Ultralight Reactors

I found a document (or at least its summary) claiming a reactor with a fuel mass of ~20 grams of Am242m. Admittedly this is using a neutron reflector, but achieves fission with 450 times less mass than the base sphere mass. Assuming this ratio can be applied to uranium-233 then ~34 g should be adequate with proper reflectors.



www.ans.org/pubs/journals/nse/a_2215 (locked behind a paywall, only the abstract)