Thorium: The Wonder Fuel That Wasn't

Lasrick (2629253) writes "Bob Alvarez has a terrific article on the history and realities of thorium as an energy fuel: For 50 years the US has tried to develop thorium as an energy source for nuclear reactors, and that effort has mostly failed. Besides the extraordinary costs involved, In the process of pursuing thorium-based reactors a fair amount of uranium 233 has been created, and 96 kilograms of the stuff (enough to fuel 12 nuclear weapons) is now missing from the US national inventory. On top of that, the federal government is attempting to force Nevada into accepting a bunch of the uranium 233, as is, for disposal in a landfill (the Nevada Nuclear Security Site). 'Because such disposal would violate the agency's formal safeguards and radioactive waste disposal requirements, the Energy Department changed those rules, which it can do without public notification or comment. Never before has the agency or its predecessors taken steps to deliberately dump a large amount of highly concentrated fissile material in a landfill, an action that violates international standards and norms.'"

Comments

Is this about Thorium or Uranium 233?

[MetalliQaZ]

Interesting caption to use as the summary.

Re:Is this about Thorium or Uranium 233?

[Anonymous Coward]

For a terrorist, however, uranium 233 is a tempting theft target; it does not require advanced shaping and implosion technology to be fashioned into a workable nuclear device.

Which is an interesting statement, given that the US government has never been able to successfully produce a working U233 bomb. In fact they've invested a lot of effort into Pu239 and U235, which would be pointless if all they had to do was bread common-as-muck (literally) Thorium into a useful nuclear weapons material for a fraction of the cost.

The reality is that U233 is almost entirely useless on it's own: off the top of my head you might be able to use it to make workable tampers for Plutonium implosion bombs; the evidence suggests that's actually the only place U233 has ever been used in a working weapon. That still wont get you far without the Pu and U235 (for the primary).

Re:Is this about Thorium or Uranium 233?

[slew]

Thorium 232 + a neutron -> Uranium 233.

Not exactly ;^)

Th232 + neutron -> Th233 (which isn't as stable stable)

Then two stages of beta- decay

Th233 -> Pa233 + electron + anti-neutrino
Pa233 -> U233 + electron + anti-neutrino

The problem is with U232 production is because all of these intermediate products are also fissile in the reactor (e.g., can interact w/ stray fast neutrons and undergo extra neutron decay before undergoing beta- decay resulting in U232 instead of U233).

However, the issue isn't that U232 is so unstable it decays with products that emit large amounts of gamma radiation (which in the decay chain, Tl208 is a big gamma emitter so it's really dangerous), it's mostly that you can't use chemistry to separate U232 from U233 (since only the mass is different, not the valence electrons). You either have to use advanced techniques (e.g, laser isotope separation), or modify your reactor parameters so that U232 production is reduced.

The ironic thing is that purported proliferation resistance of U233 is because reactors can be deliberately tweaked to increase the concentration of U232 to denature the U233. However, as I understand it, there is no particular technical reason to do this other than proliferation resistance (except to make it more dangerous to potential nuclear power plant workers as if that was a goal). If a rogue country wanted to operate a Th reactor to create large amounts of U233 w/o a limited amount U232 contamination, apparently it's not that hard to do (basically replacing the fuel more frequent schedule than normal, since most of the U232 yield comes at the end of the fuel cycle where there are more high energy neutrons bouncing around)...

That, plus a failure to ever produce a non-fizzle U233 bomb, means that this really isn't a good fission bomb source material.

If your goal is to simply produce a bomb, (not necessarily a large one with optimal yield), apparently India detonated an experimental U233 bomb as part of their Pokhran-II tests back in 1998... I don't think that bomb was a fizzle...

questionable presentation

[Mr D from 63]

The author can't seem to distinguish between the paths of weapons based programs and commercial nuclear electrical generation. He infers conclusions that he dare not spell out.

Statement of ridiculousness include;

For a terrorist, however, uranium 233 is a tempting theft target; it does not require advanced shaping and implosion technology to be fashioned into a workable nuclear device. The Energy Department recognizes this characteristic and requires any amount of more than two kilograms of uranium 233 to be maintained under its most stringent safeguards, to prevent “onsite assembly of an improvised nuclear device.” As for the claim that radiation levels from uranium 232 make uranium 233 proliferation resistant, Oak Ridge researchers note that “if a diverter was motivated by foreign nationalistic purposes, personnel exposure would be of no concerns since exposure would not result in immediate death.”

But this material is actually extremely difficult to make a warhead out of or use in any weaponized manner other than a dirty bomb. But with little effort, its easy to find that U-233 has the "unavoidable co-presence of uranium-232[6] which can make uranium-233 very dangerous to work on and quite easy to detect." That was conveniently ignored.

So, while it could be used in a dirty bomb, there are much easier, more tempting targets for that. Particularly when its material stored in a highly protected area. "No concerns"? Give me a break.

As for the Nevada waste thing. What he describes as a simple "landfill" is actually a waste area within the Nevada National Security Site.

Its easy to see right through the BS this author has laid out. Its a shame he doesn't seem to care about his own credibility. Just another asshat that does nothing but talk. Its a shame, because there are legitimate issues here to discuss, and it helps when the facts are laid out in a responsible manner.