RD&D-Programme 2004 - SKB

Newfound knowledge since RD&D 2001
SKB continued its creep testing of electron beam welds and friction stir welds during the period
/16-3/.
Programme
The programme for creep testing will continue during the coming three-year period. Modellings
of creep deformation of the copper canister under slow loading are being considered.
16.2.6 Thermal expansion
The difference in coefficient of thermal expansion between cast iron and copper can lead to
strains in the copper canister. However, these are negligible from the strength viewpoint.
Conclusions in RD&D 2001 and its review
Not dealt with in RD&D 2001.
Newfound knowledge since RD&D 2001
No new knowledge has been forthcoming.
Programme
The field is judged today not to require any further research, development or demonstration.
New developments are being monitored and will be acted on when appropriate.
16.2.7 Deformation from internal corrosion products
The build-up of corrosion products between the cast iron insert and the copper shell can lead to
an internal pressure on the copper shell.
Conclusions in RD&D 2001 and its review
SKI considers SKB’s continued programme of characterizing corrosion products to be reasonable,
but reiterates its recommendation to SKB to continue work on gathering a detailed body of
data as a basis for quantifying the corrosion of the cast iron if there is a hole in the copper shell.
This work should take into account the local environment in the narrow gap between the cast
iron insert and the copper shell with possible effects of, for example, carbonate and sulphide
on the composition of the corrosion products and the possibility of aerobic corrosion due to
radiolysis of water. Possible effects on the corrosion rate due to the metal coupling between
copper and cast iron (galvanic corrosion), as well as transport properties inside and around a
damaged canister, should also be included.
Newfound knowledge since RD&D 2001
The consequences of the build-up of corrosion products in the gap between the copper shell and
the cast iron insert has been investigated experimentally since SR 97 /16-4, 16-5/. None of the
experiments succeeded in showing any pressure build-up as a consequence of the build-up of
corrosion products. Attempts have also been made to get an idea of the long-term consequences
of the build-up of corrosion products by means of studies of archaeological analogues /16-6/.
Here as well, the conclusions were that no signs of heavy deformations could be found on
copper-based materials in close contact with anaerobically corroded iron.
RD&D-Programme 2004 187