Neutron spectra at flight altitudes and their radiological estimation.

Since the publication of the ICRP-report 60, air crews and other frequently flying persons are considered as occupationally exposed people. At civil flight levels neutrons contribute the major part to the radiologically relevant dose to men. The quantification of the neutron dose, and herewith the radiation risk due to neutrons, suffers from spectral data available especially in the energy range above 20 MeV. Experimental data were recently obtained at a low flight level on top of the mountain Zugspitze at 3000m using a modified Bonner sphere spectrometer. The resulting spectra are compared with Monte-Carlo transport calculations from top of the atmosphere down to 700 g/cm2. These data and others from the literature are used to calculate operational and risk related quantities, i.e. ambient dose equivalent and effective dose.