Posted on 07/04/2013 12:17:13 PM PDT by Innovative
I read the headline as “Thorazine.”
Interesting.
Abudant,cheap energy means the people will have more freedom of choice.
Socialists NEED everything to be in short supply for control purposes.
“But thorium has to be radioactive, too, for this to work, right? What makes it less dangerous than uranium?”
A number of things, which, if you consider the entire trail from mine to megawatt, tilts considerably towards Th.
First, the Th that comes out of the ground is, for the most part, ready to go pretty much as it is. Yes, of course it has to be cleaned up and concentrated, just like tin or lead or any other ore. Th, like U, is not very rare, there’s lots of it. Ahh, but the U used in reactors is the much feared U-235, which is only about .7 % of all naturally-occurring U. So, we have Th, about 3-4x as common as all U, but the U we are talking about is less than 1% of all U, so the relative occurrence of the salient material is about 500x as great in the case of Th. Furthermore, the chemical and physics processes needed to concentrate and isolate the U-235 from the more common U-238 are fairly nasty and generate lots of chemical wastes. And mining wastes, because so much more needs to be hauled out of the ground.
Now on to the reactor. These are heat generators that drive steam turbines. Most U-fired reactors run on U enriched only to a 3-5% level, the rest being less-desirable U-238. In subs, the U is enriched quite a bit more, to about 20%, I believe, because the whole thing has to take up less room. When that enriched U is “used up”, not that much of it has been used, it turns out. It’s like the gas tank is empty when the needle is still at 95%. At that point, the fuel stops being efficient and is generally replaced. That which is pulled out of the reactor remains fiercely radioactive, both with the remaining U, but some has also been transmuted into Plutonium (U and Pu are alpha-emitters which are considered less dangerous, but they remain radioactive for hundreds of thousands or even millions of years. And the radioactive poisons co-created in the replaced fuel are also quite dangerous, and toxic, and all that. Generally, most reactors operate at very high pressures, and thereby are vulnerable to leaks.
Th reactors, in most designs, do not operate at very high pressures, indeed they run at atmospheric pressures. So that is a piece of safety. Secondly, Th reactors have to be fed with an external neutron source, AND, must have a moderator (surrounding liquid) to run. So, shut off the neutron source and the reactor stops, right now. Most Th designs have a refrigerated “plug” much like a plug in your car’s oil pan at the bottom. Lose power, and the plug melts, and the moderator liquid runs out into some sort of collection pool and the reactor stops. So Th reactors are much, much less vulnerable to these high-pressure, overheating scenarios blowing the guts sky-high; whether by pure operational pressures or by hydrogen generation (which blew up Fukushima)
Now the bad news: Th reactors produce intense gamma radiation which has the tendency to irradiate everything and make it radioactive. The handling has to be done with sophisticated robotics. The building housing the Th reactor ultimately gets to be radioactive. And this is dangerous radiation, whereas the alpha radiation from U or Pu, while dangerous, can be shielded literally by cardboard. It tends to not be penetrating. Th reactors also use rather corrosive molten salts in their innards, and these require fairly exotic (but known) alloys to deal with.
To sum up: Th reactors can eat all the rotten, only partially consumed U/Pu fuel rods out there. That means all those filled-up fuel rod storage pools out there can be emptied, and that gets rid of a serious hazard (as seen w/Fukushima) and a proliferation risk. They eliminate much of the mining and refining effort req’d for U. They do not produce weapons-useful byproducts. They are massively less vulnerable to overpressure, overtemperature events. When they fail, the failure tends to shut off the reactor, vs when a pressurized U reactor fails, it tends to move towards thermal runaway, overpressure, and catastrophe.
But they produce fiercely radioactive byproducts. The thing about “fiercely radioactive”, though, is that such items decay much more rapidly, in decades vs tens of thousands of years. Nothin’s free.
Your post is very informative and balanced. But it opposes the One’s push to eliminated nuclear power. And therefore it is just another racist Republican attack on the Black Man in the White House (TM).
As the Forbes article implies, in twenty years, India and China will have left us in the dust in both uranium and thorium-fueled reactors: in research, design, construction and operation. The U.S. might be best served to concentrate its energies solely on Thorium.
This capital-intense field requires massive government research sponsorship.
Yup, I’m not optimistic about Th development prospects in the US. It will likely occur in India and China. Ironically, all this nat gas we are finding through fracking will probably produce a 30-year delay in moving towards Th power in the US.
Good rundown, I appreciate that. Your description matched pretty closely the Forbes article I linked to upthread, but it was a tad easier to understand.
My remaining questions are:
1) How do you generate the heat to melt the salt?
2) How do you generate the external neutron source?
It sounds to me that a significant outside energy source would be needed not just to start a reaction but to sustain it as well. Or could a Th reactor just be “jumpstarted” and then self-sustained with a portion of the resultant generated energy?
That as a very useful description. Thank you.
How can the irradiated material from a thorium rector be stored? Do you, for example, surround the thorium with liquid mercury, then pump the mercury out and store it underground once it has reached a given level of radioactivity? Whether the half-life is a thousand years or a million may be inconsequential when there is a deadly risk today.
we need to advance any means of “mini” nuke technology and technology and materials science to make the “containment” vessel for such devices able - in the case of a spaceship unable to continue and land safely, to either survive a fall to earth from the upper atmosphere, or self-destruct after being jettisoned above the atmosphere - and then nuclear power for space flight
I’m not quite sure as the tiny details get more specific, but I believe the salt need not be heated very high before it liquifies, I think about 150 C, so a reasonable external heater is used before the reactor starts up and keeps it hot...MUCH hotter, more like 650 C in operation.
Yes, the neutron source is another piece of non-trivial engineering and indeed, my readings seem to point both towards high-enriched uranium and/or some sort of accelerator device that generates protons, then accelerates them at a metallic target, generating neutrons by a process known as spallation...literally having them split off the backside of the target. I can’t claim a deep understanding of the details.
Ah well, there’s a reason I didn’t major in nuclear physics, but it’s an interesting topic nonetheless.
I frankly do not know the answer, but the core concepts are:
The sheer volume of “waste” or byproduct is massively less than with U reactors because there is not this tyranny of having the fuel becoming useless (yet still quite dangerous and still very physically hot) when it is only 5% (or so) consumed.
And since such Th reactors can use the partially burnt-up fuel now overflowing from existing fuel storage ponds, this adds to the overall “mass reduction” the adoption of the Th process would cause/create/allow.
Plus the amount of dirt we need to shove around and dig out is less than 1/100th that of U. Indeed, most Th comes from sands that are more or less surface-found items.
The nature of the emitted radiation from Th byproduct is intense gamma radiation: It calls for massively thick shielding and is without question a serious hazard to life, etc; and will remain so for decades. But not thousands much less tens of thousands of years. The alpha emitters, U and Pu (and there are some of those in Th waste, but only fractionally) are hazards because while they can cause tissue burns, the bigger hazard is their ability to form critical and near-critical masses when, for example, liquids are pumped from one tank to another, or when containers are stored on opposite sides of walls. Oak Ridge had a minor accident like that in the 40’s, and I think in the 80’s, Japan had an accidental overconcentration accident in a power plant when pumping liquids from here to there.
“The object was/is to destroy capitalist society by starving it of energy.”
Unfortunately, you hit the nail on the head! This is indeed the real goal.
Thanks for a very informative post.
Sort of a swords into plowshares kind of deal.
/sarc
The World: At the Cusp of the Millennium since 1962.
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