Natural uranium deposits serve as a model for final disposal

In the crust of the earth there are several deposits where the content of uranium is very high, in some places up to 60%. This is over 100 000 times more than in the Finnish bedrock on average. The most relevant natural analogue is the 1 300-million-years-old Cigar Lake uranium deposit in Canada. It involves the same multiple barriers as the planned Finnish disposal system for spent nuclear fuel: solid UO2, clay buffer around the uranium, quartzrich cap and half a kilometer of rock above the uranium. The most important difference is that in nature there is no long-lasting metallic canister around the uranium. Nature has even tested an underground natural fission reactor, 1 800 million years ago in Oklo, Africa. The careful investigations carried out at these natural analogue sites have indicated that uranium and other elements have been preserved in the deposits for millions or even billions of years. During the isolation from the biosphere, the radiation of the hazardous radionuclides has been reduced to harmless levels as a result of the natural decay. Thesedisposal experiments done by the nature serve as a valuable confirmation of the experts' view that the disposal plans presented will meet the most strict requirements for safety and environmental protection