RD&D-Programme 2004 - SKB

Already in the feasibility study, large areas were found to the west of the Simpevarp Peninsula
that warranted further investigations from a geoscientific point of view. The site investigation
was commenced here with geophysical airborne surveys and other studies so that an area could
be prioritized for drilling. An analysis revealed a number of areas with what could be judged to
be equivalent geological conditions. The Laxemar area just west of Simpevarp was therefore
prioritized due to its proximity to existing facilities on the Simpevarp Peninsula. Adhering to the
principle that the deep repository project should be pursued on a voluntary basis, SKB started
negotiations with the many concerned landowners to obtain access to the area. The negotiations
were drawn-out, but were finally more or less completed at the end of 2003. The work could
then start, nearly a year later than originally planned.
The aim is still to complete the current stage of the site investigation for both alternatives,
Simpevarp and Laxemar. After that an evaluation will be made, with the support of the collected
data. Contingent upon the results of the evaluation, the idea is to then carry out a complete
site investigation for one of the alternatives, see Figure 10. If the Simpevarp alternative is
prioritized, the investigations can be concentrated there. If the Laxemar area is chosen instead,
further investigations will be conducted there, and the prospects for a connecting tunnel from
Simpevarp will be explored.
In addition to the choice between the two subareas, a number of site-specific geoscientific
issues were identified as being of particular importance in the Oskarshamn case as well. Table 2
summarizes the current status of these issues, mainly with regard to the Simpevarp area, since it
is there that new borehole data are available.
Table 2. Current status of site-specific key issues identified prior to the start of the site investigation
in the site investigation in Oskarshamn.
Key issue
Size and location of bedrock blocks with
favourable properties at repository depth.
Presence and importance of dykes of
fine-grained granite and fracture zones,
particularly with respect to permeability.
Status
Drilling, in combination with lineament interpretations, show that
the Simpevarp subarea is probably surrounded by deformation
zones of such importance that they constitute boundaries for
a possible repository area. Within the area are lineaments
that can be interpreted as zones of lesser importance. Most of
the fractured formations in the boreholes exhibit relatively low
hydraulic conductivity.
Analyses of data from large areas adjacent to and west of
Simpevarp show that fine-grained granite is evenly distributed.
The dykes of fine-grained granite encountered in the boreholes on
the Simpevarp Peninsula have not exhibited elevated permeability,
compared with the surrounding rock.
A4.3 Facility design
Design is the collective term for activities where requirements, design-basis criteria, technical
solutions and other types of information are collected and processed so that they can eventually
be translated into facility descriptions, function descriptions, engineering drawings and
construction documents.
Prior to the site investigation phase, the results of the design work to date were compiled into
a comprehensive facility description outlining SKB’s general reference design of the deep
repository. The task during the site investigation phase is to produce site-adapted configuration
proposals and plans for detailed characterization and construction for the studied siting
alternatives. The starting point is the general reference design, which is progressively adapted
to the site conditions revealed by the investigations. At the same time, technical solutions for
subsystems and other results delivered by ongoing development work are implemented (see
section A4.4).
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