Ensuring robust radiological risk assessment for wildlife: insights from the International Atomic Energy Agency EMRAS and MODARIA programmes.

In response to changing international recommendations and national requirements, a number of assessment approaches, and associated tools and models, have been developed over the last circa 20 years to assess radiological risk to wildlife. In this paper, we summarise international intercomparison exercises and scenario applications of available radiological assessment models for wildlife to aid future model users and those such as regulators who interpret assessments. Through our studies, we have assessed the fitness for purpose of various models and tools, identified the major sources of uncertainty and made recommendations on how the models and tools can best be applied to suit the purposes of an assessment. We conclude that the commonly used tiered or graded assessment tools are generally fit for purpose for conducting screening-level assessments of radiological impacts to wildlife. Radiological protection of the environment (or wildlife) is still a relatively new development within the overall system of radiation protection and environmental assessment approaches are continuing to develop. Given that some new/developing approaches differ considerably from the more established models/tools and there is an increasing international interest in developing approaches that support the effective regulation of multiple stressors (including radiation), we recommend the continuation of coordinated international programmes for model development, intercomparison and scenario testing.

Evaluation of Cs-137 and natural radionuclides on different marine biota (crustacean and fishes) along Beheira governorate Coast-Egypt: RESRAD biota.

PURPOSE: This work will focused on the environmental and radio-ecological impacts occurred on an Egyptian coastal region, based on the radiochemical measurement of 238U, 137Cs, 232Th, 40K. The novelty of the study was cleared by the using of new technique showing the integration of two biological RESRAD models, lead to a probabilistic estimation of the radionuclides bioaccumulation in different consumed marine organisms and determination the probability of human cancer risk at different ages. MATERIAL AND METHODS: The 20 water samples were collected and mounted into clean containers, and their decay products, were measured in Bq.L-1, using different quality assurance tools. The study will used different statistical analysis and different RESRAD modeling codes were used in the study to predict the degree of environmental and radio-ecological impacts at the studied area, this will be helpful in order to define the impacts resulted from the transferring and accumulation of different radionuclides. RESULTS: showed that the highest human dose conversion factor values of (5, 10, 15, with adult ages) were measured in Th-232 (mrem/pCi) while the lowest ingestion conversion factors values were observed in artificial 137Cs. On the other hand the highest values of external risk factor in case of (5, 10, 15 with adult age) were observed in artificial Cs-137(mrem/pCi), while the lowest value of external risk factor with the same ages were observed in U-238. This will lead to continual monitoring of artificial Cs-137 in different marine coastal regions. The arrangement of the bioaccumulation value (BIV) in Bq.kg-1 which being calculated by using RESRAD-Biota in case of crustacean animals will be as follow: U-238 > Th-232 > Cs-137, while the arrangement of BIV in case of fish animals will be: Cs-137 > U-232 > Th-232. On the other hand the arrangement of Internal Dose Conversion factors in case of crustacean animals will be: U-238 > Th-232 > Cs-137. While the arrangement of Internal Dose Conversion factors in case of fish animals will be: Cs-137> Th-232 > U-238. CONCLUSION: RESRAD code's results showed that the arrangement of the bioaccumulation and Dose Conversion factors were depend on the type of marine living organism. RESRAD code also showed that there are increments of the calculated external risk factor values which resulted from the adult than all the infants (5,10 and 15 ages) ages this may be related to the continuous replacement of new human's body cells during the growth stages. The study results showed that, environmental bioaccumulation impacts of the artificial Cs-137 were very effective in both marine living organisms and human as this will support the relation between the ingestion Cs-137 in the body(inside the soft tissues), and the probability of the human cancer risk. On the other hand, study results showed the importance of using RESRAD BIOA code for the EIA's ecological and radiological studies which should be done for any future industrial coastal .projects.

Bioaccumulation of natural radio-nuclides in aquatic, riparian and terrestrial animals along Suez-Azzafrana coastline, Egypt: insights from RESRAD-BIOTA.

PURPOSE: The protection of endogenous species is one of the important ecological issues in which all the World Environmental Agreements are searching for. The purpose of the study is to calculate the bioaccumulation impacts of some natural radio-nuclides as: Ra-226, K-40 and Th-232 in the selected Egyptian Endogenous Aquatic Red Sea Fusileer fish, Red sea Riparian Turtle and the Red sea Terrestrial Lizard by using RESAD BIOTA version 1.8. MATERIAL AND METHODS: Ten water and sediments samples were collected from different 10 sites, along the inshore of the Egyptian Suez bay beach till El-Zafarna coastal region, as these samples were taken from subsurface (20 cm-1 m). The radioactivity concentrations of some natural radioactivity radionuclides as; 226Ra, 232Th and 40K, which were measured, using gamma-ray spectrometer based on high-purity germanium (HPGe) detector of 40% relative efficiency. RESULTS: The results of the study showed that the radioactivity of some selected natural radionuclides in the selected 10 sites of Suez costal samples were arranged as: K-40 > Th-232 > Ra-226, as this was related to the characteristics of soil and rock precipitation in this zone besides the industrial activates along the selected coastal line zone of Suez bay till Al-Zafrana. On the other hand, it was observed that all the calculated Biota contamination Guide (BCG) values of the selected Egyptian endangerous species (Aquatic, Riparian and terrestrial) animals in the 10 selected sites samples were below the recommended (BCG), as the result, no radioactivity increment being detected at these selected sites. On the other hand, the BCG values of Ra-226 in both water and sediment samples for the selected Egyptian endangerous Aquatic Sea Fusileer Fish were higher than the recommended BCG values in water, while were comply with BGC values of the sediment, while in case of Egyptian endangerous Red Sea Turtle's BCG values were comply with the recommended BCGs in water while were higher than the recommended BCGs values of sediment. In case of the selected Egyptian endangerous terrestrial Lizard its BCG values of Ra-226 were higher than the recommended BCGs in both water and sediment media. While in case of Th-232 it was observed that the BCG values of selected endangerous Red Sea Fusileer Fish were higher than the recommended BCGs in both water and sediment and also the BCG values of selected endangerous Riparian Turtle were also higher than the recommended BCGs of both water and sediment, these results may increase the suitability of the selected Egyptian endangerous Marine, Riparian and Terrestrial species to the different radiological risks. The results showed also the decrement of the radioactivity values of the measured radionuclides in the internal tissue of the Egyptian selected endangerous Red Sea Lizard (Uromastyx aegyptia) than both the selected endangerous Red Sea Turtle and Red Sea Fish species, support the reptiles, which are cold blood animals, and is less affected by gamma radiation than other terrestrial animals.

Radiological risk assessment of natural radionuclides in the marine ecosystem of the northwest Mediterranean Sea.

PURPOSE: This study aimed to assess the radiological risk of natural radionuclides (226Ra, 232Th, and 40K) to marine ecosystem biota. MATERIALS AND METHODS: The study site in this was the Mediterranean Sea, Cyprus. With the use of the RESRAD-BIOTA (RESidual RADioactivity BIOTA) code, the tissue concentration, external and internal dose rate of aquatic animals and riparian animals were estimated. RESULTS: The total tissue concentrations of the aquatic animals and riparian animals were simulated at 1.14 × 106 Bq/kg (water media) to 0 Bq/kg (sediment media), and 1.33 × 106 Bq/kg (water media) to 9.79 × 101 Bq/kg (sediment media), respectively. The total dose rate for aquatic animals and riparian animals was ranged from 1.94 × 10-2 to 0 Gray per day (Gy/d) and 1.46 × 10-2 to 7.40 × 10-7 Gy/d, respectively. CONCLUSIONS: Based on the risk assessment of this study, there is no significant impact due to organisms' exposure to natural radioactivity. Although, further consideration of the exposure levels is required due to the potential effects of protracted low-level ionizing radiation.

Assessment of dose rate to terrestrial biota in the area around coal fired power plant applying ERICA tool and RESRAD BIOTA code.

This paper presents the environmental radiation risk assessment based on two software program approaches ERICA Tool (version 1.2) and RESRAD BIOTA (version 1.5) to estimate dose rates to terrestrial biota in the area around the largest coal fired power plant in Serbia. For dose rate assessment software's default reference animals and plants and the best estimated values of activity concentrations of 238U, 234U, 234Th, 232Th, 230Th, 226Ra, 210Pb, 210Po, 137Cs in soil were used. Both approaches revealed the highest contribution to the internal dose rate due to 226Ra and 210Po, while 137Cs contributed the most to the external dose rate. In the investigated area total dose rate to biota derived using ERICA Tool ranged from 0.3 to 14.4 µGy h-1. The natural radionuclides exhibited significantly higher contribution to the total dose rate than the artificial one. In the investigated area, only dose rate for lichens and bryophytes exceeded ERICA Tool screening value of total dose rate of 10 µGy h-1 suggested as confident that environmental risks are negligible. The assessed total dose rates for reference animals and plants using RESRAD BIOTA were found to be 7 and 3 µGy h-1, respectively. In RESRAD BIOTA - Level 3, 10 species (Lumbricus terrestris, Rana lessonae, Sciurus vulgaris, Anas platyrhynchos, Lepus europaeus, Vulpes vulpes, Capreolus capreolus, Suss crofa, Quercu srobur, Tilia spp.) representative for the study area were modeled. Among them the highest total dose rate (4.5 µGy h-1) was obtained for large mammals. Differences in the predicted dose rates to biota using the two software programs are the consequence of the difference in the values of transfer parameters used to calculate activity concentrations in biota. Doses of ionizing radiation estimated in this study will not exhibit deterministic effects at the population level. Thus, the obtained results indicate no significant radiation impact of coal fired power plant operation on terrestrial biota. This paper confirms the use ERICA Tool and RESRAD BIOTA softwares as flexible and effective means of radiation impact assessment.

The Swedish radiological environmental protection regulations applied in a review of a license application for a geological repository for spent nuclear fuel.

For the first time, a system for specific consideration of radiological environmental protection has been applied in a major license application in Sweden. In 2011 the Swedish Nuclear Fuel & Waste Management Co. (SKB) submitted a license application for construction of a geological repository for spent nuclear fuel at the Forsmark site. The license application is supported by a post-closure safety assessment, which in accordance with regulatory requirements includes an assessment of environmental consequences. SKB's environmental risk assessment uses the freely available ERICA Tool. Environmental media activity concentrations needed as input to the tool are calculated by means of complex biosphere modelling based on site-specific information gathered from site investigations, as well as from supporting modelling studies and projections of future biosphere conditions in response to climate change and land rise due to glacial rebound. SKB's application is currently being reviewed by the Swedish Radiation Safety Authority (SSM). In addition to a traditional document review with an aim to determine whether SKB's models are relevant, correctly implemented and adequately parametrized, SSM has performed independent modelling in order to gain confidence in the robustness of SKB's assessment. Thus, SSM has used alternative stylized reference biosphere models to calculate environmental activity concentrations for use in subsequent exposure calculations. Secondly, an alternative dose model (RESRAD-BIOTA) is used to calculate doses to biota that are compared with SKB's calculations with the ERICA tool. SSM's experience from this review is that existing tools for environmental dose assessment are possible to use in order to show compliance with Swedish legislation. However, care is needed when site representative species are assessed with the aim to contrast them to generic reference organism. The alternative modelling of environmental concentrations resulted in much lower concentrations compared to SKB's results. However, SSM judges that SKB's in this part conservative approach is relevant for a screening assessment. SSM also concludes that there are big differences in dose rates calculated to different organisms depending on which tool that is used, although not systematically higher for either of them. Finally, independent regulatory modelling has proven valuable for SSM's review in gaining understanding and confidence in SKB's assessment presented in the license application.

Radionuclides in bats using a contaminated pond on the Nevada National Security Site, USA.

Perched groundwater percolating through radionuclide contamination in the E Tunnel Complex on the Nevada National Security Site, formerly the Nevada Test Site, emerges and is stored in a series of ponds making it available to wildlife, including bats. Since many bat species using the ponds are considered sensitive or protected/regulated and little information is available on dose to bats from radioactive water sources, bats were sampled to determine if the dose they were receiving exceeded the United States Department of Energy dose limit of 1.0E-3 Gy/day. Radionuclide concentrations in water, sediment, and flying insects were also measured as input parameters to the dose rate model and to examine trophic level relationships. The RESRAD-Biota model was used to calculate dose rates to bats using different screening levels. Efficacy of RESRAD-Biota and suggested improvements are discussed. Dose to bats foraging and drinking at these ponds is well below the dose limit set to protect terrestrial biota populations.

Effects of the new wildlife transfer factors on RESRAD-BIOTA's screening Biota Concentration Guides and previous model comparison studies.

The RESRAD-BIOTA Level 1 default Biota Concentration Guides (BCGs) are generic screening environmental medium concentrations based on reasonably conservative concentration ratios (CRs). These CRs had been identified from available literature for a variety of biota organisms. The International Atomic Energy Agency (IAEA) Technical Report Series (TRS) handbook on radionuclide transfer to wildlife was recently published with data that can be compared with the RESRAD-BIOTA values. In addition, previous IAEA Environmental Modeling for Radiation Safety (EMRAS) II Biota Working Group model comparison results are examined by comparing them with those obtained using the new TRS CR values for wildlife. Since the CR affects only internal doses, the effect on the overall dose depends on the relative contribution from internal and external exposure pathways.