atomic_fungus (atomic_fungus) wrote,

#2274: Another pile of "thorium is the answer!" nonsense

God damn it, I hate this horseshit.

I hate it because it's a bunch of horseshit. I'm 100% for nuclear power (possibly 200%) but we can already do everything with uranium that this article claims can only be done with thorium. Besides that, it gets a shitton of science wrong.

The article starts thus:
What if we could build a nuclear reactor that offered no possibility of a meltdown, generated its power inexpensively, created no weapons-grade by-products, and burnt up existing high-level waste as well as old nuclear weapon stockpiles? And what if the waste produced by such a reactor was radioactive for a mere few hundred years rather than tens of thousands? It may sound too good to be true, but such a reactor is indeed possible, and a number of teams around the world are now working to make it a reality. What makes this incredible reactor so different is its fuel source: thorium.
I've said it before: we can already do that with uranium reactors. All of it.

That bit about radioactive waste, by the way: an isotope's radioactivity is inversely proportional to its half-life; the longer the half-life, the less instensely radioactive it is. So a given mass of nuclear waste that's radioactive for "tens of thousands of years" is a lot less dangerous than an equivalent mass of something which is radioactive for "a mere few hundred years".

Nuclear isotopes don't emit a steady amount of radiation and then stop; it's not like you're burning a lump of coal or something. The term "half-life" refers to how long it takes for a given mass of an isotope's output to be reduced to 50% of whatever its initial value was. If your sample of isotope R has a half-life of 5 years, and right now it's putting out 40 curies of radiation, in five years it'll be putting out 20 curies, and in ten it'll be putting out 10. (In 40 years, it'll be emitting 0.153 curies.) If your sample of isotope S has a half-life of 50 years, and right now it's putting out 5 curies of radiation, in 50 years it'll be putting out 2.5, and in 100 it'll be putting out 1.25. OMG, S is dangerously radioactive longer than R!

It then goes on to correctly identify the real hazards of coal--the toxic ash, the radiation, the deaths of coal miners, etc, etc--as well as raising the "global warming" shibboleth. The writer talks about solar and wind power, and how well they work as primary energy sources, and blah blah blah blah blah.

On page 3 of the article, we get into the seriously incorrect stuff. His talk about the uranium fuel cycle is full of the usual misconceptions and exaggerations; but what really set me off was this:

"...[S]pent fuel can be reprocessed - but this is a much more difficult job than basic enrichment because of the high number of fission by-products in the spent fuel."

Reprocessing spent fuel is a chemical process, and we have quite a bit of experience with handling dangerous chemicals. Radioactivity is just another parameter, like acidity and toxicity and volatility; in an industrial setting, all kinds of dangerous chemicals are routinely handled safely--and I'm talking about stuff which is truly nasty, things like hydroflouric acid or nitrogen tetroxide and monomethyl hydrazine--things that are not only poisonous, but explosive.

Enriching nuclear fuel is a very equipment- and time-intensive process. Example: the Army built Oak Ridge, Tennesee, in order to enrich uranium.

Basic enrichment is a lot more difficult than reprocessing spent fuel.

Right before that nonsense:
hen the U-235 in nuclear fuel burns down to around 0.3 per cent concentration, it's no longer of use in a reactor. At this point, the proportion of U-238, along with other fission by-products, including some very radioactive isotopes of americium, technetium and iodine, is too high. Many of these elements are called 'neutron poisons' because they absorb neutrons that would otherwise be happily colliding with other U-235 nuclei to spark off more fission.
What you do is remove the "neutron poisons" from the fuel rod, then put it back in the reactor. These poisons are highly radioactive and toxic, but their half-lives are pretty short.

You don't take the fuel from the reactor and send it right to be reprocessed because of them. Spent fuel has to spend about a year or so just sitting in a pool of water while the most intense radiators half-life themselves to death. Then you reprocess the stuff.

But the most fatuous nonsense of all is this paragraph:
First of all, unlike U-235 and Pu-239, thorium is not fissile, so no matter how much thorium you pack together, it will not start splitting atoms and blow up. This is because it cannot undergo nuclear fission by itself and it cannot sustain a nuclear chain reaction once one starts. It's a wannabe atom splitter incapable of taking the grand title.
THIS IS FLAT-OUT WRONG. It contains one correct element; the rest is wrong.

It is a fact that you can't make a nuclear bomb with thorium. But one of the byproducts of the thorium fuel cycle is U-233, which is a potential bomb-grade fissile material. It's not as good as U-235, and its shorter half-life makes it more dangerous to work with, but it's there, same as plutonium is in the uranium fuel cycle.

But if thorium were not fissile, it would be useless as nuclear fuel. If it could "not sustain a nuclear chain reaction once one starts" it would be no better than lead for generating power. The process used to generate nuclear power is nothing but a chain reaction--one which is controlled, one which is moderated to keep the rate of power release at a manageable level. But a nuclear bomb detonation is the exact same process, only allowed to run away, to release as much energy in as short a time as is possible.

The article then goes on to explain that the thorium reactor requires--guess what!--uranium and plutonium to achieve criticality and function. What the writer is doing is confusing reactor design with properties of nuclear fuel. You can design any damn reactor to be sub-critical and to require an external source of neutrons to function; you can do that with uranium or plutonium or WTF-ever. Shit, you could do it with lead if you had a sufficiently energetic source of neutrons.

A subcritical reactor can't melt down--you just shut off the source of neutrons--but you don't need to build a subcritical reactor to get a reactor that can't melt down. Read Freeman Dyson's Disturbing the Universe; in that book he discusses how he and a team of scientists working for GE designed and built a reactor which was physically incapable of melting down. They demonstrated this to the bigwigs: they blew all the control rods out with compressed air. The reactor briefly made a few gigawatts--for a time measured in microseconds--and then settled down to its design output of half a megawatt. With no control rods in it.

Try that with a conventional reactor and you'd land somewhere between Three Mile Island and Chernobyl.

The point is, we don't need thorium to do any of the things this guy (and other thorium proponents) gush over. Uranium will do it all if it is simply allowed to do so.

I like this:
Imagine the West offering thorium-fuelled ADS reactors to countries such as Iran or North Korea: this would satisfy their demands for cheap nuclear power, but entirely avert the risk of the civil nuclear program leading to the development of nuclear weapons.
What a load of pie-in-the-sky peacenik nonsense that is! Iran and North Korea would scoff at this. They'd say, "We don't want to be dependent on western nations for our nuclear power!" but in fact they'd be refusing because they couldn't make nuclear weapons with the spent fuel.

Iran and NK don't want nuclear power because they need energy; they want it so they can build bombs. Anyone who thinks otherwise is fooling himself.

And then he begins his conclusion: "CAN ATOMIC POWER be green?"

Damn it, it already is! But don't expect a lefty liberal type to understand that.

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