Historical French fleet of Nuclear Power Plants (NPP) is near end-of-life, with 14 NPPs planned to begin decommissioning by 2035. Despite decade-old calls for more research regarding these activities’environmental impact, very few if any studies were conducted since. Due to the French fleet high-degree of standardization, a prospective investigation regarding the Fessenheim NPP—first large-scale plant to be decommissioned in France, starting 2026—is conducted to identify results of interest beyond this case study.