Assessment of environmental radiation monitoring data in Hungary following the Fukushima accident

The unusually strong earthquake in Japan on 11 March 2011 and the following extreme tsunami caused enormous damage in the buildings of Fukushima Dai-ichi Nuclear Power Plant (NPP) situated on the Pacific coastline of Japan. The accident led to the release of a large amount of radioactive material into the environment. According to the measurements of the Radiological Monitoring and Data Acquisitions Network (RAMDAN) the radioactive plume reached Hungary on 24 March 2011. The main volatile fission products – 131I, 134Cs, and 137Cs radioisotopes – were measurable in aerosol and fallout samples in Hungary. Their activity concentration in air reached the maximum value in the last days of March and returned to the background level in the first half of May. As a consequence of respiration of contaminated air, a maximum of 1 Bq per capita of 131I could be accumulated in the thyroid gland of the Hungarian population during the given period. The calculated upper limits of the committed effective dose from inhalation of 131I were 4 nSv and 10 nSv to the Hungarian adults and infants, respectively. These values are a hundred thousand times less than the annual radiation dose from natural sources to the Hungarian population. The radiation dose from radioactive caesium isotopes originating from Fukushima was even less, around 1 nSv on average, to Hungarian residents. No health deterioration can be expected from this radiation burden

Tracking of Airborne Radionuclides from the Damaged Fukushima Dai-Ichi Nuclear Reactors by European Networks

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 ((131)I) and cesium isotopes ((137)Cs and (134)Cs) 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 (131)I fraction were conducted compared to the number of measurements for the particulate fraction. Several studies had already pointed out the importance of the gaseous (131)I and the large underestimation of the total (131)I 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 (131)I fraction to total (131)I, both on a spatial scale and its temporal variation. It can be pointed out that during the Fukushima event, the (134)Cs to (137)Cs 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 (131)I inventory that has passed over Europe during this period was LT 1% of the released amount. According to the measurements, airborne activity levels remain of no concern for public health in Europe