RD&D-Programme 2004 - SKB

4 Overview – technology development
Development of the technology for the KBS-3 method is currently in an intensive phase in
preparation for the upcoming permit applications for the encapsulation plant and the deep
repository. SKB’s strategy for the work is to focus on a reference design for each of the different
parts of the system. Vertical deposition, KBS-3V, is the reference for the design of the deposition
area in the rock. The work of designing the details follows a step-by-step process, where
the final choices for different parts are made as late as possible so that they can be based on the
most recent findings and investigations concerning alternative designs. Horizontal deposition of
the copper canisters, KBS-3H, is one such alternative. The final choices are based on an evaluation
of safety, technology, costs and environmental aspects.
Questions relating to canister and encapsulation technology are dealt with in Chapters 5–8.
Chapter 9 deals with the transportation of encapsulated spent nuclear fuel between the encapsulation
plant and the deep repository. The technology for building and operating the deep
repository is dealt with in Chapter 10, while the methodology for designing it is described in
Chapter 11. Finally, long-term observations and monitoring of the deep repository are discussed
in Chapter 12. Sections 4.1–4.8 contain short summaries of the programmes within each
technology area.
4.1 Canister fabrication
Copper tubes for canisters have been trial-fabricated using different methods such as roll
forming, extrusion, pierce and draw processing and forging. The trials show that these methods
are feasible for fabricating copper tubes. Various methods for casting the inserts are also being
tested and evaluated. The development work is continuing in order to improve the fabrication
technology, and SKB intends to report which methods are feasible for the future serial production
of canisters in connection with the permit application for the encapsulation plant. The
complete programme for canister fabrication and nondestructive testing of canister components
is presented in Chapter 5.
Fabrication of canisters will not take place at a single location. The inserts will be cast at
different foundries and the copper tubes will presumably be made at some plant that has the
requisite machinery. Machining of inserts and copper tubes will then take place at a machine
shop or in the canister factory, which is a special facility for assembly and final inspection of the
copper canisters before they are delivered to the encapsulation plant. The lids for the inserts and
the copper lids are also components that will be fabricated by an external supplier.
4.2 Sealing technology
SKB is currently working simultaneously to develop two welding methods to seal the copper
canisters: electron beam welding (EBW) and friction stir welding (FSW). Equipment for testing
of the two methods is in operation at the Canister Laboratory. The tests show that both methods
work. Development work is continuing on the sealing technology to ensure that at least one
method that meets the quality requirements will be available and that it can be used in serial
production.
Methods for nondestructive testing, above all ultrasonic and radiographic techniques, are also
being developed in the Canister Laboratory. Work on this and to establish acceptance criteria
will continue and be reported on in preparation for a permit application for the encapsulation
plant. The programme for sealing technology for the canister and nondestructive testing of the
sealing weld is described in Chapter 6.
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