Alternative RTG Fuel: Exploring Pb210, Pu241, Ac227, Cm242, and Pm147

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Discussion Overview

The discussion revolves around alternative radioisotope thermoelectric generator (RTG) fuels, specifically examining isotopes such as Pb210, Pu241, Ac227, Cm242, and Pm147. Participants explore the potential advantages and challenges of these isotopes for medium to long-term space missions, including their production methods and power output characteristics.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant notes that Pb210 could be advantageous due to its longer half-life compared to Po210, questioning the feasibility of collecting it from lead-cooled reactors.
  • Another participant suggests that Pu241, while similar to Am241, could provide a slight power boost, prompting inquiries about its production and application.
  • Ac227 is mentioned as having a long decay chain that may yield significant power per atom, with a call for novel mass production methods.
  • Cm242 is described as similar to Pu238, with an early power boost, raising questions about the difficulty of producing Pu238 through this method.
  • Concerns are raised regarding Pm147's reported low power density despite its short half-life, with a participant expressing confusion over the accuracy of this information.
  • One participant emphasizes the advantages of 238Pu's alpha decay and its long-living daughter isotopes, which facilitate easier radiation shielding compared to other isotopes.
  • Another participant mentions the European Space Agency's shift towards Am-241 sources, acknowledging its lower power density but suggesting that improved RTG designs could mitigate this issue.
  • There is a discussion about the limitations of using Am-241 for interstellar missions due to its half-life, with a participant arguing it is more suitable for interplanetary missions.
  • Concerns are raised about the scalability of producing isotopes like Am-241 from nuclear reactors, with a suggestion that extracting it from waste could be a viable option.

Areas of Agreement / Disagreement

Participants express a range of views on the suitability and production of various isotopes for RTG applications. There is no consensus on which isotope is definitively the best choice, and discussions reflect differing opinions on the feasibility and implications of using these alternative fuels.

Contextual Notes

Participants highlight various assumptions regarding the production and power output of the discussed isotopes, indicating that further exploration is needed to clarify these aspects. The discussion does not resolve the complexities involved in the production and application of these isotopes.

dgjxqz
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I heard that Pu238 has limited production capacity.
Apart from those widely discussed, I would be curious as of why these are rarely brought up:
  • Pb210 is essentially Po210 with a longer half-life, which is more suitable for medium lifespan missions. How much Pb210 can be collected from a lead cooled reactor?
  • Pu241 is essentially Am241, but it could give a slight power boost.
  • Ac227 has a long decay chain which gives more (most?) power per atom. Any novel way for mass production?
  • Cm242 is essentially Pu238, in addition to early power boost. Is it much harder to produce Pu238 this way?
  • Pm147 has been discussed, but some sources give an unreasonably low power density (<1w/g) for its short half-life. Are they mistaken, or there is something I don't understand?

My assumption is:
  1. spent fission fuel can be reprocessed promptly,
  2. further decay of daughter isotopes contribute to total power output.
 
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238Pu has a high-energetic alpha decay to a long-living daughter isotope (which has the same features again), that makes radiation shielding easy. Most other isotopes have beta decays or high probabilities for gamma decays in their chains.
 
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Yeah, but 90Sr had been used and 241Am is being considered. I forgot to mention another assumption where anything close or less should be acceptable.
 
I believe the European Space Agency has announced they will be moving to Am-241 sources. They're less power dense, but with better RTG designs that is more than compensated for.

It's long lived, so it can support any interstellar mission. It alpha decays, so shielding is relatively easy. Production is, from what I've been told, fairly simple. I mean we produce it for smoke detectors as it is so I can't imagine up-scaling that process would be too difficult.
 
Apollo16 said:
It's long lived, so it can support any interstellar mission.
Any interplanetary missions. It is way too short-living to support interstellar missions unless you aim for something like Breakthrough Starshot with ~20% c.

It is produced in nuclear reactors. You cannot simply scale up the number of nuclear power plants in the world. You can extract more of this isotope out of their waste, however.
 

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