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Humanity’s uranium-238 inventory : a significant and enduring gamma-radiation liability

Pescatore Claudio

Nukleonika

2025

Vol. 70, No. 2

31--42

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.

Beyond one million years : the intrinsic radiation hazard of high-level nuclear wastes

Pescatore Claudio

Nukleonika

2024

Vol. 69, No. 4

215--224

This paper highlights the absence of quantitative estimates regarding the intrinsic radiation hazard of high-level nuclear wastes, namely, spent fuel (SF) and vitrified high-level wastes (VHLW), for periods exceeding one million years. Using available data, conducting scoping calculations of radiation doses, and comparing the results to radiation protection guidelines and natural background radiation, this paper shows that high-level wastes cannot be safely handled or left unprotected essentially indefinitely. By quantitatively evaluating the dose rates of unshielded SF and VHLW, this study identifies critical new insights, such as the roles of the Np-237 decay chain; the eventual, long-term dominance of the U-238 decay chain; and the interplay of three actinide decay chains, including the significant role of Bi-214. These findings fill a gap in the literature and emphasize the need for more detailed investigations in this as-yet-unexplored research area, which has a direct bearing on technical and societal decision-making for both waste disposal safety and the choice of the back end of the nuclear fuel cycle.