Column electropulse

Hydroxjiamine is used as a substitute for the ferrous sulfamate (26). These systems are called salt-free flow sheets. The main purpose is to ease the problems associated with the processing and storage of the Hquid waste streams (27). Another approach is to use an electropulse column to electrolyticaHy produce to reduce Pu to Pu on a continuous basis (28,29). The half reactions for the flow sheets are... 

The development of in situ electrolytic methods by Allied Chemical resulted in a novel unit, the electropulse column, in which mass transfer and electrolytic reduction are carried out simultaneously (25). The basic feature of the electropulse column, (Fig. 3), is the dual function of the horizontal perforated plates, acting as cathodes as well as pulse plates, and the introduction of vertical anode screens contained in porous ceramic sleeves. This design was found particularly suitable for Pu-U partitioning, since it permits operation with an aqueous-continuous phase, which is needed to maintain adequate electrical conductivity, while the organic to aqueous flow ratio is kept quite large to obtain a high plutonium concentration in the exiting aqueous stream. 

The parallel electrolytic reduction developments at Karlsruhe appear to have concentrated initially more on the reduction of Pu and U in electrode-equipped mixer-settlers in which the reduction occurred largely in the settled aqueous phase rather than in a heterogeneous mixture. It was determined that a separating membrane may njt be necessary because of the redox potentials in the U - U5 - U6 system and the absence of gaseous products at the electrodes which could lead to explosive mixtures. A pulsed column, with internals quite different from those of Allied Chemical s electropulse column, was eventually developed and successfully tested (15,26) (Fig. 4). 

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)... 

In the Electropulse Column, plutonium reduction is achieved both through the redox reaction of plutonium(IV) with uranium(IV), produced electrolytically from uranium(VI) in the cathode chamber, and by direct reduction of the plutonium(IV) at the cathode. The basic reactions involved in the electro-lytic method are as follows ... 

Figure 2. 12.7-cm diameter electropulse column 1, diaphragm 2, cathode 3, anode 4, spacers 5, cathode bus bar 6, anode bus bar 7, cathode chamber 8, anode chamber 9, organic feed 10, organic effluent 11, aqueous feed 12, aqueous effluent 13, anolyte feed 14, anolyte effluent 15, air purge 16, air purge 17, 18, vent 19, thermocouple 20, pulse leg 21, control valve. 

With respect to the resultant data from uranium runs on both Electropulse Columns, the following correlation was derived for the uranium reduction efficiency ... 

The above equation was used for scale-up calculations and design of both the pilot plant and full-scale Electropulse Column. A total of 18 experimental runs for uranium(VI) electrolytic reduction was performed on the 20-cm diameter pilot-scale column. (10) As shown in Figure 4, the predicted reduction efficiency calculated from equation (4) correlated well with the experimental values obtained during these runs. The same good correlation between the predicted and experimental R(u) values was achieved later during cold uranium tests in the full-scale unit (Figure 4). The accuracy of correlation was within the range of 6%. 

The 2.54-cm diameter Electropulse Column shown in Figure 1, after completion of uranium runs, was installed at Battelle Memorial Institute (Columbus, Ohio) for uranium-plutonium partition tests. Six electrolytic runs were made under conditions corresponding to partitioning in the first process cycle to determine the effect of uranium reduction efficiency R(u) on t le separation process. The organic feed contained 80 to 83 grams/L of uranium and 0.71 to 0.82 grams/L of plutonium. The nitric acid concentration in the aqueous feed was 2.5 to 2.8 M and in the organic feed 0.2 to 0.3 M. 

FIGURE 5.12. Electropulse column cell for liquid/liquid systems. 

Dafana, R., 1987, The Design and Performance of a Novel Electropulse Column, Ph.D. dissertation, University of Newcastle upon Tyne, U.K. 

---