4
TrUrire
.
,
Single I™
131
Intake
re)
lOF
o
oF
e
Prolonged !ntake
3
G2
been
Le
L
>
=
a
o
So
9 OF
a
C
$
=
C
of
:
&
;
Oo.
ad
Ihe
a
a
F
a
Qo
Time from detonation to intake
3
Lo
pet
iO
100
bo
10
Time‘ from Detonation to intake (hr)
__
|
20
fete te ty tity
630 40 50
i
Lt
Loot ta
OOo
200 300400 *500
_Buration of Intoke (hr)
oan
Beno.
~"* 100
FIG. 3. Approximate relative infinity dose to thyroid from short-lived |
isotopes and |!3! for case of prolongedintake. See Table 3 for sample
calculation of these curves
FIG, 2. Approximate infinity dose to thyroid from
single intake of the ['*! and its tellurium precursors
from 10,000 fissions. This figure is used with Table
3 in the preparation of Fig. 3
When ingestion or inhalation of radioactive fallout material occurs,
it is important to be able to estimate the dose received.
Here, for the case of radioiodine, is a procedure for determining
the thyroid dose given present activity or initial intake
c. The intake, along with theI**,
of Tel!" a part of which will
disintegrate within the body to
y{31,
To estimate the original rate of in-
take of I! from a known activity in
the thyroid at a later date, one can
extrapolate according to the physical
of original intake after detonation and
the duration of intake. However,estimates of the effects of ignoring these
two factors indicate that the over-all
Atomie number
131
bl
(Sb)
62
(Te)
58
(I)
o4
(Xe)
28
(Cs)
30 hr
L
25 min—
8.0 day — stable
132
133
~§min- 77hbr — 2.4hr
<10 min— 60 min-> 21
hr
134
<10 min — 43 min — 50.8 min — stable
15.3 min (~10%)
135
<Ilmin—
—- stable
— 5.3 day — stable
6.7 hr
9.2 hr— 2.1
Vol. 14, No. 2 - February, 1956
thus underestimates the original intake. The extent to which these
affect the answer depends upon time
TABLE 1—Isotopes Important to Thyroid Uptake
Mass number
and biological decays of I!*! only.
This method ignores intake factor b
and thus overestimates the original
intake; it also ignores factor ¢ and
108 yr — stable
error would not be any greater than
other inherent uncertainties.
The exact steps are given in the
following sections. Thesymbolsaredefined at the head of page 40. Two
examples are given on pages 40 and 41.
1, Initial rate of intake of P31, Ro.
Assume that the rate of intake decreases according to the physical decay
of the isotope. Then activity in the
thyroid changes with time thusly
dA
7
Roe" — (A, + DA
39