Calibration Of Radiation Protection Dosimeters With Gammas Having Energies Greater Than 1 Mev - Use Of Capture Gamma-Ray Beams

A facility generating capture gamma rays has been realized using the ISIS reactor of the Saclay research center; this facility is to be used to calibrate protection instruments at photon energies between 1 and 10 MeV. The characteristics of beams generated using titanium and nickel targets are presented. The fluence weighted mean energies of the two beams are respectively 5.14 and 6.26 MeV. The maximum dose rates in a water phanton at full reactor power are about 200 mGy/h. The responses of two types of individual dosemeter (thermoluminescent or multiple screen photographic dosemeters) are given as examples. The responses show that, in the case considered, a dosemeter that has been correctly calibrated with Co-60 gammas can underestimate doses due to a 5-6 MeV beam by a factor of 2 to 5 or can overestimate doses by as much as 50 % according to the filter placed in front of the detecting element.