Radionuclide

As a radionuclide or radioactive nuclide is known a nuclide ( a type of atom ), if it is unstable and therefore radioactivity.

Notations, label

The formulaic designation is the same as for stable nuclides, eg for radionuclide cobalt -60:

A special term for " radioactive " is not provided, except in the ( rare ) Kernisomeren. This will get to distinguish it from its ground state a superscript m, eg or even.

The previously used term radioisotope instead of radionuclide should only be used when in addition to the radioactivity is also the affiliation to a particular item of importance. However, the term isotope is found still in place of nuclide or radionuclide specifically as part of many trade names such as "Isotope Laboratory ", " isotope method " or " Radioisotope Generator".

Decay

Each radionuclide has its characteristic properties, such as half- decay time, decay (s ), and decay energy. The decay occurs mostly alpha or beta radiation and / or gamma radiation. The " speed " of this decay is described by the half-life T ½: After a half-life half of all atoms initially present is not yet decayed after two half-lives of only a quarter etc.

Classifications

One hand, for radionuclides according to their decay ( alpha emitters, beta emitters, etc.) or classified according to the scale of its half-life. On the other hand, one can distinguish between natural and artificial radionuclides. However, all radionuclides are also produced artificially; Therefore, the occurrence of some naturally existing radionuclides is increased since the beginning of the nuclear age. Examples are carbon -14 ( 14C ) and the hydrogen isotope tritium ( 3H).

Natural radionuclides

Natural radionuclides are present in the biosphere or in the ground. They come in part from the reservoir of the nuclides formed in the stellar nucleosynthesis, in particular the heavy mineral radionuclides such as uranium - 235th These so-called primordial radionuclides shall have suitably long half-lives. Since the proportion of the nuclides formed during nucleosynthesis can be mathematically modeled and decay radionuclides among them according to their half-lives, can be inferred from their measured today shares on the age of the earth forming matter.

Another part of the natural radionuclides is continuously through the interaction of high -energy cosmic radiation ( cosmic radiation ) formed with the atmosphere. These radionuclides are called cosmogenic. The radioactive carbon isotope 14C ( half-life of about 5730 years ) is the best known representatives of this genus. See radiocarbon method.

The rest of the natural radionuclides formed by the turn radioactive decay products of the first kind. One calls these radionuclides radiogenic.

Artificial radionuclides

With artificial radionuclides are understood to be caused by human-induced nuclear reactions. Many artificial radionuclides not come due to their short half -lives in nature in appreciable quantities.

Production:

• By neutron irradiation in a nuclear reactor or other neutron sources, such as C-14, by the reaction of 14N ( n, p) 14 C
• P-32 from the reaction 35Cl (n, α ) 32P;

Many artificial radionuclides have short half-lives so that they are separated from their longer-lived parent nuclide in a nuclide until shortly before use. Here, the required radionuclides are eluted by suitable solvents or binders. A frequently used generator is the 99Mo - 99mTc generator.

• Potassium 40
• Rubidium 87
• Samarium 147
• Rhenium 187
• Bismuth 209
• Thorium 232
• Uranium 235, 238
• Plutonium 244

• Tritium ( isotope of hydrogen )
• Beryllium 7, 10
• Carbon-14
• Sodium 22
• Aluminum 26
• Phosphorus- 32, 33
• Silicon 32
• Sulfur 35
• Chlorine 36
• Argon 37 39
• Krypton 81, 85
• Iodine 129

• Radium 224, 226, 228
• Radon- 220, 222
• Thorium 230
• Uranium 234

• Tritium (also naturally occurring isotope of hydrogen )
• Technetium, all isotopes
• Plutonium-239 (alpha emitter, fissile, f nuclear weapons and nuclear fission reactors suitable )
• Plutonium-238 (alpha emitter, use in nuclear batteries )
• Strontium 90 ( fission product from nuclear reactors )
• Promethium, all isotopes ( fission products from nuclear reactors )

Application

Radionuclides are used in many fields of engineering and natural sciences as well as in medicine. When handling, make sure that observed and complied with all the necessary measures for the radiation protection (see Radiation Protection Ordinance ).

In chemistry (specifically Radiochemistry ) radionuclides are used for example as radiotracers. Here connections are labeled with radionuclides, that is, there are radionuclides incorporated into the compound ( Leitisotope ) to perform temporal or local changes (eg, quantity determinations). An advantage of this method is that the radiolabelled compounds experience the same chemical reactions as their equivalents of the non-radioactive, but far better to distinguish and locate (even at low concentrations).

Similarly, biology and medicine uses similar methods to make metabolic processes in a living organism and to examine ( autoradiography Radiochromatography ). In radiotherapy enclosed radionuclides are used, for example, 60Co ( " cobalt cannon "); see nuclear medicine. In addition, the radionuclide therapy offers a variety of treatment options. The adjacent table shows an example of a selection of some radionuclides and their half-lives that are applied, inter alia, also in radiation therapy of cancer. For in vivo studies, the half -lives should be as small as possible to minimize the potential for harm to the body.

In technology, radionuclides are used for example as a source of energy (see nuclear power plant, radionuclide ).

Hazard classes

The German Radiation Protection Ordinance divides radionuclides, depending on the hazard potential in four classes.