Quantitative Risk Assessment for High-Pressure CO2 Pipelines: The Role of Modelling and Human Harm Criteria

Quantitative risk assessment (QRA) of high-pressure CO2 pipelines depends on a chain of assumptions concerning failure frequencies, transient release modelling, near-field transformation, atmospheric dispersion, and human-harm criteria. This paper presents a problem-oriented review of these modelling stages and proposes criteria for evaluating model applicability, validation range, computational requirements, and coupling consistency. The review is supplemented by an illustrative case using the DNV Phast 8.61 Long Pipeline model and Unified Dispersion Model for five perforation diameters and four concentration levels. Dangerous toxic load calculations yielded equivalent constant concentrations of 64,033–114,353 ppm for fatality probabilities of 1–50% and exposure durations of 5–30 min. Increasing the assumed exposure duration from 5 to 30 min reduced the equivalent thresholds by approximately 20.1%. Under the adopted perforation-size weighting, the 30 mm class accounted for 69.4% of punctures, showing that the largest analysed perforation does not necessarily carry the largest frequency contribution. The case is illustrative rather than site-specific and does not benchmark alternative models. The proposed framework supports transparent, proportionate QRA for pipeline design, land-use planning, emergency preparedness, and sustainable CCUS deployment.