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Open access

Wojciech Starosta, Viera K. Semina, Jerzy Smolik, Lech Waliś, Michał Rydzewski and Bożena Sartowska

Abstract

Zirconium alloys used widely in nuclear industry as fuel claddings are prone to violent oxidation in water steam atmosphere in the case of loss of coolant accident (LOCA). Accompanying generation of large quantities of heat and explosive gaseous hydrogen may lead to destruction of nuclear core. As the safety of nuclear installations is of primary importance, intensive research works are conducted on the development of so-called accident tolerant fuels much less prone to oxidation. In this paper, the application of external zirconium-silicide coatings deposited by magnetron sputtering is proposed. The preliminary results of their synthesis and studies of air oxidation properties at elevated temperatures are presented.

Open access

Mikołaj Oettingen and Przemysław Stanisz

Abstract

This paper describes the methodology developed for the numerical reconstruction and modelling of the thorium-lead (Th-Pb) assembly available at the Department of Nuclear Energy, Faculty of Energy and Fuels, AGH University, Krakow, Poland. This numerical study is the first step towards integral irradiation experiments in the Th-Pb environment. The continuous-energy Monte Carlo burnup (MCB) code available on supercomputer Prometheus of ACK Cyfronet AGH was applied for numerical modelling. The assembly consists of a hexagonal array of ThO2 fuel rods and metallic Pb rods. The design allows for different arrangements of the rods for various types of irradiations and experimental measurements. The intensity of the fresh neutron source intended for integral experiments is about 108 n/s, which corresponds to the mass of about 43 μg 252Cf. The source was modelled in the form of Cf2O3-Pd cermet wire embedded in two stainless steel capsules.

Open access

Haluk Yücel, R. Bora Narttürk, Senem Zümrüt, Gizem Gedik and Mustafa Karadag

Abstract

The aim of this study was to investigate the thermal neutron measurement capability of a CdZnTe detector irradiated in a mixed gamma-neutron radiation field. A CdZnTe detector was irradiated in one of the irradiation tubes of a 241Am-Be source unit to determine the sensitivity factors of the detector in terms of peak count rate (counts per second [cps]) per neutron flux (in square centimeters per second) [cps/neutron·cm−2·s−1]. The CdZnTe detector was covered in a 1-mm-thick cadmium (Cd) cylindrical box to completely absorb incoming thermal neutrons via 113Cd(n,γ) capture reactions. To achieve, this Cd-covered CdZnTe detector was placed in a well-thermalized neutron field (f-ratio = 50.9 ± 1.3) in the irradiation tube of the 241Am-Be neutron source. The gamma-ray spectra were acquired, and the most intense gamma-ray peak at 558 keV (0.74 γ/n) was evaluated to estimate the thermal neutron flux. The epithermal component was also estimated from the bare CdZnTe detector irradiation because the epithermal neutron cutoff energy is about 0.55 eV at the 1-mm-thick Cd filter. A high-density polyethylene moderating cylinder box can also be fitted into the Cd filter box to enhance thermal sensitivity because of moderation of the epithermal neutron component. Neutron detection sensitivity was determined from the measured count rates from the 558 keV photopeak, using the measured neutron fluxes at different irradiation positions. The results indicate that the CdZnTe detector can serve as a neutron detector in mixed gamma-neutron radiation fields, such as reactors, neutron generators, linear accelerators, and isotopic neutron sources. New thermal neutron filters, such as Gd and Tb foils, can be tested instead of the Cd filter due to its serious gamma-shielding effect.

Open access

Allan Felipe Nunes Perna, Sergei Anatolyevich Paschuk, Janine Nicolosi Corrêa, Danielle Cristine Narloch, Rafael Carvalho Barreto, Flávia Del Claro and Valeriy Denyak

Abstract

The main sources of radon in the air of dwellings are soil, building materials, and groundwater. This study aimed to determine the exhalation rate of 222Rn from samples made of concrete and cement mortars, as well as to evaluate by means of gamma spectrometry the hazard indexes associated with other radionuclides present in the studied samples of building materials. The results obtained allowed the comparison of the exhalation rate of radon using theoretical calculations based on one-dimensional and three-dimensional models. Measurements of the activity concentration of radon in air was performed by AlphaGuard radon detector. Furthermore, obtained results were compared with the measurements performed inside the concrete test cells. These test cells were built with the aim of simulating a dwelling in small dimensions and to evaluate indoor radon activity associated with concrete. Consequently, the obtained results of radon exhalation rate, in becquerel per meter squared per hour, for the concrete was 2.55 ± 0.03 Bq·h−1·m−2 for the 1D model and 0.461 ±0.008 Bq·h−1·m−2 for the 3D model. The exhalation rate of radon, for the cement mortar was 1.58 ± 0.03 Bq·h−1·m−2 for the 1D model and 0.439 ± 0.011 Bq·h−1·m−2 for the 3D model. The indoor concentration of 222Rn from the test cell was 112 ± 9 Bq/m3. These values were below the limit of 300 Bq/m3 recommended by the International Commission on Radiological Protection (ICRP) and <148 Bq/m3, the limit recommended by the US Environmental Protection Agency (US EPA). Even so, these values should be the subject of concern since that activity is related only to the contribution of concrete walls.

Open access

Wojciech Głuszewski, Andrzej Stasiek, Aneta Raszkowska-Kaczor and Daniel Kaczor

Abstract

The process of cross-linking of polyethylene using gamma radiation (γ) and electron beam (EB) was tested from the point of view of density of foam. Particular attention was paid to the postradiation oxidation effect of the polymers. The study used two types of radiation sources of varying dose rates: gamma radiation (4 kGy/h) and EB (14 000 kGy/h). Radiolysis studies of the polymers used the radiation yield of hydrogen evolved (G H2, approximately proportional to the number of radicals) and radiation yield of oxygen absorbed by the polymer (G O2). Oxidation of polymer due to radiation was also evaluated using diffuse reflectance spectroscopy.

Open access

Antoni Rożeń

Abstract

Heterogeneous catalytic recombination of hydrogen with oxygen is one of the methods used to remove hydrogen from the containment of a light-water nuclear reactor (LWR). Inside a passive autocatalytic recombiner (PAR), hydrogen and oxygen molecules are adsorbed at catalyst active spots and they recombine to yield water. Heat released in this exothermic reaction creates natural convection of gas in the spaces between the elements supporting a catalyst. Hot and humid gas flows upwards into the PAR chimney, while fresh, hydrogen-rich gas enters the PAR from below. Catalytic recombination should start spontaneously at room temperature and low hydrogen concentration. Computational fluid dynamics (CFD) has been used to study the dynamic behaviour of a plate-type Areva FR-380 recombiner in a quiescent environment for several test scenarios, including different rates of increase in hydrogen concentration and temporary catalyst deactivation. A method for the determination of pressure boundary conditions at the PAR exits was proposed and implemented into a CFD code. In this way, transient operation of PAR could be simulated without the need to model gas circulation outside the device. It was found that first a slow downward flow of gas is developed, which may persist until the temperature of the catalyst foils rises. As soon as the gas inside the PAR absorbs enough heat to become lighter than the gas outside the PAR, it starts to flow upwards. Criteria for determining the start-up time of PAR were proposed. Model predictions were also compared with experimental data obtained in tests conducted at the THAI facility.

Open access

Agnieszka Podstawczyńska and Scott D. Chambers

Abstract

An economical and easy-to-implement technique is outlined by which the mean nocturnal atmospheric mixing state (“stability”) can be assessed over a broad (city-scale) heterogeneous region solely based on near-surface (2 m above ground level [a.g.l.]) observations of the passive tracer radon-222. The results presented here are mainly based on summer data of hourly meteorological and radon observations near Łodź, Central Poland, from 4 years (2008–2011). Behaviour of the near-surface wind speed and vertical temperature gradient (the primary controls of the nocturnal atmospheric mixing state), as well as the urban heat island intensity, are investigated within each of the four radon-based nocturnal stability categories derived for this study (least stable, weakly stable, moderately stable, and stable). On average, the most (least) stable nights were characterized by vertical temperature gradient of 1.1 (0.5)°C·m−1, wind speed of ~0.4 (~1.0) m·s−1, and urban heat island intensity of 4.5 (0.5)°C. For sites more than 20 km inland from the coast, where soils are not completely saturated or frozen, radon-based nocturnal stability classification can significantly enhance and simplify a range of environmental research applications (e.g. urban climate studies, urban pollution studies, regulatory dispersion modelling, and evaluating the performance of regional climate and pollution models).

Open access

Kamil Wieprzowski, Marcin Bekas, Elżbieta Waśniewska, Adam Wardziński and Andrzej Magiera

Abstract

Radon Rn-222 is a commonly occurring natural radionuclide found in the environment from uranium-radium radioactive series, which is the decay product of radium Ra-226. The presence of radon carries negative health effects. It is, in fact, classified as a carcinogen, and therefore, it is necessary to continuously monitor its concentration. The aim of this study was to determine the level of radon-222 concentration in water intended for human consumption in the two voivodeships of Poland: West Pomeranian and Kuyavian-Pomeranian. Measurements were performed for more than 60 intakes. The level of radon was measured by using the liquid scintillation counting method. The range of measured radon concentration in the water from the West Pomeranian Voivodeship was from 0.90 to 11.41 Bq/dm3 with an average of 5.01 Bq/dm3, while that from the Kuyavian-Pomeranian Voivodeship was from 1.22 to 24.20 Bq/dm3 with an average of 4.67 Bq/dm3. Only in three water intakes, the concentration of radon-222 exceeded the value of 10 Bq/dm3. The obtained results allowed to conclude that population exposure associated with radon-222 in water is negligible and there is no need to take further action. In the case of three intakes where a higher concentration of radon was found, the potential exposure was low.

Open access

Natalia Golnik and Maciej G. Maciak

Abstract

The paper discusses the theoretical background in terms of the use of in-phantom recombination chambers in mixed radiation fields, with special attention paid to the question of how the experimentally determined, linear-energy-transfer-dependent (LET) parameters can be applied with regard to the more accurate determination of the chamber response and absorbed dose in mixed radiation fields. Methods of taking the recombination index of radiation quality (RIQ) measurements and theoretical consideration concerning the determination of the absorbed dose are described. Classical Bragg-Gray and Spencer-Attix cavity theories were analysed and their relationship to in-phantom recombination chambers was specifi ed. Methods concerning the estimation of correction factors with regard to RIQ measurements and their importance are highlighted.

Open access

Stanisław Kilim, Elżbieta Strugalska-Gola, Marcin Szuta, Marcin Bielewicz, Sergej I. Tyutyunnikov, Walter I. Furman, Jindra Adam and Vladimir I. Stegailov

Abstract

Neptunium-237 samples were irradiated in a spallation neutron field produced in accelerator-driven system (ADS) setup QUINTA. Five experiments were carried out on the accelerators at the JINR in Dubna - one in carbon (C6+), three in deuteron, and one in a proton beam. The energy in carbon was 24 GeV, in deuteron 2, 4 and 8 GeV, respectively, and 660 MeV in the proton beam. The incineration study method was based on gamma-ray spectrometry. During the analysis of the spectra several fission products and one actinide were identified. Fission product activities yielded the number of fissions. The actinide (Np-238), a result of neutron capture by Np-237, yielded the number of captures. The main goal of this work was to find out if and how the incineration rate depended on parameters of the accelerator beam.