I. International and National Concepts on Future Thorium Based Nuclear Fuel Cycles in Comparison with Other Fuel Cycles

Brazilian systematic investigations on the use of thorium fuel cycles in nuclear power reactors started in 1965. During the 60's and early 70's the work was mainly concentrated on the thorium utilization in heavy water reactors (HWRs). This work was performed in the framework of a cooperation agreement with the, French CEA. In the frame of the International Nuclear Fuel Cycle program, Brazil started in 1979 an R&D program on the thorium utilization in pressurized water reactors (PWRs), within the scope of a Brazil-German cooperation agreement. This program lasted for almost ten years. The activities of both programs wore performed at the CDTN nuclear technology development center, in Belo Horizonte. More recently two Brazilian institutions restarted again investigations on the thorium fuel cycle. At CNEN, work is being pursued to further investigate the possible utilization of thorium in a PWR (Angra 1). The purpose of the paper is to comment briefly the main results of the past work and to give emphasis on the description of the recent results and new plans related to the work on thorium utilization in power reactors.