Fuel issues: Replacement of HEU

Full text: Research reactors play a vital role in medical/agricultural/industrial applications and in fundamental scientific research. However, many of them use fuels or targets containing high-enriched uranium (HEU) that could be used to make nuclear weapons. In response to this concern, the USDOE initiated the Reduced Enrichment for Research and Test Reactors (RERTR) program in 1978, to develop the technical means to convert these reactors to low-enriched uranium (LEU) materials and to facilitate such conversions worldwide. The HEU materials from the converted reactors are to be returned to the countries of origin through parallel programs. The key to making conversions feasible lies in developing fuels with much greater uranium content, because in LEU every atom of 235U must be accompanied by approximately four atoms of 238U. The RERTR program has developed plate-type fuels with progressively greater uranium densities than the original maximum density of 1.6 g/cm3, and is now developing fuels that can reach 8.0 g/cm3 (U-Mo dispersion) and 16.0 g/cm3 (monolithic UMo). In addition, LEU targets and processes have been developed to produce 99Mo without using HEU. Extensive cooperation with Russian institutes aims to develop new fuels and analyses for LEU conversion of Russian-designed research reactors. Information about existing research reactors was collected, and computer codes were developed to study reactor performance with LEU fuels. The results were incorporated in a series of IAEA Technical Documents providing an internationally accepted set of guidebooks for core conversions. Thirty-nine research reactors have been converted to LEU fuels, or are in the process of doing so. In addition, 14 new research reactors have been built using LEU fuels developed by the RERTR program, and six more are under construction or planned. Cumulatively, use of more than 4,000 kilograms of HEU has been avoided by using RERTR fuels. The events of September 11, 2001, have increased greatly the urgency with which the goals of the RERTR program are to be pursued. On May 26, 2004, U.S. Energy Secretary Spencer Abraham announced at the IAEA a new important initiative - The Global Threat Reduction Initiative - and urged international cooperation. The RERTR program, the FRRSNF for acceptance of U.S. materials, and the RRRFR for acceptance of Russian materials, are crucial components of the new initiative that aims to secure, remove or dispose nuclear and other radioactive materials throughout the world that are vulnerable to theft by terrorists. (author)