[ASWnut101]

If they were releasing steam directly from the reactor itself would that contain trace elements of the internal elements of the reactor? I'm just pondering if they released steam and hydrogen from inside the reactor to prevent the buildup of a hydrogen bubble and it was the hydrogen released from the reactor that caused the explosion in the reactor hall.

Yeah, when the reactor pressure vessel gets above about 1100 bar, they have to open the safety relief valve or the pressure vessel will rupture. The steam loop in the reactor does contain trace, highly reactive BUT very short-lived (< ~3 minutes) radionuclides, so that would explain why they're talking about distributing KI pills to the local area.

A full-scale radioactive release of material on the scale of Chernobyl is not going to happen as long as the reactor core is submerged in water and pressure is released when needed. As far as I know, the Fukushima plant is an older design without all the safety features of modern BWRs, hence they are pumping s-tons of seawater into the core. Modern BWRs are designed to absolutely deluge the core (we're talking millions of gallons per hour) with water via a gravity-fed system.

Now, to my untrained eye, the explosion was 'shaped'. It clearly has an upward blast, with some lateral blasts. But not a lot of diagonal blast. My uneducated guess there is that it was an air-mix explosion, contained within the rectangular building. That would explain the shape and resultant destruction of the building. If it had been a core explosion, I would expect a more uniform shape? (Reactors are domes usually?). You can see the panels of the building flying off in specific directions.

Yeah, it was an explosion of the released hydrogen. From what I heard, it obliterated a building (the containment building, if I recall correctly), but the core is (as designed) unscathed inside the pressure vessel.

I always wondered if it really is a good idea to have around 60 nuclear plants in the one place on earth that tectonically is more active than any other region the world. Four continental plates meet below Japan.

It was just a question of time, I think.

I agree, but from what I can remember, the Fukushima plant was designed to withstand a Magnitude 8.0 earthquake. This 8.9 quake was nearly ten times as powerful as that, so the fact that the plant still stands [EDIT: Well, most of it anyway] is quite amazing I think. Also, all of the other plants in the area have safely scrammed their reactors and are operating without faults, so I would wager that the problems at Fukushima reflect the age of it's design.

Also, having a NPP near a huge body of water such as the ocean is actually a rather good idea, as you have a nearly inexhaustible supply of emergency coolant (as we are witnessing now) on hand.

I wonder how this will afect reactor designs in the fututre.... if this allows for a future for Nuclear reactors at all.

Probably will result in more redundant and reliable emergency cooling systems. Modern BWR designs are already nearly impossible to meltdown except under absurd circumstances (i.e. meteorite impact, direct nuclear strike, etc.) that would cause more problems than just a radiation leak.

Also, most supporting buildings and subsystems will be improved to help withstand large earthquakes and potential inundation by seawater.