On Mar 21, 2011, at 11:47 AM, Edmund Storms wrote:
Horace, rather than make suggestions based on speculation, why not
use facts?
1. Uranium fuel, if it does not melt, will remain in the geometry
that is known not to go critical.
Not true. The uranium does not have to melt to form a new geometry.
At three mile island the fuel did not melt - it rubblized. This
involves a change in geometry. It also fortunately involved the
control rods in the rubble. In the case of the storage pools, much
more fuel is stored than in the reactors. Further, it is stored in a
geometry that is designed to save space. If it rubblizes into a much
smaller volume at the bottom of the pool then determining
theoretically if a critical mass can be created involves some
serious computation. It is also notable that a chain reaction does
not have to occur for meltdown to occur. Ordinary decay can drive a
meltdown, the formation of corium. See:
http://en.wikipedia.org/wiki/Corium_(nuclear_reactor)
In any case, like Chernobyl, the storage pools are not in a steel
containment, so the products will be released to the atmosphere, as
you know. Unlike Chernobyl, MOX fuel, which contains more plutonium,
is being used in reactor 3. Further, all the MOX fuel was not loaded,
some new fuel is still in the storage pool.
2. Uranium that gets hot enough to melt will react with the air and
more rapidly with water to produce powdered U3O8. It will not form
a liquid.
In the case of metallic uranium in the fuel rods it could form a melt
with the Zr cladding at about 2000°C. I doubt if any such fuel rods
are actually located at Fukushima. I think the fuel rods for GE
designed boiling water rectors use uranium oxide fuel pellets, which
melt at 2865°C.
3. The powdered U3O8 will not go critical because it contains too
much oxygen and because it will deposit as a powder all over
everything.
This depends on the geometry and content of the rubble or slag formed
at the bottom of the storage pool, if such happens.
4. Addition of water will accelerate this process, make the fuel
even hotter, and spread the powdered U3O8 as a slurry.
The opposite seems to have happened so far. When water is restored
things stabilize momentarily. This is buying time for a more
permanent solution, though the time bought is undoubtedly very small.
Have you ever actually used uranium?
The above is an irrelevant argument. I haven't piloted a luxury
liner cruise ship, yet I know you can't dock under full steam. A
suggestion is just a suggestion. I see no harm in having a point of
view. Once suggestions are available, they need to be scrutinized
for pros and con. In any case, the authorities in charge will do
that. It is not clear any authorities will actually know of or
consider anything written here in this off-ramp off-road backwoods of
scientific discussion.
Ed
On Mar 21, 2011, at 1:31 PM, Horace Heffner wrote:
On Mar 21, 2011, at 7:57 AM, Jed Rothwell wrote:
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
This could be an incredibly bad suggestion. It depends on whether
neutron absorber slabs were actually placed between *all* fuel
assembly storage positions. It is my recollection that storage
pools did not have neutron absorber slabs when originally
constructed decades ago because there was no intent to store for
long periods. Separation geometry alone was used to prevent
criticality. When storage pools began to run out of room, the
unused portions of storage pools were later modified to
accommodate closer storage by adding neutron absorber slabs
between fuel assemblies, and storing them closer together.
If the neutron absorbers can burn, decompose or rubblize at lower
temperatures than the fuel rod assemblies, then even they probably
will not prevent criticality in the volumes in which they exist.
If there are volumes where they do not exist then it is essential
to fill those volumes with a solid which will prevent critical
mass, either by preserving the geometry or by absorbing neutrons.
It seems to me that one key thing to do immediately is to locate a
number of neutron counters in the vicinity of each pool. This
could be done by lowering an asbestos insulated cable with one or
more neutron counters on it through the roof by crane, or to lower
a water cooled metal pipe with neutron counters located within it
through the roof.
Time is of the essence. Putting water on the storage pools seems
to have provided some calm for a while, just no permanent
solution. Here is an alternate suggestion to not putting water on
the storage:
http://www.mail-archive.com/[email protected]/msg43699.html
Best regards,
Horace Heffner
http://www.mtaonline.net/~hheffner/
Best regards,
Horace Heffner
http://www.mtaonline.net/~hheffner/
