| Tritium is a kind of radionucide. It comes from natural nuclear reactions and artificial nuclear reactions and exists widely in various environmental medium. Nuclear Power Plant can produce a certain amount of the tritium under normal operation conditions, which are first released into the atmosphere in gaseous form. The gaseous tritium involved in the nature of the water cycle through a variety of reactions. Finally Tritium enters human body through breathing, drinking, diet, skin, etc. and can cause radiation damage. In recent years, Organically Bound Tritium (OBT) in biological samples was concerned because of longer retention time and more harmful. In order to accurately calculate the effective dose, effective pretreatment for OBT must be adopt. The aim of the thesis is to design and evaluate the pretreatment device for biological samples, and survey tritium level in environmental sample using the designed pretreatment device.Based on the abundance of investigation, we design a set of pretreatment device for OBT in biological samples. In order to burn biological samples slowly and completely in a quartz tube, various approaches are adopted such as phased temperature control, spiral copper oxide, design of the gas inlet end. The quartz tube is washed out with nitric acid, anhydrous alcohol and hot moisture flush respectively after burning biological samples in order to minimize the cross contamination. Standard tritiated water and 3H-TdR were used to test the recovery of tritiated water and organically bond tritium respectively. The detection efficiency of tritium is 23.3%. Excellent recovery and good repeatability was obtained using the apparatus. The recovery of tritiated water and organically bond tritium is 95.3% and 95.4% respectively. There is no difference between them (t = 0.11 , P> 0.05). The average chemical recovery of the apparatus for tritium was 95.4%. The relative standard deviations of recovery are less than 5%. The tritium results of three samples are consistent with that of Radiation Environmental Monitoring Management Centre of Jiangsu Province. These shows that design and procedure are feasible. Biological samples in five villages within 10 km of Qinshan nuclear power plant were collected, and biological samples were also collected around Suzhou city, Shandong Haiyang nuclear power plant and Tianwan nuclear power plant. The samples were collected between October 2010 and January 2011. The tritiated water in biological samples was collected by vacuum silica gel treatment and distillation. The OBT in biological samples was collected by designed pretreated device. The air samples were distillated. The results show that three kinds of biological samples (cabbage, radish and pine needles) collected at the same village have the same level of TFWF or OBT. The longer the distance from Qinshan nuclear power plant along the main wind direction is , the less level of TFWF and OBT in the samples is. And the TFWF or OBT level in Qinshan biological samples was higher than that of samples collected in Suzhou city. The levels of TFWT of leafy vegetables, carrots, and pine needles in Suzhou are 1.77±0.26, 1.21±0.26, 1.50±0.17Bq/kg, and the levels of OBT in these three samples are 0.141±0.0083, 0.0776±0.0096, 0.501±0.072Bq/kg. The OBT levels found in the wheat samples collected around Tianwan nuclear power plant were less than that of samples of tea and seaweed, which are normal background level. The tritium content in biological samples and atmospheric samples at Haiyang are also within normal background level. |
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