Airborne concentrations and chemical considerations of radioactive ruthenium from an undeclared major nuclear release in 2017.

In October 2017, most European countries reported unique atmospheric detections of aerosol-bound radioruthenium (106Ru). The range of concentrations varied from some tenths of µBq·m-3 to more than 150 mBq·m-3 The widespread detection at such considerable (yet innocuous) levels suggested a considerable release. To compare activity reports of airborne 106Ru with different sampling periods, concentrations were reconstructed based on the most probable plume presence duration at each location. Based on airborne concentration spreading and chemical considerations, it is possible to assume that the release occurred in the Southern Urals region (Russian Federation). The 106Ru age was estimated to be about 2 years. It exhibited highly soluble and less soluble fractions in aqueous media, high radiopurity (lack of concomitant radionuclides), and volatility between 700 and 1,000 °C, thus suggesting a release at an advanced stage in the reprocessing of nuclear fuel. The amount and isotopic characteristics of the radioruthenium release may indicate a context with the production of a large 144Ce source for a neutrino experiment.

Potential Source Apportionment and Meteorological Conditions Involved in Airborne 131I Detections in January/February 2017 in Europe.

Traces of particulate radioactive iodine (131I) were detected in the European atmosphere in January/February 2017. Concentrations of this nuclear fission product were very low, ranging 0.1 to 10 µBq m-3 except at one location in western Russia where they reached up to several mBq m-3. Detections have been reported continuously over an 8-week period by about 30 monitoring stations. We examine possible emission source apportionments and rank them considering their expected contribution in terms of orders of magnitude from typical routine releases: radiopharmaceutical production units > sewage sludge incinerators > nuclear power plants > spontaneous fission of uranium in soil. Inverse modeling simulations indicate that the widespread detections of 131I resulted from the combination of multiple source releases. Among them, those from radiopharmaceutical production units remain the most likely. One of them is located in Western Russia and its estimated source term complies with authorized limits. Other existing sources related to 131I use (medical purposes or sewage sludge incineration) can explain detections on a rather local scale. As an enhancing factor, the prevailing wintertime meteorological situations marked by strong temperature inversions led to poor dispersion conditions that resulted in higher concentrations exceeding usual detection limits in use within the informal Ring of Five (Ro5) monitoring network.

A COMPARISON OF RADON INDOOR MEASUREMENTS WITH INTERPOLATED RADON SOIL GAS VALUES USING THE INVERSE WEIGHTING METHOD ON MEASURED RESULTS.

The European Basic Safety Standards demand the prediction of areas where a significant number of households exceed the reference level for the radon activity concentration. Therefore, radon maps are established which are based on indoor and soil gas measurements. In this study results of soil gas measurements are interpolated to get a value for the radon activity concentration in the soil gas at the coordinates of an indoor measurement and enable a direct comparison of both results. For the interpolation the inverse weighting value is applied. This way a prediction of the indoor radon activity concentration at the location of indoor measurements is attempted for verification. Quotients between the radon activity concentration in soil gas and indoors are analyzed. Building characteristics are also taken into account to evaluate parameters which lead to the reference level being exceeded. The results assist in the interpretation of soil gas measurements regarding the prediction of indoor radon activity concentrations.

RADON EXPOSURE AT SPECIFIC WORKPLACES IN AUSTRIA-EXPERIENCES AND FUTURE CHALLENGES.

Radon exposure at specific workplaces like water works, radon spas, tourist mines and show caves were evaluated in Austria within pilot studies (2004-10) and have been regulated in an ordinance since 2008. In this article, the major results and experiences in radon measurements and dose assessments at those workplaces by the accredited AGES laboratory are presented.

The uncertainty in the radon hazard classification of areas as a function of the number of measurements.

The administration in many countries demands a classification of areas concerning their radon risk taking into account the requirements of the EU Basic Safety Standards. The wide variation of indoor radon concentrations in an area which is caused by different house construction, different living style and different geological situations introduces large uncertainties for any classification scheme. Therefore, it is of importance to estimate the size of the experimental coefficient of variation (relative standard deviation) of the parameter which is used to classify an area. Besides the time period of measurement it is the number of measurements which strongly influences this uncertainty and it is important to find a compromise between the economic possibilities and the needed confidence level. Some countries do not use pure measurement results for the classification of areas but use derived quantities, usually called radon potential, which should reduce the influence of house construction, living style etc. and should rather represent the geological situation of an area. Here, radon indoor measurements in nearly all homes in three municipalities and its conversion into a radon potential were used to determine the uncertainty of the mean radon potential of an area as a function of the number of investigated homes. It could be shown that the coefficient of variation scales like 1/√n with n the number of measured dwellings. The question how to deal with uncertainties when using a classification scheme for the radon risk is discussed and a general procedure is proposed.

Indoor radon, geogenic radon surrogates and geology - Investigations on their correlation.

The indoor radon concentration was measured in most houses in a couple of municipalities in Austria. At the same time the activity concentration of radium in soil, the soil gas radon concentration, the permeability of the ground and the ambient dose equivalent rate were also measured and the geological situations (geological units) were recorded too. From the indoor radon concentration and different house and living parameters a radon potential (Austrian radon potential) was derived which should represent the radon concentration in a standard room. Another radon potential (Neznal radon potential) was calculated from the soil gas radon concentration and the permeability. The aim of the investigation was to correlate all the different variables and to test if the use of surrogate data (e.g. geological information, ambient dose equivalent rate, etc.) can be used to judge the radon risk for an area without performing numerous indoor measurements.

Radon mapping strategies in Austria.

According to current European and international recommendations (e.g. by IAEA, WHO and European Union), countries shall identify high radon areas. In Austria, this task was initiated already in the early 1990s, which yielded the first Austrian Radon Potential Map. This map is still in use, updated with recent indoor radon data in 2012. The map is based on radon gas measurements in randomly selected dwellings, normalised to a standard situation. To meet the current (legal) requirements, uncertainties in the existing Austrian radon map should be reduced. A new indoor radon survey with a different sampling strategy was started, and possible mapping methods are studied and tested. In this paper, the methodology for the existing map as well as the planned strategies to improve this map is discussed.

Comprehensive investigation of radon exposure in Austrian tourist mines and caves.

According to Austrian Law, dose assessments in workplaces with potentially enhanced radon exposures are mandatory since 2008, including tourist mines and caves. A pilot study was carried out to evaluate the situation to test the measurement methods and to specify the main parameters controlling the radon concentration in tourist mines and caves. Radon was measured in six mines and three caves for 1 y, along with determining thoron and equilibrium factors and taking into account climatic, geological and site-related effects. The radon concentrations have a seasonal dependence with maximum in summer and minimum in winter, related to natural ventilation. Radon concentrations in the karst caves were quite low, as it was in the salt mine, whereas radon concentrations in copper and silver mines were high. The dose assessment of the employees yielded doses above 6 mSv a(-1) only in the copper mine.

National radon programmes and policies: the RADPAR recommendations.

Results from epidemiological studies on lung cancer and radon exposure in dwellings and mines led to a significant revision of recommendations and regulations of international organisations, such as WHO, IAEA, Nordic Countries, European Commission. Within the European project RADPAR, scientists from 18 institutions of 14 European countries worked together for 3 y (2009-12). Among other reports, a comprehensive booklet of recommendations was produced with the aim that they should be useful both for countries with a well-developed radon programme and for countries with little experience on radon issues. In this paper, the main RADPAR recommendations on radon programmes and policies are described and discussed. These recommendations should be very useful in preparing a national action plan, required by the recent Council Directive 2013/59/Euratom.

Monitoring trends in civil engineering and their effect on indoor radon.

In this paper, the importance of monitoring new building concepts is discussed. The effect of energy-efficient construction technologies on indoor radon is presented in more detail. Comparing the radon levels of about 100 low-energy and passive houses in Austria with radon levels in conventional new houses show that, in energy-efficient new houses, the radon level is about one-third lower than in conventional new houses. Nevertheless, certain features or bad practice may cause high radon levels in energy-efficient new houses. Recommendations to avoid adverse effects were set up. Furthermore, the paper deals with the effect of thermal retrofitting on indoor radon. Results from a Swiss study where 163 dwellings were measured before and after thermal retrofit yield an increase of the radon level of 26% in average. Among the various retrofit measures, replacing windows has the greatest impact on the indoor radon level.

The Austrian radon activities on the way to the national radon action plan.

Based on the new Euratom Basic Safety Standards (BSS), all EU member states will be obliged to design a strategy to address long-term risks from radon exposure, which is laid down in the 'national radon action plan'. In Austria, the National Radon Centre is responsible for the development of the action plan. This paper presents the current and planned radon protection activities on the way to establish the radon action plan--like the national radon database, the definition of radon risk areas by improving the existing radon map, as well as strategies and activities to increase the radon awareness of the public and decision-makers and to involve the building sector. The impact of and the need for actions caused by the BSS requirements on the Austrian radon legislation, strategy and programme are discussed.

Radon remediation and prevention status in 23 European countries.

Radon remediation and prevention aim at reducing indoor radon concentrations in the existing and new buildings. This paper gives an estimate of the number of dwellings where remediation or preventive measures have been applied so far in Europe. Questionnaires were sent to contact persons in national radiation protection authorities and radon-related research institutes. Answers from 23 European countries were obtained. Approximately 26 000 dwellings have been remediated in total. Millions of dwellings remain to be remediated and the number is increasing due to the rare use of radon prevention. These facts imply a need for an efficient radon strategy to promote radon remediation. Moreover, the importance of radon prevention in new construction and the regulations concerning radon in the national building codes should be emphasised.

Mitigation of three water supplies with high radon exposure to the employees.

A comprehensive survey to determine the occupational radiation exposure in water supplies and spas was conducted in the federal state of Upper Austria. The study comprises 45 water supplies. The limit for radon exposure of 6 MBq h m(-3) was exceeded by two water supplies (WS 33 and WS 42). In one water supply (WS 29), the level of 2 MBq h m(-3) was exceeded. These water supplies were mitigated. Prior to mitigation the main radon sources were identified. Mitigation measures were: evacuation of the outlet air of the vaporiser by means of a fan, installation of a fan in the exhaust air duct of the compensating reservoir, sealing of drain shafts and mechanical ventilation of the office. In all water supplies, the radon exposure was reduced to below 0.8 MBq h m(-3) at a cost of approx. euro 750 to euro 1000.

Intercomparison of sampling and measurement of 7Be in air at four high-altitude locations in Europe.

For several years 7Be measurements have been conducted at high-altitude stations in Austria (Sonnblick, 3106 m), Switzerland (Jungfraujoch, 3580 m), Germany (Zugspitze, 2962 m), and Italy (Mt. Cimone, 2165 m) with the aim to support a study on vertical ozone transport in the Alps (VOTALP project). Aerosol samples, collected on filtering media with high volume samplers, are analysed for 7Be by high-resolution gamma-spectrometry. Prior to evaluation of the 7Be time series of the four stations, both sampling and measurement procedures were checked for comparability. The results of an intercomparison exercise performed within the mentioned project are reported.

Radiocaesium contamination of meadow vegetation--time-dependent variability and influence of soil characteristics at grassland sites in Austria.

Long-term trends of 137Cs and 40K concentrations in meadow grass and soil-plant transfer data at eight different sites in Upper Austria are presented. Geometric means of 137Cs TF-data and Tagg values vary between 0.03-1.06 and 0.0005-0.0184 depending on site, respectively. 40K results are less variable with TF values covering a range of 0.31-2.01. Only at one site was a significant decrease of 137Cs concentration (decay-corrected) in meadow vegetation observed during the observation period 1992-1999. Seasonal trends of 40K and 137Cs were investigated at one site in 1996. Both elements show decreasing concentrations in plants from beginning of May-July, followed by a peak in September. Although this pattern was not very pronounced, there are some hints that it may explain deviations of long-term trends in 137CS levels in grass caused by unusual weather conditions as indicated by phenological climate data (beginning of sweet cherry and black elder blossoming). Finally, TF values were correlated with soil characteristics, revealing a negative correlation of radiocaesium soil-plant transfer with soil pH, exchangeable and extractable fractions of Mg, Ca and Na as well as a positive correlation with exchangeable Al.

Results and conclusions of the Austrian radon mitigation project 'SARAH'.

The Austrian radon mitigation joint research project SARAH (supported by the Austrian Ministry of Economy and the Government of Upper Austria), a 2-year follow-up study of the Austrian National Radon Project (ONRAP), was started in 1996. The objectives of the research project were to find simple, cost-effective experimental methods for the characterisation of the radon situation in dwellings and to evaluate technically and economically the implementation of state of the art remedial actions for Austrian house types. After an intercomparison exercise of the assigned radon measuring instruments and detectors five houses were closely examined in regions with elevated radon levels in the federal state of Upper Austria. In this research work for the first time an extended Blower-Door method (which is conventionally used for determining the tightness of buildings) was successfully applied to radon diagnosis of buildings. In this paper the methods used for the radon diagnosis, the applied mitigation measures and the related technical and economical aspects are discussed. In conclusion of the results of this project a common strategy for solving the radon problem in Austria in the future is presented briefly.