Key Features of Enrichment & Reprocessing Plants

Uranium enrichment is an essential part of the light water reactors (LWRs), advanced gas-cooled reactors (AGRs) and high-temperature reactors (HTRs) fuel cycle. Of these, the LWRs are most widely used. However, the uranium enrichment process has been the only part of the nuclear fuel cycle that has been kept under strict secrecy and control. The reasons are obvious. It can be seen from Figure 1 that the five nuclear weapons states have used uranium-235 (U-235) in their first fusion devices and three weapons states, including the two new ones, have used U-235 in their first fission bombs. While highly enriched U-235 has been used to start the fusion reaction in the thermonuclear weapons, Pu-239 would also trigger such a reaction. Should a country decide to start its nuclear weapons (fission weapon) programme with U-235 as the fissile material, then the acquisition of an enrichment facility becomes essential. The uranium for a nuclear weapon is enriched to at least 50 per cent and it is generally assumed that the fissile material used by nuclear weapon powers in their uranium weapons contains uranium enriched to at least 90 per cent.

Several methods for isotope separation were known even before nuclear fission was discovered. The aim of enrichment is to increase the proportion of fissile U-235 atoms within uranium. The most common methods are the gaseous diffusion and centrifuge processes. Two other technologies that are proliferation-prone are the jet nozzle process developed in Germany and the advanced vortex tube process that was patented in the United States in 1968 and developed further by South Africa. While both these are proliferationprone since, among other things, they require a lower level of technology and are therefore attractive to countries less technologically developed, they may be difficult to monitor by satellite based remote sensing.