RD&D-Programme 2004 - SKB

Programme
Trial fabrication of all copper components will continue in order to verify the reliability of the
different methods and to further optimize the tools and the process parameters used in fabrication
as well as technical specifications concerning material requirements.
Seamless copper tubes will be fabricated by means of the three methods: extrusion, pierce and
draw processing and forging. Some tubes will be cut up for more thorough material studies.
The feasibility of fabricating copper tubes with integral bottoms by pierce and draw processing
will be further explored.
The feasibility of using ultrasound for grain size inspection in copper components will be
studied, see also section 7.2.
5.4 Trial fabrication
In order to further develop the fabrication technology for copper canisters with cast inserts,
fabrication trials have continued on a full scale in recent years in accordance with the guidelines
in RD&D 2001. The results are presented in a special report /5-9/.
5.4.1 Canister inserts
Altogether, 20 nodular iron inserts have been cast and evaluated so far. Six more inserts will be
fabricated and evaluated during 2004.
Conclusions in RD&D 2001 and its review
In RD&D 2001, SKB stated that casting of nodular iron inserts with an integral bottom has the
potential to develop into a workable method.
The authorities expressed the viewpoint that in order to achieve satisfactory results in the
casting of the insert, simulation programs should be run, see also section 5.3.1.
Furthermore, the opinion was offered that SKB should to a greater extent verify the mechanical
properties of the inserts by examining some fabricated inserts more thoroughly.
Newfound knowledge since RD&D 2001
Measures such as computer simulation of the casting processes and casting techniques at
each foundry for the purpose of improving material properties and reducing their variation
were discussed in section 5.3.1. Various improvements have been made in casting techniques.
Computer simulations and analyses at each individual foundry have led to a greater understanding
and improvements of such parameters as casting temperature and technique used in the
addition of small quantities of certain substances that control the shape and distribution of the
graphite in the finished insert.
Programme
The work of probabilistic analysis of the strength of the inserts will be concluded during 2004.
The results will serve as a basis for establishing acceptance criteria and optimizing technical
specifications.
Additional inserts for BWR assemblies will be cast and evaluated. A smaller number of inserts
for PWR assemblies will also be fabricated and analyzed. In conjunction with continued trial
fabrication, technical specifications and fabrication drawings for channel tubes and the welded
cassette will be further developed.
56 RD&D-Programme 2004