GENEVA—The big question over the agreement forged Sunday in this Swiss lakeside city between Iran and the world’s big powers is this: How much will it delay, if at all, Tehran’s ability to produce enough material for a nuclear weapon? Israel argues that as long as Iran can enrich uranium at even a low level, it can elude detection of any clandestine effort toward making higher-level, weapons-grade fuel, and can quickly restore the capacity that it agreed to reduce. The international community has sought ways to ensure that any Iranian move toward a weapon is slowed, and can be caught, though Iran says its activities are for civilian purposes. Even with Sunday’s accord, most analysts believe it would still take only weeks or months to produce enough highly enriched fissile material to fuel a bomb if Iran chose to go all out. Uranium ore in nature is only 0.7% […]