Environmental gamma-ray measurement methods for French nuclear installation impact studies

Due to the development of the nuclear industry and current concern for the environment, studies need to be carried out on the impact of new nuclear power plants. One of the elements of this impact is external irradiation, which should be measured before installations are put into operation. Four measurement devices are compared: a scintillometer using a composite crystal, which takes into account the photon ionization power as a function of the energy (SCINTOMAT 6134 BEFIC); a tissue equivalent ionization chamber with magnesium fluoride polyethylene walls (CET 72 SAPHYMO-SRAT); a big ionization chamber filled with air at atmospheric pressure (CD 43 ALCATEL); and a pressurized gas ionization chamber made of a 25.4-cm-diam sphere containing argon at a 25-atm pressure STP (RSS 111 Reuter Stokes). For purposes of environmental measurements, the most important criteria of comparison are sensivity, relative fluctuation, and velocity of response, so that low dose rates can be measured when the device is set up in a truck moving at low speed for regional mapping. The comparison shows that the pressurized gas ionization chamber comes the closest to meeting the required conditions