The ODL measuring network

The ODL measuring network

Everyone is subject to external radiation exposure caused by natural radioactivity at all times. This is due to natural radioactive substances (radionuclides) such as uranium, thorium and potassium (K-40) contained everywhere in the soil, in building materials and to radiation from sun and space.

What do we measure?

The BfS ODL measuring network routinely measures the natural radiation exposure. The measured local dose rate or ambient dose rate (Ortsdosisleistung, ODL) is expressed in microsievert per hour (μSv/h). This value describes the gamma radiation from the ambient air received per hour at a specified location.

The natural ambient dose rate in Germany is roughly between 0.05 and 0.18 microsievert per hour, depending on local conditions. This external radiation exposure remains largely constant. Small and short-term increases occur where radioactive decay products of radon, a natural radioactive gas, are washed out of the atmosphere by precipitation and are deposited on the ground. A reduction of natural radiation is also possible, e.g. when the ground is covered by snow.

Why do we measure?

The ODL measuring network is an essential element of emergency preparedness. If the level of radioactivity measured at a measuring station exceeds a certain threshold value, a notification is automatically triggered.

The BfS on-call service team processes and analyses such notifications without delay 24 hours a day, 365 days a year. The BfS team will check to see if there is a natural cause of the ambient dose rate increase or if it is e.g. caused by an accident.

Segment of the map with the control panels mentioned in the text

Where do we measure?

The ODL measuring network comprises 1,700 stationary, self-controlled measuring stations which are spread all over Germany in a basic grid of roughly 20 x 20 kilometers.

Nuclear installations are surrounded by a much denser grid up to a distance of 100 kilometers from the installations.

Locations of ODL measuring stations

In order to ensure standardised comparability of the measured ambient dose rate values, the measuring probes are positioned at a rather flat and unoccupied area. The majority of ODL probes in the BfS monitoring network are located on properties owned by the public sector (municipalities, counties, states, federal government).

The BfS does not only have stationary measuring systems. In an radiological emergency, mobile measuring systems can supplement the stationary ambient dose rate measurements in order to also detect even small-scale distributions.

Nuclear emergency preparedness

The ODL measuring network is a key early warning system to rapidly detect increased levels of radiation caused by radioactive substances in the air in Germany. In the event of a radioactive cloud it would be possible to follow its dispersion almost in real time. This is an essential prerequisite for initiating targeted measures to protect the population within a very short delay.

The data from the ODL monitoring network can also help to determine the dose that people have received during a radiological emergency.

The importance of an ODL measuring network became clear at the occasion of the Fukushima reactor accident. For Japan the ambient dose rate measurements (which were performed both in the early phase of the release and in the following days) were an important source of information so that they were able to estimate the progression and the impact on man and the environment. Since Germany is at a large distance from Japan and the concentration of radioactive substances was very low, the ODL measuring network did not register any increase. These minute traces of radioactivity could only be detected with the help of special measuring equipment for trace analysis at the BfS Schauinsland monitoring station.