| 1. |
- Olsson, Mattias, 1975, et al.
(författare)
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Sorption of trivalent plutonium onto UO2 and the effect of the solid phase on the Pu oxidation state
- 2005
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Ingår i: Radiochimica Acta. ; 93, s. 341-346
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Tidskriftsartikel (refereegranskat)abstract
- A problem with plutonium in sorption studiesis its tendency to occur in a mix of oxidation states. Thiswork was a study of the sorption of plutonium on the solidphase UO2 in a perchlorate medium as a function of pH where plutonium is kept in its trivalent oxidation state.Experiments also showed that uranium(IV) oxide can reducePu(IV) to Pu(III) in an acidic solution and maintain it in thatstate. It was observed at the same time that the chemicallyinert solid phases TiO2 and ThO2 possibly increase the rateof disproportionation of Pu(IV) at a pH of about 0.5. Inaccordance with previous studies MnO2 was found to have anoxidizing effect, converting Pu(IV) into Pu(VI).A comparison is made between the sorption of Th(IV),Pu(III) and Co(II) on UO2 and TiO2, and Pu(VI) on TiO2.
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| 2. |
- Glänneskog, Henrik, 1975, et al.
(författare)
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Apparatus for on-line measurements of iodine species concentration in aqueous and gaseous phases
- 2003
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Ingår i: Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment. - 0168-9002. - 9904363455 ; 498:1-3, s. 517-521
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Tidskriftsartikel (refereegranskat)abstract
- An apparatus was constructed for on-line measurements of the concentration of iodine species in aqueous and gas phases using radioactive tracers. The apparatus and procedures for determining detector efficiencies and flow rates of both phases are described in detail. A complete description of experimental procedures is given and reactions between gaseous iodine and reactor containment construction materials such as copper, zinc and aluminium are investigated using the apparatus.
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| 3. |
- Glänneskog, Henrik, 1975
(författare)
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Interactions of I2 and CH3I with reactive metals under BWR severe-accident conditions
- 2004
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Ingår i: Nuclear Engineering and Design. - : Elsevier BV. - 0029-5493. ; 227:3, s. 323-329
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Tidskriftsartikel (refereegranskat)abstract
- I-2 released from fuel in the event of a severe nuclear reactor accident has the ability to deposit on surfaces in the containment building. This study has focused on the reactions of I-2 with reactive metals available in the containment. The experiments have been performed under conditions similar to those in a boiling water reactor at an accident situation. Copper, zinc and aluminium showed extensive uptake of gaseous I-2 under humid conditions. Reaction rates were determined at 25, 50 and 70degreesC and could be used for quantifying the effect of reactions between gaseous I-2 and copper, zinc and aluminium.Experiments with the metals placed in water showed lower I-2 uptake. Zinc iodide and aluminium iodide rapidly dissolves in water and no uptake of I-2 on these surfaces could be verified. Copper iodide has low solubility and I-2 was adsorbed on the surface.Experiments performed with reactive metals and methyl iodide showed a minor uptake of methyl iodide on zinc and aluminium in the gas phase for temperatures up to 80degreesC. A continuous uptake of methyl iodide on copper was measured at 80degreesC.
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| 4. |
- Glänneskog, Henrik, 1975
(författare)
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Interactions of iodine and methyl iodide with reactive metals
- 2003
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In the event of a severe nuclear reactor accident, iodine will be released from the fuel into the containment building. If released to the environment, iodine represents a biological hazard due to the concentration in the thyroid gland. Being a reactive element, iodine will undergo reactions with water, oxygen, organic material, surfaces etc. present in the containment. Large amounts of reactive metals like copper, zinc and aluminium present in a boiling water reactor are likely to react with iodine species in an accident situation. Experiments within this work have studied reactions of iodine and methyl iodide with these three metals under accident conditions.Copper, zinc and aluminium reacted similarly with gaseous iodine under humid conditions, with reaction rates of the same magnitude. The adsorption of iodine on theses surfaces could be divided into two steps; fast initial adsorption during less than one hour followed by slower adsorption during the rest of the experiment. Only the mass transfer of gaseous iodine to the metal surface limited the initial adsorption while the subsequent adsorption was limited by the diffusion of iodine through the metal iodide layer built up on the metal surface. Adsorption rates increased with temperature.Experiments with iodine and metals in water showed that copper only continuously adsorbed iodine on the surface. The solubility of zinc iodide and aluminium iodide is too high to allow an increasing metal iodide concentration on the surface.Zinc and aluminium only showed a minor uptake of methyl iodide on the surface for temperatures up to 80C. The uptake of methyl iodide on copper was low at 25 and 50C but continuously increased at 80C.
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| 5. |
- Glänneskog, Henrik, 1975
(författare)
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Iodine-Metal Surface Interactions under Severe Accident Conditions in a Nuclear Power Plant
- 2005
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In the event of a severe nuclear reactor accident, iodine will be released from the fuel and eventually enter the containment. Radioactive iodine isotopes constitute both an acute and a long-term threat to humans, owing to its half-life and its accumulation in the thyroid gland. To produce reliable models predicting the possible environmental exposure, it is crucial to consider the chemical reactions involving iodine in the containment. This work has been an effort to extend the knowledge of iodine chemistry during severe accidents by studying reactions between iodine and reactive metals present in the containment, metals that have as yet been little studied. In addition, the influence of radiation on iodine-metal interactions and the formation of iodine radiolysis products in the gas phase have been studied experimentally. Reactions between I2, CH3I and three metals (Cu, Zn and Al) were studied in a humid nitrogen atmosphere. I2 had a great affinity for all three metals, and adsorption rates as well as activation energies for the reactions could be determined. CH3I had an affinity only for Cu above 50ºC, and the adsorption rate was then several orders of magnitude lower than in the I2 case. Surface analysis showed that I2 and CH3I were chemisorbed as metal iodide. I2 was also retained on Cu in acidic solutions, with an adsorption rate about two orders of magnitude lower than the gas phase reactions. I2 was converted to I- on Al and Zn surfaces in acidic solutions. Conversion rate constants were determined for temperatures up to 140ºC. Mass spectrometry methods failed to identify iodine species formed through radiolysis reactions in air or nitrogen.
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| 6. |
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| 7. |
- Holm, Joachim, 1981, et al.
(författare)
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Deposition of RuO4 on various surfaces in a nuclear reactor containment
- 2009
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Ingår i: Journal of Nuclear Materials. - : Elsevier BV. - 0022-3115. ; 392:1, s. 55-62
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Tidskriftsartikel (refereegranskat)abstract
- During a severe nuclear reactor accident with air ingress, ruthenium can be released from the nuclear fuel in the form of ruthenium tetroxide. Hence, it is important to investigate how the reactor containment is able to reduce the source term of ruthenium. The aim of this work was to investigate the deposition of gaseous ruthenium tetroxide on aluminium, copper and zinc, which all appear in relatively large amounts in reactor containment. The experiments show that ruthenium tetroxide is deposited on all the metal surfaces, especially on the copper and zinc surfaces. A large deposition of ruthenium tetroxide also appeared on the relatively inert glass surfaces in the experimental set-ups. The analyses of the different surfaces, with several analytical methods, showed that the form of deposited ruthenium was mainly ruthenium dioxide. (C) 2009 Elsevier B.V. All rights reserved.
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| 8. |
- Kajan, Ivan, 1984, et al.
(författare)
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Impact of gamma radiation on the ruthenium deposited materials in a nuclear power plant
- 2016
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Ingår i: 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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Tidskriftsartikel (refereegranskat)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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| 9. |
- Kärkelä, T, et al.
(författare)
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Gas phase reactions of organic iodine in containment conditions
- 2010
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Ingår i: International Congress on Advances in Nuclear Power Plants 2010, ICAPP 2010. - 9781617386435 ; 2, s. 1084-1091
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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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| 10. |
- Pasi, Anna-Elina, 1993, et al.
(författare)
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Tellurium Behavior in the Containment Sump: Dissolution, Redox, and Radiolysis Effects
- 2020
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Ingår i: Nuclear Technology. - : Informa UK Limited. - 0029-5450 .- 1943-7471. ; , s. 1-11
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Tidskriftsartikel (refereegranskat)abstract
- In the event of a severe nuclear accident, one major concern is the release of radioactive material into the environment causing potential exposure of the general public to radiation. Among the volatile radionuclides are a range of tellurium isotopes. Due to the radioactivity and the volatility of tellurium, it has to be taken into account when assessing the overall effects of an accident. The interest in tellurium is not limited only to its release but also to the fact that some tellurium isotopes decay to iodine, and thus affect the iodine release behavior. The release and transport behavior of tellurium has been investigated over the past decades, however, the aqueous chemistry of tellurium in the complex containment sump system is still unclear. This study presents the behavior of tellurium dioxide in simplified containment sump conditions in relation to dissolution, redox reactions, and interactions with water radiolysis products. The results indicate that radiolysis products have a significant effect on tellurium chemistry in both a reducing and oxidizing manner depending on the solution composition. The redox reactions also affect the solubility of tellurium. The results show that the current information used to assess tellurium source term needs to be reevaluated for both severe accident management and for code validation purposes.
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