Depleted uranium final disposal: why classification does not settle long-term safety for large inventories

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 near-surface 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.