United States Nuclear Regulatory Commission - Protecting People and the Environment
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Source Material

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What is meant by source material?

In general terms, "source material" means either the element thorium or the element uranium, provided that the uranium is not enriched in the isotope uranium-235 above that found in nature. Depleted uranium (a by-product of  uranium enrichment) is considered source material. Source material also includes any combination of thorium and depleted or natural uranium, in any physical or chemical form, or ores that contain by weight one-twentieth of one percent (0.05 percent) or more of uranium, thorium, or any combination thereof.

Where does source material come from?

Source material includes most uranium and thorium ores and product resulting from the milling and concentration of uranium or thorium contained in ore mined for its uranium or thorium content. It can also be generated as a side product during the refining of ores mined for other precious metals. In addition, source material can arise from the reprocessing of spent nuclear fuel (no commercial reprocessing is currently licensed in the U.S.) and also, as depleted uranium (containing lower concentrations of U235 than natural uranium), a by-product of the process of enriching uranium in the isotope uranium-235.

Why is control of source material important?

Congress enacted Title I of the Atomic Energy Act of 1954, as part of President Eisenhower's Atoms for Peace program, including the clause:

"Source and special nuclear material, production facilities, and utilization facilities are affected with the public interest, and regulation by the United States of the production and utilization of atomic energy and of the facilities used in connection therewith is necessary in the national interest to assure the common defense and security and to protect the health and safety of the public."

Natural uranium has a fissile material, uranium-235, that can be concentrated (i.e., enriched) to make highly enriched uranium, the primary ingredient of some nuclear explosive designs. Natural uranium can also be used as fuel in graphite and heavy water reactors, or as a target in a reactor to produce plutonium, principally plutonium-239. Plutonium extracted and processed from reactor fuels or targets can be used in some types of nuclear explosives. Thorium can be used in the fuel or as a target in certain reactor designs to produce uranium-233, which is subsequently burned in the nuclear reactor or could be extracted for use in a nuclear explosive.

Misuse of nuclear materials intended for peaceful purposes to create a nuclear explosive is illegal. The NRC regulates source material to prevent misuse, to provide for the common defense and security, and to protect the health and safety of the public.

Source Material Regulations

The NRC regulates peaceful use of source material through licensing and oversight of licensee operations. Some of the regulations that pertain to source material possession or use are shown in the following table.

Subject Code of Federal Regulations
Radiation Protection Standards 10 CFR Part 20
Licensing of Source Material 10 CFR Part 40
Implementing US-IAEA Safeguards Agreement 10 CFR Part 75

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Page Last Reviewed/Updated Wednesday, November 16, 2016