"Popular speculation about californium as a weapon material has usually centered on Cf-252 due to its neutron-emitting celebrity. Its comparatively short half-l

"Popular speculation about californium as a weapon material has usually centered on Cf-252 due to its neutron-emitting celebrity. Its comparatively short half-life (for weapons purposes), intense and penetrating neutron radioactivity, and high thermal output make it quite unsuitable for this however." http://nuclearweaponarchive.org/Nwfaq/Nfaq6.html#nfaq6.2 http://nuclearweaponarchive.org/Nwfaq/Nfaq6.html#nfaq6.2 Also, 6.9cm isn't that far from the 10cm needed with Plutonium...