Gamma radiation

Bundesamt für Strahlenschutz (BfS)

Protecting the population from radioactive radiation is an important part of the government's precautionary and protection system. To fulfil this task the BfS runs the comprehensive Integrated Measurement and Information System on environmental radioactivity (IMIS).

It is the task of IMIS to monitor environmental radioactivity on an ongoing basis and, in the event of an accident, to record the radioactive contamination of the environment quickly and evaluate the anticipated radiation exposure. All measured results are recorded, evaluated and displayed in the IMIS. The results are published and technically evaluated in the annual report "Environmental Radioactivity and Radiation" of the Federal Ministry for the Environment, Nature Conservation and Nuclear Safety (BMU). If there is an accident, the measured results form a basis for decision-making in the interests of people's health and protection of the environment.

An important measuring facility of the German Federal Office for Radiation Protection is the nationwide measurement network for measuring external radiation exposure (Gamma Dose Rate, GDR).

The measurement network currently consists of 2,150 fixed measuring points, which are distributed over all of Germany in a lattice of 15 x 15 km.

In routine operation the measurement network measures the natural radiation to which people are constantly exposed. It is made up of the radiation from the natural radioactive materials occurring in the ground (radionuclides) such as uranium, thorium or potassium (K-40) (terrestrial radiation) as well as radiation originating in space and of which a portion reaches the surface of the Earth (cosmic radiation).

The gamma dose rate (GDR) is quoted in the unit nanosievert per hour (nSv/h). The natural GDR in Germany ranges – depending on local circumstances – between 50 and 170 nSv/h. The external radiation exposure at one place is largely constant. Smaller, brief increases occur, when radioactive secondary products of the naturally occurring radioactive inert gas radon are washed out by precipitation and deposited on the ground. Terrestrial radiation is reduced by snow cover.

As a result of the reactor accident in Chernobyl in 1986 radioactive materials were distributed throughout Europe and also deposited on the ground in Germany, of which radioactive caesium (Cs-137) still exists today to a clearly measurable extent. Nevertheless, radiation from this source only makes a small contribution to the measured gamma dose rate in the air.

The results of current measurements and the pattern of radiation exposure at all measuring stations in the past 90 days can be accessed on the Internet under

The GDR measurement network is important for the emergency contingency plan. If the level of radioactivity exceeds a specific threshold value, this triggers an alarm automatically. If there should be an accident-related increase in the GDR, the sensors can be called up at 10-min intervals. This means that the spread of a radioactive cloud of toxic materials can practically be followed "live" online, so that the affected areas can be determined very quickly. This is an important requirement for quickly introducing specific measures to protect the population.

To be prepared for all eventualities the system facilitates measurements of the dose rate in a wide range from 50 nSv/h to 5 Sv/h.


The gamma dose rate on FINO1 can be accessed from the GDR database of the German Federal Office for Radiation Protection on the following website:

To the measurement data on gamma radiation

View the measurement data on the website of the German Federal Office for Radiation Protection.