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Pu-239 is produced artificially in nuclear reactors when a neutron is absorbed by U-238, forming U-239, which then decays in a rapid two-step process into Pu-239. [22] It can then be separated from the uranium in a nuclear reprocessing plant. [23] Weapons-grade plutonium is defined as being predominantly Pu-239, typically about 93% Pu-239. [24]
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.
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.
The first production reactor that made 239 Pu was the X-10 Graphite Reactor. It went online in 1943 and was built at a facility in Oak Ridge that later became the Oak Ridge National Laboratory. [42] [note 5] In January 1944, workers laid the foundations for the first chemical separation building, T Plant located in 200-West.
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 ...
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.
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.
Pu-238 is an alpha emitter (so too is the bomb-grade Pu-239). Alpha particles can be stopped by paper. Indeed, you don’t want to inhale the stuff. But when they brought the 5 kg Pu-239 core to New Mexico for the Trinity shot, one of the physicists held it in his hand. It was even slightly warm because of the slight alpha radiation it was ...