  Any water that flows into those buildings also becomes highly radioactive, as it is likely coming into contact with melted fuel.  Without knowing the extent of the current liquefaction and its location, the location of the melted fuel, how long TEPCO has been pumping out water, or when the next earthquake will hit, it is impossible to predict how soon this could occur from the water problem/subsidence issue alone. But undoubtedly, pumping water out of the buildings is just encouraging the flow, and this water problem needs to be remedied and redirected as soon as possible.  RT:Given all the complications that could arise with extracting the fuel rods, which are the most serious, in your opinion?  CC: The most serious complication would be anything that leads to a nuclear chain reaction. And as outlined above, there are many different ways this could occur. In a fuel pool containing damaged rods and racks, it could potentially start up on its own at anytime. TEPCO has been incredibly lucky that this hasn't happened so far.  