Thermal cycle test of a full-scale graphite sleeve for use in the VHTR

A full-scale graphite sleeve which was made of the candidate graphite material IG-11 for a very high temperature gas-cooled reactor(VHTR), was tested by the application of a rapid heating and cooling to clarify its endurance for thermal shock. The graphite sleeve having inner diameter 36 mm, outer diameter 46 mm and length 550 mm was heated at an average heating rate of 80 0C per seconds to the maximum temperature of 2000 0C or 2200 0C and then the sleeve was cooled to 500 0C. The thermal cycle was repeated 500 in the case of the maximum temperature 2200 0C and 1000 in the case of 2000 0C. The dimensions, electric resistance and Young's modulus were measured at room temperature after the application of a fixed thermal cycle. The measurements were repeated at a fixed intervals. At the early stage of thermal cycle length expanded, electric resistance and Young's modulus decreased, and they were almost constant in the following thermal cycles. The results showed that the properties of the graphite sleeve were hardly changed due to the application of a rapid heating and cooling and its performance was almost unchamged. (author)