RD&D-Programme 2004 - SKB

The filled canister transport casks are transported to and received at the deep repository. There
the canisters are unloaded, after which the empty casks are transported back to the encapsulation
plant.
Conclusions in RD&D 2001 and its review
In its review comments on RD&D 2001, SKI pointed out the importance of flexibility in the
encapsulation plant, since many steps in the process have not been finalized. Furthermore,
SKI pointed out that it is important to incorporate experience from the Canister Laboratory
in designing the encapsulation plant, and that a more detailed description is needed of how
damaged fuel, fuel debrish, MOX fuel etc affect handling in the plant and plant design. The
impact on the encapsulation plant of a possible switch to horizontal deposition should also be
examined.
Newfound knowledge since RD&D 2001
Experience feedback from the Canister Laboratory to the design of the encapsulation plant takes
place continuously, for example due to the fact that personnel from the Canister Laboratory also
work with the encapsulation plant project.
The new welding machine for friction stir welding was installed and commissioned in the
Canister Laboratory during 2003. The FSW equipment offers an alternative to electron beam
welding. Experience from the development of the welding methods provides important information
for the design of the encapsulation plant. This also applies to the development of the
methods for nondestructive testing and other activities at the Canister Laboratory.
The change of atmosphere in the canister’s cast insert is not necessary, providing a certain
quantity of water can be accepted in the canister. Even after the fuel has undergone the drying
process, there might theoretically be water left in a damaged fuel rod. At present it is not
possible to determine how many damaged fuel rods might end up in the same canister. It is
therefore not possible to determine the exact amount of water there might be in the canister. As
a result, the plant is currently designed for a change of atmosphere in the canister insert. The
atmosphere change results in acceptable chemical conditions inside the canister, but entails an
extra step in the encapsulation process.
The encapsulation plant is being designed solely for the encapsulation of spent fuel. It will not
be possible at a later point in time to add equipment for handling of low- and intermediate-level
waste without re-designing the whole plant.
A possible switch to horizontal deposition will not, according to current plans, affect the design
of the encapsulation plant, since the preparation of the canister prior to deposition is planned to
take place in the deep repository.
The new decay heat measurement equipment was installed at Clab in 2003. It is designed for
accurate determination of the fuel’s decay heat. The equipment consists of a calorimeter, along
with gamma probes to measure the heat losses in the calorimeter caused by gamma radiation
that has not been absorbed. The more accurate the determination of the decay heat is, the better
the deep repository’s layout can be designed, since the surface temperature of the canisters
determines how closely they can be spaced. High decay heat, or high uncertainty regarding the
amount of decay heat, means that the canisters must be spaced at greater distances. This in turn
means that the deep repository’s underground part will be bigger.
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