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For example, the British Magnox reactor, a Generation I gas cooled reactor(GCR) design, can rarely produce a fuel burnup of more than 2-5 GWd/t U. [28] [29] Therefore, the "reactor grade plutonium" and the purity of Pu-239 from discharged magnox reactors is approximately 80%, depending on the burn up value. [30]
Plutonium in the δ (delta) form normally exists in the 310 °C to 452 °C range but is stable at room temperature when alloyed with a small percentage of gallium, aluminium, or cerium, enhancing workability and allowing it to be welded. [19] The δ form has more typical metallic character, and is roughly as strong and malleable as aluminium. [17]
The pits of the first nuclear weapons were solid, with an urchin neutron initiator in their center. The Gadget and Fat Man used pits made of 6.2 kg of solid hot pressed plutonium-gallium alloy (at 400 °C and 200 MPa in steel dies – 750 °F and 29,000 psi) half-spheres of 9.2 cm (3.6 in) diameter, with a 2.5 cm (1 in) internal cavity for the initiator.
Plutonium in the delta (δ) phase [7] normally exists in the 310 °C to 452 °C range but is stable at room temperature when alloyed with a small percentage of gallium, aluminium, or cerium, enhancing workability and allowing it to be welded in weapons applications. The δ phase has more typical metallic character and is roughly as strong and ...
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]
To reduce the concentration of Pu-240 in the plutonium produced, weapons program plutonium production reactors (e.g. B Reactor) irradiate the uranium for a far shorter time than is normal for a nuclear power reactor. More precisely, weapons-grade plutonium is obtained from uranium irradiated to a low burnup.
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 δ phase is the least dense and most easily machinable. It is formed at temperatures of 310–452 °C at ambient pressure (1 atmosphere), and is thermodynamically unstable at lower temperatures. However, plutonium can be stabilized in the δ phase by alloying it with a small amount of another metal.