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

Area of Science:

• Environmental Science
• Nuclear Chemistry
• Geology

Background:

• Depleted uranium (DU) presents complex challenges at the intersection of radioactive waste management, resource policy, and environmental radioactivity.
• While DU has low initial specific activity, its persistence, chemical toxicity, and radiological evolution over geological timescales pose significant disposal hurdles.
• Existing regulatory categories (e.g., low-level waste) are insufficient for resolving the final disposal of large, concentrated DU inventories.

Purpose of the Study:

• To examine the ambiguity in depleted uranium disposal routes and its environmental radioactivity consequences.
• To synthesize institutional and technical evidence regarding DU disposal from various international sources and stewardship examples.
• To clarify that DU disposal adequacy depends on specific inventory, waste form, site conditions, and assessment timescales, not solely on classification.

Main Methods:

• Review of institutional and technical evidence from the United States, France, the United Kingdom, Germany, and the Netherlands.
• Analysis of International Atomic Energy Agency (IAEA) materials and European classification studies.
• Examination of near-biosphere uranium and depleted uranium stewardship examples.

Main Results:

• The record on DU disposal is fragmented but consistently indicates that classification alone does not settle disposal issues.
• Different systems employ varied approaches, including LLW-type disposition, resource retention, or planning for long-lived waste disposal.
• No single disposal method is universally applicable; surface/shallow, intermediate-depth, or geological disposal must be justified for specific DU inventories.

Conclusions:

• Depleted uranium disposal is not resolved by classification alone, necessitating a case-by-case safety demonstration.
• For large DU inventories, safety cases must address uranium mobility, daughter-product ingrowth, radon, groundwater transport, intrusion, erosion, chemical toxicity, and long-term uncertainties.
• A credible safety assessment tailored to specific conditions is crucial for determining the adequacy of any proposed DU disposal route.