Protecting People and the EnvironmentUNITED STATES NUCLEAR REGULATORY COMMISSION
UNITED STATES
NUCLEAR REGULATORY COMMISSION
OFFICE OF NUCLEAR REACTOR REGULATION
WASHINGTON, D.C. 20555
January 26, 1989
Information Notice No. 89-08: PUMP DAMAGE CAUSED BY LOW-FLOW OPERATION
Addressees:
All holders of operating licenses or construction permits for nuclear power
reactors.
Purpose:
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.
8901190418
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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.
Discussion:
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
function.
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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
office.
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
reactors.
89-03 Potential Electrical 1/11/89 All fuel cycle and
Equipment Problems major nuclear
materials
licensees.
89-02 Criminal Prosecution of 1/9/89 All holders of a
Licensee's Former President U.S. NRC specific
for Intentional Safety license.
Violations
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
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