Humanity's uranium-238 inventory: A significant and enduring gamma-radiation liability

Abstract Uranium-238 (U-238), accounting for 99.3% of naturally occurring uranium, primarily utilized for nuclear energy production, is also used in civilian and military applications, leading to vast, geographically dispersed stocks across different byproduct streams. While traditional risk assessments focus on chemical toxicity and alpha radiation, the gamma risks from the U-238 decay chain remain overlooked. Using dose-progression modeling and secular equilibrium analysis, this work quantifies the timeline and magnitude of U-238-induced gamma hazards from depleted uranium (DU), spent fuel (SF), and mill tailings. Findings show that gamma emissions from U-238 inventories exceed radiological safety thresholds well before secular equilibrium, necessitating revised risk assessments and improved, durable containment strategies. By highlighting this underexplored health and environmental issue in nuclear science, the study emphasizes the persistent challenge of managing Humanity's U-238 inventory, which represents a significant and enduring gamma liability across all timescales. Notably, only about 8% of this inventory is managed under robust long-term plans, while the remaining 92%, comprising DU and U-238 in mill tailings, remains inadequately prepared for the future. Addressing the gamma hazards of U-238's decay chain requires a paradigm shift in how this radionuclide is managed. Key priorities for action are identified.