Sievert

The sievert ( unit symbol: Sv, after the Swedish physicist Rolf Sievert and physicians ) is the unit of various weighted radiation doses. It is used to determine the radiation exposure of biological organisms and is used in the analysis of radiation risk. The Sievert is used as a unit for:

• Equivalent dose;
• Effective dose;
• Organ dose.

Since an equivalent dose of 1 Sv is a very large value, the commonly occurring values ​​using a intent for units (SI prefix) in millisievert (1 mSv = 0.001 Sv = 10-3 Sv) or micro Sievert (1 Sv = 0.000 001 Sv = 10-6 Sv) specified. In exceptional cases, the information in nanosievert be (1 nSv = 0.000 000 001 10-9 Sv = Sv) specified.

• 2.1 Gray
• 2.2 Rem ( traditional unit )
• 2.3 becquerels

Radiation exposure limits and

Germany

As compared to the assessment of a radiation risk can serve the natural radiation exposure in Germany, a mean value of 2.4 mSv per year is used as a basis for the dose equivalent. The following limits apply to Germany, in addition to natural radiation:

The maximum allowed annual dose for occupationally exposed persons is 20 mSv, but may not come together more than 400 mSv over a working life. For the general population, the maximum annual dose of 1 mSv (excluding natural radiation and medical measures). An unborn child may not receive higher radiation dose than 1 mSv up to his birth.

Japan

After the Fukushima nuclear disaster in Japan on 11 March 2011 it was decided there that for the school children in the Fukushima region one years load of up to 20 mSv is classified as harmless. 20 mSv corresponds to the dose of a whole-body computed tomography and under German law permitted maximum exposure for occupationally exposed persons per calendar year. For employees of Tepco nuclear power plant operated by the reasonable annual equivalent dose was increased from 100 mSv to 250 mSv after the incident.

Relation to other units

The different types of radiation have different kinetic energies and cross sections, which differ in their toxic effects. In order to better compare the different types of radiation absorbed dose in terms of harmful effects for organisms, it is multiplied by a weighting factor, the radiation weighting factor. Thus, the various biological effects of radiation types is ( relative biological effectiveness ) are considered. In Sievert specified doses are therefore comparable with each other without knowing the type of radiation.

Gray

The unit of absorbed dose, the gray ( Gy) corresponds, as the sievert unit of the joule ( J) per kilogram ( kg). Since the radiation weighting factor is a dimensionless number, the equivalent dose and the absorbed dose have the same dimension. However, to emphasize the difference between the dose quantities for practical use and because the numerical value of the dose size can change by the radiation weighting factor also be used for energy doses Gray, for weighted dose quantities Sievert.

Rem ( traditional unit )

Until 31 December 1985, the official unit of equivalent dose was the Rem (rem ). 1 rem = 0.01 Sv = 10 mSv.

Becquerel

Under certain conditions ( known radionuclide known type of recording of the radiator, etc.) is possible using the dose conversion factor, an approximate determination of the equivalent dose ( in sieverts ) from the activity of the recorded material ( in becquerels ).