| 1. |
- Halleröd, Jenny, 1987, et al.
(author)
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Solubility Thermodynamics of CyMe-BTBP in Various Diluents Mixed with TBP
- 2018
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In: Journal of Solution Chemistry. - : Springer Science and Business Media LLC. - 0095-9782 .- 1572-8927. ; 47:6, s. 1021-1036
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Journal article (peer-reviewed)abstract
- The two organic ligands 6,6'-bis(5,5,8,8-tetramethyl-5,6,7,8-tetrahydrobenzo[1,2,4]triazin-3-yl)[2,2']bipyridine (CyMe-BTBP) and tri-butyl phosphate (TBP) have previously been investigated in different diluents for use within recycling of used nuclear fuel through solvent extraction. The thermodynamic parameters, , , and , of the CyMe-BTBP solubility in three diluents (cyclohexanone, octanol and phenyl trifluoromethyl sulfone) mixed with TBP have been studied at 288, 298 and 308 K, both as pristine solutions and pre-equilibrated with 4 molL nitric acid. In addition, the amount of acid in the organic phase and density change after pre-equilibration have been measured. The solubility of CyMe-BTBP increases with an increased temperature in all systems, especially after acid pre-equilibration. This increased CyMe-BTBP solubility after pre-equilibration could be explained by acid dissolution into the solvent. Comparing the and calculated using with the same parameters derived from a linear fit indicates temperature independence of all three thermodynamic systems. The change in enthalpy is positive in all solutions.
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| 2. |
- Kajan, Ivan, 1984, et al.
(author)
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Effect of nitrogen compounds on transport of ruthenium through the RCS
- 2017
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In: Journal of Radioanalytical and Nuclear Chemistry. - : Springer Science and Business Media LLC. - 0236-5731 .- 1588-2780. ; 311:3, s. 2097-2109
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Journal article (peer-reviewed)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.
(author)
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Impact of Ag and NOx compounds on the transport of ruthenium in the primary circuit of nuclear power plant in a severe accident
- 2017
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In: Annals of Nuclear Energy. - : Elsevier BV. - 0306-4549 .- 1873-2100. ; 100, s. 9-19
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Journal article (peer-reviewed)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. |
- Kajan, Ivan, 1984, et al.
(author)
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Impact of gamma radiation on the ruthenium deposited materials in a nuclear power plant
- 2016
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In: Journal of Radioanalytical and Nuclear Chemistry. - : Springer Science and Business Media LLC. - 0236-5731 .- 1588-2780. ; 309:2, s. 743-749
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Journal article (peer-reviewed)abstract
- © 2016 Akadémiai Kiadó, Budapest, Hungary During a severe nuclear accident ruthenium can form deposits on various surfaces inside the containment building in the form of ruthenium dioxide. Oxidizing air radiolysis products can interact with these deposits and volatilize ruthenium into the form of radiotoxic RuO4. The scope of this study was the gamma radiation induced re-vaporization of ruthenium from deposits on various materials representing surfaces inside the containment building. It was shown that humidity had an effect on the re-vaporization rates of ruthenium from epoxy paint. Some corrosion of various ruthenium deposited metal samples after gamma irradiation was also observed.
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| 5. |
- Kajan, Ivan, 1984, et al.
(author)
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Interaction of ruthenium tetroxide with iodine-covered surfaces of materials in nuclear reactor containment building
- 2016
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In: Journal of Nuclear Science and Technology. - : Informa UK Limited. - 0022-3131 .- 1881-1248. ; 53:11, s. 1889-1898
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Journal article (peer-reviewed)abstract
- Volatile iodine and ruthenium species are likely to be released from the fuel during a severe nuclear accident. Both iodine and ruthenium are expected to deposit on the surfaces in the containment building of the nuclear power plant. It is assumed that, due to the different release times from the fuel, ruthenium will reach the containment at the time when surfaces are already deposited with iodine species. The influence of ruthenium tetroxide on elemental iodine-covered surfaces in the containment of nuclear power plants was studied in this work. The ability of ruthenium tetroxide to oxidize iodine deposits on zinc, aluminum, copper and epoxy paint at high humidity conditions was evaluated. Quantification of both iodine and ruthenium deposits was done by the means of gamma spectroscopy. The chemical speciation of deposited elements was observed with SEM, XPS and EDX techniques. Experiments showed that ruthenium tetroxide oxidized iodine deposits into the volatile forms of iodine on zinc and aluminum samples and higher iodine oxides in the case of copper and epoxy paint samples. A major increase of ruthenium uptake on iodine-exposed surfaces in comparison to clean surfaces was observed.
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| 6. |
- Kajan, Ivan, 1984, et al.
(author)
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Interaction of ruthenium tetroxide with surfaces of nuclear reactor containment building
- 2016
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In: Journal of Nuclear Science and Technology. - : Informa UK Limited. - 0022-3131 .- 1881-1248. ; 53:9, s. 1397-1408
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Journal article (peer-reviewed)abstract
- © 2016 Atomic Energy Society of Japan. All rights reserved. During a severe nuclear accident, different fission products will be released from the nuclear fuel and some of them may eventually reach the containment building. Ruthenium is considered to be an important fission product due to the possible formation of volatile oxides. Radiotoxicity and chemical toxicity of the volatile ruthenium compounds present a considerable hazard during a severe nuclear accident. In this work, experiments regarding behavior of ruthenium tetroxide in the reactor containment were performed. The interactions of ruthenium tetroxide (RuO4) with zinc, copper, aluminum and epoxy paint in dry and humid atmosphere were examined. SEM/EDX (scanning electron microscope/energy-dispersive X-ray spectroscopy), XPS (X-ray photoelectron spectroscopy) and EXAFS (extended X-ray absorption fine structure) techniques were used to identify the chemical composition of the deposits formed after the interaction of RuO4 with the different materials. Additionally, distribution of ruthenium between different metals was examined. Interaction of RuO4 with the studied samples led to formation of dark, ruthenium-rich deposits. Examination of these deposits showed different chemical speciation of ruthenium on the surface when compared to the deeper layers of deposits. Interaction of RuO4 with zinc, copper and aluminum resulted to different amounts of the deposited ruthenium on the metals.
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| 7. |
- Kajan, Ivan, 1984
(author)
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RuO4 interaction with surfaces in the containment of nuclear power plant
- 2014
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Licentiate thesis (other academic/artistic)abstract
- During a severe accident different fission products will be released from the nuclear fuel and some of them may eventually reach the containment building. Ruthenium is considered to be an important fission product due to the possible formation of volatile oxides. Radiotoxicity and chemical toxicity of the volatile ruthenium compounds present a considerable hazard during the severe nuclear accident.In this work experiments regarding behavior of ruthenium tetroxide in the reactor containment were performed. Interaction of ruthenium tetroxide with zinc, copper, aluminium and epoxy paint in dry and humid atmosphere was examined. Several spectroscopic techniques were used to identify the chemical composition of the deposits formed after the interaction of RuO4 with different materials. Examination of the possible re-oxidation of ruthenium deposits to the volatile form by gamma radiation was also studied.Interaction of RuO4 with zinc, copper and aluminium had lead to different amounts of the deposited ruthenium among the metals. Most extensive deposition of RuO4 was observed on the aluminium metal. In dry atmosphere conditions preference of aluminium metal was very obvious. Deposits of ruthenium were identified to be a ruthenium dioxide on all metals. Speciation of the deposits formed on epoxy paint showed at least two different ruthenium species. One of them was identified to be probably a ruthenium dioxide, composition of the other one was not fully revealed.Experiments with the radiolytical re-vaporization of the ruthenium deposits from the epoxy paint indicated the release of ruthenium from the samples under the humid atmosphere. In the dry atmosphere re-vaporization of ruthenium wasn’t observed.The results showed how is ruthenium distributed between different materials in the containment. The chemical composition of the deposits was identified with use of different spectroscopic techniques. Dependence of re- vaporized ruthenium fraction on the received dose in the humid atmosphere was estimated.
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| 8. |
- Kajan, Ivan, 1984
(author)
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Transport and Containment Chemistry of Ruthenium under Severe Accident Conditions in a Nuclear Power Plant.
- 2016
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Doctoral thesis (other academic/artistic)abstract
- During a severe nuclear accident volatile elements and elements readily forming volatile compounds are the main concern regarding the release of radioactive material to the environment. As ruthenium is prone to form volatile oxides under severe nuclear accident conditions as well as having radiotoxic isotopes, it is one of the more important elements during such an accident.In this work the chemical behavior of ruthenium during the transport in the reactor cooling system and the chemistry of ruthenium within the containment was studied.Studies on ruthenium transport included the effect of temperature, air-radiolysis products and aerosols on the quantity and chemical form of transported ruthenium during an accident. During the experiments the temperature had significant effect both release and transport of ruthenium. Different air radiolysis products affected both quantity and physical form of the transported ruthenium.The other part of the studies was focused on the chemistry of ruthenium within the containment. These experiments aimed at the interaction of ruthenium tetroxide with metallic (Al, Cu, Zn) and epoxy paint covered surfaces within the containment. Ruthenium had great affinity towards these surfaces that led to the formation of ruthenium rich deposits and thus a clear retention. Chemical characterization as well as quantification of these deposits was obtained.The effect of gamma radiation on the formed ruthenium deposits was shown and re-volatilized fractions of ruthenium under different atmospheres and received doses were determined decreasing the retention significantly. Studies focused on interaction of ruthenium tetroxide with iodine-covered surfaces showed its ability to oxidize iodine deposit and re-volatilize iodine from the aluminum and zinc metals. Iodine covered surfaces were also proved to be an effective trap of ruthenium within the containment.Data obtained from these studies can be utilized for the better understanding of severe accident phenomenology and behavior of radionuclides during an accident.
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| 9. |
- Karkela, T., et al.
(author)
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RECENT FINDINGS ON RUTHENIUM CHEMISTRY IN A SEVERE ACCIDENT
- 2015
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In: Proceedings of the International OECD-NEA/NUGENIA-SARNET Workshop on the Progress in Iodine Behaviour for NPP Accident Analysis and Management.
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Conference paper (other academic/artistic)abstract
- The chemistry of radiotoxic ruthenium in a severe nuclear power accident has actively been investigated especially during the last decades. The Ru studies have covered the release from a fuel, the transport in the primary circuit and the behaviour in the containment building. The gathered experimental data have been utilized to understand the key parameters governing the Ru chemistry in a severe accident (SA) and to check the ability of the existing models of SA analysis codes to explain the experimental results. To further increase the knowledge on Ru behaviour, the collaboration on international level has been intensive. Lately, the widest and most active networks have been EU SARNET and EU SARNET2. The valuable effort of these networks on sharing information of e.g. national programs and on interpreting the experimental results is continued in EU NUGENIA program. More detailed studies on separate phenomena have been conducted e.g. as part of OECD/NEA STEM/START and ISTP/VERDON programs. Furthermore, Phébus FP tests have produced valuable data on integral phenomena.The large-scale integral and semi-integral experiments have confirmed that Ru release depends strongly on carrier gas. Ru is significantly released from an irradiated fuel sample under oxidizing conditions, in particular when air is involved. In addition, the oxidation of UO2 fuel seems to lead to a higher Ru release than in case of MOX fuel. Ruthenium can be transported to the containment atmosphere both in gaseous and particulate forms. The small-scale separate-effect experiments gave a detailed view on Ru transport. A high fraction of ruthenium was detected as particles at the outlet of the model primary circuit in an air atmosphere. However, the observed gaseous Ru fraction is higher than what could be expected based on thermodynamic equilibrium calculations. Further studies on the effect of flow residence time in a temperature gradient for the equilibrium of Ru oxides have been conducted.The effect of other fission products in the gas phase, as well as FP deposits on the surface of primary circuit, on the Ru transport has been investigated. For example, caesium containing deposits seemed to trap gaseous ruthenium effectively. Similarly in case of control rod residues, silver particles in the gas phase of the circuit acted as a sink for gaseous Ru. In an air ingress accident, the effect of air radiolysis products on the Ru chemistry becomes important. As the main air radiolysis products can be considered as oxidizing agents, their ability to oxidize the lower oxides of Ru to higher oxidation state has been examined.Most of Ru in the containment building ends up as deposits on the containment surfaces and in the sump. Experiments on the radiolytical revaporisation of ruthenium deposits on the epoxy paint surface indicated the release of gaseous ruthenium and it was enhanced under humid atmosphere and elevated temperature. It appeared that the products of air radiolysis caused by γ-radiation promoted the formation of gaseous ruthenium from Ru oxide deposits on paint in a higher amount than could be expected by pure ozone action. Concerning the irradiation tests of perruthenate aqueous solutions, they indicated the formation of gaseous Ru by γ-radiolysis products in solution.
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| 10. |
- Karkela, T., et al.
(author)
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Ruthenium transport in an RCS with airborne CsI
- 2017
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In: Progress in Nuclear Energy. - : Elsevier BV. - 0149-1970. ; 99, s. 38-48
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Journal article (peer-reviewed)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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| 11. |
- Kärkelä, T, et al.
(author)
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Nordic Collaboration: Impact of Ag and NOx Compounds on the Transport of Ruthenium in the Primary Circuit of NPP in a Severe Accident
- 2016
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In: 25th International Conference Nuclear Energy for New Europe, (Nene 2016); proccedings eds. Snoj, L; Lengar, I.. - 9789616207409 ; , s. no. 802-
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Conference paper (peer-reviewed)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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