ORNL-TM-0528.txt

operated by
UNION CARBIDE CORPORATION
for the

U.S. ATOMIC ENERGY COMMISSION

   
  

DESIGN AND OPERATION OF FORCED~-CIRCULATION

CORROSION TESTING LOOPS WITH MOLTEN SALT

J. L. Crowley
W. B. McDonald
D. L. Clark

DA

| Facsimile Price 3

    
  
  
  

  

Microfilm Price $

Available from the .
Office of Technical Services
Department of Commerce

Washington 25, D- C.

NOTICE

This document contains information of a preliminary nature and was prepared
primarily for internal use at the Ook Ridge National Laboratory. It is subject
to revision or correction and therefore does not represent a final report., The
information is not to be abstracted, reprinted or otherwise given public dis-

semination without the approval of the ORNL patent branch, Legal and Infor-
mation Control Department.

OAK RIDGE NATIONAL LABORATORY

 

UNION
CARBIDE

 

ORNL- TM- 528

ws\”%_%
he

 

 

 

 

 

LEGAL NOTICE

This report was prepared as an account of Government sponsored work. Neither the United Stotes,

nor the Commission, nor any person acting on bahalf of the Commission:

A. Makes any warranty or representation, expressed or implied, with respect to the accuracy,
completeness, or usefulness of the information contained in this report, ot 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 respact 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 cbove, ‘‘person acting on behalf of the Commission’ includes any employee or

confractor of the Commission, or employee of such centractor, to the extent that such employee

or contractor of the Commission, or employee of such contractor prepares, disseminates, or
provides access to, any information pursuont to his employment or contract with the Commission,

or his employment with such contractor,

 

 

 

 

 
ORNL-TM-528

Contract No. W-7405-eng-26

Reactor Division

DESIGN AND OPERATION OF FORCED-CIRCULATION
CORROSION TESTING LOOPS WITH MOLTEN SALT

J. L. Crowley W. B. McDonald
D. L. Clark

Date Issued

MAY -1 1963

 

OAK RIDGE NATTONAL LABORATORY
Oak Ridge, Tennessee
operated by
UNION CARBIDE CCORPORATION
for the
U.5. ATOMIC ENERGY COMMISSION
iii

CONTENTS

Abstract

Introduction

Description of Test Loop and Auxiliary Equipment
Alarm and Automatic-Action Controls

Operation and Maintenance of a Test Loop

Summary

Acknowledgments

15
17
21

21
DESIGN AND OPERATION OF FORCED-CIRCULATION
CORROSION TESTING LOCPS WITH MOLTEN SALT

J. L. Crowley W. B. McDonald
D. L. Clark

Abstract

Standardized test facilities were developed and oper-
ated for investigating the compatibility of structural
materials and flowing molten fluoride salts. The standard
loop accommodates various combinations of materials, fluids,
flow rates, and temperature differentials and permits
fabrication of components in sufficient quantity for cost
reduction. The test loop consists of a pump, two heated
sections, a cooled section, & drain tank, and a frozen-
plug-type valve. Automatic controls and equipment were
developed to prevent solidification of the salt mixtures
(m.p., 800 to 1100°F) in the event of a loss of power.
Most test loops are fabricated of 0.5-in.-o0.d., 0.045-in.-
wall tubing, and they operate with a temperature differ-
ential of up to ZOOOF, a maximum wall temperature in the
range 1200 to 1500°F, and a salt flow rate of up to 3 gpm.
Twenty-five test loops have been operated for an accumu-
lated operating time of 290,000 hr. Individual loops have
been operated continuously for more than one year.

Introduction

Mixtures of molten fluoride salts have been investigated extensively
for gpplication in reactor systems as fluid fuels or as heat transfer
media. The compatibility of a particular salt mixture with a proposed
container alloy is determined, in part, by tests with thermal-convection
loops,t and the most promising combinations of salt mixtures and
structural material are tThen studied in forced-circulation corrosion
test loops. These loops simulate all essential reactor operating con-
ditions except radiation.® The test stands and loops have been standard-
ized to permit ready replacement and to minimize fabrication costs and
installation time.

Many mixturss of molten salts have been tested. The basic con-

stituents of these have been the fluorides of sodium, lithium, beryllium,
zirconium, thorium, ard uranium in various proportiocns that give melting
temperatures generally falling in the 800 to 1100°F range.” Viscosity
and density vary with each mixture. The viscosity increases with the

ount of berylliuvm present and the density ircreszses with the amount of
hegvy elements preseunt. 2 typical salt mixture hes & viscosity of 10
centivoise and z specific gravity of 2.4 af iicn’ Tre salt mixtures
contalaing beryllium reguaire stringent safety precautions to prevent ex-
posure of personnel to this toxic material.

To predict accurately corrosion rates for power reactors, the tests
must necessarily be of long-term duration. The test stand control
system was therefore designed not only to maintain the necessary test
corditions for long periods of operation but alsc to provide automatic
pretection against sclidificagtion of the salt in the systam. Since
melting of the salt imposes severe stresses on the container wall, re-

meiving after solidification might cause premature failure of the loop.

Degceription of Test Loop and Auxiliary Egulpmen®

 

The test lcop is illustrated in Fig. 1. The loor consists of a
pump, two heated sections, a cooled section, a dresin tazk, and a frozen-
plug-type valve. Atl wetited parts of the loop are fabricated of the
alloy being studied. Loop tubing size is selected to provide the proper
cnditions for electrical-resistance heating and to give a pressure drop
at design flov that is consistent with the pump capabiliity. A flow

the molten-selt circuit and the auxilisry controls for the
inert cover gas end utiliities is shown in Fig. 2.

A stendard loop supported by its moblile dolly 1s pictured in
Fig. 3. This stancard loop was developed from experience gained in
rany tests to accommodate the various combinations of materials, fluids,
Tlow rates, and temperzoure gradients desired. Such standardization
has permitted fabrication of components in quantity for both cost re-
duction and ease of gggembly. The interchangeability of the test loops
and stands allows the faprication of standby test loop assemblies for
guick replacement with s minimum of down time. For most tests, 0.5-in.-

0.d., 0.045-in.-wall tubing has been focund to e suitable.
Fig. 1.

1O kva POWER SUPPLY

   
 
    
  

1600-amp BREAKER

10 kva POWER SUPPLY

Molten-Salt Corrosion Testing Loop and Power Supplies.

UNCLASSIFIED
ORNL-LR-DWG 64740
MAGNETIC GLUTCH & 5HP MOTOR (n\

/

  
 

SHAFT AND SEAL OIL

i

S @
\

BAGK FLOW

PREVENTER_\

 

 

 

   
    

  

MAGNETIC CLUTGH
GONTROL UNIT
I

ANNULUS QIL

  

 

 

 

 

BREATHER AND
OIL OVERFLOW

RETURN FROM SHAFT

&7 |2l RETURN FI AN
c:”
>

[ ]
OIL. TANK (6
T

 

 

  
 
  

FLOW ALARM

 

  
   

STANDBY
OIL PUMP

COOLING
WATER
SUPPLY

HELIUM SUPPLY ——<}

 

 

 

 

 

 

 

    

Uneclassified

Photo 34533

     

FILTER

 

 

 

 

7Y

1
DRAIN TANK

 

 

 

VENT TO
OUTSIDE
OF BLDG.
@ oIL 40% FULL
OIL LINE
<FLEXIBLE SECTION
N ‘
\ & o )
SCRRO
J)
o)
SEAL LEAKAGE
CENTRIFUGAL - RESISTANCE HEATED SECTION o .
PUMP [_, {7} ] -
COOLER
. RESISTANGE HEATED SECTION
L LS
FREEZE VALVE
PLANT
AIR EQUIPMENT IDENTIFICATION
\ FG—FLOW INDICATING GLASS, NON- CAL{BRATED
AIR VENT

FI—FLOW INDICATOR

HCV-HAND- ACTUATED CONTROL VALVE
HV—HAND-ACTUATED BLODCK VALVE
PI—PRESSURE INDICATOR
PV—PRESSURE CONTROL VALVE
XV—CHECK VALVE
TI—TEMPERATURE INDICATOR
SI—SPEED INDICATOR

SC—SPEED CONTROL

LL—LEVEL LIGHT

I, PRESSURE CONTROL VALVE
—» VALVE,NORMALLY CLOSED
—x VALVE , NORMALLY OPEN

-+~ CHECK VALVE (XV)

 

Fig. 2. Flow Diagram of Molten Salt Loop and Utilities.

 
 

 

)

)

%

L)

 

 

Fig. 3.
Dolly.

 

Uneclassified
Photo 26592

 

Photograph of Molten-Salt Corrosion Testing Loop on Mobile

——

 
The flow rate, Reynolds number, pressure drop, and power required
for the heater sections are calculated using the physical properties
of the particular salt mixture and the performance characteristics of
the pump.

A loop pressure drop (feet of head) vs flow (gpm) curve is determined
by using the physical properties of the molten salt to be tested and the
geometry of the loop. By superimposing this curve on the pump operating
characteristic curve, as shown in Fig. 4, the desired flow rate is
determined within the limitations of allowable pump speed.

The electrical resistivity of the molten salt is enough higher than
that of the metal container walls that it can be neglected in determining
the power requirements of the heater sections. The transformer voltage
required for the particular salt mixture shown in Fig. 4 was calculated
according to the =lectrical resistance of the heater section tubing, the
flow rate, and the desired bulk fluid temperature difference. The power
required of the transformer was 58.8 Kw at 1250 amp and 47.2 volts. The
two heater sections, 96 in. and 109 in. in length, are connected to the
power supply transformer in parallel and carry 665 and 585 amp, respec-
tively. The shorter first section {96 in.) has less resistance and
imparts a higher heat flux where the bulk fluid temperature is the
lowest. This arrangement results in approximately equal maximum wall
temperatures at the outlet of both heaters. A wall temperature and bulk
fluid temperature profile of a typical loop while in operation at test
conditions is shown in Fig. 5. The ISR heating is applied only to
straight sections of the tubing, during normel operation, to eliminate
hot spots caused by poor flow distribution in the tubing bends. Two
heater sections are used to reduce the over-all length of the loop that
would be necessary to obtain the desired fluid temperature with one con-
tinuous heater section. The flow of current is restricted to the heater
sections during operation at test conditions by the method of attachment
to the transformer. One terminal of the transformer is connected to the
outlet of the second heater section and to the inlet of the first heater
section. The outlet of the first heater and the inlet of the second
heater are similarly connected to the other transformer terminal. The

loop is grounded at the pump, while the remainder of the loop is
UNCLASSIFIED
ORNL-LR-DWG 65065

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

10 —
— /
/
100 \xl\‘
90 ,’ ’\fieooomm
I""* SALT COMPOSITION:
80 j— LiF-BeF—UFg
4 (60-36-4 mole %) IN
 S— / CORROSION LOOP OF
70 60ft OF Yp-in.~ 0D
= ] TUBING
£ |
[
60 -
9 f 9 5000rpm
L
* /
a 50 4
a
% 4
/ 4000 rpm
/
30
~— /
20 J
/ 3000rpm
10
0
0 { 2 3 4 5 6 7 8
FLOW (gpm)

Fig. 4. Performance Characteristics of Centrifugal Pump, Model LFRB.
TEMPERATURE (°F)

Fig. 5.

UNCLASSIFIED
ORNL-LR-DWG 65066

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

FIRST SECOND LUG 0
o HEATER HEATER COOLING COIL PUMP
!of ; | T

1300 —

| | 4

|
1250 —+—A~ _

| AT TN

- I \\\
1200 /" ! : ~J
/ | ~
/ l f | ™
150 // : i | \\\
/ | | ! \\\

100 |/ {fi | f y

) |
1050 — |

——————— WALL TEMPERATURE

———— FLUID TEMPERATURE
1000 ST |

L
950 [ | ]

 

 

 

 

 

 

 

0 100 200 300 400 500 600
LENGTH (in.}

Temperature Profile of Corrosion Loop at Test Conditions.
electrically insulated.

At test conditions, from 350 to 700 amp of 60—cycle alternating
current flows in each heater section at a potential of 25 to 50 v.
Eiectrical current is supplied to the heater sections through a nickel
lug welded to a thick-walled adapter section of the loop.

Tne power for the heater section is supplied by a 110-kva trans-
former having a low-voltage high-current secondary winding, with a
saturable-core reactor on the primary side. A proportional-control
pyrometer regulates the d-c voltage to the saturable reactor and deter-
mines the voltage applied to the heater section of the loop by the main
power transformer. The amount of power which may be applied to the
heater section is limited by a maximum-adjustment rheostat that limits
the direct current available to the saturable reactor.

A loop high~temperature alarm is designed to cut off the direct
current to the saturable reactor and to reduce the power to a minimum
leakage value. When the loop temperature again drops below the alarm
set.point, the automatic action relay is reset and the power 1ls re-
applied at the rate previously set. The high-temperature alarm thus
serves as an "on-off"” coatrol of the power if an emergency condition
occurs.

The transformer is connected to the loop heater lugs by a 500,000-
circular-mills cable through a 1600-amp breaker. During normal operation
the connections of the heater section are such that the current flow is
confined to the two heater sections (4 connections to the loop). How-
ever, when it is necessary to preheat or provide emergency heating to
the entire loop, the 1600-amp breaker shown in Fig. 1 is tripped, leaving
only two connections to the loop. Thus the entire loop, with the ex-
ception of the cooler coll, is heated by the formation of two parallel
paths of nearly equal resistance.

A downflow centrifugal sump pump designed at ORNL is used. Over 4O
of these pumps have been fabricated of four different materials. An
accumulated total of approximately 450,000 hr of operation in corrosion
testing loops and other high-temperature pumping applications has demon-
strated their reliability.%:> As shown in Fig. 6, the pump has an over-

hung vertical shaft with an oil-lubricated face seal above the liquid
10

UNCLASSIFIED
ORNL—LR—-DWG 30954

   
 
 
  
   
   

23Y2in.

SPARK PLUG
PROBE

FACE SEAL

LIQUID LEVEL

INLET

IMPELLER VANE

 

 

DISCHARGE
ot in.-

 

 

 

Fig. 6. Cross Section of Centrifugal Pump, Mcdel LFB.
11

level in an inert-gas atmosphere. Cooling of the shaft and seal is pro-
vided by a flow of oil down through the hollow shaft and out past the
seal. The inlet to the pump is located on the side, and the outlet is
at the bottom. The performance characterisgtics of the pump for wvarious
pump speeds are given in Fig. 4. A pump speed of approximately 3000 rpm
ie used for most long-term operation. |

The centrifugal pump 1s driven through double V-belts by a variable-
speed magnetic clutch and a 5 hp motor. The speed is regulated by an
electronic control supplying d-c¢ to the magnetic-clutch unit. In order
to decrease the possibility of a flow stoppage as a result of an
electronic unit failure, an auxiliary d-c source is supplied for the
magnetic clutch, which is preset at the desired speed. This clutch
supply circuit is shown schematically in Fig. 7. Relay SR-3 automatically
changes over to the auxiliary supply if any perturbation of the normal
control occurs. The operation of the pump is then maintained by the
auxiliary-clutch supply, while electronic tubes are changed or other
repalrs are being made to the normal supply. In the event of the failure
of both clutch supplies or a motor failure, steps are taken automatically
to provide heat to the entire loop, as will be discussed further in the
following section on alarm and automatic-action controls.

Since the pump contains the only gas-liguid interface of the system,
a sampling device® and level indicators are mounted on the pump bowl
flange. The maximum and minimum liquid levels are indicated by a spark-
plug-type probe which lights an indicator as the molten salt comes in
contact with it.

A cross-sectional view of the sampling device is shown in Fig. 8.
It consists of a dynamic-seal and ball-plug-valve arrangement through
which a dip tube can be inserted into the molten salt and a sample with-
drawn without contaminating the inert-gas covering the liquid in the pump
bowl. The samples, which are removed periodically for chemical analysis,
indicate the type and rate of increase of various corrosion products in
the molten salt.

In preparation for taking a sample, a seal is established around the
periphery of the sample tube, and the inert gas is introduced to purge

the volume between this seal and the ball plug valve below. The ball
r———————— CONTROL VOLTAGE —— =

|

NO. 470 CAPACITROL

PYROMETER

 

 

 

OPENS ON
CLUTCH
LOW SPEED
f 1} Rt
OPENS ON 1 I
LOOP HIGH SR3-2 SRi-4
TEMPERATURE 4— |
1y
cL
BYPASS
OPEN ON OPERATE —
e T

CLOSED ON

LOW TEMPERATURE 1

CLCSED ON TEST

CPEN ON OPERATE-

&1

 

 

OPENS WHILE CHANGING

TRANSFORMER TAP —_|

CPENS ON LOOQP

HIGH TEMPERATURE -:i t__‘ 2

—TeH
(TIME DELAY)
HOFE"

MAGNETIC
AMPLIFIER

 

 

R2-3
AUXILIARY CONTROLS
MAIN RESISTANCE
HEATER cmcurrj
OPEN ON PREHEAT 52T
CLOSED ON OPERATE ”
521
R8-7 s2a
T3 MY AR J—
Al L/ I
MAIN RESISTANCE
HEATERS CONTROL
CLOSES ON MyM
CLUTCH LOW SPEED “t——— [y R
11
SR3-6
CLOSES ON LOOP
LOW TEMPERATURE -
\LO
w 5K
SIMPLYTROL n 4
PYROMETER L ra-s
METER RELAY—|

p CLUTCH AUXILIARY D-C
55 SUPPLY 3

 

 

 

TACHOMETER SPEED AND
LOW TEMPERATURE CONTROL

 

 

 

  
 
 

 

 

OPEN ON LOSS 4 =
OF POWER TQO AC,
PUMP MCTOR (LF8)—e R5-3
T R
&
SPEED CONTROL FOR
AUXILIARY CLUTCH SUPPLY v
‘71—4;»-—
Y Ri-2

-~

 
 
   

5008 0444

 

SS—

 

(v)
__] 0-100v DC I:—-—
—2 Ri-1{ Ri-3 lé‘
T T ]

(SR

L/

 

 

Fig. 7.

l—————— NORMAL CLUTCH SUPPLY ————————=

PARTIAL CLUTCH
SUPPLY CONTROL CIRCUIT

—55

Electrical Schematic of

12

- OPENS ON LOSS

OF CLUTCH

NORMAL SUPPLY

CLOSED AT STARTUP
OF OPERATION TO
ALLOW PICKUP OF R8.

R34
T04-0 R
y[
OPEN AFTER STARTUP

OPEN ON RESET
AND PREHEAT
CLOSED ON OPERATE

SW GBr:r‘ OPEN ON RESET
CLOSED ON OPERATE

CLOSED ON PREHEAT

OPEN ON OPERATE - A
SW {6
CR—T

SATURABLE
REACTOR

LFB PUMP
-—————————————

A-C MOTOR CIRCUIT

 

@
A-C PUMP MOTOR
CIRCUIT POTENTIAL

MAIN RESISTANCE
HEATER POTENTIAL
(re)
€
MAIN RESISTANCE

—_—

 

 

 

HEATER POTENTIAL
TACHOMETER CIRCUIT

SUPPLY FOR BLOWER MOTOR
O.L.

   
      

R8-1

BLOWER,/MOTOR
CONTROL

RE-2 STAR":':-STOP
_l SOL.
DAMP

DAMPER CONTROL
—————n

125vDC —ee———
{(BATTERY CIRCUIT}
8-3 ‘ ‘ I
| SW IS

Oo.L.

 

 

 

 

 

80 uf

Iy (ma)

| \7s}

TDt-C
SW {3 R9-{
o il - |
/ T i ®—
R6-7
R1O-1
RY0-3
RIO-4

12

"———SUB STA, AND DIESEL CKT. POT,—‘~1
)
N

AUTOMATIC OPERATION

MAIN SUPPLY COOLER

RESISTANCE HEATER
RB-6
¥

 

(cR)
@

 

 

   
  

COOLER

120v AC

COOLER PREHEAT CONTROL

 

 

 

 

 

 

CONTACTS POSITION
HANDLE £NG | ON | OFF
1 211 X
Y A
3 413 X
Yo B

 

 

 

 

 

 

SELECTOR SWITCH DEVELOPMENT
CLUTCH CONTROL CIRCUIT

Automgtic Action Relays.

UNCLASSIFIED
ORNL-LAR-0WG 83067

YARIAC NO. 7
LOOP HEATERS

~-— 440v TO 34/17v
10 KVA TRANSFORMER

0-50v AC
13

UNCLASSIFIED
ORNL-LR-DWG 65062

 
  
      

  
      
    
  
  
  

REMOVABLE HEAD
ASSEMBLY

N

SSN..r
-;:'////i///é ____
(Y
o . g _,y/‘//_‘/,f/////
\\\\\\\ix\\\\ %
i

DI
[ 13
DN

N

 

10 Vg in.

? PERMANENT LOOP
MOUNTED ASSEMBLY

 

 

 

Fig., 8. Cross Section of a Molten-Salt Sampling Device.
1

plug valve 1is then opened, and the dip tube is inserted into the molten -~
salt in the pump. A vacuum is then applied to the dip tube, and the
sample is drawn up into the tube. The dip tube is withdrawn, and the

ball piuvg valve closed. The number of sampies 1s limited only by the

£

mount of molten salt which can be removed without depriming the pump.
The fiow of molter salt from the pump is past the drain-tank
on, through the first heater section, through a long-radius
180-deg bend, through the second heater seciion, through a coiled
cooler, and vack to the pump. The cooler section is a helical coil >
mounted in a circular-duct annuius through which ambient air is blown.
To provide the necessary preheat temperature for filling the loop and >
for protection against solidification of the molten salt in an emergency
situation, the cooler coii is provided with electrical heating lugs at
both ends and in the center for electrical-resistance heating. The inlet
and outlet are kept at the same potential electrically to confine the
fiow of current to the cooler coil only. A separate 10-kva saturable
core reactor and transformer are connected to the cooler coil for use in
preheating or during an emergency alarm condition. The control is set
at a predetermined rate of approximately 300 amp and 15 v, and the power
is epplied automatically when required.

Other auxiliary equipment required for the cperation of the loop
inciude a 3000 cfm blowsr, a cooling oil supply, and the necessary util-
ities, such as cooling air for the frozen-plug vaive, inert gas, and
cooling water. The entire pump, loop, and drain tank assembly is shown
in Flg. 3 mounted on & mobile dolly for ease of fabrication, inspection,
and instaliation. ne dclly contains one half of the insulated cooler
duct and the alir deflector in the center, which forms an annular air
passage. 'The back half of the cooler duct is mourted on the permanent
stand frame, which also contains the circulating cooling oil system,
heater connections, and the pump-drive motor. Mounted over the cooler
duct is an insuiated cover 1id that is held in an upright position by
a solenoid-held latch during operation of the loop. In the event of an
alarm conditiorn which shuts off the blower motor, the latch is released
oun the drop 1id and encloses the cooler coil to prevent excessive loss

of hesat. ~r
15

All critical loop welding is done by the Heliarc process with inert
cover gas and backup purge according to a strict welding specification.”
All welds are inspected visually, by dye penetrant, and by x-ray. After
welding, the loop is instrumented with Chromel-Alumel thermocouples and
heaters. The thermocouples are spot welded to the tubing and covered
with shim stock for protection. Both ceramic- and sheath-type heaters
are used for heating such auxiliaries as the drain tank, the pump bowl,
the heater lugs, and the freeze-plug valve. Standby heaters are mounted
on the loop piping for emergency use only in the event of a fallure of
the main power supply. After the heaters and thermocouples are attached,
the loop is covered with 3 in. of high-temperature insulation. The loop
and dolly assembly are tren installed in the facility, and the connections .

are made to controls and power supplies.

Alarm and Automatic-Action Controls

 

The system thermal inertia is low because of the small~diameter
tubing used, and therefore safeguards must be provided to prevent solidi-
fication of the salt in the loop. The salt in the cooler coil will become
solid in less than 1 min if the flow is stopped and no external heat is
applied. An alarm and automatic-action relay system was designed to pro-
tect the loop even though there was a failure of the power source or any
one piece of operating equipment.

The basic ocutline of this system is shown in block form in Fig. 9.
Any one of the alarms shown at the.top of Fig. 9, i.e., any condition,
which will cause flow stoppage or adverse temperatures, will automatically
place the loop in an isothermal or safe condition by performing the
actions listed at the bottom of the figure. This results in the entire
loop being warmed and in a safe or isothermal condition while the
necessary action is taken to restore the equipment to operating condition.
To cover the possibiiity of the failure of the main power transformer,
the ceramic standby heaters are connected after 2 sec, and they will
maintalin isothermal conditions until the main source of power is restored.
All relay actions indicated in the block diagram of Fig. 9 are shown
schematically in Fig. 7. The battery-powered relay R-8 is de-energized

by relasy R-4 to perform the four functions which place the loop on
UNCLASSIFIED
ORNL-LR~DWG 65068

 

 

 

 

 

 

 

 

 

 

 

 

 

LOSS OF NORMAL AND AUXILIARY LOSS OF PUMP LOOP LOW LOOP HiGH LOSS OF MAIN POWER
CLUTCH SUPPLIES (PUMP STOPS) MOTOR (PUMP STOPS}) TEMPERATURE TEMPERATURE SUPPLY TO HEATER SECTION

 

 

 

|

 

 

 

INSTANTANEQUS ALARM-ACTION RELAY (NO
DELAY IF CONTROL POWER IS AVAILABLE )

 

 

 

 

TIME-DELAY ALARM-ACTION RELAY (2sec
DELAY IF CONTROL POWER NOT AVAILABLE
TO ALLOW FOR AUTOMATIC THROWOVER
FROM NORMAL TO ALTERNATE FEEDER)

 

 

 

 

]

 

 

 

 

CONNECTS POWER TO EMER-
GENCY HEATERS ON LOOP
PIPING AT PRESET RATE

 

 

 

 

 

 

SHUTS OFF DROPS LID ON SWITCHES MAIN POWER SUPPLY FROM OPERATE TO CONNECTS POWER TO COOLER COIL
BLOWER COOLER BOX PREHEAT CONNECTIONS ON LOOQP AT PRESET RATE

 

 

 

 

 

 

 

 

Fig. 9.

Block Diagram of Automatic Alarm Actions.

91
17

iscothermal operation.
To guard against the failure of the power supply to the building

which houses the tests or to the bus duct supplying power to the loops,
equipment has been designed and installed as shown in block diagram in
Fig. 10. Bhould a faillure occur of the normal building feeder, a transfer
to an alternate feeder is made automatically within 2 sec. The time-delay
relay TD-1 and relay R-3 of Fig. 7 will hold in the battery-powered relay
R-8, allowing the transfer to be made without disturbing the operation of
the loops. ©Should the bullding electrical power be unavailable for a
period longer than z sec; the emergency diesel generator, which started
immediately, would begin assuming the load through a sequential timer.
Loads would be picked up alternately between motor startup and heater load
until the entire facility of 15 loops had power reapplied within 40 sec
after the interruption. The 300-kw capacity of the diesel generator is
sufficient to operate the loops isothermally until normal building
electrical power is again available.

Other alarms are available for the protection of the loops that give
only an audible or visual signal or both for corrective action to be
taken by the operator. These alarms include loss of blower motor, low
cooling oil flow, loss of cooler preheat potential, improper position of
control switches, improper position of alarm acknowledge switches, and

logs of control circuit potential.

Operation and Maintenance of a Test Loop

 

The startup of a new corrosion testing loop is preceded by a series
of checkouts of equipment. When all the electrical, thermocouple and
control circuits are tested satisfactorily and the loop is leaktight, the
entire loop is preheated to 1100°F with the pump shaft rotating slowly
and the cooling oil circulating. The salt mixture chcsen for the partic-
ular test is introduced into the drain tank in a molten state at a
slightly higher temperatvre than that of the loop. The drain tank level
4probe indicates when there is sufficient salt to f£ill the loop. Inert
gas pressure is admitted to the drain tank and vented from the upper

portion of the loop at the pump.
 

NORMAL
BUILDING FEEDER

 

 

 

18

 

 

ALTERNATE
BUILDING FEEDER

 

 

 

 

 

 

AUTOMATIC SWITCHING
EQUIPMENT

 

 

 

 

 

DIESEL GENERATOR

UNCLASSIFIED
ORNL-LR-DWG 65069

 

AUXILIARY
BUILDING FEEDER

 

 

 

 

 

MANUAL

 

 

STARTS WHEN POWER FAILS

 

 

 

SEQUENTIAL TIMER FOR IN-
CREMENTAL APPLICATION OF
LOAD

 

 

|

AUTOMATIC SWITCHING

 

 

 

SWITCHING
EQUIPMENT

 

 

 

 

EQUIPMENT

|

 

 

 

 

BUS DUCT

 

 

SUPPLYING POWER TO EQUIP-
MENT AND CONTROLS FOR
15 LOOPS

 

 

Fig. 10.

 

 

SUB STATION

 

 

SUPPLYING 1{{0-kva TRANS~
FORMER POWER FOR {5
LOOPS

 

 

Block Diagram of Building Electrical Supply.
19

As the salt is slowly forced up into the loop, its path can be
traced by the temperature readings of thermocouples placed along the
tubing. Level probes in the pump indicate when the loop is full, and
this level 1s maintained by manipulation of gas pressure while cooling
alr is supplied to the freeze-plug valve. When the temperature of the
valve indicates a solid plug, the pressure is released from the drain
tank and the pump speed is increased to begin circulation of the molten
salt. Power from the main transformer is adjusted to maintain the
desired temperature level.. The first load of salt is circulated for a
minimum of 2 hr to clean the system and is then dumped into the drain
tank and removed. The f:1lling operation is repeated with the supply
of salt to be used for the corrosion test.

When the test salt is circulating, the differential temperatures
are established by shutting off the cooler heat, opening the 1lid on the
cooler duct, turning on the blower, closing the 1600-amp heater section
breaker (which connects all four heater lugs), and adjusting pump speed,
cooling air flow, and main transformer power, as required. When the
desired conditions are met, all the controllers, alarm set points, and
automatic functioning relays are set for continuous operation.

In order to assure, as far as practical, that all emergency equip-
ment will function properly when the need arises, a preventive maintenance
program is carried out weekly. A check list is completed for each
facility which calls for the testing of all important alarms, the throw-
over circuit on the auxiliary clutch supply, the cooler drop 1lid, and
the clutch brushes; a visual inspection is made of the system.

The tests under this program have been operated with maximum wall
temperatures of 1200 to 15OOOF, a temperature difference between the
maximum wall temperature and the minimum fluid temperature of EOOOF, and
flow rates up to 3 gpm. Previously tests were conducted with wall tem-
peratures of lSOOOF and higher.® The wall temperatures obtained are
limited only by the strength of the container material used. The tem-
perature differential obtained is limited by the flow rate and power
available. The forced-circulaticn corrosion test facility with eleven
test stands showing in the left background is pictured in Fig. 11. The
remaining four test stands are on the opposite side of the aisle to the

right.
 

 

 

Unclassified
Photo. 32867

 

0¢

 

' . ' o v ki o T
21

Summary

Twenty-five loops have been fabricated with both INOR-8 and Inconel®
and have operated under this program for an accumulated total of over
290,000 hr. Twenty of the loops, thirteen of which were fabricated of
INOR-8 and seven of Inconel, operated from one to two and a half years
before being terminated and examined metallographically.

The long-term operation and metallographic examination of these
loops was instrumental in the acceptance of INOR-8 as the container
material for the Molten Salt Reactor Experiment.l9 The expected corrosion
is expected to be less than 1 mils/yr at the design operating temperature
of 1225°F.

Corrosion specimen weight loss and salt sample data from these loops
indicated that the primary corrosion product is chromium and that an
essentially constant value was achieved after approximately 5000 hr of

operation.l?t

Acknowledgments

 

Many persons have made important contributions to the design and
operation of these facilities. Acknowledgment is made especially to
H. W. Savage under whose direction this program was executed. The suc-
cessful operation of these loops was due to a large extent to
W. H. Duckworth and the shift operations group under R. Helton, and to

many others too numerous to mention.
10.

11.

22

References

J. H. DeVan and W. D. Manly, Corrosion Properties of Fused-Fluoride
Salt Mixtures, Trans. Am. Nuclear Soc., 1 (1):44 (June 1958).

 

. B. Trauger and J. A. Conlin, Circulating Fused-Salt-Fuel
ITrradiation Test Loop, Trans. Am. Nuclear Soc., 2 (L1):173-4
(June 1959). :

 

 

J. P. Blakely, Molten Seit Compositions, Oak Ridge National Laboratory
Report CF-58-6-58 (June 12, 1958).

J. J. Keyes and A. I. Krakoviak, High-Frequency Surface Thermal
Fatigue Cycling of Inconel at 1400%F, Trans. Am. Nuclear Soc.,
2(1):22-4 (June 1959).

 

W. ¥. Boudreau, A. %. Grindell and H. W. Savage, The Development and
Operation of Centrifugal Pumps for Liquid Metals and Fused Salts at

1100-150COF, Trans. Am. Nuclear Soc., 2 {1):17-18 (June 1959).

W. B. McDonald gnd J. L. Crowley, A Sampling Device for Molten Salt

Systems, Oak Ridge National Laboratory Report ORNL-2088 (March 7, 1960).

T. R. Housley and P. Patriarca, Procedure Specification PS-2 for
D.C. ARC Welding of Inconel Tubing for High Corrosion Applications,
ak Ridge National Leboratory.

o

W. D. Maniy et &l., Metallurgical Problems in Molten Fluoride Systems,
Proceedings of the Second United Nations International Conference on
the Peaceful Uses of Atomic Energy, Vol. 7, pp. 223-34%, United
Nations, Geneva, 1058.

J. A. Lane, H. G. MacPherson and F. Maslan, Fiuid Fuel Reactors,
p. 596, Addison-Wesley, Reading, Mass., 1958.

5. E. Beail et gl., Molten-Salt Reactor Experiment Preliminary Hazards

Report, O=k Ridge Natioral Lavboratory Report Cr-6l-2-46
(Feb. 28, 1961).

J. H. DeVan and R. B. Evans III, Corrosion Behavior of Reactor
Maverials in Fluorids Salt Mixtures, Oak Ridge National Laboratory
Report TM-328 (September 19, 1962 ).

 
O 0= OvJl F o o B

23

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