Expansion of interim storage for spent fuel completed in Olkiluoto
28.1.2015
The expansion project of the interim storage for spent nuclear fuel, which was started in Olkiluoto in the summer of 2010, has now been completed down to the last installations.
"After the commissioning inspection carried out by the Finnish Radiation and Nuclear Safety Authority before Christmas, the expansion project of the interim storage can now be considered completed", says Mr. Tommi Virtanen, who works as a project engineer in TVO's building technology division.
The structures and equipment of the interim storage for spent nuclear fuel have been designed to ensure that the radioactive substances contained in the spent fuel will not cause any danger to the environment.
"The fuel assemblies placed in the pools are now protected against falling structures by steel covers manufactured by Satateräs in Siikainen. Together with the external embankment, the covers are part of the protection of the interim storage against airplane crashes. The fuel racks were delivered by the Spanish company ENSA based in the town of Santander. They manufactured the racks, but their installation was carried out by TVO itself."
Fuel assemblies that have been unloaded from the reactor and stored in the reactor pool, are transferred to the interim storage for spent nuclear fuel, where they are cooled in water pools until their final disposal in the final disposal facility to be constructed in Olkiluoto. The final disposal is scheduled to start in early 2020's.
"One reason for the expansion of the interim storage was the increase in the amount of spent fuel from the existing plant units and later from OL3. At present, we have some seven thousand fuel assemblies in the storage", Mr. Virtanen explains.
Modern technology
After the expansion, the volume of the interim storage is ca. ninety thousand cubic metres. The safety features of the storage were also upgraded in the expansion project with new systems and firefighting equipment introduced for the supply of cooling water to the fuel assemblies. I&C systems were also enhanced; for example, more accurate pool temperature and level measurement systems are now in place.
External protection properties were improved by building high earth embankments around the storage and installing steel covers on top of the pools.
According to Mr. Virtanen, the purpose of commissioning inspections was to verify that the equipment and components function as planned.
"All the documents and functions were inspected with the Finnish Radiation and Nuclear Safety Authority and we now have permission to start the transfer of fuel assemblies from the operating plant units."
Local competence
About 80 Subcontractors were involved in the expansion project.
"Finnish workers accounted for well over 90 percent. The Finnish west coast, in particular, can boast a high degree of competence in demanding nuclear construction technology", acknowledges Mr. Virtanen.
Actions complying with good safety culture were a key requirement for a successful end result.
"The project was designed to ensure the safe use of the building for at least the next hundred years. Our work is always planned for long-term results."
Text: Pasi Tuohimaa and Tiina Kuusimäki
Photo: Hannu Huovila
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