Radioactivity in the U.S. Rare Earth Supply Chain: Laws, Regulators, and New-Entrant Risk

• Rare earth ores like monazite and bastnäsite often contain thorium and uranium, triggering complex federal and state radioactive material licensing under NRC source material definitions (0.05% threshold) and fragmented TENORM regulations.
• Classification hinges on whether processing is primarily for uranium/thorium extraction: facilities like White Mesa operate under 11e.(2) uranium mill standards, while Mountain Pass uses state environmental permits for naturally occurring radioactivity.
• New rare earth projects face five critical regulatory questions around source material thresholds, TENORM classification, 11e.(2) byproduct status, mixed waste handling, and access to limited low-level radioactive waste disposal facilities.

Rare earths are not born radioactive — but many are mined alongside radioactive companions.

In the United States, rare earth ores such as bastnäsite and monazite commonly contain naturally occurring thorium and, in some deposits, uranium. The U.S. Environmental Protection Agency confirms that rare earth mining and processing can generate Technologically Enhanced Naturally Occurring Radioactive Material (TENORM (opens in a new tab)) — meaning radionuclides whose concentration or exposure is increased through industrial activity.

Monazite concentrates, according to the U.S. Geological Survey, may contain approximately 3–14% thorium dioxide by weight. Whether that concentration translates into regulatory classification depends on ore chemistry, process design, and where uranium and thorium separation occurs.

Depending on the flowsheet, mixed rare earth carbonate intermediates may retain associated radionuclides, or radionuclides may concentrate into residues, tailings, or other process wastes. That technical distinction — not product labeling — determines regulatory status.

The Legal Pivot Points: Source Material and 11e.(2)

Under the U.S. Nuclear Regulatory Commission (opens in a new tab) (NRC), “source material” includes uranium and thorium in any physical or chemical form. Ores containing 0.05% or more uranium or thorium by weight meet the statutory definition of source material under the Atomic Energy Act (opens in a new tab) and are regulated under 10 CFR Part 40 (opens in a new tab), either directly by the NRC or by an Agreement State exercising delegated authority.

A separate and more specialized category is 11e.(2) byproduct material — defined as tailings or wastes produced by the extraction or concentration of uranium or thorium from ore processed primarily for its source-material content. These materials are regulated under 10 CFR Part 40, Appendix A, which incorporates long-term stewardship and environmental protection standards derived from EPA’s 40 CFR Part 192 under the Uranium Mill Tailings Radiation Control Act (UMTRCA). (opens in a new tab)

The operative phrase is “processed primarily for its source-material content.” Rare earth facilities are not automatically uranium mills. If uranium or thorium extraction is incidental to rare earth production, residues may not fall under 11e.(2), even if they contain radionuclides. Classification depends on the purpose of processing and material characteristics — a critical legal hinge point for project design and permitting.

Additionally, downstream concentration of uranium or thorium during processing can itself elevate materials above the 0.05% threshold, potentially triggering licensing even if the original ore was below that level.

TENORM: A Fragmented Regulatory Landscape

TENORM is not comprehensively regulated under the Atomic Energy Act. Instead, oversight often falls to states, creating what the National Academies of Sciences, Engineering, and Medicine (opens in a new tab) has described as a regulatory “patchwork.”

The NRC’s Agreement State framework delegates authority to participating states to regulate source, byproduct, and special nuclear materials. Utah and Texas are both Agreement States. States also regulate certain non-AEA radioactive materials and frequently rely on model regulations developed by the Conference of Radiation Control Program Directors (opens in a new tab), including dedicated TENORM provisions.

In practice, rare earth operators may encounter layered oversight involving:

• NRC or Agreement State radioactive materials licensing
• EPA hazardous waste regulation under RCRA
• State environmental permitting (water discharge, air quality, tailings management)
• U.S. Department of Transportation Hazardous Materials Regulations (opens in a new tab) (49 CFR Parts 171–180), governing radioactive material transport

This overlap reflects jurisdictional layering rather than redundancy.

What Enforcement Looks Like in Practice

Where a radioactive materials license applies, 10 CFR Part 20 requires:

• A radiation protection program
• ALARA (As Low As Reasonably Achievable) controls
• Dose limits of 5 rem per year for adult workers and 0.1 rem per year for members of the public from licensed operations

Waste disposal frequently becomes the binding constraint. Only four commercial low-level radioactive waste (LLW) disposal facilities currently operate in the United States. Access may be limited by interstate compact membership, waste classification, and facility-specific acceptance criteria under the Low-Level Radioactive Waste Policy Amendments Act of 1985.

Rare earth hydrometallurgical processing can also generate “mixed waste” — material that is both radioactive and chemically hazardous. Such waste is regulated under both the Atomic Energy Act (radiological component) and the Resource Conservation and Recovery Act (hazardous component).

Case Studies: Current U.S. Operators

Energy Fuels Resources (USA) Inc. — White Mesa Mill (Utah)

Energy Fuels operates the White Mesa Uranium Mill under Radioactive Materials License UT1900479 (opens in a new tab), issued by the Utah Division of Waste Management and Radiation Control.

White Mesa is a licensed uranium mill authorized to process uranium- and thorium-bearing materials. The company has publicly disclosed processing monazite concentrates to produce mixed rare earth carbonate while managing associated uranium and thorium under its existing mill license. Because White Mesa manages 11e.(2) byproduct material, tailings, and byproduct disposal are governed by uranium mill standards under 10 CFR Part 40, Appendix A, including long-term stewardship and environmental performance requirements.

MP Materials Corp. — Mountain Pass (California)

MP Materials’ Mountain Pass operation is regulated primarily under California environmental permitting frameworks, including oversight by the Lahontan Regional Water Quality Control Board (opens in a new tab). Regulatory documents acknowledge naturally occurring radioactivity associated with uranium-238 and thorium decay series radionuclides in ore and tailings.

Mountain Pass is regulated through state environmental and radiation control mechanisms and is not publicly characterized by regulators as an 11e.(2) uranium mill tailings operation subject to 10 CFR Part 40, Appendix A. Its compliance posture reflects management of naturally occurring radioactive material rather than the uranium milling law.

USA Rare Earth, Inc.

USA Rare Earth has emphasized a downstream strategy, including a magnet manufacturing facility in Stillwater, Oklahoma, and mining rights at Round Top in Texas.

Texas is an NRC Agreement State. Possession of source material meeting NRC’s regulatory definition would require licensing through the Texas Department of State Health Services, with environmental oversight from the Texas Commission on Environmental Quality. The downstream magnet facility is not inherently radioactive; however, upstream extraction or processing at Round Top would require regulatory evaluation based on uranium and thorium concentrations and resulting waste streams.

What New Entrants Must Get Right

For new rare earth operators, regulatory exposure hinges on at least five threshold questions:

1. Do any process streams exceed the 0.05% uranium/thorium source material threshold?
2. Are residues classified as TENORM under applicable state rules?
3. Does any waste qualify as 11e.(2) byproduct material?
4. Will any material be classified as “mixed waste” under both RCRA and the Atomic Energy Act?
5. Is there an available, licensed disposal pathway with compact access and waste-class compatibility?

These are not academic distinctions. Disposal capacity is finite. Licensing timelines can exceed financing windows. Misclassification can trigger enforcement actions, operational delays, or facility redesign.

The U.S. rare earth revival depends not only on metallurgical capability and magnet demand, but on disciplined regulatory strategy grounded in radiochemistry. In this industry, chemistry determines classification. Classification determines jurisdiction. And jurisdiction determines whether a project advances — or stalls.