No abstract available

[en] Radioactivity measurements of Greek lignites have shown that all of them contain radioactive isotopes of the uranium series. Radium-226 and uranium-238 concentrations have been found to be higher than those so far reported in the literature of lignites. Concentrations of ²³⁸U up to 35 pCi/g have been observed in the lignites of Serres area (Northern Greece). (T.A.)

[en] In this paper the effects of low-level ionizing radiations on man are reviewed. These effects are closely connected to the risks associated with the operation of nuclear power plants. The review examines both the rather universally accepted views and those expressed by individual researchers, the latter being quantitatively or qualitatively different from the first ones. The expected effects of the most serious nuclear power plant accident at Three Mile Island are also analyzed, based on the collective doses of the population, and finally some conclusions are drawn. (author)

[en] The lignites of the southern area (Christos-Vissiani-Lefkes-Perdikari) and the bituminous clay silts of the northern area (Maramena, Ano Metohi, Chrysopigi) are the main uraniferous beds in the Serres Basin. The sediments of the basin (Upper Miocene to recent) have been stratigraphically divided into three informal unities: the Lefkon, Georgios and Spilia formations. The uraniferous lignites pertaining to the Lefkon limnic-fluvial formation are developed into two discrete horizons, the upper Double Seam and the lower Main Seam. The bituminous clays are of the same age with the lignites, those of Maramena being, however, younger, equivalent to the marine and brackish Georgios formation. The continuity, thickness and dip of the strata reveal considerable regional changes resulting from the intense tectonism of the basin. Further to the surface works the upper lignites have been reached through small excavations and also about 100 boreholes totalling 10,000 m have been drilled. The composition of the organic constituents and the calorific value show a dull transitional to shiny hard lignite with ash rich in pyrite and sulphur. There have been no discrete U minerals detected, while the electron microprobe analysis showed that the uranium is uniformly disseminated into the lignite mass, mainly absorbed through its humic acids. More than 75% of the uranium is extractable, the control of its combustion conditions being, however, a major problem. The potential reserves have been up to date estimated to be of over 4,000 tons (uranium metal), this figure resulting mainly from data evaluated from the borehole γ-ray logs using the computer programmes LOGFILE and LOGPLOT developed at the Radioactive Raw Materials Dept. of the Greek AEC. (author)

[en] In accordance with the agreement between the UN Development Programme, the IAEA and the Greek AEC car-borne scintillometer, ground scintillometer and geochemical stream sediment surveys, along with reconnaissance geological mapping have been carried out within the area of map sheets 2623(I,IV)-2624-2723-2724 (Ormenio-Orestiada-Didymoticho, Evros Dept., Thrace). The results of these surveys, presented in a series of 15 maps, indicate that three areas (Petrota-Pentalofos, Mikro Derio, Petrota) totalling 355 km² will require further detailed examination in order to test their potential of economic uranium deposits. Of these areas the first two (340 km²) should be given first priority and be further investigated by detailed stream sediment and water sampling, detailed ground scintillometer measurements, grid soil and radon soil gas samplings, as well as by detailed geological mapping. (author)

[en] The scientific activities and achievements of the Nuclear Research Center Democritus for the years 1977 and 1978 are presented in the form of a list of 79 projects giving title, objectives, commencement year, responsible of each project and the pertaining lists of publications. The 14 chapters of this work cover the activities of the main Divisions of the Democritus NRC: Exploration of Radioactive Minerals, Computer Center, Environmental Radioactivity, Chemistry, Physics, Biology, Soil Science, Electronics, Reactor, Health Physics, Radioisotopes, Technological Applications and Medical Service. (T.A.)

[en] In the present report realistic estimations about the nuclear accident at Chernobyl and the radioactivity burdening of Greece from the radioactive releases of the accident are presented. Results of radioactivity measurements in Greece concerning the environment and the food chain are given and some estimations for the population doses and the expected consequences of the accident are made. (J.K.)

[en] The present work is concerned first with the study of certain aspects of the leaching kinetics of Cs⁺ and Sr⁺⁺ embedded in cement, as Cs₂SO₄ and SrSO₄, and in particular: (a) the comparative evaluation of leaching in (i) stagnant, (ii) stirred and (iii) continuously flowing (modified Soxhlet) water, (b) the effect of atmospheric CO₂ on elution, (c) the effect of temperature changes during leaching. Secondly, model kinetic studies were carried out using cellulose acetate incorporating SrSO₄, CaSO₄ or NaCl. The main results obtained were: (1) Cs leaching rates were not significantly affected by the leaching method or by the presence of atmospheric CO₂. The embedded Cs exists in relatively easily leachable and less rapidly leachable (most probably located within the gel regions) forms. (2) Elution of Sr is retarded by stagnant and infrequently renewed leachant (method (i)) and by the presence of atmospheric CO₂; leaching method (iii), which tends to minimize both of these effects, gave the highest elution rates. (3) The observed elution kinetics in the case of cellulose acetate-CaSO₄ or SrSO₄ conform to the Higuchi model, but a more elaborate theory is needed for the cellulose acetate-NaCl system. (author)

[en] In this work a general description of the ADREA-I code is presented and some preliminary results are discussed. The ADREA-I is a transient three dimensional computer code aimed at transport analysis with particular emphasis on atmospheric dispersion under any realistic terrain conditions (complex or not) applicable to the planetary boundary layer in a distance extending up to a hundred kilometers or more. The complex geometry applications and the reasonable results obtained constitute a solid indication of the broad capability of the code. (author)

[en] Full text: The concentrations of mixed fission products in sea water and of ¹³⁷Cs in fish and sea plants are different for samples collected from different sampling areas. This difference is more remarkable the year where the level of the world wide fall-out is higher, especially with regards to M. F. P. concentrations in sea water samples. Increases or decreases to M.F.P. concentrations in sea water samples result to increases or decreases of ¹³⁷Cs in fish and sea plants. (author)