Examples from the Web for fissionable
The fissionable material was too valuable for other purposes.
"There are, or were, three chief sources of fissionable ores," Harkaman said.
Do you know why that planet was so extensively colonized by the Federation, when there don't seem to be any fissionable ores?
What makes the whole thing terrible is that the freighter is loaded with fissionable material exported from Ganymede.Jack of No Trades|Charles Cottrell
The neutron source, the neutron reflector, and one piece of fissionable material were in place.