Abstract
Abstract. To meet safety requirements for underground storage of high-level nuclear waste, engineered barriers are an integral part of a modern defense-in-depth concept and therefore have to be considered in interaction with the host rock. This study presents preliminary results for the load behavior of a canister made of pressure-less sintered silicon carbide (SSiC), which forms the main retention barrier for the fission products in a new multi-layer waste package design denominated as TRIPLE C. This means a three-fold enclosure strategy, spreading the functionalities to three different ceramic barriers: first the porous potting compound surrounding each single fuel rod in the container, second the solid container wall of SSiC and third the over-pack of carbon concrete. Besides all the advantages a potential drawback of ceramics in general is their brittleness. Therefore, the behavior of SSiC structural components under static and dynamic loading has to be investigated. First results for a small model canister indicate that static loading will not create any relevant damage, even if stresses are extremely high and highly anisotropic on a canister all-around embedded. First dynamic simulations indicate that, under very unfavorable circumstances, the model canister can experience tensile stresses bigger than its tensile strength. Also, point loading may cause damage to the canister under certain conditions. Based on the performed calculations, the SSiC canister design will be optimized together with the carbon concrete over-pack, so that mechanical damage of main retention barrier can be excluded even under extreme static and dynamic conditions in a final repository.
Highlights
Sintered Silicon Carbide (SSiC) is a material characterized by high corrosion resistance, gas-tightness, extreme longterm stability (Peterson and Dunzik-Gougar, 2011; Mceachern et al, 2012) and high temperature resistance
Holmquist et al (1999) reported a static uniaxial compressive strength of around 3900 MPa of SiC-B at room temperature. Their test results indicate that the static uniaxial compressive strength will remain relatively stable from −200 to 570 ◦C
3.4 Embedded canister in highly anisotropic stress field. This model assumes that the SSiC canister is protected by a layer of compacted bentonite (8 cm thick), embedded in the rock mass which is characterized by a vertical stress component of 10 MPa and a horizontal principal stress of 30 MPa
Summary
Sintered Silicon Carbide (SSiC) is a material characterized by high corrosion resistance, gas-tightness, extreme longterm stability (Peterson and Dunzik-Gougar, 2011; Mceachern et al, 2012) and high temperature resistance.
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