SWRilL-50.3r
-NOTICI-
rePrl w, prepared at an account of work
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pletcneu or uaefulnew of any Information, apparatui
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WHOLE-BODY COUNT OF TUNGSTEN-187
IN PUS PERSONNEL FOLLOWING THE
SCHOONER EVENT
by
John A. Eckert
Environmental Protection Agency
Western Environmental Research Laboratory
P. 0. Box 15027
Las Vegas, Nevada 89114
The SCHOONER Event, conducted at the Nevada Test Site, December 8, 1968,
released radioactive effluent into the environment. Whole-body counts
were performed on thirty-one Public Health Service personnel who partici-
pated in this cratering experiment with tungsten-187 appearing in the
resultant spectra as the only contaminant.
Repeated whole-body counts were performed during the week following exposure
to determine the magnitude of individual burdens. The maximum burden
measured, 25 uCi.correlates to an estimated dose to the large intestine of
approximately 1 rad. Absorbed dose calculations, based on physiological
parameters taken from the International Commission on Radiation Protection
Manual II, indicate a dose conversion factor of 32 mrad per iiCi tungsten-187
ingested. A whole-body scan performed eight hours after exposure confirmed
the presence of tungsten-187 in the GI tract of one individual and yielded
an upper limit calculation on the maximum possible absorbed dose to the lung
of 6 mrad/uCi 187W retained.
Spectra obtained on all subjects woro carefully analyzed to detect any
iodine-133 that could be masked by tho rolatively largo amounts of tungsten-
187. The attributable dose duo to iodine-133 in the person showing the
highest burden of tungsten-187 was estimated to bo loss than 20 mrad.
External exposure was determined from results obtained on thermoluminescent
dosimeters worn by all personnel participating.

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WHOLE-BODY COUNT OF TUNGSTEN-187
IN PUS PERSONNEL FOLLOWING THE
SCHOONER EVENT
by
John A. lickert
Environmental Protection Agency
Western Environmental Research Laboratory
P. 0. Box 15027
Las Vegas, Nevada 89114
Project SCHOONER was a nuclear cratering experiment conducted on
December 8, 1968, at the Nevada Test Site as part of the Plowshare
Program. The yield of the device was approximately 35 kilotons and it
produced a crater 63 meters oeep and 260 meters in diameter. In accord-
ance with a Memorandum of Understanding with the Atomic Energy Commission,
the U. S. Public Health Service (whose activities in this area have now
been taken over by the Environmental Protection Agency) conducted a pro-
gram for documenting the extent and location of radioactive debris leaving
the boundaries of the Nevada Test Site. This task was accomplished through
the use of a number of sampling networks including ground monitoring with
hand survey instruments, fixed position Thermoluminescent Dosimeter net-
works, air samplers, milk collection, some vogctation sampling, and the
whole-body counting of personnel known to huvc been in the path of the
debris.
Altogether 107 whole-body counts wore obtained from 39 individuals
involved in the SCHOONER EVENT. With the exception of cesium-137 and

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potassium-40, components of all background wholo-bodv counts, no isotopes
could be identified in any spectra except tungsten-187. A typical whole-
body counting spectrum can be seen in Figure 1. Thirtv-onc of the subjects
counted were U. S. Public Health Service personnel and eight subjects worked
for other government agencies. No activity could be detected in any indi-
vidual after December 16 (D+8), and all counting was terminated on
December 20, 1968.
Fourteen individuals were counted on the day of the release including
personnel flying in monitoring aircraft and several individuals occupying
ground positions in the path of the cloud on the highway immediately north
of the test site and approximately 55 miles from the point of detonation.
A ground monitor positioned on the highway had the highest me-asuied burden
observed during the first day of counting and was chosen to serve as a
"standard" against which other individuals would be compared. About 11 hours
after exposure of this subject, herein referred to as Subject A, a whole-
body scan was performed. The results of this scan are shown in Figure 2.
Activity was detected in the nasopharyngeal area, the GI tract, and the
bladder. Most of the activity was concentrated in the region of the large
intestine. These results are consistent with the inhalation and subsequent
ingestion of large insoluble particulates.
Subject A was counted repeatedly during the two-week period following
the event and his initial burden of tungsten-187 is estimated to have been
25 uCi tungstcn-187. The whcle-body counter used to perform the measurements
uses an 11 by 4 inch Nal (Tl) crystal positioned over a .6 meter arc bed.
This geometry was originally selected to minimize calibration errors with an
unknown source location in the subject. Scan information suggested that most
activity was in the lower GI region; therefore, calibration was performed In-
using a urine sample in a 400 ml container positioned approximately where the
lower C,I region would be with respect to the whole-body counter arc. To
insure consistency in results, the urine sample was cross-calibrated with
other systems at the laboratory used to count milk and air samples. A
tungstcn-187 standard purchased from Amersham of London was used to calibrate
these other systems.
2

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External contamination was evident on the skin, hair, and clothing
of subjects arriving at the facility. Decontamination was performed by
showering. In order to maintain the integrity of the ery sensitive count-
ing facility, extreme caution was exercised to insure that no subjects were
admitted to the whole-body counting area with external contamination. The
chamber background in the energy band corresponding to the tungsten-187
peak is also shown. Little change in background occurred during the two-
week counting period. Counting results on Subject A as well as counts on
the urine sample serving as a calibration source arc shown in Figure 3.
Counting on this subject continued until December 20 when no activity could
be detected. Figure 4 is a retention plot of Subject A. The plotted points
have been corrected for the physical half-life of the tungsten-187 (23.7 hours)
and represent the actual biological retention of the nuclide. The plot is
characterized by a rather sudden drop between the 51st and 75th hour after
exposure and an apparent long-lived component (160 hour half-life).
Estimates of the absorbed dose due to tungsten-187 were made considering
the GI tract, the lungs, and the maximum possible thyroid dose that could
have occurred from iodine-133 masked by the tungsten-187. The model used to
estimate the dose to the GI tract is discussed in the appendix and is derived
from physiological parameters taken from I.C.R.P. II. The critical part of
the GI tract based on these assumptions is the large intestine and the dose
conversion figure derived is 32 mrad per uCi ingested. Subject A obtained
an estimated cose of 1 rad to the lower large intestine based on this conver-
sion factor. The assumption that the large intestine can he considered as
the critical organ for tungsten-187 is supported by a paper in Health
Physics, Vol. 15 by Kaye, which reports on rat experiments.
There was a question at the time that the critical organ might actually
be the lung based on a lack of knowledge of particle size and the possible
retention of a small particulate in the lungs. A conservative model was
chosen to compute the maximum possible dose based on information gathered
in the scan taken 11 hours after the exposure of Subject A. The model is
explained and derived in the appendix. The maximum credible dose based on
this modjl is estimated to be 6 mrad/pCi tungsten-187 retained. This value
3

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compared to the 32 mrad/uCi dose to the lower C'.I region cleorly points to
the tcr as the critical organ.
fitcause of the relatively large organ dose that can be obtained from
the inhalation of small amounts of iodine isotopes, it was necessary to
make some estimate of the possible iodinc-133 that could have been masked
in the spectra by the presence of the tungsten-187. The theoretical
location of an iodinc-133 peak is shown on the spectrum illustrated in
Figure 1. The physical ha If-lite of the two nuclides arc quite similar;
tungsten-187, 23.7 hours and iodine-133, 20.8 hours; however, it was thought
that the much slower elimination of the iodine isotope from the thyroid
(biological half-life 138 days, l.C.ll.P. 2) might change the ratio of the
two isotopes in pairs of spectra taken on individuals where significant
elimination of the tungsten-187 was known to have taken place. The latter
of the pair of spectra was stripped from the former to try to enhance the
counts in the iodine-133 region. This technique was used on a number of
pairs of spectra but no iodine-133 peak was observed. Maximum values for
iodine-133 were finally estimated by assuming that should a peak be present
in a given spectrum the peak would be identifiable by visual inspection it
the counts in the iodinc-133 peak region exceeded the counts in the spectrum
by an amount e ua 1 to three standard deviations of tin- counting error;
a = 1/ N. Tlu maximum size iodine-133 peak would then lie just 3 r.. To fnwl
' x
the maximum possible dose due to iodine-133 the maximum possible burden
hidden in a given spectrum was extrapolated back to time of exposure and tlu
factor 1.39 mrud/n(!i was applied to the extrapolated result. Tnis converse",
factor is also derived in the appendix, .'laximum computed thyroid dose due
to possible iodine-133 inhalation was estimated to be 3!> mrad.
Counting results on all individuals are shown in ligure S. The plot
reveals considerable variation between individuals with respect to the
retention of the isotope. The graph not only demonstrates the difficulties
of constructing valid dose medels when dealing with the (11 tract but points
out a problem of even assigning lelativc doses when multiple counts arc
taken on individuals. Note in the figure tli.it initiallv Subject A's burden
exceeded that of Subject 1$ lr. a factor of 2.4, but on the tith day following
the event Subject H's burden exceeded Subject A's by a factor of 1.2.

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Relative burdens were actually assigned by considering the initial count*
as indicative of the isotope passing through the (il region. Four or more
counts were taken on three ii.dividuals, Subjects A, H, and C in the figure.
Retention graphs were plotted comparing the three subjects correcting the
data for the physical half-life of the isotope. One such graph, shown in
Figure 6, is based on 1001 being the amount in the subjects on the counts
taken on December 9. The plots represent the biological retention of the
isotope after this date. Note that no apparent similarity in the retention
pattern exists except that the retention decreased as a function of time.
Six radiation monitors who were whole-body counted to determine
tungsten-187 burdens were also wearing Thermoluminescent Dosimeters. The
Thermoluminescent Dosimeter used was an Elite Model TI.-12 which is enclosed
in a glass envelope and has a low energy cutoff of SO kev. The response of
the device at energies higher than 50 kev is essentially independent of the
energy of the incident gamma ray. Figure 7 is a map showing the location
of the monitors, their Thermoluminescent Dosimeter readings, and their
respective estimated CI tract doses. Figure 8 shows a comparison of
Thermoluminescent Dosimeter readings versus estimated doses to the large
intestine due to the inhalation of tungsten-187. A linear least squares
fit of the data suggests that the ratio of Thermoluminescent Dosimeter
reading to estimated internal dose was on the order of 0.41. The remaining
U. S. Public Health Service personnel were either in unusual exposure
situations; for example, crcwing aircraft, were not stationary during cloud
passage or were wearing some sort of protective respiratory device and a
comparison of TLD readings versus tungsten-187 burdens is of little value.
5

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REFERENCES
(!) Report of ICRP Committee II on Pcrnissiblc Dose for Internal
Radiation (19S9).
(2)	Report of ICRP Committee IV on Evaluation of Radiation Doses
to Body Tissues from Internal Contamination Due to Occupational
Exposure (1968).
(3)	IIINI:, r,.j., BROWNELL, C,.L., Radiation Dosimetry (1958).
(4)	KAYE, S.V., Distribution and Retention of Orally Administered
Radlotungsten in the lint, Health Physics, 5 (I9<>8) 599-417.
(5)	ECKERT, .J.A., 'tonitoring of Several Individuals Exposed to Mixed
Fission Product I'.ascs at NTS, Health Ph>sics, 1 (1964) 1 123-1127.
(6)	Environmental Protection Agency, Firal Report of Off-Site
SurveiIlancc for Project Schooner, December 8, 1968 (1971 in press).

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TYPICAL WHOLE BODY COUNT SPECTRUM
G
theoretical 1-133 spectrum
e
o
o


B
0.5
energy mev
Figure 1
2
page 7

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Figure 2 WHOLE BODY SCAN H+U HOURS
counts per minute over region indicated
page 8

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date
Figure 3
page 9

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RETENTION GRAPH - SUBJECT
-a	-	Hill iM
50	100	150
hours after exposure
Figure 4
page 10

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WHOLE BODY COUNTING
RESULTS
chamber background
10 11
date
Figure 5
12 13
14
page IT

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0 subject B
p subject C
RETENTION GRAPH
(corrected for W-187 hall life )V * tv

50	100	150
hour* after exposure
Figure 6
pof* 12
2C
\

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igure 7 T.L.D. READING AND DOSE ESTIMATE
TO LLI VS. LOCATION OF PHS MONITORS

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T.LD. RESULTS VS.
" ESTIMATED GJ. DOSE
10'	10
T.LD. result mR
Figure 8
a
page 14

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APPENDIX
THEORETICAL ABSORBED DOSE TO LOWER LARCE INTESTINE FROM ,47W
Proa I.C.R.P. 2, use Equation 14.
R  (q f-) 3.7 x 10* x 24 x 3600 x 7 x 1.6 x 10"6E dt rcas/week
2 x 100 m x dt/t
Divide by 7 to obtain dose in rad/day
Multiply by 1000 to obtain mrad
Considor q fj as the input to Die lower large intestine in uCi.
From I.C.R.P. 2, Table II the tine elapsed from ingestion until isotope
reaches the lower large intestine is 13/24 days. Tiie physical T, o
,8,W is 23.9 hours. Therefore, the amount of 187K reaching the '
lower large intestine per yCi ingested is .687.
E  .36 McV effective energy
a  Mass organ
 150 grams
t  Time ior passage
> 18/24 days (I.C.R.P. 2)
Inserting these values;
R' (mrad)  uCi ingested x 31.7
IS

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APPENDIX
107
THEORETICAL ABSORBED DOSE DUE TO 0 W IN LUNGS
F
Dose (in mrad) = Q x 51.2 x  (from I.C.R.P. 10, Equation 1).
m
m = Mass lungs
= 1000 grains (I.C.R.P. 2)
E = Absorbed energy/disintegration
= .44 MeV
Q  Time integral of contamination nCi - days
Calculation is based on scan information of Subject A. It is assumed
tliat the count rate over lungs initially would equal the count rate
observed over the lower GI region in the scan (*8 tvrs) and that tne
lung turnover function was a simple exponential. Furtucr it is
assumed that the intake function was a constant 25 iiCi/lir between 1100
and 1300 hours with the fraction retained equaling .5 (I.C.R.P. 2).
1100	_ 1300
Time -*
Activity in Lungs
2 0 15
l-'rom scan
Background  80 counts
Lower GI = 939 counts
= 85'J net counts
Lung
	157 counts
	77 net counts
77 = 859 exp (- .693  8/T^)
T^  2..18 hrs
X  .3
Q  /J 0 (t) dt (I.C.R.P. 10, Equation 2)
187
lecting physical t(j of W
from 1100 - 1300 hrs q (t)  1 I: - oxp (- A11I
T 
from 1300 hrs - 00 q (t) = q (1300) exp (- Xtl

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APTENDIX
from 1100 - 1300 hrs Q  42 pCl  hrs
q (1300)  38 uCl
from 1300 hrs  Q  125 uCi hrs
Q  167 pCi - hrs
 7 pCi - days
Dose  7 x 51.2 x .44 t 1000  158 mrad
 6.3 rarad/nCi retained
17

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APPENDIX
THEORETICAL ABSORBED DOSE TO THYROID DUE TO INHALATION OF 133l
Dose (in mrad)  Q x SI.2 * - (from l.C.R.P. 10, Houation 1).
!D
n  Mass thyroid
 20 grams
L  Absorbed cnercv/di* integral ion
 . S4 rieV
Q  Time integral of contnmin.ition nCi  days
Calculation based on amount of 153| in	thyroid extrapolated back tc tin.
of exposure.
Q  / iexp (- v t) 1	1 - exp	(- > . t)|)dt
^ o ' eff ' uptake
- 1 -	1	
X eff X eff * ' uptake
*	er  . 7J9(> (I .C.R.P. 2)
C t f
Assume S hours uptake
*	, - ..VU
uptake
Q  1.OOH
Do'C  1.00S x SI. 2 * .S : 20  1 . M mrad/nCi l,V*l
18

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