Stefan-Boltzmann Constant sigma 5.670 x 10^-5 erg/cm^2 K^4 sec Molar Gas Constant R 8.3145 x 10^7 erg/(mole K)īoltzmann Constant k 1.3806 x 10^-16 erg/K Speed of Light in Vacuum c 2.99792458 x 10^10 cm/sec Immediate Explosive Energy Kiloton kt 10^12 calories Microscopic Cross Section Barn b 10^-24 cm^2īiological Equivalent Dose Sievert Sv Grays*QĪbsorbed Gamma/X-Ray Dose Roentgen R 94 erg/g Total conversion of matter to energy: 21480.7643 kt/kgįission of 1.11 g U-235: 1 megawatt-day (thermal) Stanford University, Department of Mechanical Engineering, March 1981įusion of tritium and deuterium (50/50): 80.4 kt/kgįusion of lithium-6 deuteride: 64.0 kt/kg Fission Energy Release for 16 Fissioning Nuclides. The only authorized host site for the NWFAQ in English is the Nuclear Weapon Archive (">) Back to Main Index 12.0 Useful Tablesįission of 0.241 moles of material (1.45x10^23 nuclei)īased on: Sher, R. Unauthorized host sites are expressly forbidden. Only authorized host sites may make this document publicly available on the Internet through the World Wide Web, anonymous FTP, or This material may be excerpted, quoted, or distributed freely provided that attribution to the author (Carey Sublette), theĭocument name (Nuclear Weapons Frequently Asked Questions) and this copyright notice is clearly preserved, and the URL of this website is included: The bomb was made in the form of a sphere with pieces of plutonium, each below the critical mass, at the edge of the sphere.Section 12.0 Useful Tables Section 12.0 Useful Tables Nuclear Weapons Frequently Asked Questions Therefore, scientists developed a plutonium-239 bomb because Pu-239 is more fissionable than U-235 and thus requires a smaller critical mass. When one piece in the form of a bullet is fired into the second piece, the critical mass is exceeded and a chain reaction is produced.Īn important obstacle to the U-235 bomb is the production of a critical mass of fissionable material. The original design required two pieces of U-235 below the critical mass. When the critical mass reaches a point at which the chain reaction becomes self-sustaining, this is a condition known as criticality. The minimum mass needed for the chain reaction to occur is called the critical mass. In addition, the uranium sample must be massive enough so a typical neutron is more likely to induce fission than it is to escape. To produce a controlled, sustainable chain reaction, the percentage of U-235 must be increased to about \(50\%\). (These discoveries were taking place in the years just prior to the Second World War and many of the European physicists involved in these discoveries came from countries that were being overrun.) Natural uranium contains \(99.3\%\) U-238 and only \(0.7\%\) U-235, and does not produce a chain reaction. The possibility of a chain reaction in uranium, with its extremely large energy release, led nuclear scientists to conceive of making a bomb-an atomic bomb. Control energy production in a nuclear reactor. View a simulation on nuclear fission to start a chain reaction, or introduce nonradioactive isotopes to prevent one. The energy released in this process can be used to produce electricity. \): In a U-235 fission chain reaction, the fission of the m nucleus produces high-energy neutrons that go on to split more nuclei.
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