Information Notice No. 88-88: Degradation of Westinghouse ARD Relays
UNITED STATES
NUCLEAR REGULATORY COMMISSION
OFFICE OF NUCLEAR REACTOR REGULATION
WASHINGTON, D.C. 20555
November 16, 1988
NRC INFORMATION NOTICE NO.: 88-88: DEGRADATION OF WESTINGHOUSE ARD RELAYS
Addressees:
All holders of operating licenses or construction permits for nuclear power
reactors.
Purpose:
This information notice is being provided to alert addressees to problems
identified in Westinghouse ARD relays. It is expected that recipients will
review the information for applicability to their facility 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:
Pacific Gas and Electric Co. (PG&E or licensee) notified the Nuclear
Regulatory Commission of a deficiency identified in Westinghouse ARD relays at
its Diablo Canyon Power Plant, Unit 1, in Licensee Event Report (LER)
50-275/88-009, dated May 26, 1988. PG&E indicated that during the period from
December 1, 1987, to April 7, 1988, seven Westinghouse 125-Vdc ARD relays were
found to have increased drag between the solenoid's coil spool and the
armature.
Discussion:
PG&E reported in their LER that during an investigation of load fluctuations
on diesel generator (DG) 1-1 on December 1, 1987, a 125-Vdc Westinghouse ARD
relay solenoid armature was found to have an increased drag. The relay was
replaced the following day after the problem was attributed to an increased
resistance caused by dust on the relay contacts. In February 1988, during re-
placement of equivalent relays in the Unit 1 and Unit 2 DGs, four ARD relays
were found to have increased drag on the solenoid armature. PG&E determined
that the increased drag was caused by granules from the coil potting compound
lodging between the solenoid's coil spool and the armature that moves inside
the coil spool. The coil potting compound, a sand-based material, had appar-
ently deteriorated, and granules had migrated to the coil spool area where
they lodged between the coil spool and the armature. The increased solenoid
armature drag resulted in increased relay contact resistance that affected the
signal transmitted by these relays in low-voltage and voltage-sensitive
circuits. The relays are Westinghouse 8-pole relays with 125/130-Vdc coils,
catalog numbers ARD440 and ARD660.
8811090403
. IN 88-88
November 16, 1988
Page 2 of 2
The licensee replaced the four relays and to confirm the cause of the
failures, sent three of these relays to Westinghouse for further analysis.
Westinghouse informed PG&E that the relay failures were indeed caused by the
potting compound granules lodging between the coil spool and the armature.
Further investigation by the licensee and Westinghouse determined that
sand-based coil potting compound had been used in certain 125-Vdc relays
manufactured before 1972. The resin used in the potting material apparently
breaks down with age. Westinghouse recognized this type of degradation in the
1970s and thereafter ceased to use a sand-based potting compound in relays
qualified by them as Class 1E components. PG&E purchased the relays as
commercial grade and was not aware of the aging characteristic of the potting
material.
According to PG&E and Westinghouse, in-place identification of relays with a
sand-based potting compound may be possible through a close inspection of the
coil terminal tab. A rectangular opening in this tab where it enters the coil
block may reveal a small sample of the potting material. A light brown,
coarse-appearing potting material is suspected as being sand based. Black or
yellow-brown, smooth-appearing material does not demonstrate the same
degradation.
During the performance of planned maintenance on April 7, 1988, PG&E personnel
identified two additional 125-Vdc Westinghouse ARD relays with increased drag.
PG&E personnel have replaced all the relays identified to have the increased
drag with relays that do not use a sand-based potting compound. The remaining
installed ARD relays with a sand-based potting compound are scheduled to be
replaced by PG&E.
No specific action or written response is required by this information notice.
If you have any questions regarding this matter, please contact the technical
contact 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 Contact: Jaime Guillen, NRR
(301) 492-1170
Attachment: List of Recently Issued NRC Information Notices
. Attachment
IN 88-88
November 16, 1988
Page 1 of 1
LIST OF RECENTLY ISSUED
NRC INFORMATION NOTICES
_____________________________________________________________________________
Information Date of
Notice No._____Subject_______________________Issuance_______Issued to________
88-87 Pump Wear and Foreign 11/16/88 All holders of OLs
Objects in Plant Piping or CPs for nuclear
Systems power reactors.
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
Page Last Reviewed/Updated Tuesday, March 09, 2021