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This prevents most of the core from participation in the chain reaction and reduces the bomb's yield. Plutonium consisting of more than about 90% 239 Pu is called weapons-grade plutonium; plutonium from spent nuclear fuel from commercial power reactors generally contains at least 20% 240 Pu and is called reactor-grade plutonium.
This is a list of radioactive nuclides (sometimes also called isotopes), ordered by half-life from shortest to longest, in seconds, minutes, hours, days and years. Current methods make it difficult to measure half-lives between approximately 10 −19 and 10 −10 seconds.
The main decay modes of isotopes with mass numbers lower than the most stable isotope, 244 Pu, are spontaneous fission and alpha emission, mostly forming uranium (92 protons) and neptunium (93 protons) isotopes as decay products (neglecting the wide range of daughter nuclei created by fission processes).
Plutonium-238 (238 Pu or Pu-238) is a radioactive isotope of plutonium that has a half-life of 87.7 years.. Plutonium-238 is a very powerful alpha emitter; as alpha particles are easily blocked, this makes the plutonium-238 isotope suitable for usage in radioisotope thermoelectric generators (RTGs) and radioisotope heater units.
Plutonium-242 (242 Pu or Pu-242) is the second longest-lived isotope of plutonium, with a half-life of 375,000 years. The half-life of 242 Pu is about 15 times that of 239 Pu; so it is one-fifteenth as radioactive, and not one of the larger contributors to nuclear waste radioactivity.
For example, the critical mass of uranium-238 is infinite, while the critical masses of uranium-233 and uranium-235 are finite. The critical mass for any isotope is influenced by any impurities and the physical shape of the material. The shape with minimal critical mass and the smallest physical dimensions is a sphere.
Watchdogs are raising new concerns about legacy contamination in Los Alamos, the birthplace of the atomic bomb and home to a renewed effort to manufacture key components for nuclear weapons. A ...
Radioactive nonprimordial, but naturally occurring on Earth. 61 347 Carbon-14 (and other isotopes generated by cosmic rays) and daughters of radioactive primordial elements, such as radium, polonium, etc. 41 of these have a half life of greater than one hour. Radioactive synthetic half-life ≥ 1.0 hour). Includes most useful radiotracers. 662 989