Absorbing or externalizing uncertainty? Nuclear energy governance architectures and delivery regimes across global reactor builds

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Long construction lead times are a principal driver of nuclear cost escalation and delivery underperformance. Recent research increasingly identifies governance dynamics—including regulatory evolution, institutional instability, and procedural reopening—as important influences on infrastructure delivery. Yet despite shared reactor technologies and similar external shocks, nuclear construction performance varies markedly across countries and historical periods. What remains insufficiently explained is why some governance systems sustain comparatively stable construction trajectories while others experience persistent delay and disruption. This study examines how governance architectures shape the capacity of nuclear delivery systems to adapt under conditions of uncertainty. Drawing on Transaction Cost Theory, the study employs an explanatory sequential mixed-methods design combining regression analysis of 541 completed commercial nuclear reactors worldwide (1954–2020) with a structured comparative analysis of major nuclear states. The quantitative analysis identifies associations between macro-institutional conditions and construction lead times, while the qualitative analysis explains how these broader institutional environments translate into distinct governance arrangements. The findings suggest that differences in nuclear construction performance reflect recurring governance functions shaping system-level adaptive capacity over long implementation horizons. Shorter construction durations are associated with governance arrangements that sustain coordinated adaptation, cumulative learning, stable financing, and durable political authorization, whereas more fragmented and procedurally reopenable systems are associated with greater exposure to renegotiation and disruption. By linking macro-institutional conditions to recurring governance mechanisms, the study advances a governance-centered explanation of variation in nuclear infrastructure delivery and provides a comparative framework for understanding how institutional design shapes complex low-carbon megaprojects.