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Thorium

rein.pk

345 pointspkrein110 comments

> but thorium reactors have been pretty experimental

Not all thorium reactors. A good example for an industrial grade thorium reactor is the thtr-300 a high temperature thorium pebble bed reactor (http://en.wikipedia.org/wiki/THTR-300)

> Thorium reactors are inherently stable, so “nuclear meltdowns” can’t happen.

This was also one reason for the design of the AVR in Jülich and it's successor the THTR-300. Although there wasn't any "nuclear meltdown", there were various other problems:

- Small amounts of water leaking into the primary cooling circuit. Bigger amounts could have lead to a buildup of hydrogen and oxygen which can cause explosions. This is very comparable to a meltdown

- The pebbles proved to be not very stable. This lead to a bigger amount of radioactive matter being released into the surrounding environment by the THTR-300

- The AVR leaked a big amount of radioactive matter into the ground water

- various other problems

Newer thorium reactor types won't have these problems because they will be considered in their designs, but there's still the problem with the timeframe. Estimates are that 2030 is the time when Gen IV reactors will get rolled out (http://en.wikipedia.org/wiki/Generation_IV_reactor). Meanwhile Germany replaced 3.5% of it's electric power sources from 2010 to 2011 with renewable ones.

I think Germany replaced a lot more than 3.5% with renewable energy.

http://cleantechnica.com/2012/07/26/germany-26-of-electricit...

One of you talks about absolute numbers, the other about % change. I don't have any numbers easily at hand but you might both be correct.

I've seen several thorium-boosting articles like this, and none of them say why research and industrial development selected for uranium over thorium. Is it just because the initial research into power came out of weapons research?

It's really, really complicated, since nearly all R&D came from huge government funding and that means politics.

A lot of it is that it came out of weapons research, and u-235 and Pu-239 were well understood from weapons research.

[edit] Also, plutonium fast breeder reactors looked very attractive in the '50s since they could use U-238, with just Plutonium feedstock, and also produced material usable for weapons. It turned out that 1) it's Not That Easy and 2) we don't need more atomic weapons.

>> we don't need more atomic weapons

Speak for yourself, the Pentagon, UK, France, Russia, China, India, Pakistan, Israel, North Korea, possibly others still replacing and/or building tons of those.

Partially. Also, the first really "working" nuclear reactor was built for a submarine. However, every modern nuclear reactor uses essentially the same design. This has resulted in some...idiosyncrasies in this design.

Yup. One of the good things about the light water reactors that everybody uses is that you can make them relatively small. That's a big deal when you're deciding what sort of reactor to put on a submarine. And then everybody who knew how to make a nuclear power plant only knew how to make a light water reactor, and then lock-in happened.

The other obvious advantage to having a light water reactor on a submarine is that water is something you can easily find a lot of out in the ocean.

The other obvious advantage to having a light water reactor on a submarine is that water is something you can easily find a lot of out in the ocean.

Well, you have to at least de-salinate the water and filter it before you use it in the reactor. If, in an emergency, you need to pump in salt water, you're going to ruin the equipment via corrosion.

The movie 'K-19 The Widowmaker' got into this a bit.

  If, in an emergency, you need to pump in salt water,
  you're going to ruin the equipment via corrosion.

Well, yeah, but is that any worse than if you have a different reactor design? Considering that, in a meltdown scenario, corroded equipment is not your biggest problem, it seems you would want to at least have the option. But most of what I know about subs comes from reading "The Hunt for Red October".

That's true only if you needed to replace water in the primary loop, but that's not likely. Seawater is only in the 3rd outer condenser loop in a PWR design.

Liquid Fluoride Thorium Reactors were based on a design for an AIRCRAFT reactor! Talk about having to be SMALL! :)

That's not really true, is a huge difference between using Sodium vs Lead vs light water vs heavy water vs gas for the primary coolant loop.

http://en.wikipedia.org/wiki/Heavy_water_reactor

http://en.wikipedia.org/wiki/Light_water_reactor

http://en.wikipedia.org/wiki/Liquid_metal_cooled_reactor

http://en.wikipedia.org/wiki/Lead-cooled_fast_reactor

http://en.wikipedia.org/wiki/Gas-cooled_reactor

The real link has a lot more to due with how cheap uranium was to mine / refine and how much refined uranium was needed for weapons programs. At this point we could stop all uranium mining for the next 50+ years without any problems and by changing designs that could stretch out to something like 1000 years. Fuel is simply not the problem.

the initial research being for weapons is probably part of it, though uranium-233 (from thorium) was used during a 1955 nuclear bomb test. [1]

thorium reactors are also "breeder" reactors. they initially require an external source of neutrons to start the reaction, then the thorium breeds into uranium-233 and the reaction can become self-sustaining. so thorium by itself is actually an impossible place to start.

[1] http://en.wikipedia.org/wiki/Uranium-233

Good point; compare to the first 5 US reactors, the Chicago Pile and the plutonium breeding Oak Ridge X-10, and Hanford B, D and F reactors. All graphite moderated (very pure graphite, BTW, something the Nazi's couldn't get), all using natural, as in unenriched uranium (at least initially). That was obviously handy for bootstrapping prior to enough Highly Enriched Uranium (HUE, mostly U-235) being available from Oak Ridge's separation plants, which I gather the first major use of was for the Little Boy gun assembly bomb.

That initial charge can be the Trans-Uranics (TRUs) from spent nuclear fuel. That way we can transition into the Thorium Age while cleaning up after the Uranium Flirtation! ;)

Long story short.

For breeder reactors getting neutron balance on to critical level is very challenging. You need one neutron to breed fertile material into fissile and another neutron to split the fissile nucleus. Usually 2-2.5 neutrons are released in fissions of U-235, U-233 (bred from thorium-232) or U-239 (bred from U-239), but some of the neutrons are absorbed by other materials in reactor, some other neutrons are leaked out from the reactor core etc. I would say this is the main reason, why breeder reactors are not common.

U-235 is the only fissile isotope available on earth so it was a natural choice for power generation.

Thorium in a LFTR breeds almost as well in a stable thermal spectrum reactor as U238 does in a twitchy fast spectrum reactor. And a LFTR doesn't have nearly the neutron loss mechanisms that solid fuel reactors typically do.

One reason also very much overlooked is that the entire nuclear industry makes the majority of its money from fuel fabrication. Making the bundles of fuel rods for PWRs and BWRs is a recurring, reliable source of income for the lifetime of the plant and any innovation into thorium or other models would take away that cash cow.

To clarify your point: utilities aren't usually in the fuel fabrication business, but some engineering firms are, like Westinghouse. They provide the designs, expertise during and after construction and fuel. And there's only a couple of vendors, so if you want to open up a nuclear power plant it's on their terms.

Yes. You're right. Utilities are told by the regulations to pay the engineering firms so that they can operate. I wish they had more choice other then the big ones but no one seems to be able to enter the market.

That's true that thorium would upend the ceramic uranium pellet market if if was a prevalent design, but it's not. The fuel fabrication business is tiny compared to most other segments of the energy market. It's probably not even the main revenue stream for a company like Areva. Remember, the nuclear industry is not a vertical industry like oil that takes the product from the ground to the service pump. It's a scattering of smaller service companies, small mining companies, and construction that are dwarfed in size in comparison to fossil fuel companies.

There is a Google Tech Talk on this very subject by Kirk Sorensen. He's a big thorium proponent so apply salt as you see fit but his talk seems fairly well cited.

http://www.youtube.com/watch?v=bbyr7jZOllI

This is only one of MANY good presentations by Sorenson and others on LFTRs and what we can do with them.

I'm not in the industry, but I believe uranium reactors produce plutonium as a byproduct. Plutonium is useful to make bombs.

Not reactor grade plutonium. Creating a pure Pu239 product depends on a specialized Pu239 production reactor with special methods. Extracting a pure Pu239 product from used reactor fuel would not be an attractive option for making a bomb. Not when you can produce a better product with a better/different method.

The same type of reactor can be used to make weapons grade Plutonium. Just ask Iran why they removed a fuel bundle from one of their reactors after just a few weeks rather than years.

One thing thorium proponents tend to omit is that there was a German thorium reactor which was considered to be in regular service (i.e., non-experimental). It suffered an incident and was shutdown several years thereafter as the costs of dealing with the incident and ensuring safety overwhelmed the operating company and forced it to seek a government bailout.

So there is some negative experience with Thorium. And the Germans are not willing to try again. Since the Germans that designed that reactor have the most experience with Thorium, and they are not trying again this should give a bit of a pause for others.

However, China is licensing those German designs and will try similar reactors in the coming years so we will see how that goes.

See :

http://en.wikipedia.org/wiki/THTR-300

http://en.wikipedia.org/wiki/Pebble_bed_reactor#Thorium_High...

Thorium has issues in a solid fuel reactor. The LFTR is the way to go.

It can not be stress enough that the reactor must be a molten salt reactor. The molten salt provides the stability, safety, and efficiency gains that a normal light water reactor can NOT match.

There are numerous different reasons. Thorium proponents often gloss over a lot of the difficulties of the system, leading to a false sense of how easy it would be to make such reactors. One of the biggest problems is that a Thorium reactor is actually a U-233 reactor, which is bred from the Thorium, and U-233 is not so easy to work with. It emits a huge amount of gamma radiation, which is highly penetrating and dangerous for human life.

To work with U-235 or Plutonium you only need a glove box, but to work with U-233 you cannot have humans physically close to the material, you need waldos and closed circuit cameras and so forth. This naturally increases the cost of working with the fuel. But wait, it gets worse. As I said, gamma radiation is highly penetrating and heavily ionizing, which means that it damages delicate materials quite easily. Especially seals, made out of rubber or silicone or what-have-you, and electronics. This makes fuel cycle handling hugely challenging and also makes reactor construction rather challenging as well.

Now, likely we could overcome these problems but they are nevertheless huge problems.

One of the big reasons why Uranium/Plutonium reactors have caught on is because you can use 1950s technology to build reactors and process fuel. That's not the case with Thorium/U-233.

This pretty much nails it, that is why things have to be very different with Thorium and the combination "very different" and "nuclear" leads to an over abundance of caution.

One of the reasons the travelling wave reactor is "interesting" is that starts and ends with 'low grade' radioactive material, and works very much like a 'brushfire' which burns fuel ahead of it and leaves behind fully utilized fuel. The downside is that it doesn't really "stop" in the sense that you start one of these candles burning and for the most part it goes 10 years and then sputters out, you can harvest the energy or not but you can't really turn it off. (at least not in the early designs)

So much of the engineering issues with Thorium are mastering the fuel cycle and that is something the US DoE hasn't spent a whole lot of time investigating. Its an interesting question what we could do with a 1950's attitude toward researching nuclear power uses and 2010's level of technology.

LFTRs are not all that difficult. It is a WHOLE lot simpler than a Traveling Wave reactor!

We have different definitions of "difficult" I suspect.

The Thorium fuel cycle produces U232, that stuff kills at a distance, through walls. What that means is that there are a number of scenarios, one of which Fukishima just went through, where the core gets uncovered and rather than leaking Cesium it shoots gamma rays everywhere killing anything trying to get near it. That is not the case with the U238 fuel cycle.

Not saying it can't be dealt with, just saying its different, and by being different it is dangerous in different ways.

"The Thorium fuel produces U232..." Yup, which is one of its nicest features. It means that the U233 is unlikely to be used for weapons. And since it never leaves the well shielded containment area in a LFTR, there is no hazard.

If the kettle is breached in the LFTR, the salt will probably just condense on any small break and seal it. If the break is large, the salt drains into a drain tank which is still in the shielded containment volume. No worries, mate! Oh, and since there is no significant pressure and no volatile chemicals like liquid sodium, there are no forces trying to disperse the materials. Inherently MUCH safer than any PWR or LMFR.

Has anyone considered using molten lead as a "seal"? I imagine you could reduce the number of places that need seals and then have it set up so that everything that needs to get into the sealed box passes through a small pool of lead that is kept molten. So long as everything around the lead has a melting operating temperature tolerance greater than 621 F it should be able to function through a molten lead seal.

Thorium is kind of like diesel, it doesn't work well in a spark ignition engine. Thorium doesn't work very well in a solid fuel reactor. Liquid Fluoride Thorium Reactors (LFTRs, pronounced "lifters") on the other hand work very nicely. All the "reasons" you mention apply to solid fuel reactors, not LFTRs. The man who invented both preferred the LFTR.

It's not the U-233 itself that emits gamma, but the U-232 it tends to be contaminated with. This can be avoided by chemically separating protactinium during the decay chain from thorium, but the U-232 is often considered desirable as a anti-proliferation measure.

By using liquid fuel and transmuting in place, you never handle U-233, contaminated or not. After reactor startup (which requires a good neutron source), you just keep feeding more thorium to the reactor and removing fission products.

Really, the greatest reason has to do with organizational momentum. Think of how office politics work when different groups have competing ideas for the same solution. Those with expertise and time invested into their way are going to protect and defend their turf. Thorium lost that battle.

The argument that it wasn't good for weapons integration doesn't hold water as a commercial power reactor would not be used in that fashion at all. The DOE's production of plutonium 239 comes from specialized irradiated u238 rods exposed for 4 weeks or so - totally different production method and process that a PWR power reactor would use.

Not only is thorium much more plentiful than Uranium, creating demand for thorium also solves diffuses the Chinese economic control of rare earth metals. Rare earths are plentiful in monazite sands as well as thorium and are available in the US. Right now, thorium is a radioactive byproduct that largely prevents economic extraction of rare earths. Build good thorium reactors in the US, and both energy and rare earth situations are alleviated.

The rare earth situation has already been solved. Mining has restarted in the US and US will likely be self-sufficient in REE in 2 years.

Do you have any citations? I'm not trying to nitpick, I am just interested in reading more.

I was also curious, so I did some digging and found this article:

http://www.sfgate.com/opinion/article/U-S-rare-earth-mine-re...

Also Europe could be somewhat self-sufficient in REE with just one new project (Norra Karr mine in Sweden).

Which just means there will be a lot of free fuel available!

Here's an introductory video (10 mins) http://www.youtube.com/watch?v=N2vzotsvvkw a longer video http://thoriumremix.com/2011/ (the surrounding links are worth exploring) and a summary http://cybercemetery.unt.edu/archive/brc/20120621060336/http... The important point to get is that the excitement is not just "thorium" (as the title of the thread suggests) but the reactor as well.

This seems to be an update on the Norway story at the end:

http://singularityhub.com/2012/12/11/norway-begins-four-year...

And how come he didn't even mention LFTR?

http://en.wikipedia.org/wiki/Liquid_fluoride_thorium_reactor

LFTR are a type of molten salt reactor, which is mentioned, though certainly not given enough attention in this first short article ;) will see what i can do.

Are there serious arguments against Thorium? Or is it just early stage waiting to be a bit more experimented with before going mainstream?

yes. a recent nature article pointed out how thorium can be used to make uranium-233 which can be used to make nuclear weapons.[1] (see the conclusions section at the end of the article)

here's a more detailed explanation: the "old" idea before this nature article was that the uranium-233 produced in thorium reactors would be inevitably mixed with uranium-232 (which isn't useful for making bombs). but the nature article pointed out that the real decay path is thorium-233 --> protactinium-233 --> (uranium-232 AND uranium-233), and that by separating the protactinium-233 from the thorium reactor's neutron flux after 1 month, you can ensure that the protactinium-233 converts to uranium-233 instead of uranium-232.[2] ... step 3 you can make a weapon.

[1] http://www.nature.com/nature/journal/v492/n7427/full/492031a... (sorry for the paywall :( ) [2] http://en.wikipedia.org/wiki/Thorium_fuel_cycle

But this isn't practical in reality. First of all, you need a core of U-233 to start the process but once you start you're adding thorium at different points in time so the fuel slurry is going to be always a mix of thorium, protactinium, u-232, u-233 and other various products which makes extracting anything a royal pain. There's much easier ways of isolating weapons grade uranium instead of trying to extract it from a ongoing fuel process.

The question isn't whether there are easier ways of producing, but whether the thorium reactor doesn't provide better concealment for producing what would bring unwanted attention when done in the 'easier' way.

If you're trying to conceal what you're doing, it would be best by far to avoid U-232 being involved in the process.

1) If you take away Uranium from a thorium reactor you will rather quickly lose criticality, so you won't be making any new protactinium. Thorium breeders run very close to steady state, and only make a very small fraction of fuel more then they need.

2) I'm pretty sure there is a rare reaction that you will get protactinium-232, which has a much shorter half life the protactinium-233 (about a day instead of about a month) but it can't be chemically separated. It will decay to U-232.

The nature article is alarmist, and not practical. It would only make sense if you had a separate neutron source that was not a thorium breeder, and probably will still have a good amount of U-232. Since you have a neutron source (probably a light water reactor) why you wouldn't use the extremely well understood methods to make plutonium from U-238 is beyond me. You quite literally just need to put uranium metal in the neutron flux for 1 month and chemically separate out the plutonium. Much easier, if I was designing a nuclear weapons program I sure as hell wouldn't pick Thorium.

But that means that while thorium doesn't present an obstacle to state actors in acquiring nuclear weapons, it would considerably lower the risk of theft of non-polluted U-233 by non-state actors.

as far i understand, yes. the real nasty thing about uranium-232 is that it emits highly dangerous gamma radiation [1], which is extremely unhealthy==difficult==expensive to handle. if i understand correctly, the gamma radiation also makes it much easier to detect from afar, making stealth difficult.

[1] http://en.wikipedia.org/wiki/Isotopes_of_uranium#Uranium-232

It will also toast the electronics in your nuclear weapon, essentially making a weapon with a considerable enough portion of U-232 impossible.

It's only tangentially relevant that a given reactor type can be used to make nuclear weapons. Yes, it means that there are states on the planet that can't be trusted with them, so be it. But there are plenty of countries that already have nuclear weapons and/or are stable and transparent enough that they can be trusted to submit to inspections - these could start Thorium projects and the world wouldn't be worse off on the proliferation front for.

Also, any fission reactor is a proliferation risk, because it will be a strong neutron source. Simply put hunks of natural Uranium around the core of your reactor and replace it on an appropriate schedule and you'll breed weapons-grade Plutonium which can be easily chemically extracted. It's just may not be as efficient as other methods.

FOLLOW THE NUMBERS!!!

U235 & Pu239 bombs extant ... ~20,000

U233 bombs extant ... ZERO

Seems pretty conclusive. It is MUCH easier to make bombs the way everyone always has than to put your lives on the line fiddling with U233.

The only really sustainable Thorium reactors would be if you could net positive U-233 production in one. This is somewhat challenging.

Also, the reactors that claim operational advantages against existing designs (particularly LFTR) are somewhat novel, which casts some doubt on their feasibility.

The operational advantages are definitely necessary for them to catch on, as this article points out, if you could get your fuel rods for free, you only save 14%.

Indeed. Uranium reactors are pushing the 4th generation, with unprecedented levels of safety and reliability in the reactor designs. Whereas LFTRs have yet to get to the 1st generation. The idea is certainly worthy of research, but the idea that we could be switch our base power to LFTRs in the next few decades is almost certainly a fantasy.

Thorium has significantly less delayed neutrons [1], which means that the reactor is closer to prompt criticality. In addition, browsing the relevant parts of wikipedia [2], there seem to be some problem with the neutron economy. And to start an reactor you need to breed some U 233 from Thorium first ( Which will alter the reaction of the reactor to a given neutron flux). Since the neutron flux in the reactor is the main variable which controls the power output it seems, that a Thorium reactor is significantly harder to control than a Uranium one.

[1] .6 delayed neutrons per 100 fissions for U233 compared to 1.6 for U235. http://www.reak.bme.hu/Wigner_Course/WignerManuals/Budapest/...

[2] Especially https://en.wikipedia.org/wiki/Liquid_fluoride_thorium_reacto...

I've heard this concern raised before, and the real question is whether the thermal expansion of the fuel salt acts as a strong enough negative coefficient of reactivity.

Answer, yes it does. This was proven in the Molten Salt Reactor Experiment.

"Since the neutron flux in the reactor is the main variable which controls the power output it seems, that a Thorium reactor is significantly harder to control than a Uranium one." This is nonsense. LFTRs are self controlling with a significant negative coefficient. It really makes no more sense to think about putting Thorium in a solid fuel reactor than it does about using diesel in a spark ignition engine.

Fun related trivia:

I just read Robert A. Heinlein's first "Heinlein juvenile" (i.e. young adult) novel Rocket Ship Galileo. It was published in 1947. The rocket ship's power plant was a nuclear reactor using... thorium.

Probably not the best choice for fuel, though. It takes around a month after capturing a neutron for thorium to become fissile, and if they just needed to get to the moon and back, a thorium breeder reactor isn't going to be too helpful with that. Highly enriched uranium is the way the NERVA guys went.

If they needed long-term power for a moon base, of course, it might be another story.

Above [1], someone pointed out that a thorium reactor would produce gamma radiation that is highly penetrating and heavily ionizing. Probably not the "roommate" you want in the small confines of a spaceship. :)

[1] https://news.ycombinator.com/item?id=4913976

Possibly Graphen coating of the metals could be used to solve the corrosion problem in molten salt Thorium reactors.

If we solve the corrosion problem we get cheap abundant energy with little to no nuclear waste and little to no material which can be used to make weapons of mass destruction.

http://www.gizmag.com/graphene-metal-corrosion/24434/

What corrosion issue? It has already been shown the a combination of adding one additional alloying element to the Hastalloy N while keeping the salt slightly fluorine poor will greatly reduce the already minimal corrosion issue.

A pretty good article overall but he seems to go off the rails when he starts talking about construction costs and assumes that a thorium reactor would cost the same as a uranium reactor. My understanding is that a thorium reactor should be dramatically cheaper for a variety of reasons (no need for a big containment bubble for one thing).

That is currently all speculative. We don't know how much it would cost to build a thorium reactor. There is strong evidence that it would be cheaper, but has yet to be demonstrated. To quote the article:

"Safety features of nuclear plants seem to dominate the cost. There are many claims about the inherent safety features of thorium Molten Salt Reactors. But those claims have yet to be proven in working prototypes. If thorium reactor designs and prototypes could prove the claims of inherent safety mechanisms, then thorium could dramatically reduce the cost of nuclear power."

Actually, there have been two working prototypes, one that ran without significant issue for about five full power years.

Oops, make that for two full power years over a period of five years. It was after all an experiment.

"Safety features of nuclear plants seem to dominate the cost. There are many claims about the inherent safety features of thorium Molten Salt Reactors. But those claims have yet to be proven in working prototypes." Actually, yes they have. The three main safety features have all been demonstrated.

First, the working fluid is non-volatile, no pressure nor chemical reactivity to drive dispersion of trapped gaseous fission products like Xenon and Iodine. Those were the two significant dispersed radionuclides in Fukushima.

Second, those same kind of radionuclides are removed from the salt continuously so there is not a store of them to BE dispersed.

Third, any loss of power to the reactor will passively result in a dump of the salt into a non-reactive tank where it will be passively cooled. It will be "walk away safe"!

This Nature article throws some cold water on the claims that thorium isn't very useful for making weapons.

http://www.nature.com/nature/journal/v492/n7427/full/492031a...

Unfortunately the article is paywalled.

That Nature article was also linked in the original article. See point 3 towards the end.

U233 more readily fizzes than booms, since it fissions faster it tends to pre-explode before getting into a really good super critcal state (probably something to do with the .6 instead of 1.6 delayed neutrons per 100 fissions mentioned above, it also has a slightly better neutron production factor than u-235).

U233 will have U232, which decays through some very high energy gamma emitters, making U233 impossible to smuggle through shipping ports etc... These gamma emissions also kill humans in minutes, so would-be bomb makers would need to use robots or other remote handling techniques to fabricate a bomb. This is something a rouge state would have a hard time pulling off, and is practically out of reach of basic terrorists.

It's not impossible but it would be easier/cheaper to just mine/steal some natural uranium and build centrifuges. It's easy to make U233 from thorium and thorium is abundant, so, really, how would reactors make thorium/U233 more available to rouge states when they could basically make it themselves, and why would they choose the U233 route?

Do you have an email address?

Scorecard

Uranium derived bombs extant ~20,000

Thorium derived bombs extant =ZERO.

The US & USSR would have been making Thorium derived weapons if it were practical. We DIDN'T. That should tell you something.

I took a nuclear engineering class in 1975. In essence we discussed three reactor design ideas:

1. Water, pressurized or otherwise. 2. Gas-cooled. 3. Molten-salt.

The big problem with molten salt was that you sent it through a whole lot of pipes. Hence, the physical plant that would get radioactive was much bigger than just the core of a water-based reactor. Also, you just had to deal with a whole lot of radioactive sludge.

A huge advantage was that the thing couldn't lose coolant and melt down; a catastrophic failure would amount to the molten salt sinking into the earth below.

It seemed at the time that if any major change would be made, it would be to HTGRs -- high-temperature gas reactors. But it also seemed as if the true "best" idea was molten-salt.

Note well that you are reading an article by someone who doesn't know the difference between fission and fusion (he says that a uranium fission reaction can result in a "thermonuclear explosion").

mmmm, yes quite inaccurate on my part. apologies. of course... uranium fission was a critical part of the hydrogen bomb ;) will correct that thanks.

Here's a full, frank discussion of the use of thorium in a LFTR http://www.peakprosperity.com/podcast/79398/kirk-sorensen-de... The nice thing about this item is that there's a transcript. For example, "Why thorium, not uranium?" Well the technicalities are explained (thermal vs fast reactors).

I'd be much more comfortble seeing resources going to improving solar and wind power. Storage of waste is always going to cause massive issues.

Thorium reactors can burn our current nuclear waste store, reducing its volume by an order of magnitude and the duration of dangerous radioactivity to under 300 years.

300 years is still far too long. You simply cannot expect most organizations to survive that long and remain trustworthy. Apart from that the real costs would still be very high.

> 300 years is still far too long.

300 years is feasible from an engineering perspective while 300,000 years is not. We know how to build a storage facility that won't let materials leach into the water table for 300 years.

> You simply cannot expect most organizations to survive that long and remain trustworthy.

Not needed.

> Apart from that the real costs would still be very high.

We've already built buildings with the required longevity. You'll have to be more specific/give better support to your assertion.

> 300 years is feasible from an engineering perspective while 300,000 years is not.

Besides engineering, communication of that facility's purpose is also important. You don't want a fancy storage facility becoming a tourist destination in 100k years either. Barring a massive collapse - loss of global knowledge and societal progress scenario (asteroid impact, super volcano, whatever), there's a great chance of some version of our modern languages surviving and being mostly readable to somebody on Earth born in 2312.

Conveying the waste storage site's inherent danger to that person 300 years from now is fairly easy task for our current society; just as we have lots of things from 1712 that still exist and are still mostly comprehensible.

We simply can't fathom how we'll communicate danger to someone ~15x further into the future than the entirety that our current civilization has even existed. Look at how much trouble we had deciphering hieroglyphics and that was only 6,000 years ago. It may not even be humans that come across it 300,000 years from now.

The point is, we have a lot of nuclear waste right now that needs containment for 10,000 years. Put it through liquid thorium reactors (or integral fast reactors) and you reduce the amount of waste by a couple orders of magnitude, while reducing the timeframe to 300 years. Do you have a better plan for it?

France seems to do okay by recycling it.

Of course it's cheaper to just toss the old stuff somewhere and dig up fresh uranium.

300 years is still a lot better than 10,000+ [1]years we are currently looking at for spent uranium fuel. If we can use current supplies in the thorium reactor then we will benefit greatly because our power production will serve as waste management for current uranium waste reserves.

[1] http://www.aps.org/units/fps/newsletters/2006/january/articl...

not to mention our electronics waste stores [1] (Ctrl-F 'thorium')

http://www.motherjones.com/environment/2012/11/rare-earth-el...

Solar and Wind will never, ever produce 24x7 power in predictable and economic quantities. They have their place but baseload, constant and affordable power is still a challenge to be solved.

If you want to help raise public awareness of this issue, sign the petition on the We-The-People website to preserve U233 used to make LFTR reactors. http://wh.gov/5Rmc

More info can be found here http://thoriumpetition.com/

Could someone please open a kickstarter for a new thorium reactor design and construction?

I'll gladly contribute to the initial cost (probably billions) just to get a lifetime of free and CO2-efficient electricity.

Couldn't this way of funding bypass most "big firm" inefficiencies and legacy cruft, just as SpaceX did?

There's a non-profit to support development of LFTR here: https://www.facebook.com/EnergyFromThorium?ref=nf

If you are an American, another thing you can do is sign the petition to stop the destruction of the U233.

http://wh.gov/5Rmc

For those interested, here's a TEDx talk about liquid fluoride thorium reactors and how they could be used to power a moon colony:

http://www.youtube.com/watch?v=N2vzotsvvkw

Shouldn't one rather frame this debate not as "proponents vs opponents" but as "scientists trying to figure out what is actually the case and hopefully inventing better nuclear power in the process"?

Does anyone know how much less waste Thorium produces when used compared to Uranium? Both this article and Peter Thiel's linked article say "less", but neither are exact.

It's actually a bit hard to quantify. The true cost of radioactive waste is related to what type of radiation it emits (gamma? alpha particles?), how long-lived the radiation is i.e. it's half-life, and the actual quantity of that material that is produced per Watt. This triple-axis makes it a bit hard to quantify in simple terms, but the main idea behind thorium is that the waste has a significantly shorter half-life[1]. Depending on the exact reactor design, there may also be ways to reduce the quantity of secondary waste (like water that's been exposed to heavy neutron flux while transferring energy from nuclear core --> steam turbines).

[1] : http://www.forbes.com/sites/williampentland/2011/09/11/is-th...

The best way to think of it is since U-233 is so much easier to burn then U-235 is like tinder instead of lumber. It reduces to much less and burns thoroughly.

There's also the huge difference between solid fuel rods used in uranium-fueled nuclear reactors and the liquid fuel used in molten salt thorium reactors. Solid fuel rods break down beyond use after less than one percent of the fissile material has been consumed, at which point the entire reactor must be shut down and the fuel rods replaced. With molten salt reactors, the fuel is constantly being replenished and the waste removed during operation, allowing a much larger portion of the fissile material (up to 99%) to be consumed before being treated as waste.

http://en.wikipedia.org/wiki/Liquid_fluoride_thorium_reactor...

Offtopic: how did you get a .pk domain?

http://www.pknic.net.pk

There is a misconception about the waste from current reactors. In short, the waste is not waste (as in something useless to be discarded, disposed of). This is all explained in the long video linked in my first post so I'll not repeat it. So much so that two MIT students (and their Professors) have come up with the acronym WAMSR, Waste Annihilating MSR, http://web.mit.edu/nse/inaround/dewan-massie.html and started a company. http://transatomicpower.com/products.php The LFTR itself can also burn the waste from a conventional reactor. http://en.wikipedia.org/wiki/Liquid_fluoride_thorium_reactor (the item "Destruction of existing long lived nuclear wastes" in the "Advantages" section)

This infographic is a nice compact presentation http://imgur.com/pm4Ux

You have to understand a bit about the subject.

1. Current reactors have U-238 and U-235. U-238 turns into Plutonium and some of that fissions but some is turned into heavier long lived transuranics. U-235 is very rare so we can't run just on that: this is what is enriched with centrifuges (no chemical separation possible as it's chemically similar to U-238) and what people mean when they say we will run out of uranium. Most of spent nuclear fuel is still just U-238. Maybe one could simplify and say that the spent fuel is not "used up" : instead it is "poisoned".

2. Thorium reactors have Th-232 and U-233. Simplified, the Th-232 turns into U-233 when it absorbs a neutron. U-233 fissions very well and releases more than two neutrons when it captures a neutron. There's quite many steps up to transuranics from that where fission can still happen, so you get very little transuranics.

3. There is the "breeder reactor" that would use just U-238 by making plutonium out of that. But you need fast spectrum and it's hard to control. It would have plenty of fuel though since there's lots of U-238.

4. What's more significant is that since U-233 is so good, you only need very little. AND you can use thermal spectrum making control easy.

The thorium system is very clever in so many ways but it only works well if you design the whole reactor concept understanding what you have - neutronics and chemistry.

It's not very complex at all, just read up on it, the basics can be understood in a couple of hours.

Then you understand why it produces less waste, consumes less fuel, why putting thorium rods to solid fuel reactors doesn't make sense (protactinium) etc etc...

The answer, when compared to typical light water reactors is... A hell of a lot less. First, since Thorium is a byproduct of Rare Earth Element mining and Uranium is mined specifically, there is all the mining waste that is saved. Second, since Thorium is used up ~completely and Uranium is used only about 0.5%, you need about 200 times more raw Uranium metal than Thorium meaning even MORE mining waste. Third, all the extra metal is RadioActive Waste. Fourth, in making the solid fuel elements, various reactants etc. become even more RAW. Fifth, the pellets are clad, then assembled into bundles using metal that gets irradiated and becomes ever more RAW. Sixth, the vast majority of the fuel pellet is U238 which gets irradiated and some becomes transUranic elements, significantly more than in a LFTR. only then do the two become ALMOST equivalent in the amount of fission products made, though even there the LFTR can be substantially more efficient at turning heat into electricity, so less fuel needs to be converted.

Oh, and most fission products decay to stability in hours, some take years, a few take a few hundred years and the rest are transmutable. It is the TRUs that represent the big storage problem. But guess what, LFTRs can burn them up too.

Not only do LFTRs not generate significant amounts of "wastes" but they can burn the problem waste from PWRs. How cool is that?!!!

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