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The Onkalo final repository in Finland

by Nils-Axel Mörner

Onkalo is the name of the proposed final repository of high-level nuclear waste at Olkiluoto in Finland. The method applied is the Swedish KBS-3 method implying a deposition in the bedrock at a depth of about 500 m, with a backfilling of bentonite, a sealing of the access tunnels and shafts and a guarantee that this repository will stay intact for 1 million years (according to Posiva).

Instead of presenting an opus operandi of how this repository was going to be constructed and kept intact for the immense time period of 1 million years, the Finnish Government took “a decision in principle” (in years 2000 and 2001) that a final repository was allowed to be built at Olkiluoto (close to Rauma in SW Finland). During the construction, the Government assumed that problems were to be revealed and dealt with.

This is, of course, a terrible way of handling such a delicate safety issue as the protection with 100% safety of this high-toxic material for 1 million years into the future.

Everyone should understand that no one has the capacity to predict anything over such a time period as 1 million years. Just claiming that you can do so, should discriminate them as being not serious and unscientific, or, more directly spoken; to spread disinformation.

With that as a philosophical-ethical dismissing of Posiva’s claim and assurance, we must turn to the proposed safety of the individual barriers; one by one.

The old idea (from the 1950s) of a nearly total stability of the Fennoscandian bedrock has, in recent years and by very clear observational facts, become totally dismissed and substituted by an understanding that, even our bedrock, is highly unstable. This is especially the case when the land ice melts away after an Ice Age and the land rises at exceptionally high rates. The earthquakes are high in magnitude and numerous in frequency (recently well documented in the Rauma area). In such an environment, no repository hidden in the bedrock would remain safe. And in the future, we will surely pass through new glaciation and deglaciation periods. A totally new finding is the occurrence of explosive methane venting when methane ice accumulated in bedrock voids suddenly transforms into methane gas (at a volume rate of 1:168). This is especially dangerous for Olkiluoto where the bedrock is unusually rich in methane. Another factor is the proposed “safe distance” for a repository to regional faults. Posiva claims that this distance is in the order of 100 m – observational facts would suggest a distance of 5 to 10 km. This is vital for the Olkiluoto repository as the area is traversed by numerous faults and fracture zones.

The duration of the canister has been questioned. The behaviour of the bentonite filling seems far from clear. In saline water the swelling minerals behave far from assumed.

In conclusion, many shortcomings seem to be connected with a KBS-3 repository, and the long-term safety can certainly not be guaranteed.

We can see why the Finnish Government took the strange decision that a KBS-3 repository would, “in principle”, satisfy the goals set. This was to open for and allow for the building of new nuclear power plants (Olkiluoto 3). Unfortunately, it also opened, at least in principle, for uranium mining in Finland.