Excavation of the Prototype KBS-3 Repository to Begin in 2023

The Prototype Repository is a full-scale experiment in 450 meter-deep crystalline rock at Äspö Hard Rock Laboratory (Äspö HRL). The experiment was initiated in 2001 to simulate the KBS-3 concept developed in Sweden for the disposal of spent nuclear fuel. The experiment consists of four deposition holes, each containing a five meter-tall copper canister surrounded by an eight-tonne bentonite buffer. The canisters are equipped with heaters to simulate heat from the decay of spent nuclear fuel. The deposition holes are located within a 64 meter-long backfilled deposition tunnel.<br/>In the experiment, more than 300 sensors have been installed so that i.e. temperature, pressure, humidity can be measured so that re-saturation and related processes like buffer swelling and homogenisation can be analysed under realistic conditions, including the prevalence of coupled processes and boundary effects, at a scale relevant for analysis of post-closure safety of a repository for spent nuclear fuel.<br/>The experiment also demonstrates the installation and handling of equipment at an industrial scale. Experiences from installing this experiment enabled SKB to argue for the feasibility of constructing and operating a KBS-type repository in their license applications.<br/>The Prototype Repository was planned to run for approximately 20 years, long enough for the buffer to resaturate, given the hydrologic conditions at Äspö HRL. The 20-year experiment timeframe also allows for results from the experiment to be considered in the future, operational license application for the KBS-3 repository.<br/>Excavation of the Prototype Repository will start early 2023 and will continue for two years. During this time a large number samples will be taken to study i.e saturation, homogenisation, swelling and mineral transformation of the clay material, status of the canister, incidence of heat-induced spalling in the deposition hole, and other factors of relevance to post-closure safety.