
Thorium reactors: Asgard’s fire (economist.com)
176 points by mblakele on Apr 11, 2014 | hide | past | web | favorite | 46 comments

This article deserves a bunch of credit for reasonably clearly articulating the distinction between thorium-powered molten salt reactors (the kind the Chinese program eventually aims for, and that groups like Flibe in the states want to build) and thorium-powered pressurized water reactors (like what India is going for). Lots of the amateur enthusiasm for thorium power glosses over the distinction, and while some of the benefits of thorium apply equally to both (like proliferation resistance), others (like many of the purported safety benefits) apply only to the MSR configuration, largely because it runs at atmospheric pressure.

The downside of the MSR configuration is that it's way harder to build, and involves some maybe-not-entirely-solved problems around corrosion resistance, since the salts in question tend to be pretty reactive.

Coincidentally, ASGARD is also a horrible backronym for another nuclear related project.

Advanced fuelS for Generation IV reActors: Reprocessing and Dissolution


The new thorium design should be the Mega-Joule Operationally Limited Nuclear Incident Reactor.


lol, nice.

You, my friend, have not had a proper nethack addiction if you don't have the desire to wish for a blessed +3 warhammer named Mjollnir.


There's a really interesting Ted Talk by Taylor Wilson (perhaps the world's youngest nuclear scientist, and definitely a child prodigy) on thorium reactors as a safer alternative to uranium and plutonium reactors[1].

Apparently there's also this talk[2] by Kirk Sorensen, but I haven't seen that one yet.

[1]: http://www.ted.com/talks/taylor_wilson_my_radical_plan_for_s...

[2]: http://www.ted.com/talks/kirk_sorensen_thorium_an_alternativ...

Two articles on why nuclear will never* scale up:



* (again. It did reach real scale in post-WWII France among other places)

Komanoff doesn't know it but he is helping make the Thorium MSR case. Proponents of the MSR are also critical of LWR economics.

In the USA

I see this as the main takeaway from the article instead:

> One or two 233U bombs were tested in the Nevada desert during the 1950s and, perhaps ominously, another was detonated by India in the late 1990s. [...] intense gamma radiation 233U produces fries the triggering circuitry

...this only shows that military use is possible! For someone less concerned about safety and more concerned about having a nuclear weapon at all costs, it might be even easier. That triggering circuitry is definitely a solvable problem... brrrrrr

Not just the proliferation resistance is a myth, but there are several others making the round: http://www.whatisnuclear.com/articles/thorium_myths.html

Yeah, chemical separation + gun assembly warheads is a particularly bad path to allow, side steps the two hardest current things required (non-chemical uranium enrichment and implosion based warheads).

Certainly it's possible, but it's much harder to do without frying either the triggers or the engineers (gamma rays and people don't play well together), so the conventional wisdom is that non-thorium fuel sources would be lower-hanging fruit, and the pool of actors who could potentially make a bomb with it (or the U233 from further down the fuel cycle) is smaller than with plutonium or enriched uranium. "Proliferation-resistant" is the claim, not "proliferation-proof."

I think thorium MSRs are the most promising of the GenIV designs. However, the biggest engineering challenge with them is with the U-232 being produced. U-232 decays into Thalium-208 and gives off very high energy radiation which would kill anyone near it, as well as damage any electronics in the vicinity (this is also why making bombs out of thorium are not as big a threat). But if this can be overcome I think it'd be a great source of power.

Am I the only one who can't actually read the article? All I get is a "sign-up" floater :(

I got it without (to my knowledge) overflowing any limits for any reasonable time period.

Do a Google search for the headline and click on the article that way. Or forge the 'Referer' header.

Try incognito mode

That happens after you reach a monthly limit of economist.com articles, I believe. Easily bypassed by most on HN...

Clear the site cookies and reload the page.

Brilliant fairly technical presentation on Thorium.


This more or less sold me on the idea years ago.

What about the radioactive waste? All nuclear reactors produce waste (finally when disassembled after the reactors' end of life). I find it strange to search for more efficient reactor styles, while the waste problem is not solved.

Most of the waste from traditional reactors is actually unspent fuel. Solid fuel rods only allow for about 1-2% energy conversion before the amount of transuranics and other contaminants built up and prevent safe operation.

The idea of the liquid fueled reactors is that you can easily change the fuel composition, ideally constantly reprocessing the fuel of contaminates, while letting the unburned fuel stay in place. This would drastically reduce the amount of waste generated (by orders of magnitude), and the 'unburnable' waste left over actually has some uses of its own (molybdenum 99 and bismuth 213).

Most of the waste is actually not the fission product itself, but everything else that is required to maintain the reactor aswell as the reactor itself.

The waste problem has been solved. We store it somewhere safe until we decide something better to do with it.

What hasn't been solved is the effects of of all our coal, gas, and oil usage that could be replaced by nuclear power. It makes all the sense in the world to be finding ways we can widely and safely deploy nuclear power worldwide to replace coal and gas power plants. Generating clean electricity is a requisite for wide spread electric or hydrogen cars to stop burning gasoline.

If you believe that coal and gas burning is bad for the environment, then we need nuclear power urgently and widely, energy needs are only going to go up and the only alternative to nuclear is burning more fossil fuels. I find it absolutely absurd that people worry more about nuclear waste than atmosphere pollution currently happening. I think we could store a few hundred years of nuclear waste on Antarctica til technology figures out what to do with it, even if that's just shooting it into the sun. I choose safely storing nuclear waste for the future to deal with over continuing to burn billions of tons of coal and gas each year which is actively killing about a million people per year. (WHO 2008)


Thus, solving the problem once and for all. ONCE AND FOR ALL!

I appreciate the Futurama reference but it is true. Nuclear "waste" is extremely valuable for use in upcoming reactor designs like MSRs that burn up significantly more of the long-lived waste. Keeping it stored temporarily until these reactors go live is the most prudent and efficient option.

There is waste with thorium reactors as well, so they need to be well run by competent people just as a conventional reactors. That said, the waste is easier to handle for several reasons, particularly in the liquid fuel type.

The waste in conventional reactors are of two types, fission procucts and higher actinides. The fision products are the result of splitted uranium atoms. These are intensively radioactive, with halflives from milliseconds to about 30 years.

Then there are higher actinides, with halflives up to tens of thousands of years. These are less radioactive, but still radioactive enough that they have to be safely stored. This storage must be safe for hundred of thousands of years, something that it is hard to guarantee. Fision products only need to be stored for about 600-800 years before they are no more radioactive than uranium ore. Thorium rectors produce virtually no higher actinides, so it is easier to find storage that is safe for the period it must stay out of reach. It is also less volume of the waste (but more concentrated, as the amount of radioactivity is about the same), since the fission products are not mixed with U238 as in conventional reactors. This means that less storage is needed, which also makes it easier to handle.

I do not mean the fission products. I mean every thing else, starting from the clothes for the staff, to maintanance materials and finally the reactor itself. A reactor produces far more waste than just the fission products.

It is solved - store it somewhere, or use it as a fuel for other reactors.

And the currently used alternatives (coal) produces way more waste (whole mountains of slightly radioactive, and slightly toxic dust leftovers from coal extraction build up near coal mines).

How do you use a used sponge that is radiactive waste as fission material in a reactor, or those pipes from the reactor itself?

Thorium molten salt reactors make waste reprocessing vastly easier and they produce significantly less "potent" waste products than Uranium solid fueled reactors do. This is important because MSRs could be used to vastly reduce the amount of waste built up so far, easing the storage problem enormously.

the article talks about waste, namely how thorium reactors burn longer lived radioactive elements into shorter lived elements so tens of thousands of years of waste turns into hundreds of years of waste

Ah, Thorium articles. Guaranteed views from nerds, a great way to discover a cohort in your audience, and an easy template to follow (e.g. "it'd be so great, but adoption is 10 years away").

(Don't vote me up for this either. Dismissive first posts are another HN trope, so in this regard I'm as guilty as The Economist.)

Pff. If 'molten salt' reactors are an inch closer in 10 years, I will eat my hat. The idea is only slightly more appealing than having the reactor fly around under it's own power.

What makes you think The Economist is interested in probing the nerdosphere? Would Tesla, Apple, etc., be more effective? For sure, the '... adoption is 10 years away' thing is funny. Makes me reminisce for Popular Science.

If I were to guess; they are advertising where their technological sympathies lie. It is more about managing their brand than probing an audience.


That was a pretty fun one: http://en.wikipedia.org/wiki/Project_Pluto

This was better:


If we hadn't canceled it we'd be colonizing the Solar System by now.

Ahem... http://en.wikipedia.org/wiki/Convair_NB-36H

... speaking of flying nuclear reactors

Oh wow, basically its Chernobyl with wings. Don't miss this, its pure gold: http://www.merkle.com/pluto/pluto.html

Quote: "Meanwhile, at the Pentagon, Pluto's sponsors were having second thoughts about the project. Since the missile would be launched from U.S. territory and had to fly low over America's allies in order to avoid detection on its way to the Soviet Union, some military planners began to wonder if it might not be almost as much a threat to the allies. Even before it began dropping bombs on our enemies Pluto would have deafened, flattened, and irradiated our friends. (The noise level on the ground as Pluto went by overhead was expected to be about 150 decibels; by comparison, the Saturn V rocket, which sent astronauts to the moon, produced 200 decibels at full thrust.) Ruptured eardrums, of course, would have been the least of your problems if you were unlucky enough to be underneath the unshielded reactor when it went by, literally roasting chickens in the barnyard."

I was suggesting that The Economist knows how to write link bait articles that generate views, and that this article which offers nothing new is an application of that skill.

Of course I was down-voted: HN's readership doesn't like to be told that it's a trivially exploitable source of clicks.

you may be right but you are wrong

The buzz for thorium reactors is made by people who want to sell thorium reactors.

And repeated by those who don't want this civilization to end when we either run out of fuel or break the ecosystem.

Perhaps the folks wanting to sell such reactors feel that way because they honestly believe that it's a superior alternative?
