Dosimetry Laboratory

Seibersdorf, Austria

Dosimetry Laboratory

Seibersdorf, Austria
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Hranitzky C.,Dosimetry Laboratory
Radiation Protection Dosimetry | Year: 2016

The Dosimetry Laboratory Seibersdorf was the irradiation laboratory for the IC2014 EURADOS intercomparison for individual monitoring. One hundred and twelve whole-body dosimetry systems with 30 dosemeters per dosimetry system participated in the intercomparison. In total, 2240 personal dosemeters were irradiated in photon reference radiation fields on the ISO water slab phantom in terms of personal dose equivalent Hp(10) and Hp(0.07). Two nuclide irradiation systems (137Cs and 60Co gamma radiation) and a 320-kV X-ray radiation unit were used. The irradiation plan consisted of nine irradiation set-ups with five different ISO/IEC photon radiation qualities (S-Cs, S-Co, RQR 7, W-80 and W-150) and two different angles of radiation incidence (0° and 60°). Reference dose equivalent values were in the range of ~1-500 mSv. Reference values were based on air kerma rate traceable to primary standard calibrations and appropriate conversion coefficients resulting in total expanded measurement uncertainties <6 %. © The Author 2015. Published by Oxford University Press. All rights reserved.

Loiseau P.,Dosimetry Laboratory | Geslot B.,CEA Cadarache Center | Andre J.,Aix - Marseille University
Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment | Year: 2013

Fission Chambers (FCs) are widely used as neutron detectors for online flux measurement. The FC current pulse charge is a key observable quantity which depends on specifications such as the filling gas pressure and the FC geometry. In order to study pulse charges, experimental data have been acquired at the Cadarache zero power reactor MINERVE. Two chambers with contrasting specifications have been used. The experimental pulse charge spectrum is interpreted by the mean of a modeling of fission products (FPs) energy deposition within the filling gas. The pulse charge spectrum peaks are found to correspond to FP emitted perpendicularly to the electrodes. © 2013 Published by Elsevier B.V.

Filliatre P.,Dosimetry Laboratory | Jammes C.,Dosimetry Laboratory | Jeannot J.-P.,CEA Cadarache Center | Jadot F.,CEA Cadarache Center
Annals of Nuclear Energy | Year: 2014

With appropriate techniques, the information brought by the in-vessel instrumentation of nuclear reactors may betray rather subtle departures from normal state indicating an abnormal situation at early stages, to improve both safety and availability. This paper takes the case of the detection of delayed neutrons released by a clad failure in sodium-cooled fast neutron reactors as an illustrative application of hypothesis testing. Two methods are discussed, seeking either for a counting excess of for a departure from stationarity, yielding similar results. The question of false alarms is addressed by a Bayesian approach that takes into account the prior probability of failure. The use of several identical sensors is shown to be effective. © 2013 Elsevier Ltd. All rights reserved.

Jammes C.,Dosimetry Laboratory | Filliatre P.,Dosimetry Laboratory | Loiseau P.,Dosimetry Laboratory | Geslot B.,CEA Cadarache Center
Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment | Year: 2012

In this paper, we address the question of how the signal of a uranium fission chamber is sensitive to the thickness of its fissile coating. We first review the electrodeposition technique in order to status on the maximum surface density reasonably achievable. Then, we assess the effect of the neutron flux perturbation on the possible loss of detection efficiency. The most important part of this work is the assessment how the energy spectrum of a fission chamber is affected by the so-called self-absorption of the fission products in the fissile coating. We present a Monte Carlo code we developed in order to achieve that goal. That numerical tool allowed us to reveal the linear relation between the sensitivity loss and the coating thickness, with a slope of 8%/(mg/cm 2). Numerical results are discussed with respect to experimental data and a need of new experiments is expressed. Finally, we showed the frequent assumption of the straight trajectory of fission products is not valid for a small fraction of those particles which have a kinetic energy less than 20 keV/amu. © 2012 Elsevier B.V. All rights reserved.

Chatgilialoglu C.,National Research Council Italy | Ferreri C.,National Research Council Italy | Lykakis I.N.,Aristotle University of Thessaloniki | Mihaljevic B.,Dosimetry Laboratory
Israel Journal of Chemistry | Year: 2014

Different types of lipid aggregations, such as micelles and liposomes, can be used as biomimetic models. The uses of γ-irradiation as a valid methodology for simulating the biological generation of thiyl radicals in these models are summarized and, in particular, thiyl radical catalyzed cis-trans isomerization of unsaturated lipids is underlined. The efficiency of antioxidants against lipid isomerization assayed by biomimetic models and the importance of trans lipids as novel biomarkers of radical stress are also described. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Mihaljevic B.,Dosimetry Laboratory | Tartaro I.,Dosimetry Laboratory | Ferreri C.,National Research Council Italy | Chatgilialoglu C.,National Research Council Italy
Organic and Biomolecular Chemistry | Year: 2011

Biomimetic models of free radical-induced transformation of polyunsaturated fatty acids, such as micelles and liposomes, have been used for the study of lipid peroxidation and lipid isomerization. Free radical reactivity of thiol compounds is the common link between the two processes, since lipid peroxidation is inhibited by thiols, due to their H-donation ability, whereas lipid isomerization is catalysed by S-centered radicals. In this paper the two processes are compared for the first time, in solution and under biomimetic conditions, demonstrating that hydroperoxides and trans lipids are formed to comparable extents as a result of oxidative free radical conditions. The biomimetic model of micelles of linoleic acid, prepared by addition of a non-ionic surfactant (TWEEN ®-20) and 2-mercaptoethanol as the amphiphilic thiol, was irradiated by ionizing radiation up to 400 Gy under various conditions. In air-equilibrated solutions, the cis-trans isomerization process was observed with a catalytic cycle of 370 together with a substantial amount of hydroperoxides (LOOH). The effect of micelle size was also studied in order to envisage the effect of the supramolecular organization on the outcome of the two processes, and in particular, for the positional preference of the double bond isomerization. © 2011 The Royal Society of Chemistry.

Elter Z.,Dosimetry Laboratory | Elter Z.,Chalmers University of Technology | Jammes C.,Dosimetry Laboratory | Pazsit I.,Chalmers University of Technology | And 2 more authors.
Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment | Year: 2014

The detectors of the neutron flux monitoring system of the foreseen French GEN-IV sodium-cooled fast reactor (SFR) will be high temperature fission chambers placed in the reactor vessel in the vicinity of the core. The operation of a fission chamber over a wide-range neutron flux will be feasible provided that the overlap of the applicability of its pulse and Campbelling operational modes is ensured. This paper addresses the question of the linearity of these two modes and it also presents our recent efforts to develop a specific code for the simulation of fission chamber pulse trains. Our developed simulation code is described and its overall verification is shown. An extensive quantitative investigation was performed to explore the applicability limits of these two standard modes. It was found that for short pulses the overlap between the pulse and Campbelling modes can be guaranteed if the standard deviation of the background noise is not higher than 5% of the pulse amplitude. It was also shown that the Campbelling mode is sensitive to parasitic noise, while the performance of the pulse mode is affected by the stochastic amplitude distributions. © 2014 Elsevier B.V. All rights reserved.

Elter Z.,Chalmers University of Technology | Elter Z.,Dosimetry Laboratory | Pazsit I.,Chalmers University of Technology | Jammes C.,Dosimetry Laboratory
Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment | Year: 2016

The signals of fission chambers are traditionally evaluated with Campbelling methods at medium count rates. Lately there has been a growing interest in the extension of Campbelling methods to cover a wider range of count rates. These methods are applied to measure the neutron flux in the stationary state of the reactor. However, there has not been any attempt to generalize these techniques for transient reactor states. This short note is devoted to a discussion of this question. It is shown through analytic and numerical calculations that for practical reasons the traditional, stationary Campbelling methods can be applied for transient scenarios as well. © 2016 Elsevier B.V. All rights reserved.

Pressyanov D.S.,Dosimetry Laboratory
Nukleonika | Year: 2010

An overview of ongoing directions of radon studies in the Faculty of Physics, St. Kliment Ohridski University of Sofia is presented. The focus is on: 1) Study and implementation of the polycarbonate method for measuring 222Rn. In this respect the results from laboratory and field experience with this method are summarized. Its potential for precise retrospective measurements by home stored CDs/DVDs is emphasized. 2) Surveys in radon risk areas in the country. The approaches and results in this direction are illustrated on the example of the town of Rakovski. In this town lung cancer risk is twice increased for both sexes. Significantly high 222Rn concentrations were observed in most of the houses and this can be the major factor contributing to the risk. 3) Mitigation of dwellings with high radon content. Mitigation works were recently initiated and our experience with passive radon barriers and active sub-slab depressurization systems is shared. Summarizing the results in all the three directions we conclude that there is a basis to enhance radon research and practice in the country. To be more efficient, these activities need collaboration with medical authorities, civil engineers and, especially in research, with international teams working in the field.

Mitev K.K.,Dosimetry Laboratory
Applied Radiation and Isotopes | Year: 2016

This work demonstrates that common plastic scintillators like BC-400, EJ-200 and SCSF-81 absorb radon and their scintillation pulse decay times are different for alpha- and beta-particles. This allows the application of pulse shape analysis for separation of the pulses of alpha- and beta-particles emitted by the absorbed radon and its progeny. It is shown that after pulse shape discrimination of beta-particles' pulses, the energy resolution of BC-400 and EJ-200 alpha spectra is sufficient to separate the peaks of 222Rn, 218Po and 214Po and allows 222Rn measurements that are unaffected by the presence of thoron (220Rn) in the environment. The alpha energy resolution of SCSF-81 in the experiments degrades due to imperfect collection of the light emitted inside the scintillating fibers. The experiments with plastic scintillation microspheres (PSM) confirm previous findings of other researchers that PSM have alpha-/beta-discrimination properties and show suitability for radon measurements. The diffusion length of radon in BC-400 and EJ-200 is determined. The pilot experiments show that the plastic scintillators are suitable for radon-in-soil-gas measurements. Overall, the results of this work suggest that it is possible to develop a new type of radon measurement instruments which employ absorption in plastic scintillators, pulse-shape discrimination and analysis of the alpha spectra. Such instruments can be very compact and can perform continuous, real-time radon measurements and thoron detection. They can find applications in various fields from radiation protection to earth sciences. © 2016 Elsevier Ltd.

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