Reassessing Transuranic Element Contamination Within the 30 km Exclusion Zone of the Chernobyl Nuclear Power Plant
Abstract
Following the Chernobyl catastrophe in 1986, large amounts of radionuclides were dispersed into the environment and spread across a large territory. An evacuated 30 km exclusion zone was established around the site to limit access to the most heavily contaminated areas. The highest concentrations of radionuclide deposition, particularly for the transuranic elements such as americium, plutonium and the minor actinides, are located on the territories adjacent to the Chernobyl nuclear power plant. Assessing the distribution and movement of radionuclides in these areas remains a high priority, but many previous studies were carried out without appropriately accounting for specific characteristics of Chernobyl fallout, namely, the significant role of hot particles (fuel particles). Evaluation of the distribution and impact of Chernobyl contamination often relied on piecing together data on different radionuclides provided by different organizations. The compositional and spatial heterogeneity of Chernobyl fallout make it difficult to evaluate the accuracy of such disparate data sets. The Institute of Nuclear Research, Kiev (INR) has been involved in the tracking and study of contamination in areas impacted by the Chernobyl accident since the first days of the catastrophe. INR has developed comprehensive evaluation methods to support detailed assessment of the distribution and levels of contamination for transuranic elements across the 30 km exclusion zone. This approach to carrying out investigations ensures collection of representative data at all stages. Assessments now include a transuranic focus, taking into account over 3500 variables, and incorporating specific features of the Chernobyl fallout and geography. The basic principles developed for data collection include several modifications: Evaluation of existing survey data (such as airborne gamma surveys) and the spatial heterogeneity to target selection of sampling locations; Measurements of the concentrations of all radionuclides are now performed from the same sample aliquots; Multiple-factor geo-statistical data analysis of the spatial distribution of radionuclide concentrations as well as relative isotope ratios are used for evaluations. Features that can now be better assessed inside the 30 km exclusion zone include the extremely non-uniform distribution of contamination, complex radionuclide compositions, the physical-chemical properties of radioactive fallout, the diversity of meteorological conditions during the active stages of the accident, and the landscape characteristics of the territory along the main traces of the release. Using these new techniques, the spatial characteristics of radionuclides concentration for the different types of releases have been studied, and detailed maps of the contamination by plutonium (238Pu, 239+240Pu) and americium (241Am) have been created. The concentrations of contamination within the Chernobyl nuclear power plant exclusion zone by 239+240Pu and 241Am depend on direction and distance from the plant, but vary considerably from 0.1 kBq/m2 to more than 500 kBq/m2.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2011
- Bibcode:
- 2011AGUFM.V23C2588T
- Keywords:
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- 1000 GEOCHEMISTRY