PIV measurements in the vicinity of a steam sparger in the PANDA facility

To study the thermal behaviour, e.g. the stratification build-up and the homogenization, steam is injected through a sparger into a large pool containing 45m3 of water in the PANDA facility; a scenario which could take place in the wetwell of a BWR in the case of a postulated accident. Depending on the steam flow rates vented in the wetwell two regimes can develop in the water pool (i) a thermal stratification build-up and (ii) thermal mixing or homogenization. If thermal stratification build-up occurs, the temperature of the upper part of the water pool is much higher than the bottom of the pool which would decrease the rate at which steam condenses since the heat sink capability of the pool decreases. Conversely if mixing occurs the pool temperature remains homogeneous throughout the pool and provides a higher heat sink capability for steam condensation.