Buckyball encased uranium - the smallest possible pebble bed

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SUMMARY

The discussion centers on the feasibility of using carbon buckyballs to encase uranium atoms in pebble bed reactors, exploring the potential for smaller pebble sizes. It references the encapsulation of cerium atoms in C80 buckyballs and questions whether a uranium atom could similarly be contained. The conversation highlights concerns regarding the structural integrity of the fullerene during fission, the practicality of fabrication, and the implications for neutron moderation. Ultimately, while the concept presents intriguing possibilities, practical challenges such as cost and material durability remain significant barriers.

PREREQUISITES
  • Understanding of pebble bed reactor design
  • Knowledge of carbon fullerenes and their properties
  • Familiarity with nuclear fission processes
  • Basic principles of neutron moderation
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  • Research the structural properties of C80 fullerenes under high-energy conditions
  • Investigate the thermal neutron absorption characteristics of carbon materials
  • Explore advancements in pebble bed reactor technology and fuel fabrication methods
  • Study the implications of low fuel-to-moderator ratios in nuclear reactors
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Nuclear engineers, materials scientists, and researchers interested in advanced reactor designs and the application of nanomaterials in nuclear fuel technology.

Jeremy Thomson
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Is there a trend in pebble bed reactors towards smaller pebble sizes? The smallest conceivable would be a carbon buckyball encasing a (single?) uranium atom. This Wikipedia article (https://en.wikipedia.org/wiki/Endohedral_fullerene) says two cerium atoms have been encapsulated in a c80 buckyball. So I guess there's enough room inside an arbitrarily large carbon fullerene for a uranium atom. I have no idea if this is actually possible. If fission were to occur would the fullerene necessarily split apart? I believe they are quite stretchy, of course fission is an enormous energy release. I just don't know the strength of c80 vs the energy of fission. I can't envisage buckynuke fuel being at all practical, most likely too expensive to fabricate. You'd need have some separator (piping) for coolant. Most likely the fullerene wouldn't survive fission so graphene fragments and loose fission products making mischief. But as a thought experiment would the carbon shell act well as a moderator? Or would the carbon shell act to protect the uranium from thermal neutrons, by bouncing neutrons away from the encapsulated uranium?
 
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Encasing one U atom in a shell of ~80 C atoms would make for a low fuel (U) to moderator (C) ratio.

Atomic bonds have energies on the order of eV, whereas the combined kinetic energy of the fission products is on the order of 168 MeV.
 
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