On Mar 21, 2011, at 1:57 PM, [email protected] wrote:
In reply to Horace Heffner's message of Mon, 21 Mar 2011 11:31:30
-0800:
Hi,
[snip]
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.
..don't forget the earthquake. There is no guarantee that things
are where they
were put.
Yes.
The wisdom of storing fuel rod assemblies in such a near-critical
geometry that neutron absorbers are required is highly questionable,
especially in an earthquake prone area. Also, it is now obvious that
a removable cover, capable of preventing storage tank coolant loss
due to sloshing, might be of use.
It seems possible to design a storage facility, possibly enveloping
and storing one assembly at a time, that uses a passive cooling
capability, possibly involving heat pipes and air cooling. Possibly
storage of encased assemblies within a pond below local water table
levels would work, so as to obtain emergency cooling water
automatically, without pumps or power, if the pond level drops.
It seems to me one of the biggest problems now is the involvement of
so many fuel containing components at Fukushima, any one of which
could force permanent evacuation of the plant. The combined
probability of none of them causing a serious problem is thus low,
much lower than for any one component. Upon a prolonged forced
evacuation, every component not having coolant will then become
problematic, due to loss of all coolant. It thus seems now is the
time, if it is not too late, to stabilize as much as possible the
fuel storage for prolonged situations in which there is no water.
The fuel storage has about 75% of the onsite fuel. Hopefully the
steel reactor containment will reduce the material released to the
air from the reactors if the plant is abandoned.
Best regards,
Horace Heffner
http://www.mtaonline.net/~hheffner/
