Peter Bossew

Distribution of radiocaesium in an Austrian forest stand

Within an Austrian spruce stand, vertical distribution of radiocaesium in soil as well as 137Cs concentration in different forest ecosystem compartments including spruce and surface water were investigated 10 years after the Chernobyl accident. The total 137Cs inventory in the forest was estimated to be 46 kBq m-2 (ref. date: 86-05-01). From the collected data annual input rates via litterfall of 0.48% per year and output rates through waterflows of only 0.02% per year were derived. The results identify the high importance of forest soils as a sink for radiocaesium. The estimated ecological residence half-times turned out to be highest in the organic soil horizons (1-3 years per cm), whereas in mineral horizons the values decrease significantly. As a consequence, soil inventory represents more than 95% of the total, whereas only approximately 3.3% of the 137Cs inventory is stored in the living biomass of spruce trees and a further 0.5% in the phytomass of understorey vegetation.

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.

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.

Vertical migration of radionuclides in undisturbed grassland soils.

Literature data on numerical values obtained for the parameters of the two most popular models for simulating the migration of radionuclides in undisturbed soils have been compiled and evaluated statistically. Due to restrictions on the applicability of compartmental models, the convection-dispersion equation and its parameter values should be preferred. For radiocaesium, recommended values are derived for its effective convection velocity and dispersion coefficient. Data deficiencies still exist for radionuclides other than caesium and for soils of non-temperate environments.

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.

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.

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.

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.

Vertical distribution of 238Pu, 239(40)Pu, 241Am, 90Sr and 137Cs in Austrian soil profiles

Abstract The occurrence of 238Pu, 239(40)Pu, 241Am, 90Sr and 137Cs in the region of Nassfeld (Salzburg, Austria) is discussed at four different locations by evaluating a depth profile for each radionuclide. Furthermore, the plutonium separated from the soil samples was measured by Accelerator Mass Spectrometry (AMS) to get information on the isotope ratio 240Pu/ 239Pu. The radiochemical procedure consisted of a Pu separation step from Am and Sr by anion exchange in 8 M HNO3 after oxidation state adjustment to Pu(IV). Am and Sr were coprecipitated with calcium oxalate. Am was separated from Sr by extraction chromatography using TRU-resin. The Sr separation was performed also by extraction chromatography using Sr-resin; after coprecipitation as oxalate, 90Sr was measured in a gas proportional counter. For the determination of 239(40)Pu and 241Am by α-spectrometry thin sources were prepared by microprecipitation with NdF3. With the respective Pu isotope ratios, it was possible to identify the global fallout as source of the contamination. This was confirmed by the ratio 241Am/239(40)Pu. From the activity ratio 90Sr/ 137Cs, it could be shown that most of these radionuclides stem from the reactor accident in Chernobyl.

Dose estimation derived from the exposure to radon, thoron and their progeny in the indoor environment

The annual exposure to indoor radon, thoron and their progeny imparts a major contribution to inhalation doses received by the public. In this study, we report results of time integrated passive measurements of indoor radon, thoron and their progeny concentrations that were carried out in Garhwal Himalaya with the aim of investigating significant health risk to the dwellers in the region. The measurements were performed using recently developed LR-115 detector based techniques. The experimentally determined values of radon, thoron and their progeny concentrations were used to estimate total annual inhalation dose and annual effective doses. The equilibrium factors for radon and thoron were also determined from the observed data. The estimated value of total annual inhalation dose was found to be 1.8 ± 0.7 mSv/y. The estimated values of the annual effective dose were found to be 1.2 ± 0.5 mSv/y and 0.5 ± 0.3 mSv/y, respectively. The estimated values of radiation doses suggest no important health risk due to exposure of radon, thoron and progeny in the study area. The contribution of indoor thoron and its progeny to total inhalation dose ranges between 13–52% with mean value of 30%. Thus thoron cannot be neglected when assessing radiation doses.