Protection of the population from radioactivity in the event of a nuclear accident

In the event of an accident at a nuclear power station, protective measures are intended to limit the radiation exposure (dose) of the population to such an extent that only a very low additional cancer risk arises. The competent Federal Länder (federal states) authorities for disaster control need reliable information quickly in order to be able to decide which measures are the most appropriate:

• What are the anticipated exposure levels of the population?
• How much exposure has already occurred?

Before radioactivity is released

By means of the technical details of a power plant accident, the Gesellschaft für Reaktorsicherheit (Association for Plant and Reactor Safety, GRS) can estimate whether or not, which and how many radioactive substances will be released from the power plant. With the data of the GRS and the current weather forecast, the BfS is able to calculate

• which areas will be affected by the radioactive cloud,
• at approximately what time the cloud will reach an area,
• which radioactive substances the cloud contains,
• how much direct exposure will be received by the population in the affected areas if no protective measures are taken,
• how high the contamination of agricultural products not yet harvested will be.

Using this information, the Federal Länder are able to decide whether or not and which protective measures to take - for example evacuation, staying indoors or prohibiting the consumption of certain foods.

During the passage of the radioactive cloud

The quality of the advance calculations can be evaluated quickly by reading off the 1,700 measuring probes of the BfS. They measure radioactivity in the environment around the clock. If a cloud spreads differently than expected, this is shown by the measurements in real time. The BfS can correct its prognoses on this basis - and the Federal Länder can review their protective measures and change them if necessary.