Experimental and modelling studies of iodine oxide formation and aerosol behaviour relevant to nuclear reactor accidents

Dickinson, S.; Auvinen, Ari; Ammar, Yousry A.; Bosland, L.; Clément, Bernard; Funke, F.; Glowa, Glenn A.; Kärkelä, Teemu; Powers, D.A.; Tietze, Sabrina; Weber, G.; Zhang, S.

doi:10.1016/j.anucene.2014.05.012

Cited by 26 publications

(14 citation statements)

References 23 publications

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“…However, besides it significant role in the depletion of ozone from the troposphere, [12][13][14] reactivity of iodine is also relevant for nuclear safety. [15][16][17] As a matter as fact, iodine species can be found inside the containment of a pressurized water reactor, in the case of a core melt accident.…”

Section: Introductionmentioning

confidence: 99%

Reactivity of Hydrogen Peroxide with Br and I Atoms

et al. 2018

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The reaction mechanisms of Br and I atoms with HO have been investigated using DFT and high-level ab initio calculations. The H-abstraction and OH-abstraction channels were highlighted. The geometries of the stationary points were optimized at the B3LYP/aug-cc-pVTZ level of theory, and the energetics were recalculated with the coupled cluster theory. Spin-orbit coupling for each halogenated species was also explicitly computed by employing the MRCI level of theory. Thermochemistry for HOBr and HOI has been revised and updated standard enthalpies of formation at 298 K for HOBr and HOI are the following: ΔH°(HOBr) = (-66.2 ± 4.6) kJ mol and ΔH°(HOI) = (-66.8 ± 4.7) kJ mol. The rate constants have been estimated using transition state theory (TST), canonical variational transition state theory (CVT), and CVT with small curvature tunneling (CVT/SCT) over a wide temperature range (250-2500 K). For the direct abstraction mechanism, the overall rate constant at 300 K was predicted to be 2.58 × 10 and 7.42 × 10 cm molecules for the Br + HO and I + HO reactions, respectively. The modified Arrhenius parameters have been estimated for the overall reactions: k(T) = 4.80 × 10 T exp(-5.51 (kJ mol)/RT) and k(T) = 3.41 × 10 T exp(-56.32 (kJ mol)/RT).

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Section: Introductionmentioning

confidence: 99%

Reactivity of Hydrogen Peroxide with Br and I Atoms

et al. 2018

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“…Gaseous iodine species (I 2 or CH 3 I) are produced in the upper ocean by marine organisms, such as macroalgae and phytoplankton. , Once released into the atmosphere, the gaseous species will undergo photolytic and ozonolysis reactions, resulting in their conversion into iodine oxides, as shown in Figure . − For instance, the reaction of I and IO with OH and HO 2 radicals led to the formation of HIO 2 species. Because of their possible implications in the destruction of the stratospheric ozone layer, − iodine oxides have drawn the attention of atmospheric chemists.…”

Section: Introductionmentioning

confidence: 99%

Thermochemistry of HIO₂ Species and Reactivity of Iodous Acid with OH Radical: A Computational Study

Khanniche

Louis

Cantrel

et al. 2017

ACS Earth Space Chem.

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This paper reports computations of thermochemical properties [Δf H 298 K °, S 298 K °, and C p = f(T)] of HIO2 isomers (HOOI and HOIO) together with the kinetic parameters of the gas-phase HOIO + OH reaction. The calculations are performed using the CCSD(T) method on structures previously optimized at the B3LYP/aug-cc-pVTZ level of theory. Spin–orbit coupling is computed by employing the CASSCF/CASPT2/RASSI scheme. The standard enthalpies of formation at 298 K are equal to −24.8 ± 0.9 and 18.7 ± 0.4 kJ mol–1 for HOIO and HOOI, respectively. The H- and O(H)-abstraction pathways are considered for the reaction of iodous acid (HOIO) with OH. Our calculations reveal that the H-abstraction channel was exergonic by −135 kJ mol–1 at 298 K. The rate constants were computed as a function of the temperature (250–2500 K) using classical and variational transition state theory. At the CCSD(T)/CBS level, the rate constants are (in cm3 molecule–1 s–1): k Habs(T) = 2.22 × 10–19 T 1.83 exp[−4.9 (kJ mol–1)/RT] and k OHabs(T) = 7.73 × 10–21 T 2.66 exp[−70.2 (kJ mol–1)/RT]. The HOIO + OH overall reaction is significantly dominated by the HOIO + OH → OIO + H2O channel for tropospheric temperatures. The atmospheric lifetime of HOIO is estimated to be approximately 64 years. Thermochemical properties and kinetic parameters derived from this study can be used as input parameters in chemistry-transport models, for which iodine is important in the case of radioactive airbone species released for a severe accident occurring to nuclear power plants.

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“…The presence of iodine in the atmosphere arises mainly from emissions of inorganic and organic compounds from microscopic (phytoplankton) and macroscopic marine plants. , The mechanism of reactive iodine release into the atmosphere appears to be particularly important for the destruction of vast amounts of ozone. − Volatile iodine will be emitted into the atmosphere of the containment of a nuclear power plant during a severe accident in which the normal core cooling is lost. − Air radiolysis products, such as ozone and hydroxyl and hydroperoxyl radicals, would react with volatile iodine to form iodine oxide species of different sizes, as represented in Figure . Small iodine oxides include IO, OIO, I 2 O 2 , and their hydrated counterparts (HOI and HOIO).…”

Section: Introductionmentioning

confidence: 99%

Investigation of the Reaction Mechanism and Kinetics of Iodic Acid with OH Radical Using Quantum Chemistry

Khanniche

Louis

Cantrel

et al. 2017

ACS Earth Space Chem.

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In this paper, the mechanism of the HOIO 2 + OH → products reaction is investigated using quantum chemistry tools. Two pathways are considered: HOIO 2 + OH → OIO 2 + H 2 O and HOIO 2 + OH → OIO + H 2 O 2 . The potential energy surfaces are calculated at the CCSD(T)/ CBS(D,T)//B3LYP/aug-cc-pVTZ level of theory. The OH radical was found to attack iodic acid from either the frontside (TS Habs ) or the topside (TS OHabs ), subsequently leading to Hor OH-transfer channels. Reaction enthalpies and standard Gibbs free reaction energies at 298 K are provided. The values indicate that only the HOIO 2 + OH → OIO 2 + H 2 O channel is exothermic and exergonic. Theoretical prediction of the kinetic parameters is performed within the framework of the transition state theory (TST) and variational transition state theory (VTST). The rate constants (in cm 3 molecule −1 s −1 ) for temperatures from 250 to 2500 K are k Habs (T) = 1.76 × 10 −22 T 2.39 exp(−3.5 (kJ mol −1 )/RT) and k OHabs (T) = 3.16 × 10 −21 T 2.57 exp(−96.2 (kJ mol −1 )/RT). The HOIO 2 + OH overall reaction is significantly dominated by the HOIO 2 + OH → OIO 2 + H 2 O channel for tropospheric temperatures. The main outcomes of this work are as follows: (i) The lifetime of iodic acid toward its removal by OH radicals is extremely long (1336 years), enabling its transportation to different locations around the Earth (marine, polar, and continental), as confirmed by recent field measurements; other possible loss pathways under clear sky (gas phase) and cloudy (aqueous phase) conditions could reduce its atmospheric lifetime. (ii) The thermochemical properties of the OIO 2 radical are provided: Δ f H 298 K

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Experimental and modelling studies of iodine oxide formation and aerosol behaviour relevant to nuclear reactor accidents

Cited by 26 publications

References 23 publications

Reactivity of Hydrogen Peroxide with Br and I Atoms

Reactivity of Hydrogen Peroxide with Br and I Atoms

Thermochemistry of HIO₂ Species and Reactivity of Iodous Acid with OH Radical: A Computational Study

Investigation of the Reaction Mechanism and Kinetics of Iodic Acid with OH Radical Using Quantum Chemistry

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Experimental and modelling studies of iodine oxide formation and aerosol behaviour relevant to nuclear reactor accidents

Cited by 26 publications

References 23 publications

Reactivity of Hydrogen Peroxide with Br and I Atoms

Reactivity of Hydrogen Peroxide with Br and I Atoms

Thermochemistry of HIO2 Species and Reactivity of Iodous Acid with OH Radical: A Computational Study

Investigation of the Reaction Mechanism and Kinetics of Iodic Acid with OH Radical Using Quantum Chemistry

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Thermochemistry of HIO₂ Species and Reactivity of Iodous Acid with OH Radical: A Computational Study