I. Sýkora

Dispersion of Fukushima radionuclides in the global atmosphere and the ocean

Large quantities of radionuclides were released in March-April 2011 during the accident of the Fukushima Dai-ichi Nuclear Power Plant to the atmosphere and the ocean. Atmospheric and marine modeling has been carried out to predict the dispersion of radionuclides worldwide, to compare the predicted and measured radionuclide concentrations, and to assess the impact of the accident on the environment. Atmospheric Lagrangian dispersion modeling was used to simulate the dispersion of (137)Cs over America and Europe. Global ocean circulation model was applied to predict the dispersion of (137)Cs in the Pacific Ocean. The measured and simulated (137)Cs concentrations in atmospheric aerosols and in seawater are compared with global fallout and the Chernobyl accident, which represent the main sources of the pre-Fukushima radionuclide background in the environment. The radionuclide concentrations in the atmosphere have been negligible when compared with the Chernobyl levels. The maximum (137)Cs concentration in surface waters of the open Pacific Ocean will be around 20 Bq/m(3). The plume will reach the US coast 4-5 y after the accident, however, the levels will be below 3 Bq/m(3). All the North Pacific Ocean will be labeled with Fukushima (137)Cs 10 y after the accident with concentration bellow 1 Bq/m(3).

Aerosol radioactivity record in Bratislava/Slovakia following the Fukushima accident – A comparison with global fallout and the Chernobyl accident

Results of radioactivity measurements in Bratislava aerosols following the Fukushima accident showed that at least three radioactive plumes arrived to Bratislava as indicated by (131)I/(137)Cs activity ratios. When compared with the Chernobyl results available for the Bratislava station, the Fukushima radionuclide levels were almost five orders of magnitude lower, with the maximum values for (131)I and (137)Cs of 0.5 and 0.07 mBq/m(3), respectively. The (131)I and (137)Cs vs. (7)Be aerosol activity records showed that the increases in (131)I and (137)Cs activity concentrations were accompanied by (7)Be increases, indicating that both the horizontal and vertical transports of radionuclides were responsible for observed radionuclide concentrations. The (134)Cs/(137)Cs activity ratio was close to 1, as has also been reported by other investigators.

Aerosol radioactivity monitoring in Bratislava following the Chernobyl accident

The radiation situation in Bratislava following the Chernobyl accident is discussed. Measurement results of γ- and α-radioactivity of aerosols are presented. The evolution of the activity ratios in air for some radionuclides is discussed. Their distribution indicates different transport and deposition properties for the volatile and nonvolatile fission products. The results are compared with long-term measurements of anthropogenic radionuclides released to the atmosphere by nuclear bomb tests.

Method for precise analysis of the metal package photomultiplier single photoelectron spectra

Abstract A sophisticated photomultiplier response function was suggested for single photoelectron analysis of the compact metal package photomultiplier spectra. The spectra taken by Hamamatsu R5600 photomultipliers have been analysed by the presented method. The detailed analysis shows that the method appropriately describes the process of charge multiplication in these photomultipliers and can be used to find their basic internal parameters.

Long-term variations of 14C and 137Cs in the Bratislava air – implications of different atmospheric transport processes

This study summarizes measurements of atmospheric (14)C and (137)Cs in the Bratislava air since 1976. Higher (14)C levels observed in spring and early summer months until the 1980s confirm injection of the stratospheric air into the troposphere. Later, deep winter minima were observed in (14)C concentrations, probably due to the depletion of the atmospheric (14)C levels in winter months by the injection of large quantities of fossil CO(2). Presently observed (14)C maxima in summer and minima in winter were caused by the depletion of the atmospheric (14)C in winter months, amplified by temperature inversions during winter, rather than by the injection of the stratospheric air into the troposphere. The observed (137)Cs activity concentrations also showed an impact of the stratospheric air on the (137)Cs levels until the early 1980s, documented by typical spring/early summer maxima and winter minima. The global fallout (137)Cs record was then disturbed by the Chernobyl accident (1986) when large quantities of (137)Cs were released to the atmosphere. The recent (137)Cs variations observed in the atmosphere, characterised by winter maxima and summer minima, are assumed to be mainly due to the resuspension of (137)Cs from the soil. A correlation was found between the (137)Cs activity concentration and the dust level in the air (the correlation coefficient r = 0.74), as well as an anticorrelation with the temperature (r = -0.56).

Fukushima-derived radionuclides in ground-level air of Central Europe: a comparison with simulated forward and backward trajectories

Results of forward and backward modeling of air mass transport from Fukushima Daiichi nuclear power plant to Slovakia were compared with aerosol radioactivity measurements. Several radionuclide maxima (131I, 134Cs and 137Cs) were observed in the Bratislava ground-level air in March–April 2011. The 131I/137Cs activity ratio records showed the presence of two different fresh air masses in the Bratislava air, supported by simulations of forward and backward trajectories between Fukushima and Bratislava.

Measurement of electron capture to positron emission ratios in light and medium nuclides

Abstract The triple coincidence method and a Ge(Li)-NaI(Tl)-NaI(Tl) spectrometer were used for measurement of EC/β+ ratios of 22Na, 26Al, 44Sc and 88Y. A comparison of theoretical and experimental results shows a good agreement for 26Al and 44Sc and disagreement for 22Na and 88Y.

Radionuclide content in some building materials and their radon exhalation

The activity concentrations of natural radionuclides in sands, gravels, cements and in different kinds of concretes were measured by γ-spectrometric methods. The222Rn exhalation rate from concretes was measured by closed chamber method and the emanation coefficient was calculated. Both used methods are described in detail and obtained results are discussed from point of view of allowed hygienic limits.

Certified reference materials for radionuclides in Bikini Atoll sediment (IAEA-410) and Pacific Ocean sediment (IAEA-412).

The preparation and characterization of certified reference materials (CRMs) for radionuclide content in sediments collected offshore of Bikini Atoll (IAEA-410) and in the open northwest Pacific Ocean (IAEA-412) are described and the results of the certification process are presented. The certified radionuclides include: (40)K, (210)Pb ((210)Po), (226)Ra, (228)Ra, (228)Th, (232)Th, (234)U, (238)U, (239)Pu, (239+240)Pu and (241)Am for IAEA-410 and (40)K, (137)Cs, (210)Pb ((210)Po), (226)Ra, (228)Ra, (228)Th, (232)Th, (235)U, (238)U, (239)Pu, (240)Pu and (239+240)Pu for IAEA-412. The CRMs can be used for quality assurance and quality control purposes in the analysis of radionuclides in sediments, for development and validation of analytical methods and for staff training.

Average daily and annual courses of222Rn concentration in some natural medium

Simultaneous measurements of the222Rn concentration in the outdoor atmosphere of Bratislava and in the soil air over one year period have been made. Daily and seasonal variations of the222Rn concentration in both media were found. Some attributes of these variations as well as methods of measurements are presented in this work.