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

Claudio Pescatore

Claudio Pescatore

Research Affiliate at the UNESCO Chair on Heritage Futures, Linnaeus University, Kalmar, Sweden Formerly Principal Administrator of Radioactive Waste Management and Decommissioning at the OECD
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Pescatore, Claudio
  
02. Mai 2025
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Artikel-Kategorie: Original Paper
Online veröffentlicht: 02. Mai 2025
Seitenbereich: 31 - 42
Eingereicht: 27. Dez. 2024
Akzeptiert: 10. Feb. 2025
DOI: https://doi.org/10.2478/nuka-2025-0004
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© 2025 Claudio Pescatore, published by Sciendo
This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

Fig. 1.

The U-238 decay-chain including gamma emissions. In parenthesis, the not-significant gamma from the decay of U-238 itself.
The U-238 decay-chain including gamma emissions. In parenthesis, the not-significant gamma from the decay of U-238 itself.

Fig. 2.

Secular equilibrium paths of the U-238 decay-chain.
Secular equilibrium paths of the U-238 decay-chain.

Fig. 3.

Evolution of the U-238 chain gamma dose-rate at the surface of an unshielded 238UO2-cylinder 40-cm-tall and 10-cm diameter. Pa-234m dominates at the start and for a few thousand years.
Evolution of the U-238 chain gamma dose-rate at the surface of an unshielded 238UO2-cylinder 40-cm-tall and 10-cm diameter. Pa-234m dominates at the start and for a few thousand years.

Fig. 4.

Gamma dose-rate from uncovered mill tailings as a function of time.
Gamma dose-rate from uncovered mill tailings as a function of time.

Estimated global-tailings U-238 and other relevant parameters

Parameter Value
Global tons of ore or tailings 3 billion tons ore or tailings
Reference uranium content in ore 0.15% (1.5 kg uranium/ton)
Fraction of U-238 in natural uranium 99.3%
U-238 content per ton of ore 1.4895 kg
Recovered U-238 per ton of ore 1.2 kg
Unrecovered U-238 per ton of ore/tailing 0.2895 kg
Conditioned U-238 3.6 million tons
Tailings U-238 868 500 tons
Recovery efficiency from ore 80.6%

Humanity's U-238 inventory in metric tons and curies as of 2022

Category Stock type Metric tons Activity (Curies) Percentage of total-mined (%)
Conditioned U-238 by stock LEU 18 252 6 156 0.41
Reprocessed uranium 127 000 42 799 2.84
Spent nuclear fuel 363 000 122 631 8.4
DU 3 100 000 1 044 700 69.24
Total conditioned U-238 3 608 252 1 216 286 80.6
Tailings U-238 Mill-tailings 868 500 292 700 19.4
Humanity's U-238 Total-mined 4 476 752 1 507 984 100

Global mill tailings estimates by source, date, and key concerns

References Global mill tailings estimate Annual production estimate Major regions affected Key concerns
IAEA [17] Over 900 million cubic meters Not specified North America, Europe, Africa Radon emissions, groundwater contamination, soil erosion
Sutherland [15] Over 1 billion metric tons in the year 2000 (sic) Over 200 million metric tons annually United States, Canada, former Soviet Union areas Radon release, groundwater contamination from in situ leaching
NEA [18] Over 1 billion metric tons Not specified North America, Europe, Central Asia Long-term containment, groundwater protection
NEA/IAEA Red Book [34] Over 1 billion metric tons Not specified North America, Europe, Central Asia Radon emissions, erosion, groundwater contamination

Observed gamma doses from uncovered mill-tailings

Location Gamma dose rate observed Key findings
Bellezane site, France [38] Above 10 μSv/h in certain areas Gamma radiation levels vary by depth and exposure; higher values observed in specific areas emphasize the need for location-specific radiation mitigation strategies.
Tuyuk-Suu, Kyrgyzstan [39] 10 μSv/h and higher in tailings Highlights potential for elevated gamma exposure in legacy uranium processing regions, underscoring radiological risks in abandoned sites.
Former uranium mining sites, Portugal [40] Frequently exceeded 10 μSv/h, peaks at 20 μSv/h Persistent gamma dose rates on tailings surfaces present significant radiological hazards, necessitating ongoing monitoring and potential intervention.
Pridnieprovsky Chemical Plant, Ukraine [41] Up to 10 μSv/h in tailings and buildings High gamma exposure levels detected in tailing areas and nearby structures suggest the need for targeted remediation in legacy milling sites.
Granitic uranium deposit, China [42] Average of 17.79 μSv/h Technologically elevated gamma dose rates in a natural uranium-rich area high-light the potential for occupational and environmental exposure risks.
Uranium mining legacy sites, Portugal [43] 7.5–9.5 μSv/h on tailings piles Gamma radiation from tailings poses long-term environmental and health risks, indicating the persistent impact of historical uranium mining.

Intensity-weighted gamma energy per decay and equilibrium contribution

Isotope Intensity-weighted gamma energy per decay (keV) Contribution at equilibrium (%)
Pa-234m 8.41 0.91
Ra-226 6.10 0.66
Pb-214 189.29 20.49
Bi-214 1076.40 77.94
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