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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.

Open access

Md. Akhtaruzzaman and Pawel Kukolowicz

Abstract

Introduction: Commissioning of the treatment-planning system includes the accuracy of dose calculations in the inhomogeneous absorber. Several results of measurements with regard to inhomogeneity correction factors (CFs) have been published. However, the dependence of CFs on photon-beam energy may preclude such results from being applied to the photon beams of general users. Purpose: The aim of this study was to assess the dependence of CFs on the photon-beam energy. Materials and methods: CFs were calculated by the Batho method for several slab geometries comprised of concentrations of lung tissue and water of 0.25 and 1.00 g/cm3, respectively. The CFs were calculated at 6 MV (TPR20 10 = 0.67 ± k * 0.01) and 15 MV (TPR20 10 = 0.76 ± k * 0.01) where k = -3, -2, -1, 0, 1, 2, 3. All calculations were performed in the region where a charged-particle equilibrium exists. Results: Changes in CFs of less than 2% were observed across the considered energy ranges. With a change in TPR20,10 of 0.01, both at 6 and 15 MV at a depth of 5 cm below the lung; and lung thicknesses of 3, 5 and 8 cm over a fi eld surface area of 10 × 10 cm2, the change in CF never exceeded 2.4%. The dependences of changes in CFs in terms of TPR20,10 were 1.74% and 1.20% for field surface areas of 5 × 5 cm2 and 20 × 20 cm2, respectively. A comparison of 42 linear accelerators (LINACs) exhibiting 6 MV and 15 MV of energy installed in Poland showed that the maximum differences in terms of TPR20,10 at 6 MV and 15 MV were 4.2% and 2.2%, respectively. Conclusion: A linear dependence of CFs on energy was observed. According to observations, the smaller the surface area of the field and deeper the point of interest below the lung, the more dependent CFs are on energy.

Open access

Jefferson V. Bandeira and Lécio H. Salim

Abstract

The present work is a contribution to rescue the history of development of the application of 99mTc, widely used in nuclear medicine, to its use as tracer for the study of the transport of fine sediment in suspension, in water environment. It addresses the usefulness of its application in obtaining important parameters in environmental studies, illustrating them with some applications already performed and the results obtained. This kind of study, when associated with information on hydrodynamic parameters, for example, river, tidal, wind and wave currents, are powerful tools for the understanding and quantification of fine sediment transport in suspension. Fine sediment is an important vector in the transportation of heavy metals, organic matter and nutrients in water environment, and the quantitative knowledge of its behaviour is mandatory for studies of environmental impacts. Fine sediment labelled with 99mTc, can also be used to study the effect of human interventions, such as dredging of reservoirs, access channels and harbours, and the dumping of dredged materials in water bodies. Besides that, it can be used to optimize dredging works, evaluating the technical and economic feasibility of dumping sites and their environmental impact. It is a valuable support in the calibration and validation of mathematical models for sediment dynamics.

Open access

Metali Sarkar, Vikas K. Sangal, Haripada Bhunia, Pramod K. Bajpai, Harish J. Pant, Vijay K. Sharma, Anil Kumar and A. K. Naithani

Abstract

The pulp and paper industry is highly dependent on water for most of its processes, producing a significant amount of wastewater that should be treated to comply with environmental standards before its discharge into surface-water reservoirs. The wastewater generated primarily consists of substantial amounts of organic, inorganic, toxic and pathogenic compounds in addition to nutrients, which are treated in an effluent treatment plant that often combines primary, secondary, tertiary and advanced treatments. However, the treatment methods vary from industry to industry according to the process utilized. The effective performance of effluent treatment plants is crucial from both environmental and economic points of view. Radiotracer techniques can be effectively used to optimize performance and detect anomalies like dead zones, bypassing, channelling, etc. in wastewater treatment plants. Experiments on the distribution of residence time were performed on the aeration tank and secondary clarifier of a full-scale pulp and paper mill to study the flow behaviour as well as locate system anomalies and hence evaluate the performance of the treatment plants using the radiotracer I-131. The convolution method was applied to model the system with an imperfect impulse radiotracer input. The aeration tank was working efficiently in the absence of any dead zones or bypassing. Various hydrodynamic models available in the literature were applied on the aeration tank and secondary clarifier to obtain the hydraulic representation of the systems.

Open access

Ioan Valentin Moise, Mihaela Ene, Constantin Daniel Negut, Mihalis Cutrubinis and Maria Mihaela Manea

Abstract

Radiation sterilization has been considered a mass decontamination technique for biodegradable cultural heritage (CH) since its widespread application in the medical field. Initial experiments have revealed advantages, for example, efficiency and effectiveness, but also disadvantages, namely “side effects” concerning CH materials. More than 50 years later, the adequacy of ionizing radiation for some CH artefacts is still the subject of discussion. The main reason why is that science and industry are not yet able to provide a more efficient technique for treating mass decontamination. For wooden items, there is general agreement that the irradiation dose required for insect eradication is not damaging, even in the case of polychromed wood. For cellulose pulp (paper), there is a reduction in polymerization degree (DP) at the high doses necessary to stop the attack of fungi, but this should be considered taking into account the purpose of the treatment. Emergency or rescue treatments are necessary to mitigate the consequences of accidents or improper storage conditions. In some cases (archives), the value of written information is greater than the historical value of the paper support. For other materials, namely textiles, leather and parchment, less research has been published on the effect of ionizing radiation treatment. As a general rule, irradiation is not necessary when only a few CH elements are present that are affected by biological contamination since restorers can solve the problem by classical means. The need for radiation treatment arises when large collections (hundreds, thousands or even more elements) are heavily affected by the biological attack. In Romania, the IRASM gamma irradiator of IFIN-HH is receiving an increasing number of requests for CH treatment, mainly due to an intensive research programme concerning this topic and close liaison with CH owners or administrators. Besides reviewing the scientific results obtained in Romania and abroad, this paper presents some examples from experiences in Romania.

Open access

Stefania Baccaro and Alessia Cemmi

Abstract

Since the 1980s, research and qualification activities are being carried out at the 60Co gamma Calliope plant, a pool-type irradiation facility located at the Research Centre ENEA-Casaccia (Rome, Italy). The Calliope facility is deeply involved in radiation processing research and on the evaluation and characterization of the effects induced by gamma radiation on materials for different applications (crystals, glasses, optical fibres, polymers and biological systems) and on devices to be used in hostile radiation environment such as nuclear plants, aerospace and high energy physics experiments. All the activities are carried out in the framework of international projects and collaboration with industries and research institutions. In the present work, particular attention will be paid to the cultural heritage activities performed at the Calliope facility, focused on two different aspects: (a) conservation and preservation by bio-deteriogen eradication in archived materials, and (b) consolidation and protection by degraded wooden and stone porous artefacts consolidation.