Development of a methodology for assessing the environmental impact of radioactivity in Northern Marine environments

Evaluation of the environmental sensitivity of Aegean Sea based on radiological box modeling

A radiological box model of the Aegean Sea has been developed simulating the dispersion and fate of radionuclides in the marine environment. The model incorporates all transfer processes within abiotic and biotic compartments in combination with appropriate site-specific information. The model was calibrated using empirical radiological data, with the simulation of ¹³⁷Cs dispersion after the Chernobyl. Environmental sensitivity analysis has been carried out based on Chernobyl ¹³⁷Cs fallout, in terms of doses to representative marine organisms (fish, crustacean and molluscs) and human population. Comparison of the results with doses from natural sources and sensitivity estimations for shallow marine environments has been performed in order to reveal the vulnerability of each sub-region. The main characteristics and parameters controlling the radioecological processes are also discussed.

Natural radioactivity levels in sediments in Algiers Bay using instrumental neutron activation analysis

The main objective of this study is to evaluate natural radioactivity levels in sediments collected from different points of Algiers bay. Particular attention was paid to understand correlations between the distribution of uranium and thorium and the geomorphological characteristics of the Bay. Instrumental neutron activation analysis (INAA) has been employed in order to measure the isotopic composition and concentration of uranium and thorium, with emphasis on isotopes, 232Th and 238U. The concentrations reported in Bq kg−1 (dry weight) vary between 19.73 and 34.53 for 238U and between 22.26 and 36.02 for 232Th. The obtained results are within the world typical ranges and did not show any anomalous values. Results revealed clear inverse relationship between activity concentration and grain size. The radioactivity content in sediments had a positive correlation with clay and silt percentage, and a negative correlation with sand percentage. The concentration ratios of 232Th/238U are found to be slightly below the world average value unite (3.94) in sediments. Values below unite indicate that the medium is reductor or the existence of an external source of U-contaminated particles in the bay; Values greater than the unit show either depletion of uranium or enrichment of thorium due to alteration or natural processes in these areas. The strong correlation of uranium and Thorium in samples reflects the source of same origin. The results of the study can be used as basic radiometric data for future sedimentological studies. The situation in the Bay of Algiers is reassuring but the risk of possible contamination cannot be excluded and requires constant vigilance for the preservation of the coast and the Mediterranean from all contamination. The results can also be used as reference data for the monitoring of possible radioactive pollution in the future.

A new method of estimation of dose conversion coefficients for aquatic biota

In order to develop the basis of an approach, through which we can comprehend the relationships of radiation exposures and dose, and dose and radiological effects, large numbers of dosimetric data are required. It is complex to estimate the dosimetry involved due to enormous variability of organism shapes, masses, and their natural habitats. This paper aims to develop an empirical equation, which correlates dose conversion coefficients (DCCs) with organism volume V, density ρ, source energy E and curve fitting coefficients. Compared with the values calculated by a Monte Carlo method, the mean relative deviation of the empirical-fitted DCCs are reasonably low for gamma external exposure and beta internal exposure. The empirical-fitted values are very close to those calculated using a simplified anatomical phantom, the ERICA Tool or a voxel phantom.

Uranium and other natural radionuclides in the sediments of a Mediterranean fjord-like embayment, Amvrakikos Gulf (Ionian Sea), Greece

The distribution of the natural radionuclides ((238)U, (232)Th, (226)Ra, (40)K) and the artificial (137)Cs was studied in sediment cores collected from Amvrakikos Gulf, a seasonal anoxic marine basin, using γ-ray spectrometry. The activity of radionuclides, along with the concentrations of Fe and Mn, were also studied in relation to the total organic carbon and the granulometric fractions of the sediments. The results obtained revealed higher (238)U activity concentrations in all the examined sediment samples compared to the world and Greek average values for soil. The high activity values of (238)U are attributed, besides the lattice-held fraction, to phosphate fertilizer inputs in the Gulf via major rivers and/or to alteration processes of phosphate ores located mainly in the drainage basin of the river Louros. The elevated activity values of (40)K could be attributed to the mineralogical composition of the sediments and to phosphate fertilizers containing potassium. Organic matter seems to be a more efficient sorbent for U than clay minerals and amorphous Fe and Mn-oxyhydroxides. Scanning electron microscopy, together with qualitative analysis of some smectites, reveals the occurrence of U, suggesting a limited absorption of U onto clay minerals. The applied BCR sequential extraction procedure revealed that U was found mainly in the refractory phase or associated with organic matter and to a lesser extent as surface-coating oxides, with the exception of one sediment core which is characterized by high content of fresh marine organic matter and presents high percentage of U in the exchangeable fraction.

Evaluation of environmental sensitivity of the marine regions

The knowledge about environmental sensitivity of the marine regions to radionuclide release can be used for the development of response strategies and improvement of design-maker systems. The present results are based on the consequences analysis after potential Russian submarine accident involving a modern vessel. The radioecological consequences are based on modelling of potential releases of radionuclides, radionuclide transport and uptake in the marine environment. The sensitivity analysis is based on the comparison of the results of simulations with the recommendations and criterions for protection of the human population and the environment. The results show that the doses to marine organisms living in the sea sediment near the accident location, and dose rates to the critical group are the most sensitive state parameters (endpoints) for describing the consequences to the marine environment in the present evaluation.

Radioecological consequences of a potential accident during transport of spent nuclear fuel along an Arctic coastline

This article presents results pertaining to a risk assessment of the potential consequences of a hypothetical accident occurring during the transportation by ship of spent nuclear fuel (SNF) along an Arctic coastline. The findings are based on modelling of potential releases of radionuclides, radionuclide transport and uptake in the marine environment. Modelling work has been done using a revised box model developed at the Norwegian Radiation Protection Authority. Evaluation of the radioecological consequences of a potential accident in the southern part of the Norwegian Current has been made on the basis of calculated collective dose to man, individual doses for the critical group, concentrations of radionuclides in seafood and doses to marine organisms. The results of the calculations indicate a large variability in the investigated parameters above mentioned. On the basis of the calculated parameters the maximum total activity ("accepted accident activity") in the ship, when the parameters that describe the consequences after the examined potential accident are still in agreement with the recommendations and criterions for protection of the human population and the environment, has been evaluated.

Transfer of radionuclides in aquatic ecosystems--default concentration ratios for aquatic biota in the Erica Tool

The process of assessing risk to the environment following a given release of radioactivity requires the quantification of activity concentrations in environmental media and reference organisms. The methodology adopted by the ERICA Integrated Approach involves the application of concentration ratios (CR values) and distribution coefficients (K(d) values) for aquatic systems. Within this paper the methodologies applied to derive default transfer parameters, collated within the ERICA Tool databases, are described to provide transparency and traceability in the documentation process. Detailed information is provided for the CR values used for marine and freshwater systems. Of the total 372 CR values derived for the marine ecosystem, 195 were identified by literature review. For the freshwater system, the number of values based on review was less, but still constituted 129 from a total of 372 values. In both types of aquatic systems, 70-80% of the data gaps have been filled by employing "preferable" approaches such as those based on substituting values from taxonomically similar organisms or biogeochemically similar elements.