Milos Zivanovic, Amra Sabeta, Nikola Krzanovic
et al.
This paper presents a comparison performed between two calibration laboratories in several radiation qualities, using dosimeters of varying quality as transfer instruments. The goal of this work was to investigate the viability of using field-class dosimeters for official comparisons and to determine if the calibration factors for field-class dosimeters are comparable between calibration laboratories within the stated measurement uncertainties. The results of the comparison were acceptable for high-quality electronic personal dosimeters in all radiation qualities, and such dosimeters could be used as transfer instruments. On the other hand, comparison results for low-quality dosimeters were often not acceptable, either due to pronounced energy dependence, low stability, or both. Such instruments are unreliable even under well-defined laboratory conditions, and their use in routine measurements may cause doubt in official data or influence public opinion. This problem is often hidden because many dosimeters are calibrated or verified only in 137Cs beams, where the deviations are the smallest. The largest differences are found for low-energy X-ray radiation qualities, where many dosimeters have significant overresponse.
Cornelius Holtorf is UNESCO Chair on Heritage Futures at Linnaeus University. He reads prehistoric archaeology, social anthropology and physical anthropology in Germany, England and Wales. In 1998 he gained his PhD and was subsequently employed in research and teaching at the University of Gothenburg (1998-1999), the University of Cambridge (1999-2002), the Swedish National Heritage Board in Stockholm (2002-2004) and the University of Lund (2005-2008). Since 2008 Cornelius have been working at Kalmar where he is currently a Professor of Archaeology at Linnaeus University and Director of the Graduate School in Contract Archaeology (GRASCA).
Sabahudin Hadrovic, Igor Celikovic, Jelena Krneta-Nikolic
et al.
The results of the gamma-spectrometric measurements in a 16500 ha large region of south-western Serbia, are presented. Activity concentrations of 40K, 137Cs, and 210Pb in different deciduous and evergreen trees in the region are investigated. For all the investigated isotopes, there is a tendency that, on average, the lowest activity concentrations were found in tree stems, then in leaves, while the highest ones were in the soil. Statistical analysis did not show any differences between activity concentrations of leaves and needles, showing that both leaves and needles could be equally well used as a biomonitors.
Particle size distribution of radon progeny is one of the most important parameters and it needs to be measured accurately. Graded screen array measurement is the most frequently used method for analyzing the characteristics of radon progeny but it needs optimization due to its complex configuration. In this paper, collection efficiency of a single screen and the number of screen array were applied for optimization and simplification of the graded screen array configuration by a series of experimental measurements, theoretical calculations, and standard comparison research methods. When optimized in this way, an experiment was designed for radon progeny particle size distribution in a customized radon chamber. The experiment results indicated that the activity median diameter in unattached mode was 0.81 nm and 287.32 nm in attached mode, which were similar to the results obtained by other researchers. The results prove that the method can satisfy the requirements of graded screen array measurement.
Seeking optimal material distribution in a nuclear system to maximize a response function of interest has been a subject of considerable interest in nuclear engineering. Examples are the optimal fuel distribution in a nuclear reactor core to achieve uniform burnup using minimum critical mass and the use of composite materials with an optimal mix of constituent elements in detection systems and radiation shielding. For such studies, variational methods have been found to be useful but, they have been used for standalone analyses often restricted to idealized models, while more elaborate design studies have required computationally expensive Monte Carlo simulations ill-suited to iterative schemes for optimization. Such an inherent disadvantage of Monte Carlo methods changed with the development of perturbation algorithms but, their efficiency is still dependent on the reference configuration for which a hit-and-trial approach is often used. In the first illustrative example, this paper explores the computational speedup for a bare cylindrical reactor core, achievable by using a variational result to enhance the computational efficiency of Monte Carlo design optimization simulation. In the second example, the effect of non-uniform material density in a fixed-source problem, applicable to optimal moderator and radiation shielding, is presented. While applications of this work are numerous, the objective of this paper is to present preliminary variational results as inputs to elaborate stochastic optimization by Monte Carlo simulation for large and realistic systems.
Smet de, Isabelle Gerardy, Frederic Stichelbaut
et al.
Proton therapy uses proton beams with energies typically between 50 and 230 MeV to treat cancerous tumors very efficiently, while protecting as much as possible surrounding healthy tissues from radiation damage. Protons interacting with matter inevitably induce secondary radiation from which all people inside the proton therapy center have to be protected. The ambient dose equivalent H*(10) in such a facility is mainly due to neutrons, which can have energies up to 230 MeV. Although various dose monitoring systems sensitive to high energy neutrons have already been developed, the response function of these detectors is often insufficiently characterized, and so are the calibration factors appropriate for the specific neutron spectra encountered inside a proton therapy facility. In this work, the Monte Carlo code MCNPX 2.5.0 has been used to study the response function of the extended-range rem-meter WENDI-2 from thermal energies up to 5 GeV. A good match has been obtained with equivalent simulation results found in literature. As a first step towards the characterization of the WENDI-2 response in continuous neutron fields, MCNPX simulations have also been carried out for the case-study of a bunker around an 18 MeV H-cyclotron, which involves neutron fields from thermal energies up to 18 MeV.
In this paper the detailed structure of the transport beam line design is proposed, quadrupoles and deflectors specifications in order to transport the beam from the optic adaptation point in the SPIRAL2 production building up to the adaptation point in the DESIR hall. All optical elements, in beam line, are electrostatic and so, settings are independent of the ratio q/m of the particle. The calculations are done by COSY INFINITY computer code in first order of approximation and without fringe field effects. The beam emittances at the starting point (adaptation point in the SPIRAL2 production building) in horizontal and vertical planes are 80p mm mrad. The beam line is designed in such a way that the beam sizes, in both planes, at the end (adaptation point in the DESIR hall) are kept the same as they are at the starting point; the horizontal and vertical displacements from the optic axis at starting and ending points are the same, ?6 mm. In such case the efficiency of transport of the beam is high.
Nenad Stevanovic, Vladimir Markovic, Momir Arsenijevic
et al.
In this paper the stopping power was calculated, representing the electrons of the target atom as an assembly of quantum oscillators. It was considered that the electrons in the atoms have some velocity before interaction with the projectile, which is the main contribution of this paper. The influence of electron velocity on stopping power for different projectiles and targets was investigated. It was found that the velocity of the electron stopping power has the greatest influence at low energies of the projectile.