SB) 9 and uses the nitric-glycolic flowsheet, no additional testing is necessary. The gaps in previous testing pertaining to PRFT volumes and composition, SEFT composition, and overall boiling time are relatively minor. The flowsheet testing already performed for SB9 is adequate technical process definition for integration with SWPF.Coupled testing should continue to be performed as part of future nitric-glycolic flowsheet simulan...