Spent fuel storage
Spent Fuel Interim Storage Facility
Three different approaches are adopted for the safe management of the spent nuclear fuel. The first one is the open fuel cycle, including the direct disposal of spent nuclear fuel, without reprocessing, into a deep geological repository. The second approach is the partly closed or closed fuel cycle, with reprocessing the spent fuel and recycling the recovered plutonium and uranium. The third possibility is to place the spent nuclear fuel in an interim storage facility until the decision is made on its reprocessing or direct disposal.
The interim storage of the spent fuel is an inevitable step irrespective of the applied spent fuel management strategy. Due to technical reasons, interim storage is always required in the initial phase of spent fuel disposal. The activity and the heat generation of the spent fuel significantly decrease during this period, which facilitates the subsequent handling operations.
Description of the SFISF
The SFISF is a modular vault type facility designed for the storage of spent nuclear fuel. It is a surface facility, in which the fuel assemblies are stored separately in vertical position, installed in airtight sealed storage tubes, filled with inert gas (nitrogen). The tubes are inserted into vaults enclosed with concrete walls. Adequate shielding is provided by the concrete structure of the vaults around the storage tubes.
The storage takes place in dry conditions and the generated remnant heat is removed by a cooling system based on natural air draught. This ensures that no electrical fault or technical problem could result in loss of cooling. The filtered cooling air flows through the interspace among the storage tubes. The air cannot get in contact with the fuel assemblies.
In addition to the radiological and cooling considerations, the effects of seismic events and the protection against high ground water level were also considered in the design of the facility. The design foundation-level of the SFISF was set at an elevation so that the facility would not be flooded even in the case if the maximum design flood level occurs.
The seismic design of the SFISF took place by taking into account 0.35 g peak ground acceleration determined for the maximum design earthquake. Re-evaluation of the seismic hazard of the site defined later a horizontal peak ground acceleration value of 0.25 g at an earthquake frequency of one in 10,000 years.
The alarm systems of the SFISF are aligned to the similar systems of Paks Nuclear Power Plant.
The SFISF site is within the Paks Nuclear Power Plant’s airspace prohibited for flight, in a circle of 3 km radius and an altitude of 5950 m.