LFTR: Energy too Cheap to Meter? Part 1

Points of accuracy:
“the stuff called “DU” used in weapons”
Specifically, used as a kinetic hammer in conventional weapons (i.e., it’s heavy and it’s hard; the rest of a projectile falls away, and the DU slug penetrates). We’re in a nuclear context; it might be best to let people know you’re not talking about the big boomy weapons.

“current crop of Generation II”
The current crop is a mix of Gen II, Gen III and Gen III+ reactors.

“Very radioactive!”
Gram for gram, the waste from conventional reactors is actually less radioactive than the output from LFTR. This is because all LFTR produces is fission products, while 95% of the output of a conventional reactor is depleted uranium.

Still, that’s a good thing; higher radioactivity means it lasts less time – as you say, after 10 years, about 83% of the mass of the fission products is stable, and the remainder has a 30 year half-life, meaning about 300 years for backgrounding.

Most of this is 137Cs, which may have applications in betavoltaics, if we can work out what to do about the gammas: 137Cs beta decays to 137Ba, which is metastable with a half-life of a few minutes, and emits a ~662keV gamma ray, powerful enough to use in food sterilization.

Anyway, the reason we have to store things in Yucca for about 250,000 years (not 10,000) is because of the actinides. They tend to have half-lives that live in the range of 1,000 years to 100,000 years – meaning their backgrounding time is between 10,000 and 1,000,000 years. Now, thankfully, the longer-lived isotopes are, by definition, significantly less radioactive – so most of the isotopes past 25,000 can be considered “backgrounded” after less than a full half-life. That still means storage for 250,000 years if we’re dumb enough to go that route.

“This one ton of Th in turn produces 1 ton, IN A YEAR, of waste.”

Theoretically – and, mind, I don’t doubt the theory.

It’s dead simple math:
The fission of U-233 produces 200.1 MeV of heat.
The reation, in sum, takes 234 amu (1 atom U-233 + 1 neutron)
So, the absolute energy density of U-233 is 0.855 MeV / amu, 22.9 MWh/g, or ~2.6 GWy/tonne; that means to produce 1 GWy / tonne, we only need to be 38.2% efficient. That’s totally doable, re Carnot, at the higher temperatures proposed by LFTR.

“This Th can be used AS IS in a LFTR.”
Incorrect; it must be processed into ThF4.

“The LFTR cannot runaway or meltdown like a Uranium Reactor.”

A meltdown in a LFTR would not be a melting of the fuel elements; it would be a thermal-mechanical failure of the containment (perhaps best called a melt-through). The primary design concern is that, at anything above the desired operating temperature, the fuel is significantly subcritical, and that (the fuel’s heat production plus the heat production of the maximum safe fission product load minus basic heat losses) is well below zero at a temperature well below the heat tolerance of the weakest part of the system. In the event the freeze plug system fails (i.e., a piece of graphite breaks off from the core and blocks the exit), we need to know how the reactor will behave in a power excursion.

The way to do this is via, first, careful geometry; second sacrificing a little efficiency for a little safety (i.e., in heat retention), and third, selection of materials such that the math works out realistically.

Just ME back again… I have been busy with TWO blogs this past week….

One focussing on Thorium
http://just-me-in-t.blogspot.com/2010/06/nuclear-terror-nightmares-are-made-of.html

The second, on other forms of clean green energy

http://just-me-in-t.blogspot.com/2010/06/define-sincerity.html

I would be very happy for you to read and comment (on the blog) if you felt it worthwhile.

I have appreciated this group and the conversations.

Cheer’s from a cold, wintery Tasmania

Just ME in T

our prime Minister who is not terribly popular and may get taken out next election – Kevin Rudd is pro nuclear…. Aussie per se are anti…… but I see there is quite a lot of research into this mineral… and we do seem to have the worlds most accessible supply on hand…… However we do mine heaps of uranium and it is a big money spinner for the government…… as with most things follow the almighty dollar! IF this mineral becomes a MUST HAVE world wide you can bet your bottom dollar Australia will mine it, gather it and sell it…. lets hope they continue research into using it as well.

Thanks for the great work…. part two soon I hope?

Just ME in T (Tasmania)

Oops… sorry, back again with another interesting link for you.

So why haven’t you heard more about thorium power? After all, thorium is already widely used for industrial applications such as welding and lending physical strength to magnesium. And its potential use as a fuel for nuclear reactors has been understood for half a century, as Wired reports: in 1958, nuclear scientist Alvin Weinberg, then-director of the US military’s Oak Ridge National Lab published a nearly 1000-page summary of research into thorium-fueled power.

Despite its theoretical advantages over uranium, however, Weinberg’s advocacy of thorium for nuclear reactors fell onto deaf ears as Cold War-era governments jumped onto the uranium bandwagon. The reason, Wired tells us, is that politicians were just as interested in the weapons-grade plutonium-239 that the process produced. By the time Weinberg left Oak Ridge in 1973, research into thorium-powered nuclear reactors had all but disappeared.

http://apcmag.com/Content.aspx?id=5094

seems the highest (currently) source of this THORIUM is in Australia……….

That is fantastic news…I’m sure one of the rich billionaires will develop this!

Krell, What an amazing and interesting post. I had no idea this technology exists. I can’t wait for Part 2, I’d imagine it would take incredible efforts from use of information technology and even grassroots efforts to overcome the opposition lobbying/corruption of vested energy interests as well as the military interest you indicate.
Great work.