Long-term high-temperature operation of the HTTR

Abstract

The high temperature engineering test reactor (HTTR) constructed at the Oarai Research and Development Center of the Japan Atomic Energy Agency (JAEA) is the first high-temperature gas-cooled reactor (HTGR) in Japan. The HTTR is a graphite-moderated and helium-gas-cooled reactor. The reactor thermal power is 30MW, and the reactor maximum outlet coolant temperature is 850°C in rated operation mode and 950°C in high-temperature test operation mode. The main objectives of the HTTR are to establish and develop HTGR technology and to demonstrate process heat application.The HTTR was operated for 30days in rated operation mode and 50days in high-temperature operation mode to obtain various characteristic data for HTGRs. The main test results are as follows:(1)The coated fuel particles (CFPs) of the HTTR are excellent at confining the fission product and have the highest performance in the world.(2)The measured temperature of the core internals is in good agreement with the design value, which means that they will maintain their structural integrity.(3)The intermediate heat exchanger maintains excellent heat transfer performance from the beginning of operation.In addition, the following two issues were validated using the HTTR burnup data: (1) the effectiveness of rod-type burnable poisons at reactivity control in the HTTR and (2) the whole core burnup calculation method for the nuclear characteristics of the HTTR.