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Moreover, 239 Pu and 240 Pu cannot be chemically distinguished, so expensive and difficult isotope separation would be necessary to separate them. Weapons-grade plutonium is defined as containing no more than 7% 240 Pu; this is achieved by only exposing 238 U to neutron sources for short periods of time to minimize the 240 Pu produced.
In contrast, the generic civilian Pressurized water reactor, routinely does (typical for 2015 Generation II reactor) 45 GWd/tU of burnup, resulting in the purity of Pu-239 being 50.5%, alongside a Pu-240 content of 25.2%, [5] [6] The remaining portion includes much more of the heat generating Pu-238 and Pu-241 isotopes than are to be found in ...
Plutonium is a chemical element; it has symbol Pu and atomic number 94. It is a silvery-gray actinide metal that tarnishes when exposed to air, and forms a dull coating when oxidized. The element normally exhibits six allotropes and four oxidation states. It reacts with carbon, halogens, nitrogen, silicon, and hydrogen.
239 Pu is virtually nonexistent in nature. It is made by bombarding uranium-238 with neutrons. Uranium-238 is present in quantity in most reactor fuel; hence 239 Pu is continuously made in these reactors. Since 239 Pu can itself be split by neutrons to release energy, 239 Pu provides a portion of the energy generation in a nuclear reactor.
The plutonium-239 (or the fissile uranium-235) fissile cross-section is much smaller in a fast spectrum than in a thermal spectrum, as is the ratio between the 239 Pu/ 235 U fission cross-section and the 238 U absorption cross-section.
Fission product yields by mass for thermal neutron fission of U-235, Pu-239, a combination of the two typical of current nuclear power reactors, and U-233 used in the thorium fuel cycle If a graph of the mass or mole yield of fission products against the atomic number of the fragments is drawn then it has two peaks, one in the area zirconium ...
However, the Hanford reactors would only yield about 0.025% of fissile 239 Pu, from the fissile 235 U content of 0.7% in the natural uranium fuel slugs. This corresponds to a "conversion ratio" of 1/30. [11]
Pu, and eventually fissile 239 Pu and heavier isotopes of plutonium. The 237 Np can be removed and stored as waste or retained and transmuted to plutonium, where more of it fissions, while the remainder becomes 242 Pu, then americium and curium, which in turn can be removed as waste or returned to reactors for further transmutation and fission.