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Plutonium-242
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<p>Plutonium-242 (242Pu or Pu-242) is the second longest-lived <a href="/facts/Isotope_of_plutonium/ASACBN4x">isotope of plutonium</a>, with a <a href="/facts/Half-life/kGVH8BAB">half-life</a> of 375,000 years. The half-life of 242Pu is about 15 times that of 239Pu; so it is one-fifteenth as radioactive, and not one of the larger contributors to <a href="/facts/Nuclear_waste/MjYh5tlu">nuclear waste</a> radioactivity. 242Pu's <a href="/facts/Gamma_ray/5Drf913J">gamma ray</a> emissions are also weaker than those of the other isotopes. </p><p>It is not <a href="/facts/Fissile/XJR9qoxW">fissile</a> (but it is <a href="/facts/Fissionable/XJR9qoxW">fissionable</a> by <a href="/facts/Fast_neutron/UMKR4XgJ">fast neutrons</a>), and its <a href="/facts/Neutron_capture/elsFpM12">neutron capture</a> <a href="/facts/Neutron_cross-section/gAkJmXXA">cross section</a> is low. </p>