Waste partitioning solutions

Mathur, J.N., Murali, M.S., Ruikar, RB. et al. 1998. Degradation, clean-up and reusability of octylphenyl-N,N-diisobutyl-carbamoylmethylphosphine oxide (CMPO) during partitioning of minor actinides from high level waste (HLW) solution. Sep. Sci. Technol. 33 (14) 2179-2196. 

The transmutation process requires partitioning, which inherently raises concern about the possibility of diversion or theft of sensitive nuclear materials. Both technical and institutional solutions to proliferation-resistance are sought for the on-site waste partitioning process. 

Transport processes carry wastes through the subsurface environment and must be considered in a fate assessment if the interaction of partition and transformation processes does not immobilize or alter the hazardous waste. Waste migration can take place either in solution or in solid form (particle migration). 

Precipitation usually occurs when the concentration of a compound in solution exceeds the equilibrium solubility, although slow reaction kinetics may result in supersaturated solutions. For organic wastes in the deep-well environment, precipitation is not generally a significant partitioning process in certain circumstances, however, it may need to be considered. For example, pentach-lorophenol precipitates out of solution when the solution has a pH of <5,35,36 and polychlorophenols form insoluble precipitates in water high in Mg2+ and Ca2+ ions.37 Also, organic anions react with such elements as Ca2+, Fe2+, and Al3+ to form slowly soluble to nearly insoluble compounds. 

Coprecipitation is a partitioning process whereby toxic heavy metals precipitate from the aqueous phase even if the equilibrium solubility has not been exceeded. This process occurs when heavy metals are incorporated into the structure of silicon, aluminum, and iron oxides when these latter compounds precipitate out of solution. Iron hydroxide collects more toxic heavy metals (chromium, nickel, arsenic, selenium, cadmium, and thorium) during precipitation than aluminum hydroxide.38 Coprecipitation is considered to effectively remove trace amounts of lead and chromium from solution in injected wastes at New Johnsonville, Tennessee.39 Coprecipitation with carbonate minerals may be an important mechanism for dealing with cobalt, lead, zinc, and cadmium. 

Aqueous biphasic systems offer the potential for highly selective and low-cost separations. Aqueous biphasic extraction for soil decontamination is based on the selective partitioning of either dissolved solutes or ultrafine particulates between two immiscible aqueous phases. Both soluble and particulate uranium contaminants can be separated from soil using this technique. Aqueous biphasic extraction may also have application for separation of plutonium and thorium from soil or waste. 

Evaporation of tue Lie.—The process of concentration is carried on in two different ways. Most commonly the solutions are evaporated and the residue calcined in tbo same reverberatory furnace, known as the white-ash furnace, whose extremo length should be about eighteen feet, and the breadth about nice feet. Its interior is linad with fire bricks, between which and the external masonry is placed a partition of sheet iron. Dy the application of heat in this manner, the evaporation proceeds rapidly, quietly, and at a very moderate expense of fuel. The waste heat from the black-ash ftrrnaees is frequently applied to tho evaporation of vat liquors. In this case, an iron pan tanned the mlting pan, in shape similar to tho furnace above-described, is placed at the end of the black-ash furnaco next to the raised bed, The evaporation proceeds rapidly as with the ordinary white-ash furnace but the mass of sah is not allowed to become completely dry. As soon as tho contents of the pan have attained... 

Mahajan, G.R. Prabhu, D.R. Manchanda, V.K. Badheka, L.P. Substituted malon-amides as extractants for partitioning of actinides from nuclear waste solutions, Waste Management 18 (1998) 125-133. 

A measured quantity of soil, sediment, or solid waste sample extracted with a measured volume of water, aqueous solution pH adjusted to >11 and serially extracted with methylene chloride pyridine partitions into the organic phase, which is then concentrated and analyzed as above. 

Ceramicrete stabilization of Tc, partitioned from high-level tank wastes, was demonstrated by Singh et al. [11]. The waste stream was a product of a complexation-elution process that separates Tc from HLW, such as supernatant from salt waste tanks at Hanford and Savannah River. A typical waste solution generated during the complexation-elution process contains 1 M NaOH, 1 M ethylenediamine, and 0.005 M Sn +. 

It is unavoidable to generate a stoichiometric amount of triorganotin-based waste, that often disturb isolation of the desired product because of low polarity and good solubihty in many organic solvents, in most of cases. Development of process to separate such a waste from the product is therefore one of the central issues in this protocol. Treatment of the reaction mixture with aqueous KF solution to precipitate polymeric trialkyltin fluoride is the most widely used procedure [22, 23, 80]. Partition between acetonitrile and pentane can effectively remove the tin waste and unreacted nonpolar organotin reagent if the desired product is polar enough [53]. Use of combinatorial technique may be one of recent solutions (see Sects. 4.7.2 and 4.7.3). Conventional and widely used procedures are nicely summarized in the review by Farina et al. [25,78,81 - 83]. 

The structure of the liquid column between the head of the piston and the tip orifice is shown schematically in Figure 3. The partition volume of pure DMSO is used for a prewash step prior to the wash step with DMSO system liquid. It is carried out by discarding the residual compound solution and the partition volume into waste after completion of each replication cycle. The 2-pL air gap (trailing air gap... 

So, it is expedient to separate them from the HLW that may be vitrified and incorporate these actinides into crystalline matrices (nuclear waste forms) or fabricate them into solid targets for transmutation in nuclear reactors or accelerators. There are a variety of processes for processing and partitioning the actinides - TRUEX (USA, Japan, Russia), DIAMEX (USA, Japan, EEC), TRPO (PRC), SANEX (USA, EEC, PRC), are under development [6]. The basic process in these technologies is extraction (or precipitation) of actinides from HLW solutions using special reagents. These methods provide for the separation of a high-actinide fraction or joint extraction of actinides, rare earths, and zirconium. The proportion of elemental concentrations in typical fractions is (in wt.%) actinides - 10-15, rare earths - 60-65, zirconium - 20-25 [7]. 

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