Programm of research and development on the thorium utilization in PWRs

The major results of the Phase 1 (1979 - 1983) of the program ''Th-Utilization in PWRs'' are presented and discussed. The investigations show that the standard KWU-PWR can accomodate (Th,U)O2 and (Th,Pu)O2 fuel without changes in the fuel element design in 3 and 4-batch operation scheme without penalties in the reactor performance. An advanced fuel fabrication scheme using direct pellet pressing out of ex-gel microspheres has been developed on laboratory scale. The (Th,U)O2 test fuel produced satisfies PWR-specifications and is currently undergoing irradiation testing. Cold laboratory investigations indicate that the (Th,U)O2 PWR-fuel can be reprocessed using presently known technology including the chop-leach technique and modified Thorex extraction process. Based on the results of the Phase 1, recommendation for program continuation has been formulated. (orig.)