fissile vs thermonuclear

fissile

adj
  • Capable of sustaining a nuclear fission chain reaction. 

  • Able to be split. 

  • Easily split along a grain. 

thermonuclear

adj
  • Of, or relating to the use of atomic weapons based on such fusion, especially as distinguished from those based on fission. 

  • Of, or relating to the fusion of atomic nuclei at high temperatures. 

noun
  • A thermonuclear weapon. 

How often have the words fissile and thermonuclear occurred in a corpus of books? (source: Google Ngram Viewer )