The most difficult challenge for a terrorist organization seeking to build a nuclear weapon or improvised nuclear device is obtaining fissile material, either plutonium or highly enriched uranium (HEU). Experts acknowledge that obtaining HEU, uranium that has been processed to increase the proportion of the U-235 isotope to over 20%, is the most difficult challenge facing a state or non-state actor seeking to build a nuclear explosive. The large stocks of HEU in civilian use, many not adequately protected, are thus one of the greatest security risks facing the global community at present....
The most difficult challenge for a terrorist organization seeking to build a nuclear weapon or improvised nuclear device is obtaining fissile material...
