An approach to identifying the relative importance of different radionuclides in ecological radiological risk assessment: Application to nuclear power plant releases.

There is a need to prioritise the requirements for data to assess the radiological risk for fauna and flora, as inevitable large data gaps occur due to the large number of combinations of radionuclides and organisms for which doses need to be assessed. The potentially most important dose-forming radionuclide-pathways combinations need to be identified to optimize filling these gaps. Few attempts have been made to classify the importance of isotopes with regard to radiation protection of the environment. A hierarchical approach is described here for radionuclides that are potentially present in generic ecosystems (freshwater, marine or terrestrial) and is applied for scenarios considering ecologically relevant chronic exposure. In each ecosystem, the top ten radionuclides that may contribute to doses were identified using a qualitative Chronic Hazard Index. Including quantitative aspects by incorporating discharge quantities changed the priority list, and increased the relative importance of radionuclides contributing most to the authorized releases of nuclear facilities (14C and 3H followed by 60C). The potentially most important dose-contributing radionuclides in the framework of environmental radiation protection under a chronic exposure situation included isotopes of about 20 elements. The five most important in order of decreasing importance were: carbon, hydrogen, caesium, cobalt and americium. Consideration of acute exposure situations was hampered by data gaps that were even greater than that for chronic exposure situations, so it was only possible to consider the feasibility of developing a consistent approach.

An extended critical review of twenty years of countermeasures used in agriculture after the Chernobyl accident.

A wide range of different countermeasures has been used to mitigate the consequences of the Chernobyl accident for agriculture in affected regions in Belarus, Russia and Ukraine. The paper comprehensively brings together key data on countermeasure application over twenty years for all three countries and critically evaluates the response to the accident with respect to agriculture. The extents of countermeasures implementation in various periods following the ChNPP accident are documented. Examples of best practices and drawbacks in remediation of affected areas are identified. Data on the effectiveness of agricultural countermeasures have been evaluated and the impact of countermeasures implementation to mitigate consequences of the accident has been assessed for the period 1986-2006. Implementation of agricultural countermeasures averted 30-40% of the internal collective dose that would have been received by the residents of affected regions without the use of countermeasures. The current situation in agriculture of areas subjected to contamination following the Chernobyl accident is described. Current and future needs for remediation, including a consideration of various strategies of rehabilitation of affected areas are presented.

Assessment of current exposure of the population living in the Techa River basin from radioactive releases of the Mayak facility.

Current doses arising from external and internal pathways have been estimated for the residents of two villages, Muslumovo and Brodokalmak, alongside the Techa River, which was contaminated by radioactive releases from the Mayak production facility. The dose estimates are based on numerous environmental measurements supplemented by further human whole body measurements and studies on occupational and dietary habits of Slavic and Turkish ethnic groups. Estimated doses arise mainly from use of the contaminated floodplains alongside the Techa River. The current average annual effective dose attributable to Cs and Sr in the environment, under conditions where restrictions on some river-related activities are in place, may exceed the Russian national action level of 1 mSv only in the hypothetical critical group of herdsmen in Muslumovo. The dose to this critical group in Brodokalmak is assessed to be 3 times less than that in Muslumovo and 2 fold below the action level. The external and internal exposures give comparable contributions to the total dose in both settlements and population groups: 47% and 53% in Muslumovo and 40% and 60% in Brodokalmak, respectively. About one quarter to one half of the internal dose in adults arises from the intake of Sr. In order to avoid substantial increases in the dose received by Muslumovo residents, it is expedient to prolong the current policy of restriction of some river-related population activities in this village.

Predicting radionuclide transfer to wild animals: an application of a proposed environmental impact assessment framework to the Chernobyl exclusion zone.

A number of assessment frameworks have been proposed to provide a mechanism to demonstrate protection of the environment from ionising radiation. Whilst some of these are being used for assessment purposes they have largely not been validated against field measurements. In this paper we compare the predictions of transfer parameters recommended by one of these frameworks (FASSET) with observed whole-body 90Sr and radiocaesium activity concentrations in a range of mammal and invertebrate species sampled within the Chernobyl exclusion zone. Predicted activity concentrations were generally within the observed ranges and mean predictions for reference organisms were similar to, or circa one order of magnitude higher than, the observed means. However, some predictions were more than one order of magnitude lower than observed values. No data were available to test predictions for the other radionuclides released by the Chernobyl accident. In a separate paper the outputs of this assessment will be used to estimate doses to reference organisms and compare these to observed radiation induced effects reported within the Chernobyl zone.