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Long term behavior of claystone and its interaction with steel casing
Study of potential damage in the claystone surrounding a HLW disposal cell for storage of high-level radioactive waste (HLW waste).
Assessment of the short and long term behavior of the claystone and steel casing using both continuum (FLAC3D) and discontinuum (3DEC) numerical models, and accounting for:
- initial fracture induced by the tunnel excavation (Figure 1),
- influence of the heat generated by waste package on claystone creep,
- effects of steel corrosion on casing strength over the time.
- Continuum vs discontinuum model: computed steel casing pressure and steel critical thickness are similar.
- The pressure applied on the steel casing may go up to 8-9 MPa.
- Casing behavior and average pressure evolution are dominated by corrosion.
- Modeling of initial fractures induced by the excavation in 3DEC (joint) and in FLAC3D (weaker macroblock) leads to different claystone equivalent stiffnesses in the horizontal and vertical direction, thus affecting the casing ovalization direction (Figure 2).