Conversion of research and test reactors: status and current plans

The Office of Global Threat Reduction's (GTRI) Conversion Program develops technology necessary to enable the conversion of civilian facilities using high enriched uranium (HEU) to low enriched uranium (LEU) fuels and targets. The Conversion program mission supports the minimization and, to the extent possible, elimination of the use of HEU in civil nuclear applications by working to convert research reactors and radioisotope production processes to the use of LEU fuel and targets throughout the world. During the Program's 27 years of existence, 46 research reactors have been converted from HEU to LEU fuels and processes have been developed for producing the medical isotope Mo-99 with LEU targets. Under GTRI the Conversion Program has accelerated the schedules and plans for conversion of additional research reactors operating with HEU. Also the Program emphasizes the development of advanced high-density LEU fuels to enable further conversions. The Conversion program coordinates with the other program functions of GTRI, most notably the Removal function, which removes fresh and spent HEU fuel from countries around the world. This paper summarizes the current status and plans for conversion of research reactors, in the U.S. and abroad, the supporting fuel development activities, and the development of processes for medical isotope production with LEU targets. Nuclear research and test reactors worldwide have been in operation for over 60 years, supporting nuclear science and technology development, as well as providing an important role as a research tool in scientific fields including medicine, agriculture, industry, and basic research. Over 270 research reactors are currently operating in more than 50 countries. Starting in 1954, many research reactors outside the United States were provided under the Atoms for Peace initiative. Initial research reactors were fueled with low-enriched uranium (LEU) with a content of U235 of less than 20%. More advanced research reactors desired higher specific power and neutron flux and, to avoid costs associated with the development of higher density LEU fuels, those reactors used high-enriched uranium (HEU) material, with an enrichment of 20% or higher, and typically over 90%, with the existing fuel designs. As HEU fuel became readily available, it turned into the usual fuel for research and test reactors, even for some that had initially operated with LEU fuel.