Defense Waste Processing Facility Process Research Articles

Analysis of cesium extracting solvent using GCMS and HPLC

A high-level waste (HLW) remediation process scheduled to begin in 2007 at the Savannah River Site is the Modular Caustic Side Solvent Extraction (CSSX) Unit (MCU). The MCU will use a hydrocarbon solvent (diluent) containing a cesium extractant, a calix[4]arene compound, to extract radioactive cesium from caustic HLW. The resulting decontaminated HLW waste or raffinate will be processed into grout at the Saltstone Production Facility (SPF). The cesium containing CSSX stream will undergo washing with dilute nitric acid followed by stripping of the cesium nitrate into a very dilute nitric acid or the strip effluent stream and the CSSX solvent will be recycled. The Defense Waste Processing Facility (DWPF) will receive the strip effluent stream and immobilize the cesium into borosilicate glass. Excess CSSX solvent carryover from the MCU creates a potential flammability problem during DWPF processing. Bench-scale DWPF process testing was performed with simulated waste to determine the fate of the CSSX solvent components. A simple high performance liquid chromatography (HPLC) method was developed to identify the modifier (which is used to increase Cs extraction and extractant solubility) and extractant within the DWPF process. The diluent and triocytlamine (which is used to suppress impurity effect and ion-pair disassociation) were determined using gas chromatography mass spectroscopy (GCMS). To close the organic balance, two types of sample preparation methods were needed. One involved extracting aqueous samples with methylene chloride or hexane, and the second was capturing the off gas of the DWPF process using carbon tubes and rinsing the tubes with carbon disulfide for analysis. This paper addresses the development of the analytical methods and the bench-scale simulated waste study results.

Demonstration of the defense waste processing facility vitrification process for tank 42 radioactive sludge – melter feed preparation

AbstractThe Defense Waste Processing Facility (DWPF), at the Savannah River Site (SRS), is processing and immobilizing the radioactive high level waste sludge at SRS into a durable borosilicate glass for final geological disposal. The DWPF is currently processing the second, million gallon batch of radioactive sludge. This second batch is primarily from Tank 42. Each time a new batch of radioactive sludge is to be processed by the DWPF, the process flowsheet is to be tested and demonstrated to ensure an acceptable melter feed and glass can be made. This demonstration was completed in the Shielded Cells Facility in the Savannah River Technology Center at SRS.This paper presents the processing and offgas data, and compositional analyses obtained during the preparation of a melter feed for this demonstration. A second paper in this conference describes the properties of the glass produced from this feed. The demonstration used Tank 42 sludge slurry and the DWPF process control strategy for blending the sludge slurry with Frit 200 to make an acceptable melter feed. To prepare feed for the melter, the flowsheet requires that the radioactive sludge slurry be treated with nitric and formic acid to adjust rheology and remove mercury. During this step, hydrogen is formed from the decomposition of the formic acid. The acidified sludge slurry is then mixed with the prescribed amount of glass forming frit and evaporated to the proper weight percent solids to prepare feed to the melter. During this step hydrogen is also formed. Results indicate that the H2 generation rate is below the DWPF safety limits and an acceptable melter feed was produced.

Demonstration of the defense waste processing facility vitrification process for tank 42 radioactive sludge – glass preparation and characterization

AbstractThe Defense Waste Processing Facility (DWPF) at the Savannah River Site (SRS) is currently processing and immobilizing the radioactive high level waste sludge at SRS into a durable borosilicate glass for final geological disposal. The DWPF has recently finished processing the first radioactive sludge batch, and is ready for the second batch ofradioactive sludge. The second batch is primarily sludge from Tank 42. Before processing this batch in the DWPF, the DWPF process flowsheet has to be demonstrated with a sample of Tank 42 sludge to ensure that an acceptable melter feed and glass can be made. This demonstration was recently completed in the Shielded Cells Facility at SRS. An earlier paper in these proceedings described the sludge composition and processes necessary for producing an acceptable melter feed [1]. This paper describes the preparation and characterization of the glass from that demonstration. Results substantiate that Tank 42 sludge after mixing with the proper amount of glass forming frit (Frit 200) can be processed to make an acceptable glass.