Measurement exercise 2011 in Baden-Württemberg

Helicopters used in the measurement exercise in Baden-Württemberg, location Bundeswehr site Bruchsal

On behalf of the state Baden-Württemberg, the Federal Office for Radiation Protection (Bundesamt für Strahlenschutz, BfS) and the Federal Police (Bundespolizei) carried out a joint exercise to detect and assess environmental radioactivity based on helicopter-borne measurements from 11 to 14 April 2011. This included radiological mapping of the sites of the nuclear facilities

• Neckarwestheim,
• Philippsburg and
• Obrigheim

as well as the Karlsruhe Institute of Technology (KIT), Campus Nord, on the initiative of, and in consultation with the Ministry of the Environment, Climate Protection and the Energy Sector (Ministerium für Umwelt, Klima und Energiewirtschaft) in Baden-Württemberg.

Survey of the areas examined in the 2011 measurement exercise

Conducting measurement flights

A particular challenge of this exercise was to map the areas using different flight strategies.

• In the immediate vicinity of the three nuclear power plants areas of 25 square kilometres each were overflown along parallel paths at an interval of 300 metres. At a greater distance from the power plants, the surrounding area up to a distance of 10 kilometres was overflown along spiral paths with increasing path distances. Mapping of these areas of 400 square kilometres each required a measuring time of about 6 hours per site on average.
• In contrast, solely parallel flight paths were used to map the premises of the Karlsruhe Institute of Technology, Campus Nord (Karlsruher Institut für Technologie).

All measurement flights were carried out at a flight altitude of about 100 metres.

Measurement results at single nuclear power plant sites

After completion of the measurement flights, the ambient dose rate (Gamma-Ortsdosisleistung, ODL) was calculated based on the total count rates measured using the sodium iodide detectors in the energy range of 250 to 3,000 kiloelectron volts. For this purpose the detected radioactive substances were assumed to be homogeneously distributed over the area of detection.

Measurement results for the premises of the Karlsruhe Institute of Technology

Ambient dose rates determined by helicopter-borne measurements in the vicinity of the nuclear plants in Philippsburg

The figure illustrates the total count rates measured by sodium iodide detectors on the premises of Karlsruhe Institute of Technology, Campus Nord, in the energy range from 250 to 3,000 kiloelectron volts at 100 meters altitude. As the measurements reveal, the activity is not evenly distributed over the area. The ambient dose rate on the ground, therefore, cannot be calculated in this measuring area, unlike the power plant sites.

The figure depicts total count rates strikingly increased for a spatially limited area above the Central Decontamination Department (Hauptabteilung Dekontaminationsbetriebe, HDB), compared to the rest of the premises of the Karlsruhe Institute of Technology. Predominantly these are due to the radionuclides cobalt-60 and caesium-137. These result from operational procedures approved under the Atomic Energy Act according to statements of the Ministry of the Environment, Climate Protection and the Energy Sector in Baden-Württemberg and the reprocessing plant Karlsruhe (Wiederaufarbeitungsanlage Karlsruhe, WAK). The increased total count rates measured in the vicinity around the HDB also are attributable to the direct and indirect radiation from the HDB complex, exclusively reflecting the radiological conditions at 100 metres altitude.

Within this conspicuous area, like on the entire premises of the Karlsruhe Institute for Technology continuous environmental monitoring is performed to monitor public radiation exposure near the ground. In this context, the WAK refers to the annual reports of the Karlsruhe Institute of Technology published on the internet, where compliance with the limits for radiation exposure of the public is documented.

Ambient dose rates determined by helicopter-borne measurements along the Neckar from Neckarwestheim to Mannheim

Measurement results along the River Neckar

In addition to the mapping of nuclear facilities, a measurement flight along the River Neckar was performed, starting at the nuclear power plant Neckarwestheim, past the nuclear power plant Obrigheim up to Mannheim to measure the gamma radiation emitted from the riverbanks.

The ambient dose rates determined are shown alongside. There is no radiological anomaly.