The Mark-IV (Mk-IV) is one of two electrolytic refining (electrorefining) vessels used in the electrometallurgical treatment of spent Experimental Breeder Reactor II (EBR-II) nuclear fuels at the Idaho National Laboratory Fuel Conditioning Facility. To meet the electrochemical separation parameters necessary for recovery of purified uranium in the Mk-IV, it is necessary to monitor and adjust the characteristics of the two phases present in the vessel: molten salt and liquid cadmium. Since the initial operation of the Mk-IV in 1996, the thickness of the cadmium layer has gradually increased as a byproduct of a chemical maintenance procedure used to adjust the electrolyte composition in the vessel. The current cadmium level is approaching the upper threshold for the process, and a level that is too high will inflict electrical shorting if cadmium contacts the purified uranium dendrites formed during electrorefining. To prevent this occurrence and maintain effective pyroprocessing, a pneumatic cadmium extraction system is designed within the unique constraints of the Mk-IV vessel. The design primarily considers portability and minimization of interruption to spent fuel treatment. The implementation of this apparatus and accompanying standard operating procedures will enable operators to remove and transfer liquid cadmium from the vessel when a decrease in level is needed. This system will be used to sustain the longevity of the Spent Fuel Treatment program at Idaho National Laboratory, an essential program for proper end-of-life disposal of spent EBR-II fuels as well as research into the applications of recovered uranium for future advanced nuclear reactor purposes.
