From unit 3 where the pool is located:
http://www.cnn.com/2011/WORLD/asiapcf/03/21/japan.nuclear.reactors/index.html
It looks like Ed Storms may have been right.
I submitted his idea to Slate, by the way:
http://hive.slate.com/hive/averting-meltdowns/do-nothing-to-the-fuel-in-the-ponds-it-will-not-reach-criticality
(This only displays with Internet Explorer on my computer.)
QUOTE:
Do nothing to the fuel in the ponds -- it will not reach criticality
Submitted by Jed Rothwell
Friday, March 18, 2011
This is not my proposal at all. This is from Dr. E. Storms, retired from
Los Alamos, an expert in nuclear fuel. He wrote to me: Two kinds of fuel
are being used, uranium metal clad by zirconium (Unit, 1,2, and 4) and
UO2+PuO2 clad with zirconium (Unit 3). . . .
No one has endorsed this so it will not be forwarded from Slate to the
authorities. People here should endorse it.
- Jed