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Workreport 2016-62

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Name:

Vesinäytteenoton kenttätyöohje – versio 5

Writer:

Alho, P., Kontula, A., Lamminmäki, T., Mäkinen, V., Parviainen, L., Uusitorppa, T., Weckman, K., Yli-Kaila, M.

Language:

Finnish

Page count:

52

Summary:

The chemical quality of groundwater is an important characteristic of a nuclear waste repository. The pH and Eh of  groundwater as well as the ammonium ion, chloride ion, sulphide ion and dissolved oxygen contents of groundwater influence the corrosion resistance of copper canisters used to final disposal of spent nuclear fuel. Redox conditions and pH as well as the quality and quantity of organic humic acid, fulvic acid, carbonates, phosphates, microbes and colloid species may influence the solubility and migration of radionuclides that may be released from the fuel. The results of groundwater chemistry samplings are used in local hydrogeochemical descriptions, in geochemical modelling and in safety analyses. Groundwater chemistry studies are an important part of the description of the site. The studies included in the description of the site (before called verifying location surveys or VARTU) were started in 2000. In 2003, VARTU studies were complemented with the Olkiluoto monitoring programme (OMO). Posiva's OMO aims at verifying that changes in groundwater hydrology, hydrogeochemistry and environment of the site are observed during the construction of ONKALO and final repository. The results of monitoring programme are reported annually, and programme will be developed based on experiences obtained and needs observed.

During the last years, several deep drillholes have been drilled at the survey area. Several groundwater samples are taken from these drillholes. The sampling aims at further defining the already obtained views on the groundwater chemistry of the different parts of the area. The samples are taken with a multi-packer, a double packer and pressurised water sampler system (PAVE) (Ruotsalainen et al 1996). With PAVE equipment it’s possible to take representative gas and microbe samples under the prevailing pressure conditions at the sampling depth. In addition, samples from specific fractures can be taken with PFL water sampler (Ripatti et. al 2014).

During the verifying location surveys that started at Olkiluoto in 2000, water samples were taken from deep drillholes, shallow drillholes, groundwater observation tubes and various types of environmental sampling points. Posiva started the construction of the underground research facility ONKALO in 2004. ONKALO started a new stage of water sampling: the water sampling points can be determined much more accurately in ONKALO than from ground level. Water samples are taken with all developed sampling methods. The method to be used is selected based on the sampling site and the sampling goals. At first, water samples were taken in order to determine the baseline state of Olkiluoto. At present, the groundwater chemistry survey results are mostly used to monitoring the changes caused by the construction of ONKALO and final repository, supplementing the hydrogeochemistry data and planing future samplings. The construction of underground facilities and the construction work at ground level both set new requirements for water sampling. Sampling points can be removed or added to the monitoring program based on the demands of the construction work.

In this field work instruction report, Posiva's water sampling methods and references to more specific instructions are presented.

Keywords:

Groundwater, chemistry, sampling, analysis, environment, equipment

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