Trends, events and potential sources of Xe-detections in the German radioxenon network.

The measurement of radioxenons (133Xe, 131mXe, 133mXe, 135Xe) in the atmosphere is a keystone for the verification of the Comprehensive Nuclear-Test-Ban Treaty (CTBT). At the German Federal Office for Radiation Protection (Bundesamt für Strahlenschutz, BfS) activity concentrations of radioactive noble gases at several sites in Germany have been measured for more than 5 decades, initially to monitor nuclear facilities and since the mid-1990s also to support the development of measurement and monitoring systems and procedures for verification of the CTBT. Average 133Xe activity concentration in air measured daily at station RN33 of the International Monitoring System (IMS) of the CTBTO on Mt Schauinsland has decreased since 2008. Due to the decreasing radioxenon background in the atmosphere, laboratory measurements with less sensitive proportional counters developed in-house are increasingly replaced by an isotope specific ß-γ laboratory system for radioxenon analyses. Six years of radioxenon activity concentrations measured with the ß-γ laboratory system in weekly samples from monitoring sites in Germany are presented. Activity concentrations of 133Xe in southern Germany are now typically below 1 mBq m-3 and have decreased by an order of magnitude in the past 25 years. Magnitude and variability of 133Xe activity concentrations are generally larger in northern and western Germany compared to the south, most likely due to the prevailing wind directions in the region. Selected, but typical, periods of elevated radioxenon levels at the stations are investigated and the value of stack emission data is demonstrated.

Evaluating 5 decades of atmospheric 85Kr measurements in the southern hemisphere to derive an input function for dating water and ice with implications for interhemispheric circulation and the global 85Kr emission inventory.

In July 2015, the currently only active monitoring station for atmospheric 85Kr measurements in the southern hemisphere went operational at the Commonwealth Scientific and Industrial Research Organization (CSIRO) in Adelaide, Australia. Here, this new data is presented and combined with measurements from historic monitoring stations, to generate a85Kr input function for the southern hemisphere which is crucial for the application of 85Kr as a dating tracer for water and ice. After a linear increase in atmospheric 85Kr concentrations between 1980 and 2005, concentrations stabilized yielding mean 85Kr activity concentration during the Adelaide monitoring period of 1.3 ± 0.15 Bq/m³ air with slight variations indicating seasonal effects. Data from three northern hemispheric monitoring stations Schauinsland, Freiburg and Jungfraujoch of the German Federal Office for Radiation Protection (BfS), located in Central Europe are used to calculate an interhemispheric exchange time of 1.25 ± 0.24 years, using a simple box model approach. Furthermore, it is investigated whether a southern hemispheric 85Kr input function can be calculated from the baseline of the northern hemispheric data set. A comparison between the calculated and the fitted input function shows that analytical techniques can just resolve the concentration differences, emphasising the need of southern hemispheric monitoring stations for 85Kr. Analysing the decay-corrected input function and taking the current detection limit of low-level counting and Atom Trap Trace Analysis of 0.05 Bq/m³ air, a maximum apparent 85Kr tracer age of 40 years can be determined in the southern hemisphere. Finally, the 85Kr measurements are used to derive global 85Kr emission rates which are found to be in good agreement with published emissions from nuclear reprocessing plants.

Analysis of radioxenon and Krypton-85 at the BfS noble gas laboratory.

Proportional counters and a ß-γ coincidence system and their performance characteristics are described, with emphasis on internal and external quality controls. Typical limits of detection (LD) are 8mBqm-3 for 85Kr and 4mBqm-3 for 133Xe for the proportional counters, while for similar xenon volumes the LD for 133Xe in the ß-γ system is approximately 4 times lower. Results of comparative analyses agree above the limit of quantification. Xenon-133 levels in southern Germany are presently at or below the LD of the proportional counters, but above the LD of the ß-γ system, which is now routinely used for analysis of environmental samples.

The IUR Forum: Worldwide Harmonisation of Networks to Support Integration of Scientific Knowledge and Consensus Development in Radioecology.

During the past decades, many specialised networks have formed to meet specific radioecological objectives, whether regional or sectorial (purpose-oriented). Regional networks deal with an array of radioecological issues related to their territories. Examples include the South Pacific network of radioecologists, and the European network of excellence in radioecology. The latter is now part of the European platform for radiation protection. Sectorial networks are more problem-oriented, often with wider international representativeness, but restricted to one specific issue, (e.g. radioactive waste, low-level atmospheric contamination, modelling). All such networks, while often working in relative isolation, contribute to a flow of scientific information which, through United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR's) efforts of synthesis, feeds into the radiation protection frameworks of protecting humans and the environment. The IUR has therefore prompted a co-construction process aimed at improving worldwide harmonisation of radioecology networks. An initiative based on an initial set of 15 networks, now called the IUR FORUM, was launched in June 2014. The IUR Forum agreed to build a framework for improved coordination of scientific knowledge, integration and consensus development relative to environmental radioactivity. Three objectives have been collectively assigned to the IUR FORUM: (1) coordination, (2) global integration and construction of consensus and (3) maintenance of expertise. One particular achievement of the FORUM was an improved description and common understanding of the respective roles and functions of the various networks within the overall scene of radioecology R&D. It clarifies how the various networks assembled within the IUR FORUM interface with UNSCEAR and other international regulatory bodies (IAEA, ICRP), and how consensus on the assessment of risk is constructed. All these agencies interact with regional networks covering different geographical areas, and with other networks which address specific topics within radiation protection. After holding its first Consensus Symposium in 2015, examining the possible ecological impact of radiation from environmental contamination, the IUR FORUM continues its work towards improved radiation protection of humans and the environment. We welcome new members.

Predicting exposure of wildlife in radionuclide contaminated wetland ecosystems.

Many wetlands support high biodiversity and are protected sites, but some are contaminated with radionuclides from routine or accidental releases from nuclear facilities. This radiation exposure needs to be assessed to demonstrate radiological protection of the environment. Existing biota dose models cover generic terrestrial, freshwater, and marine ecosystems, not wetlands specifically. This paper, which was produced under IAEA's Environmental Modelling for Radiation Safety (EMRAS) II programme, describes an evaluation of how models can be applied to radionuclide contaminated wetlands. Participants used combinations of aquatic and terrestrial model parameters to assess exposure. Results show the importance of occupancy factor and food source (aquatic or terrestrial) included. The influence of soil saturation conditions on external dose rates is also apparent. In general, terrestrial parameters provided acceptable predictions for wetland organisms. However, occasionally predictions varied by three orders of magnitude between assessors. Possible further developments for biota dose models and research needs are identified.

Variability of atmospheric krypton-85 activity concentrations observed close to the ITCZ in the southern hemisphere.

Krypton-85 activity concentrations in surface air have been measured at Darwin, which is located in northern Australia and is influenced by seasonal monsoonal activity. Measurements between August 2007 and May 2010 covered three wet seasons. The mean activity concentration of krypton-85 measured during this period was 1.31±0.02Bqm(-3). A linear model fitted to the average monthly data, using month and monsoon as predictors, shows that krypton-85 activity concentration measured during the sampling period has declined by 0.01Bqm(-3) per year. Although there is no statistically significant difference in mean activity concentration of krypton-85 between wet and dry season, the model implies that activity concentration is higher by about 0.015Bqm(-3) during months influenced by the monsoon when a north westerly flow prevails. Backward dispersion runs using the Lagrangian particle dispersion model Hysplit4 highlight possible source regions during an active monsoon located deep in the northern hemisphere, and include reprocessing facilities in Japan and India. However, the contribution of these facilities to krypton-85 activity concentrations in Darwin would be less than 0.003Bqm(-3).

The IAEA handbook on radionuclide transfer to wildlife.

An IAEA handbook presenting transfer parameter values for wildlife has recently been produced. Concentration ratios (CRwo-media) between the whole organism (fresh weight) and either soil (dry weight) or water were collated for a range of wildlife groups (classified taxonomically and by feeding strategy) in terrestrial, freshwater, marine and brackish generic ecosystems. The data have been compiled in an on line database, which will continue to be updated in the future providing the basis for subsequent revision of the Wildlife TRS values. An overview of the compilation and analysis, and discussion of the extent and limitations of the data is presented. Example comparisons of the CRwo-media values are given for polonium across all wildlife groups and ecosystems and for molluscs for all radionuclides. The CRwo-media values have also been compared with those currently used in the ERICA Tool which represented the most complete published database for wildlife transfer values prior to this work. The use of CRwo-media values is a pragmatic approach to predicting radionuclide activity concentrations in wildlife and is similar to that used for screening assessments for the human food chain. The CRwo-media values are most suitable for a screening application where there are several conservative assumptions built into the models which will, to varying extents, compensate for the variable data quality and quantity, and associated uncertainty.

Establishing a database of radionuclide transfer parameters for freshwater wildlife.

Environmental assessments to evaluate potentials risks to humans and wildlife often involve modelling to predict contaminant exposure through key pathways. Such models require input of parameter values, including concentration ratios, to estimate contaminant concentrations in biota based on measurements or estimates of concentrations in environmental media, such as water. Due to the diversity of species and the range in physicochemical conditions in natural ecosystems, concentration ratios can vary by orders of magnitude, even within similar species. Therefore, to improve model input parameter values for application in aquatic systems, freshwater concentration ratios were collated or calculated from national grey literature, Russian language publications, and refereed papers. Collated data were then input into an international database that is being established by the International Atomic Energy Agency. The freshwater database enables entry of information for all radionuclides listed in ICRP (1983), in addition to the corresponding stable elements, and comprises a total of more than 16,500 concentration ratio (CRwo-water) values. Although data were available for all broad wildlife groups (with the exception of birds), data were sparse for many organism types. For example, zooplankton, crustaceans, insects and insect larvae, amphibians, and mammals, for which there were CRwo-water values for less than eight elements. Coverage was most comprehensive for fish, vascular plants, and molluscs. To our knowledge, the freshwater database that has now been established represents the most comprehensive set of CRwo-water values for freshwater species currently available for use in radiological environmental assessments.

The new IAEA reference material: IAEA-434 technologically enhanced naturally occurring radioactive materials (TENORM) in phosphogypsum.

A reliable determination of Technologically Enhanced Naturally Occurring Radioactive Materials in phosphogypsum is necessary to comply with radiation protection and environmental regulations. In this respect, a new phosphogypsum reference material was produced and certified to assist in the validation of analytical methods and the quality assurance of produced analytical results. This paper presents the sample preparation methodology, material homogeneity assessment, characterization campaign results and assignment of property values, and associated uncertainties. The reference values and associated uncertainties for Pb-210, Ra-226, Th-230, U-234 and U-238 were established based on consensus values calculated from analytical results reported by three National Metrology Institutes and five expert laboratories.

A study of radionuclides, metals and stable lead isotope ratios in sediments and soils in the vicinity of natural U-mineralisation areas in the Northern Territory.

Australian guidelines recommend that tailings materials from uranium (U) mining and milling be contained without any detrimental impact on the environment for at least 1000 years. Natural analogue sites are being investigated to determine if they can provide data on the rates of natural erosion processes which occur over these timescales, for input into predictive geomorphic computer models. This paper presents radionuclide, metal and stable lead (Pb) isotope data from sediment cores and surface soils in the vicinity of two mineralised areas in the Alligator Rivers Region. Surface scrapes from the natural Anomaly #2, south of the Ranger mineral lease, exhibit radiogenic (206)Pb/(207)Pb and (208)Pb/(207)Pb ratios, and elevated U and metal concentrations typical for a near surface U anomaly. In contrast, samples taken from the Koongarra mineral lease (KML) show radionuclide activity and metal concentrations similar to natural areas elsewhere in the Alligator Rivers Region and Pb isotope ratios are closer to present day average crustal ratios (PDAC), as the orebodies at KML are covered by surficial sand. A sediment core collected from Anbangbang Billabong, downstream of KML, exhibits small variations in Pb isotope ratios that indicate that approximately 1% of the upper sediments in the sediment core may be derived from material originating from the U anomaly at Koongarra.

Airborne gamma survey of the historic Sleisbeck mine area in the Northern Territory, Australia, and its use for site rehabilitation planning.

An airborne gamma-survey provided information about the extent of radioactive contamination around the historic Sleisbeck mine. Quickbird satellite data were acquired to relate airborne measurements to land cover features. Enhanced equivalent uranium (eU) levels were found to be confined to the mine and low grade waste rock dumps. The average terrestrial background radiation dose rate estimated from the airborne gamma survey data was 0.10-0.14 microGy h(-1) while the area around the mine exhibited a maximum of approximately 2.3 microGy h(-1), but measurements on the ground indicate that this maximum is exceeded in some localized areas. Rehabilitation of the site is likely to result in a threefold reduction in radiation doses to people accessing the area.

Radioactive and radiogenic isotopes in sediments from Cooper Creek, Western Arnhem Land.

Protection of the environment post-mining is a key objective of rehabilitation, especially where runoff and erosion from rehabilitated mine sites could potentially lead to contamination of the surrounding land and watercourses. As part of an overall assessment of the success of rehabilitation at the former Nabarlek uranium (U) mine, an appraisal of stable lead (Pb) isotopes, radionuclides and trace metals within sediments and soils was conducted to determine the off site impacts from a spatial and temporal perspective. The study found localised areas on and adjacent to the site where soils had elevated levels of trace metals and radionuclides. Lead isotope ratios are highly radiogenic in some samples, indicating the presence of U-rich material. There is some indication that erosion products with more radiogenic Pb isotope ratios have deposited in sediments downstream of the former ore body. However, there is no indication that the radiogenic erosion products found on the mine site at present have significantly contaminated sediments further downstream of Cooper Creek.

A methodology for the assessment of rehabilitation success of post mining landscapes--sediment and radionuclide transport at the former Nabarlek uranium mine, Northern Territory, Australia.

Protection of the environment post-mining is an important issue, especially where runoff and erosion can lead to undesirable material leaving post-mining landscapes and contaminating surrounding land and watercourses. Methods for assessment of the environmental impact and long-term behaviour of post-mining landforms based on scientific methodology are needed especially where field data are absent or poor. An appraisal of the former Nabarlek uranium mine was conducted to assess the site from a soil erosion perspective as part of an independent evaluation of overall rehabilitation success. Determination of the gross erosion occurring, sediment discharge to Cooper Creek and the resultant sediment associated radionuclide load in Cooper Creek were the primary objectives of the study. These objectives were achieved through the application of several models using parameter values collected from the site. The study found that the area containing the mill tailings repository is extremely stable and meets the guidelines established for long-term storage of uranium mill tailings. Most other areas on the site are stable; however there are some areas with a high sediment loss. Sediment concentration in Cooper Creek, which drains the site, was found to be within the Australian water quality guidelines for fresh water, however sediment concentrations in tributaries were found to exceed recommended levels. Radionuclide determinations on soil samples showed that the highest specific activities (Bq kg-1) were present on a small (0.44 ha) area with a relatively high erosion rate. This small area contributed the majority of the estimated flux to Cooper Creek of uranium-series radionuclides sorbed or structurally incorporated to eroded soil particles sourced from the mine site. This study provides a methodology for assessment of the erosional stability of such a landscape and consequent impact on water quality, using extensive field data and readily available and well known models and methodologies.

A radon and meteorological measurement network for the Alligator Rivers Region, Australia.

The network described in this paper has been set up to provide detailed time-series data on concentrations of 222Rn in air at various locations within the Alligator Rivers Region, over a time frame of several years. These data will be important in assessing the effects of uranium mining operations on radon levels in the region, both in providing baseline and monitoring data and in calibrating and verifying predictive models. At present, three stations are operating in the region with a fourth being commissioned. Each station logs half hourly average radon concentrations and relevant meteorological data (wind speed, direction and variability, air pressure and temperature, relative humidity, soil temperature, rain and sunshine rates). It is intended to operate the four stations at selected locations for one- or two-year intervals, at the end of which three will be moved to new locations (one station at Mudginberri will be kept as a constant control station). Sites for which extensive datasets are currently available include: Jabiru Town, Jabiru East, Djarr Djarr, East Alligator Ranger Station and Nabarlek minesite. Illustrative data from these sites are presented.

Tracing the origin of pollution in French Alpine snow and aerosols using lead isotopic ratios.

Fresh snow samples collected at 15 remote locations and aerosols collected at one location in the French Alps between November 1998 and April 1999 have been analyzed for Pb concentration and isotopic composition by thermal ionization mass spectrometry. The snow samples contained 19-1300 pg/g of Pb with isotopic ratios 206Pb/207Pb (208Pb/207Pb) of 1.1279-1.1607 (2.3983-2.4302). Airborne Pb concentrations at one sampling site ranged from 0.42 to 6.0 ng/m3 with isotopic ratios of 1.1321-1.1427 (2.4029-2.4160). Air mass trajectory analysis combined with isotopic compositions of potential source regions did not show discernible evidence of the long-range atmospheric transport of pollutants. Isotopic ratios in the Alpine snow samples and thus the free troposphere were generally higher than airborne Pb isotopic ratios in urban France, which coupled with the relatively high Pb concentrations suggested a regional anthropogenic Pb source, probably Italy but possibly Eastern Europe.