Intercomparison measurements of surface soil contamination with in-situ gamma ray spectrometry. Pt.2. Natural radionuclides

The intercomparison program was performed by the Federal Office of Radiation Protection in October 1993. 17 teams - 10 from Germany and 7 from other european countries - took part in the measurements. Three characteristic sites at the Ronneburg (Wismut Ltd.) Uranium Mine facility are investigated: Absetzerhalde, Parkplatz Drosen and Gessenhalde. The specific activity of the nuclides from U-Ra- and Th-series and of 40K was measured at 5 locations. Most of the participants reported data about all nuclides from these decay chains measured by gamma ray spectrometry. Basically, the measured data were in good agreement and, as expected, the radionuclides from Th-series agreed better than those from U-Ra-series. Some participants reported significantly higher values (compared to the total mean value) for 226Ra (up to 90%). For other nuclides the deviations from the total mean value are within the measurement's uncertainty. The following specific activities are obtained: 1) For Absetzerhalde site: 238U (226Ra) - 1900 Bq/kg (1600 Bq/kg); 232Th - 40 Bq/kg; 40K - 640 Bq/kg. 2) For Parkplatz Drosen site: 238U (226Ra) - 700 Bq/kg (600 Bq/kg); 232Th - 20 Bq/kg; 40K - 460 Bq/kg. 3) For Gessenhalde site: 238U (226Ra) - 1200 Bq/kg (1800 Bq/kg); 232Th - 30 Bq/kg; 40K - 430 Bq/kg. 10 tabs., 14 figs., 3 refs. (orig.)