Radon releases from uranium-mining legacies are commonly evaluated in relation to inhalation exposure. Here, the separate question is whether the ²¹⁰Pb produced from sustained legacy releases could perturb the inventories used to date and interpret soils, sediments, peat and other environmental archives. This paper bounds that possibility and tests the natural-meteoric provenance assumption underlying regional excess-²¹⁰Pb interpretation. Because decay-chain mass balance conserves atoms rather than activity, conversion from a 3.8-day radionuclide to a 22.3-year radionuclide reduces the associated activity source term by λ₂₁₀/λ₂₂₂ ≈ 4.7 × 10⁻⁴. For a documented remediation-era source scale of 10¹⁴ Bq y⁻¹, even complete capture of all generated ²¹⁰Pb over 10⁶ km² would yield only about 0.05 Bq m⁻² y⁻¹, compared with a contextual natural deposition range of 50–200 Bq m⁻² y⁻¹. A complementary source-ratio diagnostic indicates that individual legacies contribute about 10⁻⁴ of the natural radon source within representative continental footprints, while the largest historical district aggregates contribute about 10⁻³–10⁻². Documented legacy releases are therefore unlikely to perturb regional-mean ²¹⁰Pb deposition or the inventories derived from it detectably. Localized source–receptor episodes cannot be excluded, but particulate and erosion-mediated inputs from ²²⁶Ra-bearing residues are the more plausible pathways at facility and catchment scales and may warrant explicit consideration and targeted, pathway-based monitoring.

Depleted uranium (DU) sits at the intersection of radioactive-waste management, resource policy and environmental radioactivity. Its initial specific activity is low, and it may be retained as a potential resource or managed within low-level, low-activity or material-management categories. These categories are useful for regulation and storage, but they do not resolve the final-disposal problem for large concentrated inventories. DU is persistent on geological timescales, chemically toxic, potentially mobile under some groundwater conditions, and radiologically evolving through ingrowth of Th-230, Ra-226, Rn-222, Pb-210, Po-210 and other daughters. This review article examines DU disposal-route ambiguity and its environmental-radioactivity consequences. It synthesises institutional and technical evidence from the United States, France, the United Kingdom, Germany, the Netherlands, IAEA materials, European classification studies and near-biosphere uranium/DU stewardship examples. The record is fragmented but consistent on one point: DU disposal is not settled by classification alone. Some systems use LLW-type disposition, others preserve resource status, and others connect non-reused uranium to long-lived LLW, intermediate-depth or geological-disposal planning. The paper does not argue that nearsurface disposal is generically unacceptable, nor that every DU inventory requires a high-level-waste-type geological repository. Its claim is narrower: the adequacy of surface/shallow, intermediate-depth or geological disposal must be demonstrated for the specific inventory, waste form, site conditions and assessment timescale. For large DU inventories, a credible safety case should address uranium mobility, daughter-controlled pathways, radon, groundwater transport, intrusion, erosion, chemical toxicity and long-term uncertainty.

What counts as safety in deep geological disposal—and what disappears when safety is defined in model terms? This paper re-examines repository safety assessment through canister interception by future drilling, a scenario used in safety cases. In current assessments, this scenario is resolved through short-term radiological exposure of selected receptors, without extending the analysis to environmental fate. Such assessments are internally consistent within a robustness-test logic: they ask whether a localised canister breach would compromise repository isolation. Yet once drilling brings waste material to the surface, that material has already crossed the safety boundary established by repository isolation. Very high doses may be acknowledged within the intrusion scenario, while the longer-term fate of surfaced material remains outside the recognised frame of consequence. Uranium—which dominates spent-fuel mass and persists as both a radiological and chemical hazard—makes this truncation materially visible by allowing the chemical and ecological consequences of surfaced repository material to be examined beyond the short-term radiological exposure frame. Combining a comparative review of Swedish and Finnish spent-fuel safety cases with an environmental illustration of uranium's behaviour after surface release, the paper interprets this truncation as model closure: the convergence of technical closure within the model and administrative closure within regulatory practice, through which open-ended environmental consequences are stabilised as a bounded safety object. It argues for reframing repository safety not only as containment, but as continuity with nature: the capacity to account for the persistence, mobility, and ecological interaction of released materials once they re-enter surface systems.

Uranium's radiological ingestion risk remains underrecognized relative to radium. Using WHO/ICRP benchmarks and ICRP dose coefficients, this study shows that uranium-238 produces about 1.6 times more ingestion cancer risk than radium-226 at guideline concentrations. A U/Ra ratio of ~6 marks the threshold above which uranium becomes the larger contributor to radiological ingestion risk, a condition often met in near-surface environments. These findings indicate that uranium's radiological role has been consistently understated and support its inclusion alongside radium in regulatory and monitoring frameworks. Recognizing uranium's radiological impact alongside radium would also strengthen the coherence of protection frameworks linking nuclear and environmental domains.

Radon-222 ingestion from drinking water is commonly treated as a minor exposure pathway relative to inhalation of radon released into indoor air. This interpretation derives largely from the modelling framework consolidated by the U.S. National Academy of Sciences (NAS), which estimated that ingestion contributes approximately 10% of the total radon-in-water dose. However, the NAS explicitly recognised that the ingestion risk partition is governed by a poorly constrained biological parameter — the fraction of radon absorbed across the gastric wall prior to exhalation — and noted that plausible values could span up to two orders of magnitude. Because this parameter directly determines the ingestion dose coefficient, the widely cited 10% contribution represents a central estimate within a broad admissible range rather than a quantitatively constrained value. Despite this, the 90/10 partition has been embedded in subsequent international guidance without empirical narrowing of the governing biokinetic parameter. In parallel, radon-222 is excluded from total indicative dose screening frameworks for drinking water, reinforcing its marginalisation within ingestion-based assessments. The ingestion coefficient is therefore operationally stabilised in regulatory practice, while its quantitative basis remains sensitive to unresolved biological assumptions. This technical note argues that radon ingestion should not be regarded as a quantitatively resolved exposure pathway from an environmental radioactivity perspective. We show that (i) earlier assessments assigning a larger ingestion contribution remain compatible with the uncertainty bounds acknowledged by the NAS; (ii) standard ingestion models treat in-vivo decay and downstream progeny production as negligible under the same biokinetic assumptions that govern radon absorption and clearance; and (iii) radon dissolved in water functions within the uranium-238 decay chain as a transfer mechanism linking short-lived and longer-lived contributors to ingestion dose. Together, these considerations indicate that the apparent stability of the inhalation–ingestion partition reflects modelling continuity and regulatory convention more than empirical constraint.

A recent paper focused on gamma dose rates from unshielded high-level waste over periods exceeding 1 million years and demonstrated that this waste remains hazardous essentially indefinitely. This paper presents a novel perspective by focusing on the practical requirement of shielding to protect from this hazard. Using concrete as the reference material, this paper shows that the required thicknesses stabilize to several tens of centimeters at 1 million years and must remain robust for each individual spent fuel (SF) and vitrified high-level waste (VHLW) form essentially indefinitely, including relevant fragments. These new results provide an additional perspective on an enduring hazard that has been overlooked in discussions of the choice of fuel cycle and in the design and safety analysis of geological repositories. Further research and data needs are identified. 

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.

While spent nuclear fuel is managed with long-term containment strategies, depleted uranium (DU) and uranium mill tailings (UMT)-which constitute over 90 % of humanity's uranium inventory (HUI)-are generally stored with minimal durable protection. This paper reframes uranium as a planetary-scale chemo-toxic liability and introduces two intuitive, inventory-wide hazard metrics: Dilution Liability (DL)-the volume of water needed to dilute uranium below nephrotoxic thresholds-and Total Lifetime-equivalent Dose (TLD)-the number of human lifetime ingestion doses present in a given stock. DL and TLD expose the scale and persistence of uranium's hazard in simple, policy-relevant terms. A national case study of Finland illustrates how these tools support uranium-inventory liability assessments and open avenues for long-term stewardship, environmental justice, and global accountability. The paper also proposes a common exposure threshold to help unify currently siloed chemical and radiological regulatory frameworks. The analysis reveals a web of international responsibilities across the uranium value chain and proposes differentiated pathways: deep geological disposal for DU, more durable and participatory solutions for UMT, and transparent national accounting as a first step toward shared global governance. Overall, the paper translates a previously invisible, under-regulated hazard into implementable, scalable tools for planetary accountability.

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 signifi cant role of Bi-214. These findings fill a gap in the literature and emphasizethe 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.