European research into the measurement of external environmental radiation doses

In a Commission of the European Communities (CEC) research programme spanning the past 10 years all aspects of external environmental radiation dose measurements have been thoroughly investigated. The aim of this work was to harmonize environmental radiation dose measurements within different countries. The initial studies involved research into practical calibration techniques and this led to the establishment of two unique calibration facilities. One facility developed by the Physikalisch Technische Bundesanstalt (PTB), Braunschweig, Germany in the Asse salt mine at a depth of 970 m where there is an extremely low level of environmental radiation. The other calibration facility is the Risoe National Terrestrial Radiation Measurement Station where reference measurements of a well determined natural environmental photon spectrum can be made. At Risoe a cosmic measurement station has also been established at a wooden pier extending into the Roskilde Fjord, this station is used for the determination of a detector's response to cosmic radiation. This paper describes the calibration techniques that have been investigated and the intercomparisons that have been performed. The relevance of this research programme was demonstrated by an intercomparison of external photon dose rate measurements by several detectors in the vicinity of a nuclear power station. (author)