C-106 High-Level Waste Solids: Washing/Leaching and Solubility Versus Temperature Studies

Lumetta, Gregg J.; Bates, Derek; Berry, P. K.; Bramson, J. P.; P, Darnell, Lori; Farmer, O. T.; Greenwood, Lawrence R.; Hoopes, F. V.; RC, Lettau,; Piepel, G.F.; Soderquist, Chuck Z.; Steele, MJ; Steele, R. T.; Urie, MW; Wagner, J.J.

doi:10.2172/750395

Cited by 1 publication

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“…For the AN-102 sludge, aluminum, chromium, iron, manganese, nickel, and uranium metal concentrations all increased, but by no more than ~8%, at 50° C compared with the concentrations measured at 30° C . Again, however, hydroxide and plutonium concentrations were not measured, while sodium was about 6.0 M. In the tests with C-106 sludge, the sodium concentration was only ~0.63 M because of dilution using 0.1 M NaOH; the hydroxide and plutonium concentrations were not measured (Lumetta et al 2000a). Under these dilute conditions, chromium and nickel concentrations approximately tripled (but were so low at <5×10 -5 M as to be of no practical consequence) in raising the temperature from 30° C to 50° C and uranium concentration increased about 25%.…”

Section: Op6 -Temperature Changesmentioning

confidence: 89%

Effects Influencing Plutonium-Absorber Interactions and Distributions in Routine and Upset Waste Treatment Plant Operations

Delegard

Sinkov

Fiskum

2015

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Permanganate Effects -The solubilities of (hydr)oxide compounds of aluminum, cadmium, chromium, iron, and uranium (but not manganese and nickel), and of plutonium itself, increase with alkaline concentration and thus help preserve the plutonium/absorber ratio in solution. However, the ratio may be altered in permanganate oxidative dissolution of discrete plutonium phases such as PuO 2 ,PuO 2 •xH 2 O, or other low-solubility tetravalent plutonium because of oxidation to more soluble pentavalent or hexavalent plutonium. The ratio also may be altered because of oxidative leaching of Cr(III) phases while compounds of other absorber elements (e.g., aluminum, iron, nickel) are largely redox-indifferent. Plutonium dissolution from genuine washed sludge with permanganate is significantly enhanced by an increase in NaOH concentration, increasing by an average factor of 70 when permanganate oxidative leaching is undertaken at 3 M NaOH as compared with 0.1 or 0.25 M NaOH. The increase is likely due to plutonium being more readily oxidized to the more soluble hexavalent state. Dissolved plutonium species in alkaline solution, irrespective of oxidation state, are anionic so they are not expected to sorb onto the cation-sorbing resin used for 137 Cs removal. Indeed, such sorption is observed to be negligible. Excess permanganate does not appear to have an appreciable effect on the distribution of plutonium to solution based on oxidative leaching of REDOX Process sludge simulants and genuine Cr(III)-bearing Hanford tank sludges. In lab testing, intentional over-dosage of permanganate did not lead to enhanced plutonium leaching at lower alkalinity (0.09 to 0.25 M NaOH), while at higher alkalinity (3 M NaOH), the plutonium concentration increase to ~0.00036 g Pu/L was relatively low and could be mitigated by adding Cr(III) nitrate to the permanganate/manganate-bearing slurry to eliminate excess oxidant, form MnO 2 , and remove ~95% of the solubilized plutonium by coprecipitation. Separate testing showed that plutonium dissolution in the presence of excess permanganate at 2 to 4 M NaOH also can be mitigated by addition of hydrogen peroxide, removing ~75% of the solubilized plutonium. In treatment with Sr/Mn(VII) for 90 Sr and transuranic element removal from Envelope C supernates, both coprecipitated plutonium that remains undissolved and the residual soluble plutonium, should be protected with 100 to 1000 times higher neutron absorber concentrations based on AN-102 supernate studies. Although experimental data on 239 Pu decontamination from AN-107 supernates are lacking, it is likely that plutonium decontamination by Sr/Mn(VII) treatment was similar to that of AN-102 supernates based on solution composition and total alpha analyses. Decontamination of tank SY-101 from dissolved plutonium by permanganate treatment also is found. Overall, treatment of Envelope C wastes by Sr/Mn(VII) should improve criticality safety by carrying plutonium into the solid phase in the presence of co-precipitated iron and especially manganese.Cerium an...

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Section: Op6 -Temperature Changesmentioning

confidence: 89%