A 'dirty bomb' or radiological dispersal device (RDD) is distinguished from a true nuclear weapon by:

Explanation

An RDD uses conventional explosives to disperse radioactive material — it is NOT a nuclear weapon and does not produce a fission/fusion yield. The immediate damage is primarily the conventional blast; the longer-term concern is contamination of the area, complicating cleanup and causing fear and economic disruption. A true nuclear device produces a fission or fusion chain reaction with catastrophic blast/thermal/radiation effects. Both warrant immediate evacuation and law-enforcement response; only proper training and detection equipment can characterize the threat. Security officers focus on isolating the area and notifying authorities.