| 1. |
- Bosland, L., et al.
(author)
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Iodine-paint interactions during nuclear reactor severe accidents
- 2014
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In: Annals of Nuclear Energy. - : Elsevier BV. - 0306-4549 .- 1873-2100. ; 74:C, s. 184-199
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Journal article (peer-reviewed)abstract
- To assess the radiological consequences of a severe reactor accident, it is important to be able to predict the behaviour of iodine in containment. Some interactions between iodine and containment paint (e.g., adsorption) have been well known for a long time. However, in recent years, new phenomena have been identified that can affect the gas phase iodine concentration in the longer term (e.g., the release of molecular iodine and organic iodides from irradiated painted surfaces). Several international collaborations and organizations around the world are currently addressing different aspects of this topic, including laboratory experiments and theoretical studies (ab initio) designed to improve the mechanistic understanding of the phenomena. Knowledge of the underlying mechanisms will provide explanations for behavioural differences observed between paint types, and will support the extrapolation of laboratory results to the safety analyses of nuclear reactors. The purpose of this paper is to present a selection of recent work performed by Severe Accident Research Network (SARNET) members regarding iodine-paint interactions and paint aging in order to improve the common understanding and better define what has still to be done in this area. The Severe Accident Research Network (SARNET) provides a framework within which members can share and discuss results.
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| 2. |
- Dickinson, S., et al.
(author)
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Experimental and modelling studies of iodine oxide formation and aerosol behaviour relevant to nuclear reactor accidents
- 2014
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In: Annals of Nuclear Energy. - : Elsevier BV. - 0306-4549 .- 1873-2100. ; 74, s. 200-207
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Journal article (peer-reviewed)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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| 3. |
- 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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| 4. |
- Prochazkova, L., et al.
(author)
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Gamma-radiolytic preparation of multi-component oxides
- 2016
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In: Radiation Physics and Chemistry. - : Elsevier BV. - 1879-0895 .- 0969-806X. ; 124, s. 68-74
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Journal article (peer-reviewed)abstract
- The preparation of solid precursors to Zn1-XCdXO and (Lu,Y)(3)Al5O12:Ce induced by Co-60 gamma-ray irradiation of aqueous solutions containing soluble metal salts and ammonium formate is presented: Due to the irradiation, crystalline zinc carbonate hydroxide Zn-4(CO3)(OH)(6). H2O or amorphous carbonates of Lu, Y and Al were formed in the solutions. After calcination at 500 degrees C, the agglomerated phase-pure Zn1-XCdXO with crystallite size about 50 nm was obtained if the Cd concentration in solutions remained below 16 M% (with respect to Zn) with x being up to 0.035. The solid precursors to garnets contained the intended concentration of all elements, according to X-ray fluorescence analysis. After calcination at 1200 degrees C in mild vacuum, the respective phase-pure garnets with crystallite size 100 nm or their solid solution were produced when the Ce dopation was kept below 2 M% (with respect to rare-earth metals). The Ce solubility in the garnet lattice was estimated as 1-2 M% at the calcination conditions used.
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| 5. |
- Tietze, Sabrina, 1986, et al.
(author)
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Formation of organic iodides from containment paint ingredients caused by gamma irradiation
- 2013
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In: Journal of Nuclear Science and Technology. - : Informa UK Limited. - 0022-3131 .- 1881-1248. ; 50:7, s. 689-694
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Journal article (peer-reviewed)abstract
- The formation of volatile alkyl iodides other than methyl iodide during a serious nuclear reactor accident may have radiological significance. The hypothesis that radioactive alkyl iodides, other than methyl iodide, could form from paint solvents under the conditions of a serious nuclear accident in light water reactors (under boiling water reactor (BWR) and pressurised water reactor (PWR) conditions) was tested using stable elemental iodine, a gamma irradiator and gas chromatography equipment. It was found that methyl and isopropyl iodides were formed from the texanol ester, which is used in many modern water-based paints. Methyl, ethyl, propyl and butyl iodides were formed from a hydrocarbon solvent (white spirit) commonly used in paint products used in the past. These results suggest that further work on the formation and behaviour of the higher alkyl iodides (containing more than one carbon atom) under the conditions of a serious nuclear accident is justified.
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| 6. |
- Tietze, Sabrina, 1986
(author)
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Formation, partitioning and interactions of organic iodides under severe nuclear accident conditions
- 2012
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Licentiate thesis (other academic/artistic)abstract
- During severe nuclear reactor accidents such as Chernobyl or Fukushima large amounts of radioactive iodine can be released in form of inorganic and organic iodine species into the environment. Volatile radioactive iodine species are harmful to human health when inhaled. The radioactive iodine species are concentrated in the thyroid gland where their beta particles may disturb the function to regulate the metabolism and may even induce cancer. Significant amounts of volatile organic iodides can be formed from released iodine and organic molecules which are released from paint coatings (epoxy paint top coatings, zinc primer) applied on containment surfaces, as well as from cable insulation materials. These reactions are caused by the pyrolysis and radiolysis during a severe accident scenario in light water reactors (LWR). In this work the formation and behaviour of organic iodides was investigated together with the formation of volatile and semivolatile organic substances from paints. Methyl iodide, the most feasible volatile alkyl iodide in the containment, is distributed between the water pools and the containment gas phase in such a way that significant amounts remain in the gaseous phase for potential release into the environment. Some countries like Sweden use wet-scrubber filter to reduce potential iodine release. The currently used wet-scrubber solutions are very efficient for removing elemental iodine but assumed to be less reactive towards organic iodides, such as methyl iodide. Thus these highly volatile short-chained organic iodides are likely to be released. Alternatively the release of iodine and organic iodides from the containment in case of a containment failure could be limited by sorption of those species on paint films. To be able to improve current used filter systems and paint types the reactivity of the relevant iodine species with the paint ingredients needs to be understood. Paint ingredients, such as solvents, of different paint types, with main focus on Teknopox Aqua VA paint used at Ringhals 2 nuclear power plant in Sweden, were identified and their reactions with iodine were studied. It was shown that the composition of different paint types varies significantly both qualitative and quantitative. Paints have a complex, heterogeneous chemical matrix that changes its properties with time, temperature, humidity and under the influence of irradiation. The impact on the volatile source term of iodine of the same type of paint was shown to be site and paint film age specific. Thus, freshly painted paint coatings will have a different contribution on the volatile, organic iodides chemistry during a severe nuclear accident than a paint which was for longer time exposed to reactor conditions or which is of different type.
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| 7. |
- Tietze, Sabrina, 1986, et al.
(author)
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Identification of the chemical inventory of different paint types applied in nuclear facilities
- 2013
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In: Journal of Radioanalytical and Nuclear Chemistry. - : Springer Science and Business Media LLC. - 0236-5731 .- 1588-2780. ; 295:3, s. 1981-1999
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Journal article (peer-reviewed)abstract
- The floors, concrete walls and many of the metal surfaces in nuclear power plant containments are coated with zinc primers or paint films to preserve the metal surfaces and simplify decontamination in the containment after the occurrence of a severe nuclear incident or accident. A chemical examination of paint films from different nuclear installations out of operation, as well as current operating ones, reveals that different types of paints are used whose composition can vary significantly. Results obtained for one type of paint at a certain nuclear site are in most cases unlikely to be comparable with sites painted with another type of paint. During normal operation and particularly during nuclear accidents, the paints will degrade under the high temperature, steam and irradiation influence. As paint and its degradation products can act as sources and depots for volatile iodine compounds, the type and aging conditions of the paint films will have a significant impact on the source term of the volatile fission product iodine. Thus, great care should be taken when extrapolating any results obtained for the interaction of radioactive iodine with one paint product to a different paint product. The main focus of the study is a comparison of the chemical profile of paint films applied in Swedish nuclear power plants. Teknopox Aqua V A, an epoxy paint recently used at Ringhals 2, and an emulsion paint used in the scrubber buildings of Ringhals 1-4 are compared with a paint film from Barseback nuclear power plant unit 1 that had been aged under real reactor conditions for 20 years. In addition, two paint films, an emulsion and a gloss paint, used in an international nuclear fuel reprocessing facility, are compared with the paints from the Swedish nuclear power plants.
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| 8. |
- Tietze, Sabrina, 1986, et al.
(author)
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Synthesis of I-131 labelled iodine species relevant during severe nuclear accidents in light water reactors
- 2013
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In: Radiochimica Acta. - : Walter de Gruyter GmbH. - 0033-8230. ; 101:10, s. 675-680
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Journal article (peer-reviewed)abstract
- Methods for the small scale synthesis of I-131 labelled iodine species relevant to severe nuclear accidents in light water reactors have been developed. The introduced methods allow the synthesis of impurity free, volatile, inorganic elemental iodine and volatile, organic iodides such as methyl-and ethyl iodide, as well as butyl iodide, chloroiodomethane, allyl iodide and benzyl iodide with ease. The radioactive iodine containing products are sufficiently stable to allow their storage for later use. Due to their volatility the liquid species can be easily converted into gaseous species and thus can be used in research in liquid and gaseous phase. The primary motivation for the development of these synthesis methods is to study the behaviour of volatile iodine species under the conditions of a severe nuclear accident in a light water reactor. Thus, the chemicals involved in the synthesis are chosen in a way to not generate impurities (chlorine and organic solvents) in the products which interfere with competing reactions relevant during a severe nuclear accident. Teknopox Aqua VA epoxy paint, which is used in Swedish light water reactor containments, and its reactions with the produced iodine species are described. The synthesised iodine species undergo chemisorption on paint films. Different to elemental iodine, the organic iodides are non-reactive with copper surfaces. The sorbed iodine species are partly re-released mainly in form of organic iodides and not as elemental iodine when the exposed paint films are heat treated. The partitioning and hydrolysis behaviour of gaseous methyl-and ethyl iodide between containment gas phase and water pools is found to be similar. The methods have been designed to minimise the use of harmful materials and the production of radioactive waste.
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| 9. |
- Tietze, Sabrina, 1986
(author)
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The chemistry of organic iodides under severe nuclear accident conditions in LWRs
- 2015
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Doctoral thesis (other academic/artistic)abstract
- For many countries nuclear fission is an important part of their energy portfolio. However, a great concern is the occurrence of nuclear reactor accidents, which can result in the emission of radioactivity into the environment. It has been proven in the past that the release of radioactivity can have environmental and health effects both locally, as well as in more distant locations, including those in other countries. As a result, severe nuclear accidents are of interest even to those countries that do not use nuclear fission as an energy source. One of the most important volatile fission products is iodine. In the event of a severe nuclear reactor accident iodine can be released from nuclear fuel and enter the containment. Iodine can be in different inorganic and organic chemical forms. The volatility of some iodine species is of importance as this enables the iodine to escape from a nuclear power plant and result in exposure of the general public. Radioiodine is re-concentrated in the small but vital thyroid gland and can induce cancer. While inorganic forms of iodine can be retained and their release into the environment to a large extent be prevented, organic iodides cannot be retained with the same efficiency by the filter systems used today. In this work the processes by which organic iodides can be formed inside the containment were studied. To this end methods were developed to produce I-131 labeled organic iodides that were used in the experiments. The formation of alkyl iodides other than methyl iodide, such as ethyl-, isopropyl-, butyl- and benzyl iodide from organic materials present in reactor containments was observed. It was found that organic materials can act as sources of organic iodides, but also consume them. The ability of a paint to retain and to generate organic iodides was found to decrease with thermal ageing of the paint. The iodine chemistry in paint films was investigated and organic iodides were found to bind to hydroxyl groups to form alkyl ethers with the iodine leaving group not being chemically bonded. A modified epoxy paint formulation was developed that can capture and retain more iodine than the bisphenol-A based epoxy paint Teknopox Aqua VATM that is currently used in Sweden. The removal of organic iodides from gas streams using solid absorbers was investigated but found to be not sufficient. It was found that trialkyl phosphines are particularly able to capture gaseous organic bonded iodine in experiments simulating the conditions in a Venturi scrubber.
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