What’s the SD on thorium as a replacement for uranium in nuclear reactors? Is it just not feasible at this time? Is there any solid research going on to develop it as an alternative?
It can be done in principle, but why should anyone? Uranium is still plenty cheap and abundant, and will remain so for a very long time.
I posted this a while back on Una’s board but it might help put some context around the idea of thorium reactors. From my quick look, they look safer and cleaner than conventional ones.
I originally came across the article in American Scientist.
Damn the link has been changed - try this one from the same site - http://www.energyfromthorium.com/pdf/AmSci_LFTR.pdf
Sort answer, thorium doesn’t fission directly, it can only be used to breed a fissionable isotope (U-233 I believe). For a multitude of reasons, the US hasn’t done much with breeder reactors (other than nuclear weapons productiion).
This guy did it.
IIRC here is part of the problem.
You need stuff OTHER than thorium to breed thorium into a usable fissile fuel. The other stuff being uranium (and subsequent plutonium).
Once that OTHER stuff is used up or more scarce, then using it to “breed” the thorium is closing the barn door after the horses have left so to speak.
Yeah, we can use what uranium we have LEFT to breed the thorium. But the stuff we “wasted” not breeding the thorium is a lost opportunity we just can’t get back.
Be warned this is age old memories talking here.
Because thorium is even cheaper and more abundant, and can be found on every major landmass and within the domain of many major nations that are poor in natural uranium resource. Thorium also has some efficiency advantages in a closed fuel cycle or complete burnup reactor (like a subcritical reactor) and does not require the expensive and radiotoxic-waste-producing enrichment cycle; it simply has to be separated and refined, producing far less waste.than the conventional uranium cycle. It also can’t be used to produce “pure” (i.e. weapons-grade) [sup]235[/sup]U and [sup]239[/sup]Pu, which alleviates weapon proliferation concerns and thus the technology can be distributed to developing nations without fear of it being turned back upon its providers.
However, thorium cycle reactors and their fuel cycle are significantly different from the boiling water and pressurized water reactors that are common Gen II and Gen III production reactor designs. While combination of the fertile [sup]232[/sup]Th is necessary with [sup]235[/sup]U or another fissile material for use in traditional water-cooled reactors, using a coolant with low neutron absorption allows for the use of an external neutron generator (such as a Farnsworth fusor) to “enrich” the fuel into a fissile [sup]233[/sup]U. The most efficient thorium reactors are molten salt reactors that operate at low pressure but with very high temperature salts. This is not a totally unproven technology; both the United States and the former Soviet Union experimented with molten salt reactors for breeding fuel. Oak Ridge National Laboratory ran the Molten Salt Reactor Experiment for four years in the mid-Sixties with no significant issues other than material degradation from neutron embrittlement, a problem that can be overcome by using newer, embrittlement-resistant alloys. A full closed-cycle thorium reactor will produce relatively little waste compared to the conventional once-through cycle with enriched uranium, and not the potentially weaponizable products that come from heavy water reactors like the CANDU. Given the estimated cost of processing, handling, transporting, and storing spent nuclear fuel from a once-through cycle–which is becoming nearly an order of magnitude more expensive than originally envisioned when many nuclear power plants were originally commissioned and licensed, this end-of-life cost difference is significant.
Thorium also appears to be relatively common in meteorites, and therefore, more readily available in space objects as a potential energy source. Again, the lack of enrichment makes it very attractive as a fuel that can be use in-situ with minimal processing, and can be stored until activation by a neutron source indefinitely. [sup]235[/sup]U fuel elements, on the other hand, require careful control and aging surveillance lest internal fission create defects that make the material more sensitive over periods of decades.
Although investing the money in developing this technology is an expensive proposition, the long-term benefits of thorium technology are dramatic, which is why nations that are dependent on nuclear technology to sustain growth (e,g, China, India, Japan) are putting research into thorium as a fuel. The United States and the European Union would be well-advised to participate in this research and ensure that if energy needs and uranium cost skyrocket we have a viable alternative.
Stranger
That guy, is what we call in technical parlance, “a fuckin’ moron.”
Stranger
This thread reminded me of an agreeable Fifties space yarn which I knew as Assignment in Space with Rip Foster but which was first released as Rip Foster Rides the Gray Planet. The titular hero is a space marine who is given a small detachment and ordered to bring a thorium asteroid back to Earth orbit, which he duly does while fighting off dirty [del]Commies[/del] Connies along the way. In the near-ish future setting, the good guys’ spaceships are powered by thorium, which also serves as a peacetime power source Earthside, while the totalitarian bad guys are still reliant on chemical rockets which, however, can still zip about the solar system at a tidy pace. I was delighted to find the full text free on Gutenberg and enjoyed rereading something I last read when I was nine or ten. 
Letter to the editor in today’s Globe and Mail:
For the non-technical types: fuckin’ in this case means huge, not that the guy had a chance of getting laid.
But isn’t it possible to build a bomb from U-233 alone? I’m not sure if it has ever been done before. (One of the Operation Teapot devices that the US tested in the 1950s used a combination of U-233 and Pu-239).
Is U-233 not a realistic proliferation risk? It is said to be more technically difficult than using U-235 or Pu-239. My understanding is that the main issue is unavoidable contamination with U-232, whose decay products are strong sources of gamma radiation and hence dangerous to workers. Are there other serious difficulties? I could imagine a country like Burma considering their workers to be disposable, or a country like Saudi Arabia having the wherewithal to work with the material remotely.
The essential problem with using [sup]233[/sup]U is that while it can be chemically separated from the [sup]232[/sup]Th, it cannot be chemically separated from [sup]232[/sup]U, which as you note is a highly energetic gamma and alpha emitter. This is not just a personnel hazard (the alphas are obviously easily shielded, but the gammas are highly penetrating and would require remote processing as personnel would be overcome by radiation sickness after more than a brief exposure) but also one to electronics and initiators in a weapon, which could not be effectively protected for any significant duration. The very properties that make [sup]232[/sup]Th good as a starting material for a molten salt reactor make it very poor as the basis for developing weapon grade nuclear material.
Stranger
Just so I’m clear the Anon poster here is full of it?
You might want to consider posting something that doesn’t require you to log in to facebook and what looks like adding an app to your facebook page.
Belated thanks for posting this!! I had a copy back in the '60s, and have several times in the last couple decades tried to find out the title so I could read it again. It was the first thing I thought of when I saw this thread this evening. 8)