United States Nuclear Regulatory Commission - Protecting People and the Environment

Information Notice No. 89-08: Pump Damage Caused by Low-Flow Operation

                                  UNITED STATES
                          NUCLEAR REGULATORY COMMISSION
                             WASHINGTON, D.C.  20555

                                January 26, 1989



All holders of operating licenses or construction permits for nuclear power 


This information notice is being provided to alert addressees to potential 
problems that may result from operation of centrifugal pumps at flows that 
can cause severe pump component damage.  It is expected that recipients will 
review the information for applicability to their facilities and consider 
actions, as appropriate, to avoid similar problems.  However, suggestions 
contained in this information notice do not constitute NRC requirements; 
therefore, no specific action or written response is required.

Description of Circumstances:

Two events which resulted in pump damage are described below.  Operations for 
extended periods at low-flow conditions apparently created hydraulic 
instability, resulting in pump damage from cavitation, pressure pulsation, 
and/or vibration.  These events occurred at the Haddam Neck Plant and 
Susquehanna Steam Electric Station, Unit 1 (Susquehanna 1).  The pump damage 
at the Haddam Neck plant was attributed to pressure pulsation and pump 
vibration, while at Susquehanna 1 it was the result of cavitation.

Haddam Neck Plant Event:

On February 4, 1988, an electric-driven fire pump was declared inoperable 
during a routine surveillance test when a high-amperage condition was noted.  
The normal indication of 200 amps initially increased to between 340 and 360 
amps.  The indication further increased to 1000 amps during a subsequent 
manual restart.  The cause of the high amperage was attributed to physical 
damage to the stuffing box brass bushing in the upper shaft area.  On the 
basis of the licensee's evaluation and its discussions with the manufacturer, 
the licensee concluded that prolonged operation of the pump at low flow may 
have caused the problem.  Operation of the pump at or near the shut-off head 
had occurred during the containment integrated leak rate test.  During the 
test, the fire pump operated in a low-flow mode, providing cooling water to 
the air compressors.

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                                                            January 26, 1989
                                                            Page 2 of 3

Susquehanna 1 Event:

While the plant was operating at full power on May 22, 1986, an over-current 
alarm for an emergency service water (ESW) pump was received in the control 
room.  The pump was declared inoperable, placing the plant in a limiting 
condition for operation.  Subsequent disassembly of the pump revealed that 
the bottom portion of the pump suction bell had separated from the pump body 
and fallen into the pump pit.  In addition, the pump's impeller vanes were 
eroded through.  Similar, but less severe, damage was found on the three 
other ESW pumps.  A subsequent inspection of the residual heat removal 
service water (RHRSW) pumps found similar damage.  The licensee determined 
that the damage to the ESW and RHRSW pumps was caused by recirculation 
cavitation, caused by operation of the pumps at flows significantly below 
their design flow rates.

The ESW pumps are normally operated at 60 percent or less of their design flow 
of approximately 6,000 gallons per minute (gpm) per pump.  When the loop sup-
plying cooling water to the diesels is run with two operating pumps, each pump 
delivers approximately 3500 to 3900 gpm.  The other loop, that does not serve 
the diesels is normally run with only one pump providing approximately 1000 
to 1500 gpm.  Operation at these conditions is believed by the pump vendor 
to cause recirculation cavitation.  In addition, the RHRSW pumps are believed 
to have been operated at less than 50 percent of design flow most of the time.  
The licensee indicated that the cavitation damage can be avoided by operating 
the pumps at higher flows; specifically, operation at 75 to 100 percent of 
design flow is desirable.


These events illustrate that pump damage, caused by operating pumps at flows 
significantly below their design flow rates, has resulted, with slow deteri-
oration of pump internals occurring over a long period.  During the early 
phases of degradation, the pumps were still functional and remained operable.  
The pumps had to be disassembled before damage to the pump internals could be 
seen.  Therefore, the routine pump surveillance tests, provided in the plant 
inservice test programs, may not be capable of detecting early component de-
gradation.  In addition, while operating the pumps in their normal, specified 
system operating ranges, plant personnel were not aware of a problem until 
actual failure of a pump occurred.  It is most likely that pump degradation 
caused by low-flow operation will go undetected until total failure of the 
pump occurs, preventing the associated system from performing its safety 

.                                                            IN 89-08
                                                            January 26, 1989
                                                            Page 3 of 3

No specific action or written response is required by this information notice.  
If you have any questions about this matter, please contact the technical 
contact listed below or the Regional Administrator of the appropriate regional 

                                   Charles E. Rossi, Director
                                   Division of Operational Events Assessment
                                   Office of Nuclear Reactor Regulation

Technical Contact:  Chuck Hsu, AEOD
                    (301) 492-4443

Attachment:  List of Recently Issued NRC Information Notices
..                                                            Attachment 
                                                            IN 89-08
                                                            January 26, 1989
                                                            Page 1 of 1

                             LIST OF RECENTLY ISSUED
                             NRC INFORMATION NOTICES
Information                                  Date of 
Notice No._____Subject_______________________Issuance_______Issued to________

89-07          Failures of Small-Diameter    1/25/89        All holders of OLs
               Tubing in Control Air, Fuel                  or CPs for nuclear
               Oil, and Lube Oil Systems                    power reactors.
               Which Render Emergency Diesel
               Generators Inoperable

89-06          Bent Anchor Bolts in          1/24/89        All holders of OLs
               Boiling Water Reactor                        or CPs for BWRs 
               Torus Supports                               with Mark I steel 
                                                            torus shells. 

89-05          Use of Deadly Force by        1/19/89        All holders of OLs
               Guards Protecting Nuclear                    for nuclear power
               Power Reactors Against                       reactors.
               Radiological Sabotage

89-04          Potential Problems from       1/17/89        All holders of OLs
               the Use of Space Heaters                     or CPs for nuclear
                                                            power reactors and
                                                            test and research

89-03          Potential Electrical          1/11/89        All fuel cycle and
               Equipment Problems                           major nuclear 

89-02          Criminal Prosecution of       1/9/89         All holders of a
               Licensee's Former President                  U.S. NRC specific
               for Intentional Safety                       license.

88-23,         Potential for Gas Binding     1/5/89         All holders of OLs
Supp. 1        of High-Pressure Safety                      or CPs for PWRs.
               Injection Pumps During a
               Loss-of-Coolant Accident

89-01          Valve Body Erosion            1/4/89         All holders of OLs
                                                            or CPs for nuclear
                                                            power reactors.

88-46,         Licensee Report of Defective  12/30/88       All holders of OLs
Supp. 2        Refurbished Circuit Breakers                 or CPs for nuclear
                                                            power reactors.
OL = Operating License
CP = Construction Permit 
Page Last Reviewed/Updated Friday, May 22, 2015