Nuclear fuelEnding civilian use of highly enriched, weapon-grade uranium

Published 9 February 2016

Efforts to convert civilian research reactors from weapon-grade highly enriched uranium (HEU) to low enriched uranium (LEU) fuels are taking significantly longer than anticipated, says a report from the National Academies of Sciences. The report calls for the federal government to take immediate steps to convert civilian research reactors currently using weapon-grade HEU fuel to a lower-enriched HEU fuel while awaiting the qualification of new LEU fuel.

Efforts to convert civilian research reactors from weapon-grade highly enriched uranium (HEU) to low enriched uranium (LEU) fuels are taking significantly longer than anticipated, says a report from the National Academies of Sciences, Engineering, and Medicine. The report calls for the federal government to take immediate steps to convert civilian research reactors currently using weapon-grade HEU fuel to a lower-enriched HEU fuel while awaiting the qualification of new LEU fuel. Additionally, the White House Office of Science and Technology Policy (OSTP) should develop a long-term strategy to evaluate future civilian needs for neutrons to meet U.S. science and technology objectives and how these could best be provided by research reactors and other sources, said the committee that conducted the study and authored the report.

The NAS reports that since 1978, U.S. policy and reactor conversion programs have worked to minimize, and phase out where possible, the use of HEU in fuel for civilian research reactors. These reactors use weapon-grade HEU — which is enriched to 90 percent or greater uranium-235 — to produce neutrons vital to research and other civilian applications. Eliminating HEU use in these reactors by converting them to fuel containing LEU — enriched to less than 20 percent uranium-235 — would reduce the risks that this material could be diverted for illicit use, for example in nuclear explosive devices. Worldwide, over 90 civilian research reactors have been converted to LEU fuel or shut down. However, 74 civilian research reactors, including eight in the United States, continue to use HEU fuel.

Obstacles for converting the remaining civilian research reactors from HEU to LEU fuel are both technical and nontechnical, the report notes. Some reactors using HEU fuel require the successful development of new, higher-density LEU fuel to maintain performance after conversion; these reactors are referred to as high performance research reactors. For others, progress toward conversion is hindered by nontechnical obstacles such as economic and political motivations.