Re: For Your Information
- From: "daestrom" <daestrom@xxxxxxxxxxxxxxxxxxxxxxxx>
- Date: Wed, 21 Sep 2005 02:16:23 GMT
"Chris" <nimbo@(no-spam)ukonline.co.uk> wrote in message
news:3UiXe.42170$k22.23057@xxxxxxxxxxxxxxxxxxxxxxxxxxxx
> Chris.
>
> Thorium can be made into a fissile material by neutron irradiation. This
> new element, I think it is Uranium 233 can be used as a fissile material.
>
> Plutonium in a pile rather than in a bomb can be used to supply thermal
> neutrons if a moderator is used. Plutonium in created from Neutron
> irradiation in a Uranium Pile by thermal neutrons using a graphite
> moderator.
>
> Uranium 238 (non fissile)> Plutonium 239 (fissile) by neutron absorbtion.
> Thorium 232 (non Fissile)> Uranium 233 (fissile) by neutron absorbtion.
> So India's invention is possible and probably true. Naturally occuring
> Uranium contains isotopes 235 and 238 in significant quantities. The U
> isotope 235 will break into two approximately equal parts if struck by a
> fast neutron and by itself with a significant half life. When this
> happens about three fast neutrons are released. These three fast neutrons
> will collide with another U235 or be lost to the system It appears that
> isotopes with even numbers are more stable than odd numbers, this has to
> do with pairing of fermions.
>
> If pure U 235 is in a chunk there will be a spontanious disintegration
> rate. If the neutrons on average escape before hitting a U235 then there
> will be no explosion.
>
> If the U235 is in the form of a sphere there will be a mean free path of
> any neutron starting somewhere inside and if that mean free path is
> smaller than the radius of the sphere there will be an uncontrolled chain
> reaction building up exponentially in about 100 mSec until all the U235
> has been split. The energy released is the diffrerence in atomic mass of
> the U235 and the sum of the two atomic mases created. This may be found
> from tables, but the split is not the same each time and there is a spread
> of products.
>
Actually, some of your nuclear physics is faulty. Uranium 238 can fission
if bombarded with a fast neutron. But the probability is small compared
with the probability that the neutron will be absorbed and a beta particle
emitted forming Plutonium-239. That is why U-239 makes a poor bomb
material. Plutonium-239 will fission readily if bombarded with a fast
neutron. This is why Plutonium-239 is preferred for bomb-making.
U-235 prefers to absorb thermal energy neutrons. Power reactors are
designed to thermalize (i.e. slow down) a large percentage of the neutrons
released from fission so that they can sustain the chain reaction. One
method of control used is to reduce the amount of moderating material in the
reactor so that fast neutrons escape from the reactor before being
thermalized. But yes, U-235 can also fission by absorbing fast neutrons.
But the neutron probabilities are much lower, requiring more material and/or
neutrons.
Even it the 'best design', only a tiny fraction of the fissile material is
actually fissioned during an explosion. The energy released as the
fissioning starts is so great that it literally blows the remaining bomb
material apart. One early bomb improvement was to increase the amount of
time that the material is contained before it blows itself apart. By
keeping the bomb together for just fractions of a msec longer, many more
fission events occur, raising the total energy yield.
daestrom
.
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