The continuous pour of water for cooling is/has leached out most of the boron added to quench the emissions from the fuel rods in storage. The racks are unstable. A significant quake could collapse them into a pile with the possibility of going critical. It's just a matter of time as the site is too "hot" for humans to approach.
The Japanese seem to be on the cutting edge of robotics.
Kinda surprised they haven’t developed some sort of remote operated robot for this type of work.