Hitachi GE conducted robot investigations into unit 2′s torus room on July 17th. The main focus of the work was to look at the pipe penetrations between the torus room wall and the turbine building. The swimming and also the crawling robots did the work together. It was noted that the layer of debris and sediment in the bottom of the torus room caused some problems when the robots kicked up that sediment. Other earlier torus room inspections found considerable layers of sediment on the torus room floors.
Tracer was used to see if the pipes between the torus room and the turbine building were leaking around the penetration seals. It didn’t appear to have any significant flow either direction. A more detailed set of work was documented on this inspection compared to unit 1. Here they explained the use of sonar to inspect the area. Images and a diagram below.
Source: Fukushima Sub