An episode of Ru-106 in air over Europe, September-October 2017 - Geographical distribution of inhalation dose over Europe.

Between the end of September and early October 2017, 106Ru was recorded by air monitoring stations across parts of Europe. In the environment, this purely anthropogenic radionuclide can be detected very rarely only. As far as known, 106Ru is only used in radiotherapy and possibly in radiothermal generators. Therefore, the episode drew considerable interest in the monitoring community, although the activity concentrations and resulting exposure were far below radiological concern. Health consequences can be practically excluded except possibly near the source. 106Ru in aerosols could be detected for several weeks and in some regions of Central and Eastern Europe tens, up to over 100 mBq/m³ were measured as one-day means. Discussions about a possible source continue until today (early 2019). Atmospheric back-modelling led to trajectories likely originating in the Southern to Northern Ural region of Russia and possibly Northern Kazakhstan. Suspiciously, no other anthropogenic radionuclides have been observed alongside, except minute concentrations of comparatively short-lived 103Ru (half life 39 d vs. 376 d for 106Ru). Due to the absence of other anthropogenic radionuclides, a reactor accident can be excluded, although both Ru isotopes are fission products generated in nuclear reactors. The exposure resulting from 106Ru activity concentration in air exceeded 200 mBq × d/m³ in some parts of Central and Eastern Europe. This leads to inhalation doses of up to about 0.3 µSv regionally, assuming the radiologically most efficient speciation, lacking better information, and inhalation dose conversion factors from ICRP 119. We show an interpolated map of the dose distribution over parts of Europe where sufficient measurements are available to us. Overlaying population density, we give an estimate of collective dose. The opportunity is also used to give a short review of origin, properties and use of 106Ru, as well as of accidents which involved release of this radionuclide.

Estimating the terrestrial gamma dose rate by decomposition of the ambient dose equivalent rate.

An extensive network of dose rate monitoring stations continuously measures ambient dose rate across Europe, as part of the EURDEP system. Its purpose is early warning in radiological emergencies and documenting its temporal and spatial evolution. In normal conditions, when there is no contribution to the dose rate signal coming from fresh anthropogenic contamination, the data represent the radiation "background", i.e. the combined natural radiation and existing anthropogenic contamination (by global and Chernobyl fallout). These data are being stored, but have so far not been evaluated in depth, or used for any purpose. In the framework of the EU project 'European Atlas of Natural Radiation' the idea has emerged to exploit these data for generating a map of natural terrestrial gamma radiation. This component contributes to the total radiation exposure and knowing its geographical distribution can help establishing local 'radiation budgets'. A further use could be found in terrestrial dose rate as a proxy of the geogenic radon potential, as both quantities are related by partly the same source, namely uranium content of the ground. In this paper, we describe in detail the composition of the ambient dose equivalent rate as measured by the EURDEP monitors with respect to its physical nature and to its sources in the environment. We propose and compare methods to recover the terrestrial component from the gross signal. This requires detailed knowledge of detector response. We consider the probes used in the Austrian, Belgian and German dose rate networks, which are the respective national networks supplying data to EURDEP. It will be shown that although considerable progress has been made in understanding the dose rate signals, there is still space for improvement in terms of modelling and model parameters. An indispensable condition for success of the endeavour to establish a Europe-wide map of terrestrial dose rate background is progress in harmonising the European dose rate monitoring network.

Status of the European Atlas of Natural Radiation.

According to the EURATOM (European Atomic Energy Community) Treaty, one of the missions of the Joint Research Centre (JRC) of the European Commission (EC) is to collect, process, evaluate and present data on environmental radioactivity. In 2006, the JRC started the 'European Atlas of Natural Radiation' project, in order to give an overview of the geographic distribution of sources of, and exposures to, natural radiation. As a first task, a map of indoor radon concentration was created, because in most cases this is the most important contribution to exposure, and since it could be expected that data collection would take quite some time, because radon (Rn) surveys are very differently advanced between European countries. The authors show the latest status of this map. A technically more ambitious map proved the one of the geogenic Rn potential (RP), due to heterogeneity of data sources across Europe and the need to develop models to estimate a harmonised quantity which adequately measures or classifies the RP. Further maps currently in the making include those of secondary cosmic radiation, of terrestrial gamma radiation and of the concentrations of the elements U, Th and K that are its source. In this article, the authors show the progress of some of these maps.

A climatology of 7Be in surface air in European Union.

This study presents a European-wide analysis of the spatial and temporal distribution of the cosmogenic isotope (7)Be in surface air. This is the first time that a long term database of 34 sampling sites that regularly provide data to the Radioactivity Environmental Monitoring (REM) network, managed by the Joint Research Centre (JRC) in Ispra, is used. While temporal coverage varies between stations, some of them have delivered data more or less continuously from 1984 to 2011. The station locations were considerably heterogeneous, both in terms of latitude and altitude, a range which should ensure a high degree of representativeness of the results. The mean values of (7)Be activity concentration presented a spatial distribution value ranging from 2.0 to 5.4 mBq/m(3) over the European Union. The results of the ANOVA analysis of all (7)Be data available indicated that its temporal and spatial distributions were mainly explained by the location and characteristic of the sampling sites rather than its temporal distribution (yearly, seasonal and monthly). Higher (7)Be concentrations were registered at the middle, compared to high-latitude, regions. However, there was no correlation with altitude, since all stations are sited within the atmospheric boundary layer. In addition, the total and yearly analyses of the data indicated a dynamic range of (7)Be activity for each solar cycle and phase (maximum or minimum), different impact on stations having been observed according to their location. Finally, the results indicated a significant seasonal and monthly variation for (7)Be activity concentration across the European Union, with maximum concentrations occurring in the summer and minimum in the winter, although with differences in the values reached. The knowledge of the horizontal and vertical distribution of this natural radionuclide in the atmosphere is a key parameter for modelling studies of atmospheric processes, which are important phenomena to be taken into account in the case of a nuclear accident.

From the European indoor radon map towards an atlas of natural radiation.

In 2006, the Joint Research Centre of the European Commission launched a project to map radon at the European level, as part of a planned European Atlas of Natural Radiation. It started with a map of indoor radon concentrations. As of May 2014, this map includes data from 24 countries, covering a fair part of Europe. Next, a European map of geogenic radon, intended to show 'what earth delivers' in terms of radon potential (RP), was started in 2008. A first trial map has been created, and a database was established to collect all available data relevant to the RP. The Atlas should eventually display the geographical distribution of physical quantities related to natural radiation. In addition to radon, it will comprise maps of quantities such as cosmic rays and terrestrial gamma radiation. In this paper, the authors present the current state of the radon maps and the Atlas.

The European map of the geogenic radon potential.

As part of its projected European Atlas of Natural Radiation (EANR), the Joint Research Centre (JRC) of the European Commission, in cooperation with research institutions and radioprotection authorities all over Europe, is currently developing a map of the geogenic radon potential. In an accompanying report the state of knowledge, mapping approaches and problems are discussed. We explain the rationale and the legal situation in Europe and present an overview on the main problems stemming from the heterogeneity of input datasets between participating countries and from the definition of input variables and their differently implemented sampling procedures or protocols. Further topics are definition of the target variable which quantifies the geogenic radon potential and its estimation from heterogeneous input and proxy variables, as well as problems specific to mapping, such as choice of mapping support and resolution. The geogenic map was preceded by a European map of indoor radon concentrations, which is still growing as ever more countries decide to participate, and which served as training for harmonisation problems occurring in the European data realm. We shall also briefly discuss its main results and implications for the geogenic map.

Radioactivity from Fukushima Dai-ichi in air over Europe; part 1: spatio-temporal analysis.

Radionuclides emitted from the Fukushima I nuclear power plant have been detected in air all over Europe. Concentrations remained far below levels which could have caused radiological concern: probably the committed thyroid dose due to inhalation remained below about 1 µSv (for 10 y children), within the investigated region. They provided, however, a spatio-temporal signal which could be used to develop and test tools to provide additional information on the large-scale situation (Europe-wide, in this case) during a nuclear emergency. In this part we discuss the spatial distribution of the contaminated air masses over Europe. Using (131)I as an example, we present a method to construct maps of the time-cumulated (131)I concentration in air and of the peak concentrations. Procedures to deal with the statistical limitations of a data set stemming from different monitoring schemes are discussed. As over all results, the mean (over the investigated region) cumulated concentration of particular (131)I is estimated about 9 mBq d/m(3), with observed maximum of about 23 mBq d/m(3). The probability that much higher concentrations occurred at unsampled locations, than have been observed anywhere, is assessed low, e.g. about 2.5% for the cumulated (131)I(part.) concentration to exceed 30 mBq d/m(3). Our method can be used in nuclear emergencies for providing spatial analyses if radionuclide concentrations of health concern are detected by atmospheric monitoring stations. We suggest considering such methods of data harmonization if synoptic assessment based on heterogeneous datasets is attempted.

Radioactivity from Fukushima Dai-ichi in air over Europe; part 2: what can it tell us about the accident?

It is shown which information can be extracted from the monitoring of radionuclides emitted from the Fukushima Dai-ichi nuclear power plant and transported to Europe. In this part the focus will be on the analysis of the concentration ratios. While (131)I, (134)Cs and (137)Cs were reported by most stations, other detected radionuclides, reported by some, are (95)Nb, (129m)Te, (132)Te, (132)I, (136)Cs and (140)La. From their activity ratios a mean burn-up of 26.7 GWd/t of the fuel from which they originated is estimated. Based on these data, inventories of radionuclides present at the time of the accident are calculated. The caesium activity ratios indicate emissions from the core of unit 4 which had been unloaded into the fuel storage pool prior to the accident.

Status of the European indoor radon map.

Since 2006 a European map of indoor radon (Rn) concentration is in the making. So far 20 countries have contributed with national data, allowing a fair coverage of parts of Europe. This paper presents the current (September 2010) state of the map, discusses its rationale, presents some statistical findings and addresses a few problems which arose during the work. It also briefly presents the European Atlas of Natural Radiation project, of which the Rn map will be part, and further, planned maps of environmental natural radioactivity.

First steps towards a European atlas of natural radiation: status of the European indoor radon map.

Within the context of its institutional scientific support to the European Commission, in 2005 the Radioactivity Environmental Monitoring (REM) group at the Joint Research Centre of the European Commission, started to explore the possibility of mapping indoor radon in European houses as a first step towards preparing a European Atlas of Natural Radiations. The main objective of such an atlas is to contribute to familiarizing the public with its naturally radioactive environment. The process of preparing the atlas should also provide the scientific community with a database of information that can be used for further studies and for highlighting regions with elevated levels of natural radiation. This document presents the status of the European indoor radon (Rn) map, first statistical results, and outlines of forthcoming challenges.

Mapping 137Cs deposition: data validation methods and data interpretation.

The "Atlas of caesium deposition on Europe after the Chernobyl accident" was prepared within the framework of the Joint Study Project 6 (JSP6) of the collaborative programme on the consequences of the Chernobyl accident between the European Commission and the Ministries responsible for Chernobyl affairs in Belarus, Russia and Ukraine. The radiological data provided by scientific institutes and competent authorities of more than 30 European countries were integrated into an information platform. Data validation and intercomparison were therefore essential before the interpretation of the deposition with the help of isoline maps prepared with a geographic information system (GIS) could be done. The data validation was a two-step procedure: after performing a primary logical consistency check, other techniques based on spatial statistics were used to outline uncertain data. The purpose of this paper is to present these validation methods and to discuss the advantages and constraints of these techniques. Rather than trying to improve the techniques of spatial data analysis, suggestions are made on how an adaptation of the sampling information could improve the final result.

Multi-fractal nature of radioactivity deposition on soil after the Chernobyl accident.

Fractal analysis is introduced in the field of environmental health physics. In particular, it is applied to the complex and inhomogeneous deposition pattern of radioactivity after the Chernobyl accident. The patchiness of 137Cs hot spots is quantified by a fractal dimension as low as 1. The problem of finding hot spots that might be of health concern is discussed.