Constantinos Potiriadis

Greek Atomic Energy Commission · Environmental Radioactivity Monitoring

Moon is an auspicious environment for the study of Galactic cosmic rays (GCR) and Solar Particle Events (SEP) due to the absence of magnetic field and atmosphere. The same characteristics raise the radiation risk for human presence in orbit around it or at the lunar surface. The secondary (albedo) radiation resulting from the interaction of the pri...

The goal of this study is to provide a benchmark for the use of Monte Carlo simulation when applied to coincidence summing corrections. The examples are based on simple geometries: two types of germanium detectors and four kinds of sources, to mimic eight typical measurement conditions. The coincidence corrective factors are computed for four radio...

The goal of this work was to develop a methodology for risk assessment in case of an accident originating from a nuclear power plant, and consequently, to improve the relevant radiation monitoring network. In specific, the study involved risk estimation in Greece from a transboundary nuclear power plant accident. The tool employed was JRODOS (Java-...

This work aims at providing a Monte-Carlo based methodology for calculating true coincidence correction (TCC) factors for volume sources of varying density. All simulations were carried out using the most recent version of Monte Carlo code PENELOPE. The main program PENMAIN was used for the calculation of full energy peak efficiencies. The subrouti...

The data acquisition system of a radiation monitor package for lunar mission is presented. The package enables the measurement of the flux of all the main particles present in the lunar environment as a function of their energy, as well as the measurement of dosimetric quantities. It encompasses electron gamma and proton – ion – fast neutron telesc...

The Miniaturized Detector for Application in Space (MIDAS) is a compact device with dimensions 5 x 5 x 1 cm 3 which combines position sensitive Si detectors and a fast neutrons spectrometer. MIDAS is developed with purpose to act as a linear energy transfer (LET) spectrometer for the charged particles and measure dose and dose equivalent from both...

The Miniaturized Detector for Application in Space (MIDAS) is a compact device with dimensions 5 x 5 x 1 cm3 which combines position sensitive Si detectors and a fast neutrons spectrometer. MIDAS is developed with purpose to act as a linear energy transfer (LET) spectrometer for the charged particles and measure dose and dose equivalent from both c...

In this study, a semi-empirical calibration method for NORM samples measurement by using a LaBr3(Ce) scintillator was developed based on a combination of experimental gamma spectrometry measurements and MCNP-X simulations. The aim of this work is to provide us with full energy peak efficiency calibration curves in a wide photon energy range which i...

Within the present work a peak analysis and unfolding method for low energy γ-ray spectroscopy is presented. This method can be used to facilitate the determination of the peak integral of a photopeak, when Ge X-ray escape peaks contaminate the latter and in parallel the source activity and the emission rate of the recorded photons which produce th...

In the present work the Ho165(n,2n) reaction was studied experimentally and theoretically for the population of the ground state (Jπ=1+) of the Ho164 product nucleus, as well as for the population of its isomeric state (Eex=139.8 keV, Jπ=6−). The cross sections of both the ground and isomeric state channels were measured at energies near the reacti...

The present work concerns the preliminary analysis for the study of the (n,2n) reaction channel of the 165Ho isotope at near threshold energies: 10.1, 10.4 and 10.7 MeV (Eth=8.04 MeV). The cross sections for the population of both the ground state (Jπ=1+) and the isomeric state (Jπ=6-, Eex=139.8 keV) of the 164Ho product-nucleus were measured at th...

Radiation doses received by astronauts outside the geomagnetic field are a main risk factor for human space exploration. The Miniaturized Detector for Application in Space (MIDAS) device is a highly miniaturized radiation detector (mass <50 g, volume < 5 × 5 × 1 cm³) which is under development using fully depleted monolithic active pixel sensors an...

The Miniaturized Detector for Application in Space (MIDAS)device is developed in response to the requirement of the European Space Agency for a device whose size, power consumption and radiation data output would increase the level of space-flight crew autonomy regarding operational decisions related to radiation hazards. It is designed as a wristw...

We present a small factor (0.5cm 3) CZT static sensor network consisted of a number of Non-Directional Detectors (NDD) capable to localize bare and lightly shielded radiation sources. The localization is performed with a fusion algorithm based on a fast analytical technique. The algorithm has been tested using simulated data and verified with exper...

Using coded aperture, for localization of radioactive hot-spots, results in enhanced efficiency and under certain configurations wide Field of View (FOV).We present a coded aperture assembly technique which can be restructured easily, as well as the reduction of the intrinsic noise of coded apertures constructed with this technique, when they local...

This paper presents the peak-to-background ratio improvement, which can be achieved in PIXE and XRF applications by the use of thin crystal detectors. This improvement becomes apparent in the presence of an intense γ-ray source, which can be produced either after proton irradiation of a sample (PIXE), or after the deexcitation of the radionuclide i...

MIDAS is a miniature detector developed with purpose to assess the radiation field parameters near to an astronaut. Part of the device is a spectrometer for fast neutrons. In missions outside the geomagnetic field, fast neutrons are secondary products of the interaction of Galactic Cosmic Ray heavy ions with the materials in the spaceship or even t...

MIDAS is a miniature detector developed with purpose to assess the radiation field parameters near to an astronaut. Part of the device is a spectrometer for fast neutrons. In missions outside the geomagnetic field, fast neutrons are secondary products of the interaction of Galactic Cosmic Ray heavy ions with the materials in the spaceship or even t...

The MIDAS device is a detector with wristwatch dimensions and mass less than 50g. It consists of a plastic scintillator cube connected to a silicon photomultiplier on its one face, while all the other faces are covered by a titanium box and 2 consecutive layers of fully depleted silicon pixel sensors with in-pixel signal processing electronics. Its...

The probabilities of locating peaks with a high relative peak-area uncertainty were determined empirically with nine types of peak-location software used in laboratories engaged in gamma-ray spectrometry measurements. It was found that it is not possible to locate peaks with a probability of 0.95, when they have a relative peak-area uncertainty in...

Radionuclides of natural origin of the Uranium and Thorium series and the Potassium-40 are present in most materials. These materials are commonly referred to as Naturally Occurring Radioactive Materials (NORMs). In Greece there are few industries involving NORM, among which 3 fertilizer industries of which only one is in operation. This industry i...

In the Council Directive 2013/51/EURATOM of 22 October 2013, laying down requirements for the protection of the health of the general public with regard to radioactive substances in water intended for human consumption, determination of several radionuclides is required. Among the natural radionuclides that have to be determined for the estimation...

We present measurements of ¹³⁴Cs and ¹³⁷Cs activity concentrations in topsoil from the greater area of the Fukushima Daiichi nuclear power plant (FDNPP) in the period 2011–2013. Fallout concentrations were determined by means of gamma-ray spectrometry, using high purity germanium (HPGe) detectors. Concentration measurements ranged up to tens of tho...

Monte Carlo (MC) simulation is widely used in gamma-ray spectrometry, however, its implementation is not always easy and can provide erroneous results. The present action provides a benchmark for several MC software for selected cases. The examples are based on simple geometries, two types of germanium detectors and four kinds of sources, to mimic...

Detection of radioactive sources in unconstrained environment with no specific entrance and exit points remains a challenge for nuclear security. The problem is more difficult when it comes to shielded radiation sources. In this work we present an approach of a sensor network that is composed of small form factor CZT radiation sensors which uses bo...

Monte Carlo simulations and verification measurements for the efficiency calibration of the ACCUSCAN shadow-shield type Whole Body Counter (WBC) of the Greek Atomic Energy Commission (EEAE) are presented. A model of the counter and RMC-II anthropomorphic phantom was developed using the MCNP code. Full energy peak efficiencies for different phantom...

This work evaluates the 137Cs and 90Sr content of wood pellets of the Greek energy market and additionally calculates worker exposure in Greek catering establishments (rotisseries). Wood pellets and ash samples were analysed through high resolution gamma-ray spectroscopy and liquid scintillation. Imported pellets had higher 137Cs concentrations, es...

A regulatory authority for radiation safety should continuously evaluate and improve the national safety framework, in line with current requirements and standards. In this context, the Greek Atomic Energy Commission initiated a series of concerted actions. The radiation dose to the population due to public and medical exposures was assessed. The a...

Electrical characteristics of Mo-MoO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</sub> /p-CdTe/ MoO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</sub> -Mo, Ti-TiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org...

The complexation of 238U and 234U in tap water and seawater after the use of a selective membrane was examined. At the first step, many ligands were used for original membranes preparation and their yields in uranium analysis were evaluated by X-ray fluorescence, in order to select the ligand with the highest uranium selectivity in water samples. A...

The Telemetric Early Warning System Network of the Greek Atomic Energy Commission consists mainly of a network of 24 Reuter-Stokes high-pressure ionization chambers (HPIC) for gamma dose rate measurements and covers all Greece. In the present work, the response of the Reuter-Stokes HPIC to terrestrial and cosmic radiation was evaluated in compariso...

For the first time, a radiological study for the dissolved 238U, 234U, 210Pb and 210Po was held in major Greek rivers across the country. 234U/238U activity ratios are above one in all samples and 210Po/210Pb activity ratios are respectively below the unit indicating the disequilibrium in the samples. Quite satisfactory correlations were observed a...

Coded aperture imaging transcends planar imaging with conventional collimators in efficiency and Field of View (FOV). We present experimental results for the detection of 141 keV and 122 keV γ-photons emitted by uniformly extended 99mTc and 57Co hot-spots along with simulations of uniformly and normally extended 99mTc hot-spots. These results prove...

This paper reports on the possible applications of molybdenum oxide (Mo/MoOx) contacts in combination with semi-insulating CdTe crystals. The electrical contacts to p-type Cl-doped CdTe crystals were formed by the deposition of molybdenum oxide and pure molybdenum thin films by the DC reactive magnetron sputtering. Electrical properties of the prep...

A Radiation Sensor Network with the Ability to Localize Radiation Sources

Radiation Source LOcalization with a network of radiation sensors

After the Fukushima accident important initiatives were taken in European level to enhance the nuclear safety level of the existing and planned nuclear reactors, such as the so-called nuclear “stress-tests” and the amendment of the Nuclear Safety Directive. A recent work of HERCA and WENRA focused on the need for a more consistent and harmonized re...

A uranium isotopes study has been carried out in river waters all over Greece, because surface waters play an essential role in the migration and redistribution of radionuclides in the earth crust.

Following the nuclear accident at the Fukushima Daiichi Nuclear Power Plant on 11 March 2011, during the period 17 March to 25 October 2011, a total of 22 Greek citizens were measured after their return to Greece. Artificial radionuclides were detected in 5 of the 22 measured individuals by whole body counter measurements conducted 10 and 11 d afte...

We describe a system consisting of two CdTe based gamma cameras with coded apertures and a video camera. The system is used for the localization of radioactive sources with the aid of triangulation. The methods used and the performance of the system are analyzed.

The development of instruments utilizing coded apertures has become more feasible with the progress of the Cd(Zn)Te hybrid detector technology. The collective performance of systems comprised by such devices can be evaluated in all the fields where traditionally coded aperture imaging has been applied. Along this direction, we present the evaluation...

Several small gamma cameras for radioguided surgery using CdTe or CdZnTe have parallel or pinhole collimators. Coded aperture imaging is a well-known method for gamma ray source directional identification, applied in astrophysics mainly. The increase in efficiency due to the substitution of the collimators by the coded masks renders the method attr...

The thermal and mineral spring waters contain naturally occurring radioactive substances. These waters have variable amounts of certain dissolved substances, as solute solubility increases with increasing temperature. Among these dissolved substances are radioactive elements of natural origin. These waters are in close contact with soil and rocks c...

A nuclear accident took place at the Fukushima Daiichi Nuclear Power Plant on March 11th, 2011, after the power plant was hit by a tsunami triggered by an earthquake, resulting in a meltdown of three of the plant’s six nuclear reactors. A total of 22 Greek citizens were measured with the WBC during the period 17th March to 25th October 2011 after t...

At the north part of Greece a phosphate fertilizer industry is in operation since 1965. The produced phosphogypsum is deposited continuously near the industry, by the sea side, in an open land disposal area of about 500000 m2. The estimated phosphogypsum mass is about 13 million tons. The Greek Atomic Energy Commission, the competent national regu...

Στην καθημερινή μας ζωή συνυπάρχουμε με τις ακτινοβολίες καθώς μας περιβάλλουν φυσικές και τεχνικές πηγές ακτινοβόλησης, οι οποίες έχουν ως αποτέλεσμα την εξωτερική ή εσωτερική έκθεση του ανθρώπινου οργανισμού. Κατά την εσωτερική έκθεση ραδιενεργά στοιχεία εναποτίθενται στα διάφορα όργανα του σώματος και τα ακτινοβολούν έως ότου απεκκριθούν μέσω τω...

The Nuclear Technology Laboratory of the Aristotle University of Thessaloniki (NTL-AUTh) and the Greek Atomic Energy Commission (GAEC) have a continuous collaboration on indoor radon measurements in Greek buildings since 1999. In the present work, the existing database was enriched with 590 indoor radon measurements in 295 houses and 76 indoor rado...

The radionuclides released during the accident at the Fukushima Daichii nuclear power plant following the Tōhoku 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. Memb...

A prototype shadow-shield whole body counter is used at the University of Ioannina Medical Physics Laboratory as a tool in radiation protection and in biomedical research. In this study the effect of natural airborne radioactivity on the measurement quality features was investigated and performance improvements were developed. Radon air concentrati...

Working group II of the IAEA programme EMRAS II focuses on the issue of "NORM and legacy sites". An overview of the objectives and achievements of the working group-composed of both modellers and regulators-is given. e group performed a review of several NORM and legacy sites from 16 countries and developed a General Assessment Methodology. Two sit...

We present results on the reconstructed image resolution of a position sensitive radiation instrument (COCAE) based on extensive simulation studies. The reconstructed image resolution has been investigated in a wide range of incident photon energies emitted by point-like sources located at different source-to-detector distances on and off the detec...

Since the double disaster of the 9.0 magnitude earthquake and tsunami that affected hundreds of thousands of people and seriously damaged the Fukushima Daichi power plant in Japan on 11 March 2011, traces of radioactive emissions from Fukushima have spread across the entire northern hemisphere. The radioactive isotope of iodine 131I that was genera...

The COCAE project develops an instrument for localization and identification of radioactive sources. For the localization task it will exploit the Compton scattered photons within its detecting layers. It is based on pixilated Cd(Zn)Te matrices in a stacked configuration. Progress has been achieved in all the components necessary for this technolog...

Simulation studies are presented regarding the performance of algorithms that localize point-like radioactive sources detected by a position sensitive portable radiation instrument (COCAE). The source direction is estimated by using the List Mode Maximum Likelihood Expectation Maximization (LM-ML-EM) imaging algorithm. Furthermore, the source-to-de...

1. Background for forming the group Many sites around the world are contaminated by man-made radionuclides or materials containing naturally occurring radionuclides (NORM). Sites that have not been operated with adequate controls according to present standards may pose a hazard to humans and the environment. Many sites fall within the definition in...

Spectroscopic measurements are presented using the PID350 pixelated gamma radiation detectors. A high-speed data acquisition system has been developed in order to reduce the data loss during the data reading in case of a high flux of photons. A data analysis framework has been developed in order to improve the resolution of the acquired energy spec...

The COCAE project develops an instrument for localization and identification of radioactive sources. For the localization task it will exploit the Compton scattered photons within its detecting layers. It is based on pixilated Cd(Zn)Te matrices in a stacked configuration. Progress has been achieved in all the components necessary for this technolog...

During a preliminary survey at the area of an abandoned fertilizer plant, increased levels of radioactivity were measured at places, buildings, constructions and materials. The extent of the contamination was determined and the affected areas were characterized as controlled areas. After the quantitative and qualitative determination of the contami...

Spectroscopic measurements are presented using the PID350 pixelated gamma radiation detectors. A high-speed data acquisition system has been developed in order to reduce the data loss during the data reading in case of a high flux of photons. A data analysis framework has been developed in order to improve the resolution of the acquired energy spec...

Simulation studies and spectroscopic measurements are presented regarding the development of a pixel multilayer CdTe detector under development in the context of the COCAE project. The instrument will be used for the localization and identification of radioactive sources and radioactively contaminated spots. For the localization task the Compton ef...

We present extensive simulation studies on the performance of algorithms for the Compton sequence reconstruction used for the development of a portable spectroscopic instrument (COCAE), with the capability to localize and identify radioactive sources, by exploiting the Compton scattering imaging. Various Compton Sequence reconstruction algorithms h...

Medical examinations performed on four monks of a monastery in the northern Greece revealed heavy metal contamination. Hair analysis, performed by a toxicological laboratory abroad, indicated, among other, the presence of uranium. The uranium concentrations determined in a laboratory of “Elemental Hair Analysis’ indicated a uranium level that was a...

In the northern part of Greece, close to the city of Kavala, a phosphoric acid production industry has operated since 1965. The raw material used is the phosphate rock imported from the foreign countries. During industrial processes, naturally occurring radioactive materials (NORM) deposits exist in many facilities in the industry, causing increase...

Portal monitoring radiation detectors are commonly used by steel industries in the probing and detection of radioactivity contamination in scrap metal. These portal monitors typically consist of polystyrene or polyvinyltoluene (PVT) plastic scintillating detectors, one or more photomultiplier tubes (PMT), an electronic circuit, a controller that ha...

Indoor radon concentrations were measured in 77 schools of the prefecture of Xanthi in northern Greece. The arithmetic mean radon concentration is 231 Bq m−3 with a range between 45 and 958 Bq m−3. Thirty five schools have mean radon concentration above 200 Bq m−3 and nine schools have mean radon concentration above 400 Bq m−3. From continuous rado...

Portal radiation detectors are commonly used by steel industries in the probing and detection of radioactivity contamination in scrap metal. Furthermore, a large number of portal monitors are installed at the border crossings to prevent illegal radioactive material trafficking. These portal detectors typically consist of either PS (polystyrene) or...

Among the patterning technologies proposed and applied for the realization of high-aspect-ratio structures in the micro- and nanoscale, proton beam writing (PBW) is considered to be a valuable tool for maskless patterning of such structures owing to the unique ability of protons to maintain a straight path over long distances. In this work, the PBW...