"
...".
**
"
"
'^ = ",
.
t
;
;
.
.
.
.
.
"
!
.
.
...
.
..
.....
.
...
.
.
.
.
.
.
..
.-. "
Y
r
y
..
.
..
..
1.
*
.
:.
.
:
:.-
.1
NUW
AIT
.
'
IV
.
S
.
.
T
..
71
.
:
:
:
.
.
UNCLASSIFIED
ORNL




TIT
HTX
Wypit,
.
..
IT
.

;
:
.
.
..
E
+:
-
++
-
+
-
-
1

2
.
....
1069
.
.'
.
.';
.
.
.
.
-
PR Nu 8-1069


Vladic-OFFICIAL
LUTET
lemy-650201-3
9.1
ORHI - AIC - OFFICIA
MAR? 3 1965
HIGH-TEMPERATURE HIGH-VACUUM THERMOCOUPLE DRIFT TESTS
J. W. Hendricks and D. L. Mchiroy
Metals and Ceramics Division
MASTER
INTRODUCTION

8. na
disanat, or prorlewa na
privately owned rightona; or
will the Coonstont, or wa employment with much contractor.
soch saployee or contractor of the Coe aloston, of employee of such contractor properes.
to, nay taformation part
ploys or conincter of the Collanton, or asaployee of such contractor, to the extrat that
As und in the abon, "price acthangao bello de Couglaston" oncluded my e-
uny liabiliun with respect to the w
un of any lalorquation, appendu, crthod, or proces dacloud sa to report,
of way totoraation apparatus, method, or procum declound in the report my cot intrare
nicy, completasun, or watalow of the lodormado contatoed in this report, or that the se
A. Makao may irruly or mountauation, aprened or implied, with respect to the accu.
San, sor the Commission, nor wy porno nella on ball of the Coaalkon:
This report me prepared ML Account of Government sponsored work. Neither the VAIKA
ol, or for de
to Ho saplogant or contract
results from the
LEGAL NOTICE
Numerous experiments in the region 1000 to 1450°C at pressures in
the range 106 to 10 8 torr require reliable and accurate temperature
measurement. Varying degrees of success have been achieved using opti-
cal pyrometers or high-temperature thermocouples; however, none of these
appear to be a panacea. A literature survey-10 revealed a virtual lack
of thermocouple drift data for this temperature and pressure range. This
information void was unduly complicating many types of tests in which
temperature control was important. In order to prevent every experiment
fron becoming a thermometry test, a facility was constructed and tests
were restricted to those operating conditions and to commercially avail-
able noble- and refractory-metal thermocouples. The results, though
limited in scope, have increased our knowledge of thermocouple perfor-
mance and should be instrumental in the design of future experiments.
It was beyond the scope of this work to study in detail the criteria
for selection and application of high-temperature thermocouples to attain
maximum thermoelectric stability. 11 Rather, in the scope of these tests,
it was decided to select a few test materials, to rely on some of the
reported test results to circumvent the cause of thermoelectric insta-
bility, and to obtain useful design information..
PENICU,15ANCE OStr .
5
THE PUBLIC IS APPRUVED. pris was
ARE ON FILE IN THE RACEJVING Skiishia
TEST METHOD
The drift test facility was designed to allow extended testing at
temperatures up to 1500°C at pressures below 10 torr. This test
facility has many of the features of those used in the previously
reported stability studies on base-metal thermocouples. 12 The present
test allows the hot junctions of the test thermocouples to be held con-
tinuously at the temperature of an isothermal zone block of niobium.
The emf stability was monitored as a function of time, and the nominal
zone block temperature was ascertained by intermittent insertion of a
thermocouple referee or by intermittent reading of an optical pyrometer
sighted into a black-body cavity in the block. Figure 9.1 16 a schematic
drawing showing the major features of the facility.
OINI - AEC - OFFICIAL
A niobium bar, 1 1/8-in. diam by 4 in. long, constituted the iso-
thermal zone block. The lower half of this verticall
contained 16 reentry holes, 1/8-in. diam by 1 3/4 in. long, for the
test thermocouples and a central hole for the movable referee thermo-
couple. The upper hall of the block contained a black-body cavity,
which was formed by an axial hole, 3/8-in. diam by 1 3/4 in. deep,
threaded and capped with a plug containing a 3/16-in.-diam sighthole.
ORNI - AEC - OFFICIAL
UNCLASSIFIED
ORNL-DWG 64-4932

-OPTICAL
PYROMETER
-VIEW PORT
IONIZATION
GAGE-
Io
GETTER-ION
PUMP
BLACK BODY
CAVITY
-Togo WO COIL
NIOBIUM
ISOTHERMAL
TEST BLOCK-
-TO RADIATION
: SHIELDS
COLD WALL VACUUM
CHAMBER
REENTRY
TEST TC-
GRADIENT
TEST TC
INTERNAL
REFERENCE
BLOCK
LC/A=
ICE
BATH
COPPER LEADS
MOVABLE
REFEREE
TC
K-3 POTENTIOMETER
AND SWITCHES
- COMPRESSION SEAL
- MOVABLE REFEREE TC
SLIDING TC
HOUSING
-MOVABLE EXTERNAL
MAGNET
9.2
829
inijosiu -
i
- inos
Fig. 9.1. Schematic Drawing of the Drift Test Facility.
9.3
This block was mounted vertically inside a Ta-10% W alloy heater
coil, 2-in. ID and 6 in. long. This coil was mounted on and completely
surrounded by three tantalum radiation shields. A variable step-down
autotransformer was used to adjust the voltage applied to the furnace
winding. The furnace assembly was supported by a stainless steel stand
mounted on a stainles6 steel base plate,
The base plate contained several components critical to the test,
A water-cooled copper reference junction block was mounted on the plate
to provide cold juctions between the test thermocouples and copper
extension leads. This internally contained reference junction not only
reduced the length of wire needed per test thermocouple but also solved
the troublesome problem of multiple vacuum seals for the various ther-
mocouple materials. The penetration of the copper wires and two
Chromel-P/Alumel thermocouples (which were used to monitor the refer-
ence junction temperature) was sealed using Teflon compression glands
mounted in tubes 6 in. below the base plate. This stand-off seal
allowed bakeout of the base plate prior to testing. The copper wires
extended to two L&N thermal-free, two-pole, twelve-position switches
which allowed thermal emf measurements to be made with a K-3 potenti-
ometer. An icebath cold junction with twist connections to copper wires
was used for the Chromel-P/Alumel reference junction thermocouples. The
base plate also contained a bakeable 400-anp copper-ceramic feed-through
to supply electrical power to the furnace. Finally, the base plate
contained a centrally located l-in.-diam, 17-in.-long stainless steel
tube, which housed the mechanism for moving the PtgoRh10/Pt referee
thermocouple into electrical contact with the top of the central hole
of the niobium isothermal block. The mechanism consisted of a short ..
iron cylinder moved vertically inside the stainless steel tube by means
of an external magnet. The leads of the referee were allowed to flex
within the stainless steel tube prior to joining copper wires at the
reference block.
A deformable copper compression gasket sealed the base plate to the
cold-wall stainless steel vacuum chamber. The top of this chamber con-
tained a viewing port (for sighting into the black-body cavity with an
optical pyrometer), a 15 liter/sec getter-ion pump, a Veeco hot cathode
ionization gage, Model RG 31A, for measuring the chamber pressure, and
a copper evacuation line which was crimp-sealed after the initial vacuum
bakeout of the system.
A number of pretest operations were performed in preparing a drift
test. The niobium isothermal zone block was pickled in 35 HNO 3-15HF-50H2O)
and annealed at 1000°C for 2 hr at 1 x 106 torr. The Morganite ARR
alumina sheathing (used on all bare-wire tests) was boiled in
50 HNO3-50 H2O for 4 hr and dried at 1000ºC for 72 hr at 1 x 10°3 torr.
This treatment is thought to reduce the iron content of the insulators.
The thermocouples to be tested were fabricated and located in the niobium
isothermal block, the electrical check-outs completed, the system sealed,
and a bakeout performed. The test chamber was evacuated to 3 X 105 torr
using a mechanical promp and an oil diffusion pump. The getter-ion pump
9.4
was used to achieve 7 X 10 6 torr. The system was helium leak checked
and then baked for 24 hr using 150°C steam in the water-cooling chambers,
The copper evacuation line was then crimped off, leaving only the getter-
ion pump to maintain the pressure. The furnace system was then heated
to obtain data at 800, 1000, and 1200°C prior to drift testing at higher
temperatures.
Data were obtained periodically by raising the referee thermocouple
into the isothermal block, allowing 20 min for equilibration, recording
the thermal emf of the system's thermocouples and the optical pyrometer
reading, and lowering the referee. The referee thermocouple was made
from 0.020-in. diam platinum and PtooRh 10 wire. Although this referee
thermocouple was continuously in the system, most of th
not at the high temperature of the 1sothermal block but at a location
where the temperature was 300°C. The optical pyrometer reading was
obtained by sighting the black-body cavity with a Model 95 Pyro Micro-
Optical, disaypearing filament pyrometer. The temperature indicated
was lower than the referee thermocouple by as much as 85°C at 1300°C
and 100°C at 1450°C. No attempt was made to correct for absorption
in the night port and the prism because the optical reading followed
changes detected by the referee thermocouple to within a few degrees.
All of the test thermocouples indicated temperatures different from
those of the referee thermocouple due to slightly different vertical
positions and to initial calibration differences. For present purposes,
these differences are inconsequential in this test since the purpose of
the test was to measure the change of thermal emf with time at tempera-
ture. This can be accomplished by comparison with the initial reading
of a particular thermocouple if the furnace temperature is maintained
constant during the test. The referee thermocouple and the optical
pyrometer indicated that the furnace temperature was maintained constant
to better than 110°C during these tests. The temperature indicated by
the referee thermocouple is reported as the nominal temperature for each
test.
MATERIALS TESTED AND RESULTS
Three tests have been completed using this facility and the salient
features of these tests are shown in Table 9.1. Test I was exploratory in
nature and yielded interesting results. Test II was a planned repeat on
certain aspects of Test I with several new configurations and materials.
Test III 16 a continuation of Test II after rem:)val of several unstable
sheathed thermocouples.
Test I was performed on the four types of high-temperature thermo-
couples listed in Table 9.2. These thermocouples were insulated with pre-
treated two-hole ARR alumina sheaths. The hot junctions of the noble-
metal thermocouples were prepared by tungsten-arc inert-gas welding, the
gradient thermocouple, wires were tweezer-welded to the niobium block to
make the hot functions through the block, and the refractory-base thermoc
couple hot Junctions were twisted for 1/4 in. and wire-wrapped with
0.002-in. tungsten wire.
9.5
Table 9.1. Conditions of the Thermocouple Drift Tests
Test
No.
Nominal Time at Average
Temperature Temperature Pressure
7°c)
(hr) (torr
Remarks
1300
352
2 x 10-7
Planned termination prior to
1450°C test
Planned termination after
1012 hr
1450
1012
4 x 10-8
II
II
2200
143
1 x 10-6
III
1315
100
1 x 10-6
1x 10-2
Stopped to remove drifting
thermocouples
Planned termination prior to
1425°C test
Test stopped 600 hr
1425
600
Table 9.2. Thermocouples Evaluated in Test I at
1300°C (350 hr) and 1450°C (1012 hr)
Wire
Size
(in.)
0.020
Thermocouple
Conver-
sion
Table (Ref)
Position
in Block
Reentry
Source
Number :
Tested
2
Pt90 Rh10/Pt
(13)
PtgRhG/Pt70Rh30
0.010
Reentrya
2
(14)
Sigmund Cohn,
reference grade
J. Bishop Co.
standard grade
J. Bishop Co.
standard grade
J. Bishop Co.
standard grade
Pt9476/Ptqo Rh 30
0.020
Reentrya
Pt 94 Rh6/Pt70Rh30
0.032
Reentrya
2.
Pt 94 Rh6/Pt70Ah 30
0.020
Gradient
W/W74RE 26
W9sRe 5/W74RE 26
(16)
0.020
0.020
J. Bishop Co.
standard grade
Englehard Inc.
Hoskins Manufac-
turing Co.
Reentrya
Reentrya
"Reentry position means inserted in a hole in the niobium block.
Gradient position means strapped on or tweezer-welded to the bottom
of the niobium block.
9.6
Table 9.3 lists the temperatures indicated by the referee and the
optical pyrometer as well as the chamber pressure for Test I at 1300°C.
The referee thermocouple and optical temperatures differed by 70 to 90°C
and were fairly consistent indications of the change of the block temper-
ature from one time to the next. Any differences were perhaps due to
variations in the vertical placement of the referee thermocouple. The
block temperature was constant within +10°C, which is sufficient for
this test. The average temperature indicated by the two thermocouples
of each type tested is listed as well as the difference between this
average at several times and a value obtained early in the test. There
is an amazing consistency in the test thermocouples in indicating the
block change in temperature from data point to data point. These results
are plotted in Fig. 9.2 and show that after 352 hr at 1300°C there is no 1
preference among the thermocouples tested. Additional proof of this can
be observed from the AT 2 values listed in Table 9.3 and plotted in Fig. 9.4
The AT2 values represent the temperature difference between the referee
and a particular test thermocouple and thus include both calibration
differences and differences caused by position in the test block. These
values are perhaps more indicative of the very nominal drift which
occurred at 1300°C since furnace temperature variations are removed in
calculating AT 2. Thus within +5°C there was no thermal emf drift at
1300°C in 352 hr at 2 x 10 torr.
These results were unexpected; so the test temperature was elevated
to 1450°C and heid there for 1012 hr in order to promote drift if any
should cccur. The results obtained at 1450°C are tabulated in Table 9.4
and plotted in Fig. 9.3. The thermocouples in the reentry positions did
not exhibit any drift of thermal emf to within 18°C. However, the
PL94Rh6/ Pty oRh30 thermocouples welded to the niobium test block (and
thus in a severe temperature gradient) did drift negatively by approxi-
mately 80°C. This is believed to be due to niobium diffusing into the
hot junction, thus altering the wire composition. Because of the severe
temperature gradient, this inhomogeneity caused the observed decrease in
thermal emf.
After accruing 1012 hr at 1450°C, the system was cooled to 1300°C,
as indicated by the referee, and rechecked at this temperature. The
reentry thermocouples agreed with the previous data at 1300°C to within
10°C, as shown in the last column of Table 9.3. This is additional prvof
that the reentry thermocouples did not drift during Test I.
Thus, Test I shows: (1) No preference exists among the thermocouples
tested in reentry positions from the viewpoint of drift behavior for this
time, temperature, and environment. Implied by this is that neither alloy
content nor wire size is an important variable. (2) Thermal emf drifts
as large as 80°C/1000 hr at 1450'C may possibly be expected for all thermo-
couples welded to niobium and exposed to a severe temperature gradient,
although this effect was noted only for the Pt 9 RH6/Pty oRngo thermocouples
in Test I.
Table 9.3.
Thermocouple Drift Data Por Test I for 352 hr at 1300°C
(5 of 17 readings)
Duration of Test in Hours
63 160 232
Duration 66 Test 12 Hours 32810350
ORNI ~ All - OFFICIAL
328
Test Thermocouple
PtgoRh 10/Pt
T(°C)
1273
1267
1272
1272
1270
1271
AT1
+33
+31
+36
+32
+30
+19
AT2
Ptg4RhG/P+ 70 Rh30
(0.010-in. diam)
1264
1258
1265
1257
1258
6
AT,
+1
+43
1246
-18
+54
AT 2
+42
+40
+43
Ptg 4Rh6/PtmoRh30
(0.020-in. diam)
1254
1248
1255
1245
1247
-7
-6
+1
1244
--10
+54
52
+50
+53
+57
+55
AT 1
AT 2
Ptg & Rh6/PtooRh30
(0.032-in. diam)
1263
1256
1259
1258
ATI
1265
+2
-5
1250
-13
+50
+43
+42
+43
+45
+42
AT2
Pto4 Rh6/Pt70Rh30
(0.020-in. diam
gradient)
1237
1247
1240
0
+56
1254
+14
+54
+7
1244
+4
+56
1150
90
-150
+62
+57
W/W17 4RE 26
1255
1264
1259
1257
1253
1262
0
+44
+2
+43
+44
+45
+43
+47
AT2
Wo 5 Reg/W4Re 26
1286
1278
1278
1278
1283
3
+25
1288
+2
+12
+26
+22
1300
+20 +20
Isothermal Block Temperature (°C)
Ptg o Rh 10/Pt, Thetares 1306 1298
Optical Pyrometer 1215 1215
(uncorrected)
Chamber Pressure, 20
torr (x1007)
1308
1220
1304
1220
1300
1209
1220
1.6
1.1
0.07
For each thermocouple the quantities reported are: T, reading of test
thermocouple; AT 1 (Theme - Is hood of test thermocouple; AT2 (Trefense
"test thermocouple' at the particular time.
Data at 1300°C after being at 1450°C for 1012 hr.
Seriesonicial


9.8
DWG 64-4931
Fig. 9.2. Test Conditions: 1300°C, 352 hr, 2 x 10°7 torr. (a) Inter-
nal comparison of thermocouples of Test I. Isothermal zone block tempera-
ture during Test I at 1300°C. (b) Temperature difference of referee thermo-
couple and thermocouples of Test I.
OINI - AEC - OFFICIAL
UNCLASSIFIED
ORNL-DWG 64-4931
O'RNI,-ATO - OFFICIAL
• Pigo Rho/PI
* Piga Rhe/ Plzo Rh30 (0.010)
Piga Rh6/ Pito Rhzo (0.020)
• Piga Rh6 / Pino Rh30 (0.032)
• Plod Rhe/Pipo Rh30 (0.020 GRADIENT)
o W/W 74 Re26
o Wgs Reg/W74 R$ 26
.

AT, (c)
lo-90°C)
:
REFEREE
TCC)
T (°C)
OPTICAL +1035 hr
- AT 1450°C
1290 Fla
am
+1035*
(1450°C)
(-150°C)
52
the
ATA (C)
ORNL - AEC - Official
50
100
150
250
300
350 (0 AT +12) ........
200
TIME (hr)
ORNL - AIC - OIFICIAL
81.5%
i
9.9
Table 9.4. Thermocouple Drift Data for Test I for 1012 hr at 1450°C
(5 of 36 readings)
+2
+4
+55
T
+2
-12
+2
+47
+49
Duration of Test in Hours
Test Thermocouple
166
406
718
910
PtgoRh 10/Pt
T (°C)
1428
1416
1430 1432
1428
AT,
-12
AT 2
+34
+33
+28
+28
+28
Pt. 4 Rh6/PtroRh30
(0.010-in. diam)
1409
1394
1403 1400
1395
AT1
AT 2
+55
+60
+61
Pto4 Rh6/PtroRh30
(0.020-in. diam)
1401
1385
1400
1403
1397
ATI
-16
AT2
+61
+64
+58:
+57
+59
Pto4 Rh6/Pt70Rh30
(0.032-in. diam)
1411
1400
1411
1413
1410
AT1
AT2
+49
+47
+46
Ptg 4 Rh6/Pt70Rh30
(0.020-in. diam
gradient)
1388 : 1360
1358
1338
1316
-28
-30
-50
-72
AT2
+74
+89
+100
+122
+140
W/W74Re 26
1415 1402
1414
1416
1415
0
AT2
+47
+41
W95 Res/W74RE 26
1469
1452
1468 1475
1466
AT1
-17
+6
AT2
-10
Isothermal Block Temperature (°C)
PtgnRh 10/Pt, Treferee: 1462 1449 1458
1460
1456
Optical Pyrometer
1360
1350 1361 1366 1362
(uncorrected)
Chamber Pressure, 54
8.3
torr (x 2008)
For each the wocouple the quantities reported are: T, reading of test
w of test thermocouple;
im
referee
* test thermocouple) at the particular time.
0
-13
+47
+]
+44
-3
15 8.
35
15
ORNI - AC-OFFICIAL
thermocouple; AT i
time
pericular time.
UNCLASSIFIED
ORNL-DWG 64-4939

www.smm
.
.
AT (°C)
• Ptgo Rho/pt
* Piga Rh6/Piyo Rh30 (0.010)
Piga Rhe/P170 Rh30 (0.020)
• Plga Rho/P170 Rh30 (0.032)
• Piga Rho/Piro Rh30 (0.020 GRADIENT)
o W/W74 Re26
o Wyg Reg/W74 Re26
whe
-OPTICAL
T (°C)
hos
REFEREE
т РС)
1350
(20) 20-
O
100
200
300
400
600
700
800
500
TIME (hr)
900
Fig. 9.3. Test Conditions: 1450°C, 1012 hr. 6 x 10°8 torr.
(a) Internal comparison of thermocouples of Test I. Isothermal zone
block temperature during Test I at 1250°C. (b) Temperature difference
of referee thermocouple and thermocouples of Test I.
9.11
Test II was initiated to confirm the results of Test I and to test
other configurations. The thermocouples tested in Test I. are listed in
Table 9.5. In the process of raising the test temperature to 1300°C, it
was decided to test for a short time at 1200°C. This temperature proved
to be sufficient to cause significant thermal emf changes in the niobium-
and tantalum-sheathed MgO-insulated Pt 9 Rhro/ Pt thermocouples. This
drift was so severe that Test II was terminated after 143 hr at 1200°C
in order to remove these bad actors prior to testing at 1300°C. The
results obtained in Test II are listed in Table 9.6 and plotted in
Fig. 9.4. The gross negative drift of the above-mentioned sheathed
thermocouples is apparent. The other thermocouples confirm the Test I
results in that within +10°C no drift occurred at 1200°C in 143 hr.
Thus the reentry, the partial reentry, and the gradient thermocouples
of all varieties, not insulated with Mgo, did not differ in performance.
It is significant that the tantalum-sheathed BeO-insulated Wo Res/Wry 2Re 26
thermocouples in the reentry positions did not drift in thermal emf in
contrast to the tantalum-sheathed MgO-insulated Ptoo Rho/Pt thermocouples.
This difference is believed due to the different insulators rather than
the thermoelements. In any case, these results sound a warning on use
of metal-sheathed MgO-insulated thermocouples in high vacuum at high
temperatures.
The removal of the four bad thermocouples of Test II allowed
several partial reentry thermocouples to be added to Test III. The
actual thermocouples tested in Test III are listed in Table 9.5 and
represent a slight extension of Test II. Four types of thermocouples
were exposed at reentry, partial reentry, and gradient positions.
These positions were selected to show that a third metal (niobium in
this case) diffusion in the temperature gradient of the hot junction
was required in order for the negative drift observed for the gradient-
positioned PtgRh6/ Pty oRh3o thermocouples of Test I to occur.
Test III was initiated by 100 hr of exposure at 1315°C with the
results listed in Table 9.7 and plotted in Fig. 9.5. The vacuum was
not as good as in Test I; the optical pyrometer was in significantly
closer agreement with the referee thermocouple than in Test I. The
test results do not show any significant thermal emf drift and thus
confirm the Test I results at 1300°C. The variation in AT2 among the
reentry thermocouples was smaller in Test III (+3°C) than in Test I
(+16°C) because more care was taken in aligning the hot junction
positions in the reentry positions in preparing for this test. The
results of Test III at 1315°C did not show any drift for the various
thermocouple positions. Since drift was not observed, even for the
gradient thermocouple in Test I at 1300°C, these results were as
expected.
Test III was continued by raising the temperature to 1425°C and
yielded the results listed in Table 9.8 and plotted in Fig. 9.6. Again
the conditions of this test were slightly different from those of
Test I at 1450°C. The vacuum was not quite as good, but the optical
pyrometer and referee readings agreed much better. There was good
9.12
Table 9.5. Thermocouples Evaluated in Tests II and III
Wire
Size
(in.)
Position
in Block
Number
Tested
Test
Number
Thermocouple
Source
PtgoRh20/Pt
0.020
Reentry
II, III
Sigmund Cohn Co.,
reference grade
PtgoRh10/Pt
0.020
Gradient
i
II, III
Sigmund Cohn Co.,
reference grade
Pt 9oRh10/Pt
0.020
III
Sigmund Cohn Co.,
reference grade
Thermo-Electric,
Inc.
PtgoRh2o/Pt
0.010
Partial
reentry
Reentry
1/16-in.
Ta, MgO
Reentry
1/16-in.
• Nb, Mgo
Reentry
Ptgohid/Pt
0.010
Continental Sensing
Inc.
2
II, III
J. Bishop Co.,
standard grade
Ptg4Rh6/Pty oRh30
Ptg4Rb6/Ptyo Rhzo
Ptg4Rba/Pty oRh30
0.020
0.020
0.020
Gradient
1
II, III
III
Partial
reentry
Gradient
J. Bishop Co.,
standard grade
J. Bishop Co.,
standard grade
Eaglehard, Inc.
Englehard, Inc.
II, III
W/W74Re 26
W/W7 4RE 26
0.020
0.020
III
Partial
reentry
Reentry
Wyg Res/Wy 4RE 26
0.020
II, III
W9g Res/W4Re 26
0.020
Partial
reentry
Gradient
Hoskins Manufac-
turing Co.
Hoskins Manufac-
turing Co.
Hoskins Manufac-
turing Co.
Continental Sensing,
Inc.
0.020
II, III
Wg5Res/W74RE 26
Wyg Res/Wy4Re 26
0.010
2
II, III
Reentry
1/16-in.
Ta, Beo
Partial reentry means inserted less than 1/2 in. Into niobium block
but not touching the niobium block.
9.13
Table 9.6. Thermocouple Drift Data for Test II for 143 hr at 1200°C
Thermocouple
and Position
Duration of Test in Hours
773 7579 95 19123
Ptg oRh2o/Pt
Reentry
1210
1213
216
1313
130s
1222
+12
ATa
T,
PtgoRha /Pt
Gradient
1210
1210
1213
1306
1208
0
1210
+2
༢
+5
1219
+11
༥
AT
AT
Ptsoma d/pt
Ta, Mgon
ཀ་
AT
Pt9ORk10/Pt
Nb, Mgo
11e7
， 118
。
942
119
-35
862
1150
37
862
847829
1139 1139 1128:
-3445
226
1132
56
1207
1143
1167
ལ0
1166
41
1167
0
1155
-52
1146
61
AT
Pt94 Rh6/Ptry Rhzo
Reentry
་ 1199
1192 1197
045
+179
1197
+5
1196
+4
+1,
1193
+1
8
1208
+16
8
+8
ATi
AT
w/w7ARe26
Gradient
ཀྱ་
AT，
AT
W9 Res/W74RE 26
Reentry
1193
1188
1191
0
418
1192
+1
+13
1194
+
1202
+11
+2
13
•13
413
1235
1234
1235
232
1235
1229
1242
༡
c7
28
-30
28
Ar
AT
W95 Reg/W7 4Re 26
Partial reentry
1227
1226
1325
1226
1220
1234
。
༤ ཕྱི་
-18
20
1s
9.14
Table 9.6. (Continued)
Thermocouple
and Position
7
73
Duration of Test in Hours
75 7995119143
Weg Reg/W7 Re26
Gradient
T
1226
1224
1225
1222
1219
AT
1225
-1
-18
1232
+6
17
AT2
18
20
ܬܪܢ
-18
1237
1238
1236
1238
1233
1245
+6
30
31
33
-31
-32
-30
Wyg Res/Wy2Re 26
Та, Beo
1239
AT1
AT 2
PtgoRhıd/Pt
Preferee 1209
Optical Pyrometer
1150
Chamber Pressure. 5
torr (* 10°6)
1206
1205
1208
1207
1201
1215
.
1155
1.2
1155
1.1
1155
1.0
1155
0.87
1150
0.68
1160
0.67
For each thermocouple the quantities reported are: T, reading in
°C of test thermocouple; AT, (Tim - Ty nood of test thermocouple;
22 (Preferee - Ttest thermocoupled at the particular time.
• Ploo Rho/P1 (REENTRY)
Pigo Rhop! (GRADIENT)
• Plgo Rho/PI, To, MgO
(000) ACTUAL READING OF
ONE SUCH T/C
• Pigo Rho/PI, NB, Mgo
20
UNCLASSIFIED
ORNL-OWO 64.4929R
* Piga Rho/P170 Rh30 (REENTRY)
o W/W74 R26 (GRADIENTI
o Wgg Reg/W74 Re26 (REENTRY;
o Wys Reg/W74 Rez6 (PARTIAL REENTRY
Wgs Reg/W74 Rez6 (GRADIENT)
• Wgg Res/W74 Re26. To, Beo
OINI - ACC

(1197)
0
97, CC)
(1942) (862)
(8621
1 847)
(829)
(226)
1210
REFEREE
TPC)
OPTICAL
1150 ?
1140
..
Ata (°C)
25
50
100
125
150
75
TIME (hr)
ORNI - AEC - OFFICIAL
Fig. 9.4. Test Conditions: 1200°C, 143 hr, 1 x 10*6 torr. (a) Inter-
nal comparison of thermocouples of Test II. Isothermal zone block temper-
ature during Test II at 1200°C. (b) Temperature difference of referee
4:32.919 ornunla and thermocouple of mest. TT.
9.16
OINE - AIC - OIFICI
Table 9.7.
Thermocouple Drift Data for Test III for 99 hr at 1315°C
Thermocouple
and Position
I
Duration of rest in Tours
Duration of Tegt in How
75
99
Pt, oRh 10/Pt
Reentry
1306
1326
+20
1325
+19
1326
+20
-10
1327
+21
-12
ATI
AT 2
Pt. Rh 10/Pt
Gradient
1289
1307
1308
1307
+18
AT1
1306
+17
+10
+29
+18
+14
+13
+9
+8
AT2
Ptg o Rh 10/Pt
Partial reentry
1284
1301
1302
1303
+19
+18
+17
+18
1304
+20
12
+18
+15
+14
ATI
AT 2
Ptg 4 Rh6/Pt70Rh30
Reentry
1303
1328
1331
+28
-10
AT,
1324
+21
-8
1325
+22
+25
-12
· AT 2
Ptg 4Rh6/Ptro Rh30
Gradient
1289
1315
+26
1307
+18
+9
1304
+15
+12
1305
+16
+11
+13
+6
AT 1
AT 2
Ptg 4Rh6/Pt70Rh30
Partial reentry
1281
1298
1301
1307
+26
+14
+27
+20
1303
+22
+13
+21
+18
+15
AT2
AT2
W/W74 Re26
Gradient
1299
1322
1318
+19
1317
+18
1320
+21
+23
AT,
AT,
+3
+3
W/W74 Re26
Partial reentry
1310
1327
+17
1326
+16
-10
1324
+14
1325
+15
AT 1
AT2
ORNI - All-OSSICIAL
9.17
OINI - AIC - OFFICI
Table 9.7.
(continued)
1
— раво
1322
AT 2
+21
+8
Thermocouple
Duration of Test la Hours
and Position
75
99
Wos Res/W74Re 26
Reentry
1303
1322
1321
1324
ATI
+19
+18
+19
+21
5
W9 5 Res/W74 Re26
Partial reentry
1293
1313
1312 1314
1315
AT1
+20
+19
+22
AT2
+9
+2
Wg 5 Reg/W74 Re26
Gradient
1290
1310
1308
1310
1311
AT 2
+20
+18
+20
+21
+12
+11
+8
+6
Wg 5 Res/W74 Re26
Та, Beo
1327 1325
1327 1328
+19
+17
+19
AT2
-21
-12
Ptg oRh 10/Pt, Treferee 1302 1321 1316
1316
1316
Optical Pyrometer, T 1270
1275 1282 1290 1290
Chamber Pressure, torr 4.6 x 10-6 4.5 x 10-6 4 x 10-6 1.1 x 10°6 8 x 10°7
AT2
+5
1308
AT 1
+20
For each thermocouple the quantities reported are: T, reading in °C
of test thermocouple; ATi (Time - T, nr) of test thermocouple;
A12 (Preferee - Ttest thermocouple at the particular time.
ORNI - AC - OFFICIAL
9.18
bar
Fig. 9.5. Test Conditions: 1315°C, 99 br, 1 x 10°6 torr. (a) Inter-
nal comparison of thermocouples of Test III. Isothermal zone block tem-
perature during Test III at 1315ºC. (b) Temperature difference of
referee thermocouple and thermocouples of Test III.
ORNL - AIC - OFFICIAL
UNCLASSIFIED
ORNL-DWG 64.4928
• Pigo Rho/P1 (REENTRY)
Pigo Rho/P1 (PARTIAL REENTRY)
o Plgo Rho PI (GRADIENT)
Piga Rhoptzo Rhzo (REENTRY)
Ptge Rho/P170 Rh30 (PARTIAL REENTRY)
• Ptge Rho/P170 Rh30 (GRADIENT)
• W/W74 Re26 (PARTIAL REENTRY) 7
• W/W74 Rez6 (GRADIENT)
Wgg RegW74 Re26 (REENTRY)
Wg5 Res' W74 Rez6 (PARTIAL REENTRY) -
Wg5 ResW74 Rez6 (GRADIENT)
o W95 RegW74 Rez6 (To-Beo)

AT, (°C)
1330
REFEREE THERMOCOUPLE
1290
1270 k*
OPTICAL PYROMETER
AT2 (°C)
TI - AIC - OFFICIAL
16)
20
40
60
80
120
TIME (hr)
s. 1s
. Table 9.8. Thermocouple Drift Data for Test III for 382 hr at 1425"C
Duration of Test in Hours
46190310
Thermocouple
and Position
Ptg oRh 10/Pt
Reentry
140
1441
10
16
144
to
+1
-14
-
༈
-14
Ti
m,
Ptg o Rh 10/PC
Gradient
-16
17
1417
1420
17
+0
+9
149
2
1323
+6
+3
༔
+7
AT
T,
Ptg oRh 10/Pt
Partial reentry
1414
+0
1420
1425
s
ri
130
+2
+7
+༩
123
+5.
+4
+g
+5
za
Ptg 4Rh6/Pt Rh30
Reentry
1437
1337
1436
133
iའn
+o
+0
-10
T
AT,
Ptg 4 Rh6/Pt70Rh30
Gradient
1410
1403
1404
1402
+0
107
-3
420
+16
+
4
+26
+25
ma
Ptg 4Rh6/Pt70Rh30
Partial reentry
1411
1416
+0
112
+1
+15
ཙྪཱ
141s
+༩
r;
T,
1415
+4
+11
+༩
+10
+15
W/W74Re26
Gradient
1426
ཙྩུ
1-29
r
1427
+1
1
142e
43
126
+0
+0
40
+4
+3
Na
v/vzRea6
Partial reentry
1430
126
1328
16
143o
+0
，
to
40
ཞལ
9.20
Duration of Test in Hours
46
190
310
-
382
Thero scouple
and Fosition
W95 Res/Wy4 Re26
Reentry
1437
1436
1434
1437
AT 1
1438
+1
+0
1
ܢ-
AT2
W9 5 Re5/W94 Re 24
Partial reentry
1432
1429
+0
428
1431
1429
+0
-1
+4
+2
AT I
AT2
Wo 5 Res/Wy2Re 26
Gradient
T
1424
1424
1422
-2
1425
+1
AT,
+0
+2
*o
AT2
+2
W9 5 Res/W74 Re26
Ta, Beo
1443
1442
1446
1445
+0
+2
-15
1427
-17
Ptg o Rh 10/Pt, Treferee
1426
Optical Pyrometer, T 2395
Chamber Pressure, torr 2.4x10*6
1441
-2
-15
1426
1400
4x10-7
-16
1430
1397
2.2x10-7
-18
1427
1397
2x10-7
1395
1x10-6
For each thermocouple the quantities reported are: T, reading in °C
of test thermocouple; AT
d) of test thermocouple;
AT 2 (Treferee - Ttest thermocouple) at the particular time.
ORNI - AC - OFFICIAL
9.21
Fig. 9.6. Test Conditions: 1425°C, 400 hr, I x 10°7 torr. (a) Inter-
nal comparison of thermocouples of Test III. Isothermal zone block temper-
ature during Test III at 1425°C. (b) Temperature difference of referee
thermocouple and thermocouples of Test III.
•oo ••L
• Pigo Rho/P1 (REENTRY)
o Pigo Rho PI (PARTIAL REENTRY)
o Pigo Rho Pt (GRADIENT)
Pige RhG/Plzo Rh30 (REENTRY)
Piga Rho/pizo Rh30 (PARTIAL REENTRY)
Ptge Rhe/ Piyo Rh30 (GRADIENT)
UNCLASSIFIED
ORNL-DWG 64-5070
• W/W74 Re26 (PARTIAL REENTRY)
O W/W74 Re26 (GRADIENT)
Wgg Reg/W74 Re26 (REENTRY)
O W95 Reg/W74 Re26 (PARTIAL REENTRY)
Wos ResW74 Reza (GRADIENT)
o W9s Res/W74 Re26 (Ta, Beo)
ORNI - AIC-OFFICIAL

AT, (°C)
REFEREE.
T (°C)
lo)
OPTICAL
AT2 (°C)
.
-16
vo
50
100
150
200
250
300
350
400
TIME (hr)
9.22
agreement among the reentry thermocouples at 1425°C. After 200 hr at
1425°C, the thermocouples in the various positions did not show any
drift, The Pt9Rn6/ PtroRhzo gradient-positioned thermocouple had
drifted about -0°C, whereas in Test I at 1450°C, this type thermocouple
had drifted -15°C in 200 hr. The slightly lower test temperature may
explain this difference. Thus, the other results of Test III at 1425°C
confirm the results of Test I at 1450°C. The repeat test has thus showa
a lack of thermal emf drift for these thermocouples at high temperatures
in high vacuum.
POSTTEST EXAMINATION AND DISCUSSION OF RESULTS
After Test I was concluded, the test thermocouples were removed and
a: limited examination of the thermoelements made. There were no striking
changes visible at 100x (binocular) for the WRey/W24Re 26 or the W/W, 2Re 26
thermocouples. The PtooRhio/ Pt thermocouples were thermally etched for
5 in. from the hot junction, and near the hot junction, individual grains
nded across the wire. The surfaces of these large grains showed a
considerable amount of thermal faceting. The Pt 9 Rh6/ PtroRbzo reentry
thermocouples were similar in appearance to the PtgoRh10/Pt thermocouples.
The gradient-tested Pt 9 Rh6/ PtoRn3o thermocouple differed in appearance
only in the region that had been in contact with the niobium block. The
surface of the wires was very mottled and rough in this vicinity. The
wires of the noble thermoelements were easy to fracture just below the
hot junction bead; this was probably related to the excessive grain
growth.
These casual observations do not offer any strong evidence for
explaining the drift results. However, since drift was observed in
only a few cases, striking visual changes were not expected. For the
non-drifting thermocouples, little (other than thermal etching) appears
to have occurred. Since the hot junctions of these thermocouples were
immersed in an isothermal zone, any changes caused by this etching were
not sufficient to generate composition differences in the temperature
gradient portion to cause drift of thermal emf. Thus, the results
indicate that, if the hot junction is placed in a moderately good 180-
thermal zone, then none of the types of thermocouples tested will
drift significantly at high vacuums and high temperatures.
---- .........
...
.. ......
The gradient-positioned Ptg2Rh6/Pty oRh30 thermocouple did drift at
1450°C and the thermoelements did have a significantly different surface
appearance near the hot junction. One reasonable explanation of this
performance is that in the hot junction region (which was in a steep
temperature gradient) a compositional change did occur and this inhomo-
geneity caused the observed drift. The surface appearance of the wires
appears to support this viewpoint. Figure 9.7 is a photomicrograph of
the PtroRh3o wire that contacted the niobium block. This structure is
not typical for this alloy but shows a second phase present in this
region. This phase is due to the aiobium.
9.23

UNCLASSIFIEDS
Y-56678
.."
.
enerowane
Fig. 9.7. Photomicrograph of Pty oRh30 Wire Which Contacted the
Niobium Block in Test I. 500X.
The thermal emf of the tantalum- and niobium-sheathed, MgO-insulated
Pt 94 Rh6/ Pt thermocouples drifted negatively at 1200°C: Figure 9.8 is a
photomicrograph of one such thermocouple which was niobium sheathed. It
is apparent that a reaction occurred and penetrated the thermoelements.
This reaction, whose character is not knowa but which must be associat
with the MgO, apparently caused the negative drift of these thermocouples.
Whether this is due to Mgo, per se, or to impurities in the MgO is not
apparent at this time.
CONCLUSIONS
Tests at 1200 to 1450°C for times up to 1000 hr at pressures between
106 and 108 torr have shown that the thermal emfs for platinum-rhodium-
and tungsten-rhenium-base thermoelements did not drift under these condi-
tions. Commercially available thermocouples of the type Pt 9 ORE 10/Pt,
Pt94 Rh6/ Ptry Rhzo, W/W24Re 26, and Wo 5 Res/Wy Re 26 were shown to be stable
within 110°C for the test conditions. Wire size and alloy content dia
9.24

· UNCL ASSIFIED
Y.49667
(20)
UNCLASSIFIED
Y-49669


CP
Ex
t
.
x ...
Fig. 9.8. (a) Photomicrograph of Niobium-Sheathed, MgO-Insulated
PtooRho/ Pt Thermocouple After 143 hr at 1200°C and 106 torr. 100x.
(b) Platinum wire from 8(a). 500x.
9.25
OINL AIC -OSTICIA
not affect the stability in these tests. Posttest examinations revealed
only minor surface appearance changes occurred for the stable thermo-
couples.
One test at 1450°C did show that drift of thermal emf could be
expected in Pto_Rh6/ Pty oRh3o thermocouples if the hot junction is
joined to niobium and exposed to a severe temperature gradient.
This is apparently due to compositional inhomogeneities due to
diffusion of niobium into the hot junction. Severe thermal emf
changes were observed at 1200°C in tantalum- and niobium-sheathed,
MgO-insulated Pt9oRh, o/ Pt thermocouples; this 18 apparently caused
by a reaction between the thermoelements and MgO.
ORNI - MEC - OFFICIAL

9.25
ORHI - AIC - OPTIC
not affect the stability in these tests. Posttest examinations revealed
only minor surface appearance changes occurred for the stable thermo-
couples.
One test at 1450°C did show that drift of thermal emf could be
expected in PtoRho/ Ptry oRh30 thermocouples if the hot junction is
joined to niobium and exposed to a severe temperature gradient.
This is apparently due to compositional inhomogeneities due to
diffusion of niobium into the hot junction. Severe thermal emf
changes were observed at 1200°C in tantalum- and niobium-sheathed,
MgO-insulated PtooRho/Pt thermocouples; this is apparently caused
by a reaction between the thermoelements and Mgo.
REFERENCES
I.
B. E. Walker, C. T. Ewing, and R. R. Miller, Thermoelectric Instability
of Some Noble Metal Thermocouples at High Temperatures,
NRL Report 5792 (June 29, 1962).
B. E. Walker, C. T. Ewing, and R. R. Miller, "Thermoelectric Insta-
bility of Some Noble Metal Thermocouples at High Temperatures,"
Rev. Sci. Instr. 33(10), 1029–1040 (1962).
3.
B. F. Hall, Jr., and N. F. Spooner, "Application and Performance Data
Tor Tungsten-Rhenium Alloy Thermocouples," Society of Automotive
Engineers Preprint 750C, Presented at the National Aeronautic and
Space Engineering and Manufacturing Meeting, Los Angeles, California
(Sept. 23-27, 1963).
R. J. Freeman, "Thermoelectric Stability Platinum vs Platinum-Rhodium
Thermocouples," pp. 201-220 in Temperature - Its Measurement and
Control in Science and Industry, vol 3, Part 2, Reinhold Publishing
Corp., New York (1962).
5.
J. A. Mcgurty and W. C. Kuhlman, "Tungsten/Tungsten-Rhenium Thermo-
couple Research and Development, General Electric Co.; Presented
at the SAE National Aeronautic Meeting and Production Engineering
Forum, New York (April 6, 1962).
6.
W. C. Kuhlman, "Status Report on the Investigation of Thermocouple
Materials for Use at Temperatures above 4500°F," TM 63-9-6, Advanced
Technology Services, General Electric Co.; Presented at the SAE
National Aeronautics and Space Engineering and Manufacturing Meeting
Los Angeles, California (Sept. 23-27, 1963).
7.
S. Fanciullo, Thermocouple Development Lithium-cooled Reactor Experi-
ment, PWAC-422 (March 5, 1964).
ORNI - AIC-OISICIAL
9.26
8.
R. I. Bennett, H. L. Memphill, W. T. Rainey, Jr., and
G. W. Keilholtz, Stability of Thermoelectric Materials in a Helium-
Graphite Environment, ORNL-TM-746 (Jan. 10, 1964).
9.
W. E. Winsche and F. T. Miles, Progress Report Nuclear Engineering
Department, May 1 to August 31, 1962, BNL 759(5-62).
10.
V. W. Obrovski and W. Prinz, "Newly Determined Fundamental Values
for the Thermocouplé Pt 30% Rh-Pt 6% Rh," Arch. Eisenhuttenw.
33(1), IL (1962).
11.
D. I. Finch, "Precision Temperature Measurements with Thermocouples,"
pp. D-1-30 in Proceedings of the Symposium on Precision Electrical
Measurements, Leeds & Northrup Company, Philadelphia, 1963.
12. J. F. Potts, Jr., and D. L. McElroy, Thermocouple Research to
1000°C – Final Report, November 1, 1957, through June 30, 1959,
ORRI-2773 (Jan. ló, 1961).
13. H. Shenker, J. I. Lauritzen, Jr., R. J. Corruccini, and
S. T. Lonberger, "Reference Tables for Thermocouples," Natl. Bur.
Sta. (U.S.) Circ. No. 561 (1955).
Morograph 40 (March 1, 1962).
15. "Temperature-Millivolt Equivalent for W-5Re/W-26Re Thermocouples,"
acopted lov. 23, 1962. Hoskins Manufacturing Company Publication.
ló. "Tingsten-Rhenium Thermocouple Alloys, Temperature-Millivolt Equiv-
alent for W/W26Re Thermocouples," Adopted Nov. 23, 1962. Hoskins
Harufacturing Company Publication.
- OFFICIAL
...
.
.
1.
-
DATE FILMED
5 / 13 /65








*
..*
5
'
.
1
Y
HT
.
:
T
.
2
F
-
I
..
..
LEGAL NOTICE

.
.
....
........
This report was prepared as an account of Government sponsored work. Neither the United
States, nor the Commission, nor any person acting on behalf of the Commission:
A. Makes any warranty or representation, expressed or implied, with respect to the accu-
racy, completeness, or usefulness of the information contained 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. Assumes any liabilities with respect to the use of, or for damages resulting 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 em-
ployee or contractor of the Commission, or employee of such contractor, to the extent that
such employee or contractor of the Commission, or employee of such contractor prepares,
disseminates, or provides access to, any information pursuant to his employment or contract
with the Commission, or his employment with such contractor.
..........
.
.
.
*
-
.
=
-
::"
A=
U
'.
'
L
.
T
.!
h
.
.
C
1
-
:
4
,
1
-
,
:,
.
.
.
+
"
=
A
-!.
END
.
:
:
:
.
*
".
-
Hii
.
.
.
.
- ..
**** um perumusawirioms