Characterization of Actinides in Simulated Alkaline Tank Waste Sludges and Leachates

Nash, Kenneth L.; Rao, Linfeng

doi:10.2172/839081

Cited by 1 publication

(2 citation statements)

References 5 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Further, selective dissolution of plutonium or uranium away from their poisons in the sludge (manganese and iron) could become a concern for downstream processing of the leachate, depending on the degree of dissolution, quantity, and isotopic distribution of materials involved. Dissolution of uranium and neptunium has been found to be non-negligible [Nash, et al, 2007]. Complexants that are present in some Hanford wastes can have significant impacts on actinide behavior during leaching, but these are generally soluble and are washed out prior to oxidative leaching.…”

Section: Status Of Randd Generalmentioning

confidence: 99%

“…Even without complexants, powerful oxidants can increase solubility of plutonium and americium in high hydroxide solutions. The different waste types have different performance However, the manganese (II) oxide formed during oxidative leaching seems to help control the solubility of the plutonium species [Nash et al, 2007]. Long term stability of these soluble species is unlikely in the absence of complexants or residual oxidizers, especially soluble forms of americium, although this behavior has only been minimally examined.…”

Section: Status Of Randd Generalmentioning

confidence: 99%

See 1 more Smart Citation

Aluminum and Chromium Leaching Workshop Whitepaper

McCabe¹,

Pike²,

Wilmarth³

2007

View full text Add to dashboard Cite

SummaryA workshop was held on January [23][24] 2007 to discuss the status of processes to leach constituents from High Level Waste (HLW) sludges at the Hanford and Savannah River Sites. The objective of the workshop was to examine the needs and requirements for the HLW flowsheet for each site, discuss the status of knowledge of the leaching processes, communicate the research plans, and identify opportunities for synergy to address knowledge gaps. The purpose of leaching of non-radioactive constituents from the sludge waste is to reduce the burden of material that must be vitrified in the HLW melter systems, resulting in reduced HLW glass waste volume, reduced disposal costs, shorter process schedules, and higher facility throughput rates. The leaching process is estimated to reduce the operating life cycle of SRS by seven years and decrease the number of HLW canisters to be disposed in the Repository by 1000 [Gillam et al., 2006]. Comparably at Hanford, the aluminum and chromium leaching processes are estimated to reduce the operating life cycle of the Waste Treatment Plant by 20 years and decrease the number of canisters to the Repository by 15,000 -30,000 [Gilbert, 2007]. These leaching processes will save the Department of Energy (DOE) billions of dollars in clean up and disposal costs.The primary constituents targeted for removal by leaching are aluminum and chromium. It is desirable to have some aluminum in glass to improve its durability; however, too much aluminum can increase the sludge viscosity, glass viscosity, and reduce overall process throughput. Chromium leaching is necessary to prevent formation of crystalline compounds in the glass, but is only needed at Hanford because of differences in the sludge waste chemistry at the two sites. Improving glass formulations to increase tolerance of aluminum and chromium is another approach to decrease HLW glass volume. It is likely that an optimum condition can be found by both performing leaching and improving formulations.Disposal of the resulting aluminum and chromium-rich streams are different at the two sites, with vitrification into Low Activity Waste (LAW) glass at Hanford, and solidification in Saltstone at SRS. Prior to disposal, the leachate solutions must be treated to remove radionuclides, resulting in increased operating costs and extended facility processing schedules. Interim storage of leachate can also add costs and delay tank closure. Recent projections at Hanford indicate that up to 40,000 metric tons of sodium would be needed to dissolve the aluminum and maintain it in solution, which nearly doubles the amount of sodium in the entire current waste tank inventory. This underscores the dramatic impact that the aluminum leaching can have on the entire system. A comprehensive view of leaching and the downstream impacts must therefore be considered prior to implementation.Many laboratory scale tests for aluminum and chromium dissolution have been run on Hanford wastes, with samples from 46 tanks tested. Three samples from SRS tanks have been ...

show abstract

Section: Status Of Randd Generalmentioning

confidence: 99%

Section: Status Of Randd Generalmentioning

confidence: 99%