CHARACTERIZATION OF THE MIXED NEUTRON-GAMMA FIELDS INSIDE THE SWISS NUCLEAR-POWER-PLANTS BY DIFFERENT ACTIVE SYSTEMS

Measurements have been made with different active dosimetric systems i n four Swiss nuclear power plants (2 BWR and 2 PWR) to characterise th e mixed n-gamma fields. They were performed in 22 positions covering a wide variety of situations inside the containments, in a fuel storage facility and around spent fuel transport flasks. The spectrometric an d dosimetric results are presented, discussed and compared. A classifi cation of the neutron spectra in four categories according to their ha rdness is proposed. The spectra inside the containments are rather sof t; they are much harder in the fuel storage facilities and around spen t fuel transport flasks. Neutron dose equivalent rates in free access areas are low compared to those due to gammas, whereas in some limited access areas the neutron contribution to the dose equivalent may be a ppreciable.