HEU Reactor Conversion

September 17, 2016


The Board of the American Physical Society supports the crucial need to reduce, with the goal of ultimately eliminating, the use of highly enriched uranium (HEU) to fuel civilian research reactors as called for by the National Academies of Sciences, Engineering, and Medicine in its 2016 report Reducing the Use of Highly Enriched Uranium in Civilian Research Reactors. Since HEU can be readily used to construct nuclear weapons, minimizing it as a fuel in civilian reactors is an important step toward reducing proliferation risks in the United States and throughout the world.


Low-energy neutrons from research reactors are essential for research in science, engineering and medicine. They are invaluable for research in fields including material science, nanotechnology, chemistry, high-Tc superconductivity, polymer science, and archaeology. They are also critically important for testing of materials, such as those used in nuclear power reactors, and for producing radioactive isotopes used in medical treatments and various industrial applications.

Currently, neutrons are produced by reactors either fueled by highly enriched uranium (HEU) or fueled by low enriched uranium (LEU). Some neutron applications require intense, bright sources of neutrons that, at this time, can be provided only by HEU-fueled reactors. However, HEU can be readily used to construct nuclear weapons and consequently every HEU reactor presents a significant proliferation risk. In contrast, LEU cannot be easily converted into a material to make a nuclear weapon.

It is therefore urgent to reduce, with the goal of ultimately eliminating, the use of highly enriched uranium (HEU) without detracting from the essential science and engineering enabled by neutron sources. Possibilities include developing new reactor fuels based on low-enriched uranium (LEU), and converting HEU reactors to operate on LEU fuel. In addition, enhanced security measures need to be developed in order to balance the need for continued access to the unique capabilities provided by research reactors with the imperative to reduce proliferation risks. The National Academies report urges further study of ways in which the use of HEU in civilian reactors can be minimized. Possible methods include using spallation neutron sources where practical, converting some HEU-fueled reactors to high-density LEU fuel, design and construction of reactors designed to operate using LEU fuel, and increasing the efficiency of the remaining HEU facilities for studies and applications that require the high fluxes from HEU reactors. Scientific input is needed to realize the simultaneous goals of minimizing HEU proliferation risks and continuing excellent science through reactor neutrons.