Re: UNUSED URANIUM, PLUTONIUM, etc.
From: N:dlzc D:aol T:com \(dlzc\) (net_at_nospam.com)
Date: 07/16/04
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Date: Fri, 16 Jul 2004 07:29:33 -0700
Dear puppet_sock@hotmail.com:
<puppet_sock@hotmail.com> wrote in message
news:c7976c46.0407160610.67207046@posting.google.com...
> "N:dlzc D:aol T:com \(dlzc\)" <N: dlzc1 D:cox T:net@nospam.com> wrote in
message news:<erIJc.2536$Wv4.1832@okepread03>...
> [snip]
> > The first time plutonium was tested as fuel in a nuclear reactor, they
did
> > not jacket it in any other material. As plutonium goes from "room
> > temperature" to "operating temperature" it goes through six different
> > atomic structures. After a few cycles, the fuel rod had changed
dimensions
> > by up to 600%, and could not be removed from the core, without severe
> > disassembly (involving some cutting, as I heard it told). I understand
> > they package it in Zirconium now... ;>)
>
> That's a good fairy story. Now tell us the one where pink unicorns
> bring the dew in the morning.
They are green, by the way. ;>P
> Plutonium was part of the fuel cycle of the very first reactor ever
> built, and part of all Uranium reactors. It gets produced during the
> normal operation of the reactor. That's where we get Plutonium. A
> non-trivial portion of the energy released is produced by reactions
> involving Plutonium.
I was referring to concentrated plutonium as a fuel source, not
spontaneously produced in a matrix of U-238.
> Metalic Plutonium does not go through "six different atomic structures"
> in heating to normal temperatures in a reactor. And it certainly does
> not expand any 600 percent. (Interesting confluence of 6's there.)
I will refer you to:
URL:http://www.lanl.gov/source/orgs/nmt/nmtdo/AQarchive/97-98winter/metallurgy.html
... paragraph starting off:
<QUOTE>
Plutonium is, as a metal of the actinide group, active in nearly every way.
The pure metal has six allotropes
<END QUOTE>
I loosely called them "atomic structures" for this context, and I learned
them as "phase changes".
As to the confluence of 6's, I would likely agree with you. A 600% change
in a single dimension would, depending on reactor design, be a physical
impossibility.
> Metalic forms of fuel are not the usual form of reactor fuel.
I wonder why they decided not to do this? Could it be they found out
"somehow", perhaps divine inspiration, that there were problems?
> This is because hot Plutonium has this nasty habit of sucking oxygen
> out of water. So does Uranium. So they don't use metalic forms in
> most designs. (A few do, but those are usually research systems with
> very special purposes.)
The early ones, the research ones, did not have the fuel immersed in water.
> Plutonium oxide, the usual form of fuel, is a ceramic. So is Uranium
> oxide. These are usually jacketed in some alloy of zirconium in order
> to give them strength, and to deal with the fact that the ceramic is
> brittle. It is fairly usual for oxide reactor fuel to crack during
> normal operation. In the oxide form, these materials are quite stable
> until they start to get close to their melting point. (I spent a very
> tedious couple weeks a few years ago, typing in the data for
> measurements of the change of density, thermal capacity, and thermal
> conductivity of these oxides, as a function of temperture, oxygen
> content, and isotopic content. Then I used half that data to build
> a computer subroutine to predict these quantities, and the other half
> to validate the code.)
>
> It's truly amazing how stories get picked up and inflated in the
> nuclear biz. As an example, some few years ago, at one of the nukes
> in Ontario, a tech left a tool in a fuel channel. The tool was a
> sort of round file, and it's name was a "plumber's weasel." At some
> later time, the channel was inspected, and this tool was discovered.
> The story was passed around and mutated until people were claiming
> that herds of dead rats had been found in a fuel channel.
>
> There really is no need or value in passing such unsubstantiated
> rumours. There's enough interest in nuclear physics without adding
> a lot of fairy stories and false rumours.
A "lot" are not necessary, true. But the fact that what we know, we
learned by trial and error in many cases, would be an appropriate addition.
The point of my post was not to denigrate the position that nuclear power
has attained, but to add to the "school of hard knocks" that got it there.
Are you going to stay grouchy?
David A. Smith
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