Natural neutron flux and the dose equivalent in localities at different altitudes

Results are presented of the measurement of neutron fields in ground air in Czechoslovak localities (48deg to 52deg N, 16deg to 20deg E) at altitudes of 113 to 2632 m, performed by using a high-sensitivity 3He counter and a Bonner spectrometer. The total neutron flux Φtot and the dose equivalent rate H from natural neutron background were found proportional to exp(a.h) where h is altitude and a is a constant, a=(0.86±0.03)x10-3 m-1. The proportionality constants obtained by extrapolation to zero altitude are (76±20) m-2.s-1 for Φtot and 0.045x10-3 Sv/year for H. The total neutron flux is only slightly dependent on the composition of the dry ground; the natural neutron spectral patterns were found markedly dependent on the ground humidity. (author). 5 figs., 2 tabs., 12 refs