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Plutonium is the element with the highest atomic number known to occur in nature. Trace quantities arise in natural uranium deposits when uranium-238 captures neutrons emitted by decay of other uranium-238 atoms.
This is a list of chemical elements and their atomic properties, ... Average atomic mass Electronegativity ... Plutonium: Pu [244] 1.28: 6.0262: 175 ...
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]
Plutonium (Pu, atomic number 94), first synthesized in 1940, is another such element. It is the element with the largest number of protons (atomic number) to occur in nature, but it does so in such tiny quantities that it is far more practical to synthesize it. Plutonium is known mainly for its use in atomic bombs and nuclear reactors. [4]
The plutonium-only core, with its high background neutron rate, had a high probability of predetonation, with reduced yield. [13] Minimizing this probability required a smaller mass of plutonium, which limited the achievable yield to about 10 kt, or using highly pure plutonium-239 with impractically low level of plutonium-240 contamination.
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 abundance of elements in Earth's crust is shown in tabulated form with the estimated crustal abundance for each chemical element shown as mg/kg, or parts per million (ppm) by mass (10,000 ppm = 1%).
Plutonium-240 (240 Pu or Pu-240) is an isotope of plutonium formed when plutonium-239 captures a neutron. The detection of its spontaneous fission led to its discovery in 1944 at Los Alamos and had important consequences for the Manhattan Project. [3] 240 Pu undergoes spontaneous fission as a secondary decay mode at a small but significant rate.