Induced radioactivity

Induced radioactivity is when a previously stable material has been made radioactive by exposure to specific radiation. Most radioactivity does not induce other material to become radioactive.

Neutron activation is the main form of induced radioactivity, which happens when free neutrons are captured by nuclei. This new heavier isotope can be stable or unstable (radioactive) depending on the element involved. Because free neutrons disintegrate within minutes outside of an atomic nucleus, neutron radiation can be obtained only from nuclear disintegrations, nuclear reactions, and high-energy reactions (such as in cosmic radiation showers or accelerator collisions). Neutrons that have been slowed down through a neutron moderator (thermal neutrons) are more likely to be captured by nuclei than fast neutrons.

A less common form involves removing a neutron with the photoneutron effect. This is where a high energy photon (gamma ray) strikes a nucleus with an energy greater than the binding energy of the atom, releasing a neutron. This starts at energies at 2 MeV (for hydrogen) and most radionuclides do not produce gamma rays that powerful.The isotopes used in food irradiation (Cobalt-60, Caesium-137) both have peaks below this. Caesium-137 at 662 keV and Cobalt-60's two peaks are 1.2 and 1.3 MeV.

Some induced radioactivity is produced by background radiation, which is mostly natural. However, since natural radiation is not very intense in most places on Earth, the amount of induced radioactivity in a single location is usually very small.

The conditions inside certain types of nuclear reactors with high neutron flux can cause induced radioactivity. The components in those reactors may become highly radioactive from the radiation they are exposed to. Induced radioactivity increases the amount of nuclear waste that must eventually be disposed, but it is not referred to as radioactive contamination unless it is uncontrolled.

See also

* Neutron activation
* Radioactive decay
* Radioactivity
* Slow neutron

External links

* [ - Ask the Experts "Gamma ray food irradiation"]

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Look at other dictionaries:

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  • induced radioactivity — sukeltasis radioaktyvumas statusas T sritis Standartizacija ir metrologija apibrėžtis Branduolinių reakcijų sukeltas medžiagų radioaktyvumas. atitikmenys: angl. induced radioactivity vok. induzierte Radioaktivität, f rus. наведенная… …   Penkiakalbis aiškinamasis metrologijos terminų žodynas

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  • induced radioactivity — /ɪnˌdjust ˌreɪdioʊækˈtɪvəti/ (say in.dyoohst .raydeeohak tivuhtee) noun radioactivity which has been induced in stable elements by bombarding them with high energy particles (e.g. neutrons). Also, artificial radioactivity …   Australian English dictionary

  • induced radioactivity — Physics. See artificial radioactivity. [1895 1900] * * * …   Universalium

  • radioactivity — /ray dee oh ak tiv i tee/, n. Physics, Chem. the phenomenon, exhibited by and being a property of certain elements, of spontaneously emitting radiation resulting from changes in the nuclei of atoms of the element. Also called activity. [1895… …   Universalium

  • radioactivity — The property of some atomic nuclei of spontaneously emitting gamma rays or subatomic particles (α and β rays) by the process of nuclear disintegration and measured in disintegrations per second (dps). One dps is equal to 1 becquerel, and 3.7 ×… …   Medical dictionary

  • induced radiation — Radiation produced as a result of exposure to radioactive materials, particularly the capture of neutrons. See also contamination; initial radiation; residual radiation; residual radioactivity …   Military dictionary

  • artificial radioactivity — induced radioactivity radioactivity produced by bombarding an element with high velocity particles, as the radioactivity of synthetic nuclides …   Medical dictionary

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