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HomeNRC LibraryDocument CollectionsGeneral CommunicationsInformation Notices1994

# 

```

UNITED STATES
NUCLEAR REGULATORY COMMISSION
OFFICE OF NUCLEAR REACTOR REGULATION
WASHINGTON, D.C.  20555

August 16, 1994


NRC INFORMATION NOTICE 94-58:  REACTOR COOLANT PUMP LUBE OIL FIRE


Addressees

All holders of operating licenses or construction permits for
pressurized-water reactors.

Purpose

The U.S. Nuclear Regulatory Commission (NRC) is issuing this information
notice to alert addressees to a problem that may exist with the oil collection
system for the lube oil system components of reactor coolant pumps.  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 are not
NRC requirements; therefore, no specific action or written response is
required.

Description of Circumstances

Haddam Neck Plant

On July 11, 1994, while operating at 100 percent power, the licensee for the
Haddam Neck Plant received a low oil level alarm for the upper lube oil
reservoir of reactor coolant pump No. 3.  The licensee later observed that the
upper bearing temperature for reactor coolant pump No. 3 had been increasing
for approximately 6 hours prior to receiving the low oil level alarm and
reached 82 C [180 F].  The licensee began a controlled power reduction to
bring the plant to a power level condition which would allow the reactor
coolant pump to be taken out of service.  Simultaneously, a maintenance crew
was entering containment to fill the oil reservoir.  Upon entering
containment, the maintenance crew observed smoke just inside the airlock.  At
this time, the upper bearing temperature reached nearly 93 C [200 F], and
the licensee manually tripped the reactor from approximately 50 percent power.
The heat detectors installed above the reactor coolant pump went into alarm
approximately 50 minutes later.  At about the same time, the fire brigade
entered containment and reported a fire in the insulation around the pump
casing and nearby piping of reactor coolant pump No. 3.  The fire brigade
removed insulation and extinguished the fire using portable dry chemical fire
extinguishers.  A relief crew later observed a reflash on the remaining
insulation, removed this insulation, and extinguished the second fire.

The licensee determined that the oil leak and subsequent fire resulted from a
crack in a 1-inch diameter, schedule 80, threaded PVC fitting in the pump lube
oil system.  The PVC fitting was installed between the reactor coolant pump

9408100058.IN 94-58
August 16, 1994
Page 2 of 3


oil reservoir and the oil lift pump to electrically isolate the oil lift pump
from the reactor coolant pump motor.  The oil leaking from the crack was not
properly collected and routed away from high velocity cooling air, which blew
the oil onto the insulation on the pump casing and pipe.  The cooling air came
from the reactor coolant pump motor and the area ventilation system.  The high
temperature of the reactor coolant system (approximately 282 C [540 F])
ignited the oil-soaked insulation.  (The flash point of the lube oil is
approximately 204 C [400 F].)  The reservoir retained about 455 liters
[120 gallons] of the approximately 755 liters [200 gallons] of oil originally
in the reservoir.  About about 150 liters [40 gallons] of oil was collected by
the oil collection system, and 150 liters [40 gallons] leaked onto the
insulation and the containment floor.

Millstone Nuclear Power Station, Unit 2

On July 27, 1994, the lube oil low flow alarm for the `A' reactor coolant pump
annunciated at Millstone Unit 2.  Plant operators began reducing reactor power
in accordance with plant procedures.  Licensee personnel inspected all of the
reactor coolant pumps and found that oil had dripped from the tops of the `A'
and `D' pump motors, coating the outside of the motors.  Most of the oil was
contained by the oil collection drip pans; however, some of the oil that
leaked from the `A' pump motor was not contained.  Based on the observed fire
hazard in containment, the licensee shut down the plant.

After the plant was shut down, an NRC inspector examined the lube oil
collection system and the area around the reactor coolant pumps.  There were a
number of small oil leaks on each pump motor although there was more leakage
from the `A' pump motor.  The inspector observed that various equipment around
the `A' reactor coolant pump was coated with a film of oil and he estimated
that several gallons of oil had collected in various areas outside the oil
collection system.  The inspector also noted that portions of the lube oil
system were outside the oil collection system and that the collection system
piping did not appear to be large enough to accommodate the largest potential
oil leak.

Discussion

In pressurized-water reactors, each reactor coolant pump motor typically
contains between 530 and 830 liters [140 and 220 gallons] of oil.  Oil leaking
from the lube oil system may come in contact with either (1) surfaces that are
hot enough to ignite the oil, or (2) an electrical source of ignition.
Appendix R to Part 50 of Title 10 of the Code of Federal Regulations requires
the installation of an oil collection system to collect oil from all potential
pressurized and unpressurized leakage sites.  An adequately designed,
installed, and maintained oil collection system is necessary to contain any
oil released because of leakage or failure of the lubrication system and to
minimize fire hazards by draining the oil to a safe location.

There are a number of differences between the reactor coolant pump motors and
their associated lube oil systems at Millstone Unit 2 and Haddam Neck.  For
example, the Millstone Unit 2 motors do not use PVC or other synthetic
couplings in the lube oil system.  The Millstone Unit 2 reactor coolant pump
.IN 94-58 August 16, 1994
Page 3 of 3


motors are manufactured by General Electric Company while the motors at Haddam
Neck are manufactured by Westinghouse Electric Corporation.  However, the oil
collection systems at the two plants are similar.

The Haddam Neck oil collection system is intended to collect lube oil from all
potential leakage sites and to drain it to a vented, closed container to
prevent a fire during normal conditions or design basis accident conditions.
However, in this event the catch pan design, which relied on an unshielded
vertical flow of oil, was not adequate.  This design allowed the air flow
around the motor to affect the vertical movement of the dripping oil and
allowed it to escape the collection system.  To a lesser extent, the
ventilation system also created air currents in the vicinity of the pump,
which prevented some of the oil from being collected.

The licensee is installing a steel dielectric union on each reactor coolant
pump motor at Haddam Neck to replace the PVC fitting which failed and caused
the leak in this event.  The licensee is also modifying the oil collection
system to account for air currents near the reactor coolant pumps.

The ventilation system for the Millstone Unit 2 containment does not
contribute to the air flow around the reactor coolant pump motors.  The only
air flow in this area is caused by the motor itself.  In addition, Millstone
Unit 2 has installed mirror insulation on some of the piping in the vicinity
of the reactor coolant pumps.  This type of insulation would prevent oil from
coming in contact with and igniting on the high temperature piping it
insulates.  These factors reduce, but do not eliminate, the likelihood of
leaking lube oil reaching an ignition source.  However, the design of the
existing oil collection system was inadequate to contain existing and
potential oil leakage paths.  The licensee is evaluating modifications that
can be installed during the current forced outage to ensure that the lube oil
collection system for the reactor coolant pump motors meets the requirements
of Appendix R.

This information notice requires no specific action or written response.  If
you have any questions about the information in this notice, please contact
one of the technical contacts listed below or the appropriate Office of
Nuclear Reactor Regulation (NRR) project manager.

/S/'D BY BKGRIMES


Brian K. Grimes, Director
Division of Operating Reactor Support
Office of Nuclear Reactor Regulation

Technical contacts:  Edward A. Connell, NRR
                     (301) 504-2838

   Ralph J. Paolino, RI
   (610) 337-5285
Attachment:
List of Recently Issued NRC Information Notices
```

*Page Last Reviewed/Updated Wednesday, February 16, 2011*

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