Part 21 Report - 1997-302
ACCESSION #: 9705140420
LICENSEE EVENT REPORT (LER)
FACILITY NAME: Hope Creek Generating Station PAGE: 1 OF 6
DOCKET NUMBER: 05000354
TITLE: Struthers-Dunn 219NE Series Relay Failures Due to Thermal
Degradation of Magnetic Vinyl Plastic Bearing Pad
Material
EVENT DATE: 04/07/97 LER #: 97-007-00 REPORT DATE: 05/07/97
OTHER FACILITIES INVOLVED: DOCKET NO: 05000
OPERATING MODE: 1 POWER LEVEL: 100
THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR
SECTION:
50.73(a)(2)(v) OTHER
LICENSEE CONTACT FOR THIS LER:
NAME: Paul Duke, Sr. Staff Engineer TELEPHONE: (609) 339-1466
COMPONENT FAILURE DESCRIPTION:
CAUSE: B SYSTEM: BI COMPONENT: RLY MANUFACTURER: S440
REPORTABLE NPRDS: Y
SUPPLEMENTAL REPORT EXPECTED: NO
ABSTRACT:
On April 7, 1997, Public Service Electric & Gas Co. (PSE&G) completed
its evaluation of an increase in the failure rate of Struthers-Dunn 219NE
series relays with 120 VAC and 24 VAC coils and concluded that the
failures were due to the use of magnetic vinyl plastic for the bearing
pad material in normally energized relays. Based upon the extent of the
condition, PSE&G concluded that, if undiscovered, it could have caused
one or more safety systems to fail to perform their intended function. A
four hour notification was made to the NRC at 1848 on April 7, 1997,
pursuant to 10CFR50.72(b)(2)(iii). This LER is being submitted pursuant
to 10 CFR 50.73(a)(2)(v) and 10 CFR 21. The apparent cause of the high
failure rate was thermal degradation of the magnetic vinyl plastic
bearing pad material in Struthers-Dunn 219NE series 24 VAC and 120 VAC
relays. Panels containing the degraded relays are being inspected weekly
to assure continued operability until the relays are replaced. The
degraded relays will be replaced before the end of Hope Creek's seventh
refueling outage. There were no actual safety consequences associated
with this condition. There was no impact on public health and safety.
END OF ABSTRACT
TEXT PAGE 2 OF 6
PLANT AND SYSTEM IDENTIFICATION
General Electric - Boiling Water Reactor (BWR/4)
Station Service Water System - EIIS Identifier {BI}
Intake Structure HVAC System - EIIS Identifier {UA}
Remote Shutdown Panel - EIIS Identifier {JL}
IDENTIFICATION OF OCCURRENCE
Discovery date: 04/07/97
Problem Report: 970306444
CONDITIONS PRIOR TO OCCURRENCE
The plant was in OPERATIONAL CONDITION 1 (POWER OPERATION) at 100% of
rated thermal power. There were no other structures, systems, or
components that were inoperable at the beginning of the event that
contributed to the event.
DESCRIPTION OF OCCURRENCE
On April 7, 1997, PSE&G completed its evaluation of an increase in the
failure rate of Struthers-Dunn 219NE series relays with 120 VAC and 24
VAC coils and concluded that the failures were due to the use of magnetic
vinyl plastic for the bearing pad material in normally energized relays.
A walkdown of the Class 1E panels containing 219NE series relays
identified 170 relays with magnetic vinyl plastic bearing pads. Forty
eight (48) of these relays had degraded bearing pads. Based upon the
extent of the condition, PSE&G concluded that, if undiscovered, it could
have caused one or more safety systems to fail to perform their intended
function. A four hour notification was made to the NRC at 1848 on April
7, 1997, pursuant to 10CFR50.72(b)(2)(iii).
The bearing pad functions as a silencer at the pivot point of the hinged
armature plate. It is mounted on a metal frame with the relay coil and
the armature. Failure of the bearing pad affects the alignment between
the armature and the AC relay coil and causes rapid oscillatory motion of
the relay armature and contacts. The rapid motion is observable as a
loud buzzing or chattering from the relay. Relay failure eventually
results. The length of time from the onset of rapid oscillatory motion
and eventual failure cannot be precisely quantified. However, it is on
the order of weeks based on experience with relays observed to be
buzzing.
TEXT PAGE 3 OF 6
DESCRIPTION OF OCCURRENCE (continued)
PSE&G conducted a walkdown of the fifty one Class 1E panels containing
219NE series relays. A total of forty eight (48) relays with degraded
bearing pads were identified in the following applications:
- Forty four (44) relays in the Remote Shutdown Panel (RSP);
- Three (3) relays in the Station Service Water System (SSWS) vacuum
breaker controls; and
- One (1) relay in the Traveling Screen Motor Room Ventilation System
controls.
One of the relays with degraded bearing pads in the RSP was observed to
be buzzing and was replaced. Degraded bearing pads were observed only in
AC relays with magnetic vinyl plastic bearing pad material. The walkdown
also identified a total of 122 relays that have magnetic vinyl plastic
bearing pads that are not degraded and two (2) relays were found to have
been assembled with no bearing pad. None of these relays were observed
to be chattering or buzzing.
With the exception of the relays in the SSWS vacuum breaker controls, all
of the degraded relays are located in mild EQ environments. The SSWS
vacuum breaker control relays are located in a harsh environment, but
they were not included in the Hope Creek Equipment Qualification (EQ)
program. The qualified life for these relays is calculated to be 11.6
years (expires November 24, 1997).
Continued operability of the affected systems is assured by performing
panel walkdowns weekly to identify relays that have begun buzzing (an
indicator of degradation to the point that rapid armature motion is
occurring) and taking immediate action if any buzzing is detected.
The relay manufacturer, Struthers-Dunn, stated that magnetic vinyl
plastic was used in 219NE series relays until April, 1983. The design
was changed to use silicone rubber after that time. However, PSE&G has
identified one relay with magnetic vinyl plastic bearing pad material
that was manufactured in 1985. The bearing pad material can be
identified by color: magnetic vinyl plastic is brown; silicon rubber is
red; and Teflon is white.
TEXT PAGE 4 OF 6
DESCRIPTION OF OCCURRENCE (continued)
This event is being reported pursuant to 10CFR50.73(a)(2)(iii) as a
condition that could have prevented the fulfillment of a safety function.
This report is also being submitted in accordance with 10 CFR 21 as a
defect which could result in a loss of safety function necessary to
mitigate the consequences of an accident.
The affected relays are Struthers-Dunn series 219NE 120 VAC (model number
219BBX222NE) and 24 VAC (model number 219BBX232NE) relays with magnetic
vinyl plastic bearing pad material. The relays were supplied to PSE&G by
Comsip, the vendor for many of the Hope Creek plant panels.
APPARENT CAUSE OF OCCURRENCE
The apparent cause of the high failure rate was thermal degradation of
the magnetic vinyl plastic bearing pad material in Struthers-Dunn 219NE
series relays with AC coils. The thermal degradation is due to exposure
to high temperatures when the relay coils are energized. Thermal
degradation causes the bearing pad to disintegrate and become dislodged
from the relay frame.
TEXT PAGE 5 OF 6
ASSESSMENT OF SAFETY CONSEQUENCES
Three (3) of the four (4) relays controlling the Station Service Water
System (SSWS) vacuum breakers were found to have degraded magnetic vinyl
plastic bearing pads. The SSWS is designed to operate during normal
plant operation and during a design basis accident, including a LOCA,
loss of offsite power (LOP), and a LOCA with LOP conditions. Normally
closed solenoid operated valves, two per loop for redundancy, are located
at the highest point of each SACS heat exchanger discharge pipe.
Following a LOP, these valves fail open to admit air and close after a
preset time delay following restoration of power. This arrangement
reduces the pressure surge caused by the subsequent restart of all
station service water pumps to within design limits.
Multiple failures of the degraded relays could prevent the vacuum
breakers from remaining open for the preset time delay following
restoration of power after a LOP. This could potentially increase pipe
support loads beyond the current analyzed levels and result in failure of
the pressure boundary. This could result in the loss of a SSWS loop.
Quarterly testing of the SSWS vacuum breakers per the Hope Creek
Inservice Testing (IST) program minimized the potential for undetected
failures of the degraded relays.
Forty four (44) relays with degraded magnetic vinyl plastic bearing pads
were found in the Remote Shutdown Panel (RSP). Of these, twenty seven
relays supply indicators or alarms required by plant Technical
Specifications. The Remote Shutdown System (RSS) provides the means for
achieving and maintaining safe shutdown conditions from outside the main
control room in the unlikely event the main control room becomes
uninhabitable. The primary control station for the RSS is the remote
shutdown panel (RSP). Multiple failures of the degraded relays could
render the RSP inoperable. However, in the event of a failure at the
RSP, sufficient redundant safety grade instrumentation and controls are
available apart from both the main control room and the RSP to ensure
that safe shutdown of the reactor can be achieved.
One (1) relay with a degraded magnetic vinyl plastic bearing pad was
found in the damper controls for one train of the Traveling Screen Motor
Room Ventilation System. The traveling screen room is provided with two
100 percent capacity supply fans, each with motorized outside air intake
and return air dampers and one common exhaust opening with backdraft
damper. Failure of the degraded relay would not affect the redundant
train and would not prevent the system from performing its function.
TEXT PAGE 6 OF 6
ASSESSMENT OF SAFETY CONSEQUENCES (continued)
There were no actual safety consequences associated with this condition.
There was no impact on public health and safety. Therefore, the safety
consequences associated with this event were negligible.
PREVIOUS OCCURRENCES
No previous occurrences similar to this condition were identified in a
review of Hope Creek LERs.
CORRECTIVE ACTIONS
1. As of May 1, 1997, six (6) of the Struthers-Dunn 219NE series relays
with degraded magnetic vinyl plastic bearing pad material have been
replaced.
2. Panels containing Struthers-Dunn 219NE series relays with degraded
magnetic vinyl plastic bearing pad material are being inspected
weekly to ensure continued operability until the relays are
replaced.
3. Struthers-Dunn 219NE series relays with degraded magnetic vinyl
plastic bearing pad material will be replaced as soon as possible
within the Hope Creek work week schedule. Replacement will be
complete before the end of Hope Creek's seventh refueling outage.
4. Normally energized Struthers-Dunn 219NE series 120 VAC (model number
219BBX222NE) and 24 VAC (model number 219BBX232NE) relays with no
bearing pad or with non-degraded magnetic vinyl plastic bearing pad
material will be inspected to verify no degradation. The results of
this inspection will be assessed to determine the need for
additional inspections until the relays are replaced. This activity
will be completed by August 29, 1997.
5. The SSWS vacuum breaker relays that were omitted from the EQ Program
have been added to the program and will be replaced before the end
of their qualified life (November 24, 1997).
6. Normally energized Struthers-Dunn 219NE series 120 VAC (model number
219BBX222NE) and 24 VAC (model number 219BBX232NE) relays with no
bearing pad or with non-degraded magnetic vinyl plastic bearing pad
material will be replaced before the end of their calculated service
life (April 15, 1998)
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