Photon calibration of radiation protection instruments in an authorized metrology service

In radiation protection it is necessary to have periodical calibration and verification of the radiation monitoring instruments and special dosimetric techniques for particular cases. To that end the Radiation Protection Service of the Grenoble Nuclear Research Centre has developed calibration facilities which comprise 241Am, 137Cs and 60Co radiation sources, a brief description of which is given. This laboratory has been accepted as an authorized metrology laboratory within the ionizing radiation calibration chain of the National Bureau of Metrology. After describing the transfer detector and the associated electronics, the authors explain the calibration procedure used - a procedure which is standardized within the radiation protection services of the Commissariat a l'energie atomique - and indicate what margins of accuracy are achieved in a calibration at this laboratory, which is on the quaternary level of the calibration chain. (author)