Information Notice 2004-07, Plugging of Safety Injection Pump Lubrication Oil Coolers with Lakeweed
| ML040770145 | |
| Person / Time | |
|---|---|
| Issue date: | 04/07/2004 |
| From: | Beckner W NRC/NRR/DIPM/IROB |
| To: | |
| Foster J, NRR/IROB, 415-3647 | |
| References | |
| IN-04-007 | |
| Download: ML040770145 (6) | |
UNITED STATES
NUCLEAR REGULATORY COMMISSION
OFFICE OF NUCLEAR REACTOR REGULATION
WASHINGTON, DC 20555-0001 April 7, 2004 NRC INFORMATION NOTICE 2004-07: PLUGGING OF SAFETY INJECTION PUMP
LUBRICATION OIL COOLERS WITH
LAKEWEED1
Addressees
All holders of operating licenses or construction permits for nuclear power reactors, except
those who have permanently ceased operations and have certified that fuel has been
permanently removed from the reactor vessel.
Purpose
The U.S. Nuclear Regulatory Commission (NRC) is issuing this information notice (IN) to alert
addressees to plugging of the high-pressure safety injection pump lubrication oil coolers with
lakeweed, which occurred at the Kewaunee Nuclear Power Plant (KNPP), a pressurized-water
reactor, during full-power operations. The NRC expects recipients to review the information
in this notice 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 and, therefore, do not require any specific action or written response.
Description of Circumstances
At the time of this event, the safety injection pump lubrication (lube) oil coolers at KNPP
were horizontal, straight tube, two-pass heat exchangers with twenty G-inch (0.95-cm)
(outer diameter) tubes per pass. Lubrication oil from the high-pressure safety injection pumps
circulated on the shell side, and service water from Lake Michigan passed through on the tube
(service water) side.
On January 15, 2004, during a routine quarterly maintenance inspection of the A safety injection
pump lube oil cooler, visual examination revealed silt and biological blockage (lakeweed)
at 17 of 20 tube pass inlets. The "as-found" tube-side flow measured 3.0 to 3.8 gallons/minute
(gpm) (11.4 to 14.4 liters/minute, lpm) before cleaning, and 5.95 to 6.05 gpm (22.5 to 22.9 lpm)
after cleaning. This concern prompted an investigation into the condition of the B safety
injection pump lube oil cooler, during which the licensee determined that 17 of 20 tubes in each
pass of this cooler were also blocked. A flow test, conducted with the cooler's end bell
removed, revealed that there was no flow from 17 of the 20 tubes, as seen from the outlet of
the cooler, and the "as-found" flow rate measured similar to that of the A safety injection pump
lube oil cooler.
1 Throughout this report, "lakeweed" is considered a mixture of plant fiber, diatom, algae filament, fungi, protozoa, and bacteria. The licensee and the NRC believe that the small tube diameter and tube sheet design
contributed to the lakeweed fouling on the tube side of the lubrication oil coolers.
The licensee determined that this condition had potentially rendered both safety injection pump
trains inoperable, and this discovery raised doubts regarding the future operability of the safety
injection pumps. As a result, plant operators declared both trains of the high-pressure safety
injection system inoperable at 12:20 a.m. on January 16, 2004, and initiated a plant shutdown
at 1:20 a.m. the same day.
Discussion:
Generic Letter (GL) 89-13, Service Water System Problems Affecting Safety-Related
Equipment, requested that licensees evaluate system heat exchangers that perform safety- related functions. The NRC also requested that licensees initiate a maintenance, test, and
inspection program (as necessary) to comply with GL 89-13 and General Design Criterion (GDC) 44, Cooling Water, as defined by Appendix A to Title 10, Part 50, of the Code of
Federal Regulations (10 CFR Part 50). The GL further stated that licensees programs should
account for heat exchanger fouling, plugging, and the potential for reduced flow and heat
removal capability.
With respect to safety injection pump coolers, the operability assessment would (as a minimum)
evaluate the delivered flow with the service water system in accident alignment, service water
temperature at its design limits (upper and lower bounds), and the safety injection pump moving
fluid at accident temperatures for a prolonged period of time (i.e., for the duration of the post- accident function).
Operating experience at KNPP and another operating plant shows that fouling with lakeweed
is a concern with heat exchangers that have an inner diameter (ID) of less than 1/2 inch
(1.27 cm). This concern is heightened if the heat exchanger in question is in a low point
in the system and experiencing low flow. Coolers with higher flow velocities and larger diameter
heat exchanger tubes have been shown to be less susceptible to fouling and flow blockage.
The higher velocities tend to keep solids suspended, and the larger diameter tubing provides
less potential for the accumulation of lakeweed or other marine organisms at the tube inlets.
Instances of lakeweed fouling of safety-related heat exchangers have occurred at other sites, as follows (this is not an all-inclusive list):
- Point Beach Nuclear Plant experienced lakeweed clogging of the G1/G2 diesel coolers.
The heat exchangers had G-inch (0.95-cm) tubes.
- R.E. Ginna Nuclear Power Plant has diesel generator cooling with two lube oil and
jacket water heat exchangers in series, one with G-inch (0.95-cm) tubes, and the other
with 1/2-inch (1.27-cm) tubes. Ginna has not experienced significant blockage of the
larger tubing but has reported blockage on the smaller tubing and continues to monitor
lakeweed fouling on all the heat exchangers. * Brunswick Steam Electric Plant, Unit 1, noted that cooling flow to both residual heat
removal pump seal coolers was approximately 1 gpm (3.8 lpm). The licensee removed
the coolers from service and found that they were partially filled with silt. The seal
coolers are in a low point of the service water system. Upon opening these coolers, the
licensee frequently discovers lakeweed creating a matte over the inlet tubesheets.
Licensees need to be aware that plugging and blockage of heat exchanger tubing attributable
to a buildup of silt, sand, or biological material may decrease the ability of the heat exchanger
or cooler to perform its required heat removal function. This may also affect other safety- related components, such as pumps; emergency diesel generators; and heating, ventilation, and air conditioning equipment, causing them to potentially fail when called upon to perform
their safety-related function.
This information notice does not require any specific action or written response. If you have
any questions about the information in this notice, please contact one of the technical contacts
identified below or the appropriate project manager in the NRCs Office of Nuclear Reactor
Regulation (NRR).
/RA/
William D. Beckner, Chief
Reactor Operations Branch
Division of Inspection Program Management
Office of Nuclear Reactor Regulation
Technical Contacts: Robert G. Krsek, Region III Jack W. Foster, NRR
(920) 388-3156 (301) 415-3647 Email: rgk@nrc.gov Email: jwf@nrc.gov
John G. Lamb, NRR Steven M. Unikewicz, NRR
(301) 415-1446 (301) 415-3819 Email: jgl1@nrc.gov Email: smu@nrc.gov
Attachment: List of Recently Issued NRC Information Notices
ML040770145 OFFICE OES:IROB:DIPM Tech Editor PM:PDIII-2 SC:PDIII:DLPM EMEB
NAME JWFoster PGarrity JGLamb LRagahavan SUnikewicz
DATE 03/17/2004 03/11/2004 03/17/2004 03/17/2004 03/18/2004 OFFICE SC:EMEB D:DE OES:IROB:SC C:IROB:DIPM
NAME DTerao RJBarrett CJackson WDBeckner
DATE 03/17/2004 03/19/2004 04/07/2004 04/07/2004
Attachment 1 LIST OF RECENTLY ISSUED
NRC INFORMATION NOTICES
_____________________________________________________________________________________
Information Date of
Notice No. Subject Issuance Issued to
_____________________________________________________________________________________
2004-06 Loss of Feedwater Isokinetic 03/26/2004 All holders of operating licensees
Sampling Probes at Dresden for nuclear power reactors except
Units 2 and 3 those who have permanently
ceased operations and have
certified that fuel has been
permanently removed from the
reactor vessel.
2004-05 Spent Fuel Pool Leakage to 03/03/2004 All holders of operating licensees
Onsite Groundwater for nuclear power reactors (except
those who have permanently
ceased operations and have
certified that fuel has been
permanently removed from the
reactor vessel) and for research
and test reactors, and all holders
of fuel storage licenses and
construction permits.
2004-04 Fuel Damage During Cleaning 02/24/2004 All holders of operating licenses
at a Foreign Pressurized Water for light-water reactors, except
Reactor those who have permanently
ceased operations and have
certified that fuel has been
permanently removed from the
reactor.
2004-03 Radiation Exposures to 02/24/2004 All well-logging licensees.
Members of the Public in
Excess of Regulatory Limits
Caused by Failures to Perform
Appropriate Radiation Surveys
During Well-logging
Operations
Note: NRC generic communications may be received in electronic format shortly after they are
issued by subscribing to the NRC listserver as follows:
To subscribe send an e-mail to <listproc@nrc.gov >, no subject, and the following
command in the message portion:
subscribe gc-nrr firstname lastname
______________________________________________________________________________________
OL = Operating License
CP = Construction Permit