Ballast water management of nuclear wastewater: Tripartite policy analysis

The ocean discharge of treated Fukushima wastewater presents complex governance challenges for radionuclide-contaminated ballast water. This study proposes a tripartite evaluation and optimisation framework targeting flag states, port states, and shipping lines. Stakeholder performance is assessed via PCA-based inspection data, entropy-weighted Cesium-137 diffusion modelling, and ESG-oriented text mining. After Min-Max normalisation, multivariable regression identifies interdependencies, followed by a Nash equilibrium model to simulate strategic responses. To assess robustness, internal sensitivity tests are conducted under policy-driven and market-driven perturbations, while external risks are reviewed to inform scenario extensibility. Results reveal behavioural asymmetries and non-linear interactions: unilateral actions produce trade-offs, but coordinated strategies yield synergistic gains. These findings highlight the importance of a neutral coordinating body to align regulatory sequencing and balance stakeholder responses, supporting stable and adaptive ballast water governance under nuclear risk conditions.