CONPREHENSIVE STUDY ON THORIUM AS AN ENERGY SOURCE IN 21 CENTURY

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1. Design Study of Thorium Fuelled Reactors : (1) Nuclear data : The prompt fission neutron spectrum and the double differential neutron scattering cross section for thorium were measured. Experimental study on resonance interference between thorium and U-233 was attempted. We evaluated the nuclear data for U-232 and the result was incorporated in JENDL-3. (2) Reactor design : Conceptual design of a small molten salt reactor named FUJI was carried out. The characteristics of a HCPWR core and an inherent safe high flux reactor both with U-233 fuel were investigated. Production rate of actinidesin thorium fuelled reactors was compared with those in Uranium ones. (3) Excellent agreement was seen between the experimental and theoretical Keff values for thorium loaded cores at KUCA. (4) Preliminary experiment for a hydrid with thorium was carried out. (5) Significance of the thorium cycle in a quasi-equilibrium nuclear society was investigated.2. Fuel and Other Materials for Thorium Fuelled Reactors : (1) Non-stoichiometric study for thorium carbide was done. (2) We observed corrosion behavior of stainless steel by tellurium. (3) Chemical diffusion of oxygen in (Th, U)O_2 was investigated to show no dependence on lattice constants. (4) Production of (U, Th)O_2 powder by freezing method was experimentally studied. (5) We observed gamma ray spectra and isotopic ratios for irradiated thorium. (6) FP release from irradiated coated partic fuel was measured at 2300ﾟC. (7) We investigated the characteristics of molten fuel and structural materials for molten fuelled reactors. (8) Deposition phenomena of dissolved materials (CaCO_3 aq.) were experimentally obtained.