Dynamic Perturbation Factors in Deep Geological Repository Safety Assessment: Identification and Linkage with the K-FEP Framework

The long-term safety assessment of Deep Geological Repositories (DGR) for high-level radioactive waste has traditionally prioritized the Normal Evolution Scenario (NES). However, guaranteeing robust safety over geological timescales requires accounting for "Dynamic Perturbation Factors (DPFs)"—low-probability, high-consequence events that deviate from expected evolutionary paths. This study identifies 18 key DPFs specific to the geo-environmental context of the Korean peninsula and analyzes their cascading impacts on the repository system using the Korean Features, Events, and Processes (K-FEP) framework.

We defined DPFs as active triggers characterized by abruptness and spatial-temporal uncertainty, capable of exerting multiple impacts on Thermal, Hydraulic, Mechanical, Chemical, and Biological (THMCB) behaviors. Through a systematic classification, we identified 11 natural factors, notably fault reactivation driven by Korea’s high horizontal stress fields and climate change-induced erosion, alongside 7 anthropogenic factors such as future human intrusion (deep drilling).

By mapping these factors to the K-FEP structure, the study elucidates cascading failure mechanisms within the multi-barrier system. For instance, the analysis demonstrates how a seismic event (External Factor) can trigger fault reactivation (Geosphere), potentially shearing canisters and creating new hydraulic pathways for radionuclide migration. The results confirm that DPFs act as critical scenario branching points distinct from the NES. This structured approach provides a scientific basis for developing comprehensive safety cases, refining site selection criteria, and establishing robust design margins against geological uncertainties in Korea.