Risk assessment for the optimization of the grid of a telemetric network monitoring system.

The goal of this work was to develop a methodology for risk assessment in case of an accident originating from a nuclear power plant, and consequently, to improve the relevant radiation monitoring network. In specific, the study involved risk estimation in Greece from a transboundary nuclear power plant accident. The tool employed was JRODOS (Java-based Real-time Decision Support), which is a system for off-site emergency management of radioactive material in the environment. This tool, widely used to generate and study scenarios for nuclear accidents worldwide, provides valuable insight to facilitate emergency preparedness and response. The probability of the plume arriving at numerous regions within the country was calculated, along with the maximum dose rates in case of transport. A risk assessment was performed, and geographical regions were prioritized in terms of risk-based environmental radioactivity burden. A total of 29 administrative districts were identified as low to medium-risk regions. Acquired results were used to determine the optimal spatial distribution of detectors for upgrading the existing monitoring network of environmental radioactivity.

Preliminary safety assessment for planning near surface disposal of low-level radioactive waste in Greece.

This paper presents the approach, assumptions, and computational analysis of the preliminary safety assessment, regarding the post-closure period for the disposal of radioactive waste in Greece. The assessment was implemented in the context of the National Program for the disposal of radioactive waste in the country, which is currently in the early stage for the investigation of facility siting. The basis scenario selected for this investigation was the leaching of radionuclides and the exposure in a residence offsite. Moreover, a scenario involving the intrusion in the facility and construction of a dwelling that disturbs the disposal zone is also considered. Due to the significant uncertainties in the current phase, the simulations related to leaching of the waste both in the offsite and intrusion scenarios are based on an uncertainty analysis with 25 site and scenario related parameters. The most important contribution is attributed to Ra-226 with an annual dose equal to about 2 and 3 µSv per MBq disposed, for the offsite and intrusion scenario, respectively. Th-232, Cl-36, C-14, Ag-108m and Pu-239 follow with a dose one order of magnitude less, compared to Ra-226. In the leaching scenarios examined, and for the most dose relevant radionuclides, the exposure related to drinking water from the well and the use of this water to irrigate fruits and vegetables are by far the dominant pathways due to the environmental transfer of the radionuclides and their associated dose coefficients. Th-232 dominates the direct exposure pathways (direct external radiation and plant contamination from the contaminated surface soil) in the intrusion scenario with an annual dose of about 1.4 mSv per Bq/g disposed. Ra-226, Cl-36 and Ag-108m cause exposure levels higher than 0.2 mSv/y per Bq/g disposed in the facility. A wide range was considered for the uncertainty parameters that led to a significant variation in the predicted doses that is expected to envelope the potential exposure for each radionuclide.

Children's exposure to size-fractioned particulate matter: Chemical composition and internal dose.

The health effects of the particulate matter (PM) depend not only on its aerodynamic diameter (AD) and chemical composition, but also on the time activity pattern of the individuals and on their age. The main objective of this work was to assess the exposure of children to aerosol particles by using personal instruments, to study the particle size and composition of the inhaled PM, and to estimate their transport and deposition into the human respiratory tract (HRT). The average daily PM2.5 exposure was 19 µg/m3 and the size fractions with the greatest contribution to PM2.5 concentrations were 1 < AD <2.5 µm and AD <0.25 µm. Results indicated a contribution of 9% from the mineral aerosol, 7.2% from anthropogenic sulphate, 6.7% from black carbon and 5% from anthropogenic trace elements to the daily exposure to PM2.5. The levels of mineral and marine elements increased with increasing particle size, while anthropogenic elements were present in higher concentrations in the finest particles. Particle size has been shown to influence the variability of daily dose deposited between the extrathoracic and alveolar-interstitial zones. On average, 3% of the PM deposited in the bronchial region, whereas 5% to 8% were found in the bronchiolar region. The level of physical activity had a significant contribution to the total daily dose.

PRACTICAL GUIDANCE ON THE REGULATORY MANAGEMENT OF RADIOACTIVE LIQUID DISCHARGES FROM MEDICAL, EDUCATIONAL AND RESEARCH LABORATORIES.

License applicants are often faced with the need to perform a radiological impact assessment study for the liquid discharges in public sewers, even for practices with short-lived isotopes used in medical, educational or research laboratories. The present paper addresses the regulatory management challenges in performing such assessments and provides a practical calculation toolbox that enables more realistic derivation of doses to critical members, based on a simple calculation means. The proposed methodology is validated through comparisons with results from other models. The effectiveness of the method is illustrated by considering relevant examples of hospitals and education and research establishments in Greece. The results show that the proposed method is a sound tool that achieves a more realistic estimation of the induced doses. In most cases a reduction in the initial screening dose estimates by several orders of magnitude is attained, thus greatly facilitating the effort needed to ascertain regulatory compliance.

A Holistic Approach to Assessment of Population Exposure to Radiation: Challenges and Initiatives of a Regulatory Authority.

A regulatory authority for radiation safety should continuously evaluate and improve the national safety framework, in line with current requirements and standards. In this context, the Greek Atomic Energy Commission initiated a series of concerted actions. The radiation dose to the population due to public and medical exposures was assessed. The assessment of dose due to public exposure was based on measurements of radon concentrations in dwellings, radionuclide concentrations in environmental samples, and air dose rates; the assessment of dose due to medical exposure was based on dose measurements for typical examinations or procedures and data on their frequency. The mean effective dose to a member of the population was found to be 4.5 mSv (1.8 mSv and 2.7 mSv from medical and public exposures, respectively). Regarding occupational exposure, aircrew dose assessment, eye lens monitoring, and the national dose registry were significantly improved. With respect to artificial tanning (sun beds), the ultraviolet radiation produced was assessed and the practices followed were observed. Results demonstrated exceedance of the 0.3 W m erythema effective irradiance limit set in European Union standards by 63.5% of the sun beds measured, along with general noncompliance with standards. An overarching activity was the upgrade of the Greek Atomic Energy Commission information system in order to collect and disseminate radiation data electronically, launch a networking strategy for interaction with stakeholders, and facilitate the process of regulatory control. In response to the above findings, regulatory actions have been initiated.

Towards an alternative testing strategy for nanomaterials used in nanomedicine: lessons from NanoTEST.

In spite of recent advances in describing the health outcomes of exposure to nanoparticles (NPs), it still remains unclear how exactly NPs interact with their cellular targets. Size, surface, mass, geometry, and composition may all play a beneficial role as well as causing toxicity. Concerns of scientists, politicians and the public about potential health hazards associated with NPs need to be answered. With the variety of exposure routes available, there is potential for NPs to reach every organ in the body but we know little about the impact this might have. The main objective of the FP7 NanoTEST project ( www.nanotest-fp7.eu ) was a better understanding of mechanisms of interactions of NPs employed in nanomedicine with cells, tissues and organs and to address critical issues relating to toxicity testing especially with respect to alternatives to tests on animals. Here we describe an approach towards alternative testing strategies for hazard and risk assessment of nanomaterials, highlighting the adaptation of standard methods demanded by the special physicochemical features of nanomaterials and bioavailability studies. The work has assessed a broad range of toxicity tests, cell models and NP types and concentrations taking into account the inherent impact of NP properties and the effects of changes in experimental conditions using well-characterized NPs. The results of the studies have been used to generate recommendations for a suitable and robust testing strategy which can be applied to new medical NPs as they are developed.

Environmental measurements and inspections on imported foods and feedstuffs in Greece after the Fukushima accident.

The radionuclides released during the accident at the Fukushima Daichii nuclear power plant following the Tohoku earthquake and tsunami on 11 March 2011 were dispersed in the whole north hemisphere. Traces of (131)I, (134)Cs and (137)Cs reached Greece and were detected in air, grass, sheep milk, ground deposition, rainwater and drainage water. Members of Six Greek laboratories of the national network for environmental radioactivity monitoring have collaborated with the Greek Atomic Energy Commission (GAEC) and carried out measurements during the time period between 11 March 2011 and 10 May 2011 and reported their results to GAEC. These laboratories are sited in three Greek cities, Athens, Thessaloniki and Ioannina, covering a large part of the Greek territory. The concentrations of the radionuclides were studied as a function of time. The first indication for the arrival of the radionuclides in Greece originating from Fukushima accident took place on 24 March 2011. After 28 April 2011', concentrations of all the radionuclides were below the minimum detectable activities (<10 µBq m(-3) for (131)I). The range of concentration values in aerosol particles was 10-520 µBq m(-3) for (131)I, 10-200 µBq m(-3) for (134)Cs and 10-200 µBq m(-3) for (137)Cs and was 10-2200 µBq m(-3) for (131)I in gaseous phase. The ratios of (131)I/(137)Cs and (134)Cs/(137)Cs concentrations are also presented. For (131)I, the maximum concentration detected in grass was 2.2 Bq kg(-1). In the case of sheep milk, the maximum concentration detected for (131)I was 2 Bq l(-1). Furthermore, more than 200 samples of imported foodstuff have been measured in Greece, following the EC directives on the inspection of food and feeding stuffs.

Data evaluation of laminar flow diffusion chamber nucleation experiments with different computational methods.

In order to evaluate the experimental data from laminar flow diffusion chamber (LFDC) experiments on homogeneous nucleation, an extensive postmeasurement computational analysis is required. The present work investigates the influence of the used computational methodology on the derived nucleation curves. To this end a reanalysis is made of previous LFDC experiments of 1-butanol nucleation in helium [D. Brus et al., J. Chem. Phys. 122, 214506 (2005)] using two different methods. The first method is based on single fluid heat and vapor transport in the carrier gas ignoring the aerosol processes, as commonly made in LFDC data evaluations. The second method is more comprehensive as is based on multidimensional computational fluid-particle dynamics. The calculations are made under the usual simplification of one-way coupling between fluid flow and particles, which is a valid approximation in most practical aerosols, while full aerosol dynamical effects are accommodated. Similar results were produced by the two methods. This finding corroborates the usual practice of omitting aerosol calculations in LFDC experimental data evaluation.

Lung deposition of fine and ultrafine particles outdoors and indoors during a cooking event and a no activity period.

UNLABELLED: Some indoor activities increase the number concentration of small particles and, hence, enhance the dose delivered to the lungs. The received particle dose indoors may exceed noticeably the dose from ambient air under routine in-house activities like cooking. In the present work, the internal dose by inhalation of ultrafine and fine particles is assessed, using an appropriate mechanistic model of lung deposition, accommodating aerosol, and inhalation dynamics. The analysis is based on size distribution measurements (10-350 nm) of indoor and outdoor aerosol number concentrations in a typical residence in Athens, Greece. Four different cases are examined, namely, a cooking event, a no activity period indoors and the equivalent time periods outdoors. When the cooking event (frying of bacon-eggs with a gas fire) occurred, the amount of deposited particles deep into the lung of an individual indoors exceeded by up to 10 times the amount received by an individual at the same time period outdoors. The fine particle deposition depends on the level of physical exertion and the hygroscopic properties of the inhaled aerosol. The dose is not found linearly dependant on the indoor/outdoor concentrations during the cooking event, whereas it is during the no activity period. PRACTICAL IMPLICATIONS: The necessity for determining the dose in specific regions of the human lung, as well as the non-linear relationship between aerosol concentration and internal dose makes the application of dosimetry models important. Lung dose of fine and ultrafine particles, during a cooking event, is compared with the dose at no indoor activity and the dose received under outdoor exposure conditions. The dose is expressed in terms of number or surface of deposited particles. This permits to address the dosimetry of very small particles, which are released by many indoor sources but represent a slight fraction of the particulate matter mass. The enhancement of the internal dose resulting from fine and ultrafine particles generated during the cooking event vs. the dose when no indoor source is active is assessed. The results for those cases are also compared with the dose calculated for the measured aerosol outdoors.

Modeling of the dispersion of depleted uranium aerosol.

Depleted uranium is a low-cost radioactive material that, in addition to other applications, is used by the military in kinetic energy weapons against armored vehicles. During the Gulf and Balkan conflicts concern has been raised about the potential health hazards arising from the toxic and radioactive material released. The aerosol produced during impact and combustion of depleted uranium munitions can potentially contaminate wide areas around the impact sites or can be inhaled by civilians and military personnel. Attempts to estimate the extent and magnitude of the dispersion were until now performed by complex modeling tools employing unclear assumptions and input parameters of high uncertainty. An analytical puff model accommodating diffusion with simultaneous deposition is developed, which can provide a reasonable estimation of the dispersion of the released depleted uranium aerosol. Furthermore, the period of the exposure for a given point downwind from the release can be estimated (as opposed to when using a plume model). The main result is that the depleted uranium mass is deposited very close to the release point. The deposition flux at a couple of kilometers from the release point is more than one order of magnitude lower than the one a few meters near the release point. The effects due to uncertainties in the key input variables are addressed. The most influential parameters are found to be atmospheric stability, height of release, and wind speed, whereas aerosol size distribution is less significant. The output from the analytical model developed was tested against the numerical model RPM-AERO. Results display satisfactory agreement between the two models.