fy,
156
the absorbed dose delivered to the stomach in
i hour ig small.
The absorbed dose in the top
portion of the small intestine is the same as
that to the stomach, but decreases during the
4 hours there due to the 60 percent uptakeinto
the bloodstream. ‘The absorbed dose to the
large intestine is much greater than that to the
small intestine because the radioactive material
speuds 8 hours in the upper and 18 hours in
the lower large intestine compared with only
4 hours in the small intestine. Also, the mass
of material in (he upper or lower large intestine
is aboutone-eighth of (hat in the small intestine
ONy=150 gg, Mu (35 g, Mg=1100 g,
Mytomsen*= 250g). In the case of Ra”the 6-hour
daughter, Ac”, makes a large contribution to
the dase. Therise in the dese in the small intestine is accentuated by the fact that the
effective energy of Ac? is 80 times that of the
parent, Ra?*, and there is only 20 percent
absorption from the small intestine into the
blood,
ct
THE SHORTER-TERM BIOLOGICAL HAZARDS OF A FALLOUT FIELD
The slow rise in the absorbed dose in
the upper and lower large intestines in the case
of SP°+¥", and Ra**-+-Ac is the result
of the growth of the 61-hour Y®*, and 6-hour
Ac™® respectively. In the case of the 17.5minute Pr, the absorbed dose is delivered
mostly to the stomach. The dose to the large
intestine is negligible because Pr' passes
through17 radioactive half-lives in the stomach
and small intestine.
The foregoing tables of MPC values maybe
useful in dealing with hazards associated with
the fallout material from the testing of nuclear
weapons as well as the contaminationresulting
from a laboratory spill or accident.
However,
manyof the radionuclides of great interest that
comprise fallout during the early periods follow-
ing the detonation of an atomic weapon were
not included in these tables. There are many
factors that determine the type of fallout
material from the detonation of a nuclear
weapon, e. g., height of burst, distance from
ground zero, typo of weapon, weapon yield,
meteorological conditions, ete. Likewise it has
been found that there maybe factors (physical,
chemical, and biological) which tend to frac-
tionate and concentrate certain of the radio-
INTERNAL DOBE FROM SHORT-LIVED RADIONUCLIDES
157
nuclides. For example, at the first Bikini
underwater test I made a numberof surveys on
the target ships and nearbyislands of the 8/y
dose rate rrtio and found it to range from 1 to
several hundred. This high 6/y dose rate ratio
was, in part, a consequence of the fact that on
the. average there are about twice as many
radiation. In any case, the record should
speak for itsclf- namely, the damage to man
and animals (cattle, horses, deer, etc) that
unless measurements have been made of the
absorbed dose from # and soft + radiation.
Having called attention to the many factors
exposure to hard gamma radiation but from
have risked setting up Table III which lists
the more important U-fission radionuclides that.
disintegration of the U-fission mixture, and
most of the beta particles have a range of less
than a meter in air whereas a large fraction of
the gamma photons have a range in air of
manymeters, i. e., the fraction of photons with
an absorption coefficient d that travel a distance
cautious not to overlook the seriousness of
fractionation.
beta particles as gamma rays emitted per
has been observed from the fallout material
from nucleartests to date has resulted not from
exposure to beta radiation. In assessing the
hazard from fallout, therefore, one must be
exposure to beta radiation, and one should not
rely on a theoretical estimate of the isotopic
distribution or one should not reach final
conclusions regarding the radiation hazard
greater than x is given approximately by the
tain circumstances this fractionation maybe of
considerable importance because overexposure
to beta radiation can lead to serious erythema,
burns, ulcera, and even death. Yet the most
commonly used field survey equipment is
designed to measure the absorbed dose from
relatively hard gammaradiation and may give
little or no response to beta radiation. Following the test of a thermonuclear weapon by the
United States in the South Pacific in 1954, the
more serious cases of radiation damage among
the natives and operating personnel from the
United States: resulting from contact with the
fallout’ materials were the consequence of
exposure to beta radiations. It is sometimes
stated that beta exposureis oflittle importance
compared to the gamma dose from fallout
material and that one would have to be partly
naked or lie prone on the ground before the
beta exposure should be a matter of concern.*
T do not agree with this point of view and dare
say some among the Marshallese, the Japanese
fishormen, and the Americans who received
painful and disfiguring beta burns as a cansequence of exposure to fallout material in the
“South Pacifie would not be inclined to underestimate the seriousness of exposure to beta
“Thereader is referred 1o the final summary ofthis Conference by Dr.
K.P. Cronkite.
would be presentas a function of time following
the detonation of a weapon if there were no
The radionuclides are listed in
order of decreasing availability (assuming no
selective deposition or separation of the radio-
elements) for 5 time intervals—1 hour to 1 day,
1 day to 1 week, 1 week to 1 month, 1 monthto
Tante IIT.--AVAILABILITY OF U-FISSION RADIONUCLIDES
equation (1—e>*). In addition, many common materials such as tar, resin, rusi, paint,
metals, etc., seemed to retain selectively certain
of the beta-emitting radionuclides. Under cer-
which may change the isotopic distribution, I
(Listed in order of decreasing yield)
Thour to 1 dey
Radionuclide
t week to 1 month
T day to 1 week
1 monthto I yeur
1 year to 70 years
Yield
Radionuclide
Yield
Rudionuclide
Yield
Radionuelide
559
519
458
454]
451
Mo... 8s.
Cel... 2]
Nb? 1.)
DR...
pit.
360
360
250]
241
937)
Lal__ re
Bato
~w--f
Pri@ __
Cettt__.
DH.
444
427
423
414
387
376
363
351)
314
294
250
233
222
206
164
163
161]
Zr"...
Tet?,
Bat®_..
Lave.
-|
Palo... -]
Pri®. 2...)
Y%_Srt._
Pmt.
Nd¥7___
Rho
[5_.
Celt,
Zr.
¥"__
¥e_.
Sri.
~
229
228
160
128
122
U1
Hid
9G
92
77
70
48
40
39
37
37
35
Nd¥7_
Zr%6___
Y%_.
Sree_.
Mom,
Rue.
Rhee,
132 |
.
Tet?___ wees
Obes, e weee
Cet4...
Pret.
Cela...
Pm'@..
337
293
284)
216
160
128
127
Nb... 2...)
Zr... 22)
Yo.
Sriv_.
Cem,
Ces...
Prt _.
586
483
374
311
284
271
271
Sr. 12... }
Ye
Cet? .
-.
Bat7_
Pm
Cems.
Pris,
480
430
406
406
215
214
214
96
93)
87
79
Lave. _
Baio __
Pm¥?.. _...
Nd...
150 Rhtes_
135 Zr%__
44 ya .
et
27
14
9
4
28
Rhis_
72
71
70
67
61
Rh 2.
Pris. oo...
31
7
126
37
34
2
Ru... 2.)
32
122
109
102
4h]
28
14}
12)
Vield
Rus _
Rnie__
Pri___
ym le
Ruts,
.
Sr
-|
-
¥8_.
Cit
a
Bat?__..
197
189
154
34
22
22
13
13
10
10
Radionuetide
Smit
Nb®.
Ruts,
Yield
44
31
27