The universal mass unit, abbreviated u (sometimes amu for atomic mass unit), is defined as one-twelfth of the mass of the 12C atom which has been defined to be exactly 12 u. The absolute mass of a 12C atom is obtained by dividing the value 12 by the Avogadro number (NA = 6.022 137...
It was the first fissile Uranium isotope to be discovered. When one neutron from the U-235 fission reaction causes another nucleus of this metal to undergo fission, it causes the entire chain reaction to continue. This condition is called the “critical condition” while the mass of U-235 re...
An atom may be conveniently symbolized by its chemical symbol with the atomic number and mass number written as subscript and superscript, respectively. For example, the symbol for uranium is U (atomic number 92); the isotopes of uranium with atomic weights 235 and 238 are indicated by 23592U...
1.a bomb whose potency is derived from nuclear fission of atoms of fissionable material with the consequent conversion of part of their mass into energy. 2.a bomb whose explosive force comes from a chain reaction based on nuclear fission in U-235 or plutonium. ...
Practical fissionable nuclei for atomic bombs are the isotopes uranium-235 and plutonium-239, which are capable of undergoing chain reaction. If the mass of the fissionable material exceeds the critical mass (a few pounds), the chain reaction multiplies rapidly into an uncontrollable release of ...
a bomb whose potency is derived from nuclear fission of atoms of fissionable material with the consequent conversion of part of their mass into energy. a bomb whose explosive force comes from a chain reaction based on nuclear fission in U-235 or plutonium.Compare...
The mass number is commonly cited in distinguishing among the isotopes of an element, all of which have the same atomic number (number of protons) and are represented by the same literal symbol; for example, the two best known isotopes of uranium (those with mass numbers 235 and 238) are...
235 to reachcritical mass, thus triggering a chain reaction and explosion. Engineers were confident that this comparatively simple design would work, but a sufficient quantity of uranium-235 would not be available until about August 1, 1945. The Hanford site would be able to deliver enough ...
235, say 0.45 kg (1 pound), cannot undergo a chain reaction and is thus termed asubcritical mass; this is because, on average, the neutrons released by a fission are likely to leave the assembly without striking another nucleus and causing it to fission. If more uranium-235 is added to...
235from naturaluraniumand to determine the critical mass of uranium required to make such a bomb. In August 1942 the U.S. Army was given the responsibility of organizing the efforts of British and U.S. physicists to seek a way to harnessnuclear energyfor military purposes, an effort that ...