- thas producing higher concentrations cf radioactivity in
nearby areas.
:
The distribution of the nearby fallout (several
hundred miles downwind) from high yield wedpons detonated
near the Earth's surface will be determined principally by
the size of the particles formed, their position in the
atomic cloud and stem, and especially on the wind 8
ture at the various altitudes.
The first two
ha
functions of the yield of the bomb and the nati ge of the
surface over which the burst occurs.
Figure On@
presents
one generalised concept of such initial distribution in
the cloud and stem.
The infiuence of the third factor
(wind structure) is qualitatively represented in Figure
~
Two. One example of how wind shear affectsthe digtribus
tionaf fallout from two similar detongtions Me ‘show
Figure Three.
a
NREoe
y he.
tcc.
After the radioactive parttetesteabh. thee
Earth's surface they continue to give off ud;
principal one being penetrating gamma rays, «
§
fons, the
these are
absorbed by the body, a certain amount ofbiological damage
rbed Ph |
incurred, and in general the more radiatioh abso
is
the greater the biological damage. One untque chareétere
istic of fallout material is the decayx9! its’ radioactive
according to the principal of ‘time)~+:
Ths means that
for every seven fold lapse of time after a nuclear detorstion there will be a decrease in activity.
AL
For example, in the event fallout oecurs one
hour after detonation, the activity wil! te only 1/10 of
its initial value by the seventh hour.
“The total possible
out-of-doo:;s ,amma dose accumulated frer te first to the
detonation,
hte *
sixth hour after detonation would be anorcvi-ately the
the sixth hour until a week iater.
rurther,
ex's dose would te owice as iarse as all of
tetal possitiec dose for the entire lifetime
ctive materjal.
To state i* another way, for
ae
a
he fallout octurs one cur or less after
one-hal* or more of the total ossibdle radiation
dose wil] he delivered 1. Ube maxt tue: ty-four nours; but
for areas wshere the faliout occurs a few hours or later
after detonation many days or even weevs would ce required
to accumulate tre maior portion of the radiation dose,
thus providing nore =ine for courtermeasires such as
evacuation or use of =relters.
(more)
aS