A circular area determined by using minimum safe distance I as the radius and the desired ground zero as the center from which all armed forces are evacuated. If evacuation is not possible or if a commander elects a higher degree of risk, maximum protective measures will be required.
ZONE I (NUCLEAR)
Meaning of ZONE I (NUCLEAR) in English
DOD English dictionary of military terms. Английский словарь военных терминов DOD. 2012