| ObjectiveThe purpose of the study is to investigate the tritium activity level and the distribution of tritium in aquatic environment which is surrounding Haiyang nuclear power plant, to compare the concentration level of tritium in different water bodies and different hydrographic periods, and to estimate the accumulated-effective dose of the residents surrounding nuclear power plant, which provided the basis for the environmental monitoring and assessment in the future.Methods1. We chose 16 sample points within 30km surrounding Haiyang nuclear power plant. The samples included surface water,groundwater,drinking water and sea water. The methods of sample-collection were based on the People's Republic of China Environmental Protection Industry Standard( HJ/T21-1998).2. The collected samples were purified by atmospheric distillation to remove impurities. In order to improve the concentration of tritium in water samples, the distilled samples should be electrolyzed .3. The preparation of the tested samples, background samples and the standard samples was on the basis of referred to the recommended method of the national standards(GB12375-90), After distillation, 8ml of the sample was introduced into a 20ml scintillation vial,with 12ml of the liquid scintillation cocktail and was sealed from light for 12 hours. A calibrated solution of 3H, with a nominal activity concentration of (12.80±0.09)Bq·g-1, was used to determine the tritium detection efficiency.4. According to the samples count results that obtained from the instrument, we estimated the accumulated-effective dose of residents who lived surrounding the nuclear power plant.5. The paired t test was used to analysis the different tritium concentrations in waters between two different periods, P<0.05 was considered statistically significant.6. In the test, tritium was determined by ultra-low-level LSC in a TRI-CARB3170TR/SL. This spectrometer is specifically designed for determining very low activities. the counts per minute (cpm) of the blank was 2.1, the sample counting time was 1000min; the counting efficiency of samples was 29.2%; the volume of water sample was the 56.8×10-3 L, the detection limit (LD) of the instrument was 0.22Bq·L-1.ResultThe results showed that the average level of the tritium concentration of water samples was (0.62±0.16) Bq·L-1, the range of the tritium concentrations was from 0.27Bq·L-1 to 0.93Bq·L-1,the tritium concentrations of the water samples in wet season, dry season were (0.73±0.12)(,0.52±0.12)Bq·L-1,respectively. The difference of the tritium concentrations between two different periods that analyzed by the paired t test were statistically significant (P<0.05).Regardless of the wet period or the dry period, the tritium concentrations of surface water samples were relatively higher than that of others, they were (0.83±0.04) , (0.61±0.11) Bq·L-1. The orders of the average tritium concentration of various types water that from high to low were surface water, groundwater, drinking water, seawater in wet period, and surface water, drinking water, groundwater, seawater in dry period.The background tritium concentration was low in Haiyang nuclear power plant. The accumulated-effective doses of the infants, adults, children who lived surrounding nuclear power plant were 0.015, 0.008, 0.007μSv·a-1,respectively.Conclusion1 The activity concentration of tritium in the aquatic environment surrounding Haiyang nuclear power plant was at the lower level than that of others. The distributions of tritium concentration in the dry period and in the wet period were different.2 According to the limited value that was regulated by basic standards for protection against ionizing radiation and for the safety of radiation sources (GB 18871-2002) (1mSv), the accumulated-effective doses of the infants, adults, children who lived surrounding nuclear power plant were also at the low level, they were 0.015, 0.008, 0.007μSv·a-1,respectively.3 The result of this study provided the basis for radiation monitoring and evaluation of the environment surrounding the plant which would be run in the future. |
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