The availability of HEU—particularly in the civilian sector—is a sig­nificant proliferation and security concern. In 2001, the U. S. National Research Council stated in its report, Making the Nation Safer, that “(t)he primary impediment that prevents countries or technically competent ter­rorist groups from developing nuclear weapons is the [lack of] availabil­ity of special nuclear material (SNM),[8] especially HEU” (NRC, 2001). The availability of HEU in the civilian sector—as opposed to the military sector—is of particular concern, because resources may not be available or used to protect the material adequately during storage or transport.

If HEU is available, either stolen or purchased, it is plausible that a nuclear weapon could be built by either a state or a non-state actor.[9] The technical barriers to constructing such a weapon are not impassably high. As Pablo Adelfang of the International Atomic Energy Agency (IAEA) noted during the symposium (Adelfang, 2011), individuals with a basic knowledge of physics and machining could build a functioning bomb from stolen HEU. This is largely because HEU is only weakly radioactive—mak­ing it relatively easy to handle—and because such a device would not re­quire explosive testing to be assured of some yield.

In the civilian sector, HEU is primarily used to fuel research reactors and produce radioisotopes for use in medical procedures. The stockpiles of HEU held for these purposes and others are significant. At the end of 2003, the estimated global stockpile of HEU (both civilian and military) was around 1,900 metric tons. Although the vast majority of this HEU is under military control, about 175 metric tons is civilian HEU (ISIS, 2005). This quantity of HEU is sufficient to fabricate about 3,500 nuclear weapons.[10] The vast majority of this civilian HEU is located in the United States (124 metric tons) and in Russia (15-30 metric tons) (ISIS, 2005).

The potential proliferation risk associated with the use of HEU-fueled research reactors—the focus of the symposium and this summary report— arises from the need to transport and store both unirradiated and irradi­ated[11] HEU fuel. This fuel must be protected at all times and is potentially vulnerable to theft while in transit, including across national borders. Proliferation risk exists even in nuclear weapons states.

It is possible to replace HEU in many civilian applications with LEU, which is considered to have a lower proliferation risk because it is not suit­able for use in a nuclear device. Such replacements are possible using cur­rent technologies or technologies that are under development. For example, in 2009, the NRC found that the HEU targets used for the large-scale pro­duction of the medical isotope molybdenum-99 could be replaced by LEU targets (NRC, 2009). Similarly, many existing research reactors can operate using LEU fuel rather than HEU fuel (see Chapters 2 and 3 of this report). In fact, as discussed elsewhere in this report, many reactors have been suc­cessfully converted from HEU to LEU fuel, and many other conversions are under way. The continuation of this trend could significantly reduce the proliferation risk associated with the civilian trade in HEU.

As will be discussed in the next section, 40 percent of the world’s op­erating research reactors are located in the United States and Russia, and nearly all of the world’s research reactors are fueled with either U. S.- or R. F.-origin fuel. For these reasons among others, the United States and Russia combined have significant influence on the nature and extent of the worldwide trade in civilian HEU.