RD&D-Programme 2004 - SKB

16.2.3 Heat transport
No new knowledge has been forthcoming. The process is dealt with as in RD&D 2001, i.e.
integrated with the temperature evolution of the fuel, see section 15.1.4.
16.2.4 Deformation of cast iron insert
Deformation of the cast iron insert could theoretically occur in conjunction with large tectonic
movements.
Conclusions in RD&D 2001 and its review
SKI says it is urgent that SKB carry out new calculations of the mechanical strength of the
canister, where all components are reconsidered, such as:
• Actually obtained material data from fabricated inserts.
• Updated material data for bentonite.
• Loads during glaciation (consistent with scenario selection).
• Defined permissible defects (from the consequence analysis).
• Failure criteria in connection with shear movements.
Newfound knowledge since RD&D 2001
With updated material data for bentonite, earthquake-induced rock shear calculations have been
carried out for the canister with insert /16-2/. The rock shear has been modelled and calculated
with the finite element code Abaqus. A three-dimensional finite element mesh that models the
buffer and the canister has been created and a number of calculations that simulate different
rock shears have been performed.
The rock shear is assumed to take place perpendicular to the canister axis either in the centre
of the deposition hole or at the quarter point. The shear calculations have been driven to a total
shear of 20 centimetres. The buffer has been modelled at four densities between 1,950 and
2,100 kg/m 3 at water saturation and at shear rates between 0.0001 and 1,000 mm/s.
The results show that the influence of especially the density of the buffer and the location
of the shear plane are very strong, but also that the shear rate and the magnitude of the shear
displacement have a significant influence. At the two lower densities an eccentric shear
plane is more dangerous, but at the two higher densities a centric shear is worst. At the
conservative combination of a shear rate of 1 m/s, a shear displacement of 20 centimetres
and a density of 2,100 kg/m 3 , the cast iron insert is strongly affected with a maximum plastic
strain of 19 percent, but in the reference case with a buffer density of 2,000 kg/m 3 and a shear
displacement of 10 centimetres, the plastic strain is reduced to 1.6 percent.
Programme
A large programme for probabilistic analysis of canister strength was started during 2003. In
this programme we are obtaining material data from fabricated canisters. Pressure testing of
canister sections is also included in the programme. According to the plans, this programme will
be concluded during 2004.
16.2.5 Deformation of copper canister under external pressure
Conclusions in RD&D 2001 and its review
SKI recommends that SKB show how a simplification of the model for deformation of the
copper canister affects the results. The simplification entails assuming plastic collapse instead
of creep.
186 RD&D-Programme 2004