Partitioning high-level liquid

The INET annular centrifugal contactors are being used to partition high-level liquid waste so that the back end of the nuclear fuel cycle can be simplified. In particular, the TRPO process has been developed at INET for this application (Song, 2000), where TRPO is the extractant in the process solvent. Also known as Cyanex 923, TRPO is a trialkyl phosphine oxide that is made commercially by Cytec Industries (formerly American Cyanamid). It has a high affinity for the actinides. Further... 

Nigond, L. Musikas, C Cuillerdier, C. Solv. Extr. Ion Exch., 1994, 12, 297. Madic, C. Hudson, M. J. High Level Liquid Waste Partitioning by Means of Completely Incinerable Extractants, European Commission, Nuclear Science and Technology, EUR18038 EN 1998 p. 208. 

Madic, C., Hudson, C. 1998. High level liquid waste partitioning by means of completely incinerable extractants. EUR 18038 EN. European Commission on Nuclear Science and Technology, Luxembourg. 

Morita, Y., Yamaguchi, I., Fujiwara, T., Koizumi, H., Kubota, M. 1998. The first test of 4-group partitioning process with real high-level liquid waste at NUCEF. NUCEF 98 Symposium Working Group, November, Hitachinaka, Ibaraki, Japan. 

Madic, C., Blanc, P., Condamines, N., Baron, P., Berthon, L., Nicol, C., Pozo, C., Lecomte, M., Philippe, M., Masson, M., Hequet, C., Hudson, M.J. 1994. Actinide partitioning from high level liquid waste using the DIAMEX process. RECOD 94, April, London, UK. 

Hirano, H., Koma, K., Koyama, T. 2002. Waste minimization in actinides(IH)/ lanthanides(III) separation process from high-level liquid waste. 7th Information Exchange Meeting on Actinide and Fission Product Partitioning and Transmutation, October, Jeju, Republic of Korea. 

Tachimori, S., Ito, Y. 1979. Radiation damage of organic extractant in partitioning of high-level liquid waste, (I) Radiolysis of di(2-ethylhexyl)phosphoric acid by irradiation with cobalt-60 gamma rays. J. Nucl. Sci. Technol. 16(1) 49-56. 

Figure 1. The high-level liquid waste can he adequately partitioned hy solvent extraction with 30% CMP.

Nuclear fuel reprocessing and partitioning allow recycling of useful fissionable materials such as uranium and plutonium, and remove harmful long-lived minor actinides (americium and curium). It is necessary also for safety storage of high-level liquid wastes(l). In order to improve efficiency of mutual separation between lanthanide and actinide elements, design of useful extractants are requisite. 

During the decontamination steps, acid streams containing small amounts of actinides and fission products are produced. These streams are evaporated to concentrate the metal ions and recycle them. Nitric acid is recovered from the condensates and recycled. Excess HNO3 may be destroyed by formaldehyde. Fission product concentrates are routed to the aqueous raffinate of the first extractor of the partitioning cycle which contains > 99% of the FP. This constitutes the high level liquid waste (HLLW, or alternatively called HAW, high active waste). All other liquid wastes can be subdivided into intermediate level waste... 

Unfortunately, the dilute solution model is limited in its applicability to concentrated solutions. This causes problems for alloys such as Ni-based superalloys, high alloy steels, etc., and systems where elements partition strongly to the liquid and where solidification processes involve a high level of segregation. It is also not possible to combine dilute solution databases which have been assessed for different solvents. The solution to this problem is to use models which are applicable over the whole concentration range, some of which are described below. 

Clarity. In some soy processing plants, high levels of HI may partition with the lecithin gums on separation from the oil. This lipid-insoluble material can cause haziness in fluid lecithins. With modem miscella and oil filtration techniques, lecithins with very low HI contents can be produced. Consequently, modern lecithins are clear. Additionally, moisture can also contribute to lack of clarity. Generally, moisture levels over 1% can cause haziness. Besides being an aesthetic problem, if haziness is caused by HI material, it can result in sediment over time solid particles may appear on the bottom of an otherwise clear liquid product containing lecithin. 

High-pressure liquid chromatography (HPLC) allows the separation of soluble materials into component parts based on the partitioning of the materials between a mobile (solvent) and stationary (column packing) phase. With proper choice of solvent and column packing, separation of many types of materials is possible. HPLC has been used successfully to determine reagent residues on fabrics treated with durable press finishes as well as detennining formaldehyde levels in aqueous solutions obtained by the AATCC Test Method 112. ... 

The proportion of total soil iodine partitioning into the liquid phase of a soil is often considered to be low due to high levels of adsorption onto solid-phase components. For example, Johnson (1980) analyzed 183 soil samples from the United Kingdom and found that water-extractable values could be <0.1mg-kg representing <0.1% of total soil iodine. However, the full range of values for this set of soil samples extended to 13.6mg-kg in the liquid phase, equivalent to around 25% of total iodine. Similarly, Hou et al (2003) found that readily available (the most environmentally mobile) I (water-soluble and exchangeable fractions) accounted for around 20% of total I in Chernobyl soil and around 10% of total I in Irish Sea sediment (Figure 11.2). Therefore, appreciable quantities of iodine... 

Ansari, S.A., Mohapatra, P.K., Raut, D.R., Seshagiri, T.K., Rajeswari, B., and Manchanda, V.K. 2009. Performance of actinide partitioning extractants in hollow fiber supported liquid membrane for the transport of actinides and lanthanides from high level nuclear waste. J. Membr. Sci. 337 304-309. 

Because of the anion complexation observed in the solid state, it was proposed that cyclo[8]pyrrole could function as an anion extractant, specifically for sulfate. Sulfate receptors that can act as extractants of this ion are highly desirable because sulfate is a problematic species in the vitrification process that is proposed for the disposal of certain radioactive wastes. The original reported short-chained forms of cyclo[8]pyrrole presented solubility issues, but a newer derivative, octamethyl-octaundecylcyclo[8]pyrrole, 2b, originally developed as a precursor for liquid crystals, proved to be amenable to extraction studies. It was found that 2b was able to selectively extract sulfate in the presence of high levels of nitrate. This cyclo[8]pyrrole was thus able to overcome the so-called Hofmeister bias or the inherent propensity for nitrate to partition before sulfate. While the kinetics are slow—reducing utility in the context of near-term applications—this is the first example where this level of selectivity is seen in a sulfate versus nitrate extraction experiment. ... 

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