Spent nuclear fuel. A material that can be misused, for example, to make a nuclear weapon. That’s why its transportation and storage are subject to strict security measures. Temelín’s spent fuel is stored in a pool next to the reactor for about ten years. The International Atomic Energy Agency’s camera is pointed at it for the whole time. Its images are transmitted directly to the Agency’s headquarters in Vienna. “The checks are in place to prevent nuclear material from being used for non-peaceful purposes. We have actually a number of tools. Some are for storage, other are for transportation. Their purpose is to keep constant track of spent fuel,” said Colin Fuller, a Scottish IAEA inspector during his inspection at Temelín.

Key checks are carried out when fuel is loaded into a special storage cask. This takes place in the pool next to the reactor. “Fuel loading is checked using special equipment that can measure the level of fuel utilization. This allows inspectors to easily recognize the declared fuel assemblies and distinguish them from, for example, dummy assemblies. Inspectors then use cameras to check the assemblies’ numbers,” notes Marek Sviták, a spokesman of the Temelín power plant owned by CEZ Group.

The whole reactor hall is surveilled by cameras, though. This allows inspectors to watch not only the path of a cask in the hall but also the installation of protective lids. Moreover, inspectors secure the lids with several seals. They attach the first seals right in the reactor hall before actual transportation. They put on additional seals when the cask is placed in storage. “We attach two seals apiece to two of the three lids. One is optical, the other is metal. We can check the optical seal right from the ground using a special reader. Checking the metal seal would require climbing onto the 5.5-meter cask. So they are mainly used as a backup in case the optical seal is damaged,” adds Milan Weis, a Euratom inspector.

This weekend was the last time spent fuel casks were handled in the Temelín storage area this year. There are currently 31 occupied storage positions out of a total of 152. Casks can stand there for up to 60 years. They will be under IAEA’s camera surveillance all the time. International inspectors will also come to check the seals once a year.

ČEZ put the spent fuel storage at the Temelín power plant’s site into operation in 2010. It is a reinforced-concrete structure consisting of a reception area and a storage area. Its covers an area roughly matching that of a soccer field and its capacity is sufficient for 30 years of the Temelín power plant’s operation. There are currently 31 casks out of possible 152 in storage. Spent fuel can be stored in casks for up to 60 years.