Partitioning flowsheets

A primary objective of the DOE program has been to develop actinide partitioning flowsheets that are defensible from the standpoint of chemical feasibility. A four-point strategy was adopted in order to meet this objective ... 

From a computational viewpoint, the presence of recycle streams is one of the impediments in the sequential solution of a flowsheeting problem. Without recycle streams, the flow of information would proceed in a forward direction, and the cal-culational sequence for the modules could easily be determined from the precedence order analysis outlined earlier. With recycle streams present, large groups of modules have to be solved simultaneously, defeating the concept of a sequential solution module by module. For example, in Figure 15.8, you cannot make a material balance on the reactor without knowing the information in stream S6, but you have to carry out the computations for the cooler module first to evaluate S6, which in turn depends on the separator module, which in turn depends on the reactor module. Partitioning identifies those collections of modules that have to be solved simultaneously (termed maximal cyclical subsystems, loops, or irreducible nets). 

In the acid deficient flowsheet the acid released from A1(N03)3 hydrolysis was neutralized to give an organic product containing 0.5 M U02(N03)2 but only 0.05 M HN03. The A1(N03)3, Na2Cr207 and FPs were retained in the aqueous raffinate from the extraction section, while the organic product was passed to the U/Pu partition contacter. 

More recently a flowsheet has been developed which employs 30% TBP/OK as the solvent.349-446 447 This involves the use of an acid feed to the first cycle to assist in zirconium decontamination and suppress hydrolysis. An acid-deficient partition cycle then follows in which the U-Th separation is effected. A pilot plant (JUPITER) has been constructed at Julich in Germany to process Th02/U02 fuel using this flowsheet. Although a complete separation of thorium, uranium and FPs is possible using TBP in the Thorex process,448 alternative approaches... 

FIGURE 3.24 SETFICS process flowsheet tested by JNC on an inactive surrogate PUREX raffinate. (Courtesy of Hirano, H., Koma, K., Koyama, T., 7th Information Exchange Meeting on Actinide and Fission Product Partitioning and Transmutation, October 2002, Jeju, Republic of Korea.)... 

Filippov, E.A., Ruzin, L.I., Mamakin, I.V. Development of complex flowsheet of HLW partitioning by solvents on the base of crown ethers and polyorganophosphazenes in heavy diluent. In Khol kin, A.I. Ed., Khimiya i tekhnologiya ekstraktsii (Extraction Chemistry and Technology), Vol. 2. Moscow, 2001, pp. 50-63. (In Russian.)... 

Partitioning of the flowsheet into recycle loop nets. 

Bruns, L. E. "Plutonium - Uranium Partitioning by a Reflux Extraction Flowsheet," in "Proceedings, ISEC 71," Society of Chemical Industry, London, 1971, Vol. 1, p. 186. 

To obtain a solution for the material and energy balances in a flowsheet by the sequential modular method, you must partition the flowsheet, select tear streams, nest the computations, and thus determine the computation sequence. 

The Purex Process has been used either with "early" or with "late" Pu-U partitioning (Fig. 1). The early split in the first cycle avoids the co-stripping of uranium and plutonium which may result in higher plutonium losses. In other flowsheets, the partitioning is delayed until the second cycle. While no particular trend has been obvious, some of the recent flowsheets in which the plutonium is reduced prior to re-extraction (10,11) will necessarily require a second cycle partitioning. 

The partition cycle columns were operated on flowsheet values and then a DBP solution was pumped to the extraction feed point in increasing amounts. The thorium content of the uranium product stream from the thorium partition column was monitored. The runs were then repeated using increasing increments of fluoride in the thorium partition solution and the thorium content again monitored in the uranium product from the partition column. 

Early solvent extraction flowsheets for HTGR fuels recycle developed at the General Atomic Company contained a coextraction costrip cycle for thorium and uranium prior to the partitioning... 

---