Swiss regulator looks at aging of waste containers

The Swiss Federal Nuclear Safety Inspectorate has called for the systematic management of the aging of containers in the country's interim radioactive waste storage facilities. The requirement follows the completion of a study into container aging and fuel handling in such facilities.

The Swiss Federal Nuclear Safety Inspectorate (ENSI) has called for the systematic management of the aging of containers in the country's interim radioactive waste storage facilities. The requirement follows the completion of a study into container aging and fuel handling in such facilities.

Waste containers in the central Zwilag interim waste management facility at Würenlingen (Image: ENSI)

Radioactive waste in Switzerland is held at interim storage sites before it can be disposed of in deep geological repositories. The interim storage containers were originally designed to be used for a period of 40 years, but such repositories are now not expected to be operational until 2050-2060. Some of the waste, therefore, will be stored in the interim containers for more than 40 years.

ENSI announced today the completion of a study, launched in 2015, aimed at ensuring the long-term safety of interim storage containers.

The study in particular aimed to assess whether aging has any safety-related effect on the functionality of the container components. It also investigated whether, even after extended interim storage, the transport of the containers to the surface installation of the repository would create problems.

ENSI said its research showed comprehensive and systematic aging management of interim storage is necessary. Within this framework, it has issued a list of actions to be taken to ensure the long-term safety of storage containers. These include compiling information on fuel behaviour under mechanical load; influence of temperature on fuel cladding properties; container components; and, storage capacity.

ENSI plans to introduce a requirement for owners of transport and storage containers for used nuclear fuel and high-level waste to implement an aging management program and submit it to ENSI. This must be done for each type of container placed in interim storage. The program will be reviewed and updated every 10 years.

The regulator considers further development of the rules will be necessary. It will initially draw up a recommendation guideline that will help facilitate the structured provision of container aging data while allowing short-term revisions. This, it said, should simplify the introduction of a system for the management of storage and transport containers.

After an initial phase, ENS will provide more detailed requirements for aging containers in its guidelines.

Six sites were proposed in November 2011, during the first stage of the selection process for the siting of two repositories: one for low- and intermediate-level waste and the other for high-level waste. Three regions - Zürich Nordost, Jura Ost and Nördlich Lägern - are under consideration for further investigations.

Researched and written
by World Nuclear News