Detector parameters (A), flight paths (B), single spectra of NaI-detectors (C) and count rates in the total count window (D) represented during a measurement flight

In addition, the count rates in the total count window for a few measurement spectra obtained by measurements performed along a trajectory of sector 3 eastern from Cattenom were slightly higher than those of the natural background. These were due to small-area anomalies of the natural radionuclides from the thorium-232 decay chain, which are, however, insignificant with respect to radiation exposure of the public.

Ambient dose rates determined by helicopter-borne measurements in the vicinity of the Cattenon nuclear power plant, France

The ODL levels at the power plant sites are between 40 and 140 nanosieverts per hour (1 nanosievert is equivalent to one billionth of a Sievert). This is within the range of radiation levels typically occurring in Germany (natural background). Evaluation of the measurement spectra for each of the radionuclides shows that the ambient dose rate is due to the natural radionuclide potassium-40 and the natural radionuclides of the thorium-232 and uranium-238 decay series in all cases.

Artificial radionuclides were not detected in the area of the nuclear power plant sites.

Ambient dose rates determined by helicopter-borne measurements in the investigation area Ellweiler

The ambient dose rates determined in the investigation area Schallodenbach, like those in the vicinity of the Biblis and Cattenom nuclear power plants, were in the range of 40 to 150 nanosieverts per hour. However, ambient dose rates between 150 and 250 nanosieverts per hour were identified in small parts of the investigation areas Ellweiler and Schweissweiler. These partial areas had been addressed by the Landesamt für Geologie und Bergbau in Rhineland-Palatinate in the run up to the measurement exercise. Compared to their environment, these partial areas are characterised by enhanced activity concentrations of radionuclides from the uranium-238 decay chain in the soil, which are due to geology and therefore natural.

Ambient dose rates determined by helicopter-borne measurements in the investigation area Schweissweiler

The ambient dose rates determined in the investigation area Schallodenbach, like those in the vicinity of the Biblis and Cattenom nuclear power plants, were in the range of 40 to 150 nanosieverts per hour. However, ambient dose rates between 150 and 250 nanosieverts per hour were identified in small parts of the investigation areas Ellweiler and Schweissweiler. These partial areas had been addressed by the Landesamt für Geologie und Bergbau in Rhineland-Palatinate in the run up to the measurement exercise. Compared to their environment, these partial areas are characterised by enhanced activity concentrations of radionuclides from the uranium-238 decay chain in the soil, which are due to geology and therefore natural.

Specific activities assessed for radionuclides from the uranium-238 decay chain using the helicopter measurement system 1

The area of the former red mud landfill in the southeast of Ludwigshafen was selected to perform comparative measurements with the two helicopters used for the exercise. Since the landfill is already completely covered by soil layers, the values measured at this site are low and similar to those of the natural background. Slightly increased values were assessed northeast from the measurement area as well as in the total count window and in the uranium window. Since the activity concentrations at this site are clearly above the natural background, this partial surface was selected for the comparison of results.

Comparison of the measurement data obtained using the two measurement systems shows that the specific activities for the identified radionuclides and for the ambient dose rate are in very good agreement, within the scope of measurement uncertainties.

Specific activities assessed for radionuclides from the uranium-238 decay chain using the helicopter measurement system 2

The area of the former red mud landfill in the southeast of Ludwigshafen was selected to perform comparative measurements with the two helicopters used for the exercise. Since the landfill is already completely covered by soil layers, the values measured at this site are low and similar to those of the natural background. Slightly increased values were assessed northeast from the measurement area as well as in the total count window and in the uranium window. Since the activity concentrations at this site are clearly above the natural background, this partial surface was selected for the comparison of results.

Comparison of the measurement data obtained using the two measurement systems shows that the specific activities for the identified radionuclides and for the ambient dose rate are in very good agreement, within the scope of measurement uncertainties.