ORNL-TM-2987.txt

 

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ORNL-TM-2987

Contract No. W-T4O5-eng-26

 Reactor Division

DEVELOPMENT OF FUEL- AND COOLANT-SALT CENTRIFUGAL PUMPS FOR
THE MOLTEN~-SALT REACTOR EXPERIMENT

P. G. Smith

 

LEGAL NOTICE

Thls report was prepared as an account of work
sponsored by the United States Government. Neither
the United States nor the United States Atomic Energy
. | Commission, nor any of their employees, nor any of
‘} their contractors, subcontractors, or their employees,
'| makes any warranty, express or implied, or assumes any
legal liability or responsibility for the accuracy, com-
pleteness or usefulness of any information, apparatus,
product or process disclosed, or represents that its use
would not infringe privately owned rights.

 

 

 

 

~ OCTOBER 1970

. OAK RIDGE NATIONAL LABORATORY
) Ok Ridge, Tennessee
- operated by
UNION CARBIDE CORPORATION
for the
U S. ATOMIC ENERGY COMMISSION

SISTRIGUTION OF THIS DOCUMENT IS

 
“

.
111
CONTENTS
-~ o f | - | Page

Abstract S 0 9 S 5 0 S8 P LB ISP I T O PP AP P RO N PSS LSS NI ESNES SN S l
GeHEral Description Of_the MOlten-S&lt Pump 5 6 40 990 S Qe LR ST EER OSSO BSOS 2

 

Test Apparatus |
Molten-Salt Pump Test Stahd secescescasssssssssecsencrssoss 5
Molten-Salt Properties ........;...........................

Bench Tests and Cold Shakedown Tests _
Force-Deflection Characteristics of Shaft ..ccevcecesenasee 9
Critical Speed of Shaft Assembly .eeecocecceecencencncnsene 9
Room-Temperature Dry.Runs teessarsessasesessscasscssesse s 11

Molten-Salt TesSts cececicesocccrrsrsscccnnsensscsssssosonnsesscaess 11
Hydraulic Performance ..ccceceeceess teseeracrctrecensnanes 11
Cavitation PErfOrMANCE «eeeeeeesseesscossecesssnacennnesnes 1k

% Effectiveness of Shaft Annulus Purge Against Back Diffusion
’k'r ofRadiOaCtive Gas .l."-l..............ll...q....Il....’.. lh

< | Measurement of Undissolved Gas Content in Circulating Salt 17

Problems Encountered During Pump Fabrication and
MOlten-Salt TEStS ® 0 2SO N PO PRI RIS RSLENEB SN Pe LS e 8 2 e 0w 21

Fabrication Problems .ceeeceecseccsscccssssosascassscssosss 22
Shaft Annulus Plugging seceecevescnssocssscasosossscsscssnsse 22
Insufficient Running ClEBIBNCES «evsesrssscssoancsccanossss ol
0il Leakage from the Catch Basin into the Pump Tank ....... 26
Pump Tank Off-Gas Line PLUEEINE wevevevevennessonnennaneass 28
Failure of We1d'Attachmén£of'Parts‘cf Flow-Straightening

DEVICE. coevessonssocesesanssssasvocsosssccsccsoscnnasocsns 28

© Mark-2 Fuel-S8lt PUID euvevseneruesnenseneanesnasnsancssesessess 33

| *Déécri?tion of Pump...;}..;.;;;..;..;....,.....;;....;...., 33

Hydraulic PETTOTIIANICE s v e e vvnsasossncossenceneeanaonasaesos 36
Measurement of Undissolved Ges Content in Circulating.

-' Salt o-uon-aoo;-ooJ--o-i¢Q--¢oooooooooo-.oooo}do(-;uoiob.i 36
, " Restrictions to Purge-Gas Flow ceereeienteecentsttertiaenes * 36
B ) . Performance Of MOlten-SBlt PumpS in MSRE'o.oooaoooocouoc-;;oouoo 38

*)

i z . . ConCluSionS ....O...O..l‘....I..IICOCO...'...0..!'..l‘.....l.l.'.. ho
Acknowledgments ......'.QOO.'....Ill.'l.l...l...'....0'!0!00'.0'0 ho

 

 
 

 

References .....‘l....‘.j'.l..'...Q.l..‘l._l......ll...‘l:..l‘l‘OO

APPendix-MSRE DraWings .....‘...'..'...C.VOOOO'.l....‘l..ll.l._c.

41
43

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a) “3

DEVELOPMENT OF FUEL- AND COOLANT-SALT CENTRIFUGAL PUMPS FOR
THE MOLTEN-SALT REACTOR EXPERIMENT

P. G. Smith
Abstract

The Molten-Salt Reactor Experiment (MSRE), a small nu-
clear power reactor that produced about 7 Mw of heat while
operating at approximately 1225°F and atmospheric pressure,
requires & pump in each of two circulating molten-salt sys-
tems. A vertical centrifugal sump-type pump was developed
for each system through water and molten-salt tests of pro-
totype pumps at temperatures to 1LOO°F and hot shakedown
operation of the actual reactor pumps before they were quali-
fied for reactor service. The development experience with
the pumps in the molten-salt pump test stand and the perfor-
mance of the reactor pumps in the MSRE are discussed here.
The hydraulic performance of the pumps circulating molten
salt corresponded closely with the performance obtained with
water. The reactor pumps served well throughout the approxi-
mately 30,000-hr operating life of the MSRE, which spanned
the period August 1964 to.December 1969, during which the
reactor produced 105,737 Mwhr(t) of nuclear energy. A back-
up pump (Mark-2), which contains additional volume in the
pump tank to accommodate thermally expanded salt, was also
fabricated and tested for the MSRE.

Keywords: pump, molten salt, Molten-Salt Reactor Ex-
periment, centrifugal pump, sump-type pump, high temperature,
nuclear reactors, pump hydraulic performance, water test
puup.

A centrlfugal pump was developed for c1rculating molten salt at ele-

'_ vated temperatures in the Molten-Salt Reactor Experlment (MSRE) 1 Briefly,
-_the MSRE 1s & salt- fueled graphite-moderated single—region nuclear reactor

test facility with a heategenerstion rate of approximately 7 Mw(t). Two

 salt pumps are required,rone'in the fuel-salt loop and the other in the
*coolant-salt loop.- Since the designs of the two pumps are essentially
-ridentical, prlmary attentlon is. given here to the fuel-salt pump.

‘The pump is a vertical-shaft sump pump with an overhung impeller and

an oil-lubricated face seal. It was developed through a series of bench

tests, water tests,® cold shakedown operations, and high-temperature
 

molten-salt tests. The problems encountered during development and
testing and the results of pump'operatibn at afibient and elevated tem-
peratures (up to 1400°F) are discussed in this report. Hydraulic per-
formance data, priming conditions, and coastdown characteristics were
obtained, and the effectiveness of spray devices for xenon removal was
demonstrated.

Thermal-stress and strain-fatigue analysesa-were made for the pump
tanks of both the fuel- and coolant-salt pumps. They were made for an
estimated operating history that included 100 heating cycles from room
temperature to 1200°F and 500 reactor power change cyéles‘frdm zero to
full power. The calculations indicated that = cooling air flow rate of
200 cfm was required for the fuel pump tank, while the coolant pump tank
vas capable of the required service without air cooling. _

The pattern followed in the development of these pumps and the de-
sign of a similar pump were discussed elsewhere in some detail.* The
problems and tests required for developing other specific elevated-
temperature pumps have been reportedJ5-4° ‘ -

Fuel- and coolant-salt pumps were instaelled in the appropriate salt
circuits of the MSRE, where they each circulated salt or helium at ele-
vated temperatures for & total of approximately 30,000 hr. The reactor
was operated up to full power and was recently shut dowm permanently.
During operation of the reactor, which produced 105,737 Mwhr(t) of mu-
clear energy, the lubricants for the bearings and seals and the insu-
lation for the drive motor were exposed to a nficlear radiation environ-
ment., |

~ The numbers of the drawings for the fuel- and coolant-salt pumps,
the drive motors, the lubrication stand, and the Mark-2 fuel-salt pump
are listed in the Appendix. | ) |

General Description of the Molten-Salt Pump
The pump is of the centrifugal sump type with a vertical shaft.

It consists of three main components: the pump tank, the rotary assembly,
and the drive motor (see Fig. 1). The three main components are bolted

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ORNL-LR-DWG-36043-8R2

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SHAFT WATER
COUPLI COOLED : ' ' ‘
MOTOR

SHAFT SEAL , | ‘
(See Inset) = fiF——=mgoo—mie—-—o————rf g — - | )

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N\
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" LEAK
DETE

LUBE OiL IN-

 

BE OIL. BREATHER

 

 

BALL BEARINGS'

(Face to Face) BEARING HOUSING

" BALL BEARINGS

GAS PURGE IN | . BASIN
(Back to Back ) '

SHAFT SEAL (See Inset)

SHIELD COOLANT PASSAGES
(In Parafiel With Lube Oil)

SHiELD PLUG
GAS PURGE OUT (See inset)

LUBE OIL OUT

SEAL OiL LEAKAGE
DRAIN

LEAK DETECTOR

SAMPLER ENRICHER
(Out of Section)
{See !nsefl

GAS FILLED EXPANSION
SPACE

  
  

 
  
 

STRIPPER ~T
BUBBLE TYPE {Spray Ring) “
LEVEL INDICATOR SPRAY -

OPERATING
LEVEL

ST R TR

TSN Ti)

To Overflow Tfink

 

Fig. 1. Cross Section of'Fuel-Salt Pump.
 

 

together and sealed with oval ring-joint gasketed flanges. The ring-
joint grooves are connected to a lesk-detection system. The motor and
rotary assembly may be removed from the pump tank either as a unit or
separately. All parts in contact with molten salt are constructed ofA
Hastelloy N,* a nickel-molybdenum-chromium-iron alloy..

The pump tank, which provides volume to accommodate. the thermally
expanded salt of the system, contains the pump volute or ca51ng, the
Xenon-removal spray device, the salt level indicators, and various access
nozzles. |

The rotary assembly consists principally of the bearing housing; the
pump shaft, which is mounted on commercially available conventional ball
bearings; the shaft seals, which constrain the circulating lubricating
oil from leaking out of the bearing housing; the shield plug, which is
cooled with circulating oil; and the pump impeller. The shield plug and
other parts of the rotary assembly that come in contact with the salt
are suspended in the pump tank through a large flanged nozzle at the top
of the tank. _ |

The drive, which is housed in arhermeticaliy §ealed vessel, is a
squirrel-cage induction-type motor ratéd for 75-hp.duty at 1200 rpm.

The electrical inéulatidn system is resistant to a radiation dose of up
to 10° rads and the grease lubricant is reported!! to be capable of with-
standing a dose of more than 3 X 10° rads.

The pump has some unusual features required by its application that
.are not found in the conventional sump pump. The pump tank contains a
salt-spraying device to remove 1335Xe (neutron absorber) from the circu-
lating fuel salt and also has two gas-bubble sensors to indicate salt
level. The spray device is connected to the volute discharge, frbm which
it receives a proportioned flow of about 50 gpm of salt at pump‘design
head and flow. This flow and other leakage fldws (bypésg flow) pass
through the pump tank and return to the system at the pump‘inlet._.A
split purge-gas flow in the shaft annulus keeps oil vapors from énfering

the salt system and fission gases from entering the region of the shaft

 

¥Hastelloy N, known also as INOR-8 and Allvac N, has the basic com-
position, by weight, 15-18% Mo, 6-8% Cr, 5% Fe (max), 0.4-0.8% C,
balance Ni.

il
 

 

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3

2

lower seal. The down-the-shaft portlon of the purge-gas flow removes
136%e by contact w1th the salt spray and dilutes and transports 1t from
the pump tank to the off—gas system. The pump is mounted on a flex1ble
support de51gned to accommodate thermal expansions. A flow of nltrogen
across the exterior of the upper nonwetted portion of the pump tank re-
moves nuclear heat dep051ted 1n the tank wall The bolt exten31ons,
which can be seen in Fig. 2 prov1de for remote installation and removal

of the drive motor and rotary assembly in the MSRE.r
Test Apparatus

Molten-Salt Pump Test Stand

A schematlc view of the ‘test stand components is shown in Fig. 3.
The components include ‘the drive motor, the test pump, and the salt
piping, which is 6-in. IPS sched 40, except for a section of plpe at the
pump inlet, which is 8-in. IPS sched 4LO. Other components include a
venturi,flowmeter, the heat removal system, a drain tank for salt storage,
the:preheating system, a flow straightener, high-temperature pressure
and temperature senso’rs,"’the‘lubrication:system,12 and two salt freeze
flanges, one of which provides a place to mount an orifice Plate torset
the_system'resistancefto saltiflow, The system resistance was varied
with four ,orii‘ice plates :having di_ff__erenthole diameters. The heat re-
moval system,'which is arsalt;to;air heat exchanger, was used to control
the salt temperature., The drain tank stored the fluoride salt in the

molten state when the system was ‘not in operatiOn.' Commer01al diaphragm-

'rsealed NaK-filled pressure transmitters were used to indicate pressure |
‘at the pump discharge and at the 1nlet and throat of the venturi. Trans-

| former controlled heaters were used,to preheat the salt plplng and com-

ponents, and Chromel—Alumel thermocouples monitored the system tempera-

,rtures. Conventional 1nstrumentatlon was used to display and record tem—

- peratures, salt flow, pump drive motor power, and salt level 1n the pump

tank. A photograph of the. test facillty, Fig. b, shows the pump 1n the
left upper foreground a portion of the salt piping beneath and to the

rear of the pump, and a portion of the control cabinets.
 

  

PHOTO T0901

 

 

 

 
 

 

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L4

and Bolting

Rotary Assembly,

Fuel-Salt Pump Drive Motor,

Fig. 2.
for Remote Maintenance.
 

 

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ORNL-LR-DWG 72414

 

 

 

 

 

 

 

 

 

_THERMAL | |
CWELL -
- - AIR COOLER

o IM
- DISCHARGE ", |

 

_1'—

PRESSURE MSRE. _
' PIPE HEATER
: FREEZE -T ";

~—8-in. PIPE o - . FLANGE 4

6-in. PIPE ' I
‘ — -’
| | II--ll
- . ‘ FLOW STRAIGHTENER
INLET °~  FREEZE VALVE | . l MSRE FREEZE
PRESSURE \ , - - FLANGE

 THROAT ||~ . : |
PRESSURE— - MAND VALVE

 

 

 

 

 

 

 

 

 

 

-

DUMP
TANK

 

 

 

Fig; 3. Schematic Diagram of Molten-Salt Pump Test ‘Stand.
             

PHOTO 70988

 

Fig. 4. Photograph of Molten~-Salt Pump Test Stand.

 
 

 

 

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Molten-Salt Pr0perties

 

The molten salt used for pump tests was a mixture of lithium fluoride
(LiF), beryllium fluoride (BeF,), zirconium fluoride (ZrF,), thorium fluo-
ride (ThF,), and uranium fluoride (UF,) in proportions of 66.4k, 27.4k, 4.7,
0.9, and 0.7 mole %, respectively. The mixture is solid at room tempera-
ture and melts at approximately 850°F. The densityl?® and viscosityl4 at

three temperatures of interest are given below:

 

Temperature Density Viscosity

- (°F) (1 /ft2) (cps)
1100 - 132 11
1200 130 8
1300 129 ' 6

 

Bench Tests and Cold Shakedown Tests

Force—Deflection‘Characteristics of Shaft

 

The force-defléction characteristics of.the shaft were measured
with the shaft assembly supported in the bearing housing and with the
force applied at the .impeller. A typical curve of shaft deflection at
the impeller versus force is shown in Fig. 5. This information and
deflection data obtained during water tests were used to determine the .

unbalanced force-vector acting on the 1mpeller at various head, flow,i

- and speed operating condltions 18 The force values were used to analyze
shaft bendlng stresses and bearing reactions and to specify the shaft

'support bearings.

Crltical Speed of Shaft Assembly

The crltlcal speed of each shaft assembly was determlned by V1brating

rthe shaft assembly in the transverse direction.. The_shaft assembly 'was -

supported in the bearing hous1ng and mounted vertically on a rugged-steel
structure anchored to the building floor. The vibrating force was applied

at the impeller and held constant over a range of applied frequencies.
 

 

of Pump.

10

(X 10-3) ORNL-DWG 70-6823
40 |

 

 

3" <
e

 

20

SHAFT DEFLECTION (in.)

 

10

 

 

 

 

 

 

 

 

0 100 200 300 400 500
FORCE (1b)

Fig. 5. Shaft Deflection Versus Radial Force Applied to Impeller

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11

Data were obtained for frequency versus vibration amplitude. The critical
speed determined by the frequency at which the amplitude increased ‘sharply
checked quite closely with the calculated value. TFor the fuel-salt pump
the value was calculated to be 2850 rpm and was measured to be within

100 rpm of this value.

Room-Temperature Dry Runs

After assembly & pump rotary element is normally operated for about
one week or longer in a cold shakedown stand before installation in the
hot test stand; This operation-is conducted to verify that the element
is free of mechanical problems and to test the performance of the shaft
bearings and seals. Theuoil-leakage from a properly performing shaft
seal is usually 10 cc/day or less.

Molten-Salt Tests

 

Tests with molten salt were conducted with the prototype and re-
actor pumps to (1) verify the hydraulic performance observed in the
water tests, (2) determine the effectiveness of the gas purge down the
shaft annulus against the intrusion of radioactive gas, (3) measure the
concentration of undissolved_gas in the circulating salt, (4) perform
acceptance tests of the reactor pumps prior to their installation into
the reactor system, ‘and (5) test the overall long-term relisbility of
the pump and drive motor atudesign and off-design conditions. Table 1
presents & summary of the fiolten-aalt test operatioh of'the'prototype

pump, the rotary elements for the reactor pumps, and the Mark-E fuel-

”:“-salt pump.

 Hydraulic Performance.

Hydraulic performance'tests were conducted with 1l3-in.~ and 11 1/2-in.-
OD fuel punp impellers in the molten-salt pump test stand with the fuel-
salt pump tank and volute installed. ‘The head- capacity performance of the

13-in.~-0D impeller with both water and molten salt is shown in Fig. 6, in
which the head is plotted against flow for three test speeds. At 1030 rpm,
 

12

 

 

 

Mark-2 pump

< : ‘ Poble 1. Sumary of Tests of MSRE Pumps in _the Molten-Salt Pump !l'estVStand
Tost -, Molten-Balt Puvp Shaft © Molten-5alt  Impeller Test : . Reason
o Temperature Speed Flow Diameter Duration Primery Purposes of Test Tor
‘ (' (rpm) (ewm) (in.) (br) . Termination
1 80-1200 1150 13 118  Ghaxedown test of prototype fuel-
galt pimp e
1l 1200 7002030 T50-1600 13 21T  Hydraulic performance test of Shaft seizure
prototype fuel-salt pump T -
2 1200 700-2030  T50-1200 13 96  Same a3 above Bcheduled
3 1200 600-1150 R0O-1500 11 1/2 1,968 Bame as above Variable frequency
‘ ’ 7 motor-generator set fallure
b 1200 185 1100 1 1/2 1,848  Back-diffusicn teste of prototype  Variable frequency
- fuel-galt pump motor-generator set fallure
5 12001320 1185 1100 1 1/2 792 Gas-concentration tests in circu-  Scheduled
: ) lating salt and back-diffusion
tests of prototype fuel-salt
pump
6 1200 1150 1070 u 1/ 335 " Gas-concentration tests of proto-
type fuel-salt pump in circu-
lating salt ’
6 1000-140C 600-1150 S00=-10T0 11 1/2 368  Hydrsulic performance of prototype Shaft annulus plugged
: tuel-sglt amp
T 1200 1150 1070 1 1/2 120 Proof test of lubrication stand -
and fuel pump supports
7 1100-1300 T00-1150 600-1070 1n 1/2 409 Scheduled
8 11001300 1159 1070 1 1f2 168  Proof test of coolant pump lubri- Scheduled
. cation stand and fuel pump sup-
ports
g 120 o800 11 1/2 Reactor fuel pump hot shakedown Shaft rubbed at startup
test
10 1200 1750 750 10 1/3 90  Reactor coolant pump hot shake- Scheduled
down test
n 1200 u7s 1200 1 1f2 100  Reactor fuel pump hot shakedown Scheduled
test
12 12004515 175 1200 13 452  Reactor spare fuel pump hot shake-  Impeller rubbed volute
. down test
13 1200 s 540 10 19/32 1,000  Reactor spare cooclant pump hot Scheduled
7 shakedown test
14 1200 uT7s 1200 13 2,654 Reactor spare fuel pump hot shake-~ Loop flw straightening
down, back-diffusion, gas concen- vanes became detached
tration tests '
15 1200 1175 1200 13 155 Reactor spare fuel-punmp impeller Bcheduled
shakedown tests
16 1200 1175 1200 13 166  Reactor spare coolant drive motor Scheduled
‘shakedown tests
17 1200 175 1200 nifz 2,631  Prototype fuel pump test Scheduled
18 1200 u7rs 1200 nifz 100  Reactor spare fuel pump hot shake-  Scheduled
i down tests
19 1200 1750 90 10 19/32 100  Reactor spare coolent pump hot Scheduled
shakedown tests .
20 1000-1325 17 1350 1 if2 1k,000 Perfarmance and endurance tests of  Continuing

 
n

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13

ORNL-DWG 65-6666

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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1

 

 

60 .
\ ®
® . \
.!
50 \
{030 rpm
40 g
= : _ ™~ 860 rpm
S
= 30
tw
I. * \.\ . -
>~ e
x 1\ 700 rpm
| |
20 ALLIS-CHALMcRS MFG, CO. IMPELLER AND VOLUTE DESIGN
SIZE 8x6; TYPE E; IMPELLER P482, 13-in. OD
ORNL WATER PERFORMANCE
10 DATA POINTS: ORNL MOLTEN SALT PERFORMANCE AT i200°F
o - - e , —
0 200 400 600. 800 1000 1200 1400 1600 1800

- @, FLOW (gal/min}

‘F:Lg. 6. Hydraullc Perf‘ormance of Prototype Fuel—-Salt Punmp with Water
and with Molten Salt. i o o
 

1k

the molten-salt head veries as much as 1 1/2 £t from that of water, and
at 860 and 700 rpm the head for the molten salt is low by approximately
1 ft.

Cavitation Performance

 

The NPSH requirements for the pumps, as reported by the manufacturer
of the hydraulic components (volutes and impellers), are 5.5 and 11 ft,
respectively, for the fuel- and coolant-salt pumps at their operating.
conditions. Converted to pressure of the circulating salt the NPSH values
aré 5 and 10 psia, respectively. These pressures are below atmospheric,
and evacuation of the pump tank gas space would be required to investigate
the suction pressure at which cavitation sets in. Since1¢vacuation is
required to cause cavitation and the operating pressuré of the pump'tanks
in the MSRE is 5 psig, experimental investigations of cavitation inception
‘were considered unnecessary and therefore were not performed.

Effectiveness of Shaft Annulus Purge Against Back Diffusion of
Radioactive Gas '

 

The migration of radioactive gases from the pump tank to the region
of the shaft lower seal via the shaft annulus could result in polymeriza-
tion of the oil that leaks past the seal and lead to plugging of the drain
line from the oil catch basin. To minimize this migration, a flow of
helium purge gas was introduced down the shaft annulus. Figure 7 is a
schematic diagram of the shaft annulus configuration and the purge-gas
flow paths. The upper end of the flow path for the down-the-shaft purge
contains a lsbyrinth seal (not shown), which has a 0.005-in. diametral
clearance. |

In back-diffusion tests, 85Kr and nitrogen were injected-into the
pump tank as shown. The concentrations of 85Kr in the pump tank off-gas
line and in the line from the leakage-oil catch basin were determined
with count-rate meters for variocus flow rates of purge gas. The data
shown in Table 2 were obtained during the tests. The 8F5Kr was not de-
tected in the purge gas from the catch basin even with a count rate

-10
meter capable of detecting a concentration as small as 0.95 X 10 Ci/cnfi.
15

 

 

 

 

 

 

 

 

 

 

 

 

 

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Tz 0

.rfl (
=< -

: . 2T ‘
awn

 

 

 

 

 

. Fig. 7, fSchem&tic,Diégiam of_Purge,Ggs:FlowiPassages'in

Fuel-Salt

 
 

16

These date indicate the capability of the purge gas at flow rates of
approximately 0.25 liter/min to reduce the concentration of 85Kr in the
catch basin by a factor as much as 35,000 times below the concentration

in the pump tank.

Table 2. Back-Diffusion Test Results.

- Diametral clearance; 0.005 in.

 

Shaft Purge = Catch Basin Purgea 85Kr Concentration'in Pump Tank

 

 

(Liters/day) (liters/day) (Ci/cmB).
| "
- X110

406 - k87 0.89
406 | L87 - 0.89
%30 497 ' 2.06
382 481 2.77
366 | 351 | 3.28
215 360 1.85
108 - 360 1.21
173 673 1.65
109 360 ‘ 0.75
109 681 0.90
10k | 681 3.5k
o |

85Kr concentration in catch basin was less than
0.95 X 1071° gt g1l purge flows.

The meximum permissible concentration of radioactive gases in the
catch basin to avoid polymerization of the leakage oil was calculated
to be 3.1 x 10~ Ci/en®. Calculations based on this limitation and the
data of Tsble 2 indicate & maximum permissible concentration or radio-
active gases of 2.4 to 11.0 Ci/cn® in the pump tank. The results of
additional calculations relating the flow rate of pfirge gas in the down-

the-shaft annulus to the concentration of radioactive gases in the pump
 

17

tank for a conservatlve assumption of the MSRE nuclear operating condi -

tions are presented in Flg 8. This figure indicates that a flow rate

of purge gas of less than 1 liter/mln suffices to protect the seal oil

leakage in the catch basin'from polymerization by radiocactive gases.

A satisfactory supply of purge gas was available at the MSRE.
Additional back-diffusion tests were made with 8SKr injection in

which the shaft annulus labyrinth seal clearance was 0.010 in., and the

data obtained are given in Table 3. With a detector sensitivity of

1.5 X 10~ ? Ci/cnP 885Kr could only be detected in the catch basin at

low down-the-shaft purge flow rates. ' '

Table 3. Back-Diffusion Test Results

Diametral clearance: 0.010 in.

 

Catch Basin Kr Concentration

 

 

Shaft Purge " purge (ci/cmB)
(1iters/day). (1iters/day) — :
, - In Pump Tank In Catch Basin
- . -8 . alo
212 173 - 2.66 x 10 <1.5 X 10
: 8 . -10
232 © 16k . 5.50 x 10 <1.5x 10
' - , D -8 - -
12 105 h.2h x 10 <8.17 X 10

 

Measurement of Undlssolved Gas Content in Clrculating Salt f

o Undesirable quantities of gas bubbles in the pump tank liquid can
be entrained in the c1rculating salt by the return of salt that has
'_leaked into the pump tank: from the high—pressure side of the pump 1 The
high velocity of these salt leaks from the internal spray and other '_
- sources within the pump tank can carry gas under the salt surface. The
m:downward velocity of the returning salt may then carry the bubbles to |
the impeller inlet and on into the circulating salt.

' To obtain insight into this the concentration of undissolved gas

in the c1rculat1ng salt was measured by.u51ng gamma, radiation densitometry.
 

 

18

ORNL-DWG €3-6483

 

 

 

 

 

 

 

 

 

 

 

 

20 - T |
= | 10 Mw POWER |
E * 100 % STRIPPING EFFICIENCY
216 50 gpm BYPASS FLOW ]
T \ 5 psig PUMP TANK PRESSURE
L3
Z e
2 42 NG
o *
= \\\\\\\
=
O
Z 8 S
g \Q
s 4
»
0
TR
0 : |
0 1000 2000 3000 4000 5000

PUMP TANK PURGE (liters /day)

Fig. 8. Concentration of Radiocactive Gas Versus Purge-Gas Flow Rate
in Prototype Fuel-Salt Pump.
 

 

»

1

A LO-Ci 187(Cs source of 0.622-Mev gamma rays was placed on one side of
the salt piping at the pump inlet, a region of low static salt pressure,
and a radiation detector was placed on the other side. The detector
consisted of a cylinder of plastic phosphor (3 in. in diameter and 6 in.
long) and an electron multiplier phototube. The plastic phosphor absorbs
photons, which are transmitted from the source through the salt. Light
is emitted by the plastic-phosphor to a phototube that produces a current.
The current is a function of the photofi transmission through the Salt,
which in turn is an inverse function of the density of the salt. The
signal current from the detector is fed to a suppression circuit that
indicates only variations in the current. The current indication is
recorded on Visicorder tape. Thus an increase in the concentration of
undissolved gas, which causes. a decrease in éalt density, is indicated
by an increase in the éurrent outpfit of the densitometer. ‘

The densitometer was calibrated over a small rénge of thermal change
in salt density correspondinéfto-themsalt temperature rangerlloo to
1400°F. During calibration the salt contained no entrained gas. The
pump was not bperating,_sbfgas bubbles could leave the densitometer and
enter the higher elevations_in‘the salt system. Thermal-convection
velocities in the salt were too small to entrain fresh gaé from the pump
tank. | | o

The two Visicorder traces shown in Fig. 9 give a measure of helium
concentration in the salt loop at two different salt levels in the pump
tank. The pump vas operated with a 13-in.-OD impeller at & flow of

1650 gpm through the 6-in,-diam pipe and a salt temperature of 1185°F;

approximately 85 gpm of salt was bypassed through the spray ring. The

_curves are plotted with the flow density at zero deflection for compari-

‘son and to illustrate:the transient behavior of the gas concentration

when the pump is first stopped (flow reduction to zero)'énd then started

'_(flcw_increase frdm'01t011650 gpm); Trace I presents the density data

for the normal level of salt in the pump tank (3 3/8 in. above center

_line of the volute). Trace II relates to a higher salt level in the

pump tank (4 7/16 in. sbove the center line of the volute). The gas

concentration in the circulating salt when operating at the normal level
was 4.6 vol %, and at the other higher level it was 1.7 vol %. The
 

20

 

 

 

ORNL-DWG 65-11798

10

o2

@ SILICA

, 8- BEAM

& FILTER

Tz

j 6= [ 46%

n

5+5 I NORMAL PUMP
= a BOWL LEVEL
/ 34

Sk

5 | © I UPPER PUMP

o2 BOWL LEVEL

| ui 1

i o

-1 SALT TEMPERATURE: H85°F

VOLUME SENSITIVITY: 0.64%/div

 

i ke ek e Lt

0 20 40 60 80 {00 120 {40 160 - 480 200
TIME (sec)

Fig. 9. Concentration of Undissolved Gas Versus Time as Determined

by Gamma Radiation Densitometry of Prototype Fuel-Salt Pump with 13-in.
Impeller and 1650-gpm Salt Flow.
 

 

 

b

¥

»

21

gensitivity of the Visicorder wvas 0.64 vol % per division. At the higher
operating level, the discharge ports of the xenon removal spray ring were

covered W1th salt. Since the high-velocity spray from the xenon-removal

spray ring is a magor contrlbutor to the agitation that causes gas bubbles,

it is understandable that the gas concentration was lower when operating
at the higher level in the pump tank.

In s separate test, the same densitometer arrangement was used to
measure gas concentrations in the fuel salt circuit at the MSRE. The
principal conditions inclndedgthe impeller diameter of 11 l/e,in., a salt
Tlow of 1150 gpmrat l200°F; normal operating level' and a spray-ring flow
of 50 gpm. The v01d fraction in the salt was not detectable at these
conditions. At & lower level’ of salt in the pump tank, a void fraction
of 2 to 3 vol % was indicated Subsequent measurements with the same
densitometer on the molten- salt test loop and with a 11 l/2-1n -diam
impeller, a flow of 1200 gpm at 1200° F, the salt at the’ normal operating
level, and a spray-ring flow of 50 gpm gave a void fraction of 0.1 vol %.

Comparing the gas concentrations for operation with the 13-in.- and

‘the 11 l/2-1n.-diam 1mpellers at the normel operating level shows that

the content is less with the smaller 1mpeller by a factor of 46. This

is attributable to the xenon-removal spray flow, which is approximately

50 gpm for the smaller impeller, compared W1th 85 gpm w1th the 13-in.-diam
impeller. The jet velocity from the spray ring is cons1derably less with
the SO-gpm flow; thus there is less agltatlon of the liquid level surface
upon impingement of the jet streams.

Problems Encountered Durlng Pump Fabrication and
' Molten-Salt Tests

_Fabrication{problems were”encountered with the dished heads for the

~ pump tanks, the1impellerLand'rolute_castings, and the hermetic vessels

for enclosing the drive motors. Pump operating prdblems-were'encountered

_with the shaft purge flow, shaft and impeller running clearances, ‘shaft

seals, and the flow straightener in the test stand salt piping during
testing and operation of the pumps at elevated temperatures.
 

 

22

" Fabrication Problems

The Hastelloy N dished heads for the pump tanks were originally fab-
_ricated by hot spinning of plate stock. The resulting heads contained
'many crack-like defects on the knuckle radius that were readily detectable
by dye-penetrant inspection. However, the heads were repaired by removal
of the cracks by grinding, and this rendered them ussble forjtesttpurposes.
Later, during fabrication of the reactor pumps, the problem was solved by
hot pressing the plate stock.

Considerable effort and time were expended to obtain satisfactory
Hastelloy N castings for the impellers and volutes. The initlal castings
were unsatisfactory due to defects such as cracks‘resulting from shrinkage,
inclusions, and porosity. Castings of improved quality, whieh vere accept-
able after repairs, were obtained from a second foundry. The castings were
improved by modifying the chemistry of the casting melts and by the founder
giving close supervision and attention to the details of the casting pro-
cedures. | '

Two problems were encountered during the fabrication of the hermeti-
cally sealed vessels for the drive motors. The design”originally'specified
brazing a cooling coil of stainless steel pipe to the outside of the cylin-

drical carbon steel vessel. However, because of the difference.in thermal
| expansion between the two materials, continuous attachment of the coil to
the vessel was not achieved ny'brazing. The problem was solved by welding
the coil in place. A more serious problem was encountered during the-build-
up of weld metal, "buttering,” on the inner surface of the vessel to accom-
modate the attachment of a flat head. Large laminar defects appeared in
the vessel wall in the region of the buildup. Removal of the defects by
grinding and weld repair resolved the problem. Satisfactory vessels were
obtained but at the expense of delays in delivery of the vessels and
additional expense to the fabricator. '

Shaft Annulus Plugging

During test 6 (see Table 1) the recorded trace of drive motor power
began fluctuating after 70O hr of operation with molten salt at 1200°F.

An anomalous value of gas pressure, which exceeded the supply pressure
 

 

 

 

»

"

"

¥

23

by approximately 5 psi;'was,observed in the pump tank. The test was

~therefore terminated,%and inspection of the rotary assembly revealed

the presence of solidified salt in the annulus between pump shaft and
shield plug. L oy

Subsequent analysis shoued‘that the gas flow in the lower portion
of the shaft annulus had been reversed and was upward instead of down-
ward, the proper direction. The flow reversed because the gas flow
from the liguld level indicators, although thought to be small, was
actually significant. The excess gas exceeded the throttled capacity
of the-off-gas flow line from the pump tank; consequently the excess
gas flowed upward, Jjoined the annulus purge gas, and left the pump
through the shaft seal oil leakage drain line. Small droplets of molten

salt were carried by the reversed purge flow into the lower end of the

- shaft annulus where they solidified, accumulated, and finally acted as

a brake on the shaft.‘ The chemical composition of a sample of the mate-
rial'taken from the shaft annulus vas very close to that of the salt
being circulated. The results of x-ray and petrographic examinations
of the sample indicated that the material vas carried into the annulus
as an aerosol. | -

To prevent the recurrence of this incident and to provide protection

against back diffusion, the flow rates of the gas to and from the pump

tank were monitored more closely to assure that purge gas did flow down

the'shaft annulus. The flow rate of gas from the pump tank must equal

“the flow rate of the purge down the shaft annulus plus the flow rate of
'7gas associated with the operation of the bubble—type level indicators.

Another case of shaft annulus plugging was encountered during test

| ;17 (see Table l) The plugging was indicated by a buildup of pressure

in the seal oil leakage catch basin compared with the pump tank pressure.

 The pressure differential (0 to 5 p51) thus created caused 0il to lesk
'"rout of the catch ba51n and down the outer surface of the shield plug and
.dinto the pump tank.- This leakage was detected by a hydrocarbon analyzer

sampllng the pump tank off-gas. The plug was located at the lower end
of the shaft annulus, and it was of such a nature it could be temporarily

removed by heating the system circulating salt from 1200 to 1250°F or by
 

 

2k

stopping the pump briefly and then restarting it. The pressure differ-
ential between the catch basin and pump tank would disappear, and leakage
of oil would stop as indicated by the hydrocarbon analyzer. After termi- |
nation of the test, material from the plug was analyzed and found to be
of a composition similar to the test salt. |

The original salt deposit is believed to have resulted from a
filling operation of the systéem wherein the supply of salt in the dump
tank was depleted before reaching the normal level in the pump tank.
Gas then bubbled up through-thg dip-line connecting the dump tank to the
| salt piping and rose into the pump tank, where it erupted from the surface
and splashed salt against the lower end of the shield_plug._ The tempera-
ture of the sfirface was low enough to freeze the salt and retain it.

Insufficient Running Clearances

It is normal practice to try to operate centrifugal pufips at or
near their highest efficiency. During operation along the constant sys-
tem flow-resistance curve that passes through this best-efficiency pdint,
also called the balance line (see Fig. iO), the various losses in the
impeller and volute are minimum, and the pressure distribution in the
volute is nearly uniform. This uniform distribution gives rfise torthe
minimum pet radial force on the impeller. Dfiring operation on higher
or lower lines of system flow resistance (see Fig.llo),'thé volute pres-
sure distribution becomes nonuniform, and a net radial force is exerted
on the impeller that increases_as the operating condition departs farther
from the balance line. Thus operation at off-design conditions produces
radial forces on the impeller that defléct the overhung shaft. Three
incidents of insufficient running clearance to accommodate this deflection
were encountered during operation of the MSRE'pumpé with molten salt in
the test facility. During the initial molten-salt test_(test 1, Table 1),
the prototype pump shaft seized in the shield plug. 0pération at off-
design conditions deflected the shaft sufficiently to cause rubbing of the
hot, dry shaft against the bore of the shield plug at its lower end. The
shaft was friction-welded to the plug over a length of sbout k4 in. The
radial running clearance between the shaft and the shield plug was
L3

25

ORNL-LR-DWG 72413R

 

HEAD —>

 

CONSTANT FLOW- ® |
RESISTANCE LINES

CONSTANT .
SPEED

INCREASING
LOAD

 

MSRE FUEL
CIRCUIT (DESIGN)

  
  
   
  
   

INCREASING
LOAD

oy

/<\1PUMP HYDRAULIC BALANCE LINE -
MINIMUM RADIAL FORCE ON IMPELLER

PROTOTYPE PUMP OPERATION WITH 13-in. IMPELLER |

 

 

FLOW —>

 

 

 

 

~ Fig. 10. Relationship Bgtweén Lines of Constant Flow rRes'isrtance ’
Pump Characteristic Curves, and Impeller Radial Load for Centrifugal
 

26

therefore increased from 0.010 to 0.045 in. to avoid shaft seizure at
anticipated off-design operating conditions.

During test 9, the shaft of the MSRE fuel-salt pump rubbed against
the helium purge labyrinth seal. The rubbing was detected and the pump
was stopped before seizure could occur. The diametral clearance was
0.005 in. The rubbing evidently occurred as a result of the buildup
during assembly of eccentricities in the mechanical structure of the
pump, shaft deflection due to dynamic loading, and shaft run-out. The
diametral clearance was increased to 0.010 in. |

During test 12, the impeller of the spare reactor fuel-salt pump
rubbed against the volute. Rubbing occurred when a flow of cooling air
was supplied to the exterior of the nonwetted portion of the pump tank
while the pump was being operated at 1200°F. It was found thét the
mounting of the volute was slightly skewed in the pump tank, and the
axial rumming clearance between the volute and the inlet shroud of the
impeller was less than required. Additional properly delineated axial
running clearance between the impeller inlet shroud and volute was there-

fore provided.

0il Leskage from the Catch Basin into the Pump Tank

0il leakage from the catch basin down the qutside of the shield
Plug and into the pump tank was observed in some of the molten-salt

~pump tests and during initial operation of the fuel-salt pump with

barren salt in the MSRE. The leakage path traversed a joint that was
sealed with a soft-annealed solid-copper O-ring compressed between
adjacent flat horizontal surfaces oh the bearing housing and shield
plug (see Fig. 11). Modifications were made on the spare rotary elements
for the fuel and coolant pumps for the MSRE. |

A weld arrangement was devised to seal the joint between the bearing
housing and the shield plug in a positive manner. The relationships be-
tween the pump shaft, the shaft lower seal, bearing housing, catch basin,
shield plug, and the pump tank are shown in the larger section in Fig. 11.
The insets show the portions affected before and after modification. The

modification was made on both the fuel- and coolant-salt pump spare rotary

"elements for the MSRE.
    
   
  
    
 
   
   
      

 

 

 

   

 

  

 

 

 

 

27
_ U , co e 'ORNL-DWG 66-2049
_ SOLID COPPER O-RING B ‘ BUNA N O-RING
- LOWER SEAL
CATCH BASIN "
s , LOWER SEAL
CATCH BASIN - -
SEAL WELD
BEFORE MODIFICATION " AFTER MODIFICATION .
SHAFT LOWER SEAL
L BEARING HOUSING
SEAL OIL. LEAKAGE OUT | '
\,UBE' o
#
PUMP TANK-
SHIELD PLUG- SHAFT §
‘Fig. 11. Cross Sections of Catch Basin.Region of Rotary Element Be-
fore and After Modlflcatlon to Seal the 011 Leak Passage Between Shield

| = _, Plug and Bearlng Housing.r T
jf
3
 

28

Pump Tank Off-Gas Line Plugging

 

During test 17 (see Table 1) the purge~gas flow rate down the shaft
annulus was set at b4 1iters/min to investigate plugging that had been
experienced in fhe fuel-salt pump off-gas line at the MSRE and to test
filters for possible use to prevent the plugging. The purge flow rate
on all previous tests was considersbly lower (factor ofllO or more).

At the high test purge rate some partial plugging in the pump tank off-
gas line was experienced. The plugging was caused by the solidification
of salt aerosol swépt out of the pump tank by the purge‘gas. The aerosol
is presumably generated by agitation of the salt in the pump tank by the
high-velocity salt Jets that issue from the xenon-removal spray ring.

The problem was a nuisance but did not interfere with pump operation.

Failure of Weld Attachment of Parts of Flow-Straightening Device

Test 12 (see Table 1) was terminated after the operator reported a
strange noise that he had heard only one time. A slight roughening of
the trace on the pump power recorder was also observed. Inspection
indicated that one of the three parts of a flow-straightening device .
had become detached and lodged in the impeller inlet. This caused some
damage to the inlet edges of the impeller vanes and deformed & swirl
preventer of cruciform configuiation that was located édjacent to the
impeller inlet. Figure 12 shows the posttest configuration of one of
the three parts from the straightener. Figure 13 shows the rubbing
damage to the leading edges of the impeller vanes, and Fig. 1k shows
the damage done to the swirl preventer. Figure 15 indicates the locations
in the flow straightener from which the three parts were detached. Other
than the barely perceptible roughening of the power trace, no effects of
the lodged parts on the hydraulic performance of the pump could be de-
tected. - '

The salt flow had carried the detached parts downstream through the
venturi meter and the interconnecting salt piping and upward into the
impeller inlet. The straightener parts had been welded in intermittent
fashion to the carrier pieces, as shown in Fig. 15. The straightener
itself was located just upstream of the venturi meter to straighten the
salt flow before entry into the meter.
29

 

 

 

 

 

 

 

Fig. 12. Part of Flow Straightener After Detachment and Lodging in
Impeller Inlet. S pE S A .

 

n

 
 

30

 

 

 

 

 

 

 

o

Fig. 13. Rubbing Damage to Inlet Edges of Impeller Blades. Damage
was caused by rubbing of impeller against detached part of flow straightener
that lodged in impeller inlet.
31

i

 

 

 

 

 

 

 

let.

 

 

in

 

Damage was caused by lodging of
ller - .

impe

 

in

Preventer.

 

mm&f

ghtener

1

ir
strai

 

 

 

 

 

   

=
w
Q3 ‘ _
3
m G
e S
i D o
. 4
~ M
—~ o .
. e
- o~ QO )
, L .
o
o
®
, s REE | kA o , _

 

 

 

 

 
 
 
 

 

 

 

 

 

 

 

 

 

Fig. 15.
Locations are

32

 

Failure of Weld Attachment of Parts in Flow Stralghtener.
shown from which parts were detached.
 

 

33

At this time it was decided to modify the salt piping as shown in
Fig. 16 to locate the venturi meter in the upper leg of the salt piping
and the straightener upstream of it near the outlet end of the air cooler.
The designs of the straightener and the welds joining its parts were also
modified to reduce the vibration-induced fatigue thought to be the reason
for the detachment of the three parts. The impeller and the swirl pre-

venter were replaced also.

Mark-2 Fuel-Salt Pump

- The Mark-é fuel-saltrpump represents a modification to the original
design of the fuel-salt pump to provide additional volume needed to ac-
commodate the thermal expansion of the systen fuel salt. For the original
fuel-salt pump, an overflow tank had to be installed at the MSRE to pro-
vide the additional volume. |

Although the Mark-2 pump was fabricated and Operated with salt in
the molten-salt pump test stand, 1t was never installed into the MSRE.
It is still being operated in the test stand and in April 1970 had cir-

~culated the salt LiF-BeF, -ZrF, -ThF, -UF, (68.4-24.6-5.0-1.1-0.9 mole %)

for more than 14,000 hr, mainly at 1200°F. Its performance has been
satisfactory 1n every respect, except for partlal restrictions to the
purge-gas flow that occur occa51onally in the off-gas line and in the

pump shaft annulus.

Description of Pump

 

- The Mark-2 pump has the same hydraulic components (impeller and

fvolute), bearing housing, and drive motor designs as those used in the

i original fuel-salt pump. However, the height of the pump tank was in-

 creased by 9 3/4 in. to provide 5 3/h ft3 of additional volume for the
a}thermally expanded fuel salt. The pump shaft is the same, except that

the length of the salt-wetted portion was increased a corresponding

o amount. The conflguratlon of the pump is shown in cross section 1n
- Fig. 17 |

The detailed designs of 1nternal equipment in the pump tank (i.e.,
salt splash baffles and salt spray ring) differ from those provided for
 

 

34

. ORNL-DWG 66-2048

 

 

 

 

 

 

 

 

 

 

 

  
      
   
 
    
   
  

 

 

)
DRIVE
MOTOR
- 0 t 2 3
e ]
FEET
AR
THERMAL
WELL
AIR COOLER
VENTURI

SALT :

PUMP v L T T T T ==

T .
_____________ i
-
DISCHARGE SALT FLOW
PRESSURE TENER '
STRAIGHTENER INLET PRESSURE PRESSURE
‘-B-in. P‘PE
6-in. PIPE

 

 

 

 

   

wa—— SALT FLOW

S FREEZEVAVE — |
RS ‘ MSRE FREEZE
fi FLANGE

bump
TANK

ORIFICE FLOW
RESTRICTER

 

 

 

 

 

Fig. 16. Configuration of Salt Piping in the Molten-Salt Pump Test
Stand as Modified After Failure of Weld Attachment of Parts in quW"

Straightener.
 

.

 

 

 

"

 

) SHAFT COUPLING -

35

_ ORNL-DWG 69-10459

 

 

"LUBE OIL IN

BALL BEARINGS
{FACE TO FACE)

BALL BEARINGS
{BACK TO BACK)

 

 

 

 

 

 

 

 

 

 

 

 

 

SHAFT SEAL ———

LUBE OIL OUT —
LEAK DETECTOR

GAS PURGE OUT

GAS-FILLED
EXPANSION SPACE

NORMAL OPERATING LEVEL

- me e == -

]
J BEARING HOUSING
GAS PURGE IN
T ‘ .
—SHIELD COOLANT PASSAGES
(IN PARALLEL WITH LUBE OIL)
SHIELD PLUG
‘BUBBLE TYPE
LEVEL INDICATOR
XENON STRIPPER
(SPRAY. RING} .
- o
AN = e
M-

\, f - . . J S

& — “

- J_ i’ . .A el Lo *

) - v .

— . —_—
e = = i Lo :
D—\—"—'———/Eb I
1 I
| _)

J T o

SHAFT SEAL
| ’ )
7
i)

U “—_LUBE OiL BREATHER

 

 

 

 

 

" Cross Section of Mark-2 Fuel-Salt’ Pump. -
 

36

the original tank (Fig. 1). The jets from the spray ring do not impinge
directly into—the pool of salt in the pump tank but are aimed at the
inner surface of the salt spray baffle. In addition the Mark-2 pump
tank is equipped with a buoyancy level indicator (not shown in Fig. 17),
vhich was not used in the original pump tank. - |

Hydraulic Performance

Hydraulic performance data were obtained at various pump speeds
along & constant line of flow resistance and at a constant salt ten-
perature of 1200°F. Theidata are‘superimposed in Fig. 18 on a graph
of water test performance data provided by thé vendor of the impeller
and volfité. The head values from the molten-salt data are within 2 ft

of the vendor's values.

Measurement of Undissolved Gas Content in Circulating Salt

The content of undissolved gas circulating in the salt was measured
with the pump operating at three different salt levels in the pump tank.
At the normal level and the high level, 5 3/8 in. above normal, there
was no gas detectable'in the circulating salt by use of the radiation
densitometer. At the low level, 2.4 in. below normal, a gas content of
0.1 vol;% was measured. (The radiation densitometer is described in a
previous section,) At the normal and high levels, the baffles are
evidently effective in keeping gas bubbles from being carried into the
circulating salt at the pump inlet.

Restrictions to Purge-Gas Flow

During operation of the pump, partial restrictions have been experi-
enced in the purge-gas flow passages. Examination after initial operation
revealed solid material in the off-gas line as far as 40 £t downstream
from the pump tank. It had collected in valves and other restricted
flow areas, and therefore it was difficult to maintain the pufgefgaé
flow of 4 liters/min, the MSRE design rate. A commercial filter'yas
therefore installed approximately 15 ft downstream from the pump fiéfik,
37

 

 

 

 

 

 

 

 

 

 

 

 

_ - , . o , - o ~ ORNL-DWG 70-6824
60 — = :
o ——— 1150 rpm e I
L ALLIS CHALMERS DATA o - \ "
: - : 1153 rpm
.| DATA POINTS FOR ORNL MOLTEN-SALT PUMP. -~ | . . -fh""“‘-7~ P
- PERFORMANCE AT 1200 o - - “h\i::;fl» 1164 rpm
N - — - ' 1151 rpm- \
ha
~ o0 J031 rpm
40 . <
;:._,‘ 860 rpm
— e ———
z 130 ‘ ' i L T ——
= ALLIS CHALMERS Mfg. CO. IMPELLER AND VOLUTE ;:;:::-~‘\
- 5 SIZE 8 x 63, TYPE E; IMPELLER P-482, 11.5 in. 0.D. - 861 rpm s
- . .
nt-
s 20

 

-.-‘Q\ _..5..9‘9 rpm

ol 60z
rpm
~ 80z rpm

 

10

 

 

 

 

 

 

 

 

 

 

. o0 200 400 600 800 1000 1200 1400 1600

 

Fig. 18. Hydraulic Performanqe_qf_Marku_Fuelr$qlt_qup.n' |

 

 

 
 

 

38

and there was no further plugging. A restriction'now occurs on the
average of about once per month in the pump tank off-gas hozzle or at
a valve Jjust fipstrefim of the filter. It is removed by rapping on the
line or by application of heat with a torch. |
Examination of a sample 6f the plug material revealed that it was

salt in nearly 8pherical droplet form 15 , in diameter or less. The
salt material is carried as an aerosol in the purge gas from the pump
tank gas space into the pump tank off-gas line.

 There have been eight occasions of partial plugging in the shaft
annulus (inlet purge-gas_paséage). This plugging can be cleared by
either stopping the pump momentarily and restarting it or by heating
the system salt to 1325°F for a short period (about 1 hr) and then re-
turning it to 1200°F. |

Performance of Molten-Salt Pumps in MSRE

Two molten-salt pumps, one for fuel salt and one for coolant salt,
were instelled in the MSRE. They were developed with the aid of water
tests® and the salt tests conducted in the molten-salt pump test stand,
as described above. The two pumps are identical except for the hydraulic
design (impeller and volute); the fuel pump tank has a spray ring to pro-
vide for xenon removal, whereas the coolant pump does not; and the fuel
pump is driven at 1175 rpm, while the coolant pump is driven at 1775 rpm.
Their accumulated operating statistics, up to the shutdown of the MSRE
on December 12, 1969, are presented in Table k4, which gives the accumu-
lated pump operating hours for circulation of molten salt, helium, and
the combined hours_for helium and salt when the system was at 900°F or
above. The service of the MSRE salt pumps, which began in August 1964,
was satisfactory, and the total operating times for the pumps exceeded
58,000 hr.

During operation of the pumps only one problem was encountered —
partial restriction of the off-gas flow. This problem did not inter-
fere with the operation of the MSRE but was a nuisance in that it re-
quired considerable attention from time to time. We believe that the

restrictions resulted from two sources: the freezing of salt aerosol
 

 

®

39

and the radiolytic polymerlzation of 011 in the off-gas lines Measure?
ments of the hydrocarbon content in the pump off—gas showed 1 to 2 g/day

of hydrocarbons. The source of salt aerosol is dlscussed in a prev1ous
sectlon, as is the source of the 011 Partial restrictions occurred at
the off-gas outlet nozzles of the ‘pump tanks and at other locations,
such as valve seats or other points of reduced flow ares. In all ‘other
respects, the oPeration of the salt pumps was deemed satisfactory by the
MSRE Operations Group.

Table 4. Molten-Salt Pump Operation in MSRE

 

 

Pump Process Head Flow Speed Temperature Total
Fluid (ft)  (gpm) (rpm). (°F) Hours
Fuel  Helium and 5900 30,848
. molten salt '
Molten salt 50 1200 1175 = 10001225 21,788
' Helium - e - . 100-1225 7,385
Coclant Helium and | . 2900 7,438
’ molten salt -~ . D T

AMoiten salt 78 800 1175 1000-1275 26,076

Helium . 100-1275 4,707

 

*An incident occurred with the fuel-salt pump during one salt-filling

ioperation in preparation for startup of the reactor. _The salt was forced

to an- excessively high level in’ the pump tank, which resulted in salt

'_entering the ‘shaft annulus ‘and freezing. Under these circumstances ‘the

motor output torque vas not sufficient to. turn the shaft After appli-
cation of extra heat to the: pump tank and sufflcient ‘time for- heat to

. . transfer into the frozen region, the shaft became free to rotate and the

pump—Was again operative. The filling procedures were modified and -

this 1nc1dent did not recur.
 

 

 

To)
Cbnclusions

The development and test programflproduced fuel-=and coolant-salt
pumps that, on the whole, operated satisfactorily and dependably during
the operating 1ife of the MSRE from August 196l to December 1969. The
molten-salt hydraulic performance of the pumps compared favdrdblyfwith
the  room-temperature water test performance. The pump head with molten
salt was observed to be within 2 ft, or 5%, of the water test head, and’
thié difference is within the accuracy of the instrumentation. |

The pump shaft purge was effective in protecting the:lower shaft
seal region df the fuel=salt pump from radiocactive fission products,
and the path for removal of seal o0il leakage remained opened during all
MSRE operation. The oil leakage rate for the lower shaft seals was ac-
ceptable (maximum of 36 ce/day) throughout MSRE operation.

A seal weld scheme, which Joiné'the shield plug and the bearing
housing, was developed to prevent oil leaskage in the lower seal catch
basin from entering the pump.tank. It was applied to the spare rotary
elements, which were not needed in the MSRE and therefore were never
installed.

Cdnsideration should be given to the handling of salt aerosol in
the design of salt pumps for advanced molten-salt reactor systems and
to minimizing the production of aerosol. A device should be provided
to remove the aerosol content in the purge gas and return it to the

salt system.

Acknowledgments

 

The satisfactory design, development, fabrication, and operation

- of reactor-grade molten-salt pumps for the MSRE required the efforts,
enthuSiasm, loyalty, and cooperation of more people than can be named

in this report. From this large group, recognition musfi be given to

L. V. Wilson for his efforts in the design of the pumps‘and to R. B.
Briggs, A. G. Grindell, and R. E. MacPherson for the substantial guidance
and encourééement they provided throughout the MSRE'salt pump development

program.
 

 

 

 

[ 13

10.

hl;
'_References

R. B. Briggs, MSRP Semiann. Progr. Rept. July 31, 1964, USAEC Report
ORNL-3708, p. 375; Osk Ridge National Laboratory.

‘P. G. Smith, Water Tesfi Development of the Fuel Pump for the MSRE,

USAEC Report ORNL-TM-T9, p. U7, Oak Ridge National Laboratory,
Mar. 27, 1962.

C. H. Gabbard, Thermal-Stfess and Strain-Fatigue Analyses of the
MSRE Fuel and Coolant Pump Tanks, USAEC Report ORNL-TM-T78, p. T1,
Oak Ridge National Leboratory, Oct. 3, 1962.

A. G. Grindell, W. F. Boudreau, and H. W. Savage, Development of
Centrifugal Pumps for Operation with Liquid Metal and Molten Salts
at 1100—1500°F, Nucl. Seci. Eng., T(1): 8391 (1960).

R. W. Kelly, G. M. Wood, and H. V. Marman, Development of & High-
Temperature Liquid Metal Turbopump, Trans. ASME, Series A, J. of
Eng. for Power, 85(2): 99-107 (1963).

C. Ferguson et al., Design Summary Report of LCRE Reflector Coolant
Pumps and Sump, USAEC Report PWAC-384, p. 41, Pratt & Whitney Air-
craft, Middletown, Connecticut, December 1963

0. S. Seim and R. A. Jaross, 5000'gpm Electromaegnetic and Mechanical
Pumps for EBR-II Sodium System, Second Nuclear Engineering and Science
Conference sponsored by ASME, Philadelphia, Pa., March 1114, 1957.

H. W. Savage, G. D. Whitman, W. G. Cobb, and W. B, McDonald, Compo-
nents of the Fused-Salt and Sodium Circuits of the Aircraft Reactor
Experiment, USAEC Report ORNL-2348, pp. 21?33 Oak Ridge National
Leboratory, Feb. 15, 1958

0. P. Steele III, ngh-Temperature Mechanlcal "Canned Motor" Liquid
Metal Pumps, Nuclear Engineering Science Conference sponsored by

Engineers Joint Council, Chicago, March 17-21, 1958.

R. W. Atz, Performance of HNPF Prototype Free-Surface Sodium Pumps ,

~  USAEC Report NAA-SR-h336,-Atomics International, June 30, 1960.

11,

12,

J. G. Carroll et al., Field Tests on a Radlatlon-Re51stance Grease,

‘Lubricating Eng., 18(2): 6470 (1962).

P. G. Smith, Development and Operational: Experlence w1th the. Lubrlca-
tion Systems for the Molten-Salt Reactor Experiment Salt Pumps, Oak .

lr'Rldge Natlonal Laborato;y, unpublished internal memorandum, June 1970.

13.

R. B, Briggs, MSRP Semi ann., Progr. Rept. November 1964, USAEC Report
ORNL-3708, pp. 233235, Oak Ridge National Laboratory.
1k,

15.

Lo

R. B. Briggs, MSRP Semiann. Progr. Rept. December 31, 1962, USAEC
Report ORNL.-3369 » PP. 123-124, Oak Ridge National Laboratory. 4

R. B. Briggs, MSRP Semlann. Progr. Rept. January 31, 1963, USAEC .
Report ORNL-3419, pp. 37-40, Oak Ridge National Leboratory.
 

"

83

Fuel-Salt Pump Drawings

BM-8930
F-9830
E-10965
D~1096L
F-9846

D-103k)

B-972T7

- D-9711
D~10068

F-98h1

D-10561
D-9849
~ E-9710

D-9839

D-9837

D-98LT

F-98LL
E-9843
D-10967
D-9834
D-9832
F-9845

D-9838

F-9836

E-9835

D-9033.
D-9831

D-9848

D-9850
D-9720

43

Appendix

MSRE DRAWINGS

MSRE Fuel Pump
- Assembly

Pump Tank Test Assembly
Flange Wéldmentr'

- Upper Shell Weldment

Details
Dished Head

| Volute

Bubbler Header Weldment
Lower Shell Weldment
Sprinkler Head Weldment
Thimble Weldment
Impeller

Details
 Details |
- Labyrinth Flange Weldment

Shield Plug Assembly
Details

- Motor Gulde Weldment
- Detaills |
 Piller Bar
- Shaft | , _
' ;shaft3Coblant Plug WEIdmehtfi
| ,LBearing Housing,Assembly |
_:f fBéarifig"HOusing Weldment

Upper Seal

 meeafing Clamp Ring

Modified Flexible Coupling -
Modified Oval Ring, ASA B16-20
Details ' |
 

4y

D-10067 Shield Plate

D-98L40 Details l
D-108890 Assembly: Shaft Leak Tester
D-10888 Assembly: Leakage Test Fixture
D-10887 Weldment: Leakage Test Fixture
D-10886 Details

BM-9T718 Seal, MSRE Pump

D-9718 Seal Assembly

D-9721 Seal Body Subassembly

C-9722 Seal Body

D-9720 Seal Spring Plate

B-9719 Seal Nose

BEM-9730 Universal Joint, MSRE Fuel Pump
D-9730 Universal Joint Assembly
D-9905 Details

BM-10066 Bolt Extension, MSRE Fuel Pump
D-10066 Bolt Extension Assembly

Coolant-Salt Pump Drawings

BM-10062 MSRE Coolant Pump
F-10062 Assembly

D-9837 Details

E-10966 Pump Tank Test Assenbly
D-10964 Flange Weldment

F-10063 Upper Shell Weldment
B-9727 Dished Head

D-10068 Bubbler Header Weldment
D-97T7L Volute

D-103h4k Details

D-103h44 Details

F-1006L4 Lower Shell

D-10065 Thinmble Weldment
D-9T7T0 Impeiler

D-9834 Details
 

 

oy

D-9847
D-9849
F-98LL
E-9843
D-10967
D-9833
D-9837
D-9832
F-98L45
D-9838
F-9836
E-9835
D-9831
D-9848
D-9850
D-9839
D-9720
D-10092
BM-9718
D-9718
D-9721
C-9722
D-9720
D-9T719

653 J 015

653 J.009

828 D 1hh
472 B 183

319157

ED 18399
Lho A 811

Lo A 800

ks
Lebyrinth Flange Weldment
Details | |
Shield Plug Assembly
Details

Motor Guide Weldment
Details

Details

Filler Bar

Shaft

‘Shaft Coolant Plug Weldment

Bearing Housing Assembly
Béaring Housing Weldment
Bearing Clamp Ring | |
MOdlfled Flexible Coupling
Modified Oval Ring
Tachometer Block

Details

‘Impeller Wrench Assembly

Séal, MSRE Pump
Seal Assembly

' Seal Body Subassembly

Seal Body

- Details
Seal Nose

5Fuel and Coolant Pgmp Drive-Motor Drawingé

| General Assembly
'ereneral Assefibly
  General Assembly |

Stator Lamination Details'

'  Wiring Dlagram for 6 Pole H .
E_Wiring Dlagram for 4 Pole
‘Terminal

Ball Bearing Detail
 

 

 

k72 B 233

Seal

Lubrication Stand Drawings - -

EM-41801
E-141801
E-41807
E-141803
E-41802
E-41806
D-41810
D-41808
D-41812
D-41813
D-141809
D-41811
D-4180k
D-41805
D-4181kL
E-L41815

BE-41816
D~55$73
D-555T2

Mark-2 Fuel-Pump Drawings

 

F-56300
F-56301
E-9T10
D-9839
D-9837
D-98L7
D-98L49
F-98L4L
D-10967

Lube 011 Packsge, MSRE
Piping Assembly

Support Frame

Tank Piping Subassembly
Tank Assembly

Flange, Double O-Ring Seal
Breather Line |
Pump Discharge Manifold
Details '

Filter Modification and Assembly

Supply Manifold
Return Manifold

Style "SSD" Valve Modification

General Notes
Process Piping Connections

Instrumentation Assembly and Power

Connections -
Instrument Support Tray
Flow Element (Coolant)
Flow Element (ILube)

Assembly

Test Assembly of Pump Tank
Impeller

Impeller Nut

Slinger

Labyrinth Flange

Details

Shield Plug Assembly

‘Motor Guide
 

 

 

 

)

-

D-48225

-Dg983h

D-9832
F-5630h
D-9838
F-9836
D-9833

D-9831

D-9848
D-9850
D-9720
D-10067
D-56307
D-55508

E-~k8hal

E-48L23

~ F-56302
F-56303

D-48Lop
D-48936

C-48935

B-9727
D-10964
D-56305

' D-56306

D-1034k

BM-9718

D-9718

D-9721

C-9722

~ D-9720
 B-9719

BM-9730
D-9730

T

o ~ Clamp

Seal
Filler Bar
Shaft

-Shaft Coolant Plug

Bearing Housing Assenmbly
Seal | | |
Bearing Clamp Ring

Modified Flexible Coupling

Modified QOval Ring
Details

Shield Plate

Spool Piece

XFMR Mtg. Plate
Details '

Splash Baffle Weldment
Upper Shell Weldment
Lover_Shell‘WEldment
Volute |

‘Level Indicator — Float Assembly and

Details |
Lube Oil Jet Pump Assembly and Details

36~in. Flanged and Dished Head
- Weldment Flange _
~ Capsule Guide and Latch Stop
.'_Bubblér Header Weldment
~ Details
" Seal, MSRE MK-2 Fuel Pump
| _;Seal Assembly
'  Séa1 Body Subassembly_

Seal'Body

 Seal Spring Plate
"'Seal Nose -
Universal Joint, MSRE Fuel Pump

Universal Joint Assembly
 

 

 

L8

D-9905 © Detalls |
BM-10066 Bolt Extension, MSRE Fuel Pump
D-10066 Bolt Extension
 

 

 

oy

"

21,
22,
23,
oL,
25,
26.
o7,

28.

29,
30.
31.
32.

33.

3.

35.
36.

- 37.
© 38,
39.
ko,
L.

- ke,

- 43,
Lk,

ks,
L6.
L.

R.

T'
W.

F. Appler

. J. Ball

F. Bauman
E. Beall
Bender

. E. Bettis

. S. Bettis

F. Blankenship
. Blumberg

. G. Bohlmann

J. Borkowski
B. Briggs

W. Cardwell
J. Claffey
W. Collins
L. Compere
H. Cook

. W. Cooke

B. Cottrell

L. Crovley

L. Culler

. H. DeVan
. R. Distefano
. Jd. Ditto

A, Doss
P. Eatherly
R. Engel

P. Epler

. P. Fraas

H. Frye

C. Fuller
H. Gabbard
B. Gallaher

- R. Grimes . S

G. Grindell
H. Guymon
0. Harms

N. Haubenreich -

E. Helms

G. Herndon
C. Hise _
W. Hoffman .
P. Holz
Houtzeel

I;. Hudson

R. Huntley

ko

Internal Distribution

 

LS.
k9.

50.'

51.
52.
~ 53.
5k,
55«
56.
5T
58,
59.
60.

61..

62.
63.
6k.
65.
66.
67.
68.
69.
T70.
T1.
2.
- T13.

.

T6.
77
T8.
T9.
8o.
81,
82,
. 83.
8L,
85.

- 87.

89.
~90.
91,

92.

o%!

+o

- 86. .

ORNL-TM-2987

H. inouyé

=

. H. Jordan

R. Kasten

. Kerlin

Keyes

. Koger

Korsmeyer

. Krakoviak

. Kress

. Krewson

. Lindauer

. Lundin

. Lyon

MacPherson

. McCoy

. McCurdy

. McGlothlan

McNeese

. McWherter
Metz

« Meyer

. J. Miller

L,. Moore

. M. Perry

Richardson

C. Robertson

. W. Rosenthal

" C. Savage

. W. Savolainen

. H. Shaffer

e
24

.

?lfllEi?%C)EiE!fi!FiUfiE:UJP4H1

GrEufoXrdrrHqQPORdHdYIY R DSGHEHEDY
n

‘M. J. Skinner

G. M. Slaughter
A. N. Smith

P. G. Smith

I. Spiewak

R. D. Stulting
D. A. Sundberg
E. H. Taylor

R. E. Thoma

D. B. Trauger
A. M. Weinberg
J. R. Weir

J. C. White

G. D. Whitman
L. V. Wilson

Gale Young
H. C. Young
 

 

95-96.
97-98.
99-102.

103.

10L.
105.
106.
107.
108.

109.
110.

111.

112.
-113.

11k,
115.
116.
117.
118.
119.
120.
12].
122.
123-137.

50

 

‘Internal Distribution (continued)

Central Research Library
Y-12 Document Reference Section

‘Laboratory Records Department

Laboratory Records Department (RC)

External Distribution-

 

- C. E. Anthony, Westinghouse Electro Mechanical Division,
. Cheswick, Pa. 15024

R. N. Bowman, Bingham-Willamette Company, Portland, Oregon

97200

Arthur Bunke, Byron Jackson Pumps, Inc., Los Angeles, Calif.

90000

E. J. Cattabiani, Westinghouse Electro Mechanical Division,

Cheswick, Pa. 1502h ,

D. F. Cope, RDT, SSR, AEC, ORNL o

Charles R. Domeck, USAEC, Washington, D.C. 20000

David Elias, USAEC, Washington, D.C. 20000 '

A. Giambusso, USAEC, Washington, D.C. 20000 :
Kermit Laughon, USAEC, OSR, ORNL 1
Liquid Metal Engineering Center, c/o Atomics International,

P.0. Box 309, Canoga Park, Calif. 91303 (Attention: -
R. W. Dickinson) |

C. L. Matthews, USAEC, OSR, ORNL

T. W. McIntosh, USAEC, Washington, D.C. 20000

C. E. Miller, Jr., DRDT, USAEC, Washington, D.C. 20000

M. A. Rosen, DRDT, USAEC, Washington, D.C. 20000

H. M. Roth, USAEC, Oak Ridge Operations '

J. J. Schreiber, DRDT, USAEC, Washington, D.C. 20000

M. Shaw, USAEC, Washington, D.C. 20000

W. L. Smalley, USAEC, Oak Ridge Operations

Laboratory and University Division, ORO

Division of Technical Information Extension (DTIE)