C. Papastefanou

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.

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.

Aerodynamic size association of 7Be in ambient aerosols

Abstract The aerodynamic size distribution of 7 Be in ambient aerosol particles was determined by using 1-ACFM cascade impactors. The activity distribution of 7 Be measured by γ-spectrometry ( E γ = 447 keV ), was largely associated with submicron aerosols in the accumulation mode (0.4–2.0 μm). The activity median aerodynamic diameter, AM AD ranged from 0.76 to 1.18μm (average 0.90μm), indicating post-condensation growth either in the upper atmosphere or after mixing into the boundary layer. The geometric standard deviation, gs g ranged from 1.86 to 2.77 (average 2.24). In 65% of the cascade impactor measurements the activity distributions of 7 Be showed maxima in the 0.7 to 1.1 μm size range. In estimating lifetimes of 7 Be aerosols in ambient air, a mean residence time of about 8 days averaged for tropospheric aerosols of 0.90 μm AM AD size.

Lichens and mosses: Biological monitors of radioactive fallout from the Chernobyl reactor accident

Abstract In the aftermath of the Chernobyl reactor accident, the radioactivity in lichens and mosses has been studied. 137Cs concentrations ranged from about 1070 to 14 560 Bq kg−1 in lichens and from 270 to 4750 Bq kg−1 in mosses. Besides the cesium isotopes, some other relatively long-lived fission nuclides, such as 106Ru, 144Ce, 125Sb, and the 110mAg produced by neutron activation were detected and measured. The present data set supports the view that these nonvascular plants can be useful biological monitors of radioactive fallout from not only nuclear weapon tests but also accidents at any nuclear facilities.

Radiation measurements and radioecological aspects of fallout from the cherbonyl reactor accident

Fallout from the Chernobyl reactor accident has been monitored for about one year in Thessaloniki in Northern Greece. Fifteen different short-lived, three relatively long- and one long-lived fission products were identified in air, precipitation, soil, grass and milk samples. The iodine-131 and cesium-137 concentrations in air reached 6·5 and 3 Bq m−3 respectively, on 6 May, 1986. The external exposure dose rate rose to five times the normal background level. It was estimated that the accumulated dose equivalent to the adult thyroid from inhaled iodine-131 averaged 96 μSv, while the body burden from inhaled radiocesium nuclides averaged 2 μSv, 1000 times lower than that corresponding to the estimated dose equivalent from ingestion of foodstuff, which averaged 2 mSv for the first year after the accident.

Behavior of natural radionuclides in lignites and fly ashes

The behavior of naturally-occurring radionuclides 238U, 226Ra, 210Pb, 228Ra (232Th) and 40K in lignites and fly ashes is described. The concentrations of 238U, 226Ra and 210Pb in lignites were increased with decreasing concentrations of 40K, resulting in an inverse relationship, whereas the concentration of 228Ra (232Th) increased with an increasing concentration of 40K. In fly ashes, 238U and 210Pb were enriched on smaller particles, while 40K decreased. The content of the two isotopes of radium, 226Ra and 228Ra, also decreased in finer particles of fly ash but the rate of decrease for 226Ra was found to be weaker than on the corresponding one of 228Ra as well as of 40K. The above observations are discussed.

Depositional fluxes and other physical characteristics of atmospheric beryllium-7 in the temperate zones (40°N) with a dry (precipitation-free) climate

Abstract Atmospheric depositional fluxes of 7Be were measured over a 3-year period (January 1987–April 1990) in Thessaloniki, Greece (40°38′N, 22°58′E). Total precipitation accumulation during 1987, 1988 and 1989 was 65.0, 46.2 and 32.6 cm, respectively, reflecting a relatively dry (precipitation-free) climate. The volume-weighted concentrations of 7Be in rainwater ranged between 0.1 and 5.2 Bq l −1 (average 0.6 Bq l −1). The annual total deposition fluxes of 7Be in 1987, 1988 and 1989 were 841, 510 and 483 Bq m−2, respectively, while the average concentrations of 7Be in the atmosphere in the corresponding periods were 6.3, 5.7 and 4.2 mBq m−3, showing a decreasing trend with time. On an annual average, the washout (scavenging) ratio for 7Be was 144 and the resuspension factor was 2.5 × 10−4 m−1, the latter is too high. The annual average total deposition velocity for 7Be was estimated to be 0.4 cm s−1. The air-to-vegetation transfer rate estimate for 7Be is 5150 m3 kg−1. Seasonal variations of 7Be concentration depend considerably on the local meteorological conditions, mainly the rainfalls.

An overview of instrumentantion for measuring radon in soil gas and groundwaters.

Instruments for the measurements of radon and its decay products in earthquake research are based mostly on the detection of alpha particles. The devices and methods used, depend on whether the techniques measure radon or radon decay products, and the duration of the measurements, of which there are three types: (i) grab or instantaneous; (ii) integrating; and (iii) continuous. Other criteria used in the design of these instruments are field measurements applicability. portability. convenience and reliability. With the recent increased demand for radon and radon decay products measurements, instruments development has focused on the design of appropriate devices for short-term measurements, as well as on more complex and sophisticated instruments for long-term measurements used in radon research for geophysical, geochemical and hydrological studies.

Radiological impact from atmospheric releases of 238U and 226Ra from phosphate rock processing plants

Phosphate rocks are used extensively, mainly as a source of phosphorus for fertilizers and secondarily for phosphoric acid and other speciality chemicals. Phosphates are typically enriched in uranium and are thus one of the sources of technologically enhanced natural radiation (TENR) which increases exposure to man from natural radionuclides. Emissions from phosphate rock processing plants in gaseous and particulate form contain radionuclides, such as 238U and 226Ra, which are discharged into the environment causing radiation exposures to the population. About 10 MBq each of 238U and 226Ra are discharged into the environment each year from SICNG, a phosphate rock processing plant in Thessaloniki area, Northern Greece. The collective dose commitment to lung tissue resulting from atmospheric releases was estimated to be approximately 2 x 10(-9) person Gy t-1 for 238U and approximately 0.1 x 10(-9) person Gy t-1 for 226Ra, i.e. about 2 times higher than that estimated in the UNSCEAR reports issued in 1982, 1988, and 1993.

Radioactivity in tobacco leaves.

The radioactivity in tobacco leaves collected from 15 different regions of Greece before cigarette production was studied in order to find any association between the uptake of the naturally occurring radionuclides and the isotopes of cesium of Chernobyl origin. The activities of the isotopes of radium, 226Ra and 228Ra, in the tobacco leaves reflected their origin from the soil by root uptake rather than from fertilizers used in the tobacco cultivation. Lead-210 originated from the air and was deposited onto the tobacco leaves and trapped by the trichomes. Potassium-40 in the tobacco leaves was due to root uptake either from soil or from fertilizer. The isotopes of cesium, 137Cs and 134Cs, in the tobacco leaves were due to root uptake and not due to deposition onto the leaf foliage as they still remained in soil four years after the Chernobyl reactor accident but were absent from the atmosphere in rain washout (precipitation) and gravitational settling.