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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