half hour after a burst, the principal contributor to induced radiation is
radioactive aluminum. Almost all soils contain aluminum since it is one of
the most abundant elements. Radioactive aluminum has a short half-life, so
that within one-half hour after burst almost all the radioactive aluminum
has decayed.
Most soils also contain significant quantities of manganese
which decays with a half-life of about 2.6 hours. From one-half hour until
10 to 20 hours after burst, both manganese and sodium are the principal
contributors to the radiation. After 10 to 20 hours, sodium, which decays
with a half-life of about 15 hours, is the principal source of radiation.
2.
Considerations of the Operational Level.
A commander will desire to expose his unit to as little radiation as is
compatible with the military situation.
The commander may know the
approximate ground zero of recent or planned nuclear detonations and will
select, if possible, a course of action that will avoid the expected areas
of significant tactical advantage may cause a commander to move the unit
through an area of induced radiation. Also, a radiologically contaminated
area may be encountered unexpectedly. The following is a discussion of aids
available to the commander and some suggested courses of action.
a. Aids to the Commander.
(1) Boundary and extent of area.
The boundary of the significant area of induced activity is considered to be
the distance to which a 2 cGyph dose rate 1 hour after burst will extend.
The maximum horizontal radius of this dose rate contour, for yields of 1 MT
or less at times later than 1 hour after burst, is about 1,400 meters; it is
usually substantially less, depending on the yield and height of burst of
the weapon.
(2) Indications of ground zero direction.
The circular symmetry of some types of damage
such as scorching, tree
blowdown, or other blast phenomena may be visible.
In addition, the reverse
sides of objects or shadowed objects normally will
not be burned. Since the
severity of these damage patterns increases in the
direction of ground zero,
examination of the damage may reveal the direction
of ground zero.
5-23
CM5206
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