Development of temperature measurement technology for control rod using melt wire in High Temperature engineering Test Reactor (HTTR)

Hamamoto, Shimpei  ; Sawahata, Hiroaki ; Suzuki, Hisashi; Ishii, Toshiaki ; Yanagida, Yoshinori

A melt wire was installed at the tip of the control rod in order to measure the temperature of High Temperature engineering Test Reactor (HTTR). After experience with reactor scram from the state of reactor power 100%, the melt wire was taken out from the control rod and appearance has been observed visually. In this study, an exclusive device for taking out the melt wire was prepared. The take-out device functions as expected, and the melt wire was safely and reliably taken out using a remote manipulator. And because the visual observation of the melt wire was clearly carried out, we were successful in developing the control rod temperature measurement technology. It was confirmed that the melt wires with a melting point of 505C or less were melted, and the melt wires with a melting point of 651C or more were not melted. Therefore, it was found that the highest arrival temperature of tip of the control rods where the melt wires are installed reaches within the range of 505 to 651C. And it was found that the control rod temperature at the time of reactor scram does not exceed the using temperature criteria (900C) of Alloy 800H of the control rod sleeve.