Useful LFTR Fission By-Products

Fission of 1000 kg U-233 produces several chemicals essential for industry, readily extracted from a LFTR, including 150kg xenon, 125kg neodymium (high-strength magnets), 20kg medical molybdenum-99, 20kg radiostrontium, zirconium, rhodium, ruthenium, and palladium.

LFTRs also produce non-fissile Pu-238, that conventional reactors can’t produce isolated from highly fissile Plutonium-239; Pu-238 is needed for radioisotope power such as for NASA deep space exploration vehicles (none left, only Th to U-233 makes Pu-238 w/o Pu-239).

(Extracting these from fuel rods in a solid fuel reactor would be extremely difficult.)

Radioactive isotopes are needed for medical treatment, including highly-targeted cancer treatments. These are currently very rare, since they have half-lives of a few days. LFTRs would produce these as part of the decay of U-233, and they would be easy to remove from the fuel salt.

Iodine-131 is used to treat cancers of the thyroid.

Thorium-229 for cancer treatments, decays to Bismuth-213, which decays through alpha emission (unlike most of the fission products that decay through beta emission). By binding Bi-213 to an antibody, it can be directed swiftly to a cancerous cell. The alpha decay of the Bi-213 then has a high probability of killing the cancer cell. (Very small amount/treatment, but decays fast to Bi-209.)

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8 thoughts on “Useful LFTR Fission By-Products

  1. Vina Oviedo

    I lately came across your blog and have been learning along. I thought I would leave my 1st comment. I do not know what to say except that I’ve loved reading. Fine blog. I will keep visiting this blog extremely usually.

    Reply
  2. Austin hykin

    I am doing a report on LFTR and I truly believe in it but I need to know per 1000kg of thorium (or uranium 233) how many kg of radioactive material is produced and can this number of kg of nuclear waste be reduced by running it back through the LFTR, if so how.

    Reply
    1. glerner Post author

      See the section on this blog on nuclear waste, I’ve covered it in enough detail for most people (but not enough for regulators, LFTR designers, etc). 300lbs of 350-year waste per GW-year.

      All the transuranic materials simple remain in the reactor until they fission.

      Some of the 350 year waste can absorb neutrons to become shorter term waste, but I’m not sure if that could happen inside the LFTR (neutron economy is a concern) or if it would take an external neutron source.

      Ask at the Energy from Thorium Forum, http://www.energyfromthorium.com/forum/index.php

      Reply
    2. glerner Post author

      Since all the uranium and other transuranic elements are easily left in the reactor, circulating through the core until they fission, essentially all of the long-term waste is “reduced by running it back through the LFTR”.

      The fission byproducts from 1000kg of Th converted to U233 (or 1000kg U235, U238, or Pu239) would be 1000kg, 83% has half-lives under 1 year, 17% has half lives 35 years (10 half lives is a good guideline for how long needs to be stored, 1/1024 the radioactivity).

      I don’t know the details on each isotope of each element that could be produced in a LFTR (or by a LWR and put in a LFTR).

      There are some isotopes that if absorb another neutron have shorter half lives. Whether those would be left in the reactor to absorb a neutron, or taken out so the neutron would be captured for example to breed fuel, is an engineering decision. Cesium is one of those that might get neutron bombarding to shorten the half life, either in a LFTR or from another neutron source.

      Reply
    3. glerner Post author

      As said on other pages, the LFTR waste, or any MSR waste, would be 1000kg (the original 1000kg minus a very tiny amount of mass converted to energy). The fission byproducts of U-233 and U-235 are similar, Wikipedia has lists of the decay chains and the fission byproducts. The probabilities of each fission byproduct are known, just need to crunch those numbers.

      But the MSR waste would not contain uranium like LWR waste; 83% below safe radiation levels in under 10 years; 17% (about 375 lbs, low radiation, non-fissionable) store for 350 years. Depending on the specific MSR design used, and type of electric generator, about 800kg-1000kg fuel would produce 1 giga-watt electricity.

      Remember, in any MSR, the fuel salt is molten, so uranium, transuranic elements, and elements with isotopes with long half-lives can be separated and would be returned to the reactor core (for fissioning, or for decay by neutron bombardment). Depending on the MSR design (in-reactor or external batch fuel processing), they never leave the reactor.

      In LWR waste, uranium is by far the largest by kg (over 95%); that uranium could be used as MSR fuel, no “reprocessing” needed, no “enrichment” needed, the hard part would be mechanically/chemically removing the uranium from the fuel rods & pellets: U235 would fission, U238 would absorb a neutron and become Pu239 which fissions, fission byproducts could be removed by the same processes the MSR uses, either in the reactor or separate equipment at the LWR waste storage site.

      A LFTR could handle small amounts of LWR waste (just add less thorium, the reactor self-adjusts since the fuel expands/contracts with changes in heat); a “waste burning” MSR would be configured for LWR waste as fuel, neutron economy adjusted, no thorium-to-uranium blanket.

      Reply
  3. soup_fly

    Using he fission products is a nice idea, but for most of them it currently is not economic, at least when reprocessing LWR fuel.
    Reusing the xenon probably will work, since it more of less needs to be separated anyway. However the value is not really significant.

    The radioisotopes that are used in medical applications need a high purity – the wast from the LFTR just delivers a mixture of isotopes. There is essentially no alternative to irradiating target materials of high purity. Even the Pu-238 may not be pure enough to be really valuable – so it’s likely better to remove the neptunium before it becomes Pu-238. Than a second dedicated reactor can make pure Pu-238 from this.

    Neodymium is mainly expensive because it’s hard to separate from other rare earth elements and thorium. So it’s likely not a good idea to do the rather dirty chemical separation with a highly radioactive mixture of rare earth material.

    The one really valuable isotope, worth selling it may be tritium – it’s only some 100 g a year, but quite expensive.

    Reply
    1. glerner Post author

      I’m not a chemist, but seems to me there are very few elements generated in LFTR, whether using Th-U233, U235 or U238-Pu239. Should be standard chemical methods for separating them from the molten salt.

      Reprocessing LWR fuel seems much harder, including the fuel rod is designed to trap all fission byproducts (and TRISO adds several more layers of trapping). Read more on the fluoride volatility and distillation processes a LFTR would use, and ask questions on the Energy From Thorium boards.

      But if it isn’t economical to separate some of the elements, it would still be simple to let them decay for the few years needed to not be radioactive, and then just drop them into whatever storage container is appropriate.

      All the discussions I’ve seen talk about this like it is easy to separate these chemicals, and molten salt reactors are the Only way to get some of them (aside from very expensive specialty reactors).

      Reply
  4. Peggy Horn

    Very interested in Thorium 229 for cancer treatments. I URGENTLY need any information you have on potential cancer treatments available. I am writing in 2014 – have there been any updates on this? Any progress?
    I would appreciate any information!

    Thank you,

    Peggy Horn

    Reply

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