[geeks] Global warming, was Mr Bill?

[Sandwich Maker]

" From: wa2egp at att.net
" 
" -------------- Original message ----------------------
" 
" > while the half life of pu-239 is only 24Ky, u-238 [unfissionable in
" > current reactors] is 4.5Gy.  even u-235 half life is 0.71Gy.  and high
" > level 'waste' is essentially pure oxide, and while i admit i don't
" > know the analysis a large percentage has to be u-238; afaik even after
" > enrichment the bulk of the fuel load is u-238.
" 
" They enrich the fuel meaning they separate the 235 from the 238 so the
" fuel rods do not have much 238 in them.  238 is thrown in fuel rod in
" breeder reactors which the US does not need at this time since we have
" plenty of 235.  Those radioactive breakdown products in the spent rod
" have shorter half lives but still have to be stored for about 2500
" years till the radiation level is considered "safe".  238 is not as
" radioactive as 235, you can handle it without much protection for
" decent amounts of time.

isotopic separation is not easy...  weight difference between
elemental 235 and 238 is less than 1.3%, and they can't be chemically
distinguished.

from the 56th crc: natural uranium is 99.283% u-238, 0.711% u-235, and
0.0054% u-234.  it is 'slightly' enriched [amount unspecified] for
power plant use, 'spent' [depleted] when u-235 falls to 0.2%.

if we have 'plenty' of u-235, we are positively swimming in ~140x as
much u-238.

i believe power plant fuel rods are still over - perhaps well over -
95% u-238 ['slightly' above could well mean 'up to 1%', and i've heard
numbers like 1-3% for fuel rod fissionable consumption].  yes, it's
-relatively- safe to handle [suggested by the above enrichment levels
- though i'd rather not] and the way to use it is to breed it, usually
to pu-239.  the safe way would be to breed the pu only as fast as it
fissions, a 'slow breeder' reactor, for which there are several
proposed designs.  my favorite is the liquid-fueled slow breeder,
which constantly reprocesses the fuel load, removing lead and adding
fissionables as needed.

nb. india is working on thorium slow breeders, as it's more abundant
than uranium and they're sitting on half the world's known th
reserves.  they'd work by breeding th-232 to u-233, and iirc need a
uranium 'ignition charge' to start.
________________________________________________________________________
Andrew Hay                                  the genius nature
internet rambler                            is to see what all have seen
adh at an.bradford.ma.us                       and think what none thought