Compressive load effects on ultrasonic wave velocity propagating in graphite IG-110

Abstract

The High Temperature Gas-Cooled Reactor (HTGR) requires the use of the material as a core structure which is resistant to operating temperature reaching more than 500°C. The fine-grained isotropic graphites of IG-110 is a graphite material that has been applied to existing HTGR. The reactor core structure has a function to ensure reactor coolant flow, control rod movement, and reactor fuel conditions. In the implementation of reactor component inspections, various non- destructive test methods have been developed which aim to find cracks that are the initial failure of components. Besides, a non-destructive test method was also developed to measure the stress acting on the reactor components in order to determine the aging process. Currently, stress measurement is generally done indirectly using strain gage. The purpose of this study is to determine the effect of the load on ultrasonic wave velocity. Ultrasonic testing is carried out by using a portable ultrasonic flaw detector, using two types of waves, longitudinal wave and transverse wave, with a frequency of 5MHz. The stress acting on graphite material is compressive. The load was varied at several levels. The test results show that compressive stress in graphite material reduces ultrasonic wave propagation, for both types of waves used. The higher the compressive stress in the material, the more significant the decrease in ultrasonic wave propagation. The testing system used in this study has a level of measurement accuracy when the load value is higher than 20MPa.