Temperature Measurement of Control Rod Using Melt Wire in High-Temperature Engineering Test Reactor (HTTR)

At the time of a reactor scram, the control rods are inserted into the high-temperature reactor core, where they are exposed to a thermal load. When a high-temperature engineering test reactor （ HTTR ） is constructed, the control rod temperature is evaluated conservatively because there is no way to accurately measure the actual temperature. In this study, to measure the temperature of the control rods in an HTTR, we installed a “melt wire” made of alloys with various melting points in the tips of the control rods. After experiencing a reactor scram at 100 ％ power, the melt wires were in-spected visually. The melt wires clearly showed a molten state. The result of the visual inspection claritied that the highest temperature reached at the tip of the control rods was in the range of 505 to 651 ℃ . The temperature measurement technique established by this study will lead to the improved accuracy of temperature estimation by design calculation and structural integrity assessment of the components in an HTTR.