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.