Leaching of 14C in repository conditions: Transport and speciation

    Research output: Book/ReportReport

    Abstract

    Long-term exposure of materials in a repository may result in significant alterations in material structures. The activated decommissioning wastes including the reactor pressure vessel and its internals made of stainless steel, as well as, spent fuel claddings and reactor graphite contain nitrogen as impurity. 14C is generated as a result of nuclear reactions involving nitrogen (14N) or 13C atoms in these materials. 14C is one of the most important radionuclides when considering safe disposal of nuclear waste due to its long half-life. Both organic and inorganic carbons have been identified in leaching experiments with carbon containing steel, although clearly higher proportion is released as small organic molecules. The origin of these compounds and their reaction mechanisms is not fully understood. The specific iron-water experiments suggest that both the carbide carbon and the reduction of aqueous CO2 could be the sources of hydrocarbons in solution. Carbon analyses are highly sensitive to filtration which may cause incorrect results by either releasing or sorbing organic compounds. The filters should be cleaned by soaking in double distilled water (DDW) before use or at least to discard the initial filtration volumes. The best materials for DOC analysis are hydrophilic polyethersulphone and hydrophilic polypropylene membrane filters which induced least interference. In this literature research, it has become clear that there is very little conclusive knowledge and evidence on the form and fate of 14C in irradiated steel materials. A need for careful assessment of the different routes of 14C production in neutron-activated materials and its chemical form and transport is required.
    Original languageEnglish
    Place of PublicationEspoo
    PublisherVTT Technical Research Centre of Finland
    Number of pages42
    ISBN (Electronic)978-951-38-8096-5
    Publication statusPublished - 2014
    MoE publication typeNot Eligible

    Publication series

    SeriesVTT Technology
    Number157
    ISSN2242-1211

    Fingerprint

    Leaching
    Carbon
    Steel
    Nitrogen
    Decommissioning (nuclear reactors)
    Radioactive Waste
    Nuclear reactions
    Graphite
    Water
    Polypropylenes
    Spent fuels
    Stainless Steel
    Hydrocarbons
    Pressure vessels
    Organic compounds
    Radioisotopes
    Carbides
    Neutrons
    Iron
    Experiments

    Keywords

    • 14C
    • radiocarbon
    • carbon speciation
    • decommissioning waste

    Cite this

    Heikola, T. (2014). Leaching of 14C in repository conditions: Transport and speciation. Espoo: VTT Technical Research Centre of Finland. VTT Technology, No. 157
    Heikola, Tiina. / Leaching of 14C in repository conditions : Transport and speciation. Espoo : VTT Technical Research Centre of Finland, 2014. 42 p. (VTT Technology; No. 157).
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    abstract = "Long-term exposure of materials in a repository may result in significant alterations in material structures. The activated decommissioning wastes including the reactor pressure vessel and its internals made of stainless steel, as well as, spent fuel claddings and reactor graphite contain nitrogen as impurity. 14C is generated as a result of nuclear reactions involving nitrogen (14N) or 13C atoms in these materials. 14C is one of the most important radionuclides when considering safe disposal of nuclear waste due to its long half-life. Both organic and inorganic carbons have been identified in leaching experiments with carbon containing steel, although clearly higher proportion is released as small organic molecules. The origin of these compounds and their reaction mechanisms is not fully understood. The specific iron-water experiments suggest that both the carbide carbon and the reduction of aqueous CO2 could be the sources of hydrocarbons in solution. Carbon analyses are highly sensitive to filtration which may cause incorrect results by either releasing or sorbing organic compounds. The filters should be cleaned by soaking in double distilled water (DDW) before use or at least to discard the initial filtration volumes. The best materials for DOC analysis are hydrophilic polyethersulphone and hydrophilic polypropylene membrane filters which induced least interference. In this literature research, it has become clear that there is very little conclusive knowledge and evidence on the form and fate of 14C in irradiated steel materials. A need for careful assessment of the different routes of 14C production in neutron-activated materials and its chemical form and transport is required.",
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    Heikola, T 2014, Leaching of 14C in repository conditions: Transport and speciation. VTT Technology, no. 157, VTT Technical Research Centre of Finland, Espoo.

    Leaching of 14C in repository conditions : Transport and speciation. / Heikola, Tiina.

    Espoo : VTT Technical Research Centre of Finland, 2014. 42 p. (VTT Technology; No. 157).

    Research output: Book/ReportReport

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    Heikola T. Leaching of 14C in repository conditions: Transport and speciation. Espoo: VTT Technical Research Centre of Finland, 2014. 42 p. (VTT Technology; No. 157).