IN the 90’s I recall reading about a fuel design that suspended tiny flakes in a high density carbon pellet.
https://www.energy.gov/ne/articles/triso-particles-most-robust-nuclear-fuel-earth
The pellets are combined and encapsulated into pebbles a little smaller than a tennis ball. The resulting so-called pebble bed nuclear reactor uses a circulating inert gas to carry heat away to a turbine that generates electricity. Although not yet developed to routine commercial use, the design is said to be inherently safer than the current pressurized water reactors now in use.