Nuclear reactions radioisotopic dating

Radiocarbon dating (43) has probably gained the widest general recognition (see Radioisotopes). Developed in the late 1940s, it depends on the formation of the radioactive isotope and its decay, with a half-life of 5730 yr. After forms in the upper stratosphere through nuclear reactions of... 

The most important isotope of plutonium is Pu = 24,200 years). It has a short half-life so only ultra traces of plutonium occur naturally in uranium ores, and most plutonium is artificial, being an abundant byproduct of uranium fission in nuclear power reactors. The nuclear reactions involved include the radiative capture of a thermal neutron by uranium, U( , y) U the uranium-239 produced is a beta-emitter that yields the radionuclide Np, also a beta-emitter that yields Pu. To date, 15 isotopes of plutonium are known, taking into account nuclear isomers. The plutonium isotope Pu is an alpha-emitter with a half-life of 87 years. Therefore, it is well suited for electrical power generation for devices that must function without direct maintenance for time scales approximating a human lifetime. It is therefore used in radioisotope thermoelectric generators such as those powering the Galileo and Cassini space probes. 

SECTIONS 21.4 AND 21.5 The SI unit for the activity of a radioactive source is the becquerel (Bq), defined as one nuclear disintegration per second. A related unit, the curie (Ci), corresponds to 3.7 X 10 disintegrations per second. Nuclear decay is a first-order process. The decay rate (activity) is therefore proportional to the number of radioactive nuclei. The half-life of a radionuclide, which is a constant, is the time needed for one-half of the nuclei to decay. Some radioisotopes can be used to date objects C, for example, is used to date organic objects. Geiger counters and scintillation counters count the emissions from radioactive samples. The ease of detection of radioisotopes also permits their use as radiolracers to follow elements through reactions. 

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