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  • 1.
    Li, Junyi
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    Maier, Annika Carolin
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    Jonsson, Mats
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    Stability of Studtite in Aqueous Suspension - Impact of HCO3- and Ionizing Radiation on the Dynamics of DissolutionManuscript (preprint) (Other academic)
  • 2.
    Maier, Annika Carolin
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    Dynamics of Spent Nuclear Fuel Dissolution: Impact of Catalysis, Matrix Composition and Time Evolution2019Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Worldwide, nuclear power produces a large portion of the electricity that we consume every day. While nuclear energy comes with certain advantages, waste originating from its use is of particular concern. As of today, most countries are planning to store spent nuclear fuel in deep geological repositories to protect humans and the environment from this highly radiotoxic waste. Through a number of natural and engineered barriers, a repository is designed to remain intact and keep the radionuclides contained for millennia to come. To assess the safety of a repository, long-term predictions based on model systems are required. Given that one day the barriers of a repository fail, groundwater intrusion is inevitable. Once spent fuel is in contact with groundwater, the mobility of radionuclides in the environment is significantly enhanced. Spent nuclear fuel is a complex material which consists to around 95 % of UO2. The remainders are fission products and heavier actinides. In this thesis a bottom up approach is used to study dissolution of UO2 based model systems with a particular focus on dissolution induced by H2O2. H2O2 forms upon water radiolysis and can enhance UO2 dissolution. The mechanism for H2O2 consumption on metals and metal oxides is therefore revisited. It was found that the mechanism for catalytic decomposition of H2O2 on Pd differs from that on metal oxides. In addition, coumarin was demonstrated to be an efficient scavenger for reaction intermediates i.e. HO . To simulate longterm dissolution under repository conditions, UO2 and Gd-doped UO2 pellets were leached to reach high H2O2 exposures. Surface passivation reducing the dissolution of UO2 pellets was found to be accompanied by the formation of an oxidized layer. Studtite, a urnayl peroxide mineral can passivate the UO2 surface under certain conditions. Upon exposure to g-radiation studtite was found to dissolve readily, inhibiting passivation of real spent fuel by this surface precipitate.

    The full text will be freely available from 2020-02-01 17:48
  • 3.
    Maier, Annika Carolin
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    Barreiro Fidalgo, Alexandre
    Jonsson, Mats
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    H2O2 Induced Dissolution of (U1–xGdx)O2 Pellets in Aqueous Solution – Impact of H2 and Consecutive ExposuresManuscript (preprint) (Other academic)
  • 4.
    Maier, Annika Carolin
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    Benarosch, Anna
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Engineering.
    El Jamal, Ghada
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    Jonsson, Mats
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    Radiation induced dissolution of U3Si2 - A potential accident tolerant fuel2019In: Journal of Nuclear Materials, ISSN 0022-3115, E-ISSN 1873-4820, Vol. 517, p. 263-267Article in journal (Refereed)
    Abstract [en]

    To assess the integrity of the accident tolerant fuel candidate U 3 Si 2 under geological repository conditions, the kinetics of γ-radiation- and H 2 O 2 - induced oxidative dissolution was studied. The experiments were performed in aqueous solutions containing 10 mM HCO 3 − and in solutions without added HCO 3 − . The same experiments were also performed on UO 2 for comparison. All experiments were performed using powder suspensions. The experiments show that U 3 Si 2 is less than one order of magnitude more reactive towards H 2 O 2 than is UO 2 . The dissolution yield of U 3 Si 2 slightly exceeds the theoretical yield (23%). In experiments with consecutive additions of H 2 O 2 in HCO 3 − solutions, the reactivity remains constant implying that no significant amount of a secondary phase is formed on the U 3 Si 2 surface. The dissolution of Si closely follows that of U in HCO 3 − solution. In solutions without added HCO 3 − the reactivity towards H 2 O 2 is reduced by a factor less than 2. The dissolution is slightly slower than in HCO 3 − containing solutions but precipitation of U is observed after some time. The results of consecutive additions of H 2 O 2 to the HCO 3 − free system shows that the reactivity is decreasing for every addition. This indicates that a secondary phase is formed. XRD shows that the secondary phase is studtite. The irradiation experiments show that the surface area normalized radiation chemical yields for uranium dissolution for U 3 Si 2 and UO 2 in HCO 3 − solution differ by a factor 5–10 in favour of UO 2 . This difference can largely be attributed to the difference in dissolution yield.

  • 5.
    Maier, Annika Carolin
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    Herceglija Iglebaek, Ena
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry.
    Jonsson, Mats
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    Confirming the formation of hydroxyl radicals in the catalytic decomposition of H2O2 on metal oxides using coumarin as a probe2019In: ChemCatChem, ISSN 1867-3880, E-ISSN 1867-3899, Vol. 11, no 22, p. 5435-5438Article in journal (Refereed)
    Abstract [en]

    Hydrogen peroxide can be catalytically decomposed to O2 and H2O on metal oxide surfaces in contact with aqueous solutions containing H2O2. The initial step in this process has been proposed to be the formation of surface‐bound hydroxyl radicals which has recently been verified using tris as a radical scavenger. Here, we make use of the unique fluorescent product 7‐hydroxycoumarin formed in the reaction between hydroxyl radicals and coumarin to probe the formation of surface‐bound hydroxyl radicals. The experiments clearly show that 7‐hydroxycoumarin is formed upon catalytic decomposition of H2O2 in aqueous suspensions containing ZrO2‐particles and coumarin, thereby confirming the formation of surface‐bound hydroxyl radicals in this process. The results are quantitatively compared to results on the same system using tris as a probe for hydroxyl radicals. The effects of the two probes on the system under study are compared and it is concluded that coumarin has a significantly lower impact on the system.

  • 6.
    Maier, Annika Carolin
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    Jonsson, Mats
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    Pd‐Catalyzed Surface Reactions of Importance in Radiation Induced Dissolution of Spent Nuclear Fuel Involving H22019In: ChemCatChem, ISSN 1867-3880, E-ISSN 1867-3899Article in journal (Refereed)
    Abstract [en]

    To assess the influence of metallic inclusions (ϵ‐particles) on the dissolution of spent nuclear fuel under deep repository conditions, Pd‐catalyzed reactions of H2O2, O2 and UO22+ with H2 were studied using Pd‐powder suspensions. U(VI) can efficiently be reduced to less soluble U(IV) on Pd‐particles in the presence of H2. The kinetics of the reaction was found to depend on the H2 partial pressure at pH2≤5.1×10−2 bar. In comparison, the H2 pressure dependence for the reduction of H2O2 on Pd also becomes evident below 5.1×10−2 bar. Surface bound hydroxyl radicals are formed as intermediate species produced during the catalytic decomposition of H2O2 on oxide surfaces. While a significant amount of surface bound hydroxyl radicals were scavenged during the catalytic decomposition of H2O2 on ZrO2, no scavenging was observed in the same reaction on Pd. This indicates a different reaction mechanism for H2O2 decomposition on Pd compared to metal oxides and is in contrast to current literature. While Pd is an excellent catalyst for the synthesis of H2O2 from H2 and O2, a similar catalytic activity that was previously proposed for ZrO2 could not be confirmed.

  • 7.
    Maier, Annika Carolin
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    Kegler, Philip
    Klinkenberg, Martina
    Baena, Angela
    Finkeldei, Sarah
    Brandt, Felix
    Jonsson, Mats
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    High Surface Conversion UO2 - Leaching Experiments as Model for Long-term Leaching of Spent Nuclear Fuel Under Deep Repository ConditionsManuscript (preprint) (Other academic)
  • 8.
    Soroka, Inna
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    Bjervås, Jens
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH).
    Ceder, J.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH).
    Wallnerström, G.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH).
    Connan, Mallory
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH).
    Tarakina, N. V.
    Maier, Annika Carolin
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    Kiros, Yohannes
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Process Technology.
    Particle size effect of Ag-nanocatalysts deposited on carbon as prepared by γ-radiation induced synthesis2019In: Radiation Physics and Chemistry, ISSN 0969-806X, E-ISSN 1879-0895, article id 108370Article in journal (Refereed)
    Abstract [en]

    The effect of silver particle sizes on the catalytic performance of Ag/C electrodes for oxygen reduction reaction (ORR) was studied. The Ag particles were precipitated from AgNO3 solutions on Vulcan XC-72 carbon as support by γ-radiation induced synthesis method. The structural and morphological characterizations of the electrode materials were done by X-ray diffraction (XRD) and transmission electron microscopy (TEM). It was found that particles with smaller diameters, 11 ± 6 nm, possess higher catalytic activity for ORR (50 mA/cm2 at 0.3 V) as compared to those with larger diameters, 41 ± 5 nm, ORR activity is 25 mA/cm2 at 0.3 V. The observed effect may be explained by an increased amount of low coordinated atoms in smaller particles as compared to the larger ones.

  • 9. Xia, Songqin
    et al.
    Lousada, Claudio M.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics. KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Technology.
    Mao, Huahai
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Maier, Annika Carolin
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    Korzhavyi, Pavel A.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Sandström, Rolf
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Wang, Y.
    Zhang, Y.
    Erratum: Nonlinear oxidation behavior in pure Ni and Ni-containing entropic alloys (Front. Mater., (2018) 5, 53, 10.3389/fmats.2018.00053)2018In: Frontiers in Materials, ISSN 2296-8016, Vol. 5, article id 73Article in journal (Refereed)
    Abstract [en]

    In the original article, there was an error. An explanation should be inserted at the beginning of the section Thermodynamic Calculations, Paragraph 1, line 1: In this as well as the following paragraphs the authors refer to phases such as halite, spinel, corundum etc. It thereby solely referred to the structure type and not the respective mineral. In the original article, there was an error. The word "sfinancial" should be corrected to "financial" in the Acknowledgements section, Paragraph 1: The Carl Tryggers Stiftelse för Vetenskaplig Forskning is gratefully acknowledged for financial support. The authors apologize for these errors and state that they do not change the scientific conclusions of the article in any way. The original article has been updated.

1 - 9 of 9
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