Re: Deep burn transmutation


daestrom wrote:
"Giuseppe" <pr@xxxxxxxxxx> wrote in message
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I know that there has been some work on transmutation of spent fuel
post-burn cycle, but this is new to me. I think in general there is a
worldwide effort towards greater burn-through both for efficientcy and
transuranics reduction. The problem, as always, are those bitch
daughters of uranium...-Jitney

If you burn all fissile plutonium (> 99%) and 70-80% of all actinides,you
virtuaaly eliminate wastte problem,it becomes a non-issue
Definitly I still don't understand why with these SC-Mhr ("self-cleaning"
Mhr) we can produce 15-20 MWyear per tonn of natural uranium,instead 5
MWy/tonn....


Not sure what you mean by 5 MWy/tonn. Modern LWR's can run to exposures of
about 15000 MWd/ton. That's about 41 MWy/ton. But this doesn't burn all
the actinides. It does, however, get substantial energy from Pu breeding
during it's life.

I think it is more than just a simple matter of exposure. The fuel must
also mechanically endure. Current LWR designs are limited by several
factors. Reactivity is a combination of fissile material and a minimum of
poisonous fission products. Cladding strength versus pellet-cladding
interaction, corrosion buildup affecting heat transfer (which in turn
affects centerline temperature), pellet swelling and cracking (UO2) are
other factors.

Some other fuel designs (metal fuel, UC, pebble seeds, etc...) get around
some of these problems, while having problems of their own. (metal fuel
cannot tolerate nearly as high a centerline temperature, but it's better
thermal conductivity means normally operates much cooler)

And if you just melt the fuel in a salt you can burn the actinides to
destruction while bubbling out the sterile neutron poisons and breed
without high energy neutrons.

.

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