Feasibility study on a wide-variety of fuel utilization by using HTTR, 4; Study on thorium fuel utilization

Ueta, Shohei   ; Goto, Minoru  ; Katayama, Masaharu*; Takagi, Naoyuki*; Ooka, Yasunori*; Yamasaki, Masatoshi*

For the feasibility study on a wide-variety of fuel utilization of the high temperature gas-cooled reactor (HTGR) in order to confirm the integrity and the irradiation performance of thorium as the fuel, the irradiation test with thorium-uranium mixed dioxide fuel (denoted as thorium fuel) by the High temperature engineering test reactor (HTTR) of Japan Atomic Energy Agency (JAEA) has been reviewed, and its neutronic characteristics has been evaluated. With regard to the license, the HTTR and the fuel fabrication plant of Nuclear Fuel Industries, Ltd. have been permitted to treat thorium as the fuel. During the irradiation, the integrity of the fuel specimen can be monitored continuously by the fuel failure detection (FFD) system installed in the HTTR. After the irradiation, the fuel sample is dismantled from the core and post-irradiation examinations are carried out to confirm the integrity and to evaluate the irradiance of the test fuel. The irradiance of the thorium fuel sample have been estimated in case of the irradiation test with three block of the thorium fuel in 4 of thorium to uranium mixed ratio and in 20% of enrichment of uranium-235. As the result, the burnup of the thorium fuel specimens will be approximately 21 GWd/t with 30 MW of reactor power in 660 days of the irradiation duration.