United States Nuclear Regulatory Commission - Protecting People and the Environment

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, November 12, 2013