The strategic path toward the safest possible nuclear power plants is to switch to inherently safe nuclear reactors, capable of self-shielding, without interference by man, in any accident situations. Examples of such plants are modular medium and low-power plants based on fast reactors with a breeding ratio close to one. As a result, in such plants the operational reactivity margin is less than/~eff, negative temperature feedbacks are present, the void effect of reactivity is negative, and the colloant is a liquid metal whose aggregate state remains unchanged in the entire operating temperature range and at the temperatures reached during accidents. The physical properties of such reactors eliminate reactivity accidents with runaway on prompt neutrons and the chain reaction is self-quenched in any accident.Liquid-metal coolant, combined with the single-unit construction of the plant, implementing passive cooldown (when all other possibilities are precluded) through the reactor vessel to naturally circulating atmosphere air, will make it possible to avoid destructive overheating of the core. This concept is being implemented in the USA in the projects ALMAR (PRISM and others) and in Russia in lead-cooled reactors, which are being developed by the Scientific-Research and Design Institute of Energy and Fuels [1], and in designs with lead-bismuth coolant, which are being developed by the Institute of Physics and Power Engineering and the Special Design Office "Gidropress" [2]. Japan has also started the conceptual development of such lead-cooled plants.The transition to lead-bismuth liquid-metal coolant, which is inert with respect to water and air, makes the concept of an inherently safe fast reactor more complete than the ALMR concept, which is based on sodium as the coolant.Mastery of Lead-Bismuth Alloy as a Coolant. Russia was the first to use and has unique experience in assimilating and using this coolant in application to moving power plants. The scientific development was directed by the Institute of Physics and Power Engineering and the engineering development was directed by the Special Design Office "Gidropress" and the Special Design Office for Machines.Work on the application of the eutectic alloy lead-bismuth was started in this country at the initiative and under the leadership of A. I. Leipunskii in 1952. The fundamental problems arising in the development of a nuclear power plant with such a coolant, including the questions of heat transfer, hydrodynamics, coolant technology, corrosion, mass transfer, and many others, were solved. The required experimental base, equipped with unique test stands, was created. Commercial and prototype nuclear power plants, on which operation, repair, and refueling of the reactors were perfected and preliminary service-life tests of the equipment were performed, were constructed. The total service life of a nuclear power plant with lead-bismuth coolant was -80 reactor.years.During this work skilled teams of investigators, designers, and operating personnel, capable of ...

No abstract