Why isn't Thorium used for reactor fuel rods?

  • #1

Main Question or Discussion Point

Is THORIUM a viable alternative Reactor Fuel? Seems like URANIUM and PLUTONIUM are to easily weaponized.
 

Answers and Replies

  • #2
DrDu
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Thorium itself isn't fissible. There were some breeding reactor concepts which produced U-233 from Th-232, but they required large quantities of U-235 and therefore also contained a large proliferation risk.
 
  • #4
Astronuc
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Is THORIUM a viable alternative Reactor Fuel?
https://www.gen-4.org/gif/upload/docs/application/pdf/2013-10/gif_egthoriumpaperfinal.pdfhttps://www.gen-4.org/gif/jcms/c_9359/msr
Folks have been thinking about thorium fuel cycles for the last 6 decades. The idea gets revived periodically, and nations such as India, China and others with substantial thorium deposits have active programs.

Thorium fuel was tested an Indian Point 1 starting around 1962, and on a limited basis in the Shippingport (LWBR) reactor in the late 1970s through early 1980s.
Fuel Summary Report: Shippingport Light Water Breeder Reactor
INEEL/EXT-98-00799 https://www.nrc.gov/docs/ML0923/ML092310709.pdf

MIT study (1999) - http://ltbridge.com/assets/15.pdf

http://www.barc.gov.in/reactor/tfc.html
 
Last edited:
  • #5
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In a light water reactor, thorium has less burnup per ton of fuel than uranium by a significant amount. It has a parasitic effect on its neutron economy which essentially wastes reactivity compared to uranium/plutonium.
 
  • #6
Thorium is "fertile" not fissile, and needs to be converted to U233 before it can be used, in which process U232 is also produced, in small quantities, but enough to wreak havoc on weapons use as it is a hard gamma emitter, detectable from far away.
The premise of Thorium use is in Molten Salt Reactors, either once-thru, or a breeder where fertile material is converted, and byproducts are removed in-line, some for use in other applications. The increased temps in MSRs allows for use in industrial processes, and/or extremely reduced size CO2 turbines, desalination of sea water, or use air to dissipate waste heat, allowing arid areas for sites.
Avoiding water with its weak covalent H / O2 bond is a bonus, both from a stability, efficiency, and safety point t of view.
 
  • #7
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Thorium is "fertile" not fissile, and needs to be converted to U233 before it can be used, in which process U232 is also produced, in small quantities, but enough to wreak havoc on weapons use as it is a hard gamma emitter, detectable from far away.
How is this a problem?
U-233 has a small critical mass, comparable to Pu-239. And lower radioactivity.
And lower spontaneous fission rate. An U-233 bomb would actually seem relatively easy to build.
 
  • #8
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Quite a necromancy, the original question is already three years old...

Thorium was used in commercial reactors already. Indian Point I. has many to say about the economical consequences of using thorium being a lone wolf in a conservative industry, and also there were several other 'live' tests with mixed-thorium fuels: it happens a few times in every decade.

I think the most correct answer for the original question would be: it is not used because it does not worth the effort yet.
 
  • #9
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How is this a problem?
U-233 has a small critical mass, comparable to Pu-239. And lower radioactivity.
And lower spontaneous fission rate. An U-233 bomb would actually seem relatively easy to build.
Intense gamma rays make handling the material much more difficult and it makes the activities much easier to detect. Even if you keep humans out of the process it means you have to make everything more radiation tolerant. You also have to worry about the gamma rays producing neutrons and so on.
 
  • #10

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