TECHNICAL | SHAFTS & CAVERNS
The Swedish Nuclear Fuel and Waste Management
Co (SKB) is now extending this waste vault to triple its capacity. Rock blasting for the extensive excavations began in late 2024. The full construction project is expected to take about six years to complete. Its excavations will be underway as those for the neighbouring deeper vault, for spent fuel, get underway in earnest. A third storage system class is needed by SKB, for
long-lived radioactive waste. It is still in planning and the site is yet to be selected. It would store metallic materials, such as reactor core components, control rods from water reactors, and reactor pressure vessels, as well as long-lived waste from medicine, research and industry. It would be the last and smallest of the three vaults, says SKB. The expanding short-lived waste vault and coming
deep vault for spent fuel are what SKB calls its final repository system at Forsmark. Whether the vault needed for long-lived waste is also located at Forsmark has yet to be determined, for there is another possible location - one that has competed to be a host site before.
DEEP GEOLOGICAL REPOSITORY - THE JOURNEY BEGINS Forsmark was not, from the outset, the predetermined site to provide deep burial of high-level waste. There was a key competitior and it looked to be winning, even though Forsmark already a power plant and an underground storage vault for short-lived radioactive
waste. Forsmark was competing against the bedrock characteristics of another keen candidate, the Laxemar site, in Oskarshamn municipality, in the south of Sweden. Oskarshamn already hosts an interim storage facility
for spent fuel (Clab). The storage is provided by water- filled concrete basins with steel lining, in vaults 30m down in the bedrock. It has been operational since the mid-1980s. SKB is seeking its expansion as existing capacity would be reached before the Forsmark deep repository is operational, tunnellers were told by SKB at the most recent World Tunnel Congress (WTC 2025), held in Stockholm, in mid-2025. Excellent bedrock is the key to securely and safely
storing nuclear spent fuel at the deepest levels possible underground. Strong and highly competent rock mass is needed, along with favourable groundwater characteristics. Together, the rock mass and extremely limited groundwater movements will act as an effective barrier, shielding the ground surface environment from the stored high-level waste. Effective distance is the key.
Unfortunately for Forsmark, its competitor looked able
to hold the required high-level waste storage vault at slightly deeper depths. That is, until the possibilities for Forsmark received a boost from researchers finding that new measurements and analysis rock stresses showed that “these stresses have less impact on the repository depth” than had been assumed, according to SKB’s report ‘Site Investigation: Forsmark (2002-2007)’. The data came from almost six years of site investigations, including with trial drillings. Therefore, for a given stress
Above: SKB’s concept layout for the Forsmark deep geological repository for spent nuclear fuel, soon to start main excavation 14 | October 2025
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