Hmmmm... Now that they have stated they believe the reactor containments have been breached, which was evident days ago from the detection of iodine according to a professor who said said today on NHK that the iodine could NOT have come from the pools, the big question is, from that professor, core or pipes and valves? I haven't heard evidence to demonstrate core breach and since the core steel containment is 200mm thick, I would think the pipe, valve (and flange o-ring gasket) scenarios are more likely.

In any case, if any of these components are breached, pumping cooling water could increase leakage. Now, how the hell can you change out valves? or seal cracked pipes if the pressure is high?

I have a terrible feeling that the fresh water and concrete pumper may have to be put to another use before this is over.

As for mg's comments on designing for the indeterminable, if engineers did that, nothing would get built. Only God can make a rock he can't lift.