Australia has the largest proven reserve of Thorium ore.

Metallic Th decays to radon gas, so a big source of occupational hazard exists unless kept as a salt.

well thats all well and good, but were are we going to get our depleted uranium rounds from if we switch to thorium?

Metallic Th decays to radon gas, so a big source of occupational hazard exists unless kept as a salt.

Yes, thorium will decay in a chain that includes radon-220, but radon-220 only has a half-life of 55 seconds, so it can't "mobilize" in time to get in your lungs and do damage during the rest of its decay. The real radon risk is radon-222, which has a half-life of nearly 4 days and comes from the decay of U-238. Radon-222 has 4 days to move around and get breathed in and cause problems.

Plus the half-life of thorium is three times longer than U-238, so less thorium is decaying in the first place.

But all these radon concerns don't make any difference in which fuel cycle you should use in your reactor.

Thanks for the comment, Kirk. Good to have you here.

so, as was discussed previously on treehugger, the only really good reason to use uranium would have been to make nuclear wepons.

Thorium doesn't work so well for that, however uranium is perfect.

and Thorium reserves compared to Uraniums reserves?

and Thorium reserves compared to Uraniums reserves?

At 10 parts per million, thorium's roughly four times more common than uranium (2.5 ppm) in the Earth's crust. More common than samarium (7 ppm), gadolinium (6 ppm), boron (3 ppm), bromine (3 ppm), uranium (2.5 ppm), beryllium (2 ppm), tin (1.5 ppm), tungsten (1 ppm), molybdenum (1 ppm), mercury (0.2 ppm), silver (0.1 ppm), platinum (0.005 ppm), and gold (0.002 ppm).

At the rate it would be consumed in a fluoride reactor there's enough to power the world for tens of thousands of years. Then if we need more we can mine the Moon or asteroids--they all have it too.

The serious issues associated with Uranium storage aren't Uranium or Plutonium (in spite of the scare mongers words). The Fission Products of Uranium decay off fairly rapidly (in the couple Hundred of years realm) just as Thoriums do.

The real issue is that Nuclear Power is scary. I can explain many aspects of Nuclear Energy, but it takes quite a while to explain even simple things. Explaining more complicated things like the Life Cycle of a Neutron to people with no background in math or science, and I am guaranteed to have someone fall asleep. This doesn't keep me from trying, I just work hard to get them to stay awake.

For me to promote Nuclear Power, I have to be honest (Eagle Scout issues). Those who oppose Nuclear Power just have to appeal to terror.

Thorium is an excellent resource for us to leverage. It may overall be "cleaner." Nuclear power is in general already really clean. 40 years of "waste" is being stored on site at many Nuclear facilities. A typical coal plant can't keep its waste on site for more than 40 hours. The accumulated radiological material in that coal ash is greater than what will be stored at yucca mountain. They forget to teach you in school that radioactivity is everywhere. The amount of Uranium sent through the system at just about any given Coal Facility has the equivalent heat energy of the coal that was burned.

There's a scary thought.

I should also add that since uranium-235 only constitutes 0.7% of natural uranium, and that since practically every reactor in the world today uses U-235 as its basic fuel, a more accurate comparison would be to compare thorium at 10 ppm to U-235 at 0.018 ppm.

The serious issues associated with Uranium storage aren't Uranium or Plutonium (in spite of the scare mongers words). The Fission Products of Uranium decay off fairly rapidly (in the couple Hundred of years realm) just as Thoriums do.

You're absolutely right about the fission products--they go away after a few hundred years whether you're using uranium or thorium. The salient difference between the two is that a thorium fuel cycle has the potential to produce energy without producing long-lived transuranics, whereas a uranium fuel cycle will inevitably form transuranics. In a thermal-spectrum uranium reactor, these transuranics will accumulate rather than being consumed over time due to their unfavorable neutronic properties (they don't fission often enough and produce enough neutrons per absorption).

The real issue is that Nuclear Power is scary. For me to promote Nuclear Power, I have to be honest (Eagle Scout issues). Those who oppose Nuclear Power just have to appeal to terror.

Boy, you are absolutely right about this. Understanding the potential and issues of nuclear energy takes time and mental effort. Getting scared and screaming "no nukes" is easy by comparison.

Thorium is an excellent resource for us to leverage. It may overall be "cleaner." Nuclear power is in general already really clean. 40 years of "waste" is being stored on site at many Nuclear facilities. A typical coal plant can't keep its waste on site for more than 40 hours. The accumulated radiological material in that coal ash is greater than what will be stored at yucca mountain. They forget to teach you in school that radioactivity is everywhere. The amount of Uranium sent through the system at just about any given Coal Facility has the equivalent heat energy of the coal that was burned.

Again you are correct. All the spent nuclear fuel in the world would not occupy a great deal of volume. The issue we have today is that the nature of this spent nuclear fuel, and the lifetime of the transuranic isotopes they contain, lead to a level of regulation and protection that is very...significant.

The costs of Yucca Mountain have a great deal to do with establishing the geological stability of the site for tens of thousands of years. There is little question that Yucca Mountain and a host of other sites will be stable for a few hundred years. Being able to dial down the lifetime of nuclear waste to a few hundred years, and at the same time reducing the volume of that waste by a factor of ten or more, is very compelling.

So, the question is: Why aren't we currently using these kinda of reactors? Obviously the know-how has been around for a while. There must be some reason that you're over-looking that makes it less feasible to build and maintain a thorium - uranium 233 reactor?

... Or did I read the article too fast?

The reason governments focused on uranium and plutonium is because what they really wanted was the ability to make bombs. Under cover of 'dual use' technology they built infrastructure claiming it was for peaceful power generation and that the big rockets were for civilian space exploration and development.

US, USSR, China, France, UK, basically everyone did it. And it's also why it's so clear that Iran wants bombs. If they didn't, they would use thorium because it's better in every way except making bombs. Not to meantion they still have all that oil.

Anyway, India's been using thorium for years in actual production reactors. They converted existing uranium reactors to use thorium jackets.

I think we use uranium because the tech was left over from bomb production, that's only a guess though. Not only should thorium be researched, India is leading there. So should generation IV reactors, specifically the integral fast reactor. It's interesting if you want to believe this

Compared to current light-water reactors with a once-through fuel cycle that uses less than 1% of the energy in the uranium, the IFR has a very efficient (99.5% usage) fuel cycle. The basic scheme used electrolytic separation to remove transuranics and actinides from the wastes and concentrate them. These concentrated fuels were then reformed, on site, into new fuel elements....Another important benefit of removing the long half-life transuranics from the waste cycle is that the remaining waste becomes a much shorter-term hazard. After the actinides and transuranics are removed from the spent fuel, the remaining waste elements have half lives of a few decades at most. The result is that within 300 years, such wastes are no more radioactive than the ores of natural radioactive elements.

From http://en.wikipedia.org/wiki/Integral_fast_reactor

How you compare the safety of a Thorium reactor to that of the fail-safe Pebble Bed reactor? PBR's use U-235 or U-238 (forget which), but are designed to fail safe, and are not capable of spreading radiation from a coolant leak, since they use helium as the coolant.

You still have the Uranium waste, but it is embedded in glass, and is at relatively low levels there. The glass beads can be recycled too, to the best of my knowledge.

What is also remarkable about the molten salt thorium reactor is that it is a breeder reactor*, meaning practically that it is very fuel efficient.
One container having 30 t of thorium could power a gigawatt-class power plant for 30 years.

Think about it, one container, 30 years of power!

A powerplant producing as much energy as current nuclear powerplants.

*: Those who know the many problems with solid Uranium 238 breeder reactors need not worry here, we can use thermal spectrum and continuous reprocessing to get breeding with Thorium.

U233 is even more rare than U235. In a Th scheme the U233 will have to be produced in place by neutron absorption by Th232. Where do you get the fuel to initiate the reaction? Where do the neutrons come from for transmuting Th232 to U233?

As to the comment about the pebble bed: Why not use Th-U fuel in the pebble bed instead? Probably no reason you can't...

Radiation from Coal plants, by the way, cannot be regulated because it is "natural"...

U233 is even more rare than U235. In a Th scheme the U233 will have to be produced in place by neutron absorption by Th232. Where do you get the fuel to initiate the reaction? Where do the neutrons come from for transmuting Th232 to U233?

U-233 is much more rare than U-235--it doesn't occur in nature at all! To start the reactor, there are many options. The best is to start on U-233. Each 1000 MWe reactor will take about 1000-1500 kg of U-233 to start, and there's only about 1000 kg of the stuff in the world, and unfortunately they're trying to throw it away! So that won't get us far.

We could use highly-enriched U-235 to start the reactor, and that would work well and help eliminate the stocks of this material, which accumulated during the Cold War.

We could also use plutonium from reactors or decommissed weapons to start the thorium reactors, but in many ways this is the worst option since it forms some transuranics in the fuel, and we're trying to get rid of these. But it does destroy any weapons value of the plutonium.

My favorite option would be to build a few chloride reactors. These reactors have a fast spectrum and can totally destroy transuranic elements like plutonium. They also make a lot of neutrons which can be directed to thorium to make U-233. This way, we destroy the long-lived waste we've already produced and produce new fuel to start reactors that won't produce transuranic waste. There's enough transuranic waste from 50 years of running uranium-fueled reactors to keep chloride reactors busy for awhile. And once you start each fluoride reactors, it doesn't require any more U-233, only thorium.

As to the comment about the pebble bed: Why not use Th-U fuel in the pebble bed instead? Probably no reason you can't...

Actually, using thorium fuel in gas-cooled reactors like the pebble-bed has been the plan for many years. The THTR was a thorium-fueled pebble-bed reactor that ran in Germany. One problem with solid-fueled reactors that run on thorium is that it is difficult to reprocess the fuel and extract protactinium-233, which is the intermediate product between thorium and uranium. Without the ability to isolate Pa-233, it can get "cooked" by the neutrons before it can decay to U-233. That drives you to a reactor with a low core power density, which is less economical. Pebbles as a fuel form have even more difficulty because their carbide coatings make them nearly impossible to reprocess.

Radiation from Coal plants, by the way, cannot be regulated because it is "natural"...

Pity....ionizing radiation does damage whether it's natural or not. Something to think about if you live in Boulder or take lots of jet flights.

From http://www.uic.com.au/nip67.htm:

"Developing a thorium-based fuel cycle

Problems include the high cost of fuel fabrication due partly to the high radioactivity of U-233 which is always contaminated with traces of U-232 (69 year half life but whose daughter products such as thallium-208 are strong gamma emitters with very short half lives); the similar problems in recycling thorium due to highly radioactive Th-228 (an alpha emitter with 2 year half life), some weapons proliferation risk of U-233 (if it could be separated on its own); and the technical problems (not yet satisfactorily solved) in reprocessing. Much development work is still required before the thorium fuel cycle can be commercialised, and the effort required seems unlikely while (or where) abundant uranium is available."

Those problems are specific to a thorium reactor using solid fuel. By using a liquid-fluoride fuel, there is no fuel fabrication, and the radioactivity from the U-232 contaminant is a strong deterrent for making weapons. Unlike solid thorium oxide fuel, it is easy to separate uranium from thorium in a fluoride form--simply fluorinate it to gaseous uranium hexafluoride. This is why coupling the use of thorium to a liquid-fluoride reactor is so advantageous.

At the rate it would be consumed in a fluoride reactor there's enough to power the world for tens of thousands of years.

Let's assume thorium (at least given future technology) can be economically extracted from "generic" crust (no more than average concentration)

10 ppm concentration = 10^(-8)

assume we can extract the thorium down to say, 30 m depth.

that's about 100 t of stuff / m^2, or 1 kg of thorium /m^2, which is 1000 t/ km^2 of thorium down to 30 m

Earth has a land surface area of 148 million km^2, assume that the areas we can extract thorium from contain equivalent thorium as 100 million km^2 of average concentration crust. That makes 100 billion tonnes of extractable thorium.

Assume 1 GW*yr per tonne of thorium. (Kirk Sorensen gives a figure slightly better here*). So, 100 billion GW years.

The number of hours in a year is 24*365.25=8766

Earths total electricity consumption is about 16 trillion kWh per year, or less than 2 billion kW years per year. Assume growth to 10 billion kW years per year = 10 thousand GW years per year.

That gives us 10 million years of power, a lot more than tens of thousands. Actually, I'm surprised it's so low, though I could have gottten a better figure by assuming deeper mining. (eg. assuming mining to 3 km, you get a billion years. it might not actually be necessary to mine at anything like that depth since over geological timescales new rock will be exposed by natural processes)

Of course, I suppose some treehugger readers might be alarmed at the idea of strip mining that much of the Earth's surface, but it would be spread out over a long time period - plenty of time for environmental recovery.

Now you may be wondering (I certainly am) how realistic it is to assume that such low concentrations can be profitably extracted. A brief googling suggests that surface quarrying costs 7-9 australian dollars/ t, so ignoring (for now) processing costs, that amounts to about US$600 000/t of thorium at 10 ppm.

Let's assume conservatively that fuel costs must be under 1 cent per kWh for thorium reactors to be economic. That's $87 660 000 per GW*yr, or about $100 million per tonne of thorium. So it seems that the cost of extracting the material from the surface is negligible (which in turn suggests the cost increases of deep mining will be tolerable). The only question is how much will it cost to process the material to get pure thorium.

I'll assume that the processing cost is the same as for uranium ore, and proportional to the dilution. Googling turns up a proposed uranium mining project "Crocker Well" with an estimated processing cost of $12.79/lb U3O8 for 0.05% concentration ore. I'll ignore the atomic mass of the oxygen. 10ppm = 50 000 times more dilute, so that would make it $640 000 per lb = $1.4 billion dollars per tonne of thorium.

Uh oh.

Well, technology advance will reduce processing costs and the assumption that we need fuel costs less than 1 cent per kWhr was conservative.

And even if it turns out that average concentration thorium will never be economically recoverable, ores even a few times more concentrated definitely should be. So we'll still have enough for quite a long time - a lot longer than tens of thousands of years, I'm pretty sure.

*he gives a figure of 0.9 t of ThO2 per GW*year which is less than 0.8 t of pure thorium

Woah, made a couple of mistakes there. Or rather the same mistake twice.

10 ppm = 10^(-5) not 10^(-8). 10^(-8) would be 10 parts per billion not million.

But through most of the comment I treated 10 ppm correctly as 10^(-5) anyway. Then at the end, when I was comparing it to the 0.05% of a proposed uranium mine, I again made the mistake of treating it as 10^(-8). So in fact, it's not 50000 times less concentrated than that uranium deposit, but only 50 times. So my estimate of processing costs for 10 ppm concentration ore should be revised to only $1.4 million per tonne of thorium.

That means that the contribution to electricity costs from the cost of getting thorium fuel should be really small even once we have to mine concentrations lower than the overall average of the whole crust!

So it looks like we really have enough to last tens of millions of years at least, if not billions, even without any technological advances beyond the thorium breeder reactors themselves.

Simon, are you sure you're correct?
10 ppm concentration = 10^(-8)

1 ppm = 10^-6 so 10 ppm is 10^-5

Anyway, your 1000 t / km^2 seems right. So if we assume GWy/t we get 1000 GWy/km^2.
And since current energy production is 2000 GWy / y, we extrapolate 10,000 GWy / y.
So 10 km^2 would be scavenged per year. Or 1000 hectares. To produce 10,000 t of Th.

If we think about the volume, it'd be 0.3 cubic kilometers per year or 300 million cubic meters.

Compare to USA coal usage of 1998, 1000 million t (http://energy.cr.usgs.gov/energy/stats_ctry/Stat1.html) or 750 million cubic meters, 0.75 cubic kilometers.

Just to summarize the comments.

Thorium is indeed safer than uranium and we have known this since at least 1960. Thorium used in a flouride-salt reactor burns trans-uranics (nuclear waste to most folks) in process and does not have nasty reprocessing by-products like fuel-rod waste.

There is sufficient thorium available to power more or less everything for a long, long time.

Somebody thinks pebble-bed reactors are great. Somebody else pointed out that they toss most of the fuel as waste.

Thorium reactors are not very usefull for making bombs.

Somebody pointed out that the once-through uranium fuel cycle is ideal for making fuel for nuclear weapons.

Nuclear reactors are scary to most people.

My $.02 ...

The US has been suckered into two wars in Iraq premised on the ficticious threat that Saddam Hussein was about to make nuclear bombs. There are some who would like to sucker us into a war with Iran based upon this same premise.

The nuclear powers-that-be in the US have known about thorium reactors and molten-salt reactors that can eat atomic waste since at the latest, 1970. Thirty seven years later there is not one molten-salt reactor operable. Not even a test-bed unit.

If anybody thinks that people who have been lied to about nuclear waste and nuclear weapons for 37 years are suddenly going to start believing nuclear power is safe and cheap well....I've got a bridge to sell them.