RD&D-Programme 2004 - SKB

Transport casks for spent nuclear fuel (Type B packages)
SKB owns ten transport casks for spent fuel assemblies of model TN17-2 and two casks for core
components of model TN17-CC. The casks were made in 1982–84.
Up to and including 2003, the fuel transport casks had been used 130 to 150 times and the casks
for core components some 60 or so times each. The casks have served their purpose well. Other
equipment in the transport chain has also proved to be reliable. Consumption of spare parts has
not exhibited an appreciable increase over time.
Terminal vehicles
SKB owns five terminal vehicles. One is at SFR in Forsmark and the others stationed at Clab.
The terminals vehicles are usually carried by m/s Sigyn to the nuclear power plants to be used
for local overland transport of fuel and waste transport casks and containers.
The terminal vehicles at Clab underwent a total renovation in 1997–2001, when diesel engines
and cabs were replaced, among other things. The fifth vehicle is being renovated to the same
standard as the others during 2004. The vehicles work well and are expected to be able to be
used for another ten years or so without the need for any major modifications.
9.3.3 Transport of encapsulated fuel
Canister transport casks
A feasibility study was carried out in the mid-1990s regarding a transport cask for canisters.
A more detailed design of a canister transport cask is being carried out during 2004. The basic
features are not expected to deviate from those proposed previously, which are described in brief
below.
The main function of the cask is to comprise a radiation shield for the enclosed canister so that
it can be handled during transport without any additional radiation shielding. It must also satisfy
the other requirements for Type B packages in accordance with the IAEA’s transport recommendations,
see section 9.4, regarding for example strength and heat resistance, and must be able to
dissipate the emitted decay heat so that neither the canister nor the surface of the cask get too
hot. A transport cask with canister is shown in cross-section in Figure 9-2.
The planned cask, which will have a diameter of about 1.6 metres, is made of cast iron with a
thickness of between 250 and 300 millimetres. The wall thickness is determined by the required
radiation shielding. Iron does not attenuate neutron radiation as well as gamma radiation, so
the cask shell is provided with a number of channels that are filled with a plastic material that
Shock absorber
Transport cask
Canister with spent nuclear fuel
Figure 9-2. Canister transport cask in cross-section.
106 RD&D-Programme 2004