Patent Number: 050135198
Section: summary

BACKGROUND OF THE INVENTION This invention relates to a fast breeder reactor system capable of supplying a thermal/electrical output corresponding to the required scale. More particularly, the invention relates to an autonomous, decentralized fast breeder reactor system suited also to an underground site. Owing to the basic characterizing feature of a fast breeder reactor, namely the fact that fast neutrons are used in production of fission energy and in the breeding of fuel, the breeder has a dense core. Accordingly, in a larger scale power reactor, it is necessary to take a change in core reactivity into consideration in order to accumulate a larger volume of fuel within the core. In this connection, an inherent safety mechanism peculiar to fast breeder reactors is required. For example, since reactivity is controlled so as to be negative by a Doppler change or the like, core safety is maintained at a high level. However, in order to assure the reliability of these mechanisms, design limitations are imposed upon the core structure and control, etc. For example, a flat core structure, a structure which allows core expansion, or control for leveling core neutron flux is necessary. These limitations will not be solved merely by reducing the size of the core. There is a need to realize a universally applicable optimum nuclear reactor system in which rationalization of design is achieved based on a harmonious balance between safety and economy. SUMMARY OF THE INVENTION An object of the present invention is to provide an autonomous, decentralized fast breeder reactor system which operates in an autonomous manner while exhibiting a high degree of safety and reliability, and wherein scale of power can be varied easily in conformity with demand and application. In order to attain the foregoing object, the present invention provides an autonomous, decentralized fast breeder reactor system characterized in that a plurality of small-size nuclear reactor subsystems each having a small-scale faster breeder reactor core and a plurality of steam generator subsystems are disposed in a single main vessel of a nuclear reactor, and a heat transfer is made to take place between each nuclear reactor subsystem and each steam generator subsystem by a coolant circulating naturally through the interior of the main vessel of the nuclear reactor and undergoing a heat exchange with a coolant circulating naturally through the interior of each nuclear reactor subsystem. Other features and advantages of the present invention will be apparent from the following description taken in conjunction with the accompanying drawings, in which like reference characters designate the same or similar parts throughout the figures thereof.