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Sökning: WFRF:(Auvinen A) > Chalmers tekniska högskola

  • Resultat 1-6 av 6
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1.
  • Dickinson, S., et al. (författare)
  • Experimental and modelling studies of iodine oxide formation and aerosol behaviour relevant to nuclear reactor accidents
  • 2014
  • Ingår i: Annals of Nuclear Energy. - : Elsevier BV. - 0306-4549 .- 1873-2100. ; 74, s. 200-207
  • Tidskriftsartikel (refereegranskat)abstract
    • Plant assessments have shown that iodine contributes significantly to the source term for a range of accident scenarios. Iodine has a complex chemistry that determines its chemical form and, consequently, its volatility in the containment. If volatile iodine species are formed by reactions in the containment, they will be subject to radiolytic reactions in the atmosphere, resulting in the conversion of the gaseous species into involatile iodine oxides, which may deposit on surfaces or re-dissolve in water pools. The concentration of airborne iodine in the containment will, therefore, be determined by the balance between the reactions contributing to the formation and destruction of volatile species, as well as by the physicochemical properties of the iodine oxide aerosols which will influence their longevity in the atmosphere. This paper summarises the work that has been done in the framework of the EC SARNET (Severe Accident Research Network) to develop a greater understanding of the reactions of gaseous iodine species in irradiated air/steam atmospheres, and the nature and behaviour of the reaction products. This work has mainly been focussed on investigating the nature and behaviour of iodine oxide aerosols, but earlier work by members of the SARNET group on gaseous reaction rates is also discussed to place the more recent work into context.
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2.
  • Kajan, Ivan, 1984, et al. (författare)
  • Effect of nitrogen compounds on transport of ruthenium through the RCS
  • 2017
  • Ingår i: Journal of Radioanalytical and Nuclear Chemistry. - : Springer Science and Business Media LLC. - 0236-5731 .- 1588-2780. ; 311:3, s. 2097-2109
  • Tidskriftsartikel (refereegranskat)abstract
    • Ruthenium is a fission product that can be released from the fuel in case of a severe nuclear accident. In this work the impact of the atmosphere composition, including air radiolysis products, on the transport of ruthenium through a primary circuit was examined. Experiments were performed at temperatures 1300, 1500 and 1700 K in a slightly humid air. In the experiments significant effect of nitrogen oxides (N2O, NO2) and nitric acid on the ruthenium chemistry in the model primary circuit was observed. The obtained results indicate a strong effect of air radiolysis products on the quantity partitioning of transported ruthenium to gaseous and aerosol compounds.
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3.
  • Kajan, Ivan, 1984, et al. (författare)
  • Impact of Ag and NOx compounds on the transport of ruthenium in the primary circuit of nuclear power plant in a severe accident
  • 2017
  • Ingår i: Annals of Nuclear Energy. - : Elsevier BV. - 0306-4549 .- 1873-2100. ; 100, s. 9-19
  • Tidskriftsartikel (refereegranskat)abstract
    • Ruthenium is a semi-volatile element originating as a fission product in nuclear reactors that can be released in case of a severe nuclear accident. In this work, the impact of atmosphere composition on the transport of ruthenium through the primary circuit was examined. The effects of silver nanoparticles representing aerosols and NO2 gas as a product of air radiolysis were studied. Quantification of ruthenium transported both as gas and aerosol was performed. Chemical composition of ruthenium species was evaluated. The transport of gaseous ruthenium through the facility increased significantly when NO2 gas was fed into the atmosphere. When both silver aerosols and NO2 were fed into the atmosphere, the transport of ruthenium in gaseous and aerosol forms was promoted. It was concluded that the composition of atmosphere in the primary circuit will have a notable effect on the speciation of ruthenium transported into the containment building during a severe accident and thus on the potential radioactive release to the environment.
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4.
  • Karkela, T., et al. (författare)
  • Ruthenium transport in an RCS with airborne CsI
  • 2017
  • Ingår i: Progress in Nuclear Energy. - : Elsevier BV. - 0149-1970. ; 99, s. 38-48
  • Tidskriftsartikel (refereegranskat)abstract
    • Ruthenium is one of the most radiotoxic fission products which can be released from fuel as ruthenium oxides in an air ingress accident at a nuclear power plant. In this study it was found that the transport of the released ruthenium oxides through a reactor coolant system into the containment building is significantly affected by the atmospheric conditions. Airborne CsI increased the transport of gaseous ruthenium compared with that in a pure air atmosphere. The overall transport of ruthenium increased with temperature. In order to understand the behaviour of ruthenium in accident conditions, it is important to widen the experimental conditions from pure air/steam atmospheres to more realistic mixtures of prototypic gases and aerosols.
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5.
  • Kärkelä, T, et al. (författare)
  • Gas phase reactions of organic iodine in containment conditions
  • 2010
  • Ingår i: International Congress on Advances in Nuclear Power Plants 2010, ICAPP 2010. - 9781617386435 ; 2, s. 1084-1091
  • Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
    • In case of a hypothetical severe accident it is very likely that iodine at least partly deposits on painted walls of a reactor containment building. Iodine may react with painted surfaces to form organic iodine species. These organic species are a possible source of volatile iodine, which may increase the fraction of releasable iodine. Therefore, it is important to study the transport of organic iodine in containment conditions. Another question is, in which form are the organic iodides transported as gaseous molecules or as aerosol particles resulting from organic iodides reacting with radiolysis products. To answer this last question methyl iodide was fed into the EXSI facility in an air mixture. In some experiments the flow contained also humidity. The reactions took place in a quartz tube heated either to 50°C, 90°C or 120°C. UV-light was used as a source of radiation to produce ozone from oxygen. A separate generator was also applied to reach higher ozone concentrations. Nucleated aerosol particles were collected on plane filters and gaseous iodine species were trapped in trapping bottles. Aerosol mass flow rate and size distribution as well as speciation of gaseous reaction products were measured with several on-line instruments. Collected aerosol particles were analysed with SEM. It was found that the formation of aerosol particles was very fast when ozone and methyl iodide were present in the facility. Even a very low concentration of ozone produced high number concentration of particles. The measured aerosol mass concentration increased with increasing temperature and ozone concentration. Because the particle diameter was quite small (
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6.
  • Kärkelä, T, et al. (författare)
  • Nordic Collaboration: Impact of Ag and NOx Compounds on the Transport of Ruthenium in the Primary Circuit of NPP in a Severe Accident
  • 2016
  • Ingår i: 25th International Conference Nuclear Energy for New Europe, (Nene 2016); proccedings eds. Snoj, L; Lengar, I.. - 9789616207409 ; , s. no. 802-
  • Konferensbidrag (refereegranskat)abstract
    • When ruthenium is released from the fuel as ruthenium oxides to the environment in a severe NPP accident, ruthenium isotopes Ru-103 and Ru-106 cause a radiotoxic risk to the population both in a short and long term. As the previous international studies on the transport of ruthenium in the reactor coolant system (RCS) have mainly been conducted in pure air-steam atmospheres, the current study was dedicated to air ingress conditions with representative airborne air radiolysis (NOx) and control rod (Ag) species which were mixed with vaporized Ru oxides. The aim was to study the impact of these additives on the transport of ruthenium as gas and particles through the primary circuit of nuclear power plant in a severe accident. As a main outcome, the transport of gaseous ruthenium through the facility increased significantly when the oxidizing NO2 gas was fed into the atmosphere.
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  • Resultat 1-6 av 6

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