Hacker News new | past | comments | ask | show | jobs | submit login
Thorium nuclear reactors: a possible solution of the energy crisis? (video) (youtube.com)
227 points by japaget on July 3, 2011 | hide | past | favorite | 102 comments

I've studied this for years and haven't found any credible reason why we couldn't do this today.

But there are a lot of forces allied against Thorium in both the government, energy companies and the current nuclear industry.

Senator Hatch (R) Utah with support from Harry Reid (D) Nevada has introduced a bill annually for five years to fund $200 million to research to commercialize Thorium power. Yet every year the bill never even gets voted on.


What is stopping Google itself from funding this I don't know? Our country should make this a major initiative similar to the race to the moon and get us off coal, oil and gas.

I'm not sure if the following links refer to the same thorium architecture but in Germany there was a test-reactor and several rather hard to solve problems appeared


http://juwel.fz-juelich.de:8080/dspace/bitstream/2128/3136/1... [50+ page PDF outlining the problems]

That was a pebble bed reactor which had issues with high pressure containment vessels and solid fuel. The reactors recommended in the video are molten salt reactors which do not have the same issues.

I think the issues were not only technical, as in P and fuel. The trouble was with those who were responsible for the pebble bed reactor project, and accountancy to the public.

The moment management knowingly blamed accidents on Russians with oversight from the authority, they played away their authority to the right of running such experiments: be it solid fuel or liquid.

People (rightly) assume, that the blatant lies were independent of the phase of the fuel

(AVR and HTR as separate projects make no difference in this respect either). And this is what is biting TEPCO: the series of "white" lies.

We could start scaling up research today, which we should, but it's a bit much to say we could start building Thorium power reactors today. Other reactor designs are far, far more developed and generally have had full-scale pilot reactors built and operated, the same is not true for Thorium reactors.

Another data point:

Even in India (which has 25% of world's Thorium reserves), it is a mystery to many, as to why the Govt. chose not to invest more heavily in Thorium based research, rather than going for traditional ones.

Edit: grammar.

Not sure how you figure that, India's whole research program is geared toward a pure-thorium future.


India seems to only go for technologies that foreign companies have developed. Guess why? Kick backs are a nice way of living the good life. This, even as recent hikes in fuel prices across the country are putting paid to the dreams of a growing economy.

You guys must be kidding: http://www.youtube.com/watch?v=Nl5DiTPw3dk

I would love to see this being scaled up and put into production. I've been hearing about thorium reactors for the last 20 years.


"The country is involved in the development of nuclear fusion reactors through its participation in the ITER project and is a global leader in the development of thorium-based fast breeder reactors."

Because uranium is cheap, so why bother? The price of nuclear energy is dominated by the cost of building the reactor, not the fuel.

Did you watch the video?

The reactors he presented appeared to be much simpler (so... they'd likely be cheaper).

As a nuclear engineer, I doubt it.

Sorry to say this but you have probably been deceived by the nuclear industry. First of all thorium is much cheaper (about 160 times I think), secondly it's far more abundant and third LFTR has a much better design.

The industry dismissed liquid reactors because of the problem extracting weapon grade material. Uranium based reactors where not as safe nor as cheap. During the cold war this made sense but not today.

It has also been about people protection their jobs. The uranium based industry can't say that something else is better because then they might lose their jobs. And who do you think the politicians ask when they want advice?

Sorry to say this but you have probably been deceived by the nuclear industry.

Or perhaps you've been swept up by the breathless prose of popular science articles?

As far from peak uranium as we appear to be, there is simply no need to explore alternative fuel sources. Fuel is not scarce. The capital (political and financial) to build infrastructure - both power plants and reprocessing plants - is.

In that climate, the (never-been-built-or-licensed) LFTR is only a game-changer if its construction (and licensing and R&D) costs are an order of magnitude lower than those of current-gen reactors. This I highly doubt.

Waste disposal/processing isn't cheap and Thorium produces significantly less waste than Uranium.

Thorium waste will be indistinguishable from Uranium waste for the next 100 years, from a public policy perspective, unless we first build a reprocessing plant.

(To be more specific, it's the absence of nuclides with mass number greater than 238 in Thorium waste that makes it less problematic than Uranium waste. These nuclides dominate the long-time, i.e. millenium, radiation profile of the waste. The short-time, i.e. decade/century, radiation profile of the waste is dominated by lower-mass-number fission products, abundant in both types of waste)

Reprocessing plants are extraordinarily expensive to build and operate, more so even than reactors themselves.

And thorium is bound to be even cheaper, as it's readily available in massive quantities.

Like I said, the cost of fuel doesn't matter. Fuel could be free, and a new reactor would still take forever to pay for itself.

But if you look at the design you will see that it's much more simple than a PWR. All calculations I've seen puts the cost of construction well below the cost of modern PWRs.

And the cost of fuel is still important, uranium isn't getting cheaper.

> All calculations I've seen puts the cost of construction well below the cost of modern PWRs.

And what calculations are those?

Google is not in nuclear energy business.

It would be better for all of us if Google stays focused in software development.

Google is in the renewable energy business. They have devoted well over $400Million US to solar, hydro, and wind power startups. They see energy as their biggest cost point in the next decade (powering data centers is not trivial).

Google is in search business.

I think focusing on power is a mistake for Google (unless founders are having fun toying with power).

Google is a pretty large and technically savvy advertising company that does search and a bunch of other things.

If energy costs are eating into their bottom line and they have the cash, why shouldn't they invest into new energy tech. Seems like a good business decision to me

"why shouldn't they invest into new energy tech"

Because amount of attention that top management have is limited.

Google would be better off if they focus on their core products.

For example, Search.

If Google has actually spent that much on renewables, then why didn't they give Bussard the measly $5M (or maybe it was $20M) for which he practically begged them, back on 11/09/06? He needed $200M, over 5 years, to build his fusion reactor, but only a small fraction of that to confirm some important experimental results which he had achieved just before the Navy cut his funding. He believed that he could get that confirmation, and that it would be enough to show that proceeding with the $200M investment would be prudent. I was quite sad to see that he died about 11 months later, having not achieved his dream, and having been reduced to begging at the end of his life. Google not only should have given him the $5M/$20M, but they should have been thrilled and honored to have such an intellect even speaking to them. Fuck Google's shortsightedness.

http://youtube.com/watch?v=FhL5VO2NStU http://en.wikipedia.org/wiki/Robert_W._Bussard http://newmexico.watchdog.org/7104/fusion-energy-promises-yi...


$280Million just in june.

I don't know anything about Bussard, but seems like he unfortunately passed away before completing his research (which admittedly was underfunded). However I wonder if part of the reason for it being underfunded is that it promised power that was TOO cheap. Too cheap to profit at the same scale as coal etc.

The response said what is stopping google from 'funding' this, not 'creating' this. Of course, they would benefit too.

"Funding" requires focus too.

Enough focus to say, "Hey, good idea". I think it would be better for all of us if Google got any of the potential patents as well. Even if it isn't their main business.

This is project pursued by many[1]. The main hurdles are:

1. political [2], which Kirk mentions (it is no coincidence, that the pellets that the rods contain are as standard as the NATO bullet) -- the industry and power has a very different interest

2. technical: Kirk always mentions, that the fuel is not solid. It is liquid. The latter means, that you do have higher concerns about corrosiveness, hence (useful) reactor lifetime...

Also, the issue of scale, which tends to lie between 1. and 2. Uranium "won", because you got the real stuff with it (weapons as in actual projection of power, or the capability of threat to project power) and because you could make it work on a massive scale (current reactors are an order of magnitude larger than any LFTR design, and capitalism is based on the leverage of and concentration of power).

[1] http://energyfromthorium.com/



... besides China, India, France and (even) Czechs.

[2] http://www.bbc.co.uk/blogs/adamcurtis/2011/03/a_is_for_atom.... -> see Seaborg interview part

Corrosion is one of the main objections people bring up, given that the fuel is a liquid salt. Sorenson says there's an alloy that solves the problem.

I do not think that corrosion is the showstopper.

It rather seems to be the lack of irresponsible megalomania, which actually fuelled the GE/Westinghouse frenzy. And I can hardly blame anybody for the lack of it, because for all the better... Our planet has became smaller in the last 50 years, and running (tea)pot operations would be a tough sell, even on Fox. But obviously (offshore) oils rigs and gas are no better either, though people are still happy with oil running their cars and data-centres.

But useful lifetime/economics of scale/TCO does matter, because ROI in the strict and sole monetary sense is the only metric of success. Note, that most reactors have been rubber-stamped to operate beyond their design lifetime.

Watch Seaborg and some engineers from ex-USSR above before downvoting without reasoning.

And imagine the powerlines in a play, where Seaborg himself feels he can only act as a puppet -- randian rationalism doesn't work in society. (I do not agree/disagree with all of the comments above, just note)

Thanks for your argument. Case closed.

you see now too -- the alloy is not the problem.

I hear a lot about the LFTR, and I wonder what the problem is. Is there a major technical hurdle that prevents this from seeing widespread use?

Sometimes there is, sometimes there isn't. Sometimes a really good idea never gets used because... well... because nobody really picks it up and runs with it. It's that simple sometimes.

But sometimes there's some hidden gotcha.

The most common 'gotcha' is that you can't make a thorium reactor critical with just thorium. It needs 'boost' neutrons. The most way that was done in the past was a small bit of uranium or plutonium that was critical to provide the neutrons. A more innovative way is to use a small particle accellerator to provide the thorium with neutrons [1].

[1] http://www.physorg.com/news/2011-06-pint-sized-particle-nucl...

It's actually U233 that fissions. The neutrons convert thorium to U233, and when U233 fissions it produces neutrons that convert more thorium. So once you get the reaction started, you don't need an external neutron source.

LFTR proponents figure the simplest approach is to just go ahead and use U233 to seed the reaction. The U.S. has one ton of U233, which it currently plans to dispose of.

Short answer: yes, you do need to maintain an external neutron source for Thorium reactors.

The advantage of Thorium is that you can maintain the reaction subcritical. That means it is much easier to shut down by simply removing the neutron source. In a critical reactor, you have to physically inject control rods containing a neutron sink (usually Halfnium or Boron). These elements can jam or be ejected under certain unlikely conditions (this is one of the things that happened at Chernobyl, and has happened at a handful of military test reactors in the US that no one has ever heard of).

In practice, however, modern reactors are designed to take this type of jamming into account. There is no known failure mechanism where it would become an issue.

FWIW, I was an engineer on a nuclear submarine.

No no no no.. you don't want to do subcritical particle accelerator reactors. Well, you don't want solid fuel reactors, solid fuel has the same cooling issues as standard uranium, since it's the fission product breakdown that caused the Fukushima accidents (not an initial nuclear excursion, like Chernobyl).

Molten salt can be passively cooled (much better thermal conductivity) and can be moved from core to containment by gravity. Also it expands when its hot, which slows the reaction, and it's chemically stable and doesn't crack like uranium fuel pellets.

There are people who advocate subcritical reactors, but that's not how the LFTR works. Fissioning U-233 produces plenty of neutrons to keep a thorium reactor going. See the last couple paragraphs here: http://energyfromthorium.com/2006/04/28/whats-the-difference...

Mainly it's historical reasons. Light-water reactors were developed first, for nuclear submarines. Once they had those working, everybody went with what they knew, and thorium advocates got fired. Then people forgot about thorium.

At this point, NRC regulations assume solid fuel, and the nuclear industry makes most of its money from selling complex fabricated fuel rods.

However, there was a small liquid-fluoride reactor actually working back in the 60s.

The main technical objection I've seen is corrosion from the liquid-salt fuel. Sorenson claims there's an alloy that makes it a non-issue.

The first reactors were actually heavy water for producing plutonium for nuclear weapons. Light water reactors were developed next because they could still produce plutonium, were cheaper, and could be put on a submarine. But their usefulness on subs was secondary. The USSR built Pb moderated reactors for some Alfa class subs that didn't require anyone working in the engine room. For lots of reasons, this is obviously superior as a submarine reactor tech. (See http://en.wikipedia.org/wiki/Alfa_class_submarine)

The real reason we never went to Thorium is the best reason to go to Thorium. It creates U233, which is not usable for nuclear weapons. (Or at least, no nuclear weapon has ever been built with it.) This would have made it great for exporting to countries without worrying about proliferation. That's the reason we're seeing it become discussed so much more often now.

The first reactors were not heavy-water, but graphite moderated (and light-water cooled). Nazi Germany intended to build heavy-water reactors, but they did not succeed.

Pb (actually Pb-Bi eutectic) isn't a moderator, just a coolant. Alfa-class submarines' reactors were fast reactors (no moderator).

I don't know anything about the German bomb program, except that it was pretty unsuccessful. (To be fair, they had people bombing their scientists the whole war.) The heavy water reactors I referred to were from the Manhattan Project. (They did have graphite moderated too, but they weren't as successful I understand.)

You're right that Pb is only the coolant. I got typing too fast.

I believe you've confused something. Almost all plutonium from the Manhattan project (e.g. 'Fat Man') was from graphite-moderated, light-water cooled reactors at Hanford site in Washington, starting with the 'B reactor'.

Plutonium: The First 50 Years (chapter 9)



The US did not build a heavy-water plutonium production reactor before those at the Savannah River Site (South Carolina), which did not start until 1953. These are all the plutonium production reactors the US has built (ref. DoE): 9 graphite-moderated light-water cooled reactors at Hanford, and 5 heavy-water moderated/heavy-water cooled reactors at Savannah River.

In the Manhattan project, there were also tiny amounts of plutonium sourced from the X-10 reactor at Oak Ridge (also graphite-moderated):


Separately, there was highly-enriched uranium produced at Oak Ridge (Tennessee), which was used in 'Little Boy'.

And, CP-3 was a research heavy-water reactor (Chicago), built in 1944, which was not used for breeding plutonium.


Hope this clears things up...

My understanding is that building the reactors are significantly more expensive. So until the price of Uranium increases enough to justify the total cost of the Thorium reactors, we won't see many of them outside research settings.

The other issue is building a new reactor of any type right now is a giant pain in the ass, which doesn't help either.

Thorium reactors should be quite a bit cheaper. Light-water reactors operate at 160 atmospheres of pressure. They need a very strong reactor vessel, which currently can only be forged by a single facility in Japan. They need a large containment dome because if a pipe breaks, that high-pressure water will flash into steam with a thousand times the volume. They use lots of redundant emergency active cooling mechanisms. Some of them have giant slabs of ice inside the containment dome, which reduce the volume of steam if it's released but have to be constantly refrigerated, to keep them frozen in close proximity to a nuclear reactor core.

LWRs are resupplied every year with expensive fabricated fuel rods, which are non-standard and can only be purchased from the company that sold the reactor. The fuel rods are complicated because they have to withstand a thousand-degree temperature gradient, and the fuel pellets are prone to cracking from the production of xenon gas. Xenon and other reaction products prevent the use of more than one percent or so of the energy potential of the nuclear fuel, another reason the rods are frequently replaced, and the reason we have so much nasty nuclear waste.

The nuclear industry makes most of its revenue from selling those fuel rods.

LFTRs operate at atmospheric pressure. No super-strong steel, no containment dome, no ice. It's a liquid fuel, so no proprietary fuel rods. Xenon just bubbles out of it.

The fuel has a strong "negative coefficient," meaning the reaction slows down as it gets hotter. If it nevertheless gets too hot, a salt plug melts and all the fuel drains into a passive cooling tank. No need for all those active cooling systems.

On top of that, LFTRs operate at higher temperature, so the turbine is more efficient, and the waste heat can be used to desalinate seawater. They don't require water cooling. As a bonus, marketable reaction products can be separated from the liquid fuel (http://flibe-energy.com/products/).

Misguided government regulation is the main problem, but Sorenson's company plans to get around that by selling to the military first.

"Misguided government regulation is the main problem, but Sorenson's company plans to get around that by selling to the military first."

Sorry but is this subtle irony? My apologies if it's not, I don't know anything about this field. It just seems weird that the military wouldn't be subject to the same regulations that the govt. sets? Or in the US are the military able to ignore some of the regulations around this?

The NRC has no authority over nuclear aircraft carriers and submarines. The military's stuff is classified, and it does its own regulation.

The latter, I'm sure. When you are a war economy, the military rules supreme.

In the video he states that the cost would be 30-50% lower because the reactors are very simple. The cost for uranium based fuel is also significantly more expensive (watch the vide). He states that the reason people don't build these is because they don't know about them, or they are stuck in the existing structure of legacy reactor thinking.

The reason that anything new is a pain in the ass is simply because of bureaucracy.

It might be that you could make a thorium reactor much safer than current light-water reactors for cheaper, but the laws regulating our nuclear power were written under the assumption that all reactors were light-water reactors - so in practice you would end up with all the fancy 100% reliable control systems needed to keep the positive feedback loops in a traditional reactor from blowing themselves up as well as the special metallurgy needed by Thorium reactors.

That is the case, and it's a big problem. NRC regulations for example require "fuel integrity," which doesn't exist with liquid fuel.

Sorenson's company plans to market initially to the military, which has need of compact energy sources for remote bases and isn't constrained by the NRC.

CANDU, one of the best uranium designs, has the same problem.

It's sort of like inkjet printers. Either it's cheaper up front and more expensive in the long run, or it costs a fortune up front but the ink is cheap.

To be completely honest, though, one of the biggest obstacles to widespread CANDU implementation in the past was that it isn't a breeder.

> Is there a major technical hurdle ... ?

That's exactly my question, too. So I tried to find some alternative view on that topic. Unfortunately, I only found some criticism of questionable quality ...


... as well as a rebuttal of questionable quality:


The ratio of plutonium needed to seed and convert thorium into fissionable uranium-233 is very high (0.8:1)

Except for that fact that we already have plenty of U233 sitting around being useless at Oak Ridge. Certainly plenty to do all the research and prototyping needed to get a design certification for a LFTR.

Clearly, the problem is the political will to do something different. If the nuclear lobby and the anti-nuclear lobby are both against it, it's hard to get traction. Kirk is likely correct. The only way to get this through is via the DoD. I wish FLIBE Energy the best.

Uranium reactors are children of war, much like hydrogen-bomb-shaped communications satellites. They are a byproduct of A-bomb research. From wikipedia:

1) Weapons-grade fissionable material (233U) is harder to retrieve safely and clandestinely from a thorium reactor

2)Thorium cannot sustain a nuclear chain reaction without priming, so fission stops by default.

The focus with Uranium reactors wasn't to make reaction efficient over time, just violent. What I'm trying to say is the current atomic energy industry is heavily invested in Uranium. No wonder they're resistant to change.

Just like (almost) every spaceship designed is a descendant of the V2 rocket.

War is an incredible catalyst of the discovery process, but it unearths such discoveries just to throw them into a local optimum.

I just wrote a bunch of comments arguing in its favor but here's an article I just found with various criticisms I hadn't seen before: http://daryanenergyblog.wordpress.com/ca/part-8-msr-lftr/

I'm not sure how credible this guy is, because he talks about thorium-232 as a dangerous nuclear waste, with a terrible 14 billion year half-life. The problems with this are (1) such a long half-life means its hardly radioactive at all, and (2) that's the only isotope of thorium, which means it's the same stuff that exists in large quantities already in natural ore.

Also I'm not sure why he thinks U-232 has to be separated from the U-233.

Aside from that, he raises some interesting objections.

He may be exaggerating the complexity of the reprocessing system. Wikipedia describes it in detail: http://en.wikipedia.org/wiki/Molten_salt_reactor#On-line_rep...

Kinda wish I could delete that comment. Here's a bunch of people on reddit ripping that article apart: http://www.reddit.com/r/energy/comments/ifx40/molten_salt_lf...

The "advantage" that the LFTR doesn't produce fissile material was probably considered a disadvantage by most governments, at least until about a decade ago.

Now that we have decades of experience with light water reactors it simply is a challenge to propose a solution that unproven on a commercial scale. It may look good on paper but it would be a multi-billion dollar project with multi-billion dollar risks. Visionary politicians who would want to take such risks are in short supply.

I go to school at Boston University and took an Energy class with a Nobel Laureate in physics, Sheldon Glashow, last semester. He spoke in great depth about Thorium reactors, and is very supportive of the technology.

One of the main hurdles is that we have poured money into our modern-day reactors, and have constructed hundreds of plants. If we were to switch to thorium, we would have to essentially start from scratch - new research, new plant designs, new training, etc. It is very difficult to justify a complete switch from uranium, as it would be incredibly costly.

In other countries, however, thorium reactors could be very beneficial. Countries using thorium would not be able to produce nuclear weapons, which would give the world great peace of mind. This could minimize risks in unstable countries - we wouldn't worry if Iran was building a thorium reactor, for example.

There are also other types of reactor designs that use nuclear waste to create power. I believe our nuclear future lies with these types of reactors, rather than with uranium or thorium.

Don't switch from uranium. Switch from coal.

Since India has a lot of Thorium, they are actively pursuing it. http://www.youtube.com/watch?v=Nl5DiTPw3dk&feature=relat...

Just use CANDU reactors, it will burn raw uranium, and can use the waste product from PWR reactors, just leave the thorium in the raw uranium. It's been working for years, no Yucca mountain, Yucca mountain is a purely US phenomena, it doesn't exist in Canada or France. It's not a new technology, it's 60 years old. All you need is a little heavy water, and in event of a meltdown you just flood the tank with regular water and voila no reactions.


Here's the fuel cycle for a CANDU reactor which will support the thorium cycle as well. http://en.wikipedia.org/wiki/File:CANDU_fuel_cycles.jpg

For anyone who wants to delve into this more deeply, Sorenson's videos (http://energyfromthorium.com/2011/06/04/adventures-with-gord...) are really great. I recently watched the two-hour one, which was edited from a longer talk to cut out the pauses. It's a rapid-fire, passionate technical introduction that I found very compelling.

Any plans to build a reactor somewhere?

I fear that mere engineering heavy talking has no chance solving nuclear’s PR problem.

Actually building a reactor might help. Maybe. Maybe not.

Maybie with the generational shift things will change. For USA's sakes, let's hope it won't be too late.

If the world was serious about nuclear non-proliferation, we would have thorium reactors everywhere already. They said a few times in the video that thorium reactors can't be used for weapons, and so they are not built. Governments have decided that we need nukes, so thorium reactors do not get funding.

But if we are serious about non-proliferation, then switching to thorium reactors and controlling which new reactors get built is a much more effective strategy then the current weapon-counting efforts. Once a reactor is built and starts creating fissile material, then it is difficult to keep track of and control. But it is much harder to hide a reactor while you are building it - Iran tried and failed.

So it seems to me that thorium reactors, in addition to their efficiency, low cost and low amount of radioactive waste, could also be a useful tool in enforcing nuclear non-proliferation. We've got these reactors that cannot be used to make bombs - why don't we sign treaties saying that they are the only reactors that can be built?

I read an American company is trying to make one in the north of Chile. It's because they really need energy (they're currently using coal and diesel to keep the lights on in the north) and there's not a whole lot of bio-anything to protect there. I think it's a great idea, but a lot of people don't.

This cutted version feels like none of these persons said anything that is in the video, because the statements (or even words) are "out of context". I just can assume the author of the video has good intentions and did not change the context.

Here are the original videos:

The Liquid Fluoride Thorium Reactor: What Fusion Wanted To Be http://www.youtube.com/watch?v=AHs2Ugxo7-8

Aim High: Using Thorium Energy to Address Environmental Problems http://www.youtube.com/watch?v=VgKfS74hVvQ

Lessons for the Liquid-Fluoride Thorium Reactor (from history) http://www.youtube.com/watch?v=AZR0UKxNPh8

I watched one of the videos and seems accurate enough. The cut left out an important bit from the end of that video. Developing those kinds of thorium reactors would take the US five years with a Manhattan Project style investment. Ten or more years at a slower pace and lower price.

This is by no means cheap and easy, "it's not THAT hard" is a quote that made the cut. I imagine the effort would be comparable to making uranium reactors for power stations which took around thirty years.

I've watched all of the videos-- this is a very good summary of them. Plus, it isn't like the editor/uploader doesn't make it easy to find the original videos anyway.

I really liked this. I doubt I would have had tie to watch the original, but yeah... it does rely heavily on the integrity of the editor.

FWIW, I recently watched one of the talks this is spliced from, and it seemed fairly accurate.

Thus video just gave me something to research for the next few days.

You can still make bombs from the thorium cycle, with U233.

Many people claim you can't, due to fact it's generally a mixture of U232 as well, which will decay rapidly and cook your detonator/firing mechanism, but a couple of interesting comments I found suggest a liquid fuel would be amenable to continuous separation:



The MET test of Operation Teapot being the first example of a successful U233 firing: http://nuclearweaponarchive.org/Usa/Tests/Teapot.html

The MET test was not a pure U-233 design, it was a mixture of Pu-239 and U-233, it also had 1/3 lower yield than the equivalent design using U-235.

Ah, thanks, I didn't notice the 'mixed U/Pu' bit originally.

On the second point, not only was it 1/3 of the equivalent (and specified) 235 design, it was also 1/3 less than predicted for itself, if I'm reading it correctly. I wonder if that was an error in the prediction, or a fault of the weapon/design.

I've forgotten most of the nuclear chemistry involved in producing Pu, but iirc it can be done with natural uranium and a neutron source. But then again, if you have those, and can produce plutonium, why not just use that? Maybe it'd be helpful as a filler if you've got some, and only limited Pu resources, or to simplify weapon design (Any idea if the MET was gun-type or implosion-type, sources being unsurprisingly hard to find)?

The MET test was odd, the military wanted a highly dialed in yield to test effects of nuclear weapons but somehow there was a miscommunication and they ended up using U-233 as a replacement for U-235 as an experiment. We really don't have enough information about how well U-233 might work in a nuclear weapon to make a judgment on the subject.

Anywho, in regards to the larger point, I discussed the issue in another comment, here: http://news.ycombinator.com/item?id=2723675

Basically, proliferation concerns transition entirely to the honor system once someone is operating any sort of fission based reactor, even one powered by Thorium. Since it is quite easy to breed Plutonium merely by placing natural (and readily available) U-238 in a high neutron flux environment. Simply remove your Uranium samples every 90 days or so and chemically separate out the Plutonium.

The non-proliferation aspects of Thorium reactors are a bit overstated. Consider that the easiest way to create fissile fuel for nuclear weapons is to merely have access to an abundant neutron source, such as any fission reactor (Thorium or not). If you have an LFTR you can just place natural Uranium-238 near the reactor core and use the neutron flux to breed Pu-239, easy peasy.

As far as producing materials that could be stolen and used for nuclear weapons manufacture, that at least is a little bit better with a Thorium fuel cycle. Presumably the U-233 would simply be left to burn up in the reactor, rather than being separated out and kept in storage. If someone happened to obtain some used fuel they could potentially separate out the U-233 and use it to make weapons, although it would require substantial engineering. Also, since U-233 is very much more radioactive than U-235 or Pu-239 it requires handling with remote manipulators. Any organization that had the ability to separate U-233, engineer the appropriate modified bomb design, then process and machine the U-233 using only remote manipulation is extremely likely to have a sufficient level of technology and industry to build reactors or separators on their own (meaning, able to build nuclear weapons independent of having access to used Thorium fuel).

In theory you can, but nobody makes bombs with U233 because it's easier to make bombs in other ways.

It seems to me that the real question for proliferation is not "is it theoretically possible to make bombs with this," but rather "if you wanted to make bombs and you had this technology, would you use it to make your bombs, or would you still prefer other methods?"

It's easier to make them other ways at the moment, because U233 isn't common. But popularize and reduce the cost of this cycle, as well as claiming it's "proliferation resistant" and hence suitable for export to non-members of the we-got-nukes club, may well lead to weapons being made out of it.

Still, if you made a u233 device (and I'm thinking it would have to be a dirty bomb, an explosive seems unfeasible), it would difficult to get it to a target since it's so easy to spot the gamma rays.

u235 is still the way to go, since you can just hide it in a lead pipe in a crate of bananas.

Kirk Sorenson on Dr kiki’s Science Hour: http://www.youtube.com/watch?v=vEpnpyd-jbw

the UK National Nuclear Laboratory (NNL) undertook a recent independent assessment, in which it assessed a number of claims made by proponents of thorium fuel. The report can be found at: http://www.nnl.co.uk/positionpapers

I would be deeply skeptical about position papers from the UK, British Nuclear Fuel are a massive, partly government owned company that makes a lot of money from reprocessing. The government started dismantling BFNL into private companies one of which is is the NNL.

Slightly off topic, but could thorium be used for vehicle propulsion? as in nuclear submarines or even better: space craft? if the payload is efficient enough, it could solve the issues we have with getting rockets into space (fuel is heavy, and costly to transport).

Tailor made idea for the "reverse VC pitch"

VC >> find engineers >> provide $$ >> GO.

Can I look forward to a Google thorium salt reactor in the near future?

text > video

I think the video is really interesting but it seems strange that it is highly edited and sliced together? Whenever I see something so hacked together I question the context that some of the message was cut out to benefit someones agenda

A beautiful thing, opinions. Everyone can have one of their own.

I have a whole lot of related links here making the case for thorium: http://webwanderings.wordpress.com/2011/04/07/thorium-based-...

Guidelines | FAQ | Support | API | Security | Lists | Bookmarklet | Legal | Apply to YC | Contact