RD&D-Programme 2004 - SKB

11.3 Execution – stepwise design
Siting, construction and operation of the deep repository facility has been divided into phases:
the feasibility study phase, the site investigation phase, the construction phase and the operating
phase with initial and regular operation and closure. In different phases of the deep repository
project, design is supposed to deliver the documents that are required for a decision to be made
prior to the next phase.
Design of the deep repository facility is proceeding stepwise. The following account focuses
primarily on the design of the underground part. Prior to each new step in the design of the
underground part, methodology and premises are updated based on the execution of the
preceding step. In this way, the design of the underground part is progressively determined
and detailed as investigations of the rock and safety assessment furnish new information,
technology is developed and the facility is gradually built out. This stepwise information
gathering, decision-making, detailing and build-out lead to a gradual narrowing-down of the
freedom of action for changes.
Alternative non-site-adapted facility descriptions based on alternative layouts designated E were
prepared in the feasibility study phase. These layouts were intended to provide a clear picture of
what the construction of the deep repository facility entails and to serve as a basis for studying
which of the alternative layouts is/are preferable from the viewpoint of safety, environment and
effectiveness. Layout class E serves as the basis for the subsequent design step D.
Design step D was commenced when the site investigation phase began in 2002 and is intended
to serve as a basis for permit applications for the encapsulation plant and the deep repository,
and to proceed into the construction phase. The placement of the surface part of the facility and
the design and placement of access roads are determined in this step. A decision on the layout
of a part of the facility entails that the design of technical systems and installations in that part
of the facility are also determined to a great extent. This means that possible future changes are
limited.
The design continues during the construction phase with the preparation of main documents
for planned parts of the deep repository. Based on the engineering documents, new site data,
information from safety assessment and EIA and technology development, methodology and
premises are updated. Design in the construction phase then continues with the preparation of a
final layout and construction documents for the buildings and rock openings required for initial
operation.
Conclusions in RD&D 2001 and its review
SKB’s stepwise design model for the deep repository has been described in RD&D 98 and
RD&D 2001. The configuration of the repository is refined and documented as more knowledge
is obtained and the deep repository is progressively designed and controlling layout issues are
dealt with. This stepwise detailing gradually narrows down the freedom of action for changes. It
was observed that those parts that are built early should be configured so that sufficient freedom
of choice is retained for the configuration of parts that are built later.
Newfound knowledge since RD&D 2001
A methodology for how the design steps are to be carried out has been devised and the connections
between the documentation in each design phase have been established. The connections
include feedbacks from the design work and finished layouts to the site investigations and
different versions of the site models, as well as to safety assessment and EIA. The methodology
also prescribes how uncertainties in early information and early functional solutions are to be
estimated.
134 RD&D-Programme 2004