Reprocessing technology in the HTGR fuel cycle

Extensive R and D work has been carried out in the Federal Republic of Germany since 1967 to develop the technology necessary for closing the fuel cycle of high-temperature gas-cooled reactors (HTGRs). The efforts are concentrated primarily on fuel elements with either highly enriched 235U or recycled 233U as the fissile material and thorium as the fertile material embedded in a graphite matrix. They include the development of processes and equipment for reprocessing and remote preparation of coated microspheres from the recovered uranium. The paper reviews the issues and problems associated with the need to deal with high-burnup fuel from HTGRs of different design and composition. It is anticipated that a grind-burn-leach head-end treatment and a modified Thorex-type chemical processing are the optimum choice for the flowsheet. An overview of the present status in construction of Jupiter, a small reprocessing facility, is presented. It includes a discussion of problems already solved and still to be solved, such as the treatment of feed/breed particle systems and for minimizing environmental impacts envisaged with a HTGR fuel cycle technology. Also discussed is the present status of remote fuel kernel fabrication and coating technology. Additional activities include the design of Venus, a mock-up prototype burning head-end facility, with a throughput equivalent to about 6000MW installed electrical power, as well as a preliminary study for the utilization of the Karlsruhe LWR prototype reprocessing plant (WAK) to handle HTGR fuel after remodelling of the installations. The paper concludes with an outline of prospects for the future. (author)