Re: Irish Electricity II


kevinmccabe@xxxxxxxxx wrote:
Si wrote:

Also for what it is worth. One can make a fission bomb with just U235
(http://en.wikipedia.org/wiki/Little_Boy); standard reactor fuel. So
why is every one getting hung up on the fast breeder approach? The only
difference would be the scale of the explosion by using plutonium. What
do a few megadeaths either way matter? As Stalin put it: one death is a
tragedy, one million a statistic.

That statement by Stalin has always been, for me, the epitomy of real
evil. That aside, can you make a bomb like little boy with uranium
straight out of the ground?


I don't think so. I think the minimum enrichment you need is 20%,
Natural uranium is 0.7%. IIRC Little boy was > 85%. The main effect of
going to lower enrichment levels is the rise in critical mass.


That's what the CANDU's use. And, wouldn't
the enrichment level on the PBMR's be too low for weapons production as
well? I know the Canadian reactors might be criticized on the basis of
the cost of heavy water production, but the PBMR's are cheap enough.
And, if that reeeeeeeeaaaaaallllllllly isn't good enough, why not
strictly ration Iran through enrichment in Russia with tight inventory
controls. Then, they could use LWR. By the way, what do you think of
the ones that use liquid metal?


I've designed a rocket motor that uses liquid sodium in a heat pipe to
remove heat from the combustion chamber. Nobody would buy it of course,
not even my internal management. (Standard Dilbertian whinge: It would
work). It was entirely passive and used capillary action to pump the
hot stuff. I bet it is the same sort of detailed design that the liquid
metal reactors use (we mostly use the same metals). I really must look
at the thermal cycles involved. It is typically the case that heat
transfer is more efficient with the largest temperature difference.
Liquid metals probably give you that. They also lack the high pressure
water system which is a nice Brucey bonus. Water, hot enough to be
steam at athmospheric pressure, held in stainless steel pipes
(corrodable still) at pressures to keep it liquid, is not to my mind a
safe design. Mineral oil or if you want liquid metal at much lower
pressures seems to my Failure Modes, Effects and Critically addled mind
to be a LOT safer. The thing about the sodium is by dumping solid pase
material into the heat exchanger loop you could remove a lot of heat as
it liquifies, like chucking ice cubes into yer drink. Another safety
bonus. The liquid metal reactors need enriched fuel as far as I can
tell.



Si


"Bog snorkler extraordinaire"

.

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