Radiological Impact Assessment Research Articles

Influence of climate on landscape characteristics in safety assessments of repositories for radioactive wastes

In safety assessments of repositories for radioactive wastes, large spatial and temporal scales have to be considered when developing an approach to risk calculations. A wide range of different types of information may be required. Local to the site of interest, temperature and precipitation data may be used to determine the erosional regime (which may also be conditioned by the vegetation characteristics adopted, based both on climatic and other considerations). However, geomorphological changes may be governed by regional rather than local considerations, e.g. alteration of river base levels, river capture and drainage network reorganisation, or the progression of an ice sheet or valley glacier across the site. The regional climate is in turn governed by the global climate.In this work, a commentary is presented on the types of climate models that can be used to develop projections of climate change for use in post-closure radiological impact assessments of geological repositories for radioactive wastes. These models include both Atmosphere-Ocean General Circulation Models and Earth Models of Intermediate Complexity. The relevant outputs available from these models are identified and consideration is given to how these outputs may be used to inform projections of landscape development. Issues of spatial and temporal downscaling of climate model outputs to meet the requirements of local-scale landscape development modelling are also addressed. An example is given of how climate change and landscape development influence the radiological impact of radionuclides potentially released from the deep geological disposal facility for spent nuclear fuel that SKB (the Swedish Nuclear Fuel and Waste Management Company) proposes to construct at Forsmark, Sweden.

Numerical simulation of air pollutant dispersion using an in situ tracer experiment at a nuclear site

A tracer dispersion experiment was conducted at the Wolsong Nuclear Power Plant, Korea to determine concentrations of airborne radioactive materials under weather conditions unfavorable to dispersion. The observed concentrations were compared with estimates from a Gaussian plume model to determine whether the model provides sufficiently conservative estimation under bad weather conditions and is therefore suited to radiological impact analysis at nuclear power facilities. It was found that the more often the meteorological data was used, the more advantageous it was in helping to understand the diffusion characteristics of radioactive materials.Most of the current computer models for estimating the dispersion of airborne radioactive materials, which are needed to gain construction approval for a nuclear power plant, are based on the Gaussian plume model. Overall, the Gaussian plume model overestimates the concentration of airborne radioactive materials compared with actual observations. This suggests that the model is suitably conservative to enable its use in radiological environmental impact assessment of the health risks to nearby communities.

Assessment of atmospheric dispersion and radiological impact from the Fukushima accident in a 40-km range using a simulation approach

In this study, radiation doses and lifetime attributable health risk to the members of public in a 40-km impact zone around the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) were assessed for the airborne releases that occurred during 11–31 March 2011 from the loss of coolant accident associated with the east Japan earthquake and tsunami event. High-resolution simulations with FLEXPART-WRF Lagrangian particle dispersion model were made using available source term estimates for four significant isotopes (Cs134, Cs137, I131, Xe133). Radiation risk models were adopted to estimate the health risk for leukemia, breast, thyroid, and all solid cancers using simulated distributed lifetime organ doses. The simulations indicate occurrence of hotspots in the spatial activity deposition and radiation dose distribution with high values in the northwest and south-southwest land sectors in a 40-km radius. Large activity depositions (106 to 108 Bq/m2 of Cs137 between 12 and 31 March 2011) and external air doses (10 to 100 μSv/h) are simulated in the above sectors. The simulated air dose rates are found to match with observed doses at 85 % of the monitor stations within a factor of 5. It is estimated that the groundshine and ingestion dose are the principal contributors of the effective dose. Simulated average effective dose during the first year of exposure varied as ~150 mSv in the first few kilometers to 2 mSv at 40 km. The risk incidence was estimated to be high for infants compared to the children and adult age group for all types of cancers. The first 0–20-km range of the FDNPP is characterized with high risk for all types of cancers, for example, 10 to 20 in 10,000 adults for leukemia. The analysis shows that the immediate implementation of countermeasures of evacuation in the 0–20-km zone, sheltering in the 20–40-km zone, and food restrictions by Japan actually reduced significant health risks to the population living near FDNPP. Simulated yearly distribution of total dose indicates that people of evacuated zone can be rehabilitated in about 16 years in the 5–10-km area and 7 years in the 10–20-km area with minimum risk, whereas the near reactor zone of 0–5 km and areas along the plume footprint up to 20 km in the northwest sector of FDNPP require special attention and reclamation measures for rehabilitation. This study demonstrates a total simulation-based approach for estimating the radiation risk for the Fukushima case and helps to assess the time attainment of low risk for inhabitation of the people in the affected areas.

Recycling and reuse of very low level radioactive steel in motorway tunnel scenario

Since a number of nuclear power plants are approaching the end of their lifetime is continuously increasing, decommissioning issues and radioactive waste management have become widely discussed topics. Considerable amounts of materials arising from decommissioning could be categorized as very low level radioactive waste. In line with international incentives for optimization of radioactive material management, alternative concepts of recycling and reuse of materials are suggested, analyzed and discussed. One of these concepts of such optimization is the conditional clearance of materials with their subsequent recycling and reuse in the industrial sector. The present paper describes an option of recycling and reuse of conditionally cleared steel in motorway tunnels.The analyzed scenario assumes that very low level radioactive steel would be reused in the form of steel reinforcing components, such as reinforcing mesh and bars, assembled in the primary and secondary linings of a motorway tunnel.However, prior to real application, a radiological impact assessment has to be done in order to prove compliance with radiation protection criteria. Methodology for implementation of the concept of conditional clearance was created and applied on two selected NPPs located in the Slovak Republic, which are currently under decommissioning. Assessment of relevant exposure pathways, which are likely to occur in the analyzed scenario, was performed.The aim of the paper is to derive and to justify new clearance levels for each radionuclide contained in steel reinforcement components in order to reuse the maximum amount of very low level radioactive steel considering radiation protection criteria. An increase of recyclable amount of radioactive steel could bring benefits in the form of saving considerable financial resources.

Global Transport and Deposition of 137Cs Following the Fukushima Nuclear Power Plant Accident in Japan: Emphasis on Europe and Asia Using High–Resolution Model Versions and Radiological Impact Assessment of the Human Population and the Environment Using Interactive Tools

The earthquake and the subsequent tsunami that occurred offshore of Japan resulted in an important loss of life and a serious accident at the nuclear facility of Fukushima. The "hot spots" of the release are evaluated here applying the model LMDZORINCA for (137)Cs. Moreover, an assessment is attempted for the population and the environment using the dosimetric scheme of the WHO and the interactive tool ERICA, respectively. Cesium-137 was deposited mostly in Pacific and Atlantic Oceans and North Pole (80%), whereas the rest in the continental areas of North America and Eurasia contributed slightly to the natural background (0.5-5.0 kBq m(-2)). The effective dose from (137)Cs and (134)Cs (radiocesium) irradiation during the first 3 months was estimated between 1-5 mSv in Fukushima and the neighboring prefectures. In the rest of Japan, the respective doses were found to be less than 0.5 mSv, whereas in the rest of the world it was less than 0.1 mSv. Such doses are equivalent with the obtained dose from a simple X-ray; for the highly contaminated regions, they are close to the dose limit for exposure due to radon inhalation (10 mSv). The calculated dose rates from radiocesium exposure on reference organisms ranged from 0.03 to 0.18 μGy h(-1), which are 2 orders of magnitude below the screening dose limit (10 μGy h(-1)) that could result in obvious effects on the population. However, these results may underestimate the real situation, since stable soil density was used in the calculations, a zero radiocesium background was assumed, and dose only from two radionuclides was estimated, while more that 40 radionuclides have been deposited in the vicinity of the facility. When monitoring data applied, much higher dose rates were estimated certifying ecological risk for small mammals and reptiles in terms of cytogenetic damage and reproduction.

Estimation of radioactive leakages into the Pacific Ocean due to Fukushima nuclear accident

High concentrations of several radionuclides were reported in the sea near the Fukushima Daiichi Nuclear Power Station (FDNPS) in Japan due to the nuclear accident that occurred on 11 March 2011. The main source of these concentrations was leakage of highly radioactive liquid effluent from a pit in the turbine building near the intake canal of Unit-2 of FDNPS through a crack in the concrete wall. In the immediate vicinity of the plant, seawater concentrations reached 68 MBq m−3 for 134Cs and 137Cs, and exceeded 100 MBq m−3 for 131I in early April 2011. These concentrations began to fall as of 11 April 2011 and, at the end of April, had reached a value close to 0.1 MBq m−3 for 137Cs. Following the nuclear accident, the Tokyo Electric Power Company (TEPCO) had initiated intense monitoring of the environment including the Pacific Ocean. Seawater samples were collected and the concentrations of few radionuclides were measured on a wide spatial and temporal scale. In this study, the measured concentrations of different radionuclides near the south discharge canal of the FDNPS were used to estimate their leakages into the Pacific Ocean. The method is based on estimating the release rates that reproduce the concentration of radionuclides in seawater at a chosen location using a two-dimensional advection–dispersion model in an iterative manner. The radioactive leakages were estimated as 5.68 PBq for 131I, 2.24 PBq for 134Cs and 2.25 PBq for 137Cs. Leakages were also estimated for 99mTc, 136Cs, 140Ba and 140La and they range between 0.02 PBq (99mTc) and 0.53 PBq (140Ba). It was estimated that about 11.28 PBq of radioactivity in total was leaked into the Pacific Ocean from the damaged FDNPS. Out of this, 131I constitutes 50.3 %; 134Cs 20 %; 137Cs 20 %; 140Ba 4.6 %; 136Cs 2.6 %; 140La 2.3 % and 99mTc 0.2 % of the total radioactive leakage. Such quantitative estimates of radioactive leakages are essential prerequisites for short-term and local-scale as well as long-term and large-scale radiological impact assessment of the nuclear accident.

Assessment of Gamma-Radiation Levels in Selected Oil Spilled Areas in Rivers State, Nigeria

A prelude radiological impact assessment of oil spillage on the oil spilled environment, those saddled with the responsibility of cleaning the spilled crude and the host/nearest communities residents in Rivers State Nigeria has been examined in-situ, using radiation meters (Digilert 100 nuclear radiation meter) and a geographical positioning system (GPS). Readings were taken twice in a month for three months in the five different oil spilled site and one measurement taken at a control site where there is no oil spillage but within oil bearing community. The average radiation values in all the oil spilled site is 0.019±0.006mRh-1, this is far above the 0.011±0.003mRh-1obtained for the control and ICRP 0.013±0.005mRh-1 world background levels. The average equivalent dose rate obtained in all the five studied site is 1.6mSvy-1 while the dose rate in the control is 0.93mSvy-1. The results showed that all the oil spilled sites yearly equivalent dose rate exceeded the 1mSvy-1 maximum permissible limit recommend for the public and non-nuclear industrial environment by International Council on Radiological Protection (ICRP,1999). All the oil spilled environment radiation levels exceeded the normal world average BIR level of 0.013mRh-1and other reported values in similar environment. This shows that the oil spilled environment have been impacted radiologically. This will pose some long-term health side effects on the clean-up workers and residents of the host communities. Interim proactive measures are recommended while further and a detail study is ongoing.

Public exposure from environmental release of radioactive material under normal operation of unit-1 Bushehr nuclear power plant

The Unit-1 Bushehr Nuclear Power Plant (BNPP-1), constructed at the Hallileh site near Bushehr located at the coast of the Persian Gulf, Iran, is a VVER type reactor with 1000MWe power. According to standard practices, under normal operation conditions of the plant, radiological assessment of atmospheric and aquatic releases to the environment and assessment of public exposures are considered essential. In order to assess the individual and collective doses of the critical groups of population who receive the highest dose from radioactive discharges into the environment (atmosphere and aquatic) under normal operation conditions, this study was conducted. To assess the doses, the PC-CREAM 98 computer code developed by the Radiation Protection Division of the Health Protection Agency (HPA; formerly called NRPB) was applied. It uses a standard Gaussian plume dispersion model and comprises a suite of models and data for estimation of the radiological impact assessments of routine and continuous discharges from an NPP. The input data include a stack height of 100m annual radionuclides release of gaseous effluents from the stack and liquid effluents that are released from heat removal system, meteorological data from the Bushehr local meteorological station, and the data for agricultural products. To assess doses from marine discharges, consumption of sea fish, crustacean and mollusca were considered. According to calculation by PC-CREAM 98 computer code, the highest individual dose in terrestrial area for adults is 14×10−5mSv/y in ESE direction and 600m distance from stack. Also, the individual dose via discharge of liquid effluents to the Persian Gulf is 5×10−7mSv/y. Furthermore, total collective dose around BNPP-1 site within 100km radial is calculated using local data and consumption habits. The results show that the radiological impact of the BNPP-1 on the critical groups of public and the individual effective doses are in good agreement with the values given in the Final Safety Analysis Report (FSAR-2007) and the Environmental Report of the BNPP-1. Also the calculated ambient gamma dose rates match relatively well with the monitored dose rate values of the environmental monitoring stations around the reactor under normal operation conditions. It can also be concluded that the estimated effective doses are lower than the dose constraint of 0.1mSv/y associated with this plant. The results are presented and discussed.

Wilk’s Method Based Model for Regulations Related to Radiological Impact of Opencast Uranium Mining on Water Reservoirs

Opencast mining of uranium may lead to natural erosion of ore material due to overland flow of water accumulated from rainfall. The overland flow may ultimately reach the nearby surface water body. This process may lead to the release of 238U and its daughter products into the surface water body. A model is developed to assess the radiological impact of the erosion in terms of dose through drinking water pathway due to 238U and its progeny in the surface water body. The in-growth of progeny is taken into account using Bateman equations. The study brings out the importance of incorporating decay chain transport in the radiological impact assessment studies. It is also observed that 210Po, 210Pb, 226Ra, and 230Th together contribute to about 95.5 % of the total dose. The model is then extended to incorporate the uncertainty associated with the dose due to consumption of the reservoir water by employing Wilk’s Method. Such a model can be very useful in establishing regulations related to dose through drinking water pathway around an opencast mine. Wilk’s method is computationally less expensive as compared to the exact methods like Monte Carlo method. Wilk’s method is used to calculate a value greater than α percentile value for the dose to the public due to 238U and its progeny in the reservoir through drinking water pathway with confidence level β (α/β value). When applied to a hypothetical case using some literature data on surface water bodies, it is found that with increase in the value of α or β, the α/β value in general, shows an increasing trend as expected. Depending upon the nature of the problem under study, one can calculate an α/β value i.e. 95/95 value, 99/95 value etc., and that value can be helpful in establishing the regulatory limiting value. Also, the α/β value can be used to check whether dose due to a particular radioactive release is within the specified limits.

Response Surface Method Coupled with First-Order Reliability Method Based Methodology for Groundwater Flow and Contaminant Transport Model for the Uranium Tailings Pond Site

Groundwater flow and contaminant transport modelling is carried out to predict the concentrations of radionuclides in groundwater beneath the tailings pond. This is used as a tool for radiological impact assessment studies. The geo-hydrological parameters involved in the modelling exhibit inherent uncertainty associated with their values. This uncertainty may get propagated to the model output, i.e. the dose to the public. The propagation of the uncertainty in the input parameters to the output is modelled using suitable methods of probabilistic analysis. Response surface method coupled with first-order reliability method is used to develop a methodology for estimating the probability that the dose rate value through drinking water pathway at a location around the tailings pond exceeds the WHO guidelines for drinking water, termed as the probability of exceedance of acceptable levels. This method also gives the estimate of sensitivity of the probability of exceedance to the different input parameters. It is observed that the probability of failure decreases as the distance from tailings pond centre is increased and beyond a distance of around 0.5 km from tailings pond centre, the probability reduces to zero. The work also brings out the importance of quantifying the uncertainty in case of actual field problems where there is wide variation in the values of the various parameters within the domain under study.

Activity concentration and radiological impact assessment of 226Ra, 228Ra and 40K in drinking waters from (OML) 30, 58 and 61 oil fields and host communities in Niger Delta region of Nigeria

This paper presents the concentrations of naturally occurring radionuclides (226Ra, 228Ra and 40K) measured in hand dug wells, boreholes and river waters collected from three oil mineral leases (OML) 30, 58 & 61 oil and gas fields onshore of the Niger delta, using gamma spectroscopy. Fifty-four water samples from the three sources of drinking water supply were collected within the oil fields and host communities and three water samples from a control site. The results showed average activity concentrations of 226Ra, 228Ra and 40K as 8.9 ± 1.0, 8.1 ± 0.9 and 39.8 ± 3.3 respectively for hand dug wells, 4.4 ± 0.8, 4.6 ± 0.5 and 28.5 ± 3.0 for borehole water and 8.2 ± 1.0, 6.7 ± 0.7 and 32.1 ± 3.5 for river water respectively. These 226Ra, 228Ra and 40K average are well above the WHO permissible levels of 1.0, 0.1 and 10 BqL−1 respectively and also above the control values. Although the hazard indices calculated are still within their tolerable levels, the estimated committed effective dose due to intake of the sampled water for all the four age groups considered are far above the ICPR 0.1 mSvyr−1 maximum permissible limit. The result indicates some level of water pollution in the studied area.

Estimation of naturally occurring radionuclides in fertilizers using gamma spectrometry and elemental analysis by XRF and XRD techniques

The fertilizers are essential in agriculture as they supply nutrients to the farming fields. One of the sources of radioactivity other than those of natural origin is mainly due to extensive use of fertilizers. The concentrations of natural radionuclides, namely 226Ra,232Th and 40K in different chemical fertilizers used in agricultural soil were analyzed using gamma spectrometry with a high purity germanium (HPGe) detector in order to assess the implications of the extended use of phosphate fertilizers in recent years. The radiological impact assessment in an integrated manner assessing doses to members of the public via the atmospheric aquatic and secondary pathways was made. The concentration of major elements (AI2O3, SiO2, P2O5, SO3, CI, K2O, Fe2O3) along with other elements present in all samples were measured by X-ray fluorescence (XRF) analysis. The X-ray diffraction (XRD) system was used for analyzing the composition of fertilizer samples. The XRD results confirmed the presence of main constituents fluorapatite Ca5(PO4)3F, hydroxylapatite Ca5(PO4)3(OH) and chlorapatite Ca5(PO4)3CI of phosphate fertilizer samples.

Natural Radionuclide Concentrations and Radiological Impact Assessment of River Sediments of the Coastal Areas of Nigeria

This work was carried out to measure the radioactivity level in the coastal areas of Nigeria by gamma counting of river sediment samples and assess the radiological impact associated with the use of the river sediments as building material. The method of gamma spectrometry with a 7.6 cm by 7.6 cm NaI(Tl) detector was employed in determining 40K, 238U and 232Th levels in 95 and 38 sediment samples respectively collected from representative sites in the oil producing and non oil producing coastal areas of Nigeria. Results of the samples assayed showed that the radioactivity concentrations of 40K, 226Ra and 228Ra in the sediment samples of oil producing areas range from 95.4 to 160.0; 7.6 to 31.0 and 9.5 to 41.6 Bq kg–1, respectively. The respective means were calculated as 122.39 ± 47.49; 18.93 ± 12.53 and 29.31 ± 18.67 Bq kg–1. In the sediment samples from the non oil producing areas, the respective mean values are 88.48 ± 8.22, 14.87 ± 3.51 and 16.37 ± 3.87 Bq kg–1. Statistical analysis of the results showed that there is no significant difference between the radionuclide concentration of the sediment samples from different rivers in the oil producing and non oil producing coastal areas, except for 40K. The values of the natural radionuclide concentrations however translate to the determina-tion of the radiological impact assessment values. The values of the radiological assessment indices obtained were ob-served to be lower than limits internationally reported and recommended for building materials. It could therefore be reported that the operations of the oil companies in the coastline, involving use of radioactive materials have not contributed adversely to the radioactivity level of the river sediments and that the use of river sediments as building mate-rial in the coastal areas of Nigeria poses no radiological risk.

A first order assessment of the potential radiological impact of foodstuffs grown in a catchment area influenced by mining and mineral processing industries

Natural radioactivity is associated with the vast mineral resources in South Africa in such concentrations that the radionuclides from the natural uranium and thorium decay series are found to pose concern for public exposure to communities living around these areas. Consumption of water and food is usually the most important route by which natural radionuclides can enter the human body and assessment of natural radionuclide levels in different foods and diets is therefore important to estimate the intake of these radionuclides by man. Sensitive measurement of three major radionuclides (in addition to 238 U, 234 U, 232 Th, 226 Ra, 224 Ra and 223 Ra) is necessary to calculate the estimated annual dose with a high degree of certainty i.e. 230 Th, 210 Pb and 210 Po, while 231 Pa, 227 Ac and 228 Ra also require improved sensitivity. In order to evaluate the yearly dose due to an individual source at a screening level of 25 μSv/a, one is faced with a required lower limit of determination (LLD) of 0.1 to 0.5 Bq/kg for certain foodstuffs. In this study the potential radiological impact of foodstuffs grown in a catchment area influenced by mining and mineral processing industries in South Africa, was determined by measuring the natural radionuclides in a number of foodstuffs collected from the area. The radionuclides were measured by non-destructive techniques such as Instrumental Neutron Activation Analysis (INAA) and low background gamma spectrometry. The assessment of natural radionuclides in foods allowed us to evaluate the items that present the highest risk to the population, and compare this to the limits established by the National Nuclear Regulator (NNR). From the public’s point of view it is important to ensure the population that the contaminant levels in specific food as a result of mining activities, do not exceed the permissible limits. For the majority of the analysed foodstuffs, the estimated dose was less than 250 μSv/a. Overestimation of dose, due to poor measurement detection limits, was clearly indicated for some of the samples. For most of the analysed nuclides, suitable data for evaluation of the yearly dose at the screening level of 25 μSv/a was obtained by broad energy gamma analysis of ashed samples. However, nuclides such as 230 Th, 210 Po and 231 Pa has to be analysed by radiochemical separation through acid destruction of dried foodstuffs followed by individual element separations to provide suitable data with a low enough LLD not to result in an overestimation of the calculated dose.

Elaboration on a radiological environmental impact assessment methodology for Northern environments

The present work encompasses some key aspects of a 3-year long research project (INTRANOR) where the main focus has been specifically on environmental assessments for radiation exposure through application of existing methodologies and their adaptation to quantify transfer, exposure and effects in Boreal/Arctic ecosystems. Non-parametric statistical methods have been applied in order to estimate the threshold dose rates above which radiation effects can be expected in vertebrate organisms. In addition, industrial areas contaminated by uranium mill tailings and radium production wastes, in the Komi Republic, Russia, were selected as suitable sites to study further the effects of exposure to radiation under boreal conditions. Dose–effect relationships have been established for a few natural populations inhabiting this area. Analyses of data have allowed benchmarks to be established below which no decrease in reproductive capacity could be observed. Other work performed within the project includes the collation of data in relation to naturally occurring radionuclides and application of existing methodologies to characterise background radiation exposures. These dose-rates may be a suitable means of contextualising the exposure attributable to enhanced dose-rates arising from human activities. Finally, combined action of ionizing radiation and low temperature has been analyzed and mathematically modelled.

An assessment of the external radiological impact in granites and pegmatite in central Eastern Desert in Egypt with elevated natural radioactivity

The contents of natural radionuclides ((226)Ra, (232)Th and (40)K) were measured in investigated samples (granite Gabal Ras Barud, Eastern Desert in Egypt) by using gamma spectrometry (NaI (Tl) 3″×3″). The activities of (226)Ra, (232)Th series and (40)K are between (3.8±0.5 and 172.8±1135.1±56.8 8.6), (2.3±0.3 and 103.8±5.2) and (53.1±2.7 and 1135.1±56.8) Bq kg(-1), respectively. With average total annual dose being only 67.2 μSv y(-1), this value is about 6.72 % of the 1.0 mSv y(-1) recommended by the International Commission on Radiological Protection (ICRP-60, 1990) as the maximum annual dose to members of the public. Geochemical studies revealed that Gabal Ras Barud is formed from a highly fractionated biotite granite, with SiO(2) >75 % and generally enriched in alkali with K/Na >8 %.

Estimation of dose rates to humans exposed to elevated natural radioactivity through different pathways in the island of Ikaria, Greece

A radiological survey has been carried out in the island of Ikaria based on the natural radionuclide inventory in abiotic environment and the consequent dose rate assessment for the critical groups of population. The island of Ikaria-Aegean Sea, Greece is characterised by the presence of mineral and thermo-mineral springs, which have an apparent influence on natural background radiation of the island. The levels of natural radionuclides in spring water (either for spa treatment and household use), potable water (local domestic network), and rock and soil samples were measured in this island. The concentrations of (222)Rn and natural gamma emitters were found to be significantly elevated in spring water and some rock and soil samples. In terms of NORM and TENORM, the external and internal dose rates (mSv y(-1)) were estimated in three groups of population selected on the basis of water use as: habitants of the island, working personnel and bathers in spa installations. According to the derived results, the working personnel in the thermal spa installations are exposed to significant radiological risk due to waterborne (222)Rn with a maximum dose rate up to 35 mSv y(-1), which led to overexposure in terms of the 20 mSv y(-1) professional limits. Therefore, this group can be considered as the critical one for the radiological impact assessment in the island.

Assessment of terrestrial gamma exposure to the population of Belgrade (Serbia)

The activity concentrations of (226)Ra, (232)Th and (40)K in 178 samples from 52 locations of the territory of Belgrade, the capital of Serbia, were determined by gamma-ray spectrometry. Based on the results obtained, the values of absorbed gamma dose rate at 1 m above the ground, radium equivalent activity, external hazard index, annual effective dose, annual gonadal dose and excess lifetime cancer risk were calculated. The results of the present study were compared with values reported worldwide and also with internationally recommended values. The total absorbed dose rate varied between 24.7 and 89.6 nGy h(-1) with a mean of 60.5 nGy h(-1), which is close to the world average value. Since all estimated radiological impact assessment factors were lower than the recommended values there seems to be no radiological health hazard for the population living in the investigated area.

Plutonium in the environment: key factors related to impact assessment in case of an accidental atmospheric release

Abstract This paper deals with plutonium and key factors related to impact assessment. It is based on recent work performed by CEA which summarize the main features of plutonium behaviour from sources inside installations to the environment and man, and to report current knowledge on the different parameters used in models for environmental and radiological impact assessment. These key factors are illustrated through a case study based on an accidental atmospheric release of Pu in a nuclear facility.

Role and uncertainty of foliar transfer in radiological impact assessments: State of the art and future actions

Sensitivity analyses have shown major role of foliar transfer for many radionuclides in the context of radiological impact assessments. A review of the published literature about foliar transfer focusing on translocation factors was carried out in order to constitute an updated database on one hand and to use the appropriate existing values of translocation parameters for modeling on the other. Translocation describes the distribution of radionuclides within the plant after foliar deposition and radionuclide absorption onto the surface of leaves. It mainly depends on elements and the plant growth stage. The collected data was derived from both in-field and greenhouse experiments. It was analysed to select those coming from a contamination simulating sprinkling irrigation or rain.This work not only allowed us to carry out a diagnosis on the values themselves but also enabled us to ascertain missing data needs. In order to compensate for the lack of data on important radionuclides concerning radioactive waste (129 I, 36 Cl, 79 Se), experimental studies have been launched.