Here is an excellent article about BWR safety systems.

http://en.wikipedia.org/wiki/Boiling_water_reactor_safety_systems

The one thing that stood out was;



So all the discussion about the integrity of the core reactor vessel about whether the core is breached/degraded etc in the various reactor buildings is a mute point in terms of actual radiation release from this accident. None of the so called nuclear media experts have actually mentioned this and no one seems to asking what happened to reactor nos 1 and 3 spent fuel reactor ponds during those huge explosions. No one has even asked when each reactor was last refueled. For example if one the reactors was refueled in the last week or two there will be very little radiation release potential from the inner reactor containment vessel if breached (fissile byproducts) compared the 1 week old pulled fuel that was now being stored in the storage pool.

There is also very little discussion about the added dangers of the 7% Plutonium MOX fuel in reactor No 3.