Investigation of the potential impact of storage place on tissue free water tritium and organically bound tritium activity determination

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Baglan, N. | Ansoborlo, E. | Cossonnet, C. | Losset, Y. | Crozet, M.

Edité par CCSD ; EDP Sciences -

International audience. When focusing on environmental tritium measurement, water is the most common matrix, and monitoring is mainly concerned by tissue free water tritium (TFWT) and organically bound tritium (OBT) analysis. Moreover, in order to improve knowledge on tritium behaviour and migration, TFWT and OBT determinations are performed at low activity level. TFWT and OBT determinations could also be performed after incidental releases to determine potential impact to the environment and to man. As hydrogen isotopes are prone to isotopic exchange with atmospheric moisture, the key point when analysing TFWT and OBT is to ensure appropriate preservation of the sample from its sampling to its analysis. Aiming to answer to the following question does the storage condition could change activity level within the sample? An interlaboratory exercise was organized within the framework of a French tritium working group to follow both TFWT and OBT activity scrutinizing for any variation on a one-year period. For this study about 50 kg of grass were sampled, homogenized, packaged and frozen prior dispatching to the participants. Six aliquots were sent to each participating lab to determine both TFWT and OBT activity concentrations, starting when all the labs received the sample, continuing two weeks, one month, three months, six months and one year after to check for any variation in the measured activity concentration. The results were treated for each analysis date, for each participating lab and considering the overall population by calculating the mean and associated standard deviation. As all values are consistent, the main conclusion of this work is that TFWT and OBT activity concentrations remain constant when appropriate storage conditions are used. This point is of importance as sample conservation is always a critical parameter for tritium determination in environmental samples and also when considering the fabrication of certified reference materials.

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