Onkalo

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  • owned by Posiva
  • supposed final repository for HAW
  • Olkiluoto was selected as the site for final disposal of spent nuclear fuel in 2000[1]
  • in 2000 the municipality of Eurajoki issued a building permit for the underground characterisation facility Onkalo[1]
  • 2004-2009: ground-level service and monitoring buildings for Onkalo under construction; excavation of the access tunnel to reach a depth of 420 meters[1]
  • 2009-2011: excavation of Onkalo to continue down to 520 meters; research on mechanical characteristics of the bedrock, and layout adaption of the repository to continue[1]
  • 2012: Posiva to submit an application for a construction license for the final disposal facility[1]
  • 2015: construction of the final disposal facility to start[1]

Some historic key points:[2]

  • 30.12.1992: Olkiluoto, Konginkangas and Kuhmo were chosen for more detailed site investigations for final disposal site for spent nuclear fuel.
  • 1.1.1996: Posiva Oy began its activities.
  • 21.12.2000: The Council of State gave a positive Decision in principle for Posiva Oy's application for the construction of a final repository of spent nuclear fuel at Olkiluoto, Eurajoki.
  • 18.5.2001: The Finnish Parliament ratified the Decision in principle made by the Council of State supporting Posiva Oy to construct a final repository for spent nuclear fuel at Olkiluoto in Eurajoki.
  • 25.4.2008: Posiva Oy filed to the Government an application-in-principle to expand its for spent fuel for OL4.


Contents

Encapsulation starts the final disposal process

provided by an exhibition presented at the international anti-nuclear conference in Vienna on May 31, 2013

After the spent fuel assemblies have been removed from the reactor, they are allowed to cool down for at least 20 years before the final disposal process can proceed. After a few decades the radioactivity level and heat generation in the fuel are reduced to less than thousandth part of the original level. When the fuel assemblies have cooled down enough, they are transported to an encapsulation plant. The plant is located at ground level above the actual repository. The encapsulation plant is equipped with a system that protects the outside world from radiological consequences should anything extraordinary take place during the encapsulation process.

During encapsulation the spent fuel assemblies are sealed into canisters. Those consist of copper and cast iron insert. The canisters are closed by welding and transported to the final disposal tunnel which is located at a depth of ca. 400 meters.


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.


An ambiguous reputation as a pioneer of nuclear waste management

Source: lecture of Tapio Litmanen, University of Jyväskylä [3]

  • Posiva, nuclear waste company, suggested Olkiluoto to be a final disposal site in May 1999
  • The municipal council of Eurajoki made a positive statement on the decision in principle in January 2000
  • The Government made the decision in principle on the 21st of December 2000
  • The Parliament ratified the decision on the 18th of May 2001

The nuclear waste management system

  • Spent nuclear fuel is managed by Posiva Oy
    • set up in 1995 as a joint venture company - 60% TVO and 40% Fortum
  • Deep geological repository for encapsulated used fuel at the Olkiluoto island in Eurajoki
    • some 400 metres down in 2 billion-year-old igneous rock
  • Plans do not include accommodation for used fuel from Fennovoima's new plant
    • But the government can use its legal authority to ensure that Fennovoima fuel would be included


  1. 1.0 1.1 1.2 1.3 1.4 1.5 provided by an exhibition presented at the international anti-nuclear conference in Vienna on May 31, 2013
  2. TVO: Pocket Guide 2010; Eura Print Oy, 2010
  3. http://www.nuclear-heritage.net/images/7/70/Case_Pyhajoki_presentation_Finnish_Exceptionalism.pdf as at August 8, 2013

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