On site: UV/VIS photography

All samples were given a unique identification ID and photographed in normal and ultra-violet light with high resolution digital imaging. In normal light, the structure of the shear zone against the rock matrix is easy to observe. Under UV light, the fluorescent tracers added to the epoxy resin before overcoring are used to distinguish the different flowpaths.

Normal (left) and UV light (right) photography of a section of the HPF shear zone. Sample width is 30cm. The thick vertical line through both images shows the borehole position.

The approximate location of the radionuclides within the leachate-altered shear zone and the approximate amount of radionuclides sorbed in each sample were then determined in a new Level C laboratory at the GTS, dedicated to radionuclide analysis. State of the art beta autoradiography (Fujifilm BAS1800i scanner) and gamma spectrometry (Ortec Poptop with Xcooler) were used to provide these preliminary, qualitative data which is then used to plan detailed sub-sampling.

The radioanalytical equipment employed in the analysis of the HPF core material.

Example of beta autoradiography on a section of HPF core material. The brighter areas show areas enriched in radionuclides from the tracer cocktail

Example of a gamma spectrum for a section of HPF core material

To look for the presence of cement leachates in the HPF core material using, the British Geological Survey examined the material using the PIMA analytical technique.

Operation of the PIMA system at the Grimsel Test Site and potential areas of sorption of cement leachates

The analysis of HPF core material currently continues at laboratories around the world. Further analysis ongoing includes

  • structural analysis
  • microscopy, XRD, SEM, EMPA
  • EMPA mineralogy mapping
  • Stepwise dissolution plus radionuclide and chemical analysis
  • Proposed: (A)TEM, ESEM, RAMAN, FTIR

The complete results of the in situ field test, the modelling and the laboratory tests will be brought together in a series of Nagra technical reports and papers. It is expected that these will be available by end 2006. To order a copy of the reports from Nagra click here.