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MAVIC;
You're buying into the histrionics over the WORD "meltdown", not actually reading what it MEANS.
Have some fuel rods overheated, and probably begun to melt? Yes.
And their zirconium cladding is what created the hydrogen, not the fuel itself.
Is there a molten puddle of fuel at the bottom of the reactor pressure vessel? No. (or at least, there are no indications of that at this point).
EVEN IF all of the fuel WAS melted, and pooled in the bottom of the pressure vessel, it does NOT MEAN ANYTHING HAS ESCAPED THE PRESSURE VESSEL OR THE CONCRETE CONTAINMENT STRUCTURE AROUND IT.
There's enough trouble happening at the Fukushima plant without borrowing trouble.
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I found a post on a nuclear engineering forum with an event-by-event overview of reactor one...
Caveat: I haven't verified what "ANS" is or whether it's a good source...
ANS has put out a brief which describes events at Unit 1:
* The plant was immediately shut down (scrammed) when the earthquake first hit. The automatic power system worked.
* All external power to the station was lost when the sea water swept away the power lines.
* Diesel generators started to provide backup electrical power to the plant’s backup cooling system. The backup worked.
* The diesel generators ceased functioning after approximately one hour due to tsunami induced damage, reportedly to their fuel supply.
* An Isolation condenser was used to remove the decay heat from the shutdown reactor.
* Apparently the plant then experienced a small loss of coolant from the reactor.
* Reactor Core Isolation Cooling (RCIC) pumps, which operate on steam from the reactor, were used to replace reactor core water inventory, however, the battery-supplied control valves lost DC power after the prolonged use.
* DC power from batteries was consumed after approximately 8 hours.
* At that point, the plant experienced a complete blackout (no electric power at all).
* Hours passed as primary water inventory was lost and core degradation occurred (through some combination of zirconium oxidation and clad failure).
* Portable diesel generators were delivered to the plant site.
* AC power was restored allowing for a different backup pumping system to replace inventory inreactor pressure vessel (RPV).
* Pressure in the containment drywell rose as wet well became hotter.
* The Drywell containment was vented to outside reactor building which surrounds the containment.
* Hydrogen produced from zirconium oxidation was vented from the containment into the reactor building.
* Hydrogen in reactor building exploded causing it to collapse around the containment.
* The containment around the reactor and RPV were reported to be intact.
* The decision was made to inject seawater into the RPV to continue to the cooling process, another backup system that was designed into the plant from inception.
* Radioactivity releases from operator initiated venting appear to be decreasing.
And a reply post to from someone in the nuclear industry;
The reactor building for a BWR is nothing more than a thin weather protection building and all other components of major concern are within hardened structures within it.
Naturally, all of this needs verifying with "official" sources, and doesn't diminish the seriousness of the events..
But like I said before; there's no need to borrow trouble not in evidence!
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the pellets of poison are flooding the waters
