RD&D-Programme 2004 - SKB

5.6 Canister factory
SKB needs to have very good control of the empty canisters that are delivered to the encapsulation
plant. For this reason, SKB is planning to build its own canister factory. The most recent
planning report /5-8/ describes a reference design where blanks for all canister components are
delivered to the factory from different subcontractors. In the factory, the components will be
finish-machined, inspected and assembled to finished empty canisters, which will be transported
to the encapsulation plant.
The fundamental principle for the factory is still that handling of copper and nodular iron
are separated all the way up until the insert is lowered into the copper tube. The factory will
therefore contain two machining lines: one for machining of copper and one for machining
of nodular iron inserts and steel lids for inserts. Seamless, probably rough-machined hollow
copper billets are delivered to the factory from subcontractors. The tubes are fabricated by
means of one or more of the methods extrusion, pierce and draw processing and forging. Forged
and probably rough-machined blanks of copper for lids and bottoms are also delivered to the
factory from subcontractors. In the factory, the tubes, lids and bottoms are machined to specified
dimensions. After measurement, bottoms are welded onto the canister tubes and inspected by
nondestructive testing methods such as ultrasound and radiography. The step involving welding
of bottoms may become superfluous if the development of pierce and draw processing of tubes
with integral bottoms is successful.
In the other machining line, inserts and insert lids are turned. The inserts are delivered in the
cast and rough-machined state from various foundries. The insert lids are fabricated from rolled
steel plate. After measurements and cleaning of all parts, the insert is lifted down into the copper
tube. The finished canister is then placed in a special transport frame and delivered along with
an insert lid and a copper lid to the encapsulation plant.
The reliability of deliveries from various subcontractors is of fundamental importance for future
production in the canister factory. All components to be delivered to the canister factory must
meet SKB’s quality requirements. These are specified in an existing quality system for canister
fabrication which is certified to ISO 9001 and ISO 14001 and is progressively developed. One
step in the ongoing work of development of the quality system for canister fabrication is finding
the necessary network of suitable subcontractors and creating a long-term and businesslike
relationship with them. In conjunction with ongoing trial fabrication, suppliers are continuously
assessed by means of regular quality audits and analysis of pricing, delivery reliability and
probable future development.
Where the canister factory will be located has not yet been decided. Questions that must
be taken into consideration in the siting of the factory concern e.g. shipments to and from
the factory and societal aspects, such as availability of labour and industrial environment.
Alternatives to be studied include a siting in the same region as the encapsulation plant or the
deep repository, but other alternatives entirely may also be considered.
Conclusions in RD&D 2001 and its review
The design of the canister factory must be updated in the event of changes in fabrication
technology or canister design. SKI recommends that SKB continue to study whether possible
changes in the technology for machining of copper tubes and blasting of inserts, as well as the
allocation of what is done by suppliers and what is done in the canister factory, can improve
the quality of the delivered canisters. SKI has conducted its own analysis and assessment of
SKB’s investigation and planning of the canister factory /5-12/. The results indicate that SKB’s
proposed fabrication methods, choice of equipment and organization should result in a workable
system for canister fabrication. Further studies are recommended in some cases, however.
RD&D-Programme 2004 63