Reprocessing/partitioning

New reprocessing (partitioning) techniques in which U and Pu are no longer separated as is the case in the traditional PUREX process (Section 10.5), and... 

Chemical Separation. A reprocessing facility typically utilizes multiple extraction/reextraction (stripping) cycles for the recovery and purification of uranium and plutonium. For example, a co-decontamination and partitioning cycle is followed by one or more cycles of uranium and plutonium purification. The basic process is illustrated in Figure 3. 

Fullwood, R. R. and R. R. Jackson, 1980, Partitioning-Transmutation Program Final Report VI Short Term Risk Analyis Reprocessing, Refabrication, and Transportation," ORNL/TM6986, and ORNL/Sub-80/31048/1. 

Early experimental work in electrorefining at Los Alamos by Mullins et-all ) demonstrated that americium could be partitioned between molten plutonium and a molten NaCl-KCl salt containing Pu+3 ions, and Knighton et-al(8), working at ANL on molten salt separation processes for fuel reprocessing, demonstrated that americium could be extracted from Mg-Zn-Pu-Am alloys with immiscible molten magnesium chloride salts. Work... 

Bond, W. Leuze, R. "Feasibility Studies of the Partitioning of Commercial High-Level Wastes Generated in Spent Nuclear Fuel Reprocessing Annual Progress Report for FY-1974," ORNL-5012, Oak Ridge, Tennesse, January 1975. 

Actinide chemistry involving soft donors and separation of Ans and Lns by tailor-made soft donors has been prevailing worldwide because its fruits are highly valuable in separation science and technology especially for the advanced reprocessing and partitioning. 

FIGURE 1.10 Classification scheme of separation processes developed and proposed for the reprocessing or partitioning. 

As a consequence, whereas NaN02 was employed for feed adjustment of the reprocessing solution in the earlier plants, N204 is being used increasingly for this purpose today. Similarly, in the partitioning cycle, U(IV) has replaced ferrous sulfamate. The... 

Uranous nitrate [U(N03)4] solution is used for the quantitative reduction of plutonium from loaded tributyl phosphate (TBP) phase [8]. Membrane cell technology was investigated for the production of 100% uranous nitrate solution [9], which is to be used in the partition cycle of the PUREX process in the fuel reprocessing plant. The membranes used hitherto have suffered from mechanical instability. A study was carried out at the BARC to obtain 100% uranous nitrate solution using a membrane-based electrolytic cell. The membrane used in this study was a thin polymer film reinforced with a Teflon fabric. The film was used as a separator between the anolyte and catholyte chambers, which are made of perfluorinated polymers, thus offering high thermal and chemical stability. 

During the past ten years, there has been considerable research devoted to the development of crystalline waste forms for actinide immobilization [7,8,24,27, 28,39,40,67,68,41-43,69]. Many of the phases are based on studies of minerals that contain Th and U, such as pyrochlore [16-18], zirconolite [70,71], zircon [1,72], monazite [73], britholite [74]. Based on their degrees of alteration, most of the minerals are considered to have an acceptable chemical durability. In addition, closely related mineral structures, such as murataite and garnet, which do not contain U or Th have been synthesized with actinides [29,75,76]. Multiphase ceramics. Ceramic matrices were initially designed for the immobilization of non-partitioned HLW from SNF reprocessing and considered... 

The second approach, which represents a departure from previous Pur ex partitioning, provides for the quantitative reduction of Pu to Pu3 with HAN and N Hlf (as the holding reductant) prior to the introduction of the U- and Pu-containing feed into a second cycle extraction column (Fig. 2). This method was proposed for both the EXXON reprocessing plant in Tennessee (10) and the ORNL Reprocessing Facility for LMFBR fuel (11). HAN will continue to be an attractive reductant because, not only is the introduction of metallic cations avoided, but HAN is decomposed safely by heating at temperatures above 60°C, which simplifies the reoxidation of Pu to Pu prior to subsequent extraction cycles. 

The location of the Pu-U partitioning step in Purex flow-sheets and the selection of specific operating variables (flow rates, concentrations, temperature) were generally determined by the type of fuel to be reprocessed, the subsequent waste management schemes, and the desired characteristics of the products. 

The Purex process will continue to be the main method for the reprocessing of nuclear reactor fuels. The inherent flexibility of this process allows for modifications needed to accomodate a large range of fuel compositions and product specifications. Among the several plutonium partitioning methods developed, those avoiding the introduction of extraneous metal ions... 

Cermak, A. F., and Spaunburgh, R. G., "Development of the Electropulse Column for Uranium-Plutonium Partitioning in the AGNS Reprocessing Plant," Paper presented at this Conf. (INDE 162). 

Development of the Electropulse Column for Uranium-Plutonium Partition in the AGNS Reprocessing Plant... 

In 1968, an electrolytic reduction process was proposed by A. Schneider and A. L. Ayers (6) to circumvent the above disadvantages. A research program was carried out in the Allied Chemical Corporation s laboratories during the years 1968 to 1972 to develop the process and equipment. The work resulted in the development of the Electropulse Column ( 7) for the continuous (differential) electrolytic uranium-plutonium partition process, which was later scaled up, fabricated, and installed in the Allied-General Nuclear Services reprocessing plant at Barnwell, South Carolina. About the same time, a stagewise electrolytic uranium-plutonium partition process was tested on a mini mixer-settler unit in Germany. (8)... 

Tedder, D. W., Finney, B. C., and Blomeke, J. 0., "Waste Treatment Facilities for the Partitioning of Actinides from LWR Reprocessing and Refabrication Plant Wastes,"... 

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