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

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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