Neutron exposure at civil flight levels

This paper gives a review on the current knowledge of neutron exposure to men at civil flight altitudes due to neutrons, and presents recent experimental and calculation data of the authors. The ICRP proposed in 1991 to consider air crews and other frequently flying persons as occupationally exposed people. As neutrons contribute the major part to the radiologically relevant dose at civil flight levels to men, special considerations are necessary with respect to the required basic data for the determination of the risk relevant radiation doses. The quantification of the dose, suffers from spectral data available especially in the energy range above 20 MeV. Experimental data were obtained at a low flight level on top of the mountain Zugspitze at 3000 m 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 the operational and risk related quantities, i.e. ambient dose equivalent, effective dose and effective dose equivalent. The question of the proper choice of the operational quantity ambient dose equivalent to estimate the risk related doses is elucidated.

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