Can 7Li Replace Na in Fast Breeder Reactors?

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Discussion Overview

The discussion centers on the potential use of lithium-7 (7Li) as a replacement for sodium (Na) in fast breeder reactors, exploring theoretical advantages, operational implications, and challenges associated with this substitution.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • Some participants propose that 7Li could be used instead of Na in fast breeder reactors, particularly in high-temperature compact designs.
  • One participant suggests that using a potassium Rankine cycle or Brayton cycle for power conversion could complement the use of 7Li.
  • Another participant highlights advantages of 7Li over Na, particularly in terms of safety and operational efficiency during leaks in a nuclear-gas Brayton turbine configuration.
  • Concerns are raised about the lack of enrichment facilities for 7Li, with one participant noting that the presence of lithium-6 (Li6) would negatively impact reactor neutronics.
  • Historical context is provided regarding the use of 7Li in the MSRE, which utilized leftover material from weapons production.

Areas of Agreement / Disagreement

Participants express differing views on the feasibility and practicality of using 7Li instead of Na, with some advocating for its advantages while others point out significant challenges, particularly regarding enrichment facilities and neutronic effects. The discussion remains unresolved regarding the overall viability of 7Li in this context.

Contextual Notes

Limitations include the current absence of operational enrichment facilities for 7Li and the potential negative impact of Li6 on reactor performance, which are not fully addressed in the discussion.

Efrain
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7Li can be used instead on Na on a fast breeder reactor?
 
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Efrain said:
7Li can be used instead on Na on a fast breeder reactor?
Yes - particularly for very high temperature compact fast reactors. A potassium Rankine cycle or Brayton cycle would then be used for power conversion.
 
Thank you Astronuc for your answer. Even when the 7Li is more expensive I see a lot of advantages over sodium.

For me the greatest advantage is that if a leak occurs on a nuclear-gas brayton turbine configuration, the compressed air can be bypassed from the heat exchanger to the combustion chamber, the reactor can be shut down, the leaked heat exchanger can be purged very fast with nitrogen or argon and the turbine continue working with gas which means very little plant downtime and less costly repairs.

After material cost issues, what will be the drawbacks for using 7Li instead Na on fast breeder reactors?
 
Last edited:
As of now, there are no enrichment facilities operating for Li7 enrichment. Li6 would kill the neutronics of any operating reactor.

The MSRE used Li7 left over from the weapons production (did they want Li6 or Li7 for weapons?); however, no such facility operates today; as far as I know.
 

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