Vibrometric’s over 2 decades experience in the Nuclear Waste Management field is mostly within Finland, the country being at the forefront in assessing, assigning and constructing Nuclear Repository Sites. It is an on-going Program in which Vibrometric has been the technological partner since its incipiency in the 80’s.

The Olkiluoto site has been selected amongst several candidate sites investigated in Finland for deep geological disposal of spent nuclear fuel.

From 1987 until 2001 preliminary and detailed site characterisation phases were completed.

Extensive geophysical data and imaging have been used to produce and refine a 3D model of the site.

An underground research facility, ONKALO, will be built at Olkiluoto for detailed characterisation of the planned nuclear waste repository host rock.

ONKALO will also be used for testing and demonstration purposes.

The main objective of the site investigations and related research has been to attain sufficient confidence in the plans for the final disposal operations.

The investigations focused on the identification of bedrock volumes suited for final disposal and on a detailed definition of the properties of these volumes.

Geophysics has had a significant contribution to the detailed characterization of the planned repository host rock.

• The initial site description stage, kilometer scale
  • Surface reflection: 3-D setup needed, difficulties with the thick overburden.
  • VSP: each subsequent survey adds information from other regions of the site, until a complete and iteratively validated model is obtained.
  • With VSP, the initial coverage is less, and the angular coverage is more complete than with surface reflection.
• The construction phase, medium scale 50 - 500 m
  • Layouts used: VSP, HSP (tunnel), Crosshole
  • Relatively large investigation distance
  • Ability to predict the 3-D geometry of the rock structures
  • Model built by joint interpretation of reflection and transmission data
  • Geometrical model of the rock features (Reflection)
  • Character of the features (Transmission)
• The completion stage, small scale
  • Seismic results directly compared with rock mechanical and hydraulical data