Review of the effectiveness of internal dosimetry monitoring regimes.

Routine monitoring is an important element of any occupational radiation protection programme to be able to determine how effective this protection is in practice. As well as providing information on normal operational conditions and routine worker dose uptakes, these programmes are also required to be able to detect the occurrence of abnormal or unexpected exposures to radionuclides, where these risks are deemed to be present in the workplace. Various monitoring techniques and methods are available and can be applied to the direct monitoring of workers or of the workplace. For many of the less radio-toxic radionuclides simple monitoring programmes are often more than sufficient to demonstrate compliance with operational and regulatory controls; however, multiple programmes, operated in parallel, are often required for the more radio-toxic radionuclides-e.g. Plutonium and americium-to be able to provide assurance that the potential risks of exposure are reliably and adequately controlled. When a potential exposure event is detected then further investigations are instigated to confirm whether an intake has occurred and to estimate the resultant dose. This paper presents an empirical review of the records of all such investigations over an eighteen-year period at the Harwell site, Oxfordshire, UK. The purposes of this review were to determine the relative effectiveness of different monitoring methods in being able to detect potential exposure events; and how efficient each method was in detecting potential exposures which, following investigation, were confirmed as real intakes. The analyses revealed that routine faecal sampling provided the better performance characteristics in terms of combined effectiveness and efficiency; and that the ability to detect potential exposures (at levels of up to 6 mSv) in the absence of any routine monitoring programme was limited. There was a very low incidence of potential exposures being detected by more than one monitoring technique, which emphasises the importance of operating multiple monitoring methods in order to optimise the probability and confidence of detecting potential exposures.

Evidence for a recent increase in delivery of atmospheric 210Pb to Oualidia lagoon, coastal Morocco.

Two sediment cores were collected from the Oualidia lagoon, on the Atlantic coast of Morocco, and analyzed for 210Pb and 137Cs activity by gamma spectrometry. The 210Pb profiles were characterized by high activity at specific depths in each core, which were attributed to substantial increases in atmospheric 210Pb input to the sediment. A modified CRS model was applied to develop age-depth relations (chronologies) for the cores and calculate sediment accumulation rates, taking into account changing unsupported 210Pb delivery and specifying the year when the increase began. Calculated 210Pb inventories (activity/area) and fluxes (activity/area/time) depend strongly on sedimentation rates and were much higher than mean values in similar coastal systems worldwide. We attempted to use 137Cs as a time marker to support the modified CRS chronologies for both cores. The 137Cs profiles, however, were affected by post-depositional cesium migration in the sediment which made it difficult to identify the 1963 atmospheric bomb-testing peak, especially in the core with low sedimentation rate. We conclude that the high activities of 210Pb detected at specific depths in the Oualidia lagoon sediment cores are a consequence of decay of radioactive 222Rn, which displayed periodic high concentrations in the overlying atmosphere.

Conversion of simulated radioactive pollutant gas concentrations for a complex building array into radiation dose.

Methods used to convert wind tunnel and ADMS concentration field data for a complex building array into effective radiation dose were developed based on simulations of a site in central London. Pollutant source terms were from positron emitting gases released from a cyclotron and clinical PET radiotracer facility. Five years of meteorological data were analysed to determine the probability distribution of wind direction and speed. A hemispherical plume cloud model (both static and moving) was developed which enabled an expression of gamma-ray dose, taking into account build-up factors in air, in terms of analytic functions in this geometry. The standard building wake model is presented, but this is extended and developed in a new model to cover the concentration field in the vicinity of a roof top structure recirculation zone, which is then related to the concentration in the main building wake zone. For all models presented the effective dose was determined from inhalation, positron cloud immersion and gamma ray plume contributions. Results of applying these models for determination of radiation dose for a particular site are presented elsewhere.

Comparison between direct measurements and modeled estimates of external radiation exposure among school children 18 to 30 months after the Fukushima nuclear accident in Japan.

After a major radioactive incident, accurate dose reconstruction is important for evaluating health risks and appropriate radiation protection policies. After the 2011 Japan Fukushima nuclear incident, we assessed the level of agreement between the modeled and directly measured dose and estimated the uncertainties. The study population comprised 520 school children from Minamisoma city, located 20 km north of the nuclear plant. The annual dose 18­30 months after the incident was assessed using two approaches: estimation using the model proposed by the Japanese government and direct measurement by radiation dosemeters. The ratio of the average of modeled and measured doses was 3.0 (standard deviation (SD): 2.0). The reduction coefficient, an index for radiation attenuation properties, was 0.3 (SD: 0.1) on average, whereas the value used in the government model was 0.6. After adjusting for covariates, the coefficient had a significant negative correlation with the air dose rate in the dwelling location (p < 0.001), indicating that stronger building shielding effects are valuable in areas with higher air contamination levels. The present study demonstrated that some overestimation may have been related to uncertainties in radiation reduction effects, and that the air contamination level might provide a more important indicator of these effects.

Dynamic dose assessment by Large Eddy Simulation of the near-range atmospheric dispersion.

In order to improve the simulation of the near-range atmospheric dispersion of radionuclides, computational fluid dynamics is becoming increasingly popular. In the current study, Large-Eddy Simulation is used to examine the time-evolution of the turbulent dispersion of radioactive gases in the atmospheric boundary layer, and it is coupled to a gamma dose rate model that is based on the point-kernel method with buildup factors. In this way, the variability of radiological dose rate from cloud shine due to instantaneous turbulent mixing processes can be evaluated. The steady release in an open field of (41)Ar and (133)Xe for 4 different release heights is studied, thus covering radionuclides that decay with a high-energy gamma and a low-energy gamma, respectively. Based on these simulations, the variability of dose rates at ground level for different averaging times in the dose measurements is analyzed. It is observed that turbulent variability in the wind field can lead to dose estimates that are underestimated by up to a factor of four when conventional long-term measurements are used to estimate the dose from short-term exposures.

Release, deposition and elimination of radiocesium ((137)Cs) in the terrestrial environment.

Radionuclide contamination in terrestrial ecosystems has reached a dangerous level. The major artificial radionuclide present in the environment is (137)Cs, which is released as a result of weapon production related to atomic projects, accidental explosions of nuclear power plants and other sources, such as reactors, evaporation ponds, liquid storage tanks, and burial grounds. The release of potentially hazardous radionuclides (radiocesium) in recent years has provided the opportunity to conduct multidisciplinary studies on their fate and transport. Radiocesium's high fission yield and ease of detection made it a prime candidate for early radio-ecological investigations. The facility setting provides a diverse background for the improved understanding of various factors that contribute toward the fate and transfer of radionuclides in the terrestrial ecosystem. In this review, we summarize the significant environmental radiocesium transfer factors to determine the damaging effects of radiocesium on terrestrial ecosystem. It has been found that (137)Cs can trace the transport of other radionuclides that have a high affinity for binding to soil particles (silts and clays). Possible remedial methods are also discussed for contaminated terrestrial systems. This review will serve as a guideline for future studies of the fate and transport of (137)Cs in terrestrial environments in the wake of the Fukushima Nuclear Power Plant disaster in 2011.

Measurement of indoor radon concentration and assessment of doses in different districts of Alexandria city, Egypt.

The main objective of this study is to assess the health hazard due to the indoor radon. Measurement studies have been carried out in 56 dwellings belonging to 14 residential areas in Alexandria city, Egypt. Results are obtained using the LR-115 (Type II) alpha track detector in "closed-can" geometry. The dosimeters were installed in bedroom, living room, and the kitchens of each house. For intercomparison purpose, dosimeters are installed in basements, ground floor, and first floor. Measured indoor radon concentrations were found to vary from 15 to 132 Bq m(-3). The average radon concentrations in living room, bedrooms, and kitchen in basements were found to vary from to be 39 ± 10, 63 ± 15 and 81 ± 25 Bq m(-3), respectively. In living room, bedrooms, and kitchen, on ground floor, the average radon concentrations were found to be 35 ± 9, 44 ± 6 and 56 ± 10 Bq m(-3), whereas on first floor, the average values are 29 ± 8, 34 ± 7 and 45 ± 8 Bq m(-3), respectively. The overall mean radon concentration in all surveyed districts has been found to be 44 ± 16 Bq m(-3). The mean annual estimated effective dose received by the residents of the studied area is estimated to be 0.75 mSv. The obtained results are compared with the indoor radon levels prescribed by the International Commission on Radiation Protection and are found to be less than the action level recommended.

Establishing a regional reference indoor radon level on the basis of radon survey data.

The establishment of national reference levels is a new requirement of the ICRP radiological protection system. For protection against indoor radon exposure measures based on a common national reference level tend to be less effective in regions where the probability of high indoor radon concentrations is relatively low in comparison with the national average. Therefore it makes sense to establish individual indoor radon reference levels for large sub-national regions as well as for urban agglomerations separately. Analysis of indoor radon surveys of the territory, taking into account the type of building, year of construction, building material, floor and other factors influencing indoor radon concentration, provides essential and important data for defining the reference level. For Ekaterinburg, Russia it is suggested to set the reference indoor radon concentration to a level of 70 Bq m(-3) which corresponds to the 90th percentile of radon concentration in a representative group of buildings constructed in the period 1970-89, in which the lowest average indoor radon concentration was observed.

Predicted indoor radon concentrations from a Monte Carlo simulation of 1,000,000 granite countertop purchases.

Previous research examining radon exposure from granite countertops relied on using a limited number of exposure scenarios. We expanded upon this analysis and determined the probability that installing a granite countertop in a residential home would lead to a meaningful radon exposure by performing a Monte Carlo simulation to obtain a distribution of potential indoor radon concentrations attributable to granite. The Monte Carlo analysis included estimates of the probability that a particular type of granite would be purchased, the radon flux associated with that type, the size of the countertop purchased, the volume of the home where it would be installed and the air exchange rate of that home. One million countertop purchases were simulated and 99.99% of the resulting radon concentrations were lower than the average outdoor radon concentrations in the US (14.8 Bq m(-3); 0.4  pCi l(-1)). The median predicted indoor concentration from granite countertops was 0.06 Bq m(-3) (1.59 × 10(-3) pCi l(-1)), which is over 2000 times lower than the US Environmental Protection Agency's action level for indoor radon (148 Bq m(-3); 4 pCi l(-1)). The results show that there is a low probability of a granite countertop causing elevated levels of radon in a home.

Assessing the possible radiological impact of routine radiological discharges from proposed nuclear power stations in England and Wales.

The aim of this work is to assess the possible radiological impact on the population of the United Kingdom (UK) from new nuclear power stations proposed for up to eight sites in England and Wales. The radiological impact was measured in terms of collective dose to the UK, European and world populations from a single year's discharge integrated to 500 and 100 000 years and the annual dose to an average member of the UK population (known as the per-caput dose). The doses were calculated for two reactor types, UK EPR™ and AP1000™, using the annual expected discharges estimated by the designers of the reactors and assuming two reactors per site. In addition, typical individual doses to adults living close to the sites were calculated on the basis of continuous discharges for 60 years (the assumed lifetime of the reactors). The dose to a representative person (previously known as the critical group) was not calculated, as this has been done elsewhere. The assessments were carried out using the software program PC-CREAM 08(®) which implements the updated European Commission methodology for assessing the radiological impact of routine releases of radionuclides to the environment. The collective dose truncated to 500 years to the UK population was estimated to be 0.5 manSv assuming UK EPR reactors on all sites and 0.6 manSv assuming AP1000s on three sites with UK EPRs on the other sites. The most significant contribution to the collective dose to the UK population is due to the global circulation of carbon-14 released to the atmosphere. The annual dose to an average member of the UK population from all sites was calculated to be around 10 nSv y(-1) and would therefore contribute little to an individual's total radiation dose. All the calculated doses to a typical adult living near the sites assuming continuous discharges for 60 years were found to be below 1 µSv y(-1).

Spatial modeling of geogenic indoor radon distribution in Chungcheongnam-do, South Korea using enhanced machine learning algorithms.

Prolonged inhalation of indoor radon and its progenies lead to severe health problems for housing occupants; therefore, housing developments in radon-prone areas are of great concern to local municipalities. Areas with high potential for radon exposure must be identified to implement cost-effective radon mitigation plans successfully or to prevent the construction of unsafe buildings. In this study, an indoor radon potential map of Chungcheongnam-do, South Korea, was generated using a group method of data handling (GMDH) algorithm based on local soil properties, geogenic, geochemical, as well as topographic factors. To optimally tune the hyper-parameters of GMDH and enhance the prediction accuracy of modelling radon distribution, the GMDH model was integrated with two metaheuristic optimization algorithms, namely the bat (BA) and cuckoo optimization (COA) algorithms. The goodness-of-fit and predictive performance of the models was quantified using the area under the receiver operating characteristic (ROC) curve (AUC), mean squared error (MSE), root mean square error (RMSE), and standard deviation (StD). The results indicated that the GMDH-COA model outperformed the other models in the training (AUC = 0.852, MSE = 0.058, RMSE = 0.242, StD = 0.242) and testing (AUC = 0.844, MSE = 0.060, RMSE = 0.246, StD = 0.0242) phases. Additionally, using metaheuristic optimization algorithms improved the predictive ability of the GMDH. The GMDH-COA model showed that approximately 7 % of the total area of Chungcheongnam-do consists of very high radon-prone areas. The information gain ratio method was used to assess the predictive ability of considered factors. As expected, soil properties and local geology significantly affected the spatial distribution of radon potential levels. The radon potential map produced in this study represents the first stage of identifying areas where large proportions of residential buildings are expected to experience significant radon levels due to high concentrations of natural radioisotopes in rocks and derived soils beneath building foundations. The generated map assists local authorities to develop urban plans more wisely towards region with less radon concentrations.

Spanish experience on modeling of environmental radioactive contamination due to Fukushima Daiichi NPP accident using JRODOS.

Since the Chernobyl Nuclear Power Plant accident, decision support systems (DSS) for supporting response of the decision makers in emergencies have been developed and refined. Data available from real accidents are used to validate these systems, thus demonstrating their real capabilities and finally to improve them. This article presents the findings of the simulation exercises using JRODOS DSS performed in Spain after the first days of the accident in the Fukushima Daiichi Nuclear Power Plant. The investigation was carried out in two phases. The first phase is considered the early phase of the accident when few details of the real emissions are known (operational modeling). The second phase demonstrates how real measurements could be used (reconstructive modeling) to improve model predictions. Only major releases to the atmosphere, occurring during the first two weeks, were taken into account. Validation of the model was performed by direct comparison of the modeled results with real measurements.

Indoor radon monitoring near an in situ leach mining site in D G Khan, Pakistan.

Indoor radon and its decay products are considered to be the second leading cause of lung cancer after cigarette smoking. This is why extensive radon surveys have been carried out in many countries of the world, including Pakistan. In this context, 25 spots were selected at workplaces in the vicinity of the uranium mining site in Dera Ghazi Khan District for indoor radon measurement. For this purpose, CR-39 based radon detectors were installed at head height and were exposed to indoor radon for 60 days. After retrieval, these detectors were etched in a 6 M solution of NaOH at the temperature of 80 °C for 16 h in order to make the alpha particle tracks visible. The observed track densities were related to the indoor radon concentration using a calibration factor of 2.7 tracks cm(-2) h(-1)/kBq m(-3). The measured indoor radon concentration ranged from ∼386 ±161 to 3028 ± 57 Bq m(-3) with an average value of 1508 ± 81 Bq m(-3) in the studied areas of Dera Ghazi Khan District. The mean annual effective dose ranged from 2.22 ± 0.93 to 17.44 ± 0.33 mSv yr(-1), with an average of 8.68 ± 0.47 mSv yr(-1). The effect of the seasonal correction factor (SCF) on the annual average radon concentration has also been considered. Results of the current study show that, for the majority of the workplaces studied, indoor radon levels exceed the action levels proposed by many world organisations.

Measurement and analysis of electromagnetic pollution generated by GSM-900 mobile phone networks in Erciyes University, Turkey.

Mobile phones are becoming increasingly important in our everyday lives. The rising number of mobile phones reflects a similar increase in the number of base stations. Because of this rapid evolution, the establishment and planning of new base stations has become mandatory. However, the rise in the number of base stations, in terms of human health, is potentially very harmful. It is important to analyze the radiation levels of base stations until we can confirm that they are definitely not harmful in the long term. Mapping of electromagnetic field (EMF) is also important from a medical point of view because it provides useful information, for example, on the detection of diseases caused by EMF. With the help of this information the distribution of diseases over different regions can be obtained. In this article, the electromagnetic radiation levels of base stations were measured at 80 different points in Erciyes University (ERU), Turkey and detailed information about the measurement tools and measurement method were given. It was observed that no area in ERU exceeded the national and international limits. It is also observed that the effects of base stations vary according to duration and degree of exposure. Therefore, if people are exposed to a very low-intensity electromagnetic field for a very long time, serious health problems can occur.

Tritium release during nuclear power operation in China.

Overviews were evaluated of tritium releases and related doses to the public from airborne and liquid effluents from nuclear power plants on the mainland of China before 2009. The differences between tritium releases from various nuclear power plants were also evaluated. The tritium releases are mainly from liquid pathways for pressurised water reactors, but tritium releases between airborne and liquid effluents are comparable for heavy water reactors. The airborne release from a heavy water reactor is obviously higher than that from a pressurised water reactor.

On protecting the inexperienced reader from Chernobyl myths.

The health and environmental consequences of the Chernobyl accident continue to attract the attention of experts, decision-makers and the general public, and now these consequences have been given added relevance by the similar accident in 2011 at the Fukushima-1 nuclear power plant (NPP) in Japan. Expert analysis of radiation levels and effects has been conducted by international bodies--UNSCEAR in 2008 and the Chernobyl Forum during 2003-5. At the same time, three Russian and Belarusian scientists, Yablokov, Nesterenko and Nesterenko (2009 Chernobyl. Consequences of the Catastrophe for People and the Environment (New York: Annals of the New York Academy of Sciences)) published both in Russian and English a substantial review of the consequences of Chernobyl based mostly on Russian-language papers. In this book, they suggested a departure from analytical epidemiological studies in favour of ecological ones. This erroneous approach resulted in the overestimation of the number of accident victims by more than 800 000 deaths during 1987-2004. This paper investigates the mistakes in methodology made by Yablokov et al and concludes that these errors led to a clear exaggeration of radiation-induced health effects. Should similar mistakes be made following the 2011 accident at Fukushima-1 NPP this could lead quite unnecessarily to a panic reaction by the public about possible health effects and to erroneous decisions by the authorities in Japan.

An assessment of radiation doses at an educational institution 57.8 km away from the Fukushima Daiichi nuclear power plant 1 month after the nuclear accident.

OBJECTIVES: On 11 March 2011, the Great East Japan Earthquake occurred. Due to this earthquake and subsequent tsunami, malfunctions occurred at the Fukushima Daiichi nuclear power plant. Radioactive material even reached the investigated educational institution despite being 57.8 km away from the power station. With the goal of ensuring the safety of our students, we decided to carry out a risk assessment of the premises of this educational institution by measuring radiation doses at certain locations, making it possible to calculate estimated radiation accumulation. METHODS: Systematic sampling was carried out at measurement points spaced at regular intervals for a total of 24 indoor and outdoor areas, with 137 measurements at heights of 1 cm and 100 cm above the ground surface. Radiation survey meters were used to measure environmental radiation doses. RESULTS: Radiation dose rates and count rates were higher outdoors than indoors, and higher 1 cm above the ground surface than at 100 cm. Radiation doses 1 cm above the ground surface were higher on grass and moss than on asphalt and soil. The estimated radiation exposure for a student spending an average of 11 h on site at this educational institution was 9.80 µSv. CONCLUSIONS: Environmental radiation doses at our educational institution 57.8 km away from the Fukushima Daiichi nuclear power plant 1 month after the accident were lower than the national regulation dose for schools (3.8 µSv/h) at most points. Differences in radiation doses depending on outdoor surface properties are important to note for risk reduction.

Awareness and perceptions of the risks of exposure to indoor radon: a population-based approach to evaluate a radon awareness and testing campaign in England and Wales.

The current study aimed to evaluate the locally directed radon roll-out program that was conducted between 2001 and 2005 in England and Wales to increase radon awareness and testing rates. A representative sample of 1,578 residents aged 16 and older were interviewed who lived in radon-affected areas of 15 local authorities in England and Wales that were eligible for participation in the program. The study systematically sampled across participating and nonparticipating local authorities, "actionable" and "nonactionable" radon-affected areas, and geographic regions with different campaign histories (Wales, Southwest England, and the rest of England). As a multistage sampling strategy was used, the data were analyzed from a multilevel perspective. This study found that participants living in participating local authorities had higher levels of awareness and were more likely to have tested their home for radon than participants living in nonparticipating local authorities. Similar results were found for participants living in "actionable" areas as compared to those living in "nonactionable" radon-affected areas. The study further found that radon awareness and testing rates were the highest in Southwest England and the lowest in Wales. This study suggests that the radon roll-out program has been effective in raising awareness and testing rates, and that ongoing domestic radon campaigns in Southwest England may have raised radon awareness and testing in these areas, showing important reinforcement effects of multiple risk communication campaigns.

Radiation hazard assessment in Egyptian painting oxides. A comparative study.

Building materials are potential sources of radiation, which represents a risk factor for human disease including cancer. In this work, the natural radioactivity due to the presence of (238)U, (226)Ra, (232)Th and (40)K in different painting oxides has been measured using gamma spectrometry with a Hyper Pure germanium detector. The concentrations of the heavy metals (Cd, Co, Mn, Pb, Ni, Sr, Rb, Cr, Cu and Zn) were determined by atomic absorption spectrometry in order to investigate their possible correlation with radioactive elements. The activity concentrations of (238)U, (226)Ra, (232)Th and (40)K ranged from 15 ± 0.75 to 126 ± 14, 2.35 ± 0.09 to 72.96 ± 1.96, 1.76 ± 0.31 to 12.88 ± 0.7 and 2.26 ± 0.09 to 200 ± 3.34 Bq kg(-1), respectively. The calculated radium-equivalents were lower than values recommended for construction materials (370 Bq kg(-1)). The absorbed dose rates due to the natural radioactivity of the investigated samples ranged from 8.11 ± 0.24 to 68.46 ± 4.20 nGy/h. Also, the results revealed that some heavy metals (Cd, Co, Mn and Rb) were correlated with (238)U, (226)Ra, (232)Th or (40)K.