Geomechanical aspects of Sintered Silicon Carbide (SSiC) waste canisters for disposal of high level radioactive waste

High-level radioactive waste (HLW) poses threat to the biosphere. Geological disposal is accepted as a safe way for HLW disposal. Waste canisters made of Sintered Silicon Carbide (SSiC) are proposed and geomechanical safety aspects relating to such SSiC canisters are investigated. First part of the thesis reviews the state-of-the-art and demands for HLW disposal. The reason for considering Silicon Carbide (SiC) as canister material is explained. Especially in terms of corrosion and lifetime, ceramics and especially SiC is superior to metals or concrete. The only concern is its brittle behavior. The second part of the thesis presents results on static and dynamic mechanical properties of SiC in general and in particular for SSiC based on literature review and own lab tests. Although strength values for SiC and especially SSiC are very high, the extreme brittle behavior has to be considered in case of impact or point-like loading. The third and most extensive part of the thesis part contains numerical simulations, which consider most critical potential loading situations during transport and installation of the canisters underground. Both, pure elastic continuum and DEM based models are used considering the following loading situations (critical scenarios): Freefall of canister during transport or installation (FF), Impact by falling rock block at disposal site (RF), Point loading due to accidental insertion of small stone below the canister (PL), Anisotropic earth pressure loading after disposal (EP). Coating to protect the canisters against damage is investigated and preliminary parameters in terms of stiffness and thickness are recommended.

Level thesis:degree_level

thesis.doctoral

Grantor dc:publisher

Technische Universität Bergakademie Freiberg

Year

2021

Author dc:creator

• Zhao, Yanan

Contributors dc:contributor

• Konietzky, Heinz
• Knorr, Jürgen
• He, Guicheng

• high level radioactive waste disposal
• geological disposal
• silicon carbide
• DEM
• Hochradioaktiver Abfall
• Endlagerung
• Behälter
• Siliciumcarbid