Calculations: gamma source, measurements 57B-66

Calculations: gamma source, measurements 67-76A

Plug End

Blue Dot

I +o -- Hl

Red Dot

(dz)?= (di +8.9)?+ (5.7)? Ea
Ai/Aa= (de)?/(di)? fii]
where A,=R/hr at d,
and = A.=R/hr at d,
rem/hr at d,=1.44* A, [iii]
* See Fig. 9.
Fravre 20, Diagram of radiation geometry (not to

scale) and calculation of dose rates (rem/hr) at
the Geiger tubes for measurements 57B-66. A, is
the dose rate in R/hr at distance d, (cm) from the
Cs gamma source according to calibration infor-
mation obtained at Kirtland. 4d, is the distance
from the source to the can. 4, is the distance from
the source to the Geiger tubes.

18

Moderator End csi8?

Blue Dot

30.4. cm

~------0--------!

Red Dot
Geiger tubes

f
1

1

1

' x

' 5.76m
'

'

1

(dz)? (di +30.4)?-+ (5.7)? [i]
Ai/Aa= (de)?/ (di)? Gi]
where A,=R/hr at d,
and A,=R/hr at d,
rem/hr at d,=1.44* A, [iii]
* See Fig. 9.
Fieure 21. Diagram of radiation geometry (not to

scale) and calculation of dose rates (rem/hr) at
the Geiger tubes for measurements 67-76A, A, is
the dose rate in R/hr at distance d, (em) from the
Cs*" gamma source according to calibration infor-
mation obtained at Kirtland. 4d, is the distance
from the source to the surface of the moderator.
d, is the distance from the source to the Geiger
tubes.


Calculations: neutron source, measurements |-8, Il, 12

Blue Dot, Opposite Meter Side, Meter Side

Center of neutron detector

d:=di +5 Gi]
Au/Ae= (de)?/(d)? Gi]
where A,=rem/hr at d,
and A,=rem/hr at d.
rem/hr at d2=(A1) (di)?/(d2)* (ii)

Figure 12, Diagram of radiation geometry (not to
seale) and calculation of dose rates (rem/hr) at
neutron detector for measurements 1-8, 11, 12. A,
is the dose rate in rem/hr at a distance d, (em)
from the Pu-Be neutron source according to cali-
bration information obtained at Los Alamos. 4d, is
the distance from the source holder to the center
of the neutron detector. d, is the distance from
the source (point source assumed) to the center of
the detector.

12

Calculations: neutron source, measurement 9

Moderator End

we

Scm

do

12.0 em

stron detector
(under blue dot)

[ ieeneeaieeeeneiete)

d,=d,+12.0+5 fi]
Aj/Aa= (do)?/(di)? [ii]
where A,=rem/hr at d,
and A,=rem/hr at d,
rem/hr at d2= (Ax) (di)*/(de)? [iii]
Figure 18. Diagram of radiation geometry (not to

scale) and calculation of dose rate (rem/hr) at
neutron detector for measurement 9. A, is the dose
rate in rem/hr at a distance d, (em) from the
Pu-Be neutron source according to calibration in-
formation obtained at Los Alamos. 4, is the distance
from the source holder to the center of the neutron
detector. d, is the distance from the source (point
souree assumed) to the center of the detector.




Jacket te provide insulation

for recorder

tibia,

Fieure 2, Concorde instrument on rackmount ready for installation in RB-57F.

Fievre 3. HARIS package and Concorde instrument in upper pressurized compartment of RB-S7F.

3



Tani 4.—Radiation Measurements Made with the Concorde Instrument on Flights from Eielson Air Force Base in

Alaska
Date 10/22/69 10/29/69 11/3/69 11/17/69 11/18/69 11/19/69 11/21/69 11/21/69 11/21/69
Maximum In-

Flight Chart

Reading... ...- 3.2 3.4 3.3 3.2 3.2 3.1 3.2 3.2 3.2
Dose Rate,

Millirem/hr*._ 0.7-0.9 1.0 0.9 0.7-0.9 0.7-0.9 0.5-0.7 0.7-0.9 0.7-0.9 0.7-0.9
Altitude, Kilofeet 60 60 60 60 60 60 60 60 60
Latitude, °N_..- 65 70 67 71 70 70 70 68
“Background”

Chart readingt 1.7 1.6 1.6 1.5 1.5 1.5 15 1.7 1.6
Internal Source

chart readingt 15.2 15.3 15,2 15.0 15.2 15.1 15.3 15.2

*Estimated from the maximum in-flight chart reading by use of the extrapolated portion of the calibration curve
in Fig. 15.

In the aircraft on the ground. This data was collected as an additional instrument check but not used to correct
the readings at altitude.

Constancy check with Sr®°,

indicate a galactic radiation dose-rate of 0.7-0.9 VI. Conclusions.
millirem/hr at 60,000 ft and 65°-71°N geomag-
netic latitude. This compares reasonably well
with 1.1 millirem/hr+40%, the reported value

Results of the calibrations performed at Los
Alamos Scientific Laboratory and at Kirtland
from recent earlier measurements made with the Air Force Base compare favorably with those

HARIS package at 60,000 ft and high geomag- carried out by the British. Galactic radiation
netic latitude.” It should be realized that the measurements made with the Concorde instru-

Concorde instrument was designed to measure ment at SST altitude and northern latitudes are
solar cosmic radiation at levels much higher than reasonably consistent with those obtained with

obtained from galactic radiation. the HARIS package.
REFERENCES
1. Radiobiological aspects of the supersonic transport. tory, Kirtland AFB, New Mexico, Interim report on
A report of the IORP Task Group on the Biological the high altitude radiation environment study. June
Effects of High-Energy Radiations. Health Physics 1969.
12: 208-226, 1966. 5. Benbow, T. G, A solar flare monitor for Concorde.
2, Langham, W. H., [ed.], Radiobiological factors in In, Proceedings of the 5th international aerospace
manned space flight. National Academy of Sciences, instrumentation symposium, Cranefield, Beds. Eng-
National Research Council, Publ. 1487. Washington, land, March 25-28, 1968.
De. 1967, p24. ae 6, Federal Aviation Administration. Advisory Commit-
8. United Kingdom, Air Registration Board, TSS Stand- tee for Radiation Biology Aspects of the Supersonic
ards, Tssue 4, Part 7-1, paragraph 2, Cosmle radia- ‘Pransport. Interim report on the radiation biology
tion, June 8, 1969, aspects of the supersonic transport. Washington,
4. Air Force Systems Command, Biophysics Division, D.C., June 23, 1970.

Bioastronautics Branch, Air Force Weapons Labora-

19 38316





Opposite

er Dot

Meter Side ° cs !3?
midway between
blue and red dots
Measurements 34-46 4
— Red Dot
ial [pe
Meter Side . 7cs'3?
midway between
blue and red dots
Measurements 47-57A °
Npecorder
Cs!37
Plug End o fe Le
Measurements 57B-66
Moderator End os!37
4
. ° <—O

Measurements 67-76A

16

Ficure 18. Position of gamma source relative to Concorde instrument for measurements 34-76A,


‘Taste 1.—Continued

Measurement dy R/hr Rem/hr at Meter Chart. Average
No. (em)* at dt Detector? Reading Reading “Background”’§
Red Dot**, Source-On Plug-Intt
458.7 0.0010 0.00142 3.5 4.2 7
324.4 0.0020 0.00284 4.5
264.8 0.0030 0.00424 5.2 4.9 1.7
205.1 0.0050 0.00704 6.2 5.9 LT
173.4 0.0070 0.00982 6.8 6.6 1.7
162.2 0.0080 0.01121 7.3 6.7 1.8
145.0 0.0100 0.01397 7.6 7.3 1.8
187.3 0.0060 0.00844 6.6 6.3 1.8
229.4 0.0040 0.00565 5.8 5.4 1.7
290.1 0.0025 0.00354 5.0 4.5 1.5
374.6 0.0015 0.00213 4.3 4.0 5
418.8 0.0012 0.00170 4,2 3.8 15
483.6 0.0009 0.00128 3.7 3.5 1.6
548.3 0.0007 0.00099 3.5 3.4 17
102.5 0.0200 0.02760 9.3 8.9 17
32.4 0.2000 0, 25257 14,2 13.9 1.9

*The number of digits does not reflect experimental precision.
+ Distance (dj) from center of Cs" source to Concorde instrument and corresponding dose rate (R/hr) on 9 June 1969.

tNo correction was made for “background”.

§Concorde chart-reading with source shutter closed.

¥*The side of the Concorde instrument that faced the Cs!” source.
tt Configuration of the Cs!” source. ‘“‘Source-on plug-in” is the low dose-rate configuration and means that the Cs"?
source capsule, which is in a lead-filled steel container, was positioned in front of the container aperture with the aperture
plug in place to attenuate the radiation. “Source-off plug-out” is the high dose-rate configuration and means that the
Cs" capsule was positioned away from the aperture and the plug was out.
#Repetition of measurement indicated in parenthesis. The repeat measurement was not unbiased (the observer
knew the previous reading), and was not included in the graph.

Red Dot

Measurements 1-33.

Red Dot

Measurements 768-9!

Blue Dot

nes Dot

<—S

U

cs !37

<—s. midwoy between

blue and red dots

cg'37
opposite red dot

Figure 8. Position of gamma source relative to Concorde instrument for measure-
ments 1-33 and 76B-91.

8


Moderator end

Plug end

Meter side

Fiaure 6. Configuration of Concorde instrument for calibrations.

2 91S oN WwHass
"Psi /urmae 344k
‘aa4nn03 Wa¥ wouinaN
“ONVIONS — AB¥YNS
7 SOINOWLDITS ANDLWID mOz,

Blue dot

_

OU.

Red dot side

csi E
fa Ua

BS

Ficure 7. Configuration of Concorde instrument for calibrations.

Red dot side of instrument facing source. Ref-
erence scale in inches.

5



bonttid

me

Fiecre 4. HARIS package and Concorde instrument in upper pressurized compartment of RB-57F,

View from
above the compartment.
10.06
8
®
°
go
ok Pe a
© °
# 0)
ato
‘Opposite Meter Side (Neutron) in 9°
Meter Side (Neuteon) x on
Nederator End (Neutron Be
ok loderotor End (Neutron ©
Plug End (Neutron) * Be
Ba a ©
= * °
Fe s
Fs +|
© Gammo (Cs!'97, Kirtland)
oo! te oe
Bo 2 Gamma (Co®® Aldermaston)
* 4 0° Dose rotes and corresponding Concorde meter-readings.
“Red dot side” of instrument facing the radiation
s 4 8 source excep! ahere ndicoted otherwive © Neutron Pu289-Be,0.019-0.072 rem
go u?38-Be,0.121-1.1 cem
20
ook Los Alamos
& Neutron (Am?4!-Be, Aldermaston)
Digitol-reoding derived dore-rares (computed from
digitol-reading increments ond elapsed times) ond tr Gomme (Ra226 Oklahoma)
corresponding meter reodings, “Opposite meter side”
of instrament facing the rodiation source
0.0001 fi 1 1 f 1 f 1 1 L 1 1 fl L L 1 1
3 * 5 6 7 ° ) a
METER READING

Fievre 5.

Concorde instrument meter-readings with corresponding dose rates for gamma and neutron radiation,
and dose rates computed from digital readings with corresponding meter readings.

4


with the Cs'** source in its low dose-rate con-
figuration (source-on plug-in). With the Cs***
source in its source-on plug-in (low dose-rate)
configuration, the two measurements (0.0276 and
0.253 rem/hr) made within the range of dose
rates used to calculate the straight line fell on or
very close to the line. The eight measurements
made between 0.0035 and 0.0139 rem/hr, below
the range of the high dose-rate measurements
from which the line was calculated, fell a little
above but parallel to the line. The five measure-
ments made at dose rates between 0.0010 (the
lowest dose-rate measured) and 0.0021 rem/hr
were below and not parallel to the line and the
chart readings were higher than expected from
either the high dose-rate data or the other low
dose-rate data. The deviation from linearity
was not associated with the position of the Con-
corde instrument in the Cs**" calibration-range
room (nearness to a wall, ete.). The distance
between the Concorde instrument and the Cs**
source, for all measurements made with the source
in its source-on plug-in (low dose-rate) config-
uration, was within the range of distances for
measurements made with the Cs* source in its
source-off plug-out (high dose-rate) configura-
tion (Table 1, measurements 1-33 and 76B-91).
Assuming that dose rates on the Kirtland Cs'*?
range are accurate and include background radia-
tion (as designed), then nonlinearity in the
Concorde instrument calibration curve (Fig. 15)
at low dose-rates can be attributed fo a charac-
teristic of the instrument.

Curves (Fig. 16) derived from Concorde-
instrument chart and meter readings and cor-
responding Cs'*’ gamma dose-rates were almost.
identical (data from Table 1, measurements 1-33
and 76B-91; calculations in Fig. 8-10).

Figure 17 shows calibration curves from meas-
urements made with different sides of the Con-
corde instrument facing the Cs? gamma source.
When the moderator end of the instrument was
facing the Cs" source, approximately nine times
the dose rate was required to give the same chart.
reading obtained with any other side of the in-
strument facing the source (data from Table 1,
calculations in Fig. 8-10 and 18-21). Thus, the
Geiger counters show a directional response ap-
parently because of the moderator.

The Concorde instrument responded normally
after exposure to 10 and 30 rem/hr of gamma

1%

radiation (Table 1 measurements 56 and 57A).
Measurements made before and after these off-
scale exposures fell on the same curve (Fig. 15).

VY. Radiation Measurements Made At 60,000
Ft With the Concorde Instrument.

Table 4 shows measurements made on RB-57F
flights in October and November from Eielson
Air Force Base, Alaska. The maximum in-flight
dose rate was estimated from the maximum
chart-reading by use of the extrapolated portion
of the calibration curve in Fig. 15. The data

Calculations: gamma source, measurements 34-57A

Opposite Meter Side and Meter Side

(dz) ?= (di +10.7)?-+ (9.2)* a]
(ds)?=(de)?+ (5.7)? {ii]
Aa/As= (ds)*/ (di)? [iii]
where A,=R/hr at d,
and A;=R/hr at d,
rem/hr at d,=1.44* As [iv]
* See Fig. 9.
Figure 19. Diagram of radiation geometry (not to

seale) and calculation of dose rates (rem/hr) at
the Geiger tubes for measurements 34-57A. A, is
the dose rate in R/hr at distance d, (cm) from the
Cs" gamma source according to calibration infor-
mation obtained at Kirtland, d, is the distance
from the source to the surface of the moderator.
d, is the distance from the source to the Geiger
tubes.



Tasie 1.—Continued

Measurement a R/br Rem/hr at Meter Chart Average
No. (em)t at dt Detector? Reading Reading  “Background”§
31#(22).. 314.9 0.0500 0.06966 11.3 id L8
324(21) 266.1 0.0700 0.09603 12,1 12.0 7
33#(19).. 234.7 0.0900 0. 12396 12.7 12.5 L7
Opposite Meter Side**, Source-Off Plug-Out*t
222.6 0. 1000 0.13081 12.6 12.5 7
157.4 0.2000 0.25147 141 13.9 1.9
90.9 0.6000 0.68385 16.2 16.1 2.3
70.4 1.0000 1.06619 17.2 17.0 2.8
49.7 2.0000 1.89071 18.3 18.1 2.6
157.4 0.2000 0.25147 14.1 14.0 2.3
222.6 0, 1000 0. 13081 12.7 12.5 21
266.1 0.0700 0.09301 12.0 11.8 2.0
314.9 0.0500 0.06727 11.2 10.9 1.9
406.5 0.0300 0.04098 10.0 9.6 1.7
497.9 0.0200 0.027588 9.3 8.9 7
642.8 0.0120 0.016714 8.0 17 1.8
704.2 0.0100 0.01396 7.6 1.3 1.9
Meter Side**, Source-Off Plug-Outtt
704.2 0.0100 0.01396 7 7.8 7
497.9 0.0200 0.02758 9.1 9.2 2.0
406.5 0.0300 0.04098 10.0 10.0 1.9
314.9 0.0500 0.06727 11.2 WL 1.9
266.1 0.0700 0.09301 11.9 11.9 1.9
222.6 0.1000 0.13081 12.8 12.8 1.9
157.4 0.2000 0.25147 141 14.1 2.3
90.9 0.6000 0.68385 16.3 16.2 2.8
49.7 2.0000 1.89071 18.5 18.2 2.9
Meter Side**, Source-On Plug-Outtt
185.0 10.00 Off scale
106.8 30.00 Off scale
49.7 2.0000 2.0533 18.2 18.0 3.0
70.4 1.0000 1.12915 17.0 16.8 2.5
90.9 0.6000 0.71445 16.0 15.9 2.3
187.4 0.2000 0.25770 13.9 13.8 1.9
222.6 0.1000 0, 13806 12.4 12.8 1.8
266.1 0.0700 0.09434 11.8 11.6 17
314.9 0.0500 0.06807 10.8 10.8 17
406.5 0.0300 0.04136 9.7 9.5 1.8
497.9 0.0200 0,02779 9.0 8.7 1.8
704.2 0.0100 0.01404 7.5 72 1.8
Moderator End**, Source-Off Plug-Out'*
704.2 0.0100 0.01323 4.0 3.8 7
497.9 0.0200 0.02557 4.7
406.5 0.0300 0.03739 5.8 5.0 1.9
314.9 0.0500 0.05986 6.2 5.7 1.6
266.1 0.0700 0.08116 7.0 6.5 1.9
292.6 0.1000 0.11142 7.6 71 1.9
157.4 0. 2000 0. 20214 9.2 8.5 1.6
90.9 0, 6000 0, 48415 11.2 10.6 2.0
70.4 1.0000 0.70028 11.9 11.5 2.0
49.7 2.0000 1.10470 12.9 12.6 2.0

See footnotes at end of Table 1.



TECHNICAL REPORT STANDARD TITLE PAGE

T. Report No. 2. Government Accession No. 3. Recipient's Catalog No.

FAAwAMe71=- AC - 4

‘4. Title and Subtitle 5. Repost Date }
CALIBRATION OF THE CONCORDE RADIATION DETECTION va LIZ.
INSTRUMENT AND MEASUREMENTS AT SST ALTITUDE 6. ye" ©: Yoni zation Code

7. Author») 8. Performing Organization Report No.

Wallace Friedberg, Ph.D.
John M. Nelson, B.B.A.

9. Performing Organization Nome and Address 10. Work Unit No.

FAA Civil Aaxvomedical Institute
P, O, Box 25082
Oklahoma City, Oklahoma 73125

Ti. Contact or Grant No.

13. Type of Report and Period Covered

12. Sponsoring Agency Name and Address

Office of Aviation Medicine
Yederal Aviation Administration OAM Repeat

800 Independence Avenue, S.W. 14." Sponsoring Agency Code”
Washington, D. C, 20590

15. Supplementary Notes

This work was performed under Task No, AM-B-71-PHB-18,

16. Abstroct

Performance tests were carried out on a solar cosmic radiation detection
instrument developed for the Concorde SST, The instrument calibration curve
(log dose=rate vs instrument reading) was reasonably linear from 0.004 to 1
rem/hr for both gamma radiation and fast neutrons, Nonlinearity in the
calibration curve was observed at dose rates below 0.003 rem/hr. The instrument
responded normally after exposure to 30 rem/hr of gamma radiation. The charged
particle detectors showed a directional response apparently because of the
neutron moderator, The neutron detector did not show a directional response.
When accumulated dose ~- which is shown on the digital display of the

instrument -~ was used to compute the dose rate, the dose rate was overestimated
by about 169% at 0.0013 rem/hr and 50% at 0.1 rem/hr. Measurements made with
the Concorde instrument at 60,000 ft. and high geomagnetic latitudes indicated
a galactic cosmic radiation dose rate of 0,7 - 0.9 millirem/hr.

17. Key Words 18, Distribution Statement
Cosmic radiation Availability is unlimited. Document may
Supersonic transport be released to the National Technical
Radiation detection instrument Information Service, Springfield,
Concorde SST Virginia 22151, for sale to the public.

19. Security Classif. (of this report) 0, Security Classif. (of this page) Fi. No. of Pages | 22. Price

. ly
Unclassified. Unclassified $3,00

Form DOT F 1700.7 (8-69)



‘Tapp 2-—Concorde Instrument Meter- and Chart-Readings and Corresponding Neutron Radiation Dose Rates*

Measurement dy Rem/hr Rem/hr at Meter Chart Average
No. (em)t at dit Detector? Reading Reading = “Background’’§
Blue Dot**, Pu®-Bett
1 300 0.002 0.00193 4.5 4.3 2.0
2 200 0.005 0.00475 5.6 5.4 2.3
3 100 0.019 0.01723 8.2 8.0 21
4 50 0.072 0.05950 11.0 10.8 1.9
Blue Dot**, Put*-Bett
100 0, 133 0, 12069 12.4 12.2 2.3
50 0. 532 0. 4396 15.6 15.3 2.6
30 1,500 1.1019 17.5 V1 1.8
Blue Dot**, Pu%*-Bett
8#(8)---------------- 100 0.019 0.01723 8.2 8.0 1.9
Moderator End**, Pu*-Bett
[re 100 0.019 0.01387 7.6 1.8 1.9
Plug End**, Pu**-Bett
100 0.019 0.01085 7.0 6.7 QA
Opposite Meter Side**, Pu%?-Bett
5. nnn 100 0.019 0.01723 8.3 8.0 21
Meter Side**, Pu%*-Bett
12.2222 e eee 100 0.019 0.01723 7.9 7.6 21

* The number of digits does not reflect experimental precision.
+Distance (d;) from Pu-Be neutron source housing to center of neutron detector and corresponding dose-rate (rem/hr)

on 11 June 1969.

?No correction was made for “background”.
§Chart reading with source out of room.

##The side of the Concorde instrument that faced the neutron source.

tt The neutron source.

#Repetition of measurement indicated in parenthesis. The repeat measurement was not unbiased (the observer
knew the previous reading), and was not included in the graph.

10


Calculations: gamma source, measurements {- 33

Red Dot

(dz)?= (dy +2.2+2.9)? + (9.2)? til

Au/Aa= (de)?/(di)? [ii]
where A,=R/hr at d.
and A,=R/hr at d,

Ae= (Ax) (di)?/(de)* [iii]
rem/hr at d2=(0.96)* (1.5) (Ay) =144 A, [iv]

* rads/R ratio for Os“ for muscle.
+rem/rad ratio used by Aldermaston group for gamma
radiation.

Frourr 9. Diagram of radiation geometry (not to
scale) and calculation of dose rates (rem/hr) at
Geiger tubes for measurements 1-33. A, is the dose
rate in R/hr at distance a, (cm) from the Cs'TM
gamma source according to calibration information
obtained at Kirtland. d, is the distance from the
source to the surface of the moderator. d, is the
distance from the source to the Geiger tubes.

Calculations: gamma source, measurements 76B-91

Red Dot

Blue Dot

H
i
!

d,=d,+2.2 i)

Ai/As= (d2)?/(di)? [ii]
where A,=R/hr at d,
and A,=R/hr at d,

As= (Ax) (di)?*/ (de)? [iii]
vem/hr at d,=1.44* A, [iv]
* See Fig. 9.

Ficure 10. Diagram of radiation geometry (not to
scale) and calculation of dose rates (rem/hr) at
Geiger tubes for measurements 76B-91. A, is the
dose rate in R/hr at distance d, (cm) from the
Cs" gamma source according to calibration infor-
mation obtained at Kirtland. d, is the distance
from the source to the can. d, is the distance from
the source to the Geiger tubes.



The upper pressure-compartment in the RB-
57EF, where the Concorde instrument was to be
located, is extremely cold at SST altitudes;
therefore, to ensure proper operation of the
Rustrak recorder, a 3000 ohm resistor was in-
stalled to supply extra heat and a jacket was
provided for insulation (Fig. 2).

IV. Calibration of the Instrument With
Cs.887

Concorde instrument meter-readings and cor-
responding dose rates for gamma and neutron
radiation are shown in Fig. 5. The data desig-
nated “Aldermaston” were replotted from cali-
bration .curves that came with the instrument.
These calibrations were performed on or about
30 December 1968 at the Atomic Weapons Re-
search Establishment in Aldermaston, Reading,

England. “Kirtland” denotes measurements
made at the Air Force Weapons Laboratory,
Kirtland Air Force Base, New Mexico, on 9-10
June 1969 and “Los Alamos” indicates measure-
ments made 11 June 1969 at the Los Alamos
Scientific Laboratory, New Mexico.

Figure 6 shows the configuration of the Con-
corde instrument used for the measurements at
Kirtland and Los Alamos. In order for the
“red dot side” (Fig. 7) to face the radiation
source, the instrument was placed on its side
with the meter and Rustrak recorder down. For
the Kirtland data in Fig. 5 see Table 1 measure-
ments 1-33 and 76B-91. The calculations are
described in Fig. 8-10. The Los Alamos data
used in Fig. 5 are given in Table 2 and the
calculations are described in Fig. 11-14.

Tass 1.—Concorde Instrument Meter- and Chart-Readings and Corresponding Gamma Radiation Dose Rates*

Measurement ay R/br Rem/br at Meter Chart Average
No. (em)t at dyt Detector? Reading Reading ‘‘Background”§
Red Dot**, Source-Off Plug-Outtt
222.6 0.1000 0. 13740 12.8 12.8 1.7
157.4 0. 2000 0. 26934 14.2 14.2 1.5
128.5 0.3000 0.39777 15.2 15.0 1.9
111.3 0. 4000 0. 52338 15.8 15.6 1.9
99.5 0. 5000 0, 64656 16.1 16.0 2.0
90.9 0. 6000 0. 76759 16.6 16.2 2.8
84.1 0.7000 0. 88669 16.9 16.6 2.3
78.7 0.8000 1.00400 ADA 16.9 2.3
74.2 0. 9000 1.11966 17.4 171 2.3
70.4 1.0000 1.23376 17.6 17.4 2.5
64.2 1.2000 1.45766 17.9 17.7 2.6
57.5 1, 5000 1.78385 18.4 18.1 2.9
49.7 2.0000 2.30493 18.8 18.4 3.2
44.5 2. 5000 2, 80202 19.1 18.8 3.3
70.4 1.0000 1.23376 17.6 17.2 2.5
90.9 0.6000 0.76759 16.7 16.3 24
157.4 0.2000 0, 26934 14.3 14.1 1.9
222.6 0.1000 0. 13740 12.8 12.7 1.7
234.7 0.0900 0, 12396 12.7 12.5 1.7
248.9 0.0800 0, 11047 12.4 12.3 1.9
266.1 0.0700 0, 09693 12.1 11.9 7
314.9 0.0500 0.06966 11.2 11.2 1.7
406.5 0,.0300 0.04211 10.1 9.9 1.7
497.9 0.0200 0.02820 9.3 9.0 1.7
642.8 0.0120 0.01700 8.2 8.1 1.6
704.2 0.0100 0.01419 8.0 7.6 1.5
704.2 0.0100 0.01419 8.0 7.8 1.5
642.8 0.0120 0.01700 8.1 7.9 1.5
497.9 0.0200 0.02820 9.4 9.1 1.6
406.5 0.0300 0.04211 10.2 9.9 1.7

See footnotes at end of Table 1.




Moderator

Geiger tubes

Fievre 1.

tests performed in Aldermaston on production
models identical to the unit lent to the FAA
indicated that the seals were inadequate at the
junction of the polyethylene moderator and the
can enclosing the electronic components and also
at the bolt heads securing the top plate. Mr. T.
G. Benbow of the Atomic Weapons Research
Establishment provided us with results of the
tests in Aldermaston and a list of production
modifications. Accordingly we made the follow-
ing modifications in the instrument in our charge:
(1) a groove was machined in the polyethylene
moderator and the flat gasket between the mod-
erator and the can was replaced with a ¥% inch
‘o’ ring (FSN 5330-551-3963) and (2) the
metal lock-washers used with the top-plate bolts
were replaced with shakeproof paper-base phe-
nolic washers.

Concorde instrument partially disassembled.

A miniature one-channel Rustrak chart re-
corder (Model 228, 0-1 ma), which allows con-
tinuous data collection for 9 hr, was coupled to
the ratemeter. The frequency of the print stroke
is 20/min and the gear train moves the chart
paper 15 inch/hr. The vertical coordinate of
the chart paper is divided linearly.

The Concorde instrument and recorder were
attached to a modified Barrymount, type 10020-10
(Fig. 2-4). The mount has 18-40 lb shock ab-
sorbers inboard and 10-20 Ib shock absorbers
outboard. The entire package including the
shock-mount rack weighs 39 lb. The power re-
quired, about 15 w, is obtained from a 115 v 400
cycle outlet in the aircraft. A mating plug and
power cable were provided and the system was
fused to meet FAA standards. The instrument.
package passed the required pull test of nine
times its weight.


Calculations: neutron source, measurement 10

1
'
Center of neutron detector 1
(under blue dot) 1

i}

1

1

Sem
Pu-Be

d,=d,+27.3+5 [i]
Ay/Me= (de)?/(ds)? (ii]

where A,=rem/hr at d,

and A,=rem/hr at d,
rem/hr at d,= (Ay) (d,)*/(de)? fii]
Fieure 14. Diagram of radiation geometry (not to

scale) and calculation of dose rate (rem/hr) at
neutron detector for measurement 10. A, is the dose
rate in rem/hr at a distance d, (cm) from the
Pu-Be neutron source according to calibration in-
formation obtained at Los Alamos. d, is the dis-
tance from the source holder to the center of the
neutron detector. d, is the distance from ‘the source
(point source assumed) to the center of the detector.

At dose rates between about 0.004 and 1.0
yem/hr (Fig. 5), the Concorde instrument re-
sponded essentially the same to Co® gamma
(Aldermaston), Cs** gamma (Kirtland) and

18

Pu-Be neutrons (Los Alamos). Although the
difference was small, results of the calibration
using Am**-Be neutrons (Aldermaston) were
not consistent with the others; for example, in
the range 0.004 to 0.2 rem/hr estimates of dose
rate from meter readings by use of the Alder-
maston neutron curve were higher than the
others by about 25%.

The Kirtland gamma and Los Alamos neutron
curves (Fig. 5) show nonlinearity in the log
dose-rate vs meter-reading plot at dose rates
below 0.003 rem/hr; whereas the Aldermaston
neutron curve suggests linearity down to 0.002
rem/hr. It should be noted, however, that at
rates below 0,004 rem/hr only one neutron meas-
urement each was made in Aldermaston and Los
Alamos. No gamma measurements were made
in Aldermaston below 0.004 rem/hr. Measure-
ments at the lower dose-rates will be considered
in more detail below.

Measurements in Fig. 5, labeled “opposite
meter side”, “meter side”, “moderator end” and
“plug end”, indicate that the Concorde instru-
ment responds equally well to neutrons regard-
less of the side of the instrument facing the
radiation source.

To test the digital readout, which shows total
dose in millirem, the Concorde instrument was
placed at various distances from an uncalibrated
radium needle and rate-meter readings, digital-
reading increments and elapsed times were re-
corded (Table 3). Figure 5 shows a curve re-
lating the meter readings and dose rates com-
puted from digital-reading increments and
elapsed times. Digital-reading derived dose-
rates were higher than indicated by the Os'**
dose-rate vs meter-reading curve. For example,
with the Concorde instrument at a distance from
the radium needle such that the meter reading
was 3.6, the Cs'’ curve showed a dose rate of
0.0018 rem/hr; however, according to digital-
reading increments and elapsed times, the dose
rate was 0.0035 rem/hr. Thus, the dose rate
based on digital readings was 169% higher than
indicated by the Cs**? curve. When the meter
reading was 12.5, the Cs**’ curve showed a dose
rate of 0.11 rem/hr; based on digital readings,
the dose rate was 55% higher (0.164 rem/hr).

Possible reasons for the nonlinearity of the
dose-rate vs instrument response curve at low
dose-rates are considered. Results in Fig. 15



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Fiavure 17. Concorde instrument chart-readings with corresponding dose rates for gamma radiation: different sides
of instrument facing radiation source.

15



CALIBRATION OF THE CONCORDE RADIATION DETECTION
INSTRUMENT AND MEASUREMENTS AT SST ALTITUDE

I. Introduction.

On rare, unpredictable occasions—perhaps one
to five times in each 11-year solar cycle—the
radiation at SST cruise altitude during a solar
cosmic ray event reaches levels normally consid-
ered unacceptable for the general population.t*
To protect passengers and crew from unneces-
sary radiation exposure, airworthiness authori-
ties of Britain and France require that civilian
aircraft, which fly above 50,000 ft, have a solar
cosmic ray warning device.* If the radiation
level reaches 100 millirem/hr, the pilot is to
descend to a lower altitude.

A radiation warning device, developed at the
Atomic Weapons Research Establishment in
Aldermaston, Reading, England, for the Con-
corde SST, was lent to the Office of Aviation
Medicine of the Federal Aviation Administra-
tion (FAA). In April 1969 we received the
instrument (NIS 366/1 detector unit, Ser. No. 3;
NIS 366/2 display unit, Ser. No. 102) with in-
structions to: (1) attach a recorder, (2) calibrate
the detectors, (3) measure radiation levels at
SST altitudes with the Concorde instrument and
(4) compare the Concorde instrument measure-
ments with those made with the High Altitude
Radiation Instrument System (HARIS), a re-
search instrument for cosmic radiation measure-
ments currently being flown by the Air Force
under contract with the FAA.

II. Description of the Instrument.

The Concorde radiation instrument consists
basically of three miniature Geiger-Mueller
counters, which measure the dose from charged
particles and gamma radiation, and a moderated
boron trifluoride proportional counter, which
measures the neutron dose (Fig. 1). The pulsed
signals from the neutron and charged-particle
detectors are amplified, shaped and added. The
processed signals from the two detector systems

drive a single ratemeter. A four-decade log-
arithmic continuous indication of dose-rate
equivalent is produced and displayed on a dial
divided linearly in arbitrary units. A digital
display of the total radiation dose, in millirem,
is also provided.

The response of the neutron counter is propor-
tional to the dose equivalent of the incident
radiation for neutrons with energies from thermal
to 10 MeV; the quality factors for neutrons
yecommended by the International Commission
on Radiological Protection (ICRP) are auto-
matically applied. Fast neutrons are slowed
down by the moderator (mainly polyethylene)
and captured by B.° When B* absorbs a slow
neutron it becomes the unstable BTM which decays
to Li’ by emitting an alpha particle. The ioni-
zation caused by the positively charged alpha
particles is measured.

The desired relative response of the two detec-
tion systems is accomplished by the use of the
three Geiger counters. The response of the
Geiger counters is such that a rem/rad ratio of
1.5 for gamma radiation is automatically ap-
plied.

A calibration check for the Geiger counters is
provided by a Sr radiation source enclosed in a
stainless steel housing inside the instrument near
the Geiger tubes. When the button marked
“test” on the display unit of the ratemeter is
pressed, a shutter in the source housing opens
and the Geiger tubes are exposed to Sr® beta
radiation,

This brief description of the Concorde instru-
ment is based on information provided by Mr.
I. I. McNaughton of the Royal Aircraft Estab-
lishment and a report by T. G. Benbow.®

III. Preparation of the Instrument for In-
stallation in RB-57F Aircraft.

The detector unit was designed to be her-
metically sealed; however, pressure chamber



ACKNOWLEDGMENTS

Individuals in several organizations contributed to this project and it is
a pleasure to acknowledge their assistance. Mr. T. G. Benbow of the United
Kingdom Atomic Energy Authority has been a ready source of technical
information on the Concorde instrument. (uidance and assistance in the
measurements at Kirtland Air Force Base was given by Lt. S. M. Blanken-
ship, Capt. R. B. Philbrick and Mr. J. F. Janni, and at Los Alamos Scientific
Laboratory by Mr. M. J. Engelke and Mr. B. B. Riebe. Dr. E. D. Folk, Mr.
D. N. Faulkner, Miss B. R. Neas and Mrs. R. J. Melton of the Civil Aero-
medical Institute advised and assisted us in data processing. Dr. E. B. Dar-
den and Dr. M. L. Randolph of the Oak Ridge National Laboratory were
consulted on several occasions during the course of the study.



you Be

Blue Dot <—\o

Measurements |- 8 i

Moderator End

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Measurement 9 q

Pu-Be
Plug End ° . be &

Measurement IO

Opposite Pu - Be
Meter Side ° <—_& opposite blue dot
Measurement I{ e
U
qo
Meter Side .

7 Pu-Be
Measurement 12 ° Opposite blue dot

Ficure 11. Position of neutron source relative to Concorde instrument
for measurements 1-12.

il



Tapue 3.—Rate-Meter Readings and Corresponding Digital Readings When Concorde Instrument Placed at Various
Distances From An Unealibrated Radium Needle

Measurement Rate-Meter Elapsed Time Digital Increment Digital Units
No. Reading (min) (Units)* per Hour
(millirem/hr) *
5.97 99. 17 10.3
3.6 104, 6 3.46
15.3 6. 54 540.
12.5 31.5 86 164.
10.5 94. 119 76.
8.5 59.5 28 28.2
4,75 83. 8 5.8
7.5 124, 40 19.4
6.0 147, 25 10.2
1.5

*A unit is one millirem.
+No correction was made for “background”.
tDetectors exposed to a Sr® test source located inside the Concorde instrument.

10.06

0001

0.0001 r 1 1 n L L 1

line calculated from dato
denoted by open circle

Gamma (Cs!37, Kirtlond)

© Cesium source in source-off plug-out configuration

© Cesium source in sour:

plug-in configuration

1 1 1 1 1 n 1. A

g 4 5 @ 7 @ 2° To

ir 12
CHART READING

1s 14 1s 16 iT 8 is 20

Fieure 15. Concorde instrument chart-readings with corresponding dose rates for gamma radiation: calibration
curve,

show gamma radiation dose-rates and correspond-
ing Concorde instrument chart-readings (data
from Table 1 measurements 1-33 and 76B-91,
calculations in Fig. 8-10). Between 0.014 and
2.8 rem/hr with the Cs'*? source in its high dose-
rate configuration (source-off plug-out, see Table

1 footnote {+), the chart readings increased
linearly with logarithmic increase in dose rate.
A straight line, fitted to the data points by the
least squares method, was extended to lower dose
rates so that the high dose-rate data could be
compared with low dose-rate measurements made

14