Using high-resolution γ−ray spectroscopy, the terrestrial gamma radiation in all the predominant types of geological rock formations appearing in Cyprus was measured. Soil samples were collected from each rock type, sealed in 1-litre plastic Marinelli beakers, and measured in the laboratory for 24 hours each. From the measured γ−ray spectra, activity concentrations were determined for 232 Th (range from 1.3 to 52.8 Bq kg −1 ), 238 U (from 0.9 to 90.3 Bq kg −1 ) and 40 K (from 13 to 894 Bq kg −1 ). Elemental concentrations mean values of (2.8 ± 0.7) ppm, (1.3 ± 0.3) ppm and (0.6 ± 0.1) % were extracted, for thorium, uranium and potassium, respectively. Absorbed dose rates in air outdoors were calculated to be in the range of 0.1−50 nGy h −1 , depending on the geological features, with an overall mean value of (14.7 ± 7.3) nGy h −1 . The corresponding effective dose rates per person outdoors were estimated to be between 0.1 and 61.4 µSv y −1 , assuming a 20% occupancy factor.

The gamma radiation in samples of a variety of natural tiling rocks (granites) imported in Cyprus for use in the building industry was measured, employing high-resolution γ−ray spectroscopy. The rock samples were pulverized, sealed in 1-litre plastic Marinelli beakers, and measured in the laboratory with an accumulating time between 10 and 14 hours each. From the measured γ−ray spectra, activity concentrations were determined for 232 Th (range from 1 to 906 Bq kg −1 ), 238 U (from 1 to 588 Bq kg −1 ) and 40 K (from 50 to 1606 Bq kg −1 ). The total absorbed dose rates in air calculated from the concentrations of the three radionuclides ranged from 7 to 1209 nGy h −1 for full utilization of the materials, from 4 to 605 nGy h −1 for half utilization and from 2 to 302 nGy h −1 for one quarter utilization. The total effective dose rates per person indoors were determined to be between 0.02 and 2.97 mSv y −1 for half utilization of the * Corresponding author. E-mail address: tsertos@ucy.ac.cy, Fax: +357-22339060. Department of Physics, University of Cyprus, P. O. Box 20537, 1678 Nicosia, Cyprus. 2 materials. Applying dose criteria recently recommended by the EU for superficial materials, 25 of the samples meet the exemption dose limit of 0.3 mSv y −1 , two of them meet the upper dose limit of 1 mSv y −1 and only one exceeds clearly this limit.

A survey was carried out to determine activity concentration levels and associated dose rates from the naturally occurring radionuclides 232

In October 2017, most European countries reported unique atmospheric detections of aerosol-bound radioruthenium (106Ru). The range of concentrations varied from some tenths of µBq·m−3 to more than 150 mBq·m−3. The widespread detection at such considerable (yet innocuous) levels suggested a considerable release. To compare activity reports of airborne 106Ru with different sampling periods, concentrations were reconstructed based on the most probable plume presence duration at each location. Based on airborne concentration spreading and chemical considerations, it is possible to assume that the release occurred in the Southern Urals region (Russian Federation). The 106Ru age was estimated to be about 2 years. It exhibited highly soluble and less soluble fractions in aqueous media, high radiopurity (lack of concomitant radionuclides), and volatility between 700 and 1,000 °C, thus suggesting a release at an advanced stage in the reprocessing of nuclear fuel. The amount and isotopic characteristics of the radioruthenium release may indicate a context with the production of a large 144Ce source for a neutrino experiment.

A comprehensive study was conducted to determine thorium, uranium and potassium elemental concentrations in surface soils throughout the accessible area of Cyprus using high-resolution γ−ray spectrometry. A total of 115 soil samples was collected from all over the bedrock surface of the island based on the different lithological units of the study area. The soil samples were air-dried, sieved through a fine mesh, sealed in 1000-mL plastic Marinelli beakers, and measured in the laboratory in terms of their gamma radioactivity for a counting time of 18 hours each. From the measured γ−ray spectra, elemental concentrations were determined for thorium (range from 2.5×10 −3 to 9.8 µg g −1 ), uranium (from 8.1×10 −4 to 3.2 µg g −1 ) and potassium (from 1.3×10 −4 to 1.9 %). The arithmetic mean values (A.M. ± S.D.) calculated from all samples are:(1.2 ± 1.7) µg g −1 , (0.6 ± 0.7) µg g −1 , and (0.4 ± 0.3) %, for thorium, uranium and potassium, respectively, which are by a factor of three to six lower than the world average values of 7.4 µg g −1 (Th), 2.8 µg g −1 (U) and 1.3 % (K) derived from all data available worldwide. The best-fitting relation between the concentrations of Th and K * Corresponding author. E-mail address: tsertos@ucy.ac.cy, Fax: +357-22892821. 2versus U, and also of K versus Th, is essentially of linear type with a correlation coefficient of 0.93, 0.84, and 0.90, respectively. The Th/U, K/U, and K/Th ratios (slopes) extracted are equal to 2.0, 2.8×10 3 , and 1.4×10 3 , respectively.