ORNL-TM-1993.txt

 

 

RECEIVED BY. DTIE SEP 2§ 1967 . MAST

OAK RIDGE NATIONAL LABORATORY
operated by

UNION CARBIDE CORPORATION
NUCLEAR DIVISION
for the
U.S. ATOMIC ENERGY COMMISSION
ORNL- TM- 1993

FTEENY
[ YW |

 

   

EXPERIENCE WITH HIGH-TEMPERATURE CENTRIFUGAL PUMPS IN
NUCLEAR REACTORS AND THEIR APPLICATION TO
MOLTEN-SALT THERMAL BREEDER REACTORS

P. G. Smith

NOTICE This document contains information of a preliminary nature
ond was prepared primarily for internal use at the Oak Ridge National
Loboratory. It is subject to revision or correction and therefore does

not represent a final report.

BISTRIBUTION OF THIS DOCUMENT, 1S UNLIMUIER
 

 

 

LEGAL NOTICE

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

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

A. Makes oany warranty of representation, expressed or implied, with respect to the accuracy,
completeness, or usefulness of the information contained in this report, or that the use of
any information, apparatys, method, or process disclosed in this repert may not infringe
privately owned rights; or

B. Assumes any licbilities with respect to the use of, or for damages resulting from the use of
ony 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

contractor of the Commission, or employee of such contractor, to the extent that such employee

or contractor of the Commission, or employeea of such contractor preparss, disseminates, or
provides access to, any information pursuant to his employment or contract with the Commission,

or his employment with such contractor.

 

 

-

 

 

 

 
ORNI!-TM-197._)

Contract No. W-Th05-eng-26

REACTOR DIVISION

EXPERIENCE WITH HIGH-TEMPERATURE CENTRIFUGAL PUMPS IN

NUCLEAR REACTORS AND THEIR APPLICATION TO

MOLTEN-SALT THERMAL: BREEDER REACTORS

Smith

G.

P.

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CONTENTS

Long=Shaft PUmD seceesvsereareaccsscsnssonnsss reseans vesnse

General Descriphbion s.cciereerrevrencsscnscssnossnnsnss

Sodium Pumps for the Hallam Nuclear Power Reactor ....

Primary Sodium Pumps for the Experimental Breeder

ReaCtOI"'"Q e 8 28 s s s 0w B OB PSRN G e s e 6 000008 80

Sodium Pumps for the Enrico Fermi Reactor ....eececees

Development Sodium Pump for the UKAEA Prototype
Fast Reactor ..veieveeriiriteneeteessesonancananssens

Sodium Pumps for the Rapsodie Reactor ..cee... seesoos
Sodium Pumps of the Sodium Test Facility at LASL ...
Molten-Salt Pump Operated at ORNL «v.ievvoocovvsosesncs

Large Reactor Sodium Pump Proposed for Development
DYy USAEC svcvnreeensosssosonsssctscsssesancossasssses

Short-Shaft Pump .....cc00.. Puseseerrenstraressenns cer s
Sodium Pumps at the SRE ciccveene cestesasssecesesasaeen
General Description of ORNL Pumps ...cecoccsssvscessne
MSRE Fuel and Coolant Salt Pumps ...eecerevrcnccoseass

PROBLEMS ANTICIPATED WITH LARGE PUMPS FOR MOLTEN~SALT BREEDER

Dynamic Response of the Rotary Components Assembly .eevvese
Bearings ....... Csastecssssevraenecarrsacseseassansaes ceeasos
Thermal and Radiation Damage Protection ..evceccocsese ceoes
Shaft Seal sieeuireieeieereeeracoesossssccsoansas sieeasacses
Hydraulic Design .cesecoverssescaecanssascosnacossosaoessnanes
Fabrication and Assembly ..veecrcoervsassoscosssesocassescs .

11

11
15

17
18
21
2k

26

o6
27
30

33

33
35
36
37
37
38
iv

CONTENTS ( continued)

oooooooooooooooooooooooooo

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Page
38

39
Lo
Figure 1

-

10

11

12

LIST OF FIGURES

Sodium Pumps, Hallam Nuclear Power Facility
(from Ref. 5).

Primary Sodium Pump Rotary Assembly, Hallam
Nuclear Power Facility
(courtesy of Atomics International).

Primary Sodium Pump, Experimental Breeder
Reactor—2
(from Ref. 5).

Primary Sodium Pump, Enrico Fermi Fast Reactor
(from Ref. APDA-12L, January 1959).

Secondary Sodium Pump, Enrico Fermi Fast Reactors,
(courtesy of Atomic Power Development Associates).

Development Sodium Pump, UKAEA Prototype Fast
Reactor
(from Ref. 9).

Primary Pump for Rapsodie Reactor
(from Ref. kL),

Primary Pump for Sodium Test Facility (LASL).

Molten-Salt Pump With One Molten-Salt Lubricated
Bearing (ORNL).

Large Sodium Pump Concept Proposed for Development
by USAEC
(from Ref. 19).

Main Primary and Secondary Pumps, Sodium Reactor
Bxperiment

(from Ref. T).

MSRE Fuel Salt Pump (ORNL).

Page

12

13

14

16

19

20

22

25

28

29
Table

1

vi

LIST OF TABLES

List of the Pumps and Their Distinguishing
Features.

Characteristics of Reactor Sodium Pumps,
Long-Shaft Sump Pumps.

Characteristics of Development Pumps, Long-
Shaft Sump Pumps.

Sodium Pump Operating Parameters, Hallam Nuclear
Power Facility.

Operating Characteristics, Molten-Salt Pump With
One Molten-Salt Lubricated Bearing.

Characteristics of Short-Shaft Sump Pumps at ORNL.

Endurance Operation of Short-Shaft Sump Pumps.

Pumps for Molten-Salt Breeder Reactors.

Page

10

23

3t
32
3k
EXPERIENCE WITH HIGH-TEMPERATURE CENTRIFUGAL PUMPS IN
NUCLEAR REACTORS AND THEIR APPLICATION TO
MOLTEN~-SALT THERMAL BREEDER REACTORS

P. G. Smith

ABSTRACT

Design features, development problems, and operating
experience have been compiled for ligquid-metal and molten-
salt circulating pumps used in variocus nuclear reactors
and test facilities. The compilation was made to search
out the problem areas and to select suitable combinations
of features for the circulating pumps required by each of
the three molten-salt systems in the proposed molten-salt
thermal breeder reactor. The pumps are divided into two
configurations: the "short-shaft pump" and the "long-
shaft pump." The short-shaft pump is favored for the cool-
ant salt system, and the long-shaft pump is favored for the
fuel-and-blanket salt systems.

INTRODUCTION

As part of a continuing program for development of molten-salt
reactors, the Oak Ridge National Laboratory (ORNL) is working on the
design of molten-salt thermal breeder reactors. A conceptual design
of a 2225 Mw(t) Molten Salt Breeder Reactor!’® (MSBR) has been pre-
pared, and a 100-150 Mw(t) Molten-Salt Breeder Experiment (MSBE) has
been proposed as the follow-on to the 7.5 Mw(t) Molten-Salt Reactor
Experiment® (MSRE). One version of the MSBR consists of four modules
each of 556 Mw(t); and the MSBE consists of a single, reduced-scale
module. Each module has three molten-salt systems, the fuel, blanket,
and coolant; and each system requires a salt pump. The fuel and blanket
salt systems are contained in an oven that is maintained at temperatures
varying from 1050-1150°F, and they are so arranged that the discharge
and suction connections for the pumps are located well below the oven

ceiling and very near the nuclear core. The coolant salt system, in
which little radiocactivity is expected, is contained in a separate oven —~
that is maintained at 900-1000°F; and it is so arranged that the dis-

charge and suction connections for the pump are located very near the

ceiling.

A survey of the experience with large pumps for high-temperature
fluids has been made 1o assist in the design of pumps for the molten-
salt breeder reactors. Descriptions, cross section drawings, and photo-
graphs, tables of pump parameters, and accounts of significant operating
problems have been obtained for specific pumps of interest to the survey
from various reactor installations. The pumps are classified into two
configurations: "short-shaft pump" and "long-shaft pump." The pumps
included are: +the primary and secondary system sodium pumps for the
Hallam Nuclear Power Facility®® (HNPF), the Enrico Fermi Reactor,% S
and the Sodium Reactor Experiment®:7:8 (SRE); the primary system sodium
pumps in the Experimental Breeder Reactor—2%*% (EBR-2); the sodium pump
being developed for the Prototype Fast Reactor’ (PFR) by the United
Kingdom Atomic Energy Authority (UKAEA); the sodium pumps of the 10 Mw

experimental circuit for the Rapsodie reactor at the Cadarache installa-
tion in France%:19,11 the sodium pumps of the 2000-Kw Sodium Test Facility
at Los Alamos Scientific Laboratoryl®,18,14 (LASL); the fuel and coolant
salt pumps for the MSRE;15,1€ other elevated temperature pumps developed
at ORNL;*?218 and the large sodium pump (50,000 to 100,000 gpm) proposed
for development by the United States Atomic Energy Commission (USAEC)
for sodium-cooled fast breeder reactors.*® All centrifugal pumps known
to have been used in sodium-cooled and molten-salt nuclear reactors are
included in the survey.

The problem areas anticipated for the two pump configurstions in
the molten-salt breeder applications are discussed briefly, and tentative
conclusions are reached on a choice of pump configuration for each of the

salt systems.
PUMP DESCRIPTIONS AND OPERATING EXPERIENCE

The pumps included in this survey are described as mechanical,

free-surface, centrifugal, vertical-shaft, sump pumps. They are -~
subdivided into two groups: those that have a long shaft with at least
one shaft support bearing located in the pumped fluid, and those that
have a short shaft with the impeller overhung. The first group (here-
after referred to as long-shaft pump) includes reactor sodium pumps in
the HNPF, EBR-2, and Enrico Fermi systems; the experimental development
sodium pump for the PFR by UKAEA; the large sodium pump proposed for
development by the USAEC; the sodium pumps for the Rapsodie reactor in
France; the sodium pumps used in the Sodium Test Facility at LASL; and
one molten salt pump that was operated at ORNL.2® The second group
(hereafter referred to as short-shaft pump) includes the remainder of the
liquid-metal and molten-salt pumps that were developed and operated at
ORNL, and the main and auxiliary sodium pumps of the SRE. The distin-

guishing features of each pump are listed in Table 1.

Long-Shaft Pump

 

General Description

 

The pumps in this group have a shaft support adjacent to the im-
peller provided by a Journal bearing that is lubricated with the pumped
fluid. This permits the use of long shafts to separate the drive motor
and its sensitive electrical insulation and hydrocarbon lubricant from
intense radioactivity and high-temperature. 1In addition to the distance
effect, the separation provides space to accommodate radiation shielding.

The pumps that were used to circulate high-temperature sodium in
primary and secondary nuclear reactor systems are listed in Table 2, with
pertinent design parameters and operating experience. Table 3 provides

design and operational information for development pumps.

Sodium Pumps for the Hallam Nuclear Power Facility

The HNPF, a graphite-moderated, sodium-cooled reactor, designed
for 256 Mw(t), required three sodium pumps in both the primary and
secondary systems. The same hydraulic designs were used for the single-
suction radial.-impeller and vaned diffusers in both the primary and

secondary pumps (Figs. 1 and 2). A conventional oil-lubricated ball
Table 1. List of the Pumps and Their Distinguishing Features

Type Pump

Distinguishing Features

 

Long Shaft Pumps
Sodium pumps for the Hallam Nuclear Power Facility
Primary sodium pumps for the Experimental Breeder

Reactor ~2

Sodium pumps for the Enrico Bermi Reactor

Development sodium pump for the UKAEA Prototype
Fast Reactor

Sodium pumps for the Rapsodie Reactor

Sodium pumps for the Sodium Test Facllity at LASL

Molten salt pumps opersted at ORNL

Large reactor sodium pump proposed for development
by USAEC
Short Shaft Pumps
Liquid metal and molten salt punmps developed at ORNL

Sodium pumps for the SRE

Relatively long shaft, at least one bearing lubri-
cated with pumped fluid.

Mechanical shaft seal, one sodium lubricated hydro-
static bearing.

Hermetic containment of motor, one sodium lubricated
hydrostatic bearlng.

Mechanical shaft seal, primary pumps have two sodium
lubricated hydrostatic bearings, secondary pumps
have only one.

Mechanical shaft seal, one sodium lubricated hydro-
static bearing.

Mechanical shaft seal, one sodium lubricated hydro-
static bearing. '

Mechanical shaft seals, three sodium lubricated hydro-
dynamic bearings. Primary pump - 2 stages; secondary
pump - L4 stages.

Mechanical shaft seal, one molten salt lubricated
hydrodynamic bearing.

Mechanical shaft seal, one sodium lubricated hydro-
static bearing.

Short shaft, impeller oVerhung.

Mechanical shaft seal, impeller overhung.

Shaft freeze seal, impeller overhung, shaft extension
used to remove motor from radiation field.

 
Teble 2. Characteristics of Reactor Sodium Pumps, Long Shaft Sump Pumps

 

 

- Hallam EBR2 Enrico Fermi
Primary System Pumps
Design
Type Centrifugal Centrifugsl Centrifugal
Free-surface Free-surface Free-surface
Bumber of units 3 2 3
Capacity, gpm 7200 5500 11,800
Dynamic head, £t 160 200 310
Design temperature, °F 1000 800 1000
Motor speed, rpm 900 1075 900
‘Motor power, hp 350 350 1060
Sealing arrangement Mechanical Hermetically sealed Mechanical
Shaft sesl Drive motor Shaft seal
Material 30k gs 304 ss 304 ss
Type of speed control Eddy current Variable freq. and Wound rotor motor
coupling voltage w/liquid rheostat
Manufacturer Byron=-Jackson Byron-Jackson Byron-~Jackson
Operation
Sodium temperature, °F 300~1000 TO0 500-600
Sodium flow per pump, gpm Up to 7200 Ty (o} 900-11,800
Time per pump, hr 20,0002 12,000° 26 ,000-28,500°
Secondary System Pumps
Design
Type Centrifugal A-C linear Centrifugal
Free-surface Induction Free-surface
Number of units 3 1 3
Capacity, gpm T200 6500 13,000
Dynamic head, ft 170 - 142 100
Degign temperature, °F 1000 700 1000
Motor speed, rpm 900 1180 (MG set) 900
Motor power, hp 350 500 (MG set) 350
Sealing arrangement Mechanical Total metal Mechanical
Shaft seal Enclosure Shaft seal
Material 304 ss 304 ss 2 1/4 Cr-1% Mo
Type of speed control Eddy current Variable voltage Eddy current
coupling (MG set) coupling
Manufacturer Byron-Jackson General Electric Byron-Jackscn
Operation
Sodium temperature, °F 300~1000 - 500
Sodium flow per pump, gpm Up to T200 “— Up to 13,000
Time-per pump, hr 19,0008 - 17,000-23,000°

 

STotal. operation per pump, facility discontinued.

brotal operation per pump as of January 18, 1967.

CPotal operation per pump as of April, 1967.
dElectromagnetic pump, for information only.
 

 

Teble 3. Characteristics of Development Pumps, Long Shaft Sump Pumps
Prototype Fast 10 Mw Test Loop LASL Sodium Teset Fast Breeder
Reactor Rapsodie Moltez(:OIS‘f.lmt Pump Facility Reactor
{UKAEA) ( France) (Los Alamos) (USARC)
Primary System Pumps
Design
Type Centrifugal Centrifugal Centrifugal Centrifugal Centrifugal
free~-surface free-surface free-gurface free-surface free-surface
Number of units 1 1 1 1 (2-stege) 1
Capacity, gpm 7100 1650 260 230 50,000~-100, 000
Dynamic head, ft 150 105 50 50 300
Design temperature, °F 150 1200 1350 850 8001200
Motor speed, rom 100500 1100 1400 1675 890
Motor power, hp 475 72 -—-- T 1/2 6000
Sealing arrangement Mechanical Mechanical Mechanical Mechanical Mechanical
shafi seal shaft seal shaft seal shaft seal shaft seal
Material 321 s8 316 sa Inconel 300 series ss ———
Type of speed contrcl Comprutator ac motor Ward Leonard -——- Electromagnetic -——
v/induction regulator system drive
Manufacturer -——- Hispano-Suiza —— Byron-Jackson ——
Operation
Pumped fluid Sodium Sodium Molten-Salt Sodium ——
Temperature, °F Up to 750 Up to 1022 11.00~-1350 Up to 850 -
Flow per pump, gpm 1&000;7100 2000 o ll-5~—960c 230 4 ———
Time per pump, hr 7000 12,000 13,600 11,920 -—
Secondary System Pumps
Deslgn
Type - Centrifugal - Centrifugel -
free-surface free-surface
Number of units -—- 1 —— 1 (L-stege) —
Capacity, gpm --- 1675 - 230 -~
Dynamic head, ft -—- 59 - 110 -
Decign temperature, °F _—— 1200 — 550 -
Motor speed, rpm -a- 875 - 1675 -
Motor power, hp ——- 15 —— i0 -—-
Sealing arrangemesnt - Mechanical —-—- Mechanical ——-
shaft seal shaft seal
Material - 316 ss - 300 series ss -
Type of speed control ——— Ward Leonard —— Electrodynamic -—
system drive
Manufacturer —-— Hispano-Suiza ——— Byron-Jackson ———
Operation
Pumped fluid -—- Nax -— Sodium ———
Temperature, °F --- Up to 1022 - Up to 550 ——
Flow per pump, gpm -—— 2000 -—— 230 a ———
Time per pump, hr - 12,000 —- 13,474 ——

 

“latest published information, May 1967, Nuclear Engineerifg.
Ppotal operation as of April 1965.

“Potal as of ‘Septent:er 1967.

d'.l'ot.e;l operation, facility discontinued.
ORNL-DWG 67-2568R

 

 

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HYDROSTATIC
BEARING
IMPELLER J —————— WEEP HOLES

 

Fig. 1. BSodium Pumps, Hallam Nuclear Power TFacility (From Ref. 5) .
 

Hallam Nuclear Power

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1

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Fig.
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bearing supported the upper end of the pump shaft. Shaft seals con-
strained oil from leaking into either the sodium system or the atmosphere.
A sodium-lubricated hydrostatic bearing supported the lower end of the
pump shaft. The drive motor was located outside the reactor system
primary containment. The shaft seals in the pumps were a part of the
system containment. No shaft-annulus gas purge was used with these pumps.
The pump and piping comprising a system were preheated before sodium was
introduced. The preheating was accomplished with electrical resistance
heaters, which were attached to the exterior of the sodium-wetted parts

of the pump and piping.

Each of the three primary sodium pumps operated for approximately
20,000 hr, and each of the secondary pumps operated for approximately
19,000 hr. The speed-dependent operating parameters for both the primary
and secondary pumps are presented in Table L.

Initially the sodium level in the primary pump casing dropped below
normal when the pump was operated at flow rates above 60% of design and
with the system resistance to flow lower than the design value of 160 ft
at 7200 gpm.*! Analyses and tests indicated that the flow rates of
various sodium leakages into the pump casing were less than the outflow
rate, thus lowering the sodium level in the casing. The problem was
resolved by plugging four of the eight balancing holes in the impeller,
which reduced the flow rate out of the casing.

The secondary pumps experienced binding of the rotating element
caused by heavy wearing of the close running-clearance surfaces on the
impeller wear rings, the sodium-lubricated bearing, and the impeller
rim and casing inner diameter. The difficulty was traced to extranecus
materials in the close running clearances and thermal distortion of the
pump casing. The successful corrective actions that were taken included
filtering the circulating sodium in a bypass loop, forced cooling the
outer pump casing, and increasing the running clearances of both the
upper and lower wear rings.

A prototype of the Hallam pumps®®was operated for 800 hr at tem-
peratures of 350—-1000°F, speeds of 227—1135 rpm, and flows up to 9000

gpm.
Table L4,

Sodium Pump Operating Parameters, Hallem Nuclear Power Facility

 

 

 

Run Number
Parameter Units
1L 2 3 h 5 6
Primary Pump
Pump speed rpm 316 360 498 590 ' 620 6L2
Sodium flow 1b/hr 1.h2 (108 1.67 (102 2.30 (0P 2.8 (108 3.04 (0P 3.13 (10F
Pump head ft 19.3 24.3 48.0 68.7 76.7 81.5
Hydraulic work ft-1b/min 4.56 (L0F 6.76 (L0¥ 18.4 (10 32.3 (10F 38.8 (10 L42.5 (10
Pump output power hp 13.8 20.5 56 .4 97.9 118 129
Pump input power hp 31 38 78 127 1hh 158
Pump efficiency % L5 54 T2 T7 82 82
Motor input power hp 101 111 160 202 228 ohp
System efficiency % 1L 18 35 Lk 52 53
Secondary Pump

Pump speed rpm 260 462 416 Lo 508 51k
Sodium flow 1b/hr 1.30 (10 1.60 (10 =2.02 (10Ff 2.35 (10 2.48 (10F 2.60 (10)6
Pump head ft 20.4 64.7 45.1 61.6 68.0 73.2
Hydraulic work ft-1b/min L.4k2 (10F 17.3 (0P 15.2 (10F 2h.2 (10F 28.1 (10F 31.7 (LOP
Pump output power hp 13.4 52.5 L6.1 T3.4 85.1 96.0
Pump input power hp 25 72 6L 99 107 118
Pump efficiency % 53 T3 T2 T4 80 81
Motor input power hp 102 157 179 199 206 o2k
System efficiency % 13 33 26 37 41 43

 

o1
Sodium Pumps for the Experimental Breeder Reactor—2

 

The EBR-2, an experimental fast breeder reactor designed for 62.5
Mw(t), uses two centrifugal pumps in the primary sodium system (Fig. 3)
and an ac linear induction pump in the secondary system. The upper end
of the primary pump shaft is supported by the motor bearings, and the
lower end is supported by a sodium-lubricated hydrostatic bearing. The
motor is enclosed in a hermetic vessel, which is part of the reactor con-
tainment; and it is protected from the intrusion of sodium vapor by 2
purge of argon gas that flows downward through close running clearances
in the pump shaft annulus.

The primary pumps are located within the primary vessel and are
preheated to 250-275°F by tubular resistance heaters attached to the
core tank.

Each of the two primary sodium pumps has been operated for 12,000
hr. During initial operation the pump shaft rubbed against the shaft
labyrinth. This problem was resolved sgtisfactorily by installing new
pump shafts that had been subjected to proper stress-relief heat treat-
ment. In addition, the labyrinth radial running clearance was increased
from 0.017 to 0.129-in.

One pump would not restart in a normal fashion following a shutdown
that occurred after 4LL4OO hr operation. Manual movement of the shaft pre-
sented a "spongy" feel, as might be caused by a sodium oxide buildup.
The pump was restarted after the shaft-impeller assembly was raised
sufficiently with the shaft drawbolt to free it.

A prototype pump’® was operated for 16,000 hr during sodium pump
development tests at temperatures up to 900 °F, speeds up to 1750 gpm,
and flows up to 6500 gpm.

Sodium Pump for the Enrico Fermi Reactor

This fast breeder reactor designed for 430 Mw(t) requires three
sodium pumps (Fig. 4) in the primary system and three sodium pumps
(Fig. 5) in the secondary system. Fach primary pump has two sodium-
lubricated hydrostatic bearings, and each secondary pump has only one

such bearing. The upper end of the primary pump shaft is attached to
ORNL-DWG 67-2569

MOTOR COOLING
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—— HYDROSTATIC BEARING

 

IMPELLER

ANTI-VORTEX
BAFFLE

DISCONNECT

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Fig. 3. Primary Sodium Pump, Experimental Breeder Reactor-2
(From Ref. 5).
13

    
  
   
  

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SHAFT SEAL

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231t 5% in. LEVEL

IMPELLER

5-f1 6-in.DIAM
PUMP TANK

30 ~-in.
INLET

 

B

ORNL~-DWG 67-2570R

 

 

 

 

 

 

16-in. DISCHARGE

 

<—}— MOTOR
' 1 SHAFT
t
|
!
?i
f '

e PUMP

SHAFT

-
£,
st
N -

 

———

HALF SECTION OF SHAFT SEAL

Fig. 4. Primary Sodium Pum.p5 Enrico Fermi Fast Reactor

(From Ref. APDA-124, January 1959
14

ORNL-LR-DWG 57847R

 

  
  
  
  
   

350-HP 900 RPM MOTOR

AIR-COOLED EDDY-CURRENT COUPLING

 

SHAFT SEALS 8 BEARINGS

COOLANT HOUSING

5ft6in.

  
   
    
  

BEARING

LEAK-OFF OPERATING LEVEL

BEARING

 

DISCHARGE

SUCTION

Fig. 5. BSecondary Sodium Pump, Enrico Fermi Fast Reactors ,'
(Courtesy of Atomic Power Development Associates).
which are oil lubricated. GShaft seals are applied to the bearing at the
upper end of the shaft to constrain the lubricant from leaking into the
atmosphere or the sodium system. The radial force that acts on the im-
peller is minimized by discharging sodium at four symmetrical ports
around the diffuser casing. The impeller is of the mixed flow type.

The pump is driven by a L475-hp, ac commutator motor, which is contrclled
with an induction regulstor and is capable of continucus speed variation
between 10 and 100% of design speed.

The pump tank and loop are surrounded by a mild steel Jjacket that
forms an annulus for the purge of hot or cold air for preheating or cool-
ing. The jacket also serves as secondary containment to provide protec-
tion in the event of sodium leakage. Air is heated by finned electrical
resistance heaters and is circulated through the annulus to provide pre-
heat to LOO°F.

This pump has operated satisfactorily for 7000 hr and was removed
from test twice for inspection. It was subjected to 300 starts and
stops and has been operated at speeds between 10 and lOO% of design
values at sodium temperatures up to 750°F. During cperation the oil
leakage past the shaft seals decreased from 1 to ~ 0.2 cnf /hr.

During disassembly some difficulty was encountered in loosening
flange bolts and in separating the faces of flanges that had been immersed
in the sodium. It was necessary to heat these components above the melt-
ing point of sodium to perform the loosening and separation; however, the
surfaces of the components showed no signs of distress. The pumps for
the PFR will be supplied with provisions for Jack bolts to assist in the
separation of flange faces. Also, an impeller with double entry is being

considered to provide a greater margin for cavitation-free operation.

Sodium Pumps for the Rapsodie Reactor

These pumps (see Table 2 for design conditions) are similar to the
FBR-2 and Fermi pumps in many aspects.* The important differences are
the arrangement of the discharge and suction that eliminates the com-
plexity of the discharge manifolding, and the arrangement of the sodium-

lubricated hydrostatic bearing that has the sodium supplied to pockets
18

on the journal rather than on the bearing sleeve. A cross section of

the pump is shown in Fig. 7. The shaft is supported by two bearings:

the sodium-lubricated bearing (mentioned above) located just above the
impeller, and an upper roller bearing that consists of two thrust races
placed Jjust below the motor ccupling. The latter bearing is lubricated
with oil. Means are provided for purging helium through a labyrinth

seal around the shaft to prevent diffusion of sodium vapor along the
shaft. The pump tank contains a sheath casing of stainlegs steel, through
which hot nitrogen is circulated for preheating.

The experience as of April 1965 consisted of approximstely 12,000 hr
operation each for the primary and secondary pumps. They have been oper-
ated at temperatures up to 1022°F and at flows of approximately 2000 gpm.
Operation with the secondary pump has been with NaK rather than sodium.

The main difficulties experienced with the pumps have been with
defective operation of the hydrostatic bearings. Adjustments have been
made in clearances and the length-to-diameter ratio. In the case of
clearances, it has been necessary to increase the clearance. Other dif-
ficulties were experienced with defective operation of the check valve in
the discharge line, contamination in the form of oxides, and thermal dis-
tortions. Problems that had to do with vortexing and gas entrainment were

found and solutions were provided during water tests.

Scdium Pumps of the 2000 kw Sodium Test Facility at LASL

The Sodium Test Facility,'® which LASL operated, contained two sodium
circuits, each of which used a vertical centrifugal pump (Fig. 8) for cir-
culating the sodium. These pumps were two-and four-stage pumps with the
shafts supported by three socdium-lubricated hydrodynamic bearings and an
oil-lubricated bearing. The shaft lengths are approximately 10 1/2 ft on
the primary pump and approximately 9 1/2 ft on the secondary pump. The
impellers are located Jjust above a sodium-lubricated hydrodynamic bearing
that supports the shaft at the lower end. The other two sodium bearings
are separated by 45-in. on the primary and 34-in. on the secondary, and
they are above the impellers. The oil-lubricated bearing is near the

upper end of the shaft. It consists of a duplex pair of ball bearings,
MGOTOR fl

COUPLING

 

 

 

ORNL-DWG 67-7791

 

 

 

ROLLER BEARINGS

 

MECHANICAL SEAL

 

 

&fl
N
Y

 

 

SHIELDING 7.‘ —
N ¢
-
"y
THERMAL SHIELD
HOLLOW SHAFT _L‘

 

HYDROSTATIC -
BEARING :

 

 

 

 

IMPELLER

CHECK FLOAT

 

§.
1__“1
Ni

PREHEATING
GAS

SODIUM
LEVEL

14 f+¢

Qin.

 

Fig. 7. Primary Pump for Rapsodie Reactor (From Ref. 4).
20

CRNL-DWG 6T7-T792

-DRIVE MOTOR SUPPORT
--RUBBER GASKET

 

OIL LEVEL
INDICATOR
LOOKING N
DIRECTION OF
ARROW “A"

 

1.5 gai
t gal

_~—PLASTIC GLASS
-Q-A— - | O

 

         

T Ol INLET

OiL DRAIN, OIL QUTLET

COOLING JACKET

QUTLET

 

 

 

 

 

 

 

      

et

e

&

OIL RESERVOIR DRAIN
AND
RECIRCULATION LINE

O INLET

"’(""‘-Iv[_“"'"

(N
e

—

OIL COOLING JACKET

INLET —

 

 

 

 

 

“w sacm. AHTONGDIS
_E\m w.v AdY AN

=
fa
"

 

 

Primary Pump for Sodium Test Facility (LASL).

Fig. 8.
2l

mounted back to back. Shaft mechanical seals are used to contain the
oil.

The pumps served very satisfactorily throughout the life of the
facility. The primary pump operated for 11,920 hr at temperatures up
to 850°F, and the secondary pump opersted 13,47hk hr at temperatures up
to 550°F. The pump design characteristics are listed in Table 3.

The oil-lubriczted shaft seals performed well with an oil leakage
rate of 1-5 c® /day.}'® After 10,700 hr of operation, the oil-lubricated
shaft seal on the primary pump was replaced with a helium-lubricated
seal. The helium consumption due to leakage was unsatisfactorily high
after 150 hr of operation. Modifications were made and the seal was
returned to service. The leakage rate was 10 scf/day. After 1030 hr
operation the seal failed and again leaked helium excessively.l®* The

program was then discontinued.

Molten-Salt Pump Operated at ORNL

This pump,?® Fig. 9, is similar to the scdium pumps; but it is
smaller. The pump shaft is supported at the lower end with a molten-
salt-lubricated hydrodynamic journal bearing and at the upper end by an
oil lubricated ball bearing. The sleeve of the molten-salt-lubricated
bearing is gimbals mounted. Shaft seals are applied tc the upper bear-
ing region to prevent leakage cf oil to the atmosphere or to the molten
salt. The pump is driven with an electric motor mounted in the ambient
atmosphere. The pump tank and loop are preheated to 1200°F before they
are filled with molten salt. Preheating is provided by electrical
resistance heaters attached to the pump tank and piping.

A summary of the operating experience with this pump is presented
in Table 5. It became evident during the early development tests that
the lubricant flow path to the bearing was inadequate, and that the
rigid bearing support used at that time was probably being distorted
sufficiently to cause or to aid in the shaft seizures that halted the
first three tests. The lubricant flow path intoc the bearing was improved
by removing a flow restriction between the pool of molten salt in the

pump tank and the annular entrance to the bearing. The bearing was
ORNL-LR-DWG 417658

 

 

 

 

 

 

 

 

 

 

 

 

 

 

fih 1f’,,,MOTOR
‘?‘:
l*” i
i . ooy
Coy
fl T = M
/ !l =Y
el / COUPLING
/ | X |
A P bl
\ !
'/, .
Y L
W %
|
OIL LUBRICATE g
DOUBLE ROW ;
BALL BEARING ACE TYPE SEAL
HELIUM PURGE IN SEAL LEAKAGE OUT
—COOLING BARRIER
~2ft 3in.
' SALT LUBRICATED
HYDRODYNAMIC HELIUM
ING
SALT LEVEL
\ T —' - ~ )
VOLUTE g
IMPELLER

 

Fig. 9. Molten~Salt Pump With One Molten-Salt Lubricated
Bearing (ORNL).
Table 5,

Operating Characteristics Molten Salt Pump With One
Molten Salt Lubricated Bearing, Operated at ORNL

 

 

Pump
Salt Salt Test
Test. Temp. Shaft Flow No. of Duration Reason for Termination
No. ( oF) Speed ( Il'l) Start-Stops (hl")
(rpm) &P
1 1200 1200-1400  50-100 1 1/3 Salt bearing seizure
2 1200 1150 50 0 Selt bearing seizure
3 1200 1200 50 1 11 Salt bearing seizure Development
Tests
L 1200 1400 100 2 1000 Scheduled
5 1200 1200 50 100 105 Scheduled
6 1100-1350 800-1400 L5960 100 12,500  Salt bearing showed
signs of rubbing
T 1200 1200 50 1 58 Fulcrum pin worked
loose in bearing >£mdurance
gimbals mount Tests
8 1200 1200 1 1 Fulcrum pin worked
loose in bearing )

- Total Operation

13,616

gimbals mount

 

 

£e
2L

mounted in a gimbals arrangement to decouple it from thermal distortions
that might be experienced during high-temperature operation.

Three tests were made with this bearing configuration, in which the
pump was operated approximately 13,600 hr and was subjected to 200 start-
stop operations. The longest run of 12,500 hr and 100 start-stop cycles
was terminated when the bearing showed signs of slight rubbing. During
the short period between each pump stop and the subsequent restart, the
pump shaft was rotated by hand to check for tactile signs of rubbing be-
tween the bearing sleeve and journal.

Two additional attempts to operate the pump with new bearings were
halted by bearing seizure. We believe the seizures resulted from the
loosening of fulcrum pins in the gimbals mount. A revision to the gim-
bals design to prevent the loosening of these pins will be tested in the

near future.

Large Reactor Sodium Pump Proposed for Development by USAEC

Westinghouse and Byron-Jackson are developing conceptual designs
for a sodium pump of approximately 60,000 gpm capacity for the fast
breeder reactor program under USAEC contractual arrangements. An early
conceptual design (Fig. 10) shows the electric drive motor coupled to
the vertical pump shaft. The shaft extends downward from the floor
level through five feet of shielding into the pump tank. The lcwer end
of the shaft is supported in a sodium-lubricated bearing located sbove
the pump impeller. The upper end of the shaft is supported in an oil-
lubricated bearing located above the floor level. The sodium pocl is
blanketed with an inert gas at pressures ranging from 5 to 50 psig. A
shaft seal located close to the upper bearing prevents the leakage of
the blanket gas to the atmosphere.

The pump rotary element, including the double suction impeller, can
be withdrawn vertically from the pump tank by personnel working at floor
level. The overall length of the rotary element is 45-ft, and its diameter
is approximately five feet. Baffles are applied to minimize the formation
of vortexes in the sodium pool by the rotating shaft and to reduce both

the convective heat transfer and the diffusion cf sodium vapor in the

blanket gas region.
N
n

ORNL-DWG. 67-2694

  
    
   

~m THRUST BEARING
-~ SHAFT SEAL

NORMAL SODIUM LEVEL
PUMP TANK

LOWER RADIAL BEARING
+STATIC SEAL

. THERMAL BARRIER

. VOLUTE

CONCEPTUAL DRAWING
OF A 6000 HP FREE SURFACE
SHAFT SEALED SOBIUM PUMP

Fig. 10. Large Sodium Pump Concept Proposed for Development by
USAEC (From Ref. 19).
26

Short-Shaft PUmps

The distinguishing features of the short-shaft pump are the short
distance between the shaft support bearings and the overhung impeller.
This pump was used in the SEE and has been applied extensively by the
Reactor Division of CORNL; however, the capacities of the various models
are smaller than the requirements for proposed molten-salt breeder
reactors. At ORNL, the pumps have been used in the Aircraft Reactor
Experiment®?* and in the MSRE.2:'%® They have slso been used extensively
in metallurgicsl development programs and in heat transfer and heat ex-
changer development tests.

The SRE sodium pumps used a packing type seal (sodium freeze seal)
that separated the sodium from the atmosphere; whereas, the ORUL pumps
have the impeller and volute submerged in a vessel that serves as an
expansion tank in which there is g liquid-free surface. Oli-~lubricated
shaft seals are used to maintsin an inert atmosphere on the liquid-free

surface and to contain the oil.

Sodium Pumps for the SRE

 

The SRE is a 20 Mw(t) sodium-cooled nuclear power reactor with
heat transfer and service systems and a steam plant. The heat transfer
system consists of a primary scdium loop that cools the reactor and
delivers heat to a secondary sodium loop. The secondary loop heats the
steam operating system. The primary sodium flow passes through the reac-
tor and therefore becomes radioactive, while the secondary system is non-
radioactive. An auxiliary heat transfer system, comprised of primary and
secondary sodium loops, is provided to remove "after glow' heat during
reactor shutdown or during a failure of the main system.

Each of the four heat transfer loops contained a sodium pump, which
was & modified hot process pump similar to those used in refineries. The
principal modifications consisted of vertical mounting and the addition
cf scdium-freeze sesls on the shaft and the casing. The primary pumps
differed from the secondary pumps in that they had theilr shaft and casing

extended to remove the drive unit to a safe operating zone. The shaft
27

freeze seal replaced the conventional type packing. In this seal, which
earlier used tetralin as a coolant and later used NaK, sodium freezes
around the shaft to provide a seal. The earlier pumps used oil-lubricated
bearings to support the shaft. In later models the lower bearings were
replaced by grease-lubricated bearings to minimize the possibility of
hydrocarbon leakage into the sodium system. The main system pumps are
shown in Fig. 11l. The auxiliary pumps are similar, but their capacity

is reduced by the use of reduced diameter impellers.

The pumps served to circulate coolant sodium in the SRE for a
cumilative period of 37,000 hr at coolant temperatures of 285—1030°F
and at flows of 600-1600 gpm. The main problems encountered with the
pumps were associated with the freeze seals, which were responsible for
shaft binding, sodium extrusion, and gas inleaksge. In view of these
problems, different pump concepts were used 1n the sodium pumps for the

HNPF (discussed in a previous section).

General. Description of ORNL Pumps

The vertical pump shaft (Fig. 12) is supported at two places with
oll-lubricated bearings separated by about 11 3/8nin. and mounted in a
bearing housing. The impeller, which is mounted on the pump shaft about
26 l/h-in. below the lower shaft bearing (i.e., Qverhung), and the pump
casing, or volute, are immersed in a pcol of the working fluid in the
pump tank. The drive motor is mounted directly above and in line with
the bearing housing and is connected to the pump shaft through a flexible
coupling.

Shaft seals are used to minimize the leakage of the oil to the
gtmosphere and to the pumped fluid and also to prevent the leakage of
inert gas from the pump tank. A blanket of inert gas covers the free
surface of the working fluid in the pump tank to protect the fluid from
air and moisture contamination. Purge gas is used to scavenge seal oil
leakage and to remove fission products in reactor pump applications.
Running clearances between the rotating shaft and impeller and their
respective matching stationary surfaces accommodate radial shaft deflec-

tion and axial differential thermsl expansion. Preheat is provided in
 

 

ORNL-DWG. 67-7790

 

 

 

 

 

.

 

 

 

 

 

- TTT——
gy e i e e o T M

HOUSING ——

BEARING
X" PUMP CASE—]

1-:-' .«
. e P~

 

 

 

 

 

ry Pumps, Sodium Reactor

 

MAIN SECONDARY SODIUM PUMP

 

MAIN PRIMARY
SODIUM PUMP

      

Main Primary and Seconda

Fig. 11.
Experiment (From Ref. 7).
 

 

 

 

Ll

 

 

 

 

 

 

 

 

 

 

 

 

 

 

/7

222222

 

 

 

 

{Out of Section) SPACE
(See Insat) ~ ENON STRIPPER
BUBBLE TYPE {Sproy Ring)
LEVEL (NDICATOR SPRAY

ORNL-LR-DWG~56043-BR2

   
  
  
 
 
 
  
   
 
  
   
  
 
 
  
  
   
  
   
 
 
   
   
  
  
 

SHAFT ATER
COUPLING COOLED
MOTOR
SHAFT SEAL
(See inset) M= W =TT

LEAK
DETECTOR

LUBE OIL iN

BE OIL BREATHER

BALL BEARINGS
(Face to Face)

  

BEARING HOUSING

GAS PURGE IN A/
SHAFT SEAL (See Inset)
SHIELD COOLANT PASSAGES
{in Paraliet With Lube Oil)

SHIELD PLUG

BALL BEARINGS
{Back to Back)

LUBE OiL ouT

SEAL OIL LEAKAGE

DRAIN
LEAK DETECTOR GAS PURGE OUT (See Inset)—

SAMPLER ENRICHER GAS FILLED EXPANSION

OPERATING
LEVEL

 

To Overflow Tank

Fig. 12. MSRE Fuel Salt Pump (ORNL).
30

most cases with electrical resistance heaters which are attached to the
pump tanks and piping. Also, where possible, the pumps are rotated to
circulate helium and to bring the system container material to near
isothermal conditions.

The design parameters for these pumps used in the Reactor Division
at ORNL are presented in Table 6. The capacities range from 5 gpm for
the early LFB pumps to 1200 to 1600 gpm for the later MSRE and PKP pumps,
and the pump heads range up to 400 ft. The range of operating temperatures
and the total operating time for each pump model are also presented.
Table 7 provides a list of those pumps that were operated for pericds in

excess of one year.

MSRE Fuel and Coolant Salt Pumps

 

Both of these pumps, which are operating in the MSRE, are short
shaft sump pumps; and in external appearance they are nearly identical.
The hydraulic designs of the volutes and impellers and the pump operating
speeds differ, as set forth in Table 6.

The inert gas in the fuel salt pump performs functions additional
to that of protecting the salt from contamination. A flow of inert gas
introduced at an intermediate point in the pump shaft annulus (Fig. 12)
is used (1) to scavenge oil that leaks past the lower shaft seal into
the catch basin (oil is carried from the pump to an external tank);

(2) to prevent the diffusion of radioactivity from the pump tank gas
space to the region of the lower shaft seal; (3) to strip Xenon-135,
principal poison of the thermal neutron chain reaction, from a spray cof
salt in the pump tank; and (4) to dilute and transport the poison t¢ an
external charcoal trap system.

The MSRE pumps have been operated a total of more than 21,000 hr
in the reactor and were previously subjected to approximately 5000 hr
operaticon during various hot shakedown tests in a prototype pump test
facility. Also, a prototype pump was operated nearly 9,000 hr during
various development tests.

The principal difficulties that were resolved during development

of the MSRE pumps included shaft seizures and excessive o0il leakage
Table 6. Characteristics of Short Shaft Sump Pumps at ORNL

 

 

Model Process Head? Flowa Speeda Temp. No. Total
Fluid (£t) (gpm) (rpm) (°F) Built Hours
L.FB - Na, NeK, and 92 5 6000 1100-1400 L6 451,000%
Molten Salt
DANA Na, NaK, and 300 150 3750 1000~1500 10 57,000
Molten Salt
‘DAC Molten Salt 50 60 1450 1000-1400 3 4,000
In-Pile Loop Molten Salt 10 1 3000 8 14,000
MF NaK and 50 700 3000 1100-1500 hl,OOOd
' Molten Salt
MN Na. and NakK 120 500 3600 1050—-1250 1 7,000
PKA NaK and 400 375 3550 TO0--L500 19,000
Molten Salt
PKP NaX and 380 1500 3500 700-1500 L 40,000
Molten Salt
MSRE Prototype Fuel Molten Salt 50 1200 1150 1100-1500 1 8,900
MSRE - Fuele Molten Salt 50 1200 1150 1100-1300 2 3,300
MSRE - Coolant® Molten Salt 100 850 1750 11001300 2 1,600
MSRE Reactor Operation Molten Salt 50 1200 1175 1200 9,700
(Fuel Pump)f
MSRE Reactor Operation Molten Salt 78 800 1775 1000 11,400
(Coolant Pump)¥ e
Total 668,000

 

®at design points.

bSome pumps were operated for periods of 15,000-20,000 hr.

®Includes 3000 hr in-pile operation.

dTncludes continuous operation of 25,500 hr for a.single pump, circulating molten salt.
€Operation in Molten Salt Pump Test Facility, hot shakedown of 2 ea rotary elements.

fOperation of single rotary element.

1€
32

Table 7. Endurance Operation of
Short Shaft Sump Pumps at ORNL

 

 

Model Nurg?er Working Dul"f;}imfl
Units Fluid Test
(hr)
LFB 3 Molten Salt 8,800
LFB 1 Molten Salt 20,000
LFB 1 Molten Salt 15,000
MF 1 Molten Salt 25,500
PK 1 NaK 16,600
PK 1 Molten Salt 9,700
MSRE Fuel 1 Molten Salt 9,700
MSRE Coolant 1 Molten Salt 11,400

 

past the lower shaft seal. Operation of the pump at off-design capacity
conditions caused a pump shaft seizure, when the shaft deflection ex-
ceeded the value of the running clearance. The running clearances were
increased sufficiently to accommodate the off-design operating conditions.
Seal performance was improved by reducing the tolerances on the concen-
tricity and parallelism of the stator face of the shaft seal with respect
to the rotor face. The final machining operation on the seal stator is
performed in a lathe, using a fixture designed to attain the required
concentricity and parallelism.

Several incidents of plugging in the off-gas line from the fuel
salt pump tank have occurred during operation of the MSRE. We believe
there is a small leakage of 0il into the fuel salt pump tank, and that
the thermally cracked products are subsequently polymerized by radio-
activity in the off-gas line, particularly in small flow-area configu-
rations (e.g., needle valves, capillary tubes, and gas filters). The
spare rotary elements for the MSRE pumps have been modified to replace
a gasketed joint with & seal weld to remove what is thought to be the

major source of oil leakage into the pump tank.
33

Experience indicates that after pump development has been accom-
plished, the main sources of difficulty arise from failures in electrical
and speed control systems and from such drive motor components as the

electrical insulation system and the rotor support bearings.

PROBLEMS ANTICIPATED WITH LARGE PUMPS FOR
MOLTEN-SALT BREEDER REACTORS

Other than the shaft length, the primary configuration difference
between the short- and long-shaft pumps is the means of supporting the
shaft. The short shaft is usually supported with oil-lubricated ball
bearings at two places located relatively close together. A short
separation distance is provided between the elevated temperature work-
ing fluid and the thermal and radiation sensitive pump components in
the bearing housing and drive motor. The long shaft 1s supported at
its lower end with a pumped fluid-lubricated bearing and at its upper
end with a conventionally lubricated bearing. These two bearings are
widely separated. A long separation is provided between the pumped
fiuid and the sensitive pump components. The two configurations differ
strongly in other areas: the dynamic response of the individual rotating
components assembly, the kind of shaft support bearings used, and the
thermal and radiation damage protection requirements.

The molten-salt pump requirements presently envisioned for the MSBR
and the MSBE are listed in Table 8. A comparison between the two pumps
is made on the bases of their differences and the problems anticipated
with their application to the pumping requirements for the molten-salt
thermal breeder reactors. The principal technology problems include
(1) dynamic response of the rotating components assembly, (2) bearings,
(3) thermal and radiation damage protection, (4) shaft seals, (5) hydrau-

lic design, and (6) fabrication and assembly.
Dynamic Response of the Rotating Components Assembly

The dynamic response of the rotating components assembly (which is

comprised of the shaft, drive motor, impeller, and bearings) and the
34

Table 8. Pumps for Molten-Salt Breeder Reactors

 

 

Fuel Blanket Cooclant
2225 Mwt MSER
Number required L L L
Design temperature, °F 1300 1300 1300
Capacity, gpm 11000 2000 16000
Head , ft 150 80 150
Speed, rpm 1160 1160 1160
Specific speed, Ns 2830 2150 3400
NPSH, required, ft 25 8 32
(Net Positive Suction Head)
Impeller input power, hp 990 250 14k0
Distance between bearings, ftb 29 29 1.5
Impeller overhang, ftb 2.5 2.5 5
150 Mwt MSBE
Number required 1 1 L
Design temperature, °F 1300 1300 1300
Capacity, gpm 4500 54O 4300
Heag, ft 150 80 150
Speed, rpm 1750 1750 1750
Specific speed, N_ 2730 1520 2670
NPSH required, ft 27 5 26
(Net Positive Suction Head)
Impeller input power, hp 410 61 390
Distance between bearings, ftb 20 20 1.5
Impeller overhang, ffb 2 2 5

 

aOne pump is required for each of the four modules in
the MSER.

b
Estimated from preliminary pump layouts.
35

pump casings must provide vibraticn amplitudes that are sufficiently low
to be tolerable to the shaft support bearings and seals, and pump struc-
ture throughout the entire range of operating speeds. In this respect
the long shaft presents the more critical problem.

A preliminary layout of the MSBR fuel salt pump indicates a shaft
length of approximately 35-ft for use with the oven heousing concept. It
may be necessary to operate this pump supercritically, i.e., at design
speed above the first shaft critical frequency, in contradistinction to
the usual practice of setting the design speed at approximately three-
guarters of the first shaft critical. Mathematical analyses can now be
made of the dynamic response of supercritical shafts. The usual closed
solutions and graphical approximation methods for calculating shaft re-
sponse have been augmented during the past few years with sophisticated
computer programs. These programs have been expanded to permit computa-
tion of the dynamic response of supercritical shafts.

The newness of operating long supercritical shafts and calculating
their dynamic response invites, if not requires, proof-testing. Although
it would be most satisfactory to simulate the full-scale supercritical
shaft system, study may indicate the feasibility of proof-testing with
reduced-scale models. Because of these problems, additional studies will
be made of the reactor cell layout. It may be possible to reduce shaft
length sufficiently to permit sub-critical operation of the MSBR fuel

and blanket salt pumps.
Rearings

The short-shaft pump does not require development of bearings, and
its reliability is enhanced by the use of conventionally lubricated ball
bearings that have good long-term life based on large statistical sam-
plings.

The long-shaft pump configuration requires a molten-salt lubricated
journal bearing near the lower end of the shaft. The bearing guides the
pump impeller in its casing so that there is no rubbing between these
two components. The problems include the design of the bearing to pro-
duce the hydrodynamic lubricating film with molten salt, the selection

of the bearing materials and their form (hard surface coating or integral

body construction), the accommodation of differential thermal expansion
36

if integral body construction is used, and the design of a bearing mount-
ing arrangement that will accommodate some thermal distortion between
the pump shaft and casing without interferring with the lubricating film
in the bearing.

The hydrodynamic design of process fluid lubricated bearings is on
a firm foundation and no real problem is anticlpated with this aspect
of the design of molten-salt bearings. However, there are some un-
regsolved questions about the bearing materials and the mechanical design
of their attachment to the pump statlionary element.

Although approximately 30 Hastelloy-N vs Hastelloy-N bearings,?°
which represent a relatively soft-on-soft combination, were successfully
operated in molten salt, it is believed that a hard-on-hard combination
is a better choice for molten-salt systems. The cemented carbides,
which utilize cobalt, nickel or molybdenum binder, appear to be good
candidate materials. They may be used in solid body form or applied
to the softer container material with plasma spray techniques to form a
hard surface coating. A program to determine the compatibility and to
assess the appropriate characteristics of the selected bearing materials
in molten salt is required.

Thermal distortion of the pump casing can have a deleterious effect
on the alignment between journal and bearing, which is so necessary to
the satisfactory operation of the molten-salt bearing. It appears that
a uniform temperature distribution in the casing and a bearing mounting
arrangement that will accommodate some distortion between shaft and
casing must be provided. A program is reguired to proof-test the full-
scale bearing and mounting arrangement in molten salt and to simulate
the anticipated start-stop requirements, thermal cycling, and endurance

conditions.
Thermal and Radiation Damage Protection

The reliability of a salt pump for the fuel and blanket salt systems
for a molten-salt breeder reactor is strongly dependent upon the tempera-
ture and the radiation dose to which the conventional lubricant and drive

motor components are subjected. The long-shaft pump provides a much
37

greater separation between the sensitive components and the sources of
thermal and radiation damage than the short shaft configuration. Very
low radiation dosage and gentle temperature gradients are expected for

the long-shaft pump.
shaft Seals

A shaft seal is required with either the long- or short-shaft pump
to maintain separation between the lubricant in the upper shaft bearing
and the molten salt in the pump tank. Its design should be as simple as
possible, consistent with convenient replacement of the seal. The an-
ticipated problems include (1) the fabrication of a bellows to accommodate
the required pump shaft diameter, (2) the attachment of the rotor wear
surface with respect to the axis of shaft rotation, (3) the attachment
of the stator wear element to the bellows to obtain a hermetic joint,
(4) the assembly of the stator element to provide both squareness and
concentricity of its wear surface with the axis of shaft rotation to
close tolerances. Although shaft seals preoportioned for 3-in.-diam
shafts have been operated continuously for more than 25,000 hr, a pro-
gram to produce and to proof-test seals for larger diameter pump shafts

is required.
Hydraulic Design

The salt pump capacities for the MSBE and the MSBR range from 500
to 16,000 gpm. The hydraulic designs of impellers and diffusers or
volute casings in this capacity range are available in the pump industry.
Allis-Chalmers Manufacturing Company provided the hydraulic designs and
assisted a reputable founder to produce the Hastelloy-N impeller and

volute castings for the MSRE fuel and coolant salt pumps.

Fabrication and Assembly

 

Both the long- and short-shaft pumps will require the fabrication
of large pump impellers and diffusers or volute casings from castings
38

or weldments. A survey of U. S. industry is being made to determine the
influence of the best state-of-the-art fabrication methods and quality
controls on the design of long and large diameter shafts and casings.
The results of the survey will be used in making pump conceptual layouts
and will be made available to pump manufacturers. By comparison, the
long=-shaft pump components will require large and long handling equip-

ment and increased headroom in the assembly and installation areas.

CONCLUSIONS

A history of satisfactory operation makes the short shaft pump very
attractive for application to molten-sglt breeder reactors. However, the
proposed oven concept, mentioned previously for preheating and containing
the fuel and blanket salt systems, would impose stringent cooling and
radigtion protection requirements for the pump. The pump would need to
be contained in a re-entrant cell supported from the ceiling. The cell
would restrict accessibility to the drive motor and rotary element and
would increase the pump installation problems. The reliability of the
pump would depend directly on the religbility of the cooling systen.

However, the application of the short-shaft pump to the fuel and
blanket salt systems would be attractive if the salt system components
were preheated individually, the pump were provided with adequate local
nuclear radiation shielding, and an ambient temperature below 200°F were
maintained in the reactor cell.

Probably the most desirable pump configuration from the viewpoint
of the reactor designers and operators is the canned rotor pump. This
pump has no limitations on either orientation or elevation. However,
its application to molten-salt reactors would require the development
or invention of a radiation-resistant, high-temperature electric motor.
It also would impose the necessity for long term maintenance of satis-
factory alignment between the matching surfaces of process-lubricated
Jjournal and thrust bearings. These problems appear to be difficult and

expensive to resolve.
39

We believe that the long-shaft pump is the best configuration for
the fuel and blanket salt oven cell concept being considered for molten-
salt breeder reactors because it provides the greatest thermal and nuclear
radiation protection to the drive motor. The location of the coolant salt
pump near the ceiling of its oven and the anticipated low level of radio-
activity mske feasible the application of the short-shaft pump to the

coolant salt system.

ACKNOWLEDGMENT

We acknowledge gratefully the work and cooperation of the individuals
and companies whc contributed to the survey and the contributions ©f
Orville Seim of Argonne National ILaboratory, Norman Peters of Atomic Power

Development Associates, and Robert Atz of Atomics International.
10.

11,

12,

13,

Lo

REFERENCES

P. R. Kasten, E. S. Bettis, and R. C. Robertson, Design Studies
of 1000-Mw(e) Molten-Salt Breeder Reactors, ORNL-3996, Oak Ridge
National Laboratory, August 1966.

H. G. MacPherscn, Molten-Salt Reactor Will Produce Low Cost Power,
Power Engineering, Part 1,71(1): 28-31 (January 1967);
Part 2, 71(2): 56-58 (February 1967).

 

R. C. Robertson, MSRE Design and Operations Report, Part 1 -
Description of Reactor Design, ORNL-TM-728, Oak Ridge National
Laboratory, January 1965.

J. J. Morabito and H. W. Savage, Major Components and Test Facili-
ties for Sodium Systems, Detroit Meeting April 2628, 1965, ANS-100,
pp. 308-311.

H. O. Monson et al., Components for Sodium Reactors, 1964 Geneva
Conference, P/228 USA, pp. 594-5937.

Design Modifications to the SRE During FY 1960, NAA-SR-5348 (Rev.)
February 15, 1961, p. 108.

E. N. Pearson, SRE System and Components Experience - Core II,
Presented at the Sodium Components Development Program Information
Meeting, Palo Alto, California, August 20-21, 1963, Atomics Inter-
national.

The Effects of Long-Term Operation on SRE Sodium System Components,
NAA-SR-11396, 50 p., August 31, 1965.

K. G. Eickhoff, J. Allen, and C. Boorman, Engineering Development
for Sodium Systems, BNES, London Conference on Fast Breeder Reactors,
May 17-19, pp. 6-9, 1966.

J. Baumier, Mechanical Pumps for 1 and 10 Mw Test Loops, DRP/ML/FAR
R/100, February 20, 1962.

J. Baunier and H. J. Gellion, Mechanical Pumps for Liquid Metals,
Colloquium of the European Soclety of Atomic Energy on Liquid Metals,
Aix-en-Provence, September 30 to October 2, 1963.

L. A. Whinery, 2000-Kw Sodium Test Facility Project Description and
Progress Report, LAMS-25L1, June 3C, 1958 through September 30,
1959.

Quarterly Status Progress Report on Lampre Program for Pericd Ending
August 20, 1961, LAMS-2620, pp. 23-2L, September 29, 1961.
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16.

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Quarterly Status Progress Report on Lampre Program for Period
Ending November 20, 1961, LAMS-2647, pp. 12-13, December 27,
1961.

P. G. Smith and L. V., Wilson, Development of an Elevated-Temperature
Centrifugal Pump for s Molten-Salt Nuclear Reactor, ASME Paper 65
WA/FE-27 11 p., December 1965.

Oak Ridge Nastional Laborstory, MSRP Semlann. Progr. Rept. July 31,
1964, USAEC Report ORNL-3708, pp. 147-167.

H. W. Savage and A. G. Grindell, Pumps for High-Temperature Liquid
Systems, Space Nuclear Conference, Gatlinburg, Tennessee, American
Rocket Society, 16 p., May 3-5.

A. G. Grindell, W. F. Boudreau, and H. W. Savage, Development of
Centrifugal Pumps for Operation with Liquid Metals and Molten
Salts at 1100—1500°F, Nuclear Science and Engineering, 7(1):
83-91 (January 1960).

Sodium Pump Development and Pump Test Facility Design, WCAP-2347,
August 1963.

P. G. Smith, High-Temperature Molten-Salt Lubricated Hydrodynamic
Journal Bearings, ASLE Trans., 4(2): 263-274 (November 1961).

R. W. Atz, Operating Experience with Heat Transfer System Pumps
at the Hallam Nuclear Power Facility, NAA-SR-Q717, June 15, 196L.

R. W. Atz, Performance of HNPF Prototype Free-Surface Sodium Pump,
NAA-SR-4336, 26 p., June 1960.

0. 8. Seim and R. A. Jaross, Characteristics and Performance of
5000 gpm A.C. Linear Induction and Mechanical Centrifugal Sodium
Pumps, A/CONF 15/P/2158, USA, June 1958.

H. W. Savage, G. D. Whitman, W. G. Cobb, and W. B. McDonald,
Components cf the Fused-Salt and Sodium Circuits of the Air-

craft Reactor Experiment, ORNL-2348, Oak Ridge National Laboratory,
September 1958.
O 01 OV =w o

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Adams

. Adamson
Affel
Alexander
Apple
Baes

. Baker
Ball
Bauman

. Beall
Bender

S. Bettis

F. Blankenship
B. Blanco

0. Blomeke
Blumberg

G. Bohlmann
J. Borkowski
E. Boyd
Braunstein

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Bronstein
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Canonico
antor
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Compere
Cook

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Crowley

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Epler
Ferguson
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Fraas
Friedman
Frye, dJr.
. Gabbard

. Gallaher
. Goeller

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INTERNAL DISTRIBUTION (continued)

97T. A. M. Perry 132. R. C. Steffy
98. H. B. Piper 133. H. H. Stone
99. B. E. Prince 134. J. R. Tallackson
100. J. L. Redford 135, E. H. Taylor
101. M. Richardson 136. R. E. Thoma
162. R. C. Robertson 137. J. S. Watson
103. H. C. Reller 138. C. F. Weaver
104-105. M. W. Rosenthal 139. B. H. Webster
106. H. C. Savage 140. A. M. Weinberg
107. C. E. Schilling 141. J. R. Weir
108. Dunlap Scott 42, W. J. Werner
109. H. E. Seagren 143. K. W. West
110. W. F. Schaffer 144, M. E. Whatley
111. J. H. Shaffer 5. J. C. white
112. M. J. Skinner 6. L. V. Wilson
113. G. M. Slaughter 147. G. Young
114, A. N. Smith 148. H. C. Young
115. F. J. Smith 149. ORNL Patent Office
116. G. P. Smith 150-151, Central Research Library (CRL)
117. ©O. L. Smith 152-153. Document Reference Section (DRS)
118-129. P. G. Smith 154-206. Laboratory Records (LRD)
130. W. F. Spencer 207. Laboratory Records - Record Copy
131. I. Spiewak (LRD-RC)

EXTERNAL DISTRIBUTION

208, R. W. Atz, Atomics International, Canoga Park, Cslifornia
209. Byron-Jackson Pumps, Inc., Los Angeles
210. B.Cametti, Westinghouse, Cheswick,; Pennsylvania
211. E. J. Cattabiani, Westinghouse, Cheswick, Pennsylvania
212-213. D. ¥, Cope, AEC-ORNL R.D.T. Site Office
21k, J. W. Crawford, AEC-RDT, Washington .
215. P. W. Curwen, Mechanical Technology Incorporated, Latham, N. Y.
216, C. B. Deering, AEC-ORO
217. E. G. Eickhoff, UKAEA
218, A. Giambusso, AEC-Washington
219. W. J. Larkin, AEC-ORO
220. Liquid Metal Information Center, Atomics International
221. C. L. Matthews, AEC-ORO
222=-223, T. W, McIntosh, Atomic Energy Commission, Washington
224. C. E, Miller, Jr., Atomic Energy Commission, Washington
225. N. T. Peters, Atomic Power Development Associates
226, B. T. Resnich, Atomic Energy Commission, Washington
227. H. M. Roth, AEC-ORO
228. 0. S. Seim, Argonne National Laboratory
229. Milton Shaw, Atomic Energy Commission, Washington
230. W. L. Smalley, AEC-ORQ
231. Beno Sternlicht, Mechanical Technology, Incorporated, Lathem, N. Y.
232. R. F. Sweek, AEC-Washington
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