Post-Chernobyl 137Cs in the atmosphere of Thessaloniki: a consequence of the financial crisis in Greece.

The background radiation level of (137)Cs at the urban atmosphere of Thessaloniki has been increased during the recent decade only due to the Fukushima accident fallout. Since then, no other signal of (137)Cs was observed until the winter period of 2013, when slightly elevated (137)Cs concentrations were measured. The (137)Cs signals observed were up to 12 µBq m(-3), mainly during holidays and weekends followed by lower or even non-detectable activities in the next working days. Those episodes are attributed to the increase of biomass products combustion for residential heating as this year the tax of oil for heating was drastically raised as a consequence of the financial crisis. A preliminary survey of various wood products as well as of bottom ashes from different domestic burning devices is presented. (137)Cs concentrations up to 11 Bq kg(-1) were measured in wood products and up to 500 Bq kg(-1) in ash samples.

Environmental measurements and inspections on imported foods and feedstuffs in Greece after the Fukushima accident.

The radionuclides released during the accident at the Fukushima Daichii nuclear power plant following the Tohoku earthquake and tsunami on 11 March 2011 were dispersed in the whole north hemisphere. Traces of (131)I, (134)Cs and (137)Cs reached Greece and were detected in air, grass, sheep milk, ground deposition, rainwater and drainage water. Members of Six Greek laboratories of the national network for environmental radioactivity monitoring have collaborated with the Greek Atomic Energy Commission (GAEC) and carried out measurements during the time period between 11 March 2011 and 10 May 2011 and reported their results to GAEC. These laboratories are sited in three Greek cities, Athens, Thessaloniki and Ioannina, covering a large part of the Greek territory. The concentrations of the radionuclides were studied as a function of time. The first indication for the arrival of the radionuclides in Greece originating from Fukushima accident took place on 24 March 2011. After 28 April 2011', concentrations of all the radionuclides were below the minimum detectable activities (<10 µBq m(-3) for (131)I). The range of concentration values in aerosol particles was 10-520 µBq m(-3) for (131)I, 10-200 µBq m(-3) for (134)Cs and 10-200 µBq m(-3) for (137)Cs and was 10-2200 µBq m(-3) for (131)I in gaseous phase. The ratios of (131)I/(137)Cs and (134)Cs/(137)Cs concentrations are also presented. For (131)I, the maximum concentration detected in grass was 2.2 Bq kg(-1). In the case of sheep milk, the maximum concentration detected for (131)I was 2 Bq l(-1). Furthermore, more than 200 samples of imported foodstuff have been measured in Greece, following the EC directives on the inspection of food and feeding stuffs.

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 <1% of the released amount. According to the measurements, airborne activity levels remain of no concern for public health in Europe.

Radioiodine and radiocesium in Thessaloniki, Northern Greece due to the Fukushima nuclear accident.

Radioiodine ((131)I) in air and rainwater as high as 497 µBq m(-3) and 0.7 Bq L(-1), respectively, as well as (137)Cs and (134)Cs in air as high as 145 µBq m(-3) and 126 µBq m(-3), respectively were recorded in Thessaloniki, Northern Greece (40°38'N, 22°58'E) from March 24, 2011 through April 09, 2011, after a nuclear accident occurred at Fukushima, Japan (37°45'N, 140°28'E) on March 11, 2011.

Dose measurements around spallation neutron sources.

Neutron dose measurements and calculations around spallation sources appear to be of great importance in shielding research. Two spallation sources were irradiated by high-energy proton beams delivered by the Nuclotron accelerator (JINR), Dubna. Neutrons produced by the spallation sources were measured by using solid-state nuclear track detectors. In addition, neutron dose was calculated after polyethylene and concrete, using a phenomenological model based on empirical relations applied in high-energy physics. The study provides an analytical and experimental neutron benchmark analysis using the transmission factor and a comparison between the experimental results and calculations.

The application of phosphogypsum in agriculture and the radiological impact.

Radium-226 in phosphogypsum produced in a phosphate industry, SICNG operating at Thessaloniki, Northern Greece since May 1966, varied from 261 to 688 Bq kg(-1) (mean value 508 Bq kg(-1)). This radionuclide in soil tilled with phosphogypsum used for agricultural purposes varied from 50 to 479 Bq kg(-1) (average 205 Bq kg(-1)), while in the regular soil of cultivated fields it varied from 37 to 54 Bq kg(-1) (average 48 Bq kg(-1)). Radium-226 in rice originated from cultivated fields tilled with phosphogypsum or not varied from 0.36 to 1.98 Bq kg(-1) (average 1.53 Bq kg(-1)) with the higher values observed in samples originated from cultivated fields tilled with phosphogypsum. Radium-226 transfer factors, TF, from soil tilled with phosphogypsum to plants for the case of rice varied from 6.5 x 10(-3) to 2.0 x 10(-2) (geometric mean: 1.1 x 10(-2)). A mean (226)Ra content in rice 1.53 Bq kg(-1) results in a daily intake of (226)Ra by humans in Greece 0.0084 Bq day(-1) leading to an annual effective dose for adults 0.86 microSv y(-1) which is much less in contributing to the average exposure to natural radiation sources (2.4 mSv y(-1)) and particularly to the part due to ingestion (0.29 mSv y(-1)). It is necessary to continuously control (monitoring) (226)Ra in phosphogypsum before any use for agricultural purposes.

Detection of spallation neutrons and protons using the (nat)Cd activation technique in transmutation experiments at Dubna.

Various spallation sources have been used to transmute long-lived radioactive waste, mostly making use of the wide energy neutron fluence. In addition to neutrons, a large number of protons and gamma rays are also emitted from these sources. In this paper (nat)Cd is proved to be a useful activation detector for determining both thermal-epithermal neutron as well as secondary proton fluences. The fluences measured with (nat)Cd compared with other experimental data and calculations of DCM-DEM code were found to be in reasonable agreement. An accumulation of thermal-epithermal neutrons around the center of the target (i.e. after approx. 10 cm) and of secondary protons towards the end of the target is observed.

Cesium-137 in grass from Chernobyl fallout.

Grass ecosystem was monitored for 137Cs, a relatively long-lived radionuclide, for about 16 years since the Chernobyl reactor accident occurred on April 26, 1986. Cesium-137 in grass gramineae or poaceae the species, ranged from 122.9 Bq kg(-1) (September 4, 1986) to 5.8 mBq kg(-1) (October 16, 2001) that is a range of five orders of magnitude. It was observed that there was a trend of decreasing 137Cs with time reflecting a removal half-time of 40 months (3 1/3 years), which is the ecological half-life, T(ec) of 137Cs in grassland.

Temporal changes of 7 Be and 210 Pb concentrations in surface air at temperate latitudes 40 degrees N.

Atmospheric concentrations of (7)Be and (210)Pb were measured for 15 years (1987--2001) in ground-level air at Thessaloniki, Northern Greece (40 degrees 38'N, 22 degrees 58'E). Mean activity concentrations of (7)Be and (210)Pb were 5.02 mBqm(-3) and 664 microBqm(-3), respectively, characteristic of the latitude of 40 degrees N. Monthly atmospheric concentrations of (7)Be showed a strong seasonal trend with the highest values being observed in the summer and the lowest in the winter period. Multiple regression analysis of the data of (7)Be concentrations and a number of meteorological parameters revealed that the sunspot number and temperature are the most significant parameters affecting the concentrations of (7)Be in surface air. The observed strong positive correlation between the mean monthly concentrations of (7)Be and the temperature confirms that the increased rate of vertical transport within the troposphere, especially during the warm months, has as a result to carry down to the surface layer air masses enriched in (7)Be. Highest values of the mean monthly atmospheric concentrations of (210)Pb were observed in the autumn and lowest in the spring period. The positive correlation that was observed between (210)Pb and (7)Be concentrations during the summer months suggests that these two radionuclides could be used together as tracers of environmental processes.

Measurement of radon emanation factor from granular samples: effects of additives in cement.

Two methods for radon emanation factor determination were performed and compared regarding their measuring accuracy: (a) by hermetically closing the sample in an airtight container and measuring the induced radon activity, and (b) by mixing charcoal and sealing the sample hermetically and after placing the sample in an open vessel with no charcoal addition, measuring each time the 226Ra content using gamma-spectrometry. Measurements of radon emanation factor of cement and pozzolanic additives, i.e. fly ash and phosphogypsum were also performed.

Assessment of natural radiation exposure and radon exhalation from building materials in Greece.

In controlling the natural radiation exposure for the residents of dwellings, it is necessary to determine the levels of natural radioactivity (external exposure) and radon exhalation rate (internal exposure) from building materials. Using a high-resolution gamma ray spectrometry system, the activity concentration of natural radionuclides was measured. The radon exhalation rate was measured by hermetically closing the sample in a container and following the radon activity growth as a function of time. Three different methods were applied in order to find the most appropriate, i.e. that with the less uncertainty for the less exposure time. Typical building materials were analyzed in order to examine the external and internal exposures. In addition, the total annual effective dose was evaluated for the residents of a typical Greek dwelling.

Application of activation methods on the Dubna experimental transmutation set-ups.

High spallation neutron fluxes were produced by irradiating massive heavy targets with proton beams in the GeV range. The experiments were performed at the Dubna High Energy Laboratory using the nuclotron accelerator. Two different experimental set-ups were used to produce neutron spectra convenient for transmutation of radioactive waste by (n,x) reactions. By a theoretical analysis neutron spectra can be reproduced from activation measurements. Thermal-epithermal and fast-super-fast neutron fluxes were estimated using the 197Au, 238U (n,gamma) and (n,2n) reactions, respectively. Depleted uranium transmutation rates were also studied in both experiments.

Coloured rain dust from Sahara Desert is still radioactive.

A coloured rain event originating from the Sahara Desert occurred on April 9, 2000 at Thessaloniki, Northern Greece (40 degrees 38'N, 22 degrees 58'E). The radioactive nuclides that were determined in a coloured rain dust sample were 137Cs of Chernobyl origin, 7Be of cosmogenic origin and 40K of terrestrial origin. Cesium-137 still remained 14 years after the Chernobyl accident, reaching 26.6 Bq kg-1 in the coloured rain dust.

Atmospheric deposition of cosmogenic 7Be and 137Cs from fallout of the Chernobyl accident.

Atmospheric (tropospheric) depositional fluxes of the naturally occurring 7Be of cosmogenic origin and 137Cs from fallout of the Chernobyl accident were measured over a 7-year period (January 1987-December 1993) at Thessaloniki, Greece (40 degrees 38' N, 22 degrees 58' E). The annual total deposition fluxes of 7Be varied between 854 Bq/m2 (1987) and 1242 Bq/m2 (1992), showing a minimum in the years 1988-89. The annual total deposition fluxes of 137Cs varied between 183 Bq/m2 (1987) and 16.4 Bq/m2 (1992), showing a significant decrease as expected for natural removal and radioactive decay and no new releases from nuclear facilities or weapons testing. The annual average total deposition velocity for 7Be was from 0.3 cm/s (1988) up to 0.8 cm/s (1991), while for 137Cs the corresponding values were much higher, hence 137Cs was associated with larger atmospheric particles. High 7Be concentrations in air were related to the very little solar activity (1987-88 and 1993-94), while low 7Be concentrations in air related to the high solar activity (1989-91). Maximum 137Cs concentrations in air were registered during the spring 1991 and 1992, reflecting some stratospheric inputs. An unusual highly elevated value of 137Cs concentration in air, reaching 0.25 mBq/m3, was observed during the summer 1990.

Indoor radon concentrations in Greek apartment dwellings.

Radon concentrations indoors were determined in 24 typical occupied apartments in the city of Thessaloniki, North Greece (40 degrees 38'N, 22 degrees 58'E), by means of 12 surveys, each 2 mo long, over a 2-y period starting October 1989. The ratio of the winter and summer averages for the first year of measurements was 1.8 +/- 0.78, and for the second year of measurements was 1.6 +/- 0.61. The indoor radon concentration in the summer (1990) period ranged between 8 and 81 Bq m-3, while in the winter (1989-1990) it ranged between 20 and 143 Bq m-3 for the first year of measurements or between 8 and 92 Bq m-3 in the summer (1991) period and between 12 and 119 Bq m-3 in the winter (1990-1991) for the second year of measurements. These results were obtained by type CN-85 alpha track detectors. Some parameters that influenced the concentrations, such as precipitation rates and use of fly ash in building materials, are discussed.

Seasonal variations of 137Cs content of milk after the Chernobyl accident.

Results are presented on monthly measurements of 137Cs content in cows' milk over a 3-y period after the Chernobyl reactor accident. It was observed that, in an annual cycle of measurements, the 137Cs concentration of milk increased between December and August, peaking in April each year, due to the dependency of the 137Cs content of cattle feed on the fallout activity of 137Cs. There was a consistent correlation between the 137Cs concentration of milk and surface air.

Time-dependent radioactive concentrations of fallout following the Chernobyl reactor accident.

The levels of Chernobyl-derived 137Cs, 134Cs, 106Ru and 103Ru were measured at Thessaloniki, Greece, in air, rain, soil, grass and milk samples for more than 2 years after the accident. The data were analysed in conjunction with 7Be (produced in the atmosphere by cosmic rays) measurements and show that significant variations were observed, particularly in the spring and in the autumn measurements. In interpreting these variations we took into consideration the tropospheric, or possibly stratospheric, fallout injections into the atmosphere due to the Chernobyl accident, nuclear weapons testing or other releases from nuclear reactors operating world-wide. Useful information can be derived for determining the periodicity of global circulation of the fallout radionuclides.

The radioactivity of coloured rain in Thessaloniki, Greece.

The radioactivity of coloured rain precipitated over Thessaloniki, Greece, on 4-5 April 1988 was determined. The long-lived fission product radionuclides such as 137Cs, 134Cs, 144Ce, 106Ru and 125Sb were identified in dust originating from the Sahara desert which was precipitated with the rain to produce coloured rain. Caesium-137 concentrations reached 1000 Bq kg-1, resulting in a deposition of 3.03 Bq m-2, which is four orders of magnitude lower than measured on 5-6 May 1986 after the Chernobyl reactor accident.

Silver-110m and 125Sb in Chernobyl fallout.

Measurements of the two unusual nuclides 110mAg and 125Sb in soils and grass, derived from fallout, were made in Greece after the Chernobyl reactor accident. The 110mAg concentrations ranged from 4.5 to 46.1 Bq kg-1 (average 14.3 Bq kg-1) in soils and from 0.2 to 1.5 Bq kg-1 (average 0.8 Bq kg-1) in grass. The 125Sb concentrations ranged from 15.7 to 284.6 Bq kg-1 (average 105.0 Bq kg-1) in soils and from 1.1 to 19.6 Bq kg-1 (average 4.4 Bq kg-1) in grass.