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The main decay mode for isotopes heavier than 244 Pu, along with 241 Pu and 243 Pu, is beta emission, forming americium isotopes (95 protons). Plutonium-241 is the parent isotope of the neptunium series, decaying to americium-241 via beta emission. [11] [26] Plutonium-238 and 239 are the most widely synthesized isotopes.
Plutonium-239 is the primary fissile isotope used for the production of nuclear weapons, although uranium-235 is also used for that purpose. Plutonium-239 is also one of the three main isotopes demonstrated usable as fuel in thermal spectrum nuclear reactors, along with uranium-235 and uranium-233. Plutonium-239 has a half-life of 24,110 years. [1]
Plutonium-242 (242 Pu or Pu-242) is the second longest-lived isotope of plutonium, with a half-life of 375,000 years. The half-life of 242 Pu is about 15 times that of 239 Pu; so it is one-fifteenth as radioactive, and not one of the larger contributors to nuclear waste radioactivity.
Plutonium-238 (238 Pu or Pu-238) is a radioactive isotope of plutonium that has a half-life of 87.7 years.. Plutonium-238 is a very powerful alpha emitter; as alpha particles are easily blocked, this makes the plutonium-238 isotope suitable for usage in radioisotope thermoelectric generators (RTGs) and radioisotope heater units.
Fission product yields by mass for thermal neutron fission of U-235 and Pu-239 (the two typical of current nuclear power reactors) and U-233 (used in the thorium cycle). This page discusses each of the main elements in the mixture of fission products produced by nuclear fission of the common nuclear fuels uranium and plutonium.
Plutonium-240 has a high rate of spontaneous fission, raising the background neutron radiation of plutonium. Plutonium is graded by proportion of 240 Pu: weapons grade (<7%), fuel grade (7–19%) and reactor grade (>19%). Lower grades are less suited for bombs and thermal reactors but can fuel fast reactors.
Plutonium (Pu, atomic number 94), first synthesized in 1940, is another such element. It is the element with the largest number of protons (atomic number) to occur in nature, but it does so in such tiny quantities that it is far more practical to synthesize it. Plutonium is known mainly for its use in atomic bombs and nuclear reactors. [4]
Plutonium-240 (240 Pu or Pu-240) is an isotope of plutonium formed when plutonium-239 captures a neutron. The detection of its spontaneous fission led to its discovery in 1944 at Los Alamos and had important consequences for the Manhattan Project. [3] 240 Pu undergoes spontaneous fission as a secondary decay mode at a small but significant rate.