“This core of enriched uranium, approximately the size of a cantaloupe, would weigh about thirty-three pounds. They could also construct a weapon from the even heavier element of plutonium—produced via a neutron-capture process using U-238. A plutonium bomb would need far less critical mass, and the plutonium core might therefore weigh only eleven pounds and appear no larger than an orange. Either core would need to be packed within a thick shell of ordinary uranium the size of a basketball.”