Highly enriched uranium (HEU) is defined as uranium in which the amount of the isotope uranium-235 (U-235) has been increased, or enriched, from the naturally occurring level of 0.7 percent to 20 percent or more. Most of the HEU being blended down by Russia under the HEU deal has an enrichment level of more than 90 percent U-235. Low-enriched uranium (LEU) suitable for use in civil nuclear power reactors, but not usable for bombs, has an enrichment level of about 5 percent U-235.
Under conventional commercial arrangements, a nuclear power utility will purchase natural uranium as uranium oxide (U3O8), have it converted to uranium hexafluoride (UF6), and pay to have it enriched by a seller of enrichment services, such as the U.S. Enrichment Corporation (USEC), to make LEU. The quantity of uranium is typically referred to in pounds U3O8 or, alternatively, kilograms uranium metal (U) contained in UF6. (One kilogram U is equivalent to about 2.6 pounds U3O8.) A kilogram of LEU requires roughly 11 kilograms U as feedstock for the enrichment process and about 7 separative work units (SWUs) worth of enrichment services. At $30 per kilogram the uranium content is worth about $330, and at $90 per SWU the enrichment content is worth about $630.
Another way to make LEU is to blend down HEU by mixing it with natural uranium or uranium at a relatively low enrichment level (for example, 1.5 percent U-235). One kilogram of HEU at an enrichment level of 90 percent U-235 can be blended with about 30 kilograms of uranium to make about 31 kilograms of LEU for nuclear power plants. At current prices, a kilogram of HEU can be made into LEU worth more than $25,000. A typical nuclear weapon contains HEU worth more than $600,000.
When USEC takes delivery of LEU from Russia under the HEU deal, it delivers this LEU to its customers rather than actually enriching the uranium that its customers had previously delivered to USEC facilities for enrichment. In effect, the uranium component contained in the Russian LEU displaces a similar amount of uranium of some Western origin that had been delivered to USEC for enrichment. Under current arrangements, USEC pays Russia for the enrichment services contained in the Russian LEU, and turns over an equivalent amount of its customers' uranium to Russia at USEC facilities.
Because a number of countries impose safeguards and other specific restrictions on the use of their uranium, USEC exchanges "origin" and "obligation" labels between the uranium in the LEU delivered to its customers and the uranium that its customers delivered to USEC. Thus, a utility that delivered Australian-origin uranium to USEC would receive LEU from USEC containing "Australian" uranium (even though that uranium might have been mined decades earlier in the former Soviet Union), while Russia receives back "Russian" uranium (that was actually mined in Australia). For all purposes, including trade restrictions, Russia receives back "Russian" uranium.
Russia may then sell this uranium, subject to the various trade restrictions placed on Russian uranium by the United States, the European Community or other countries. Sale of the uranium outside the United States is complicated by U.S. "prior consent" rights. Under the 1978 Nuclear Non-Proliferation Act, uranium may only be exported if the recipient agrees to obtain U.S. consent for any subsequent use of the uranium, such as enrichment, reprocessing or re-export. Foreign buyers are naturally reluctant to accept such conditions. Russia has expressed interest in taking some of its uranium back to Russia for domestic use. While the United States and Russia do not have an "agreement for cooperation," preventing most nuclear trade between the two nations, the United States can, under special circumstances, ship uranium back to Russia under a different provision of the act. This requires specific actions by Department of Energy and the Nuclear Regulatory Commission. However, any uranium shipped from the United States to Russia still must retain U.S. prior consent rights. —T.N.