Explainer: How close is Iran to producing a nuclear bomb?

VIENNA/WASHINGTON (Reuters) - The central achievement of the Iran nuclear deal - keeping Tehran at arm's length from nuclear weapons - is eroding.The 2015 accord's many restrictions on Iran's atomic activities were built around one objective: to extend the "breakout time"Tehran would need to produce enough fissile material for one atomic bomb - if it decided to do so - to at least a year from around 2-3 months.Iran maintains that it has never sought nuclear weapons and never would.