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ORNL-2348.txt
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'l:R';i;ll]'l'hl'[l"llfl"fi',;,filfi'j']J'.l'\.iil":ll"|i||.'i|l?ih'.ili"'|
ORNL-2348
Metallurgy and Ceramics
TID-4500 (13th ed., Rev.)
February 15, 1958
aa, )33
COMPONENTS OF THE FUSED-SALT AND SODIUM CIRCUITS
OF THE
AIRCRAFT REACTOR EXPERIMENT
CENTRAL RESEARCH LIBRARY
DOCUMENT COLLECTION
LIBRARY LOAN COPY
DO NOT TRANSFER TO ANOTHER PERSON
If you wish someone else to see this
document, send in name with document
and the library will orrange o loan.
OAK RIDGE NATIONAL LABORATORY
operated by
UNION CARBIDE CORPORATION
for the
U.S. ATOMIC ENERGY COMMISSION
Contract No. W-7405-eng-26
REACTOR PROJECTS DIVISION
COMPONENTS OF THE FUSED-SALT AND SODIUM CIRCUITS
OF THE
AIRCRAFT REACTOR EXPERIMENT
H. W. Savage
G. D. Whitman
W. G. Cobb
W. B. McDonald
DATE ISSUED
OAK RIDGE NATIONAL LABORATORY
Ook Ridge, Tennessee
operated by
UNION CARBIDE CORPORATION
for the
U.S. ATOMIC ENERGY COMMISSION
ORNL-2348
MARTiNHMARIETTA EiiR||G|V SYSTEMS |LIBi|A|RIES
3 4456 03BLLY?7? 7
CONTENTS
AD SIFACT ettt et ettt et et e ettt e et et e et et ater et e n e et ense st ersans 1
IETOAUCTION Lottt et b et e e e e et e ee et e et ee et e e e s e e ereeteoteneetesaearense e seresaass 1
Engineering Development for the ARE ... et 1
Forced-Circulation Test LooOps ..ottt e et e et ae e eneoes 3
Mixing of Fuel and SOdiUm ....o..ooiiiiiicc et ettt e 3
BeO-Sodium Compatibility .....cccoooiiiiiiiiie e et 8
REAEIOE COTE oottt ettt e ettt oot ettt et et eee e e e ee e e e e e s e et e et s e et e e e et raneeens 8
Fill and Drain EQUIPMENT ..ot ettt e e ee et et e et ee e st eee e e eeenaans 8
Fill and Drain TanKs ....ooooio e e ettt et er e et e e et et et eeeeeae e, 8
Fuel ENFiChmMent oottt e te et ee et s e ettt e e eeeee e 8
Piping and Leak Detection ..ottt sttt ettt e 11
P i e ettt e e s ere e et e er et b et eaereesae e crereer e 11
ek D et O ION ittt ettt ettt e, 12
Preheaters and InsUlation ..ottt 13
Heat DUMP Sy Stems ..o ittt ettt ettt e bs et e e bt sttt es st eeeeees e 13
Fuel Heat DUMP Sy Stem ..o e e e ettt ee e e e eae s eae e 13
Sodium Heat DUmp System ..ottt ettt 13
Heat ExXchanger Test .ot e et e e eeeaeane e 15
High-Temperature Isolation Valves ...t 19
Sodium Oxide Cold Traps oo ettt e e e e ete et et e et et e e 19
INErt GOS8 Sy STEMS ..ttt ittt ettt et sttt e b b re et e e et b er b ssest e e te ke eatt s e et s raabessenbere et ereea b s antesseas oo 20
2T TGP S s b s 20
P UMD S et e ettt bbb st er e et e s et et st eee e 21
Packed Seals ... e e et sttt et e 21
Rotary Gas-to-Lubricant Seals ... e 23
Centrifugal Sump Pumps oo e ettt ae e 23
PUMP D SigN .. i et bbbt st ne 25
PUMP AUXTTIGRIES oottt h et b e e e et e et e st e e bt e e eb e ettt aeas e enn e s e nbeeaabeantesaensane e 34
P UMD DIIVES oottt e et e e et e e eat b ete e e ae s es st et e eee e st e e e ans eeesae ek s aan snsen e e enne e entneeneeenns 34
LU Cation Sy SEEmS L it ettt ettt e sttt et aen e e et n et ean 34
High-Temperature INstrument@tion ...........cooooiiiiiiiioiiieiie ettt ettt et e er e et ae s e 34
T emperature MeasUremMeEnt ..ot et reer e s ettt et ee e e e e e e et e e e ettt et e anate et e e 34
PressUre MeasUrEemENnT ... . ettt e et ettt et r et a et e reraes 34
it
F oW MO SUICMENT ooeeeereeee oot e e e oo e eeeee e e e e e s e ee e ee e e e e ee e mae e e ae e ae e e e m e aeee et ettt A bbe bbb sb bbb s raaesneebsrnrnrenn s 34
L eVel MEASUIPEMENT oottt e e e e e e e e e et e et e e e e esbbe aa e e eabbe b e e e s ernb e an s renae e e an s 36
Component Installation ...ttt bbb 36
SUMMIGIY et ciete ittt cteet et et e ekt et e e ese et e et e e ese £ eteems e b e et et et e ebeshee et rones e e ead e R e s s saen Ao es e e R e a e e re e a e e s e e s eeae e e ab et sebe s 36
ACKNOWIEAGMENT 1ottt ettt bR a e e et 38
COMPONENTS OF THE FUSED-SALT AND SODIUM CIRCUITS OF THE AIRCRAFT
REACTOR EXPERIMENT
H. W. Savage
G. D. Whitman
W. G. Cobb
W. B. McDonald
ABSTRACT
The Aircraft Reactor Experiment (ARE) successfully demonstrated the feasibility of generating
heat by fission in a fused-fluoride circulating fuel. Most of the heat was removed from the reactor
by the fused fluoride at 1580°F.
Sodium at 1350°F was used to cool the BeO moderator. With
minor exceptions all the components proved to be adequate.,
The development of components and fabrication techniques for this reactor consumed a four-
year period, during which time the technology for handling high-temperature fluids was extended
to equipment operable above 1500°F. The methods used for determining compatibility of materials
under static and dynamic conditions, standards for materials, ond techniques for welding, fabri-
cation, and assembly and the design criteria for pumps, seals, valves, heat exchangers, cold
traps, expansion tanks, instrumentation, preheating devices, insulation, etc., are described,
INTRODUCTION
A high-temperature Aircraft Reactor Experiment
(ARE) generated heat by fission of U233 in a
fused salt composed of UZ235F , ZrF ., and NaF
for a period of 221 hr, ending on November 12,
1954. As shown in Fig. 1, the maximum equilibrium
temperature of the saltwas 1580°F, with @ maximum
temperature gradient of 380°F. About 25% of the
heat was transferred to sodium, which was circu-
lated at a maximum equilibrium temperature of
1350°F with @ maximum temperature gradient of
120°F. The heat was then transferred from both
salt and sodium to helium in separate closed
circuits and was finally transferred to water. The
maximum heat power generated was 2500 kw, and
the total amount of energy was 96,000 kwhr. The
entire operation was performed in remotely
controlled equipment in three concrete enclosed
pifs.]
Prior to the nuclear power operation the systems
and components were checked out? by operating
the fused-salt circuit for a period of 388 hr at
temperatures above 1200°F and the sodium circuit
for a period of 561 hr at temperatures above 600°F.
]E. S« Bettis et al., **The Aircraft Reactor Experi-
ment ~ Design and Construction,’
Eng. 2, 804-825 (1957).
2E, S, Bettis et als, **The Aircraft Reactor Experiment —
Operation,’t Nuclear Sci. and FEng. 2, 841-853 (1957).
Nuclear Sci. and
The ARE than four years of
research and development and is believed to be
the first reactor to generate nuclear power above
1500°F.
It is presumed that the reader is familiar with
the basic concepts of the design, the physics, the
chemistry, and the metallurgy which led to this
required more
particular reactor system, since these topics have
been covered in other reports,1+3=6 as has the
operation? of the In the
following discussion emphasis is placed on the
principal components of the reactor experiment
and on the solution of some of the important de-
reactor experiment.
velopment problems involved.
ENGINEERING DEVELOPMENT FOR THE ARE
Figure 2 shows the principal phases of engi-
neering development. Since the original concept
of the ARE was that of a solid-fuel-pin, beryllium
oxide—moderated, sodium-cooled reactor, the first
3A. M. Weinberg et al., ‘*Molten Fluorides as Power
Reactor Fuels,’” Molten Fluoride Reactors, ORNL
CF+57-6-69.
W, K. Ergen et als, **The Aircraft Reactor Experi-
ment — Physics,’" Nuclear Sci. and Eng. 2, 826-840
(1957).
SW. R. Grimes et als, *"Chemical Aspects of Molten
Fluoride Reactors'' (to be published).
bW, D. Manly et als, ORNL-2349 (Sept. 17, 1957)
(classified).
SCDIUM
CIRCULATED AT 42D gpm
HELIUM
ELOWER
ABSORBER RCD
HEAT £EXCHANGER
Fig. 1.
UNCLASSIFIED
ORKNL-LR-DWG 282t6
1950 19951 1952 1953 1954
. e , R -
BASIC 1500°F SCDIUM HANDLING h ‘
BASIC 1500°F MOLTEN FLUCRIDE
SALT HANDLING e
CORROSION STUDIES h
MECHANICAL PUMPS C e e
ARE COMPONENT DEVELOPMENT | | ..
\
_ - o i o
ARE SHAKEDOWN AND OPERATION | ol
— | e e
EXPLORATQORY MAJGR DEVELOPMENT - IMPROVEMENTS
OR SHAKEDOWN: PEQIOD; 7
Fig. 2. ARE Development Phases.
year was devoted to studies of the corrosion,
dynamic, and engineering problems of handling
sodium at 1500°F. In 1951 the concept was
changed to that of fuel elements containing
stagnant molten salt, and shortly thereafter to
that of a reactor containing no fuel elements but
circulating a fused fuel salt.! The sodium circuits
were retained to cool the beryllium oxide moderator
UNCLASSIFIED
ORNL-LR-DWG 14562AR
FLUQORIDE
CIRCULATED AT 46 gpm
HE
BLOW
s
HEAT EXCHANGLA
m ‘
T : +
5
M
pral
S
Schematic Diagram of the ARE.
and the reactor pressure vessel. The second year
was devoted primarily to determining compatible
structural materials and fused fluoride compositions
and to investigating the engineering and fabrication
problems involved in handling fused fivorides at
temperatures between the melting temperature,
~950°F, and the proposedreactor operating temper-
ature of 1500°F.
Development of pumps, heat exchangers, valves,
pressure-sensing instruments, cold traps, and
other components began in late 1951 and continued
to the summer of 1954, culminating with the
defivery of pumps and other components to the
experimental reactor facility, Many of the tech-
niques developed were extrapolations from data
already available from the extensive experience in
the temperature range of 800to 1000°F with sodium
and sodium-potassium alloy at Argonne National
Laboratory, Knolls Atomic Power Laboratory,
and Mine Safety Appliances Co. Had not this
experience been available, the development period
would certainly have been much longer.
Design of the reactor, development of pumps,
valves, heat exchangers, and other components,and
containment of sodium and molten sait at 1500°F
presented new and perhaps fascinating problems.
Equally challenging were the problems concerning
fabrication, construction, preheating, instru-
mentation, and insulation of reliable leak-tight
high-temperature circuits made of Inconel. Much
of the technology of these developments has been
d.7=9 We wish also to acknowledge the
important contributions to the technology by
hundreds of engineers and scientists, and regret
that it is impossible to give them individual
recognition.
reporte
Although some of the avenues investigated in
developing components were not fruitful, many of
the solutions used in the ARE have become
accepted practice. Among these are the following:
1. use of fire-resistant insulation,
2. use of all-welded construction,
3. standardization of specifications for quality
and inspection of reactor and heat transfer
circuit materials,
4. standardization of welding procedures,
5. standardization of inspection specifications
for assembled components as to fabrication and
leak-tightness,
6. development of high-temperature instrumentation
to include pressure, temperature, flow, and
liquid level measurement,
7. development of the high-temperature sump-type
centrifugal pump — now in routine use in the
laboratory.
Completely adequate designs were not available
for valve seats, bearings in sodium or salt, pump
operable against the liquid, or pumps
in circuits with more than one free
seals
operating
surface. Mechanical valves were used in the high-
temperature reactor circuits, but because of their
dubious qualities provisions were made for freeze
valves and frangible diaphragms. Overhung shafts
were used in the pumps to avoid bearings and
seals in the liquid, and the pump tank (or sump)
was enlarged sufficiently to become the expansion
tank of the system, thereby preventing multiple
free liquid surfaces.
During pump development a number of pumps for
sodium were operated successfully with frozen
sodium shaft seals. On the other hand, frozen or
packed seals for fluorides invariably resulted in
excessive wear and failure.
Fabrication of reliable leak-tight high-temper-
ature circuitry required the use of all-welded
7C. B. Jackson (Editor-in-chief),
Handbook, Sodium-NaK Supplement, 3d ed,,
Washington, 1955.
8w. B. Cottrell and L. Ae. Mann, Sodium Plumbing,
A Review of the Unclassified Research and Technology
Involying Sodium at the Oak Ridge National Laboratory,
ORNL-1688 (Aug. 14, 1953).
IA. M. Weinberg, **The Nature of Reactor Technology
and Reactor Development,!’ Molten Fluoride Reactors,
CRNL CF-57-6-69.
Ligquid Meials
GPOC,
stress-free structures, use of seamless tubing and
pipe, and adherence to carefully defined welding
and inspection techniques. All material is 100%
dye-checked, is vltrasonically and radiographically
inspected for defects before use, and is rejected
when there are any observable defects. Materials,
labeled to
minimize errors in selection; analyses are per-
formed to avoid mislabeling; and all critical welds
radiographed before ac-
including weld rod, are carefully
are dye-checked and
ceptance. With these controls, leaks are rare,
unless the part involved has been severely over-
stressed.
FORCED-CIRCULATION TEST LOOPS
Much of the technology and component develop-
ment was accomplished in forced-circulation loops.
These loops, which were also used to determine
corrosion rates,® were of two types. Figure 3
shows a typical sodium test loop which uses an
electromagnetic pump. Figure 4 shows a salt test
loop which employs a down-flow centrifugal sump
pump capable of 1600°F operation. This pump has
been improved since its development in 1951 and is
still used routinely in the laboratory. It provided
some basic ideas for reactor pumps subsequently
developed. It was partly on the basis of corrosion
data obtained from such loops that Inconel and a
composition®:® were chosen for the
reactor. These loops established that use of a
single alloy in a high-temperature system would
minimize corrosion and mass transfer.® Inconel
was chosen for both the sodium and the fuel
circuits, although type 316 stainless steel is more
resistant to attack by sodium, in order to avoid
fuel salt
duplex-material construction for reactor fuel tubes
(see Fig. 5). (Mass transfer in sodium-Inconel
systems is considerably higher than in sodium-—
stainless steel systems, but was not expected to
be excessive in the periods of operation anticipated
for the reactor experiment.)
Screening tests were conducted with hundreds
of natural-convection loops, Fig. 6, to eliminate
structural materials and fused
6
fess desirable
fluoride compositions.
Mixing of Fuel and Sodium
Other determined the effects of
sudden
could have occurred if one of the reactor fuel tubes
experiments
mixing of fuel salt and sodium, which
had cracked or ruptured during operation. The
reaction was known to be exothermic. Insoluble
reaction products were frequently found in sufficient
Fig. 3. Sodium Corrosion Test Loop.
! UNCL ASSIFIED
PHOTO 22434
SAFETY
ALLES
YLST 8¢ gy
1% "f-!5 4?5:
Fig. 4. Fused=Fluoride Corrosion Test Loop Employing a Down-Flow Centrifugal Sump Pump (See Fig. 22 for Cross Section of Similar Pump).
UNCLASSIFIED
DWG. 16336
REGULATING ROD
ASSEMBLY
SAFETY ROD
GUIDE SLEEVE
——TUBE EXTENSION
THERMAL SHIELD CAP
_—— THERMAL SHIELD TOP
SAFETY ROD ASSEMBLY FUEL INLET MANIFOLD
THERMOCOUPLE
LAYOUT
TOP HEADER
CORE ASSEMBLY TOP TUBE SHEET
HEATERS
REFLECTOR COOLANT
TUBES
8eC MODERATOR
AND REFLECTOR
FUEL TUBES
THERMAL SHIELD
ASSEMBLY
PRESSURE SHELL
TUBE
SHEET
STUD
SUPPORT ASSEMBLY
BOTTOM HEADER
FUEL OUTLET
MANIFOLD
e e e 8O Y2 i, REF.
|
THERMAL SHIELD
THERMAL SHIELD CAP BOTTOM
e 235%g in. REF. —
\SUPPORT ASSEMBLY
02 4 6 i &
ELIUM MANIFOLD s;ghaéuaggzfisde
SCALE IN INCHES
Fig. 5. The Reactor {(Elevation Section).
UNCLASSIFIED |
PHOTO 22432
Fig. 6. Natural-Convection Corrosion Test Loops.
quantity to stop circulation. While the pressure
rise observed was small, local temperature
transients of 200 to 300°F were observed.
BeO-Sodium Compatibility
Specimens of BeO were suspended in sodium
and examined for attack. Little or no beryllium
was found in the sodium, but porosity of the BeO
was clearly evident, since the specimens exuded
sodium for long periods after they were removed.
Visually, the BeO showed no damage of conse-
quence at any temperature of interest in the reactor.
REACTOR CORE!
In the original concept the reactor core provided
sixty=six ]]/4-in.'rubes in parallel vertically through
holes in hexagonal beryllium oxide bricks and
seventy-nine ]/2-in. tubes in the outer reflector
section of the core, When the shift was made to a
circulating fused salt fuel, the higher viscosity and
reduced over-all flow rate required made it essential
to reduce the number of parallel paths through the
reactor in order to maintain Reynolds numbers in
the turbulent range.! Consequently, the 66 tubes
arranged in six parallel routes, each
comprising a serpentine (see Fig. 5) of 11 tubes
in series connected by U-bends at the top and
bottom. This arrangement introduced the question
of whether the core could be filled without first
being evacuated and also made complete draining
The outer sodium tubes
were
of the core impossible.
were left unchanged.
A full-size core, Fig. 7, was mocked up
with glass and metal tubing, and its hydraulic
characteristics were studied with water-glycerin
solutions for viscosity effects and with tetra-
bromoethane (manometer fluid) for density and
viscosity effects. It was found that complete
filling of the core could not be accomplished by
pressurization of the fluid from the fill tanks,
because gas became trapped in the multiple
vertical rises of each parallel circuit through the
reactor core; nor was it possible to expel this gas
and establish full flow within the maximum head
provided by the fuel pump. With a partial vacuum
above 400 mm Hg, filling was certain and flow
could be established in each of the six parallel
paths without difficulty. Full blowdown draining
was impossible because liquid expulsion ceased
as soon as one circuit was opened to the gas flow;
however, the liquid could be forced or chased out
with another liquid. As the result of these experi-
ments, the reactor was filled under vacuum, and
spent fuel was displaced with barren salt, followed
by several flushings.
FILL AND DRAIN EQUIPMENT
Fill and Drain Tanks
Tanks were attached to both the sodium and the
salt circuits to receive the initial charges of
sodium and barren salt. With the use of helium
pressurization the materials were transferred from
the tanks into the reactor Once the
circuits filled, the interconnection was
closed by a mechanical valve and the liquid could
not be drained back. (As explained elsewhere,?
the sodium valves did not seal tightly, but this
situation was tolerated.)
circuits,
were
There were three fill tanks for sodium and two
for barren salt, all located in a tank pit as shown
in Fig., 8. In addition, a hot-fuel dump tank con-
taining 89 vertical through tubes for convection
cooling with helium in the pit was reserved for
the spent fuel. Each tank was equipped with
external electrical heaters and thermocouples and
was of welded construction. Valved connections
to a supply of spectroscopically pure helium
(<10 ppm 02, —60°F dew point) permitted the
fluids to be blanketed at any desired pressure and
prevented exposure of them to air or water vapor,
Fuel Enrichment2:4,5
The approximate quantity of U235 needed in the
fused fluoride mixture for the reactor to reach
criticality was known from an earlier, low-temper-
ature critical experiment. Consequently, the first
phase of nuclear operation of the ARE was a high-
temperature critical experiment.24 The initial
charge of fused fluorides to the reactor was a
highly purified® 50-50 mole % mixture of NaF
and ZrF,. To this a mixture of 33% mole %
U235F4, 66%_13 mole % NaF was added?:4¢5 in
known increments wuntil criticality, and subse-
quently the desired excess reactivity, was
reached. At the completion of this operation the
reactor fuel was approximately 6.18 mole % U235F4,
40.73 mole % ZrF ,, and 53.09 mole % NaF, which
had a melting temperature of 1000°F.
The highly enriched fuel was stored in several
containers under helium, and was batched down to
smaller containers in quantities ranging from 2 to
33 |Ib. The smaller containers were connected
successively to the fuel circuit as shown in Fig. 9,
and 23 transfers were made in order to fully enrich
the fuel. A Z-in.-dio tube, heated by a current
"UNCL ASSIFIED
PHOTO 21918
Fig. 7. Full-Scale Reactor Core Mockup.
0l
//SOD\UM FILL AND
: DUMP TANK
SODIUM FILL AND
DUMP TANK NG.5
HOT FUEL DUMP TANK
. ' o — i
SODIUM FiLL AND DUMP TANK NC 4 - \
TANK NO. 3 (NOT USED)—
Fig. 8. ARE Fill and Drain Tanks.
UNCLASSIFIED
ORNL-LR-DWG 6222R
UNCLASSIFIED
TO HELIUM SUPPLY ORNL-LR-0OWG 6395
| VENT
TO HELIUM SUPPLY
TO VACUUM
PUMP
VENT
"N ELECTRICAL CONNECTIONS
1 FOR RESISTANCE HEATING
1
E E/S#’«TCH Can
. 5> |
E 1 g TRANSFER POT
MM
L—O\./'EJ\I
= TRANSFER LINE
ELECTRIC HEATERS
g{TO HELIUM SUPPLY
FLOOR LEVEL AUXILIARY
|
|
;
|
g
L —><—— VENT
5
= VENT
FUEL PUMP
SAMPLING LINE SUMP
DISCHARGE
| - SUCTION
|
\
|
. Fig. 9. Equipment for Addition of Fuel Concentrate to Fuel System.
passed through it, led to the sump of the fuel UNCLASSIFIED
pump, and injections were made with the pump in ORNL-LR-DWG 28217
operation and the fused salt circulating. The
high melting temperature of the enriched salt
(1185°F), unanticipated cold spots in the transfer
tube, and leaks in tube fittings used in the transfer 100 deg
line made enriched-fue! transfer more tedious than
had been expected. The exact amount transferred
was determined after completion of the operation
by comparing differences in weights of the con- W /////@1 fi&\ j&
tainers emptied. A-J L
g in 1/46 in.
PIPING AND LEAK DETECTION 1 .
/16—|n.MAX.
Piping
All the reactor high-temperature piping was
Y
seamless sched-40 inconel pipe with full-penetration V /%// /m\\k N
welds, Fig. 10, at joints. The pipe was installed
between anchor points, prestressed sufficiently
- at room temperature to be approximately stress-free Vg —in. MAX.
at operating temperature. All piping connections