from induced radiation was not considered in determining the extent of Zone
I. (Figure 3-2).
b. Secondary Hazard (Zone II).
Zone II delineates the area of secondary hazard and is called Zone of
It is defined as a zone within which the total dose
received by exposed, unprotected personnel is not expected to reach 150
centigrays within a period of 4 hours after the actual arrival of fallout,
but within which personnel may receive a total dose of 50 centigrays (the
negligible risk dose), or greater, within the first 24 hours after the
arrival of fallout.
However, only a small percentage of the personnel in
the zone are expected to receive these doses. The exact dose personnel will
receive at any location within Zone II is dependent upon the dose rate at
their location, the time of exposure, and protection available. Personnel
located close to the extent of Zone I will normally receive higher doses
than those located close to the extent of Zone II. (Figure 3-2) Personnel
with no previous radiation exposure may be permitted to continue critical
missions for as long as 4 hours after the actual arrival of fallout without
incurring the emergency risk dose.
If personnel in this zone have
previously received significant radiation doses, a cumulative dose of 150
centigrays or more, serious disruption of unit mission and casualty-
producing doses may be expected.
Zone I and Zone II