What are they doing?
TEPCO & Hitachi are apparently looking for damage to the vacuum breaker pipes that run in tandem above the downcomers to the torus inside unit 1. The handout before they did the actual work cited both the vacuum breakers and the location they found one leaking so they may have had other data that lead them to believe this was a problem.
Additional parts of the plan include using both the robots and the robot boat to look at penetration locations in the outer wall that faces the turbine building. They didn’t clarify why they were investigating those but it could be speculated they consider this a route of highly contaminated water or fuel debris to leave the building.
The new robots used to traverse the catwalk with telescoping camera arms were dropped in through a hole in the 1st floor down into the torus room. The location is …
Source: Fukushima Sub