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[39] Using modern values he found that to be "equal to about a microsecond, which makes the point about the rapidity of fission with fact [sic] neutrons". [39] In the original memorandum, if the neutrons had velocities of 10 9 cm/s, then they would have an average time between fission collisions of 2.6 × 10 −9 s. Therefore, Bernstein's time ...
The tamper had a radius of 17.5 centimetres (6.9 in) and a thickness of 11.3 centimetres (4.4 in), for a mass of 317 kilograms (699 lb). This was about 3.5 times the mass of the fissile material used. Tungsten carbide has a high density and a low neutron absorbency cross section.
has units of mass, and it is the only parameter in the Standard Model that is not dimensionless. It is also much smaller than the Planck scale and about twice the Higgs mass, setting the scale for the mass of all other particles in the Standard Model. This is the only real fine-tuning to a small nonzero value in the Standard Model.
A critical mass is a mass of fissile material that self-sustains a fission chain reaction. In this case, known as criticality, k = 1. A steady rate of spontaneous fission causes a proportionally steady level of neutron activity. A supercritical mass is a mass which, once fission has started, will proceed at an increasing rate. [1]
The mass excess of a nuclide is the difference between its actual mass and its mass number in daltons.It is one of the predominant methods for tabulating nuclear mass. The mass of an atomic nucleus is well approximated (less than 0.1% difference for most nuclides) by its mass number, which indicates that most of the mass of a nucleus arises from mass of its constituent protons and neutrons.
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 symbols are defined as: [3], and are the average number of neutrons produced per fission in the medium (2.43 for uranium-235). and are the microscopic fission and absorption thermal cross sections for fuel, respectively.
Little Boy was a type of atomic bomb created by the United States as part of the Manhattan Project during World War II.The name is also often used to describe the specific bomb (L-11) used in the bombing of the Japanese city of Hiroshima by the Boeing B-29 Superfortress Enola Gay on 6 August 1945, making it the first nuclear weapon used in warfare, and the second nuclear explosion in history ...