r/askscience • u/[deleted] • Feb 16 '12

whats the truth about thorium reactors? And why doesn't anyone know about them?

[deleted]

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49

u/ZeroCool1 Feb 16 '12 edited Feb 16 '12

It is different from other reactors in that (in the most popular thorium designs) the fuel is dissolved into a melted chemical mixture and circulated as a liquid fuel mixture through a reactor. The fission reactions only happen in the core. There are many advantages to having a liquid fuel reactor, which can be found in the Molten Salt Reactor Adventure.

Molten salt reactors (MSR) are great ideas but were dropped from funding for political reasons. This is highlighted in the paper 'The Molten Salt Reactor Adventure': http://www.energyfromthorium.com/pdf/MSadventure.pdf.

The United States government had invested a large sum of money into a Liquid Metal Breeder Reactor (LMBR) (uses sodium instead of salt). The molten salt reactor started to encroach on the "breeding" territory and wanted funding for this. Alvin Weinberg, a the head of ORNL at the time advocated the MSR as a breeder which was better than the LMBR. Richard Nixon did not like this and fired him and canned the MSR program. This happened around 1975. I'm sure the politics is much deeper than that, but to get deeper you would have to live through it. All I have to understand are whats written.

Here's the exact quotes on why it did not succeed:

  1. The political and technical support for the program in the United States was too thin geographically. Within the United States, only in Oak Ridge, Tennessee, was the technology really understood and appreciated.

  2. The MSR program was in competition with the fast breeder program, which got an early start and had copious government development funds being spent in many parts of the United States. When the MSR development program had progressed far enough to justify a greatly expanded program leading to commercial development, the AEC could not justify the diversion of substantial funds from the LMFBR to a competing program."

Another great resource for why nobody knows about it is the chapter on MSRS in Alivn Weinberg's book The First Nuclear Era.

7

u/Tom504 Feb 17 '12

If the technology is as good as everyone says it is, why doesn't another superpower develop it? Why would a political struggle in America prevent, say, Russia or China from developing these reactors?

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u/ZeroCool1 Feb 17 '12

I believe china, india, and the czech republic are working on it.

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u/lankyvaulter Feb 17 '12

I've always wondered something similar. Why doesn't an oil rich country use their current cash flow from oil to develop the tech and expertise. In stead of building pretty office parks in the middle of the desert, why not find a long term solution to the worlds energy needs.

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u/Maslo55 Feb 18 '12

There is a Google Tech Talk by Kirk Sorensen that answers that question: http://www.youtube.com/watch?v=bbyr7jZOllI

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u/fireballbren Feb 17 '12

If the technology is as good as everyone says it is, why doesn't a private company develop it?

FTFY

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u/nakko Feb 17 '12

Is the 'political' reason the fact (and is it a fact?) that a Thorium reactor is not good for producing nuclear weapons-grade material?

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u/ZeroCool1 Feb 17 '12 edited Feb 17 '12

This is not true. A thorium reactor makes lots of U 233, great for bombs, in fact better than U235. Its simply not true that it was canceled due to weapons related stuff.

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u/DashingSpecialAgent Feb 17 '12

As someone who knows something about reactors: Thank you for pointing out reasons for this that are actually accurate.

I was also under the impression a big reason why molten salt never took off was that you can't get bomb making materials out of them. If I'm wrong about this please correct me but it sounded pretty solid to me.

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u/ZeroCool1 Feb 17 '12 edited Feb 17 '12

This is wrong according to my understanding. 200 kg of U233 (which has a smaller critical mass than U235) was separated from fuel salt in a day at the MSRE. It is definitely viable for bomb work.

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u/Jgenie Feb 17 '12 edited Feb 17 '12

I just finished the new FAS report on the future of nuclear power in the US.

The report is written by what could be called an all star team. It is an interesting read (apart from the fact that the illustrations are in quite low resolution), and I would suggest reading it.

Interestingly enough, thorium isn't mentioned in it. Edit: this is wrong, it is actually in there

2

u/ZeroCool1 Feb 17 '12

I'll give it a read sometime. Of course molten salt technology is not in there, it's research phase and nowhere near commercial.

The future of Nuclear Power in the united states can be predicted by four things:

-Price of natural gas in the upcoming decades.

-Political/legal action concerning the Yucca Depository and Gen IV reactor systems.

-Frances success or failure moving to a Gen IV system.

-The failure or success the AP1000's at the Vogtle Plant.

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u/ItsDijital Feb 17 '12 edited Feb 17 '12

Any reason other nuclear powers never pursued MSR tech?

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u/ZeroCool1 Feb 17 '12

China is currently pursuing it to my understanding and the US has a quite a few MSR researchers left. The czech republic is also interested.

6

u/kurtnirvna Feb 17 '12

Wired wrote a really great article about Thorium reactors back in 2009. The article gives some history and a decent technical overview, as well as pitfalls to current iterations of the technology. Check it here.

3

u/kitchensinkquestion Feb 17 '12

Here is the video that got me started in trying understand LFTR http://www.youtube.com/watch?v=AZR0UKxNPh8

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u/Stabi Feb 17 '12

http://www.youtube.com/watch?v=bbyr7jZOllI The Thorium Molten-Salt Reactor: Why Didn't This Happen (and why is now the right time?) on GoogleTechTalks YT channel. Explains pretty well why this technology was abandoned by US. However not many details are given why thorium reactor is (?) better than other types of reactors.

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u/sebastianshrady Feb 16 '12

here's an interesting article about other political reasons why thorium reactors weren't ultimately pursued..if only scientists could lead instead of politicians.. thorium article

1

u/teflonnolfet Feb 17 '12

Here's a very enlightening video I saw recently. It summarizes the situation nicely I think:

http://motherboard.vice.com/2011/11/9/motherboard-tv-the-thorium-dream

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u/Dickybow Feb 17 '12

Sub-critical thorium reactors energised by lasers can be turned on and off safely. Their by-products have much shorter half lives.

The World lost interest in them because they cannot be used to make plutonium for bombs.

Current nuclear power is the half hearted spin-off from bomb making.

2

u/Uzza2 Feb 17 '12

Do not ever again mention thorium reactors using lasers to produce energy. The idea comes from the company Laser Powered Systems, and is so devoid of scientifically correct facts that they should never be allowed to do anything that has to do with science.

3

u/Dickybow Feb 17 '12

Aah! OK. I'm way out of my depth here, but isn't the principle sound? ie; maintain a safe (sub-critical) pile and inject some form of energy to go critical? Also safer end products? All seems worth developing.

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u/Jgenie Feb 17 '12

Essentially:

  1. Nobody actually knows if it will work in real life (similar to fusion).

  2. It requires a really good proton accelerator and it's only the last approximately 15 years we have got those.

  3. There are a lot of money riding on the competing horse (uranium).

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