Re: Being eyeballed

In message <499e9ce6$1$fuzhry+tra$mr2ice@xxxxxxxxxxxxxxxx>, Shmuel Metz
<spamtrap@xxxxxxxxxxxxxxxxxxxxxxxxxx> writes

Are you taking into account the cost of safely disposing of them if we
don't exploit them?

Exploiting waste isotopes doesn't dispose of them, per se. What you're
thinking of is "burning" them, and sadly that doesn't really work.
Intense neutron bombardment is only available from a reactor, and that
would result in more "waste" than is burnt off. There are other ways of
destroying radioactive waste isotopes, using for example linear
accelerators but they consume massive amounts of electrical power which
in turn means producing more nuclear waste... I did recently see a
proposed radioactive waste burning facility using plasma tapped from a
fusion reactor but since we don't actually have any power-generating
fusion reactors at the moment this concept is yet to be tested.

Storing long-term waste is a lot cheaper and easier than burning it,
and probably safer. That's not to say some new method might be invented
in the future but there isn't a lot of waste to start with and trying to
extract usable amounts of energy out of it is probably a non-starter
(unless we can invent a simple method of annihilating matter).


We don't have a lot of Pu-239

Are you including the Pu-239 in spent fuel that we haven't reprocessed?

OK, here I'm going to make some approximations as I'm not sure of the
numbers and details like this can be difficult to track down... assume
MOX is 50% Pu-239 and 50% U-235, and the fuel pellets in the fuel rods
are enriched to 6%, with the rest being U-238. A loadout for an MOX
reactor will be 80-100 tonnes of pellets, which will last about a year
with a 90% baseload schedule, with the fuel rods depleted to about 50%
of their initial elemental content in that year of operation, delivering
about 550MW/year. That means a single MOX reactor will burn about 3
tonnes of Pu-239 per year.

In contrast it takes only a small amount of pure Pu-239 to make a nuke
-- less than 10kg if the design and engineering is top-notch and the
metallurgy of the Pu metal pit is highly optimised plus neutron
reflectors, initiators and other bits and bobs, and when I signed the
Official Secrets Act a long time ago it was made clear to me there was
no statute of limitations on information I picked up in the course of my
duties, even though I wasn't working on the nucleonics side of things.

From what I understand from various sources the US has about 100 tonnes
of Pu-239 stored, the proceeds of decommissioned warhead material.
Stored fuel rods probably have another 30-40 tonnes of Pu-239 in them.
Unless a reactor is run to deliberately breed Pu it doesn't produce a
lot -- each spent fuel rod might have a few grams of Pu-239 in it.
Reprocessing all of those rods and using the Pu-239 to make MOX fuel
would result in 50 reactor-years of fuel or thereabouts.

The UK has about 70 tonnes of Pu-239 in store, from what I remember
reading, the result of decommissioning a bunch of warheads over the
years plus what we extract from our fuel reprocessing lines. That would
drive one MOX reactor for about 20-25 years. Not a lot, really, compared
to the hundreds of tonnes of U-235 burned each year in existing reactors
world-wide.
--
To reply, my gmail address is nojay1 Robert Sneddon
.

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