Andrew wrote:
In message , "dennis@home"
writes


"Bolted" wrote in message
...

The reactors shut down properly immediately the primary shockwaves
from the earthquake was
detected.

Properly? Doesn't seem to be working that properly now, unless you
really shut your eyes and ears and mind at tsunami +x hours (where x
varies by reactor).

They shut down, they would have gone critical a few minutes after the
tsunami if they had not.
The loss of cooling is the problem, it boils all the water out because
the decay side of things will be generating a couple of megawatts of
heat for weeks after shutdown.
Without cooling, the core melts, becomes compact enough to become
critical and the whole thing goes Chernobyl.
What they need to do now is hang onto the short half life stuff for as
long as possible to keep it away from people.
This is proving difficult as they are just pumping water through the
reactors and have run out of room to store it.
Normally they reuse the stuff so don't have storage problems.


Cooling is indeed the problem. One of the reactors (#4 I believe) had
had all its fuel removed for maintenance. All these fuel rods were in
the cooling ponds which seem to be right next to the containment vessel
and have boiled dry, due to the additional cooling required. In fact if
they are open-topped, the tsunami may have allowed salt water in which,
AFAIK reacts with the zirconium shields around the uranium and generates
hydrogen. The hydrogen explosions may also have cracked the cooling
ponds - they're keeping quiet about this.


no, the zirconium is quite capable of reacting with steam wirthout the
salt: that just makes it a bi easier that's all.


One of the reactors was burning mixed Plutonium/Uranium. I should think
the cooling pond full of that stuff is of most concern to them.



All reactors produce a certain amount of plutonium anyway. so its merely
a question of degrees.