Information Notice No. 88-87: Pump Wear and Foreign Objects in Plant Piping Systems
UNITED STATES
NUCLEAR REGULATORY COMMISSION
OFFICE OF NUCLEAR REACTOR REGULATION
WASHINGTON, D.C. 20555
November 16, 1988
Information Notice No. 88-87: PUMP WEAR AND FOREIGN OBJECTS IN PLANT
PIPING SYSTEMS
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
flow reduction resulting from pump wear and foreign objects in plant piping
systems. It is expected that recipients will review the information for ap-
plicability 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:
The NRC has received three licensee event reports (LERs) (50-281/88-004,
50-281/88-010, and 50-280/88-017) related to pump wear and foreign objects in
plant piping systems that could affect the ability of plant safety systems to
perform their functions during a design-basis accident. These events were
reported by Virginia Electric and Power Company's Surry Nuclear Power Station.
On March 27, 1988, during a manual reactor trip on Surry Unit 2, the auxiliary
feedwater (AFW) flow to the "A" steam generator (S/G) was noted to be low.
Extensive valve testing and inspections at the time did not locate the cause
of the low flow (LER 50-281/88-004).
On May 16, 1988, Surry Unit 2, while at 100 percent power, experienced a
reactor trip as a result of S/G low-low level. Following the reactor trip,
the AFW flow to the "A" S/G was noted lower than expected. The flow was
observed to be 227 gallons per minute (gpm) compared with 325 gpm for the "B"
and "C" S/G. Additional testing of the AFW flow to the "A" S/G indicated that
a partial blockage existed in the flowpath.
The reduced AFW flow to the "A" S/G was due to a metallic object partially
blocking the cavitating venturi in the "A" AFW line. The metal piece was
determined to be from the channel ring vane on the "B" motor-driven AFW pump.
Subsequent visual inspection using fiber optics located two metal pieces. One
was located upstream of the cavitating venturi in the line to the "A" S/G and
a second was at a flow orifice in the "C" S/G AFW line. Inspection of the
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November 16, 1988
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three AFW pumps revealed that one chip was missing from a channel ring vane
tip in the "A" motor-driven AFW pump, eight small pieces were broken off from
the channel ring vane tips in the "B" motor-driven AFW pump, and numerous
chips were missing from the outer vane ends in the turbine-driven AFW pump.
In addition, a nondestructive inspection revealed several cracked channel ring
vanes in the turbine-driven AFW pump.
The two pieces retrieved from the piping were verified to have come from the
"B" motor-driven AFW pump. Extensive inspection of the AFW system piping did
not locate the other small pieces missing from the AFW pumps (LER
50-281/88-010).
On June 6, 1988, Surry Units 1 and 2 were in cold shutdown following a special
test run of the Unit 1 inside recirculation spray pump (IRSP), and foreign
material was found in the temporary discharge cone strainer. The material
consisted of cap screws, a swagelock cap, nuts, weld wire, and other objects.
As a result of this finding and the imminent return to power by Unit 2, the
Unit 2 recirculation spray pump sumps were inspected. This area includes the
pump suctions for the IRSPs, the outside recirculation spray pumps, and the
low-head safety-injection pumps. This inspection, utilizing fiber optics,
observed nuts, bolts, wire, metal and wood pieces, and other material in the
sump. These foreign objects were subsequently removed (LER 50-280/88-017).
Discussion:
The events described above illustrate the potential for loss or significant
reduction of flow from safety-related pumps as a consequence of pump wear and
foreign objects in the plant piping systems. The objects in the AFW system
significantly reduced the flow to the affected S/G. Lack of appropriate pump
internal inspections may have contributed to the failure to identify the
problem with the pump channel ring vanes earlier. The foreign objects found
in the safety-related system piping resulted from inadequate foreign material
exclusion from sump wells and/or inadequate inspection after maintenance
activities in the past.
No specific action or written response is required by this information notice.
If you have any questions about this matter, please contact one of the
technical contacts 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 Contacts: W. Holland, Region II
(804) 357-2101
L. Nicholson, Region II
(804) 357-2101
Attachment: List of Recently Issued NRC Information Notices
. Attachment
IN 88-87
November 16, 1988
Page 1 of 1
LIST OF RECENTLY ISSUED
NRC INFORMATION NOTICES
_____________________________________________________________________________
Information Date of
Notice No._____Subject_______________________Issuance_______Issued to________
86-106, Feedwater Line Break 11/10/88 All holders of OLs
Supp. 3 or CPs for nuclear
power reactors.
88-86 Operating with Multiple 10/21/88 All holders of OLs
Grounds in Direct Current or CPs for nuclear
Distribution Systems power reactors.
88-85 Broken Retaining Block 10/14/88 All holders of OLs
Studs on Anchor Darling or CPs for nuclear
Check Valves power reactors.
88-84 Defective Motor Shaft 10/20/88 All holders of OLs
Keys in Limitorque Motor or CPs for nuclear
Actuators power reactors.
88-83 Inadequate Testing of Relay 10/19/88 All holders of OLs
Contacts in Safety-Related or CPs for nuclear
Logic Systems power reactors.
88-82 Torus Shells with Corrosion 10/14/88 All holders of OLs
and Degraded Coatings in or CPs for BWRs.
BWR Containments
88-81 Failure of Amp Window 10/7/88 All holders of OLs
Indent Kynar Splices or CPs for nuclear
and Thomas and Betts power, test, and
Nylon Wire Caps During research reactors.
Environmental Quali-
fication Testing
88-80 Unexpected Piping Movement 10/7/88 All holders of OLs
Attributed to Thermal or CPs for PWRs.
Stratification
88-79 Misuse of Flashing Lights l0/7/88 All holders of OLs
for High Radiation Area or CPs for nuclear
Controls power reactors.
_____________________________________________________________________________
OL = Operating License
CP = Construction Permit
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