An experimental study on the local two phase distributions in the ERVC flow channel

During ex-vessel cooling two-phase flow around the outside of the inverted hemisphere geometry of the lower reactor head results in a variety void fraction distributions. To study the local features of the void fraction distribution we performed an experimental study with a quarter-circle geometry test section to simulate the RPV lower head. Air is injected in the test section to simulate the two phase flow phenomena and a conductivity probe is used to measure the local void fraction distribution. The test results show that the local void fraction near the bottom of the lower head is a wall peak distribution which then transitions to a near-wall peak distribution near the top of the lower head, and eventually develops into a center-peak distribution outside of the cylindrical shell. A sensitivity study has shown that the air flow rate has a significant effect on the local void fraction distribution in the flow channel. (author)