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International audience; From early April 2020, wildfires raged in the highly contaminated areas around the Chernobyl nuclear power plant (CNPP), Ukraine. For about 4 weeks, the fires spread around and into the Chernobyl exclusion zone (CEZ) and came within a few kilometers of both the CNPP and radioactive waste storage facilities. Wildfires occurred on several occasions throughout the month of April. They were extinguished, but weather conditions and the spread of fires by airborne embers and smoldering fires led to new fires starting at different locations of the CEZ. The forest fires were only completely under control at the beginning of May, thanks to the tireless and incessant work of the firefighters and a period of sustained precipitation. In total, 0.7–1.2 TBq 137Cs were released into the atmosphere. Smoke plumes partly spread south and west and contributed to the detection of airborne 137Cs over the Ukrainian territory and as far away as Western Europe. The increase in airborne 137Cs ranged from several hundred μBq·m–3 in northern Ukraine to trace levels of a few μBq·m–3 or even within the usual background level in other European countries. Dispersion modeling determined the plume arrival time and was helpful in the assessment of the possible increase in airborne 137Cs concentrations in Europe. Detections of airborne 90Sr (emission estimate 345–612 GBq) and Pu (up to 75 GBq, mostly 241Pu) were reported from the CEZ. Americium-241 represented only 1.4% of the total source term corresponding to the studied anthropogenic radionuclides but would have contributed up to 80% of the inhalation dose.

International audience; 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. © 2018 American Chemical Society.

Significance A massive atmospheric release of radioactive 106Ru occurred in Eurasia in 2017, which must have been caused by a sizeable, yet undeclared nuclear accident. This work presents the most compelling monitoring dataset of this release, comprising 1,100 atmospheric and 200 deposition data points from the Eurasian region. The data suggest a release from a nuclear reprocessing facility located in the Southern Urals, possibly from the Mayak nuclear complex. A release from a crashed satellite as well as a release on Romanian territory (despite high activity concentrations) can be excluded. The model age of the radioruthenium supports the hypothesis that fuel was reprocessed ≤2 years after discharge, possibly for the production of a high-specific activity 144Ce source for a neutrino experiment in Italy., 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.

This paper reports evidence of Pu isotopes in the lower part of the troposphere of Central Europe. The data were obtained based on atmospheric aerosol fraction samples collected from four places in three countries (participating in the informal European network known as the Ring of Five (Ro5)) forming a cell with a surface area of about 200,000km(2). We compared our original data sets from Krakow (Poland, 1990-2007) and Bialystok (Poland, 1991-2007) with the results from two other locations, Prague (Czech Republic; 1997-2004) and Braunschweig (Germany; 1990-2003) to find time evolution of the Pu isotopes. The levels of the activity concentration for (238)Pu and for ((239+240))Pu were estimated to be a few and some tens of nBqm(-3), respectively. However, we also noted some results were much higher (even about 70 times higher) than the average concentration of (238)Pu in the atmosphere. The achieved complex data sets were used to test a new approach to the problem of solving mixing isotopic traces from various sources (here up to three) in one sample. Results of our model, supported by mesoscale atmospheric circulation parameters, suggest that Pu from nuclear weapon accidents or tests and nuclear burnt-up fuel are present in the air.

Traces of particulate radioactive iodine (

Введение: С 1980 года в Польше проводятся систематические исследования естественной радиоактивности сырья и строительных материалов. На основании результатов этих исследований, проводимых как Центральной лабораторией радиологической защиты (CLOR), так и более 30 другими научно-исследовательскими лабораториями в нашей стране была создана общенациональная база данных измерений естественной радиоактивности. Эта база данных находится под контролем CLOR и содержит результаты измерений более 42 000 образцов, проанализированных с 1980 по настоящее время. В связи с экономическим развитием страны с 1990 года наблюдается увеличение числа измерений естественной радиоактивности сырья и строительных материалов. Цель: Цель данной статьи состоит в представлении и оценке выбранного сырья и строительных материалов с точки зрения их радиологических свойств. Метод: В Польше использование различных сырьевых материалов и готовых строительных материалов классифицируется относительно значений показателей активности f1 и f2. Показатель активности f1 определяет содержание природных изотопов в исследуемом материале и является фактором опасного воздействия гамма-излучения на целое тело). Показатель активности f2 определяет содержание радия 226Ra в исследуемом материале и является показателем опасного воздействия на альвеолы легких, вызванного альфаизлучением, эмитированного продуктами распада радия, которые поступают вместе с воздухом в дыхательную систему человека. Показатели активности описываются естественной радиоактивностью калия 40K, радия 226Ra и тория 228Th. Концентрация активности этих радионуклидов определяется при помощи анализатора MAZAR со сцинтилляционным детектором. Анализатор работает в трех диапазонах и измеряет образцы для значений от 1,26 до 1,65 MeV, от 1,65 до 2,30 MeV и от 2,30 до 2,85 MeV. Результаты: В статье представлены показатели активности f1 и f2 для выбранного сырья и строительных материалов, таких как зола, бетон, цемент и керамика. Кроме того, в статье обсуждались показатели активности f1 и f2 угля. Уголь, который являлся предшественником некоторых строительных материалов (золы, шлака, смеси золы и шлака), измеряли достаточно часто начиная с 1996 года. Среднее значение показателя активности f1 колебалось от 0,15 до 0,43, в то время, как средний показатель f2 составял 14,7 Бк/кг до 44,2 Бк/кг для результатов, полученных в 1980-2012 годах. Средние значения показателей активности f1 и f2 угля являются самыми низкими из всех измеренных и сравниваемых материалов, описанных в этой статье. Среднее значение активности f1 золы в качестве побочного продукта от сжигания угля в несколько раз выше, чем угля, и выше, чем предельное значение 1,0 для результатов, собранных за все годы исследований. Выводы: В статье представлено среднее значение и диапазон мощности дозы для нескольких типов сырья и строительных материалов. Средняя мощность дозы колеблется от 31,8 нГр/ч в случае угля, и до 140,8 нГр/ч для золы.Introduction: The systematic research of the natural radioactivity of raw and building materials has been conducted in Poland since 1980. Basing on the results of these studies, carried out by both the Central Laboratory for Radiological Protection (CLOR) and over 30 other research laboratories in our country, the national database of natural radioactivity measurements has been set up. The database is supervised by the CLOR and contains the results of the measurements for more than 42 000 samples analysed since 1980 up till now. Due to the economic development of the country, since 1990 there has been an increase in the number of the natural radioactivity measurements of raw and building materials. Objective: The aim of this article is the presentation and evaluation selected of raw and building materials in terms of radiology. Method: In Poland the possibility of using different raw and ready building materials is classified due to the value of activity coefficients f1 and f2. Activity coefficient f1 specifies the content of natural isotopes in a test material and is the coefficient of the gamma radiation exposure to the whole body. Activity coefficient f2 specifies the content of radium 226Ra (mother of isotope 222Rn) in the test material and is the coefficient of the exposure of the lungs epithelium to the alpha radiation emitted by the decay products of radon, breathed into with air by the human respiratory system. Activity coefficients are described by the natural radioactivity of potassium 40K, radium 226Ra and thorium 228Th. Activity concentration of these radionuclides is determined by the MAZAR analyser with a scintillation detector. It is a three-window analyser, which measures samples in the range from 1.26 MeV to 2.85 MeV. Results: This paper shows the values of activity coefficients f1 and f2 for a few selected raw and building materials like ash, concrete, cement and ceramics. Additionally, activity coefficients f1 and f2 for carbon are discussed. Carbon, as a precursor to a few building raws, (ash, slag, mixture of ash and slag) has been measured in significant amounts since 1996. Average value of its activity coefficient f1 was between 0.15 and 0.43 while an average index f2 was from 14.7 Bq/kg to 44.2 Bq/kg for results collected in 1980-2012. Average values of activity coefficients f1 and f2 for carbon are the lowest of all measured and compared materials described in this paper. Average value of activity coefficient f1 of ash as a by-product of coal combustion is a few times higher than for carbon and is higher than the limit value equals 1.0 for results from almost all years. Conclusions: In the paper, average value and range of dose rate for these several raw and building materials have been shown. An average dose rate is between 31.8 nGy/h for carbon up to 140.8 nGy/h for ash.

Radioactive emissions into the atmosphere from the damaged reactors of the Fukushima Dai-ichi nuclear power plant (NPP) started on March 12th, 2011. Among the various radionuclides released, iodine-131 ( 131I) and cesium isotopes ( 137Cs and 134Cs) were transported across the Pacific toward the North American continent and reached Europe despite dispersion and washout along the route of the contaminated air masses. In Europe, the first signs of the releases were detected 7 days later while the first peak of activity level was observed between March 28th and March 30th. Time variations over a 20-day period and spatial variations across more than 150 sampling locations in Europe made it possible to characterize the contaminated air masses. After the Chernobyl accident, only a few measurements of the gaseous 131I fraction were conducted compared to the number of measurements for the particulate fraction. Several studies had already pointed out the importance of the gaseous 131I and the large underestimation of the total 131I airborne activity level, and subsequent calculations of inhalation dose, if neglected. The measurements made across Europe following the releases from the Fukushima NPP reactors have provided a significant amount of new data on the ratio of the gaseous 131I fraction to total 131I, both on a spatial scale and its temporal variation. It can be pointed out that during the Fukushima event, the 134Cs to 137Cs ratio proved to be different from that observed after the Chernobyl accident. The data set provided in this paper is the most comprehensive survey of the main relevant airborne radionuclides from the Fukushima reactors, measured across Europe. A rough estimate of the total 131I inventory that has passed over Europe during this period was \textless1% of the released amount. According to the measurements, airborne activity levels remain of no concern for public health in Europe. © 2011 American Chemical Society.

Calculations of 154 Eu and 155 Eu activities in the Chernobyl Unit IV reactor are given, together with a discussion of the uncertainties involved and comparison with results of other authors. The measurements of activities of the Chernobyl-origin ‘fuel-like’ hot particles (fuel fragments) and analysis of the radionuclide fractionation reveal a common behaviour of 154 Eu, 155 Eu and 144 Ce radioisotopes as regards non-volatility, similar to 95 Zr and 95 Nb in hot particles.