Note: This post will be a brief summary of the thorium fuel cycle for power production. It will be expanded in later weeks (I will post the link within this article).

Thorium power is based upon the use of Th-232; an isotope which occurs naturally. It is a fertile isotope which means that it can be used to create the fissile (or fissionable) isotope U-233 by absorbing a nucleon. U-233 is largely responsible for the heat generated in a thorium reactor as opposed to U-235 and Pu-239 for a typical light water reactor (LWR).

credit: snorgcontent.com

credit: snorgcontent.com

Benefits

  • no enrichment needed – after the initiation of the closed fuel cycle, no centrifuge facilities or laser enrichment is necessary because thorium ore has no fissile component
  • greater abundance – thorium is 3 to 4 times as abundant as uranium, which means more opportunity to supply reactors
  • thermal breeding is possible – reactors that use thermal neutrons experience less material damage compared to other generation IV reactors that require the use of fast neutrons
  • better anti-proliferation properties – less Pu-239 and U-235 are created and no enrichment is needed which means it’s harder to collect enough material to create a weapon; high gamma emission also makes handling U-233 difficult
  • better waste properties – less plutonium and other actinides means that the wastes generally has shorter half-lives
  • less waste – ideally, the entire amount of thorium is “burned” as opposed to 5%-10% of typical uranium fuel

Drawbacks

  • need fissile material (U-235 or Pu-239) to start the cycle – after the first irradiation, the resultant U-233 is used
  • high gamma emissions – this makes remote handling necessary while also making weapons use difficult; it also means certain components are more vulnerable
  • unproven – very few facilities have experimented with thorium, so it will be expensive to research and need to clear more regulatory hurdles
    • also, the chemistry for reprocessing is different from uranium fuel cycle requiring more research
  • U-233 is fissile – that means it can be used in weapons; it’d be hard, but possible (the US has already done it)
  • liquid fuels – all LWRs operate with solid uranium oxide fuel; new fuel materials mean new challenges
    • while it’s possible to use solid thorium oxide in LWRs, it’d be much harder
  • recycling is necessary – this will add costs and increase the opportunity for countries to use U-233 for weapons
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