The global non-proliferation regime faces complex and wide-ranging proliferation threats on many fronts, including the most urgent danger posed by high-consequence nuclear terrorism. Many argue that even a single incident of nuclear terrorism could forever change the world as we know it. Hundreds of metric tonnes of highly enriched uranium (HEU) and plutonium are used annually at nearly 350 different sites in more than 60 countries. This widespread use of HEU constitutes serious proliferation risks. The fundamental challenge for the international community is to deny terrorist organisations the means to steal fissile material needed to build a crude nuclear weapon — an improvised nuclear device (IND). Efforts must be focused more on securing and completely eliminating the vast quantities of HEU globally because it is well within the technical reach of terrorist organisations like al Qaeda to manufacture a ‘gun-type’ IND, if they acquire just a few kilogrammes of weapons grade or near weapons grade HEU. According to the International Panel on Fissile Materials (IPFM), as of January 2013, the global stockpile of HEU is estimated to be about 1.390 tonnes, of which more than 50 tonnes is material situated in civilian research reactors. Some of the material is very poorly secured, making it an ideal target for terrorists. Experts are of the view that uranium enriched just above 60 percent can also be used to produce a small-scale detonation. The gun-type atomic bomb dropped on Hiroshima in 1945, for example, used 80 percent enriched uranium. Although the US and Russia possess much of this material, there are over 25 other countries that also possess significant quantities of weapons-usable material. Against this backdrop, the most logical step to combat nuclear terrorism is the total phase-out of civilian commerce in HEU. It is a well-known fact that HEU is not needed for the generation of civilian nuclear power and is only used as fuel for some research reactors and critical assemblies. And in most of these research reactors, low-enriched uranium can be substituted for HEU. A comprehensive reactor conversion process generally involves three major steps, starting with the development of low enriched uranium (LEU) fuel followed by the conversion of the HEU-fuelled reactor to use the new LEU fuel. In the end, all fresh and spent HEU from the research reactor and associated facilities is completely removed. There are few technical barriers to the conversion from the use of HEU to the use of LEU fuel in civilian reactor operations. The replacement of HEU by LEU fuel typically results in a five to 10 percent decrease in neutron flux but through certain fuel assembly readjustments and core configuration, many research reactors have successfully been converted. According to a recent report from the Washington-based Nuclear Threat Initiative (NTI), 62 HEU fuelled research reactors have been converted to use LEU fuel and 17 reactors have been shut down in 36 countries over the past three decades. All converted reactors included diverse and multiple designs and, in all cases, the neutronic performance of the reactors and their experiments using LEU was considered satisfactory for each level. The international community has taken a number of steps to further the objective of combating nuclear terrorism through reducing global stocks of HEU. In 1978, the US launched the Reduced Enrichment Research and Test Reactor (RERTR) programme to convert HEU-fuelled reactors to LEU. The Department of Energy started a materials consolidation and conversion programme in 1999 to reduce the amount of HEU in potentially vulnerable locations in Russia and other former Soviet Union countries. In May 2004, the US unveiled another programme known as the Global Threat Reduction Initiative (GTRI) designed “to minimise and eventually eliminate any reliance on HEU in the civilian fuel cycle, including the conversion of research and test reactors worldwide from the use of HEU to the use of LEU fuels and targets.” These programmes have greatly increased global awareness of the risks associated with the use of HEU for research and other civilian purposes. However, despite many significant achievements, the US and other major powers have remained unable to develop a universal consensus on HEU elimination. The IAEA, the organisation involved in reactor conversion and HEU fuel repatriation, has also initiated a series of workshops to tackle technical problems involved in HEU conversion. For these initiatives to be successful, the global community should establish an ‘irreversible elimination norm’. The global community must work together to develop HEU transparency guidelines like those that exist for plutonium used in civilian facilities. Lack of transparency surrounding activities involving HEU minimisation makes it extremely difficult to understand the scope of the problem. Another additional measure to bolster nuclear security could be to encourage voluntary declarations of HEU holdings. Finally, countries must review stockpile requirements for HEU fuel used in naval reactors that power submarines and aircraft carriers. This issue has significant implications for the prospects of HEU elimination because HEU use in naval reactors has been kept out of the ‘elimination debate’. Various operational priorities are keeping the US and Russia from exploring conversion to LEU and massive stocks of HEU remain in reserve for future naval use. Although the US is reviewing its plans for the next generation of nuclear submarines, there is reluctance to consider LEU-fuelled reactors for new boats. Despite a number of formidable technical and political challenges to HEU removal, the fact is that the less HEU exists in civilian research reactors, the less opportunity there is for terrorists to steal the material. In comparison with other non-proliferation initiatives seeking to place limits on fuel cycle technology development, HEU elimination is non-discriminatory in nature because it applies to both nuclear weapons states and non-nuclear weapons states. This added virtue offers a common ground for fostering broad cooperation in reducing a very real threat to international security. The writer is a research scholar and a former visiting fellow at the Monterey Institute of International Studies, California. He can be reached at rizwanasghar7@hotmail.com