EVENT
AND
DESCRIPTION OF EXPOSED GROUPS
relationship to the surface dose and depth dose
as does the air dose measured in a “point source”
beam in the clinic or laboratory.
It would
9
source” beam air doses with comparable bio-
logic effect are obtained:
Rongelap, Group I._-_----
260 Yr
appear under these circumstances and in most
Ailinginae, Group [I____----
100 r
experimental conditions that the midline dose,
Rongerik, Group III ------
120 r
rather than dose measured in air, would be the
Utirik, Group IV__--_-_----
20 r
r|
:
4m EXPOSURE,
c
MANY SOURCES
5
RATIOIS6
|
BILATERAL EXPOSURE,
DIVERGING SOURCE
1.35
oe
59%
, 2
a an
} L
a
PER CENT AIR DOSE AT SURFACE
i00
0
5
Id
15
20
25
30
36
CM MASONITE
DEPTH DOSE DISTRIBUTION IN CYLINDRICAL PHANTOM, co FACILITY, (NMRI)
FIGURE 1.4—Comparison of depth dose curves in masonite phantoms from
bilateral exposure to a single point source, and simulianeous exposure to
multiple sources with a aspherical distribution around the phantom.
better common parameter in terms of which to
predict biological effect. On this assumption,
the air dose values stated in Table 1.1 should be
multiplied by approximately 1.5 in order to
compare their effects to those of a given air
dose from a “point source” beam geometry delivered bilaterally. If this is done, assuming
a fallout of 12 hours, the following “point
381712 O—56-——2
500 .tGa
ro
The geometry of radiation from a fallout field
is not identical either to the geometry of bilateral point sources or spherically distributed
sources since the plane source delivers the radiation largely at a grazing angle. However, the
total field situation is better approximated by
solid than by plane geometry. Exposure geometry in a radioactive cloud would be spherical.