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 in four Swiss nuclear power plants (2 BWR and 2 PWR) to characterise the 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 and dosimetric results are presented, discussed and compared. A classification of the neutron spectra in four categories according to their hardness is proposed. The spectra inside the containments are rather soft; they are much harder in the fuel storage facilities and around spent 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 appreciable.