Available on-demand - *F.EN08.05.01
Overview of the SKB Spent Fuel Research Program over the Years—Knowledge Gained and Remaining Open Questions
Swedish Nuclear Fuel and Waste Management Co1
The Swedish strategy for spent nuclear fuel has, since around 1980, been direct geological disposal. Research about the properties and dissolution of spent fuel has been going on since then. An overview of this research program is given here with a focus on questions posed and answered along the way, ending with remaining open questions. At the beginning, some basic studies were performed to gain information about spent fuel as wasteform. Dissolution studies were at first mainly performed in contact with air, and often with aqueous solutions that mimicked the expected groundwater chemistry. However, complexities relating to precipitation of secondary phases indicated that simplified water compositions were preferred. Knowing that the radioactivity of the fuel caused radiolytic oxidation of uranium and thus controlled the dissolution rate, there were also attempts to achieve reducing conditions via bubbling a hydrogen/argon mixture in presence of a palladium-catalyst. The first attempts resulted in variable results, but notably, a reduction in apparent leach rate was observed for some experiments . Later, possibilities to perform the leaching experiments in autoclaves, with controlled hydrogen atmosphere, allowed experimental conditions closer to the expected repository conditions. These experiments showed that hydrogen, during this type of experimental set-up, could suppress oxidative dissolution caused by radiolysis [2,3]. A new phase of research was thus started where the mechanistic explanation for the observed behaviour was sought. Experimental work, both with spent nuclear fuel and with analogue materials, was coupled with modelling efforts. At the time of the SR-Site safety assessment , which was a part of the license application submitted in 2011, a certain understanding had been reached, based on the effect of metallic particles in fuel. Still, questions remained and studies performed during the last decade (see for example ) can now be summarised to illustrate the knowledge gained, and remaining open questions. This summary is utilized in the next step in the licensing process: the application to start building the spent fuel repository, which is expected to be submitted within the next couple of years. In the coming decade the SKB research program will continue, with the goal to support the development of the safety assessment report, SAR, which will be submitted to the authorities as a part of the license application connected to start of trial operations.
During all these years, international collaboration has been a cornerstone of the SKB research program. This international collaboration has been carried out via European projects or bilateral agreements, and triggered the start-up of the Spent Fuel Workshops . The research program has also been presented at this MRS symposium since the early 1980’s.
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 Spahiu, K., Werme, L. and Eklund, U.B., 2000. The influence of near field hydrogen on actinide solubilities and spent fuel leaching. Radiochimica Acta, 88(9-11), pp.507-512.
 Werme, L.O., Spahiu, K., Johnson, L.H., Oversby, V.M., King, F., Grambow, B. and Shoesmith, D.W., 2004. Spent fuel performance under repository conditions: A model for use in SR-Can. SKB-TR-04-19. Swedish Nuclear Fuel and Waste Management Co.
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