What is the appropriate time for countermeasures?

The importance of individual exposure pathways is different in various phases of a nuclear accident. Since a particular countermeasure (i.e. intervention during a nuclear accident) is effective only to a certain exposure pathway, different countermeasures would be required for different phases of the nuclear accident and different exposure pathways.

	Countermeasures in different phases of the nuclear accident Countermeasures Phases of a nuclear accident Early Intermediate Late Evacuation ** * - Sheltering ** * - Control of incoming people and cargo ** ** * Administration of stable iodine ** * - Control of foodstuffs and drinking water * ** ** ** High priority *  Low priority
Countermeasures for different exposure pathways   Exposure Pathway Phases of a nuclear accident Countermeasures External irradiation from plume Early           Inhalation of radioactive materials Intermediate     Contamination of skin and clothing Late     External irradiation from deposited materials       Inhalation of resuspended materials       Ingestion of foodstuffs or drinking water