Measurement exercise 2012 in Schleswig-Holstein and Lower Saxony

Helicopter of the German Federal Police Aviation Squadron (Bundespolizei Flugstaffel) Fuhlendorf Lower Saxony used during the measurement exercise.

The Federal Office for Radiation Protection (Bundesamt für Strahlenschutz, BfS) and the German Federal Police (Bundespolizei, BPOL) carried out a measurement exercise in Schleswig-Holstein and Lower Saxony from 24 to 27 September 2012.

This included measurements of environmental radioactivity in the vicinity of the nuclear installations

• Brunsbüttel
• Brokdorf
• Krümmel, and
• Stade.

In the run up to the exercise, the BfS preselected the investigation areas in coordination with the states (Bundesländer) involved.

The measurement exercise involved overflying these areas along given paths at an altitude of about 100 metres, using two helicopter-borne gamma spectrometry systems.

Map of investigation areas of the measurement exercise 2012

Comprehensive evaluation of all results obtained during the measurement exercise

The assessed ambient dose rates (ODL) map the geological conditions in the vicinity of the nuclear installations.

A localised radiological deviation which is not displayed on the maps was detected when overflying an industrial facility where a leak test was performed at the time of the measurement exercise, with a test device including a low-energy gamma source. Such test devices are commonly used in industry. However, only skilled personnel is allowed to use them in order to avoid putting staff and residents at risk.

Measurement results for each power plant site

After completion of the measurement flights, the ambient dose rate (ODL) was calculated based on the total count rates measured by sodium iodide detectors in the energy range of 250 to 3,000 kiloelectronvolts. Results were provided on radiological maps.

Considering the individual measurement uncertainties, the values obtained by the helicopter-borne ODL measurements are comparable with those detected by the ODL ground probes installed in the area under study. They provide a consistent image of the spatial distribution of the ambient dose rate.

The exercise also showed that helicopter-borne aero-gamma spectrometry is particularly suited for emergency preparedness since it is ready for use at a moment’s notice due to its short lead-time.

Comparative measurements over the red mud landfill near Stade

At the beginning of the exercise, measurement flights were conducted over a red mud landfill near the city of Stade in order to match the data obtained using the two measurement systems.

The specific activities of the natural radionuclides from the thorium-232 and uranium-238 series occurring in this are known from previous laboratory analyses:

Ambient dose rates determined by helicopter-borne measurements in the vicinity of the red mud landfill near Stade

The specific thorium and uranium concentrations in red mud are up to ten times higher than the activities measured in the vicinity. The red mud landfill near Stade is therefore well suited for comparison with the measured levels.

Evaluation of the measurement spectrums of the two measuring systems shows that the specific activities determined for the identified radionuclides and for the ambient dose rate match.

The ambient dose rate levels are in the range of 20 to 200 nanosieverts per hour and are comparable with the ambient dose rate levels measured on the ground.