SR-97: Canister performance under normal disposal conditions.

The SR-97 disposal canister consists of an inner load bearing cast iron component and an outer corrosion barrier of copper. The mechanical strength of the insert must be such that it withstands, with sufficient safety margins, the combined forces of hydrostatic pressure at the disposal depth (7 MPa) and the bentonite swelling pressure (7 MPa). It must also withstand an increased hydrostatic pressure during a future glaciation. This pressure increase may be as high as 30 MPa. For this load situation, no extra safety margins will be required. Uneven pressure may occur during the water saturation of the buffer and to some extent some uneven pressure may also persist after water saturation. Calculations have been performed for such design basis uneven loads and the present canister design has been shown to withstand them. Under the oxygen-free conditions at the disposal depth, copper will be thermodynamically stable. Only dissolved sulfide will be able to corrode the copper. The supply of sulfide is expected to be low and, consequently, the service life of the canister will be very long. Calculations indicate that no known corrosion processes will lead to canister failure during a shorter time than at least 1 million years.