Image: Sketch of the whole body detector (supervision).

This field also covers measurements of the release of materials from controlled zones, and the monitoring of discharges of radioactive substances into the surrounding area. These were the most important results in 2009:

• The areas around the Mühleberg and Gösgen nuclear power plants were measured by means of aeroradiometry. Except on the operating sites of the nuclear plants, no increased measurement values were recorded. The statutory limits were respected on the operating sites.
• PSI representatives took part in the revision of the international radiation protection standards ISO 7503 (Evaluation of Surface Contamination) and ISO 2889 (Sampling Airborne Radioactive Materials from Stacks and Ducts of Nuclear Facilities).
• In order to validate the Monte Carlo calibration of the PSI whole body counter, the detector geometry was determined and the virtual detector model was created. Measurements were then carried out in the whole body counter with simple geometries, and the detector model was verified and adapted. However, first measurements with complex geometries have not yet displayed the desired accuracy.
• The use of material CR-39 as a detector in personal neutron dosimetry was examined. Neutrons impacting the detector material leave traces in it. These are rendered visible with the help of a chemical etching process, and are evaluated by means of computer-aided image analysis and digital microscopy. The PSI verified the reproducibility of the evaluation, the linearity in the dose range from 0.5 to 100 mSv and the influence of the “temperature” and “time” etching parameters on the results.
• It was possible to demonstrate that the new MADUK sensors (MADUK: automatic network for monitoring the dose rate in the neighbourhood of nuclear power plants) are extremely sensitive. They were even able to detect increases of about 20 nSv/h in the ambient dose rate due to the discharge of positron emitters on the West site of the PSI. This increase is negligible in terms of radiation protection.