As a geophysical consultant for Svensk Kärnbränslehantering AB (SKB), Ramboll has carried out geophysical borehole logging as part of the site investigations for a deep storage facility for radioactive waste.
Disposal of nuclear waste
Svensk Kärnbränslehantering AB (SKB) manages and disposes radioactive waste from Swedish nuclear power plants. Currently they are working on finding a site for disposal of the spent nuclear fuel – a final repository. As a geophysical consultant for SKB, Ramboll has carried out geophysical borehole logging as part of the site investigations for a deep storage facility.
The site investigations are carried out to ensure a high level of safety and are carried out openly in collaboration with affected stakeholders such as private individuals, municipalities, political bodies and regulatory authorities.
The spent nuclear fuel will be encapsulated in copper. The copper canisters will then be deposited in the bedrock, embedded in clay, at a depth of 500 metres. Geophysical borehole logging has been used as an important tool for assessing the physical properties of the bedrock 500-1000 metres below the surface.
Ramboll’s role in the project
Ramboll’s consultancy has included geophysical borehole logging of density, self potential, normal resistivity, guard resistivity, magnetic susceptibility, 3D calliper, acoustic televiewer, sonic and fluid conductivity and temperature. The measurements have been conducted in 134 deviated boreholes of up to 1000 m. The total length of the reported borehole logs has been 450 km. The logging operation has been carried out at the two proposed sites for the final repository in Oskarshamn and Forsmark, eastern Sweden.
The processing of data has included detection and mapping of borehole breakouts and other borehole deformations by means of processing of data from an acoustical televiewer probe. Breakouts, keyseats and washouts with a certain magnitude (more than 0.1 mm), is mapped and classified by special processing routines. Also micro fallouts (fallouts smaller than 0.1 mm) are registered, but the mapping of these is more uncertain, as it is not possible to make specific criteria for this phenomenon. The special processing routines where developed by Ramboll and applied to acoustic televiewer data from 15 boreholes of 500-800 m.