Onderzoek naar radioactiviteit in luchtstof te De Bilt. Resultaten over 1990

Abstract

In 1990 airborne particles were daily sampled, using a sampling-period of 24 hours. After decay of the short-lived daughters of radon and thoron, gross-alpha, gross-beta and gross-gamma activities were measured. The yearly average of gross-alpha activity was 0.02 +- 0.01 mBq/m3, of gross-beta activity 0.16 +- 0.01 mBq/m3, and of gross-gamma activity 0.19 +- 0.06 mBq/m3. These mean levels are quite similar to those of 1987, 1988 and 1989. Applying gamma-spectroscopy no artificial radionuclides could be detected in airborne particles. Only the natural activationproduct Be-7 was detectable. The yearly average was 0.9 +- 0.1 mBq/m3 and the contribution to the gross-gamma activity was estimated at approximately 0.09 mBq/m3. The major contributions to gross-alpha and gross-beta activity in airborne particles are tentatively attributed to natural Po-210 and Pb-210/ Bi-210, respectively.