Uranium thorium partition cycle

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... 

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. 

In the Acid-Thorex process, fluoride ion should be added to the thorium partitioning solution (1BX) to decrease thorium transfer to the uranium stripping column, particularly where highly radioactive feeds are used. This fluoride ion addition then decreases the precipitation of thorium-DBP in the uranium stripping column. Also, the partition cycle should be the first cycle in the Acid-Thorex process to allow separation of thorium from DBP. 

Codecontamination and partition cycle. Because the codecontamination and partition cycle is the critical step in the acid Thorex process, it will be described in more detail. In this cycle, shown in Fig. 10.21, most of the fission products were separated from the uranium and thorium, which were then separated from each other. The four solvent extraction units, HA, IBX, IBS, and 1C, were pulse columns with dimensions given in the figure. 

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... 

In the solvent extraction step thorium and uranium are co-extracted in the first cycle subsequent partitioning of thorium and uranium in the second cycle gives two decontaminating cycles to both products while using only five columns. For short-decayed thorium a reductant, sodium hydrogen sulfite, is continuously added to the feed streams of both cycles to decrease the effect of nitrite formed by irradiation. Without the sulfite addition, the nitrite formed by radiation decomposition of nitrates converts ruthenium to a solvent-extractable form. Acid deficiency in the second cycle feed is achieved by adding dibasic aluminum nitrate (diban). 

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