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?
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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