This paper describes how a rather conventional rock cavern will be used for intermediate storage of spent nuclear fuel from the Swedish nuclear power stations. The plant and the spent fuel handling is generally described. The design requirements for the rock cavern postulate very high safety demands. An extensive reinforcement will therefore be carried out in order to guarantee the stability of the rock cavern. The cost of the rock cavern will be reasonably low, in spite of the extended costs of reinforcement, compared to the advantages which are obtained by this type of sub-surface storage.
In order to increase present spent fuel storage capacity available at the Swedish nuclear power stations, the Swedish Nuclear Fuel Supply Company (SKBF) is planning to erect an intermediate spent fuel storage facility (CLAB). Oskarshamnsverkets Kraftgrupp Aktiebolag is assisting SKBF in realising the CLAB project, and the Swedish State Power Board (SSPB) is designing the building constructions. The other main consultants engaged in the project is Asea-Atom (Sweden) and Societe Generale pour les Techniques Nouvelles (France).
CLAB will be located close to the Oskarshamn nuclear power station. All permits required to the facility were obtained in 1979. CLAB was then the first licensed spent fuel storage facility of its kind in the western world.
The fuel elements will be stored in a rock cavern, which provides very good protection against external impacts such as acts of war and sabotage. The bedrock will also protect the environment by isolating the fuel in the unlikely event of any internal impact taking place. The advantages of this sub-surface storage are obtained at a reasonably low cost compared to the cost of a storage building on the surface designed to resist the same impacts.
The rock cavern will be constructed using well-known techniques. This paper will describe how a rather conventional rock cavern can be used in combination with techniques for nuclear fuel handling. The description of the design and construction work is based on knowledge of the existing rock mass on the site.
The CLAB design is based on a storage capacity of 3000 metric tonnes of uranium, with provisions to permit an expansion of this capacity to 9000 tons. In terms of function, the CLAB facility can be divided into three main parts: fuel reception, storage and auxiliaries.
Spent fuel from Ringhals, Barseback and Forsmark nuclear power stations will arrive at the harbour of the Oskarshamn power station on a ship specially designed for this purpose. The fuel elements will be transported in containers called casks. These casks are designed to provide adequate protection against damage during transport. The casks will be transported on a special vehicle from the ship or from Oskarshamn power station to the CLAB facility. The vehicle will bring the cask to the fuel reception building at CLAB. In this building, the casks will be cooled down and then placed in an unloading pool. The fuel elements will be unloaded under water, which provides protection against radiation, and then placed in special canisters.