Variations in 234U/238U activity ratios in groundwater: A key to flow system characterisation?

Juhani Suksi (Corresponding Author), Kari Rasilainen, Petteri Pitkänen

    Research output: Contribution to journalArticleScientificpeer-review

    46 Citations (Scopus)


    Two key questions concerning geological disposal of high-level radioactive waste are (i) how robust is the barrier system during long term disturbances and (ii) do we know the possible disturbances well enough? One step towards answers is to study how groundwater flow systems have behaved in the past. Studying naturally occurring radioactive tracers in groundwater offers useful information. Uranium isotopes 234U and 238U are oft-used tracers. A characteristic of the 234U/238U activity ratio (AR) is its considerable variation in groundwater. It is known that the reason for variation is isotopic fractionation at the rock–water interface. However, the reason why AR varies in groundwater is not clear. We tried to answer this question by carefully examining the geochemical and nuclear chemical origins of U isotopic fractionation and by studying a large body of U data from Finnish and Swedish investigation sites. We found that despite large variations in AR and U concentrations, the respective 234U and 238U activities show a correlation which contains useful information of the flow system behaviour which is in line with other hydrochemical data.
    Original languageEnglish
    Pages (from-to)556-571
    Number of pages16
    JournalPhysics and Chemistry of the Earth: Parts A/B/C
    Issue number10-14
    Publication statusPublished - 2006
    MoE publication typeA1 Journal article-refereed
    EventThe 10th international conference on the chemistry and migration of actinides and fission products in the geosphere - Avignon, France
    Duration: 18 Sept 200523 Sept 2005


    • 234u/238u activity ratio
    • a-recoil
    • groundwater
    • U-series disequilibrium
    • glacial processes
    • groundwater flow
    • radionuclide migration
    • radionuclides
    • nuclear waste


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