HB-Line Dissolution of Glovebox Floor Sweepings
- Westinghouse Savannah River Company, AIKEN, SC (United States)
Two candidate flowsheets for dissolving glovebox floor sweepings in the HB-Line Phase I geometrically favorable dissolver have been developed.Dissolving conditions tested and modified during the laboratory program were based on the current processing scheme for dissolving high-fired Pu-238 oxide in HB-Line. Subsequent adjustments made to the HB-Line flowsheet reflected differences in the dissolution behavior between high-fired Pu-238 oxide and the MgO sand/PuF{sub 4}/PuO{sub 2} mixture in glovebox floor sweepings. Although both candidate flowsheets involved two separate dissolving steps and resulted incomplete dissolution of all solids, the one selected for use in HB-Line will require fewer processing operations and resembles the initial flowsheet proposed for dissolving sand, slag, and crucible material in F-Canyon dissolvers. Complete dissolution of glovebox floor sweepings was accomplished in the laboratory by initially dissolving between 55 and 65{degree} in a 14 molar nitric acid solution. Under these conditions, partial dissolution of PuF{sub 4} and complete dissolution of PuO{sub 2} and MgO sand were achieved in less than one hour. The presence of free fluoride in solution,uncomplexed by aluminum, was necessary for complete dissolution of the PuO{sub 2}.The remaining PuF{sub 4} dissolved following addition of aluminum nitrate nonahydrate (ANN) to complex the fluoride and heating between 75 and 85{degree}C for an additional hour. Precipitation of magnesium and/or aluminum nitrates could occur before, during, and after transfer of product solutions. Both dilution and/or product solution temperature controls may be necessary to prevent precipitation of these salts. Corrosion of the dissolver should not be an issue during these dissolving operations. Corrosion is minimized when dissolving at 55-65{degree}C for one to three hours at a maximum uncomplexed free fluoride concentration of 0.07 molar and by dissolving at 75-85{degree}C at a one to one aluminum to fluoride mole ratio for another one to three hours.Generation of hydrogen caused by the dissolution of calcium metal should also not be a concern.No hydrogen was detected in the laboratory off-gas stream and insignificant metals of any kind are present in glovebox floor sweepings. Glovebox floor sweepings are generated at Savannah River in FB-Line during preparation of the feed material used in the metal producing bomb reduction process. It is usually after precipitation and during drying or conversion of plutonium fluoride to a PuF{sub 4}-PuO{sub 2} mixture at 500{degree}C, that spil occur which can contaminate the converted cake with varying amounts of MgO sand or other glovebox materials. This contaminated converted cake mixture of PuF{sub 4} and PuO{sub 2} is packaged and stored in the vault fo eventual recovery of the plutonium.In the past, most recovery operations in HB-Line have dealt with PuO{sub 2} as the only plutonium compound present in the material to be dissolved. However,since the plutonium in FB-Line glovebox floor sweepings is a mixture of plutonium fluoride (PuF{sub 4}) and plutonium oxide (PuO{sub 2}), the standar HB-Line dissolving flowsheet is not directly suitable for complete dissolution.This is because it is difficult to completely dissolve PuO{sub 2} when the fluoride is complexed with aluminum and it is difficult to completely dissolve PuF{sub 4} unless sufficient aluminum is present to complex free fluoride. These observations were previously confirmed during the initial flowsheet development work for dissolving sand, slag, and crucible materials in F-Canyon dissolvers.
- Research Organization:
- Savannah River Site (SRS), Aiken, SC (United States)
- Sponsoring Organization:
- USDOE, Washington, DC (United States)
- DOE Contract Number:
- AC09-96SR18500
- OSTI ID:
- 644591
- Report Number(s):
- WSRC-TR-98-00029; ON: DE98052825; TRN: 98:009473
- Resource Relation:
- Other Information: PBD: Feb 1998
- Country of Publication:
- United States
- Language:
- English
Similar Records
DISSOLUTION OF NEPTUNIUM OXIDE RESIDUES
DISSOLUTION OF 3013-DE SAMPLE 10-16