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