M. Manolopoulou

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.

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.

Radon concentrations and absorbed dose measurements in a Pleistocenic cave

Radon concentration measurements were carried out using solid-state nuclear track-etch detectors (SSNTDs) type CA 80-15 cellulose nitrate films, in a Pleistocenic cave at Petralona, in Halkidiki, Northern Greece, at 55 km from the city of Thessaloniki. Radon levels as high as 88 kBq.m-3 (2.38 nCi.l-1) have been recorded inside the cave equivalent to 11.90 WL in terms of occupational exposure to radon and its decay products. Absorbed dose rates were performed using TL dosimeters, type TLD-200 (CaF2-Dy) in a continuous monitoring program (integrated measurements). Dose rate levels as high as 110 nGy.h-1 were recorded inside the cave. In interpreting the high levels of radiation doses, radioactivity measurements regarding the naturally occurring 238U, 232Th and 40K radionuclides were carried out in various speleothems found at different sites in the cave.

Silver-110 m 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.

A simple device for measuring radon exhalation from the ground

Abstract A special device was developed for measuring radon exhalation from the ground in the earthquake prediction research. A solid state nuclear track (SSNT) detector (CA 80-15) has been used as a probe. The thoron registration is reduced by a factor of 103. Several problems concerning field measurements (e.g. humidity) were solved.

A new technique for accurate measurements of Ra-226 with γ-spectroscopy in voluminous samples

Publisher Summary Accuracy in the measurements of Ra-226 concentrations by γ-spectroscopy depends on an appropriate estimation of Rn-222 decay product concentrations (Pb-214 and Bi-214) in the sample. As an inert gas, radon can leak from the sample vessel and/or can be accumulated in the upper, void part of it. In the latter case radon decay products can be attached on the inner surface of the sample container, and therefore, the produced γ-rays have a different geometry and a self-absorption factor from the one assumed (similar to the calibration sample). The influence of the above procedures on the accuracy of the measurements depends mainly on the emanation factor of radon in the sample, the geometry used in the measurement and the structure of the sample container. For the estimation of Ra-226 concentration one assumes that the radioactivity is homogeneously distributed in the sample, as it is in the calibration sample. As a result, the accuracy in the determination of Ra-226 concentration in the sample depends on the amount of the effective radium in the sample as well as the geometry characteristics of the sample vessel. In this paper, the results of the tests performed with a new technique developed to eliminate radon diffusion through the sample, are presented.

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.

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.

Extensive performance studies for the ATLAS BIS-MDT precision muon chambers with cosmic rays

ATLAS (A Toroidal LHC ApparatuS) is a general-purpose experiment, which will start its operation at the Large Hadron Collider (LHC) at CERN in 2007. The ATLAS detector is designed to explore numerous physics processes by measuring, recording, and investigating the products emerging from proton-proton collisions at energies up to 14 TeV. High-precision muon momentum measurement (dp/p-10% at p/sub T/=1 TeV/c) over large areas using Monitored Drift Tube (MDT) chambers is crucial for the ATLAS experiment. More than 1,200 MDT chambers, assembled from approximately 370,000 drift tubes operated at 3 bar pressure, will be used to provide for the total detector coverage of 5,500 m/sup 2/. Three Greek universities have taken the responsibility to construct 30,000 drift tubes of /spl sim/1.7 in length, to test them and finally assemble them into 120 BIS (Barrel Inner Small) chambers. The design of the muon drift tubes aims at high efficiency (>95%) and a spatial resolution of <80 /spl mu/m (single tube resolution). This paper describes the cosmic ray setup, which has been instrumented in order to verify. that the BIS chamber Module-0 fulfils its design requirements. The analysis of its data shows that the chamber meets these requirements; it has low noise levels, uniform drift properties, good spatial resolution and high particle detection efficiency.

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.