RD&D-Programme 2004 - SKB

A2.3 System design
A2.3.1 Fundamental requirements, design premises
At a general level, the premises for designing and engineering the management system for
spent nuclear fuel are derived from Swedish laws and regulations, other requirements on safety,
and SKB’s own and other parties’ requirements on technical feasibility and efficiency. These
requirements are as a rule generally formulated and not directly applicable to optimization or
more concrete design work. They therefore have to be translated into performance requirements
on the system or its parts.
Performance requirements mainly apply to safety and radiation protection, other environmental
protection, construction and operation, and aspects that derive from international agreements.
The design and execution of the facilities must be shown to fulfil all of these requirements under
the design-basis stresses and loads. These stresses and loads are determined by analyzing the
situations and processes that occur or might occur during construction and operation, and in the
case of the deep repository after closure as well. They include e.g. static loads, deformations and
movements, corrosion, etc.
The work sequence in the waste programme, with regular accountings in the form of RD&D
programmes and safety assessments, has entailed a gradual development of the system, accompanied
by regular cross-checking with the requirements. In 2002, SKB submitted a status report
on the work of preparing design premises, see Chapters 5 and 11 with references. The report
covers the entire deep repository system and its parts, and also includes the sequence of derivations
that has been gone through to arrive at a useful design basis from general requirements.
The degree of precision and quantification provided by the report for the parameters, loads etc
that govern design and execution corresponds to the status of the work at the time of the report.
A2.3.2 System analysis and optimization
The overall strategy for designing and optimizing a repository system according to the KBS-3
concept has been presented in many contexts, most recently in RD&D-Programme 2001.
The principle is to gradually work out, in defined steps, an increasingly detailed design of the
facilities, requisite infrastructure and technical supply systems. Execution of construction and
operation are more precisely defined in the same way. As the design becomes increasingly
detailed, decisions are made which narrow down the range of options, first for general system
selection, then for technical solutions for facilities and subsystems, and finally for the details.
This mode of working has been successfully applied in many industrial projects, including SFR,
Clab and the NPPs.
Decisions and choices during the course of the process are made systematically by producing
possible alternatives and evaluating them against established requirements or other criteria with
regard to:
• Post-closure safety and performance.
• Safety during construction and operation.
• Environment.
• Feasibility and efficiency.
• Resource needs.
Final choices of system and technology solutions will be made as late as possible to in order
to take full advantage of technical advances and, in some cases, site-specific data as well.
However, the decisions must not be delayed so much that the development of other parts of
the system is held back or otherwise impaired by unclear premises. Striking a balance between
the advantages of retaining freedom of choice on the one hand and the need to drive the design
process towards the final goal at a reasonable pace on the other hand is a central consideration
in SKB’s strategic planning.
RD&D-Programme 2004 369