SKB/TVO ice age scenario

Ice ages have repeatedly occurred throughout geological history, and it is likely that they will also occur in the time-span considered for the disposal of nuclear fuel. Based on the present status of knowledge, this report discusses when future ice ages will occur and the possible changes in the geosphere that might be of importance for repository performance. The report is intended to be used as a basis when developing scenarios for safety analysis of final repository for spent nuclear fuel. Both the ACLIN and Imbrie and Imbrie models suggest stadials (glaciations) at c. 20000, 60000 and 100000 years from now. The ACLIN model also suggests a glaciation period around 5000 years ahead. The next interglacial period will occur at c. 75000 years, according to the Imbrie and Imbrie model, while the ACLIN model suggests that interglacial conditions will not appear until 125000 years form now. Other models strongly support the 60000 year glaciation event. To some extent there is also support for the 20000 and 5000 year events. For the purpose of the SKB/TVO scenario it is suggested that smaller or large glaciations will occur at 5000, 20000 and 60000 years form now. Following the last glaciation, interglacial conditions will prevail at 75000 years. Thus after the first glaciation (5000 years) this is the earliest time when most part of Sweden and Finland will once again be resettled by man. (25 refs.)