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Outline of Research
Nuclear energy is one of the most important energy resources for future energy security and environmental protection not only in Japan but also in the world. For the future long-term utilization of the nuclear energy, the development of light water reactors (LWR), fast breeder reactors (FBR), high temperature reactors (HTTR) and fusion reactors should be continued with various innovative idea. The reduction of high level radio-active waste from spent fuels of the reactors is also required to reduce environmental impact. Thus, it is necessary to develop accelerator-driven nuclear transmutation systems (ADS) for the back-end of nuclear fuel cycle.
We have investigated various interesting thermal-hydraulics, transport and corrosion phenomena extensively for the advancement of LWR, FBR, HTTR and ADS.
Present Researchs
1. Studies for Innovative Fast Reactors
Lead-bismuth eutectic (Pb-Bi) is superior to sodium as a coolant of fast reactor from the viewpoints of good neutronics and thermal-hydraulic properties and chemical inactiveness. Conceptual design and fundamental studies are performed for the development of a Pb-Bi cooed fast reactor shown in Fig. 1 as safe and economical future reactors.
1.1 Design Study of Innovative Fast Reactors
Design studies are performed for Pb-Bi-cooled small fast reactors that have high performance of thermal cycle efficiency, uranium utilization efficiency, and proliferation-resistance, and are safe and economical. The Pb-Bi-cooled fast reactors are also studied as the candidates of a MA transmutation reactor and the accelerator driven system (ADS).
1.2 Corrosion Test of Cladding and Structural Materials
Cladding and structural materials that are compatible with high temperature Pb-Bi are being developed. Candidates of corrosion-resistant materials are surface Al alloyed steels, high Cr steels that contain Al and Si, refractory metals, and ceramics such as SiC and SiC/SiC composites.
1.3 Chemical Test of Pb-Bi Coolant
Oxygen concentration in Pb-Bi coolant should be controlled adequately for formation of self-healed oxide film on the material for corrosion resistance. Thus, oxygen concentration control and monitoring technique is developed. For injection and/or leakage of steam into Pb-Bi, production and control of impurities in Pb-Bi and steam is studied.
1.4 Thermal-hydraulic Test
Innovative concept of elimination of primary pumps and steam generators are proposed as an economical reactor. Steam lift pump in chimneys above core is employed and its thermal-hydraulic performance is studied experimentally and analytically. Pb-Bi mists entrained from Pb-Bi free surface is removed in separators, dryers and electrostatic precipitators.
2. Li Technology for Fusion
Molten Li technology is studied for blanket breeder/coolant of fusion reactors. Magneto-hydrodynamic (MHD) characteristics of Li flow under strong magnetic field is investigated for reduction of MHD pressure drop.