Monitoring of radiation in the atmosphere and a food chain. Results in the Netherlands in 1992. Environmental report 1993

The results of biosphere sample measurements are presented. In 1992, the yearly average gross α and gross β activity concentration of airdust was 0.06±0.01 and 0.44±0.06 mBq·m-3, respectively. These values were significantly higher than those of previous years. The yearly total gross α and gross β-activity of the deposition in Bilthoven, Netherlands, was 44.2±0.4 and 87.3±0.8 Bq·m-2, respectively, and the deposition of 3H was 1440±50 Bq·m-2. The total activity of 137Cs in deposition was 0.69±0.16 Bq·m-2, of 210Po 11±1 Bq·m-2 and 210Pb 83±5 Bq·m-2. These activities are comparable to those of previous years. The yearly average concentrations of 137Cs and 90Sr in consumer milk from a nationwide sample mix was 0.13±0.02 and 0.03±0.01 Bq·L-1, respectively, which are about equal to that of the previous year. For the gross α-activity concentration, as measured by the aerosol monitors of the LMR, 5-percentile values in the range of 0.3-0.9 Bq·m-3 and 95-percentile values in the range of 4.3-11.1 Bq·m-3 were found, with an average value across the country of 2.4 Bq·m-3. This value was in between the values of 1990 and 1991. The γ-activity measured with the LMR monitors was in the same order of magnitude as the year before. For the dose-equivalent rate, 5-percentile values in the range of 56.1-88.4 nSv·h-l and 95-percentile values in the range of 63.8-95.8 nSv·h-l were found. The average value of 79.3 nSv·h-l was in good agreement with the 1991 average (78.9 nSv·h-l). The aerosol monitors of the LMR had an average availability of 88% in 1992, which is an improvement over the value of 76% in 1991. In 1992, just as in previous years, some structural monitor failures reduced the availability. The proportional counters were almost free of failures; the average monitor availability was 96%, which is also an improvement compared to the 92% of the year before. 17 figs., 9 tabs., 1 appendix, 27 refs