Operation, test, research and development of the High Temperature Engineering Test Reactor (HTTR) (FY2024)

Department of HTTR

This report summarizes the activities carried out in the fiscal year 2024 about the operation and maintenance of the High Temperature Engineering Test Reactor (HTTR), the R&Ds using the HTTR and so on. The HTTR is the first Japanese test reactor of High Temperature Gas-cooled Reactor (HTGR) type with 30MW in thermal power and whose maximum outlet coolant temperature achieved 950C. HTGRs are regarded as the promising candidates of the Next Generation Nuclear Plants conformed to the future decarbonized society because of the inherent safety characteristics as well as high temperature heat supply capability for not only power generation but for wide-ranging industrial uses such as hydrogen production and so on. The HTTR achieved its reactor outlet coolant temperature of 950C under full thermal power of 30MW on April 19, 2004. And since then, HTTR has had a lot of experience of HTGRs' operation and maintenance throughout rated power operations, safety demonstration tests, long-term high temperature operations and demonstration tests relevant to HTGRs' R&Ds. In the fiscal year 2024, we conducted heat load variation tests simulating heat load fluctuations due to equipment abnormalities at thermal utilization facilities (hydrogen production facilities) planned to be connected to HTTR, as well as radioactive iodine quantitative evaluation tests to assess the amount of radioactive iodine deposited in the pipes, assuming a primary double-pipe high temperature gas duct rupture accident of the HTGR. Additionally, to confirm hydrogen production technology using the high-temperature gas reactor, we applied to Nuclear Regulation Authority for a reactor installation change permit to connect a hydrogen production facility to HTTR.