Freezing and flow study of Wood's Metal in order to be used as water stopper material

The motivation of this study came from the decommissioning activities which are taking place in Fukushima Daiichi Nuclear Power Plants. Major corium removal plan is based on radiation shield by rising a water level inside the primary containment vessel after stopping water leak. Preliminary test showed the presence of numerous water leak points. Thus, a new technology is needed to stop the water leaks in strong radiation field for the decommissioning period. One of the candidate technologies can be using low melting point metal as sealing material. The advantage of this method is that it is easy to stop a leak point because the solidification of the liquid metal can be controlled by temperature. The candidate material is Wood Metal which has a melting point of 72.3 C. degrees and is an eutectic alloy of 48%Bi-26%Pb- 13%Sn-13%Cd. The melting point of Wood Metal is optimum for the injection in water and air environment. From the experiments it was concluded that a droplets injection is preferred for air environment. If it is not possible to have droplets injection it is recommended to have an injection in 2 or 3 steps. In this way each step will solidify and seal a part of the leak. The continuous injection appears ideal for most cases in water environment. Among the two environments, it was easier to obtain a good seal in water environment. However, a problem remain in the size of the leakage. In case of a big one, it is not possible for the liquid metal to solidify fast enough to stop it. A patch will be necessary before using this sealing method. The article is followed by the slides of the presentation