~200MWt reactors are common in large nuclear submarines and weight about 2000 tons, not sure how much of that (if any) is shielding, but the figures for reactor

~200MWt reactors are common in large nuclear submarines and weight about 2000 tons, not sure how much of that (if any) is shielding, but the figures for reactor weight sound high. I’d imagine for joules/kg nuclear would be hard to beat.