D105 Study on temperature fluctuation phenomena in pressurizer spray pipe of pressurized water reactor

Gas liquid inter is formed in a pressurizer spray pipe of a pressurized water reactor when flow rate is small at normal reactor operation. Temperature fluctuation may occur it the interface moves periodically. Measurement of inner wall and fluid temperature in the test section simulating the real pressurizer spray pipe was conducted to study mechanism of the temperature fluctuation phenomena. Experiments with and without non-condensable gas, air were conducted. The significant temperature fluctuation was not observed in air-water system and air- vapor-water system. The temperature fluctuation was observed in vapor-water system. Visualization was carried out at the horizontal part of the spray pipe. No interface movement was observed but vortices in the liquid layer near the interface were observed without non-condensable gas. It was estimated that Kelvin-Helmholtz instabilities occurred in the liquid layer near the interface.