Design study of high breeding fast reactor

Aiming to increase fuel breeding capability as the most essential feature of fast breeders, an idea of the FP gas purge/tube-in-shell type metallic fuel assembly is proposed. It makes volume fraction of fuel high as more than 50% and realizes a very hard neutron spectrum in the core. The structure of the fuel assembly, its fabrication and the FP gas purging mechanism were assessed and it is clarified that the new concept of the fuel assembly is engineeringly feasible. FP gas purging does not affect shielding structure and can be managed by a small scale cover-gas treatment system because of good trapping characteristics of bonding sodium in the assembly as expected. The fuel handling system without forced cooling is possible. Other reactor components such as IHX were also evaluated. Thus, a concept of the total reactor system of a fast breeding reactor of 670 MWe with the ultra-high breeding ratio of 1.84 and the short reactor doubling time of 6.7 years was obtained. (author)