Thorium | Hacker News Reader

Thorium

austinmeyer.com

204 pointsjasim72 comments

This article perpetuates a common misunderstanding about radioactive half-lives, which is that shorter ones are better because the waste isn't dangerous as long. Actually, isotopes with short half-lives are undergoing radioactive decay very quickly, and are thus much more highly radioactive than substances with longer half-lives. There are radioactive isotopes in dirt, vegetables, etc., but they pose us no risk because their half-lives are so long as to not radiate significantly enough for it to matter. Fission byproducts with 300-year half-lives are actually super dangerous.

Interestingly, most thorium proponents point to this danger inherent in the thorium fuel cycle as a selling point, because it makes thorium waste so difficult to handle as to be a hindrance to proliferation.

In general, even speaking as someone who's generally pretty excited about thorium power, I'm not a huge fan of this article because I don't get the sense that this author has a super-solid handle on the science.

Good point.

I work a bit with PET-related isotopes, mostly fluor-18 and carbon-11, which has half-lives of 110 and 20 minutes, respectively. You gotta be careful with that stuff, the radiation (β-minus) is pretty dangerous if you're exposed for long (usually there's 5-30 GBq per vial), but again, it's pretty neat that if something happens (you spill something for example), you can just leave the room and clean it the next day without any problems. Overall, there's really no radioactive waste, since after 24 hours it's darn safe (and the FDG turned to sugarwater, literally).

> you can just leave the room and clean it the next day without any problems

Wouldn't it radiate into the room and make the room... bad? (Sorry, I'm clueless about this subject)

Usually it's neutron radiation that makes things radioactive[1]. Really energetic particles can do the same[2]. But the positron emission from Flourine-18 I don't think has enough energy to do that.

[1] Being neutral particles they can easily be absorbed by the nucleus of whatever. Adding an extra neutron may result in an unstable nucleolus.

[2] Friend that worked at SLAC (big linear accelerator) gave us a tour and mentioned the block of aluminum they use to backstop the beam. He said it gets slightly radioactive.

http://www.slac.stanford.edu/pubs/slacpubs/1250/slac-pub-140...

Radiation is very different from radioactivity.

It's sort of like the idea that a microwave can be dangerous running exposed, but it's fine the moment the magnetron stops.

If you have a rapidly decaying isotope, it will produce lots of radiation. However, most of that radiation will be harmless.

Some ionizing radiation will be able to change the atoms that make up surrounding materials, but most of that will remain harmless, and very little will become radioactive.

Not the best direct source, but this is asserted to be from Nuclear Engineering International magazine in November 2009

http://www.greenpeace.org/international/community_images/88/...

via

http://www.greenpeace.org/international/en/news/Blogs/nuclea...

Thorium waste appears substantially less radioactive at shorter timescales we care about. On really long (10^4 - 10^6 years) timescales the proactinium-231 becomes an issue and uranium waste pulls ahead of thorium waste slightly. As we don't really have any idea how to plan on those timescales anyway (it's not like they're still going to be sitting in casks in a pool of water in New Jersey in 10^4 years), I think thorium is a lot better candidate from this perspective.

I'm not sure exactly why a non-fissile material with a half life this long is a "problem". By definition it's not.

Beside these are the burnup rates for Once-Through solid fuel cycles. In Uranium reactors this is only recommended if you are actively trying to create weapons material, and in Throium it simply doesn't work. Not sure what the relevance of these articles is.

That writing was even worse than the OP!

Very short half-life-times in the minute regime and below are actually pretty great because you can just keep that stuff in a container for some time and it decays away exponentially.

If a "waste product" is still that energetic, then is it waste after all?

As I understand it, the main waste product of concern is Uranium-232, which is highly radioactive (half-life of ~70 years) but not fissile. Conceivably you could maybe use it for power generation in some other way, though, like with a radioisotype thermoelectric generator? I'm not sure it would be worth the effort, though.

U232 is not fun to work with, well into the "robot arms" level of gamma radiation output.

U235 and P239 are like "wear gloves, glovebox"

In a lab, or WRT inevitable accidents and contamination, its like the difference between working with strong industrial acids vs nerve gases.

Its really a huge pain. The article author seems to have hand waved away several practical engineering problems like this. Also see his interesting hand waving away of the steam cycle as we know it, hand wave away molten salt moderator issues, etc.

Some things are a practical pain because nobody's given the engineers enough $$$ yet, some things are a pain because of basic physics and chemistry reasons. I think the article author is confusing those two. Certainly, the nuclear industry over the last 70 years has not lacked for money or brainpower.

I do find it sad that we don't yet have a more efficient means of capturing the output of a nuclear reactor than heating liquid to power a turbine. Seems like there should be a more direct (and more efficient) path from fission or fusion to electricity.

So much of the nuclear reaction ends up just wiggling the atoms around, so it's tough to do anything smarter than a heat engine.

It is possible to generate power by other means. For example, you can use radioactive isotopes which emit beta radiation to generate electricity directly, since beta radiation is just free electrons.

With fusion (ignoring the important problem of breakeven) you have an energetic plasma, and you can extract energy using magnetic fields rather than with turbines.

For fission, the energy produced goes into moving neutrons and the fragments of the nuclei, which I don't think can really be captured other than as heat.

MHD generators powered by decelerating nuclei fragments are possible and aren't subject to the limits of the Carnot Cycle, but they're still uneconomic at this point.

>> "ignoring the important problem of breakeven"

I am so happy you included that line. From when I was studying fusion the actual conversion into usable energy was a complete after thought because breakeven is such a larger challenge.

Indeed. It's an interesting question to figure out how to turn a sustainable fusion reaction into electricity, but it's totally pointless until the main problem is solved. In context I thought it was worth mentioning, since fusion does allow some interesting possibilities in this area, but there's no practical use for it at the moment.

Using the difference between a hot and cold reservoir to do work is a very fundamental, pure way to look at energy. It seems very natural to me.

I don't think the GP is bemoaning how "natural" the process seems, but how inefficient it is. It's pretty much the best we've got currently, given the choices we've made (including those broadly detailed in The Fine Article). That said, there's an aesthetic level at which you kinda have to look at the thermal efficiency of a nuclear power plant — which is, AFAIK, like 30-some percent — and wish we could somehow do better, given all the infrastructure and risk involved.

So has anyone ever calculated the effect of the heat output if all of our power consumption were supplied by nuclear power? (at 30% conversion efficiency). Would the earth just radiate that extra heat off, is it negligible for all practical purposes?

Probably not much different. I'm pretty sure most fossil fuel power plants have comparable efficiencies. It's not like the steam produced by burning dinosaurs is somehow less capable of driving a turbine than what comes from splitting atoms.

Electricity moves energy by driving quasi-static fields with non-zero Poynting vector in a neighborhood of the wire.

Heavy 2-MeV charged particles don't want to couple to that kind of mode at all; they're going to deposit their energy into MeV-ish radiation modes (e.g. Bremmstralung).

Most people underestimate just how insanely efficient steam really is. There aren't (m)any better ways of moving heat around and converting it into electricity, even after 2000 years.

I think he understood the efficiency limits, or in other words, the theory of the Carnot Cycle.

Other than the minimal amount of global heating -- which should be thought about, but it's a lot better than CO2! -- why not just produce more reactors? We're not running out of Thorium, and maybe it can get us off coal. !!!

A nuclear engineer once told me that you could eat more plutonium than you could caffeine, because the caffeine would instantly kill you, but the half life of plutonium was much longer and it would pass in and out of you before anything actually happened.

That claim is usually sourced to a guy named Bernard Cohen, who once volunteered to eat as much pure plutonium as Ralph Nader did caffeine. Nader demurred, and most people disavow Cohen, because who'd actually do that?

That said, consider Albert Stevens. He was (unknowingly) injected with 131 kBq of Pu, accumulating a lifetime dose of ~64 Sv, and died of heart disease some 20 years later.

Agreed. There's also a lack of understanding of the economics behind the construction of industrial power generation facilities. In short: there is virtually no environment in the US where it's a financially sound decision to build any new nuclear power facilities.

Thorium and Uranium waste profiles are pretty similar with respect to the shorter-half-life stuff (fission fragments unstable against beta-minus decay because they've got too many neutrons for their own good).

The government didn't say "give us the one we can make bombs with" or anything like that. In a review [1] they discuss groups working on thorium reactors who find that these reactors are potentially cheaper than water cooled reactors, but there are uncertainties and a demonstration plant is needed. They basically state that thorium reactors might work well, but their potential benefits don't outweigh the existing industrial commitments. Sure, the reason for the existing infrastructure was for the ability to more easily make bombs. But when this was reviewed, it was possible to make bombs with Thorium, too. [2]

There are advantages and disadvantages to thorium over common reactors, but it's definitely not a magic bullet.

[1]: WASH-1222 (p. 49) http://www.energyfromthorium.com/pdf/WASH-1222.pdf

[2]: https://whatisnuclear.com/articles/thorium_myths.html

This writing style makes me actively distrust anything written in it. It's the opposite of convincing.

I agree, and I've been thinking about why that is. It starts with Szilard's understanding, and then misstates that it "was realized in 1945" (the year the bomb dropped on Hiroshima), but anyone who has read about atomic energy knows that the Szilard tested his theory with Fermi in Chicago as Chicago Pile 1 [1] in 1942.

Secondly, it presents the choice of molten salt versus pressurized water reactors (PWR) as a binary choice when it clearly isn't. Running a reactor is a process not a simple act. Fueling and "cleaning" molten salt reactors is an additional burden on the reactor's operation. If you put the number of processes you have to develop to run a molten salt reactor to the number you have to develop to run a PWR, there are fewer processes for a PWR. So from a development stand point the PWR is the MVP of reactors. By the time the research was available on the needed processes for Thorium[2] nuclear power was already under siege [3].

[1] https://en.wikipedia.org/wiki/Chicago_Pile-1

[2] https://en.wikipedia.org/wiki/Molten-Salt_Reactor_Experiment

[3] https://en.wikipedia.org/wiki/Anti-nuclear_protests

You need a lot more fuel fabrication and waste processing facilities for a conventional light water uranium reactor.

This is because uranium fuel must be enriched, and there also is orders of magnitude more waste, because only a small portion of the fuel in the solid can be used.

One could say that in a liquid fluoride thorium reactor (LFTR) those separate plants are integrated in the same building, but they can be much simpler because of the very different nuclear physics and chemistry.

Here's a simplistic diagram http://imgur.com/aKK7JaO

But in terms of processes, this diagram is too simplistic. What about all the attached chemical plant required for semi-continuous on-line fuel reprocessing? Keeping that safe, leak-free and coping with the activation of all the pipework and processing equipment is a huge engineering challenge.

Don't get me wrong, I love the simplicity of the LFTR reactor, but keeping the reactor running at scale requires a lot of additional infrastructure around it, and that's the hard part.

Same, author glosses over important details and is clearly biased. I agree with the spirit of the article but the execution is flawed.

At least the author should have someone proofread it. There are grammar and spelling problems throughout.

Could use a fact check too. Atom was first split by humans in 1938, not 1945.

I thought the article made some interesting points, but the plentiful spelling errors were a red flag. They detracted from my reading experience and casted a doubt on the credibility of the author's writing.

Examples: won;t, he(the) waste, yesterdays, todays, it's power source, flouride, bug(big), radio-active vs. radioactive, lots of unnecessarily Capitalized Words.

Let's not forget that the technology is relatively unexplored. No matter how clean; nobody is going to use something that simply doesn't work. Funding is the only way to improve that, but it's definitely not as peachy as the article tries to make it look. The technology is not mature enough to take to your local congressman (unless you're after funding for research).

Also, generation IV uranium reactors (e.g. PBR) are designed to be passively safe, although expensive. Thorium reactors will need to be safe and most of all cheap - we've become quite efficient at splitting uranium during all the years that thorium has been ignored.

A reactor needs to be economically viable before it is built.

Don't know what you lot are talking about.

It's very easy to read the article, get the basic argument down, and search for more information for everything that didn't sound convincing to you.

It's an article that has a point -- right or wrong. Not everything has to be written as some journal submission.

> It's very easy to read the article

Not for me, at least. My eyes jump to the all-caps words, they jump to the repeated letters in "weeeeelllll....", and I find the unqualified binary assertions and fake dialogue utterly unconvincing.

All these writing techniques combine to set off my crackpot and scam detectors.

I agree with the article's premise, but it takes conscious effort to not dismiss it based on style issues.

I'd agree with you, yet the article leaves me with the same type of response.

I don't know if it's true, but the writing style for me too invokes a feeling that I'm not getting the complete story. Similar to articles from conspiracy theorist or advertising for local unions (I live in Toronto, I have nothing against unions, but their ads just feel like I'm being lied to).

I found it very easy to read too, and when halfway through I remember thinking it's a great example of why I prefer blog posts so much over scientific papers.

However I have to agree with the person you're replying to: the typos and general writing style were making me unsure of the trustworthiness. It's too black and white, not a nuanced list of pros and cons. It seems written to convince people who don't want to know the details, rather than the uninitiated.

I also thought it was easy to read and had no strong qualms with the style.

I'd like to sell you some BEAUTIFUL, SCENIC land in Florida, perfect for raising you're children in a CLEAN, WHOLESOME environment free from the HECTIC, DANGEROUS modern world.

Agreed, I didn't finish reading the post due to the writing style.

It seems to be written in a tone typically used for narrative fiction.

He at the very least stole the setting, theme and the beginning from "The Making of the Atomic Bomb" by Richard Rhodes, mutilated it too.

I agree. It just came off to me as made-up and non-authoritative.

So terrible that I've stopped reading and came back to HN to read the comments to see if it was serious. Now I don't need to finish it.

It's a writing style that is very familiar to anyone who has read X-Plane press releases. Austin Meyer is very fond of all-caps for emphasis.

This is written very similarly to the anti-vaccination articles. Just sets off all kinds of red flags.

It really does, even though I generally tend to favor thorium-cycle power generation.

Also, why is "fluoride" such a hard word to spell?

the "uo" letter sequence is pretty rare. from the latest collins wordlist:

$ grep UO ~/CSW15.txt | wc -l 603

$ grep OU ~/CSW15.txt | wc -l 12564

the most common are QUO- and -UOUS words, plus a handful of _UOS words like "virtuoso"; removing those we are left with a handful of root words:

FLUOR [as noted], BUOY [which americans pronounce "booee" and everyone else "boy", so the letter sequence even leads to dialect pronunciation differences!], DUO, LANGUOR [i've seen this misspelt a lot too], PLUOT, SKEUOMORPH, and a handful of scientific words like GLUON and VACUO-, and words borrowed from other languages like EUONYM and OCTUOR.

It's those "chemtrails" messing with your mind

Previous discussions on HN:

https://news.ycombinator.com/item?id=4912187

https://news.ycombinator.com/item?id=2723675

https://news.ycombinator.com/item?id=7734867

https://news.ycombinator.com/item?id=2401498

https://news.ycombinator.com/item?id=4857053

In particular this thread:

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

The litany of contradictory or bad information on thorium reactors (and nuclear in general) is astounding. That's probably a function of both how polarizing nuclear energy is as a topic, and how nuanced the science actually is.

First off, note that thorium is not the fissile material - it's the fertile material. Thorium 232 is transmuted into something else like Uranium 233 via a breeder reactor, so saying that these reactors use thorium "instead" of uranium is about like saying your gas powered automobile burns crude oil.

As others have pointed out there's also a ton of bad information in this about fuel cycles and half life being the biggest driver of clean vs dirty nuclear, but lest I perpetuate more bad information...

Here's a detailed look at the science: http://www.world-nuclear.org/information-library/current-and...

Thorium or otherwise, it's tilting that the public perception of nuclear energy is based on dated technology. Almost as tilting as electric cars being marketed as zero emission. We as a society have to figure out better answers to power production. When you sell bad science or buzz words to people who really take them as such without realizing that the power still has to come from somewhere, there's less support for funding the research that gets us end-to-end clean power.

Also, FWIW, the only reference I found to "war time politics" being the main driver was http://discovermagazine.com/2014/june/3-ask-discover. I'm guessing the full history was far more complex and nuanced than that.

The timeline is all wrong:

> In 1945, theory was turned into practice. (I can’t even WRITE that without my skin crawling, but nevertheless, it can’t be un-done now). Immediately, the scientists saw that if they just slowed down the reaction a bit, they could get controlled power. Power almost without limit. Power without pollution.

The first controlled chain reaction was achieved by Fermi in 1942, 3 years before Hiroshima.

Yeah this article is garbage and has a middle-school understanding of the history of things at best.

And what the author handily omits: Since the Thorium fuel cycle is based around transmuting Thorium into U-233, which is fissionable, Thorium reactors can be a less complicated that Uranium enrichment pathway to the bomb.

True, not the one the military likes because of U-232 impurities, but good enough for rogue states and other malicious actors to blow up a couple of blocks of a city.

And that is why Thorium is actually tightly controlled. And why there won't be a Thorium revival.

Searched for THTR-300 [1] in the article and nope doesn't come up. It was a commercial size thorium reactor and showed that with a different reactor design you simply have to fight with other problems which the German wikipedia article lists [2]. In the end it didn't offer any of the magical advantages often claimed for thorium reactors and the project ran out of money. Now the government has to pay to clean up.

[1] https://en.wikipedia.org/wiki/THTR-300 [2] https://de.wikipedia.org/wiki/Kernkraftwerk_THTR-300#Problem...

Interesting note, this is the same person as the recently popular "I am being sued, in East Texas, for using Google" video.

Has a similar tone. I find the tone to work better with video than text.

Oh man, it's time for the annual thorium post.

It doesn't need to be evangelized. Don't worry, the scientists and the energy companies are already aware of thorium.

Reads like a typical Thorium article.

They always seem to imply that there is some worldwide government conspiracy against Thorium based energy.

And they always gloss over the fact that this is an old idea that to this day still hasn't managed to prove any of its claims even as a proof of concept.

Throw in the fact that renewable energy is picking up steam and you have a recipe for some very unhappy Thorium proponents indeed.

> And they always gloss over the fact that this is an old idea that to this day still hasn't managed to prove any of its claims even as a proof of concept.

This isn't true. There's been proof of concept.

It's just that people who actually develop Thorium power make more reasonable claims, and its actual advantages aren't that compelling.

Waste storage is next millenium's problem, and the cost of nuclear power is dominated by amortized infrastructure, so the economic advantage of thorium (fuel is more abundant, hence cheaper) just isn't very exciting.

There's quite a good article debunking Thorium misconceptions here: https://whatisnuclear.com/articles/thorium_myths.html

I found it interesting that the reactors can actually be quite good for making bombs.

>In the case of the molten-salt U-233 breeder reactor, it was proposed to have continual chemical processing of a stream of liquid fuel. Such an arrangement also offers a way to completely bypass the U-232 contamination problem because 27-day half-life Pa- 233 could be separated out before it decays into U-233.

And apparently U-233 works fine in bombs:

>because of its low rate of spontaneous-neutron emission, U-233 can, unlike plutonium, be used in simple gun-type fission-weapon designs without significant danger of the yield being reduced by premature initiation of the fission chain reaction

Newport Tower was built in America in the year 1670. Now read this quote about how long Thorium will remain dangerous.

"... And now, finally, the really big one: A Thorium Nuclear reactor would make much less radioactive waste than a convention Nuclear Power Plant, and most of the waste that it DOES make would only be dangerous for…. 300 years. ..."

We could totally manage a Thorium nuclear waste site in a 300-year time frame!

*Newport Tower: https://en.wikipedia.org/wiki/List_of_the_oldest_buildings_i...

The post minimizes the utility of a thorium reactor for making fission weapons.

Neutron irradiation of the most abundant isotope of thorium (Th232) produces U233. The US, the USSR and India have successfully tested U233 in fission weapons. [1] BTW, India has ~ the world's second largest known thorium reserves. [2]

Also, I'd be concerned about the long-term corrosion effects of molten fluorides on pipes, pumps, etc., especially those parts that are in a high neutron flux environment.

Not saying that Th reactors wouldn't be a better choice than what we've fielded to date, but the posted article doesn't lead me to that conclusion.

[1] https://en.wikipedia.org/wiki/Uranium-233 [2] https://en.wikipedia.org/wiki/Occurrence_of_thorium

The ratio of plutonium needed to seed and convert thorium into fissionable uranium-233 is very high (4:5)

https://en.m.wikipedia.org/wiki/Thorium-based_nuclear_power

iirc Flibe Energy is working on a LIFTR reactor http://flibe-energy.com/

"We can give you TWO kinds of reactors: URANIUM-based, where the by-product will be PLUTONIUM, which you can use to make bombs..."

Countries aren't like "Oops I guess we have to make a bomb now," with the plutonium. They are very much happy with that possibility.

Reply on news.ycombinator.com