Spent fuel from the Finnish Triga research reactor in the surroundings of BWR spent fuel final disposal repository. Safety assessment and comparison to the risks of the BWR fuel

The Finnish Triga reactor, a 250 kW research reactor, has been in operation since 1962. According to the current operating license of our reactor we have to achieve a binding agreement between our Research Centre and the domestic Nuclear Power Companies about the possibility to use the Olkiluoto final disposal facility for our spent fuel. Naturally there is also the possibility to make an agreement with USDOE about the return of our spent fuel back to USA. In case of the domestic final disposal solution the main safety aspects, which have to be analyzed and compared to the spent fuel coming from the nuclear power plants, are the criticality safety, the solubility of the fuel (UZrHx) to water and the existence of some moving and long-lived radioactive isotopes. The criticality safety calculations show that it is possible to load safely all the TRIGA fuel elements in one heavy final disposal canister. A simple safety analysis for the Triga fuel has been carried out in order to evaluate the long term risks of the final disposal. For the analysis a few scenarios from the TILA-99 safety assessment have been chosen. These scenarios will give a good picture of the potential risk of disposed Triga fuel compared to BWR fuel. TILA-99 safety assessment includes about 100 calculated different scenarios for the spent fuel so it’s not reasonable to calculate them all for the Triga fuel. The main result is that the risks from the final disposal of Triga fuel are minor compared to BWR mainly due to smaller activity inventories.