ighly enriched uranium (HEU) is used for two major civilian pur­poses: as fuel for research reactors and as targets for medical isotope production. This material can be dangerous in the wrong hands. Stolen or diverted HEU can be used—in conjunction with some knowledge of physics—to build nuclear explosive devices. Thus, the con­tinued civilian use of HEU is of concern particularly because this material may not be uniformly well-protected.

This report focuses on the civilian use of HEU for research reactor fuel. It summarizes the proceedings of a joint symposium organized by the National Research Council of the U. S. National Academies and Russian Academy of Sciences (RAS) to address progress, challenges, and opportu­nities for converting U. S. and Russian research reactors from HEU to low enriched uranium (LEU) fuel. This symposium—held in Moscow on June 8-10, 2011—was sponsored by the U. S. Department of Energy-National Nuclear Security Administration’s (NNSA) Office of Defense Nuclear Nonproliferation.

This report provides a summary of the symposium presentations and discussions; it does not represent a consensus of the symposium participants or the authoring committees.1 Many important points were made by indi­vidual participants during the symposium,[1] [2] particularly regarding possible future actions for reducing or managing the proliferation risks posed by

HEU-fueled U. S. and Russian research reactors. These points include but are not limited to the following:

• Many symposium participants from both the United States and Russia emphasized the importance of reducing and, where possible, elimi­nating the use of HEU in research reactor fuel. Participants noted that conversion of research reactors to LEU fuel provides for permanent threat reduction and may reduce the requirements for (and potentially the costs of) facility security.

• Research reactors currently serve important purposes for research and industry, and they will continue to serve important purposes into the future. Prominent examples include medical isotope production and re­search associated with the design of next-generation nuclear plants.

• The United States and other nations have been able to convert research reactors to LEU fuel while maintaining their performance for key missions. In fact conversions of research reactors in the United States have resulted in improved understanding of their operating characteristics and, in some cases, improved performance. In the United States, all reactors that can be readily converted with existing LEU fuels have been converted. Many symposium participants observed that conversion studies of research reactors in Russia has started but conversion is lagging behind the United States.

• The economic and performance challenges associated with conver­sion are likely to be surmountable in many cases, particularly with govern­ment assistance and the involvement of reactor operators and customers.

The development of higher-uranium-density LEU fuels could reduce fears of loss of performance by reactor customers.

• Collaboration between the United States and Russia on conver­sion of research reactors has been and is likely to continue to be valuable.

Several participants noted that collaborative U. S.-Russian work on fuel development has provided opportunities to advance conversion of both countries’ reactors. Additionally, the United States has already confronted regulatory challenges associated with conversion. This experience could be useful to Russia.

• Some facilities may not be easily convertible to LEU fuel, includ­ing fast spectrum reactors, fast critical assemblies, reactors with small core volumes, and reactors with high specific power per unit volume of active core. The feasibility of conversion depends to some extent on policy choices by host nation governments. Several workshop participants suggested that one way of minimizing the use of HEU for essential or unique missions would be to create major international nuclear centers to house these reac­tors and to ensure that those facilities have strong security and safeguards protections.