A vast amount of research and development work has been done in recent years to resolve the issues of relevance to the safety of the Liquid Metal cooled Fast Breeder Reactor (lmfbr). Based on the results of this research as well as on the experience gained from the operation of test and prototypelmfbr’s, a certain consensus is emerging on the safety requirements of a modern sodium-cooled large fast power reactor. The paper reviews the fundamental physics and engineering aspects oflmfbr safety with reference to the Fast Breeder Test Reactor (fbtr) now being commissioned at Kalpakkam, and the proposed larger Prototype Fast Breeder Reactor (pfbr). The elements contributing to the inherent safety of fast reactors are recapitulated followed by description of the philosophy of the plant protection system and the use of engineered safeguards to enhance the safety. Finally, the principles used for the containment of radioactivity are discussed.

The role that could be played by liquid metal-cooled fast breeder reactors (LMFBRs) in the utilization of India’s considerable thorium resources is reviewed in this article. Distinct advantages of thorium-based fuels over plutonium-uranium fuels in LMFBRs pertain to a more favourable coolant voiding reactivity coefficient and better fuel element irradiation stability. The poorer breeding capability of thorium-fuelled fast reactors can in principle be overcome by improved core design and development of advanced fuel concepts. The technical feasibility of such advanced thorium fuels and core designs must be established by sustained research and development. It is also necessary to efficiently close the thorium fuel cycle of fast breeder reactors by appropriate development of the fuel reprocessing and refabrication stages. The Fast Breeder Test Reactor (FBTR) at Kalpakkam is expected to be an important tool for development of thorium fuel and fuel cycle technology. A quick look at the economics of the thorium cycle for fast reactors, vis-a-vis the more conventional uranium cycle indicates only a small and acceptable cost disadvantage on account of the need for remote fabrication of recycled thorium fuel.