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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.
The two fissile materials used in nuclear weapons are: 235 U, also known as highly enriched uranium (HEU), "oralloy" meaning "Oak Ridge alloy", [12] or "25" (a combination of the last digit of the atomic number of uranium-235, which is 92, and the last digit of its mass number, which is 235); and 239 Pu, also known as plutonium-239, or "49 ...
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.
The most common chemical process, PUREX (Plutonium–URanium EXtraction), reprocesses spent nuclear fuel to extract plutonium and uranium which can be used to form a mixed oxide (MOX) fuel for reuse in nuclear reactors. Weapons-grade plutonium can be added to the fuel mix.
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 "Thin Man" design was an early nuclear weapon design proposed before plutonium had been successfully bred in a nuclear reactor from the irradiation of uranium-238. It was assumed that plutonium, like uranium-235 , could be assembled into a critical mass by a gun-type method, which involved shooting one sub-critical piece into another.
Fat Man Replica of the original Fat Man bomb Type Nuclear fission gravity bomb Place of origin United States Production history Designer Los Alamos Laboratory Produced 1945–1949 No. built 120 Specifications Mass 10,300 pounds (4,670 kg) Length 128 inches (3.3 m) Diameter 60 inches (1.5 m) Filling Plutonium Filling weight 6.2 kg Blast yield 21 kt (88 TJ) "Fat Man" (also known as Mark III) was ...
At the time, the critical masses of uranium (and more particularly plutonium) were not precisely known. It was thought that uranium with a uranium tamper might be about 25 kg, while that of plutonium would be about 5 kg. [3] The Little Boy uranium bomb used in the atomic bombing of Hiroshima had a tungsten carbide tamper.