Information Notice 2001-19, Improper Maintenance and Re-Assembly of Automatic Oil Bubblers
| ML013020195 | |
| Person / Time | |
|---|---|
| Issue date: | 12/17/2001 |
| From: | Imbro E Operational Experience and Non-Power Reactors Branch |
| To: | |
| References | |
| TAC MB3043 IN-01-019 | |
| Download: ML013020195 (5) | |
UNITED STATES
NUCLEAR REGULATORY COMMISSION
OFFICE OF NUCLEAR REACTOR REGULATION
WASHINGTON, DC 20555-0001 December 17, 2001 NRC INFORMATION NOTICE 2001-19: IMPROPER MAINTENANCE AND REASSEMBLY OF
AUTOMATIC OIL BUBBLERS
Addressees
All holders of operating licenses 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 to alert
addressees to recent problems resulting from improper maintenance and reassembly of
automatic oil bubblers. The NRC expects all recipients to review the information for
applicability to their facilities and consider actions, as appropriate, to avoid potential problems.
However, the recommendations contained in this information notice do not constitute NRC
requirements; therefore, this information notice does not require any specific actions or written
response.
Background
Recent problems raised concerns regarding improper maintenance and reassembly of
automatic oil bubblers. These oil bubblers are used to maintain the oil level in the pump
bearing housing of safety-related equipment. Blockage of oil flow from the bubbler, along with
periodic loss of oil through equipment operation and routine oil sampling, could deplete the oil
level to the point where severe equipment damage could result. This issue was first identified
at Millstone Nuclear Power Station Unit 2, in August 2000, then at Joseph M. Farley Nuclear
Plant, Unit 1 in January 2001, and later at Seabrook in June 2001. The degraded oil bubblers
at Seabrook involved both emergency feedwater pumps.
The concern arises when the oil feed pipe entering the bottom of the oil bubbler extends
beyond the threaded fitting (protruding too far into the housing), thereby allowing the pipe to
make contact with the level adjuster (flat disc) mechanism. The contact between the oil feed
pipe and the disc could block the essential oil flow from the bubbler to the bearing reservoir.
(See attachment 2.)
Discussion
Within the past year, two power plants have experienced a situation that resulted in the
malfunction of the automatic oiler feature for the bearings on safety-related equipment. The
Trico Opto-Matic oiler that malfunctioned is commonly used in many applications in power
plants; therefore, the potential exists for similar malfunctions to affect other plant components.
Plant personnel typically use the oil level in the glass reservoir as a visual indication that an
adequate supply of oil is available to replenish the reservoir of the component on which it is
installed. The oil for the equipment reservoir is supplied via a 1/4 inch threaded pipe that can be
connected through either the side of the lower housing or from the bottom (Attachment 2, figure a.) The problem arises when the supply piping (1/4 inch, 18-NPT, threaded connecting
nipple) is threaded into the oiler base so far that the pipe begins to protrude into the lower base
of the oiler (Attachment 2, figure b.) In both plants that experienced this problem, the oil
bubbler involved was an early Trico design from the 1970s, which contained a flat-based
spider assembly that controlled the flow of oil from the bubbler to the equipment being supplied.
Trico has since changed the design of the oil bubbler spider assembly to incorporate a
concave-shaped spider base (Attachment 2, figure c.) This design minimizes the potential for
the connecting pipe to make contact with the spider base by extending a total of d inch above
the oiler base supply port. As a result, this design greatly minimizes the potential for a flow
restriction to develop between the bubbler reservoir and the equipment bearing housing. The
potential for problems exists only when the oiler feed supply line is connected to the bottom of
the oiler base with a flat-based spider assembly.
The EPRI's Nuclear Maintenance Application Center (NMAC) and the NMAC Pump Users
Group recommend that licensees take the following actions to ensure that this condition does
not affect equipment performance and availability:
(1) Verify existing oil levels using redundant means, such as a dipstick with secured
equipment or visual inspection through the equipment oil reservoir sample/inspection
ports while the pump is running.
(2) As soon as possible, determine if the connecting fitting protrudes into the base of the
Trico oil bubbler housing, by removing the bubbler bulb and spider assembly and feeling
the bottom of the bubbler base for the protruding 1/4 inch fitting.
(3) At the earliest opportunity, install oil bubblers with the concave-style spider assembly to
avoid the possibility of an improperly functioning oiler or oil level indication.
(4) Change the applicable procedures so that oil change/sampling, and post-maintenance
test procedures fill the oil reservoir using a consistent technique as recommended.
Additional detailed information can be found in NRC Inspection Report 50-443/01-07, SEABROOK STATION - NRC INSPECTION REPORT, dated July 27, 2001, Accession
- ML012110281. 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 the technical contact listed
below or the appropriate project manager in the NRCs Office of Nuclear Reactor Regulation
(NRR).
/RA/
Eugene V. Imbro, Acting Chief
Operational Experience
and Non-Power Reactors Branch
Division of Regulatory Improvement Programs
Office of Nuclear Reactor Regulation
Technical contacts: Omid Tabatabai, NRR Javier Brand, Region 1
(301) 415-3738 (603) 474-3589 E-mail: oty@nrc.gov E-mail: jmb3@nrc.gov
Attachments:
1. List of Recently Issued Information Notices
2. Trico Opto-Matic Oil Bubbler figures
ML013020195 Template #: NRR-052 OFFICE REXB TECH ED DSSA/SPLB REG I:RI REG I: SR:RI
NAME OTabatabai* PPuccio* JHannon JBrand*oty GDentel*oty
DATE 10/16/2001 10/12/2001 12/17/2001 10/17/2001 10/17/2001 OFFICE REG I:DRP REXB REXB AC:REXB
NAME CCowgill*oty CPetrone* JTappert EVImbro
DATE 10/17/2001 10/24/2001 12/11/2001 12/17/2001
Attachment 1 IN 2001-18 Page 1 of 1 LIST OF RECENTLY ISSUED
NRC INFORMATION NOTICES
____________________________________________________________________________
____________________
Information Date of
Notice No. Subject Issuance Issued
to
____________________________________________________________________________
____________________
2001-18 Degraded and Failed Automatic 12/14/2001 All uranium fuel conversion, enrichm
Electronic Monitoring, Control, fabrication licenses and certificate h
Alarming, Response, and authorized to receive safeguards in
Communications Needed for Information notice is not available to
Safety and Safeguards public because it contains safeguar
information.
2001-17 Degraded and Failed Performance 12/14/2001 All uranium fuel conversion, enrichm
of Essential Utilities Needed for fabrication licenses and certificate h
Safety and Safeguards authorized to receive safeguards in
Information notice is not available to
public because it contains safeguar
information.
2001-08, Update on Radiation Therapy 11/20/2001 All medical licensees
Sup. 2 Overexposures in Panama
2001-16 Recent Foreign and Domestic 10/31/2001 All holders of operating licenses for
Experience with Degradation of pressurized-water reactors (PWR),
steam Generator Tubes and those who have permanently cease
Internals operations and have certified that fu
been permanently removed from th
2001-15 Non-Conservative Errors in 10/29/2001 All holders of operating licenses or
Minimum Critical Power Ratio construction permits for boiling wate
Limits (BWRs)
OL = Operating License
CP = Construction Permit