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Summary:
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As a part of the site investigations for the disposal of spent nuclear fuel, hydraulic conductivity measurements were carried out with HTU-equipment in drillholes OL KR40, OL KR42 and OL KR45 at Eurajoki, Olkiluoto. The objective was to investigate the distribution of the hydraulic conductivity in the surrounding bedrock volume. Measurements were carried out during 2007.
The total length of the borehole OL-KR40 is 1030,00 m, 405,96 m of which was cov-ered by 203 standard tests with 2 m packer separation as specified in the measurement plan. Respectively, OL-KR42 is 400,85 m long and 51 similar tests were made in it covering 102,00 m of the hole and OL-KR45 1023,30 m long, 152 tests made covering 304,00 m. The measured sections are around the depths of the planned repository. Double-packer constant-head method was used throughout with nominal 200 kPa overpressure. Injection stage lasted normally 20 minutes and fall-off stage 10 minutes. The tests were often shortened if there were clear indications that the hydraulic conductivity is below the measuring range of the system. The pressure in the test section was let to stabilise at least 5 min before injection. In some test sections the test stage times were extended. Two transient (Horner and 1/Q) interpretations and one stationary-state (Moye) interpretation were made in-situ immediately after the test.
Some tests with extended duration of the injection were made simultaneously recording pressures in near by plugged holes. The objective was to confirm the hydraulic connections between the holes.
The Hydraulic Testing Unit (HTU-system) is owned by Posiva Oy and it was operated by Geopros Oy.
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