Timothy Murphy wrote:
Ian White wrote:

The cumulative amount of high-level waste produced by *any* fission
reactor system is almost exactly proportional to the cumulative amount
of heat energy that has been generated. There is no significant
difference between thermal reactors and fast reactors in this respect.

Why?

See below.

You seem to make claims like this with great confidence

Long ago in a distant galaxy, the assessment of waste arisings from
various nuclear fuel cycles was part of my job.

but as far as I can see without the slightest evidence.

Unlike you, I am not satisfied by pulling some half-relevant quotation
off the web and calling that "evidence". The information is all
available, but organising and explaining it properly would take far more
time and effort than I'm prepared to donate to the cause.

However, the explanation for the statement quoted at the top of this
message is simple enough. When a heavy atom (usually U-235 or Pu-239)
undergoes nuclear fission, it splits into two lighter atoms of fission
products and releases a certain amount of energy. The atoms of fission
products remain in the fuel, and if the fuel is reprocessed those atoms
end up almost entirely in the high-level waste. The energy from the
nuclear fission ends up as heat, which is used to raise steam and
generate electricity.

Fission is a complex statistical process which can produce a range of
different pairs of fission products, but the fission energies of various
kinds of heavy atoms are very similar. That means there is a fixed
three-way relationship between the numbers of atoms of fuel that have
been fissioned, the amount of heat energy generated, and the amount of
HLW. That relationship comes from the basic physics of fission, so it's
essentially independent of the type of reactor.

Certainly there are many differences between reactor systems, and more
complications than you can possibly imagine, but if you thrash your way
through a much more detailed assessment, you'll find that basic
relationship between energy generation and the resulting amount of HLW
still holds good.

My mug of coffee has gone cold (and after revising, it has now gone cold
twice, dammit). If you want to know more, you'll need to do a lot of
detailed work. I have no doubt that you're intelligent enough to do
that, but at present you are just recycling other people's opinions. For
example, the following statement that you quoted has nothing to do with
fast breeder reactors, which we were discussing - it's about
uranium-fuelled thermal reactors, and the decision whether to do any
fuel reprocessing at all.

"Considerable experience with reprocessing in France however, has indicated
that a one way fuel cycle based on extracting and processing fresh supplies
of uranium and storing the spent fuel is more economical than reprocessing,
not the least because in the process of plutonium extraction, the volume of
high-level liquid radioactive waste increases about 17-fold."
http://en.wikipedia.org/wiki/Nuclear_reactor

The only thing odd about that statement is that factor of 17. If you
operate a once-through system - not reprocessing the spent fuel but
leaving it intact, storing it, and eventually disposing of it as waste -
then there will be *no* high-level liquid radioactive waste at all.

No doubt some further digging would reveal the origins of "17" (I could
make some guesses, but won't). Let's just leave it as yet another
example of what can happen when basically correct information is quoted
out of context.

I'm sorry this whole subject is so desperately complicated... but that's
how it is. It takes an awful lot of time and effort to break through to
the level where you can generate your own information and accurately
judge the information from other sources.


Now please can I go read some bright ideas for cutting sheets of foam?


--
Ian White