Highly enriched uranium and crude nuclear weapons

Nuclear weapons can be constructed with either highly enriched uranium or plutonium. The uranium weapons are less technically demanding and do not require testing. Developing states pursuing a secret weapons programme, and terrorist organisations seeking nuclear capabilities will most likely choose a uranium weapon. The amount of uranium needed to construct one weapon is dependent on the enrichment level of the material. We show that if the enrichment exceeds 80 % in uranium-235, even a crude design could work with less than 80 kg.