RD&D-Programme 2004 - SKB

8 Canister – encapsulation
The design of the encapsulation plant depends on where it is sited. SKB’s main alternative is
to build the encapsulation plant connected to Clab. The work of designing such a facility was
begun in 1993. Since then the facility has been further developed and modified. SKB has also
studied the possibility of building an encapsulation plant adjacent to the deep repository in
Forsmark.
In this chapter, an encapsulation plant connected to Clab is dealt with in section 8.1 and an
encapsulation plant in Forsmark in section 8.2. Sections 8.3 and 8.4 describe the measures
that will be required with regard to physical protection and safeguards.
8.1 Encapsulation plant at Clab
The general production requirements on the encapsulation plant are that it must have a capacity
of one canister per day and a lifetime of at least 60 years, and that all types of spent fuel that
are stored in Clab must be able to be handled and encapsulated. To protect personnel and
nearby residents, high standards of safety must be met in the operation of the plant. The safety
standards cover radiation protection and fire protection, among other things. The spent fuel must
always be able to be handled without risk of criticality.
For the licensing work the plant is dealt with separately from Clab with its own preliminary
safety report. When the plant is ready to take into operation, the safety analysis report will be
integrated with the one for Clab.
Different siting alternatives have previously been compared and presented /8-1/. There are
several advantages to a siting adjacent to Clab. For one thing, the experience of fuel handling
that exists at Clab can be taken advantage of. Several of the existing systems and facility
sections in Clab can also be utilized for both facilities.
8.1.1 The plant
Besides fuel from today’s energy-generating nuclear power plants, certain other fuel types are
also stored in Clab’s storage pools. The intention is that this fuel can also be encapsulated in the
copper canisters without the canister design having to be modified. In the same way as spacers
are used in the transport casks for fuel shipments to Clab, the space in the channels in the inserts
can be modified to suit all fuel types by means of spacers in the canisters.
Damaged fuel is transported to Clab in special cans for leaking fuel. After arrival at Clab, the
damaged fuel has previously been lifted out of the cans and stored in the same way as other fuel,
i.e. in storage canisters in the storage pools. In the future, damaged fuel may be stored in Clab in
cans for leaking fuel. Prior to encapsulation of the damaged fuel, however, this fuel must also be
lifted out of the cans to be placed in the copper canisters. The experience that exists of transporting
damaged fuel and handling and storing it in Clab suggests that no further degeneration of the
fuel take places during storage.
A limiting factor for the fuel content in a copper canister is the canister shell’s outer temperature
in the deep repository. In designing the encapsulation plant the maximum permissible heat
output of each canister is assumed to be about 1.7 kW. Since burnup and cooling times vary for
the spent fuel, this means that the contents of each individual copper canister must be planned
carefully to permit maximum utilization of the canisters. Towards the end of the encapsulation
period, it may nevertheless be decided not to fill the canisters completely rather than to wait for
them to cool sufficiently.
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