Recent trend of research and development of high conversion light water reactors

Accompanying the delay of the adoption of FBRs, the utilization of LWRs is expected to be made for long period. In order to deal with such situation, the development of the high conversion LWRs which can use natural uranium and reprocessed plutonium more efficiently is anticipated. In these HCLWRs, mixed oxide fuel is used, and the expected conversion ratio is 0.8 - 0.9 as compared with 0.55 in conventional LWRs, accordingly the rate of utilizing uranium resources is superior. Moreover, the HCLWRs have the characteristics which may be called plutonium storage reactor, consequently, they facilitate the flexible bridging from LWRs to FBRs. Accordingly, recently their development is positively advanced in various countries and research institutes. In Japan, Japan Atomic Energy Research Institute decided to begin the preliminary study of HCLWRs from fiscal year 1985, and the consultation on the research and development of HCLWRs for exchanging information has been advanced by the Government, JAERI and electric power and atomic energy industries. The reactor physics features of HCLWRs, the effect of hardening neutron spectra, the effect of using moderately enriched plutonium fuel, the relation between conversion ratio and other performance parameters, the present status of the research on the reactor physics by analytical and experimental methods are described. (Kako, I.)