After Brussels, leaders tackling threat of nuclear terrorism

WASHINGTON (AP) — Still reeling from attacks in Brussels and Paris, world leaders are wrestling this week with the chilling prospect of the Islamic State group or other extremists unleashing a nuclear attack on a major Western city.

Preventing terrorists from obtaining nuclear materials is the central focus as President Barack Obama hosts leaders from roughly 50 countries for a nuclear security summit starting Thursday.

Despite three previous summits and six years of Obama's prodding, security officials warn that the ingredients for a nuclear device or a "dirty bomb" are alarmingly insecure.

Decades after the Cold War, the threat of a nuclear war between superpowers has given way to growing concerns about non-state actors, including Islamic State and al-Qaida offshoots operating in North Africa and in Yemen and Saudi Arabia.

Easier to pull off would be for IS or another group to obtain fissile material like highly enriched uranium, then turn it into a crude nuclear device delivered by truck or ship.

The most likely scenario that security experts fear is that a group could get ahold of radioactive material, such as cesium or cobalt, for a dirty bomb that could be carried in a suitcase.