Plutonium-242 is one of the isotopes of plutonium, the second longest-lived, with a half-life of 373,300 years.242Pu's halflife is about 15 times as long as Pu-239's halflife; therefore, it is one-fifteenth as radioactive and not one of the larger contributors to nuclear waste radioactivity.242Pu's gamma ray emissions are also weaker than those of the other isotopes. It is not fissile (though it is fissionable by fast neutrons) and its neutron capture cross section is also low.