ML20206H297

Part 21 Rept Re Common Mode Failure for magne-blast Breakers.Vc Summer Nuclear Station Utilizes These Breakers in Many Applications,Including 7.2-kV EDG Electrical Buses

ML20206H297
Person / Time
Site:	Summer
Issue date:	05/05/1999
From:	Pease J SOUTH CAROLINA ELECTRIC & GAS CO.
To:	NRC
References
REF-PT21-99 NUDOCS 9905110154
Download: ML20206H297 (2)

Text

0G051999 U.S. Nuclear Regulitory Commisslo., Operations Center Event Report P;ge i Power Reactor Event # 35677 Site: SUMMER Notification Date / Time: 05/05/1999 10:17 (EDT)

Unit: 1 Region:'2 State : SC Event Date / Time: 05/02/1999 18:00 (EDT)

Reactor Type: [1] W-3-LP Last Mod,ification: 05/05/1999 Containment Type: DRY AMB NRC Notified by: JEFF PEASE Notifications: CHRIS CHRISTENSEN R2 HQ Ops Officer: LEIGH TROCINE JAMES LINVILLE R1 Emergency Class: NON EMERGENCY MONTE PHILLIPS R3 10 CFR Section: BILL JONES R4 21.21 UNSPECIFIED PARAGRAPH VERN HODGE (fax) NRR U, sit Scram Code RX Crit Init Power Initial RX Mode Curr Power Current RX Mode 1 N No O Refueling 0 Refueling -

GENERIC CONCERNS REGARDING A COMMON MODE FAILURE FOR MAGNE-BLAST BREAKERS l

Th3 following text is a portion of a facsimile received from the licensee:

"This is report is being made pursuant to 10CFR21.21 to identify a Substantial Safety Hazard with General Electric 7.2-kV Magne-Blast Breakers."

"On April 15,1999, V.C. Summer Nuclear Station submitted a potential Substantial Safety Hazard report due to 7.2-kV breakers which failed to close. After further investigation and testing, it has been determined that a Substantial Safety Hazard could exist with this failure to close. The identified problem deals with a cotter pin ,

striking the latch check switch mounting bracket and bending it forward. This removes the factory set clearance between the bracket and the switch actuating paddle. This results in the paddle, which is bolted to the trip shaft, j rolling the trip shaft to the trip position when the breaker attempts to close. The cotter pin problem is considered a defect in repair. This condition represents a potential for a common mode failure for Safety-Related Magne-Blast l breakers." m I

V "V.C. Summer Nuclear Station utilizes these breakers in many applications, including the 7.2-kV Emergency !f Di sel Generator electncal busas."

f "The function of the latch check switch is to enable rapid repeated breaker closures, which is not required in the V. C\

C. Summer application of these breakers. Engineering has determined that removal of the latch check switch, the ,\\ {

latch switch mounting bracket, and the actuating paddle will prevent recurrence of this problem in the future."

h j The licensee stated that this schon has already been taken on all of the safety-related breakers. However, this achon has not been taken for the non-safety-related breakers located in the balance of plant. These breakers are normally closed and stay closed throughout the cycle. The licensee stated that these are not restart items. All h:va been done with the exception of four, which feed the transformers for the 480-V switchgear.

The licensee notified the NRC resident inspector 990511011!4 990505 ^OOO PDR ADOCK 05000395 8 PDR j j

. ., NL-122 7

ATTACHMENTI k dp PAGE 1 OF 2 REVISION 2 Leau k m,

' WRc FORM 361 (06-1998) F

u. S. NUCLEAR REGULATORY COMMISSION NRC ONE HOUR NOTIFICATION OPERATIONS CENTER EVENT NOTIFICATION WORKSHEET TIME FACILITY OR ORGANIZATION UNIT ol7 NoTlFICATTn.s , Virgil C. Summer Nuclear Station 1 C3.LER'S NAME

/'ghr(

CALL BACK = : ENS or ( ) .

EVENT TIME & ZONE EVENT DATE 1.Hr Non-Emergency 10 CFR 50.72 (b) (1) (v) Lost Offsite Comms

/N 5 2-99 OXA) TS Required Shutdown ASHU (vi) Fire AESS AFIR POWER / MODE BEFORE POWER / MODE (i)(B) TS Deviation ADEV AFTER (vi) Toxic Gas ACHE 0 0 (i) Deoraded Condition ADEG (vi) Red Release ARAD OlXA) Unanalyzed Condition - AUNA (vi) Other Hampenne Safe Op AHIN EVENT CLASSIFICATIONS (W)(B) Outside Design Basis AouT 4-Hr. Non-Emergency 10 CFR 60.72(b)(2)

GENERAL EMERGENCY oEN/AAEC OiXC) Not Covered by ops /EPS ACNC 0) Degrade Whos S/D ADAS SITE AREA EMERGENCY SIT /AAEC (hi) Easthquake ALERT ANEA Ci) RPS Aduation(scram) ARPS ALE /AAEC 06i) Flood ANFL UNUSUAL EVENT (ii) ESF Actuation AESF UNU/AAEC (iii) Hurricane ANHU 50.72 NoN EMERGENCY (see New Colwnns) Ice / Hail (inXA) Safe S/D Cr~i AINA Cat) ANIC Dii)(B) RHR Capabety AINS PHYSICAL sECURfTY (73.71) D??? Oli) Lightning ANL1 TRANSPORTATION DiiXC) Control of RAD Release AINC NTRA (iii) Tornado ANTO (siXD) Accident Mit 2ation AINO 20.403 MATERIAL / EXPOSURE B??? (iii) Other Natural Phenomenon Ov)(A) Air Releaso > 2X App B AAIR ANOT OTHER: NDAM. NLCO, NL8L, NINF. Oy) ECCS Discharge to RCS ACCS NLTR, NONR OvXB) Liq Release > 2X App 8 AUO (v) Lost ENS AENS (v) Offsne rnedical AMED CDEF, FLOM, ElRR. GCON (v) Lost EE s Assessment AARC (vi) Offsite Notificaten APRE DESCRIPTION XX t DCFR21.21.a(1)

This is report is being made pursuant to 10CFR21.21 to identify a Substantial Safety Hazard with General Electric 7.2 kV Magne-Blast Breakers.

On April 15,1999, V.C. Summer Nuclear Station submitted a potential Substantial Safety Hazard report due to 7.2 kV breakers which failed to close. After further investigation and testing it has been determined that a Substantial Safety Hazard could exist with this failure to close. The identified problem deals with a cotter pin striking the latch check switch mounting bracket and bending it forward. This removes the factory set clearance between the bracket and the switch actuating paddle. This results in the paddle, which is bolted to the trip shaft, rolling the trip shaft to the trip position when the breaker attempts to close.

The cotter pin problem is considered a defect in repair. This condition represents a potential for a common mode failure for Safety-Related Magne-Blast breakers.

V. C. Summer Nuclear Station utilizes these breakers in many applications, including the 7.2 kV Emergency Diesel Generator electrical buses.

' The function of the latch check switch is to enable rapid repeated breaker closures which is not ,

required in the V. C Summer application of these breakers. Engineering has determined that removal of the latch check switch, the latch switch mounting bracket, and the actuating paddle will prevent recurrence of this problem in the future.

Include: Systems affected, actuations & their initiating signal, causes, effects of event on plant, aChons taken or planned, etc.

NOTIFICATIONS YES NO WILL ANYTNING UNUSUAL OR NOT UNDER$TOOO? YES NO NRC RESIDENT )O( BE (Explain

)Q(

above)

STATE (s) NO N/A Dt0 ALL SYSTEMS FUNCTION AS REQUIRED? YEs (Explain above)

LOCAL N/A N/A HER GOV AGENCIES XX MODE oF OPERATION ESTIMATE FoR ADDITIONAL INFO

.DIA/ PRESS RELEASE XX UNTilCORRECTED: N/A RESTART DATE: N/A ON BACK7 NO NRC FORM ast 40s.teet) -

. <a e ese, s,c t e rra taa-a -a