Argon production from radioactive decay

Argon-40 [7440-37-1] is created by the decay of potassium-40. The various isotopes of radon, all having short half-Hves, are formed by the radioactive decay of radium, actinium, and thorium. Krypton and xenon are products of uranium and plutonium fission, and appreciable quantities of both are evolved during the reprocessing of spent fuel elements from nuclear reactors (qv) (see Radioactive tracers). 

Helium is the second most abundant element in the universe. In the Earth, it is continuously formed by radioactive decay, mostly of uranium and thorium. Its present concentration in the atmosphere is probably the equilibrium concentration between the amount being released from the Earth s crust and the amount of hehum escaping from the atmosphere into space. The atmosphere represents the major source for neon, argon, krypton, and xenon. They are produced as by-products during flactional distillation of liquid air. Radon is obtained from the radioactive decay of radium. 

Radioactive elements in rocks (see Section 2.8), most importantly potassium (K) and heavy elements such as radium (Ra), uranium (U) and thorium (Th), can release gases. Argon (Ar) arises from potassium decay and radon (Rn, a radioactive gas that has a half-life of 3.8 days) from radium decay. The uranium-thorium decay series results in the production of a particles, which are helium nuclei. Once these nuclei capture electrons, helium has effectively been added to the atmosphere. 

Under this constraint, it is not possible to produce new superheavy nuclides at greater neutron excess by cold fusion, or by hot fusion with heavy-ion beams with lower atomic numbers than argon. This is because of the neutron richness of the overshoot isotopes, daughters of the multiple emission of relatively proton-rich a particles in the decays of the " Ca-induced evaporation residues. Nevertheless, both reaction types offer advantages in the production rates of the known isotopes of superheavy elements with Z = 106-108 that are of interest to the radiochemist. As examples Direct production of the long-lived hassium isotope Hs is possible in the cold-fusion irradiation of ° Pb with radioactive Fe. From Fig. 2, the cross... 

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