Tungsten-181 and Other Short Lived Fission Products in Ground Level Air in North Germany and North Norway

Abstract

SAMPLES of atmospheric dust have been collected for several years at 1.5 m above ground in Brunswick (52° 18′ N, 10° 28′ E) as part of an environmental radioactivity surveillance programme. Before analysis, each filter, made from ‘Microsorban’ (Delbag, Berlin) is ashed at 450° C. The content of fresh fission products in the samples is then measured in a 10 cm by 10 cm NaI(T1) well-type scintillation spectrometer. Later, the ashes of all filters exposed during half a month—containing dust from about 50,000 m³ of air—are combined and measured in a 45 cm³ well-type Ge(Li) detector with a multichannel analyser (ND 2200). The activity concentrations of various fission products and certain cosmogenic radionuclides are evaluated from the γ-spectra numerically. Since October 1970 a filter sample containing dust collected from about 300,000 m³ of air in Tromsö (Norway) is also analysed once a month. Within recent months fresh fission products were detected on three occasions.