SWRHL-93r
A COMPARISON OF FILM BADGES AND THERMOLUMINESCENT
DOSIMETERS USED FOR ENVIRONMENTAL MONITORING
by
Charles K. Fitzsimmons, William Horn, and William L. Klein
Environmental Surveillance
Western Environmental Research Laboratory
ENVIRONMENTAL PROTECTION AGENCY
Published May 1972
This study performed under a Memorandum of
Understanding (No. SF 54 373)
for the Nevada Operations Office
U. S. ATOMIC ENERGY COMMISSION
-------
"This report was prepared as an account of work sponsored by the United
States Government. Neither the United States nor the United States Atomic
Lnergy Commission, nor any of their employees, nor any of their contractors,
subcontractors, or their employees, makes any warranty, express or implied,
or assumes any legal liability or responsibility for the accuracy, or
process disclosed, or represents that its use would not infringe privately-
owned rights."
Available from the National Technical Information Service
U. S. Department of Commerce '
Springfield, VA 22151
Price: paper copy $3.00; Microfiche $.95.
(JbO
-------
SWRHL-93r
A COMPARISON OF FILM BADGES AND THERMOLUMINESCENT
DOSIMETERS USED FOR ENVIRONMENTAL MONITORING
by
Charles K. Fitzsimmons, William Horn, and William L. Klein
Environmental Surveillance
Western Environmental Research Laboratory*
ENVIRONMENTAL PROTECTION AGENCY
Published May 1972
This study performed under a Memorandum of
Understanding (No. SF 54 373)
for the Nevada Operations Office
U. S. ATOMIC ENERGY COMMISSION
*Formerly the Southwestern Radiological Health Laboratory, U. S.
Department of Health, Education, and Welfare, Public Health Service,
Environmental Health Service, Environmental Control Administration,
Bureau of Radiological Health
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ABSTRACT
Data obtained from two concurrent dosimetry networks operated by
the Western Environmental Research Laboratory in Nevada, one
utilizing film badges and the other thermoluminescent dosimeters
(TLD's) are compared. Gamma exposures from a few mR to approx-
imately 1R due to both natural background and fission products
in the environment are more easily and accurately measured by the
TLD system. Where the minimum detectable exposure for film is
about 45 mR, the TLD sensitivity is on the order of 1 mR (which
allows measurement of monthly background exposures). The insensi-
tivity of TLD's to environmental heating, humidity, light damage,
and pressure makes them ideal for use in the extreme conditions
encountered in the desert. Heat damage to the film was seasonal
with the greatest losses occurring in the summer. During July,
1967, 71% of the film badges issued were heat or light damaged,
while no loss of TLD data occurred. No background information
was obtained from film data during 1967, but the geographical
variations in background exposure rates were clearly disclosed
by the TLD's.
-------
TABLE OF CONTENTS
ABSTRACT i
LIST OF TABLES ill
LIST OF FIGURES iv
INTRODUCTION 1
Film Badge Network 2
TLD Network 3
COMPARISON OF FIELD DATA 7
Data from the Routine Monitoring Network 7
Data from Monitoring a Nuclear Waste Disposal Site 10
Data from a Plowshare Experiment 15
DISCUSSION 26
CONCLUSIONS 29
REFERENCES 30
DISTRIBUTION
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LIST OF TABLES
Table Page
1 Summary of dosimeters issued to routine stations in 1967. 8
2 Paired average TLD - FB monthly exposures from Nuclear
Engineering Company site. 12
3 Paired TLD - FB data from Arc 1, Buggy I. 20
4 Paired TLD - FB data from Arc 4, Buggy I. 24
-------
LIST OF FIGURES
Figure Page
1 Gamma energy response of thermoluminescent CaF^rMn. 6
2 Percent return of film badge and TLD data during
1966 and 1967. 9
3 Background exposure rates at selected locations around
the Nevada Test Site as determined by TLD's. 11
4 Correlation of film and TLD response from Nuclear
Engineering Company data. 14
5 Cloud profile, Arc 1, Buggy I, first pickup. 16
6 Cloud profile, Arc 1, Buggy I, second pickup. 17
7 Correlation of film and TLD response from Arc 1, Buggy I. 19
8 Correlation of film and TLD response from Arc 1, Buggy I
lowest 13 data pairs. 21
9 Cloud profile, Arc 4, Buggy I. 23
10 Correlation of film and TLD response from Arc 4, Buggy I. 25
iv
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INTRODUCTION
In accordance with Memorandum of Understanding, SF 54 373, the
Western Environmental Research Laboratory (WERL) provides an
off-site radiological safety program for the Atomic Energy Com-
mission in support of nuclear tests conducted on the Nevada
Test Site (NTS) complex.
As one portion of the off-site radiological safety program, the
Dosimetry Unit of the WERL has a primary mission to document off-
site gamma radiation exposures above environmental background
resulting from specific nuclear tests.
Since inception of the program in 1954, integrating dosimeter
readings have been used to supplement off-site exposure data.
Film badges were the dosimeters of choice. However, because
interest in the field of radiological health has shifted during
recent years to the measurement of smaller exposures, the in-
herent properties of the film badge dosimeter severely limited
expansion of the program into this area. The sensitivity, ac-
curacy, and reliability of the film badge were found to be in-
adequate for the gamma radiation levels of interest.
During this same period, considerable research on thermolumin-
escent dosimeters (TLD's) was being done by a number of inves-
tigators. The properties of the TLD as described in the liter-
ature seemed more suitable for the needs of the WERL. In 1965,
after considerable field testing, a TLD system was incorporated
into the film badge dosimetry network. As a result, over two
years of side-by-side data have been accumulated from approxi-
mately eighty field locations.
-------
This report presents a comparison and discussion of the film badge
and TLD data.
Film badge Network
Before 1961, film badges were issued to off-site residents and
placed at strategic locations for specific nuclear tests. The
film packet used was DuPont type 556, containing a two-component
packet, emulsion No. 508, with a claimed detection range from
30 mR to 5R, and emulsion No. 834, with a detection range from
3R to 10R. In 1961, 28 permanent stations were established
with a monthly dosimeter exchange. By 1963, the number of per-
manent stations had grown to 66 in addition to a monthly dosi-
meter exchange with 130 off-site residents. The present pro-
gram involves 100 permanent off-site stations and 119 off-site
residents.
Although the DuPont 556 film packet was the most suitable field
dosimeter available at the time, serious problems were encoun-
tered. A high percentage of the film badges were damaged by
heat, light, and moisture. In 1963, an alternative to the
DuPont 556 film packet was investigated. Since off-site radia-
tion monitoring involved exposures less than 5R, it was felt
that a single component low-range film packet would be adequate.
As a result, a new film badge holder was designed incorporating
DuPont type 545 film with a detection range from 30 mR to ap-
proximately 4R. Although this reduced the initial film badge
cost by 50% and increased the sensitivity of the dosimeter some-
what, the new film packet was as susceptible to heat, light, and
moisture damage as its predecessor.
-------
During this same period, interest in the field of radiological
health had shifted to the measurement of smaller exposures. At
this point, the inherent limitations of the film badge became a
major obstacle to the growing needs and obligations of the Dosim-
etry Unit. In 1965, several non-film dosimeters were investi-
gated and evaluated.
TLD Network
After investigating various thermoluminescent and glass dosi-
meters, the Edgerton, Germeshausen, and Grier, Inc., (EG&G)
Thermoluminescent Dosimetry System was field tested. The EG&G
system utilized the TL-12 thermoluminescent dosimeter and the
TL-2B dosimeter reader. The detection medium of the dosimeter
consists of a layer of CaF2:Mn bonded to a helical heater ele-
ment that is encapsulated in a gas-filled glass envelope. The
detector is housed in an aluminum-tin-lead shield designed to
compensate for the detector over-response in the low energy
region of the gamma ray spectrum and to protect the detection
from light exposure. The dosimeter reader accepts the TLD in a
light-tight chamber, heats it with a regulated current and con-
verts the emitted light energy into an electrical signal for
display on the built-in strip chart recorder.
Preliminary field investigation involved the use of ten TLD's
for each of two NTS events: Sulky, a Plowshare experiment, and
the Transient Nuclear Test (TNT) of a Kiwi Reactor. During
each event, two TLD's were retained in Las Vegas as controls and
eight were placed in strategic locations or carried by EPA moni-
toring personnel. Although the field dosimeters yielded slightly
higher readings than the controls, evaluation on a larger scale
was advisable. Consequently, EG&G furnished 55 dosimeters for
-------
monitoring of Project Palanquin in April 1965. During each eval-
uation, ten dosimeters were retained as controls. Each of the
remaining 45 dosimeters was packaged in a polyethylene envelope
with one DuPont type 555 film packet and one DuPont type 556
film packet. The type 556 film had been pre-exposed to 100 mR60Co
radiation in an attempt to gain greater sensitivity to low expo-
sures. The dosimetry packages were placed on stakes within the
expected trajectory and carried in monitoring aircraft and by
field personnel.
After a ten-day exposure in the field, the TLD's were taken to
EG&G in Santa Barbara, California, for reading. The film badges
were sent to Mercury, Nevada, for processing. The results ob-
tained from Santa Barbara indicated that the manufacturer's
claims concerning the minimum dose resolution of 5 mR and a co-
efficient of variation of 10% were, in fact, conservative. In
addition, it was found that the pre-exposed film performed very
poorly and this technique was abandoned. The TLD system held
promise to fulfill the growing need for greater sensitivity and
accuracy in measuring environmental gamma exposure.
An EG&G TLD system was obtained and put into operation during
August 1965. The first four months of operation indicated that
before the full potential of the system would be realized, a
number of objectives had to be met. These objectives were to
(1) perfect a system of reader calibration, (2) establish a
correction factor for each dosimeter, (3) determine the internal
background due to 't°K activity within the dosimeter, (4) ascertain
the significance of fading over extended periods of time, and (5)
determine the precision of the system. The results of studies
-------
and solutions to problems in these areas, as well as the develop-
ment and growth of the TLD network, are discussed in another
report. '
The bulk of the data used for comparison in this report was col-
lected during 1966 and 1967 when 80 TLD stations were in operation.
The data represent exposures to the gamma radiation of fission
products in the range from 5 mR to approximately 1R. The energy
response of any dosimeter is a function of the shielding em-
ployed as well as the detection medium. The energy response of
the TL-12 is shown in Figure 1.
-------
1O
CTi
o
U
o
o
0)
in
c
O
a
in
0)
a>
o:
l»| unshielded
(ft shielded
I I
.01
O.1
Effective Energy
MCV
1O
Figure 1. Gamma energy response of thermoluminescent
-------
COMPARISON OF FIELD DATA
Data from the Routine Monitoring Network
Data from the routine stations are used primarily to establish back-
ground exposure rates, even though the network owes its existence to
the need for measurement of possible biologically significant expo-
sures due to specific nuclear tests. Background, in this sense,
refers to the exposure from all ionizing radiation in the environ-
ment which can not be attributed to any specific man-made source.
Thus, it is possible in some cases that background includes the
exposure from a residual trace of long-lived fission products as
well as from the naturally-occurring radionuclides and cosmic radia-
tion. The observed variation in background levels from place to
place is a function of the intensity of all three contributors, man-
made, terrestrial, and cosmic.
The film badge has proven incapable of providing this background
information. Out of 6454 film badges placed at the off-site stations
during 1967, only 199 or 3.0 percent had a reported value greater
than zero. Table 1 presents a summary of dosimeters issued, those
damaged or lost, and those having a reading greater than zero. Of
2461 TLD's issued in 1967, only 10 failed to produce usable data.
If film badges are left in the field long enough to obtain a reading
over the 30 to 50 mR threshold, the chance of heat or light damage
becomes a near certainty. Film badges left in the field for two
months which do not become unreadable because of severe heat damage
often read 40 to 50 mR, about 100 percent greater than the expected
exposure. Figure 2 shows the seasonal variation in the precent of
dosimeters which had usable data for the years 1966 and 1967.
-------
Table 1. Summary of dosimeters issued to routine stations in 1967
Reporting
Period
No. of Dosim-
eters used
Uo. Lost or
Damaged
Percent lost
or damaged
No. reporting
values greater
than zero
Percent
greater
than zero
THERMOLUMINESCENT DOSIMETERS
Jan.
Feb.
Mar.
Apr.
May
June
July
Aug.
Sept.
Nov.*
Dec.
Totals
209
210
207
216
177
204
222
248
246
261
261
2461
0
0
0
0
6
0
0
1
3
0
0
10
0
0
0
0
3.3
0
0
0.5
1.2
0
0
0.4
209
210
207
216
171
204
222
247
243
261
261
2451
100
100
100
100
96.6
100
100
99.5
98.8
100
100
99.6
Jan.
Feb.
iMar.
Apr.
May
June
July
Aug.
Sept
Nov.*
Gee.
Totals
588
482
592
574
491
600
580
632
628
630
657
6454
FILM
18
12
132
64
146
400
413
177
60
15
12
1449
BADGES
3.0
2.4
22.2
11.2
29.7
66.6
71.2
28.0
9.5
2.3
1.8
22.5
17
18
31
50
20
24
0
18
21
31
27
199
2.8
3.7
5.2
8.7
4.0
4.0
0
2.8
3.3
4.9
4.1
3.0
* Reporting periods were longer than one month on the average, and only eleven reports
were made in 1967. The gap was made up by skipping the October report.
-------
1966
1967
<
Q
|JAN|FEB|MAR|APR|MAY|JUN
JULJAUG
SEP |OCT|NOV|DEC
JAN] FEB
MAR
APRJMAY|JUN|jULlAUG|SEP|NOV|DEC| |
Q
Z
LJJ
o
o
00
5
Z
Cki
Z)
LU
Figure 2. Percent return of film badge and TLD data during 1966 and 1967.
-------
Little use is made of the routine film badge data since the TLD's
perform so well. TLU background exposure rates for a few selected
locations are presented in Figure 3.
The basic purpose of any monitoring network is to detect exposures
above natural background. However, small off-site exposures due to
nuclear testing are seldom detected even by the TLD's at routine
stations because the signal-to-noise ratio is unfavorable. Typical
monthly backgrounds range from 10 to 20 mR. Variation in the monthly
background exposure at a given location can be as great as ±50 per-
cent. Thus, net exposures less than about 10 mR which are still of
interest may be missed. Greater sensitivity is obtained by placing
special dosimeters in the field for specific events and using the
background values derived from the routine data to calculate net
exposures. In order to accumulate background data, the dosimeters
used must be sensitive to the low background exposure of one month's
time.
Data from iionitoring a uuclear Waste Disposal Site
Four routine stations in the monitoring network are located on the
fence surrounding the Nuclear Engineering Company's radioactive waste
disposal site near Beatty, Nevada. Each station has five film badges
and three TLD's. The stations were established on request of the
uevada State Health Department. Subsequently, the stations have pro-
vided side-by-side data which have been used to compare film badge
and TLD performance. Exposures range from about 40 mR to nearly 700 mR.
Paired average values of TLD and film badge responses for one year at
the disposal site are ranked by TLD response in Table 2. The data
were collected from January 4, 1967, to January 11, 1968. Each value
represents the exposure in mR for approximately one month. The great
monthly variations are the result of burials and other movement of
radioactivity within the fenced area. A linear regression was performed
10
-------
mR/DAY
AT:
DATE
»
LAS VEGAS
NEVADA
WARM SPRINGS
RANCH
NEVADA
ST. GEORGE
UTAH
PIOCHE
NEVADA
ALAMO
NEVADA
HANCOCK SUMMIT
NEVADA
GARRISON
UTAH
DUCKWATER
NEVADA
WARM SPRINGS
NEVADA
CLARK STATION
NEVADA
AUSTIN
NEVADA
TONOPAH
NEVADA
GROOM LAKE
NEVADA
LATHROP WELLS
NEVADA
SHOSHONE
CALIFORNIA
MAMMOTH LAKE
CALIFORNIA
BARSTOW
CALIFORNIA
_
0
*"
o_
0_
10-
0
m
tf>_
1966
OCT
10 20 C
" i
I
fj
FT
NOV
DEC
5=
L :::-.- a
CHANGE OF STATION A
LOCATION DEC 1966' 9
m
i
r~>
i
''.. '':\':'^-;.
--!
1967
IAN
~fe^
.-
i
FEB
|_
|
_J
MAR
i
_j
-^^-
T?
1
,...|
APR
MAY
JUN
IUL
-L.
I
B
1
m
l_
~
1
J... .
f
^ro
1
1
jjfiiis:'',:.
1
^-T
J
r
i
wJ
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AUG
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i
l':.h'"-''i
:.;! . ..
i
f
F
j
i
L_
r
c^
r1
!"":'
SEP
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1
Figure 3. Background exposure rates at selected locations
around the Nevada Test Site as determined by TLD's.
11
-------
Table 2. Paired average TLD - FB monthly exposures from Nuclear
Engineering Company Site.
NORTH
TLD (mR)
37
38
43
50
52
60
62
62
63
93
EAST
TLD (mR)
61
67
75
98
101
102
126
147
150
FENCE
FB (mR)
79
44
23
34
81
49
48
55
58
98
FENCE
FB (mR)
70
34
96
106
90
110
95
131
182
SOUTH
TLD (mR)
46
64
64
71
72
98
187
269
364
537
FENCE
FB (mR)
39
40
96
113
65
104
183
267
367
671
WEST FENCE
TLD (mR)
48
62
63
72
79
81
121
185
297
551
679
FB (mR)
48
95
47
52
no
71
123
141
321
505
663
12
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on the data and yielded y = -1.01 + 1.03 x, which is an excellent
agreement between the two dosimeters (see Figure 4). The slope of
1.03 has a coefficient of variation of only 3.22 percent and a
correlation coefficient of 0.98.
The lowest reported film badge reading in this group of data was
23 mR. Thirty-four readings were greater than 45 mR, while only
six were less. The excellent correlation is attributable to the
ideal exposure range, 40 to 700 mR, for the film. What is not
shown by these figures is that all zero values or unreadable
(damaged) film badges were deleted from Table 2. Frequency of
heat damage followed the same seasonal trend as it did for the
other badges in the network (Figure 2). For example, during July
1967, 19 of the 20 badges issued were unreadable. Of the 220
film badges issued, 27 percent were heat damaged, and 1 percent
indicated zero. No data were missing from the 132 TLD's issued
during the same period.
Another statistical test was made on the Nuclear Engineering data.
Individual readings rather than averages were used so that a better
estimate of the error term would be made. The hypothesis that the
mean film badge response is equal to the mean TLD response for a
given exposure was tested using a two factorial design. Calcu-
lations were made by an IBM 1130 computer. The two factors were:
(A) monthly effects; and (B) type of dosimeter (film badge or TLD).
As expected there was a very large monthly effect. There was also
a significant difference at the 95 percent confidence level between
film badge and TLD means; however, the regression analysis done
previously suggests that the difference was probably small. The
interaction term (A x B) was also significant indicating a possible
seasonal effect on the film response. The validity of this inter-
pretation is supported by the fact that heat damage to the film is
seasonal and, therefore, sensitivity might be assumed to be seasonal
13
-------
900
Y = 1.O + 1.O3X
o
I
I
100 200
300 400
mR (TLD)
500 600 700 800
Figure 4. Correlation of Film and TLD Response from Nuclear Engineering
Company Data.
14
-------
also. Furthermore, studies have shown ' ' that environmental temper-
ature, humidity, and pressure have no detectable effect on TLD re-
sponse. It is likely, then, that the interaction term reflects a
greater degree of variation in film response than in TLD response.
Data from a Plowshare Experiment
EPA monitoring activities for Project Buggy I, a Plowshare nuclear
cratering experiment conducted on March 12, 1968, included six
arcs of thermoluminescent dosimeters placed across the expected
cloud trajectory. The dosimeters yielded a series of exposure pro-
files across the cloud path at 8, 10, 35, 51, 82, and 170 miles
downwind from ground zero. The data also defined the line of maxi-
mum exposure, the approximate cloud width with distance, and the
decrease of exposure as a function of distance.
On two arcs, Arc 1 and Arc 4, film badges were placed alongside the
TLD's. Arcs 1 and 4 were approximately eight miles and fifty-one
miles from ground zero (GZ), respectively.
Two TLD's and two film badges were placed on each stake of Arc 1.
One of each was collected at H + 3 hours and the data plotted as
"first pickup" in Figure 5. The remaining TLD's and film badges
were collected on D + 7 days. These data are plotted as "second
pickup" in Figure 6. The difference in low level sensitivity is
shown plainly in these two plots. Above 80 mR film and TLD re-
sponses are comparable, but there is increasing disaareement between
the film badge and TLD data as the exposure level decreases. Be-
low 45 mR there is no reported film response at all. Under these
' A two-year study by Mr. William Horn, WERL, of TLD measurements
of backgrounds at Las Vegas, Tonopah» Fallen, and Ely, Nevada,
indicated no effect to the TLD's from environmental conditions.
TLD's were placed inside USWB instrument shelters at all four
locations.
15
-------
10
FILM
TLD
0
92 90 88 86 84 82 80 78 76 74 72 70 68 66 64 62 60
STAKE NUMBER
Figure 5. Cloud Profile, Arc I, Buggy I, First Pickup.
16
-------
10
IU
§10
(f)
O
Q.
X
UJ
10
oo
FILM
TLD
92 N N K 14 12 N 78 76 74 72 71 SI 66 64 62 60
STAKE NUMBER
Figure 6. Cloud Profile, Arc I, Buggy I, Second Pickup.
17
-------
experimental conditions, 45 niR appears to be the minimum detect-
able exposure for the film (DuPont 556 packet, the same as that
used at the Nevada Test Site for personnel monitoring).
The film and TLD data were paired for a statistical comparison of
response to common exposures. Of the 34 film badges issued, only
19 provided positive data. Consequently, only the 19 film badge-
TLD data pairs shown in Table 3 were used in the analysis.
The first linear regression analysis, performed on all 19 data
pairs, yielded the relationship y = 21.36 + 1.086x, where y repre-
sents the film response and x the TLD response. The data are
plotted in Figure 7. The slope of the regression line was equal
to 1.086 with a coefficient of variation of 1.64% and a correlation
coefficient of 0.99.
As can be seen from Table 3, the film showed little sensitivity to
small changes in exposures below 55 mR. A second linear regression
analysis was performed on the lowest 13 data pairs. The result of
the analysis (Figure 8), yielded the relation y = 32.9 + 0.770x.
The slope of the regression line was equal to 0.770 with a coefficient
of variation of 5.67% and a correlation coefficient of 0.98.
18
-------
1400
1200
1000
5
I
\^
g
E
800
600
400
200
Y = 21.36 + 1.086X
I
200
400
600 800
mR (TLD)
1000
x
1200
Figure 7. Correlation of Film and TLD Response from Arc I, Buggy I.
19
-------
Table 3. Paired TLD - FB data from Arc 1, Buggy 1
TLD (mR)
14.8
15.4
16.0
17.0
17.2
20.4
21.4
21.7
29.8
31.1
44.5
75.6
92.8
135.5
162.1
252.9
313.8
734.3
1025.4
FB (mR)
45
45
45
45
45
45
55
55
55
55
65
85
no
150
195
290
390
760
1175
20
-------
120
110
10
5
_i
IL
40
CD
Y = 32.9 + 0.77OX
20
20
40
mR (TLD)
10
100
Figure 8. Correlation of Film and TLD Response from Arc I, Buggy I,
Lowest 13 Data Pairs.
21
-------
One DuPont type 545 film badge, the same type as is used in the
dosimetry network, was placed on each stake along Arc 4, 54 miles
from ground zero. Exposure profiles, as detected by both film
badges and TLD's, are plotted in Figure 9. The conspicuous lack
of film badge data points results from the exposure levels being
near or below the minimum detectable limit of the film. Table 4
lists the paired values for which positive film data were available
A linear regression on the data of Table 4 yielded the relation,
y = 10.54 + 0.586x, which is plotted in Figure 10. The slope of
the regression line was equal to 0.586 with a coefficient of vari-
ation of 4.37% and a correlation coefficient of 0.94.
The data in Figures 7, 8, and 10, and their respective analyses
are presented in the order of decreasing exposure levels. In
general, as the level of exposure decreases, the correlation co-
efficient of film and TLD response decreases. The slope also
decreases from unity, indicating that the range of exposure is
near the minimum detectable limit of the film, i.e., there is a
flattening of the curve at low exposures. An increasing degree
of variation accompanies film response as exposure levels decrease,
further indicating that the lower limit is being approached. The
above data would indicate that the lower limits of the 556 and 545
film are approximately 45 mR and 30 mR, respectively.
22
-------
10
LLI
o:
D
(0
0
Q.
X
111
10
I
_L
10
20 30 40
MILES ALONG ARC
50
60
Figure 9. Cloud Profile, Arc 4, Buggy I,
23
-------
Table 4. Paired TLD - FB data from Arc 4, Buggy 1
TLD (mR) FB (mR)
29.0 30
37.0 30
53.4 45
54.7 40
65.8 45
69.4 50
72.8 60
74.0 50
81.6 60
24
-------
N
2
\L
sa
50
40
30
20
10
Y = 10.5 + 0.586X
I I I I
II 20
30 40
mR (TLD)
50 60 70 00
Figure 10. Correlation of Film and TLD Response from Arc 4, Buggy I.
25
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DISCUSSION
It has been shown that the film badge as used by WERL in the off-
site environment is incapable of providing background information.
During 1967, only 3% of the 6454 badges issued had a reported value
greater than zero. In addition, the data which were available
varied from the expected exposures sufficiently that their validity
was in doubt.
Data from both the Nuclear Engineering Disposal Site and the Plow-
share project indicated that the minimum detectable limit for the
film badge is approximately 45 mR.
The Nuclear Engineering Disposal Site film badge data which escaped
heat damage showed an excellent agreement with the TLD data. The
high correlation is attributable to the ideal exposure range, 40-700-mR,
for the film.
The same situation was seen in greater detail in the investigation
of Plowshare data. Analyses of data resulting from three different
levels of exposure indicated that as exposure levels decreased, the
correlation coefficient of film and TLD response decreased. This is
an indication that at lower exposures, TLD and film results are less
likely to agree. It was evident that the lower exposures were ap-
proaching the minimum detectable limit of the film because the slope
of the linear regressions decreased from unity with decreasing ex-
posures.
A definite relationship between ambient temperatures and film damage
has been shown in both the routine network data and Nuclear Engineering
Disposal Site data. During 1967, 22% of the 6454 film badges issued
to routine stations were lost or damaged. The monthly damage percentage
varied seasonally from a low of 1.8% in December to a high of 71.2t in
26
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July. Frequency of heat damage to film badges located at the Nuclear
Engineering Disposal Site followed the same seasonal trend seen in the
routine data. In 1967, 27% of the badges were heat damaged.
A statistical test of the Nuclear Engineering data indicated a possible
seasonal effect on film response, in addition to the seasonal fluctua-
tion of heat damage. This, and other research, tend to indicate that
the precision of film response is less than that of the TLD.
The TLD is more suitable as an environmental monitor than the film
badge, and is quite capable of providing background information. In
addition, it is unaffected by environmental heating both in terms of
damage and response. Of 2461 TLD's issued to routine stations, only
10, or 0.4%, failed to produce usable data. No data were missing
from the 132 TLD's issued to the Nuclear Engineering Disposal Site
during this same year.
In addition to the results of this investigation, there are several
pieces of recent supporting research. According to Johnson and
to)
Attixv , most erroneous film data, including readings which occur
when no exposure exists, can be related to heat and humidity damage.
They compared a quartz fiber dosimeter and two types of TLD's with
film badges worn by personnel. The first three dosimeters agreed
within ten percent but the film badges were often off by a factor
of two or three.
From a processing standpoint, film is subject to more variables than
the TLD. The accuracy and reproducibility of reported film badge
(3)
exposures by commercial dosimetry services often are quite poor.v '
The best accuracy appeared to be -50 to +200 percent. The film
processing service at Mercury, Nevada, used by WERL is believed to
be considerably better than this (±20% above 100 mR). This claim
is supported by the good correlation of our film and TLD data in
favorable exposure ranges.
27
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tn)
Kathrerr ' has shown that considerable fogging of dosimetry film
occurs above 50°C, a condition often attained in the field situations
under discussion. This high frequency of heat and light damage was
one of the major reasons for investigating and acquiring a TLD system
at WERL.
There have been several studies by other investigators in recent years,
comparing the performance of a variety of dosimeters. A few are
mentioned here to put WERL efforts in prespective. Becker* ' discusses
the relative merits of photographic, glass, and thermoluminescent
dosimeters. Cusimano and Cipperley* ' describe the personnel dosi-
metry program at Idaho Falls, using LiF9 - Teflon dosimeters. Hall
(7)
and LaRoccav ' report the use of TLD's for environmental monitoring
at the Savannah River Plant, South Carolina. In each case, TLD's
were favored over film because they had better precision, better
accuracy, higher sensitivity, and a greater dynamic range.
28
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CONCLUSIONS
The review of TLD and film badge data from the routine dosimetry
stations, the Nuclear Engineering Disposal Site, and a Plowshare
experiment, leads to conclusions which favor TLD's. The TLD is
more sensitive to the exposures of interest than the film badge.
Because of this, it has been possible to obtain average values
for background exposure rates at the various dosimetry stations.
The high ambient temperatures encountered during the summer months
cause an unacceptable amount of damage to film badges used as
environmental monitors. In addition to heat damage, there is
evidence that film sensitivity is temperature dependent, which may
cause a seasonal effect on film badge results. TLD's at the same
locations sustain no apparent effects from environmental heating.
Statistical treatment of dosimetry data shows the TLD to be more
precise than the film. Typical TLD reproducibility is well within
±5 percent.
29
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REFERENCES
1 Fitzsimmons, C. K. and William Horn. SWRHL-58r, Environmental
Monitoring with Thermoluminescent Dosimeters, Second Printing,
Feb. 1970, Southwestern Radiological Health Lab., Las Vegas,
Nevada.
2 Johnson, T. L. and F. H. Attix. Pilot Comparison of Two Thermo-
luminescent Dosimetry Systems with Film Badges in Routine
Personnel Monitoring, Naval Research Lab., Test and Evalu-
ation Report 69, 1967, p. 34, Washington, D. C.
3 Suntharalingham, N. and John R. Cameron. A Comparison of TLD
and Film for Personnel Dosimetry. Health Physics 12:1595-
1599. 1966.
4 Kathren, R. L. Thermal Fogging of Personnel Monitoring Film.
Health Physics 12:61-63. 1966.
5 Becker, K. Photographic, Glass or Thermoluminescence Dosimetry?
Health Physics 12:955-964. 1966.
6 Cusimano, John P. and Foster V. Cipperley. Personnel Dosimetry
Using Thermoluminescent Lithium Fluoride-Teflon Dosimeters.
Health Physics 14:339-344. 1968
7 Hall, R. M. and J. P. LaRocca. Thermoluminescent Dosimeters
for Environmental Monitoring. Health Physics 12:851-852.
1966.
30
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DISTRIBUTION
1-15 WERL, Las Vegas, Nevada
16 Robert E. Miller, Manager, NVOO/AEC, Las Vegas, Nevada
17 Robert H. Thalgott, NVOO/AEC, Las Vegas, Nevada
18 Henry G. Vermillion, NVOO/AEC, Las Vegas, Nevada
19 Chief, NOB/DNA, NVOO/AEC, Las Vegas, Nevada
20 Robert R. Loux, NVOO/AEC, Las Vegas, Nevada
21 Donald W. Hendricks, NVOO/AEC, Las Vegas, Nevada
22 Technical Library, NVOO/AEC, Las Vegas, Nevada
23 Mail & Records, NVOO/AEC, Las Vegas, Nevada
24 Martin B. Biles, DOS, USAEC, Washington, D.C.
25 Director, DMA, USAEC, Washington, D.C.
26 John S. Kelley, DPNE, USAEC, Washington, D.C.
27 Harold F. Mueller, NOAA/ARL, AEC/NVOO, Las Vegas, Nevada
28 Gilbert J. Ferber, ARL/NOAA, Silver Spring, Maryland
29 Stanley M. Greenfield, Assistant Administrator for Research & Monitoring,
EPA, Washington, D.C.
30 Acting Deputy Assistant Administrator for Radiation Programs,
EPA, Rockville, Maryland
31 Paul C. Tompkins, Act. Dir., Div. of Criteria & Standards, Office of
Radiation Program, EPA, Rockville, Maryland
32 Ernest D. Harward, Acting Director, Division of Technology Assessment,
Office of Radiation Program, EPA, Rockville, Maryland
33 Bernd Kahn, Chief, Radiochemistry & Nuclear Engineering, NERC, EPA,
Cincinnati, Ohio
34 - 35 Charles L. Weaver, Acting Director, Division of Surveillance & Inspection,
Office of Radiation Programs, EPA, Rockville, Maryland
36 Gordon Everett, Director, Office of Technical Analysis, EPA,
Washington, D.C.
37 Regional Administrator, EPA, Region IX, San Francisco, California
38 Eastern Environmental Radiation Laboratory, EPA, Montgomery, Alabama
39 Acting Director, Twinbrook Research Laboratory, EPA, Rockville, Maryland
40 Library, EPA, Washington, D. C.
41 William C. King, LLL, Mercury, Nevada
42 James E. Carothers, LLL, Liver-more, California
43 Roger E. Batzel, LLL, Livermore, California
44 William E. Ogle, LASL, Los Alamos, New Mexico
45 Harry S. Jordan, LASL, Los Alamos, New Mexico
46 Arden E. Bicker, REECo, Mercury, Nevada
47 Clinton S. Maupin, REECo, Mercury, Nevada
-------
Distribution (continued)
48 Charles F. Bild, Sandia Laboratories, Albuquerque, New Mexico
49 Robert H. Wilson, University of Rochester, Rochester, New York
50 Richard S. Davidson, Battelle Memorial Institute, Columbus, Ohio
51 Frank E. Abbott, USAEC, Golden, Colorado
52 John M. Ward, President, Desert Research Institute, University of
Nevada, Reno
53 - 54 Technical Information Center, Oak Ridge, Tennessee (for
public availability)
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