: 56
THE BHORTER-TERM BIOLOGICAL HAZARDS OF A FALLOUT FIELD
THEORETICAL CALCULATIONS OF THE GAMMA RADIATION SPECTRUM, BTC.
more than one and onehalf times that of the
previous device. Again, however, the theoretical prediction appears sound.
Figure 18 presents an instance wherein
unmodified theory and measurement do not
agree--especiallyat closer distances. However,
this shot represents a weaponof relatively large
yield, and it is presented as a reminder that
with high yields~-such as more than about 100
198
KT—a ‘phenomenon comes significantly into
play that is relatively unimportant at lower
yields but which cannot presently be dealt
with analytically for inclusion in the unmodified
transport theory. The phenomenon referred
to is the radiation enhancement that is due to
the modification of the previously homogencous
atmosphere by the weapon's blast wave.
~ 19 9
ws
”
3
enhencement amplifies total dose above that
predicted by theory for the unmodified atmosphere; and since it affects fission product
~
x
a
c
2
2
&
\
gammas far more significantly than it affects
nitrogen capture gammas, it also alters the
spectral shape from that predicted by the
methods previously discussed.
In other words, for very large yield woapons
initial gamma doses are much greater than
predicted by the unmodified transport theory;
and furthermore, the dose spectrum is much
“softer’’ or less energetic due to the relatively
decreased contribution of the very “hard”
nitrogen capture gammas at this yield range.
Interestingly enough, however, an empirically
estimated enhancement factor to allow for this
hydrodynamic enhancement effect corrects the
calculated points shown in Figure 18 so that
then theydo fit thefield data.
The analytical method is further supported
by calculations made for the Hiroshima and
Nagasaki bombs. As can be seen in Table I,
the calculated points lie within a few percent
Taste 1-—COMPARISON OF INITIAL GAMMA RADIATIONS CALCULATIONS FOR THE ATOMIC
BOMB IN JAPAN
$
\
This
57
=
“.
a
a
1
“Calculated Dose’ Re.)
Distance from exploston (yd.)
ported in Table 3.8 of
Oughterson & Warren
{7} for bothcities (r)
fn
CC
1
700
100
15
3
0
Doses
fur
both
cities
Gamma doses predicted hy
the
read fromFig. 7.42 of
micthods of this paper (r)
“Effects of Atomne
Weapons” [6] (ry
Ufroshima
Nagasaki
few ef ee eee
750
105
15
4
1
630
105
18
3.5
0. 80
630
98
V7
3.2
0. 73
t Maximum.”
= Fleld Dote
* Calculated Fission Product Gose
= Calculoted Nitrogen Copture Dose
= Calculoted Composite Dose
"
1
SLANT RANGED (yds.)
Fiqurk 18.1? vs D plot, comparison with field data,
of the doses predicted by the effects handbook
“Effects of Atomic Weapons” [6] on the basis
of compiled empirical measurements; and they
agree to within less than 10 to 20 percent error
with the essentially identical values quoted by
Oughterson and Warrenin their book, “Medical
Effects of the Atomic Bomb in Japan.” {7]
FALLOUT BOMB GAMMA RADIATIONS
Since the field data on initial gammaradiation
seem generally to confirm the validity of the
transport theory approach, it is particularly
appropriate at this fallout conference to pursue
the application of the transport theory method
to fallout gamma dose and spectrum.
The
geometryof fallout as represented by aneffectively infinite plane source of radiation is
amenable to theoretical treatment. Data can
be presented in a fashion analogous to that
previouslyutilized for the effective point source
geometry.
For example, Figure 19 shows a differential
dose spectrum calculated for a height of 3