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MICROCOPY RESOLUTION TEST CHART
NATIONAL BUREAU OF STANDARDS - 1963
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SM/76-12
SLP 2 2 1966
CFSTI PRICES377
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60807-3
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LEGAL NOTICE
This report was prepared as an account of Governmont sponsored work, Nettaer the United
States, nor the Commission, nor any person acting on bebail of the Commission:
A. Alakes any warranty or representation, expressed or implied, with respect to the accu-
racy, completeness, or usefulness of the information conlained in this report, or that the use
of any information, apparatus, method, or process disclosed in this report may not infringe
privately owned rights; or
B. Absumes any llabilities with respect to the use of, or for damages reswung from the
use of any information, apparatus, method, or process disclosed in this report.
As used in the above, "person acting on behalf of the Commission" includes any om-
ployce or contractor of the Commission, or employee of such contractor, to the oxtont that
Buch employee or contractor of the Commission, or employoe of such contractor preparos,
disseminates, or provides access lo, any information pursuant to his employment or contract
with the Cummission, or his employment with such contractor.

RELEASED FOZ ANNOUNCEMENT
IN NUCLEAP. SCIENCE ABSTRACTS
MULTILABORATORY INTERCOMPARISONS OF NEUTRON DOSIMETRY SYSTEMS*
J. A. Auxier
Health Physics Division, Oak Ridge National Laboratory
Oak Ridge, Tennessee
During the past ten years, several plants and laboratories in the
United States have adopted and installed nuclear accident dosimetry
systems. Because of the economic factor, the lack of adequate test
facilities, or, in some cases, the pressure of time limitations resulting
from the rash of accidents in 1958, most of these systems received only
cursory testing and evaluation prior to their acceptance. However, health
physicists now have more extensive radiation facilities at their disposal,
particularly at the Oak Ridge National Laboratory, and more comprehensive
and comparative studies of the accuracy and utility of the various systems
have been initiated.
In March of 1965, the first joint multilaboratory study was conducted
at the ORNL DOSAR Facility with seven laboratories and production plants
participating. Two exposures were made during which the Health Physics
Research Reactor (HPRR) [1] was used in the burst mode to simulate acciden-
tal nuclear excursions. On the first day, the HPRR was pulsed in a "low
scatter" geometry with the dosimeter systems set up along an arc of 3 m
radius. On the second day, the experiment was repeated with a 20-cm-thick
*Research sponsored by the U. S. Atomic Energy Commission under contract
with the Union Carbide Corporation.
graphite moderator between the reactor and the dosimeters. During the
first exposure, a live burro was also positioned along the arc to serve as
a "phantom" complete with a heterngeneous and circulating source of blood
were used for this purpose.
The participants met two days after the second exposure to tabulate
and compare results. After returning to their home installations and after
further analysis of their data, they submitted revised estimates of the
dose.
In the fall of 1965, a second study was made primarily with the same
participants. This was intended to test relative reproducibility with
time as well as any modification which had appeared desirable and feasible.
Future studies will include other installations and dosimeter systems and
other radiation sources as well. (e.g., a small accelerator).
Figure 1 shows the arrangement of the apparatus around the reactor
for the first exposure, and Table I shows the results of the first two
exposures. Rather than name the participating installations, they are
designated here by a letter only, except for the DOSAR Facility. A more
meaningful description is given in columns 2 and 3 of Table I, however,
by listing the primary dosimeter components for neutrons and gamma rays,
respectively. As most of the systems were calibrated for a fission spec-
trum of neutrons, good agreement might be expected. The initial and
revised estimates for the neutron and gamma-ray exposures are given in the
last two columns.
The results of the second exposure (i.e., with the graphite moderator
in place) are shown also in Table I. In this case, there is an apparent
increase in the variance of the reported results. Table II shows the
ranges and averages for the data; the range cf results for total fluence
and for two specific detectors is shown also. The results for the first
two sets of experiments are esse:tially identical. The measurements made
by the DOSAR Facility staff and repcaced in the table were made with
threshold detector units [2,3] and photoluminescent dosimeters. [4,5]
However, these systems were cross calibrated with other DOSAR standard
instruments, including proportional counters, spectroneters, etc., so that
the neutron and gamma-ray values should be accurate to within +5% and 18%,
respectively, for one standard deviation.
From these data and other auxiliary tests performed during the past
few years, several conclusions may be drawn. The systems based on modera-
tors with imbedded thermal detectors yield too high response in the low
energy range from a few eV to 300 keV. The enhancement is of the order of
3 to 5. luclear emulsions and diode detectors (passive type) generally
read low in this region; the emulsions show no neutron tracks for energies
greater than thermal and less than about 0.5 MeV, and the response of the
diodes decreases sharply below 250 to 300 keV. It seems reasonable that
installations using the thermal neutron detectors in moderators might add
either emulsions or diode detectors. If, in case of an accident, the two
detectors give significantly different responses, the first higher than
than a fission spectrum and that the two responses represent the extremes
of the dose range. An average in this case would be better than either,
and approximate limits of error would be established directly.
Recent developments in the use of heavy particle track detection in
solids with fission foil radiators permit extensive simplification and
broader application of threshold detectors; [6] this may result in more
widespread use of this versatile dosimeter system. Figure 2 shows a
detector unit with glass plates for track detectors. Fission fragment
tracks in glass rendered visible with a magnification of 100 by etching
in hydrofluoric acid are shown in Fig. 3.
REFERENCES
.
[41
[1] AUXIER, J. A. ,. Ilealth Phys. 11 (1965) 89.
[?] HURST, G. S. et al., Rev. Sci. Instr. 27 3 (1956) 153.
(3] REINHARDT, P. W., DAVIS, F. J., Health Phys. 1 (1958) 169.
BERSARD, C. H. et al., Health Phys. 4 (1961) 236.
[5] CHEKA, J. S., Health Phys. 10 (1964) 303.
[6] KERR, 'G. D., STRICKLER, T. D., The application of solid-state nuclear
track detectors to the Hurst threshold detector system, to be pub-
lished in Health Physics.
CAPTIONS
Fig. 1. General view of the apparatus used in the first intercomparison
experiment arranged for exposure to the HPRR.
Fig. 2. Exploded view of the fission foil holder, foils, and glass detec-
tors for the modified threshold detector system.
Fig. 3. Photomicrograph of pits in glass caused by fission fragment bon-
bardment and subsequent etching in hydrofluoric acid.
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experiment arranged for exposure to the HPRR

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1000 ,

Table 1
RELATIVE DOSE VALUES OBTAINED BY THE VARIOUS INVESTIGATORS
DURING THE FIRST INTERCOMPARISON STUDY
Chief
detector,
neutron
Burst B7!D, March 23, 1965
Fast Therma! Gamma
neutrons neutrons rays
(rads) (rads) (r)
Chief
detector,
gamma
Study
group
Burst B72D, March 24, 1965
Fast Thermal Gamma
neutrons neutrons rays
(rads) (rads) (r)
A
0.6
73
0.5
32
Foils in
moderator
TLD and
film
- 462
3378
193
188
33
129a
30a
--
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-
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. ܫܝ -
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-
-
-
-
-
-
-
-
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B.
0.16
79
0.15
44
Foils on
phantom
Glass and
film
468
337
132
120
-
-
-
-
-
-
-
-
-
-
-
-
--
DOSAR
TDU
Glass
58
81
0.30
22
320
300
3208
0.29a
D
TDU
56
79
24
Glass and
film
332
356
0.19a
S2
0.152
22a
21a
22a
E
52
23
Modified
TDU
Glass and
film
466
431
120
91
339a
333a
80 a
73a
F
Silicon
diode
330
75
800
TDU
346
3162
0.20
Glass and
film
52
Did not participate
·
"Revised two weeks after experiment.
-
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-
--..
Table II
RANGES AND AVERAGES OF DOSES AND FLUENCES REPORTED BY THE
VARIOUS INVESTIGATORS DURING THE FIRST INTERCOMPARISON STUDY
March 23
March 24
Range
Fast neutrons
Gammas
300 to 468 rads
52 to 79 r
75 to 193 rads
22 to 44 r.
-
Revised range
-
-
-
t
--
Fast neutrons
Gammas
--
316 to 339 rads
52 to 79 r
79 to 129 rads
22 to 44 r
--
-
*..
Average
.
Fast neutrons
Gammas
384 rads
62 r
111 rads
29 r
Revised average
Fast neutrons
Gammas
348 rads
60 r
96 rads
28 r
Neutron fluence (total)
Range
Revised range
(12.6 to 19) 1010
(12.6 to 19) 1010
(3.8 to 9)1010
(3.8 to 7.8)1010
In + Cd
Range
(0.02 to 0.47)1010
(0.02 to 0.48)1010
Cu
Range
4.7 x 1010a
(4.0 to 4.4)1010
Two identical values.
.
1
-
-
-
.
..
-
END
-
.
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C
1
...
..1
DATE FILMED
10/24 / 66







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