ML18031A335

Final Deficiency Rept Re Insulation Damage to Wiring in Control Room Inserts 72C & 73C Which Are Part of Offsite Standby Diesel Generator Controls.Caused by Wire Routing Over Steel Barrier Severing Conductor Insulation

ML18031A335
Person / Time
Site:	Susquehanna
Issue date:	12/17/1979
From:	PENNSYLVANIA POWER & LIGHT CO.
To:
Shared Package
ML18031A334	List: ML18031A333 ML18031A335
References
840-4, NUDOCS 7912270308
Download: ML18031A335 (3)

Text

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FIN.V REPORT ON INSULATION DAMh,GE DEFICIENCY IH CONTROL ROOM IN~RTS 72C A'H) 73C

~Sub ect Panel OC653 Inserts 72C and. 73C While attmpting to perform the tasks delineated on GE's field vork in-struction, on insert modules 72C and 73C from plant Operating Benchboard OC653 (GE H12-P853), Bechtel noted that internal wiring (14ANG) paralleling conduit numbers 15, 18, 19, 20 and 21 (4, 2, 1, 2 and. 2 conductors, respective1y) vere damaged. on insert 73C.

5he above stated nonconformance vas documented, in NCR 3760.

The subject inserts vere returned to GE - San Jose manufacturing facility for inspection, repair/rework a& check out. Insulation damage vas also discovered in insert 72C. We insoection findings are documented by the GE Evaluation of Susquehanna I H12-P853 Inserts 72C and 73C dated. May 15, 1979.

It appears that the vire insulation damage occurred because the viring was routed over the sharp edge of a steel barrier, and the metal flexible conduit locknuts vere, in some instances, installed in a manner which caused cr~ing and severing of the conductor insulation. These defects vent urdetected. during GE-QA's in-process and pre-shipment inspection for damage and manufacturing defects.

Analysis of Safety Implications The system design vas reviewed on the basis of the damages docume..ted in the GE Evaluation of Susquehanna I H32-P853 (OC653) Insert 72C and 73C dated MW 15, 15V9.

We damaged. viring is part of the tvo off-site power system feeder 4.16 kV circuit breaker controls and the fou" standby AC Diesel Generator 4.16 kV feeder breaker controls.

The offsite pover feeder breakers are required to trip uoon loss of voltage at each of the four 4.16 kV standby AC buses'imultaneously, the undervoltage condition of each bus starts the respective standby AC Di.esel Gererator, When rated speed. and voltage are reached., each Diesel Generator ci cuit breake is automatically closed. into its dead. ous that has oeen disconnected frcm both offsite power sou"ces. These buses serve redundar. emergency core cooley pcs and related. equipment (i.e., HER, Core Spray, etc.), and. are required for e ergency shutdo~w. Tne four Diesel Generators are considered redundant to each othe" and separated. accordingly.

ATTACHMENT 1 page 2 of 2 3:nserts 72C and 73C contain the two offsite power supply feeder breaker control switches and synch onizing switches to each of the four 4.16 kV buses.

Mditionally, they conta'n the four Diesel Generator breaker controls and z'elated synchronizing switches. Other non-safety related canponents are present.

The deficiencies re~orted identify a condition where the negative of the 125 V DC control po~er of tne Diesel Generator breaker control closing circuit and the positive of the tripping circuit could have been damaged. and shorted. to panel steel.

r

%he closing and tripping ci"cuits are independently fused but supplied from the same 325 V DC power source. The resulting short would have blown the positive tripping circuit fuse and the negative closing circuit fuse.

5he closing circuit fuse, if blown, would disable the closing circuit of the Diesel Generator feeder breaker including the automatic close signal.

ghe deficiency described above, failure of if uncorrected, could permit shorting and redundant Standby AC Diesel Generator 4.l~kV feeder breaker controls which could prevent the circuits from performing the designed safety function.

Since the occur."ence of damaged wiring is rardom and coul) occur in any and. all Diesel Generator feeder breaker control circuits, the possibility of a failure exists. Tne simultaneous degradation and loss of the Standby AC Diesel Gene ator power supplies could result in a safety hazard to the operation of the plant.

Xt has been concluded that the insert 72C and 73C wire insulation damage is reportable under 10CFR ,'0.55(e).

Corrective Action inserts 72C and, 73C were retu"ned to GE-San Jose, the manufacturer, for repair/rework.

QE disassenbled both inserts down to bare metal. The insert steel was stripped.,

repainted and devices were checked, replaced/reinstalled and ewi."ed.. Yanufacturing ark Qh procedures were in place to assure wiring did not come in contact with sharp edg steel barriers and conduit fittings. The inserts were 10+ visually inspected 'f and functionally checked by G--QJ to verify circuit continuity, ope ation and con-dition. The inserts have been returned to the site and reinstalled.

ATTACHMENT 2 Page l of 1

( JItL 979 'l OG5g~

G EN ERAL ~~c". E LECTR I C NUCLEAR ENERGY P ArrIE QcT Snro tb4V 48 0 N ttej. Sgr.

GENERAL ELECTRIC CCIMPANY, ET5 CVRTNER AVESAN JCSE, CAUFORNIA 95125 ate/. rap.

SAO NC 394, (408) 925-3005 *W 0$

DM R

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July S, 1979 Responds to: N/A EI.CCT ilt GP 79-92 L 9 1S7 D Umem CMS free. Ngr tUltM th )+

.1HSPC Hr. R. J, Shovlin. Assistant Pro5ect Ss~

Director - Susquehanna 4

.CD5T Pennsylvania Power 5 Light Company Two North Ninth Street Allentown, PA 18101 OUAI.ITY ENGINEERING

SUBJECT:

SUSQVEHANHA 1 5 2 INSERTS 72C ANO 73C - POTENTIAL REPORTABLE CONDITION Follo~ing a review of the conditions existing on the sub5ect inserts as deterTrrined by a detailed inspection in San Jose and discussions with Bechtel on circuit implications, General Electric has concluded that

'the deviations would not prevent or degrade any safety function. Thus, these deviations do not constitute a potential reportable condition within the context of 10CFR, Part 21.

A review of the list of deviations in the 72C and 73C inserts with Bechtel has determined that regardless of the deviations, the diesel generators would automatically be switched to the emergency bus.

The possibility of wires with frayed or cut insulation grounding against the frame was also investigated. The manual control for the 4.16KY distribution system is 125 volt'DC and is not grounded (the ground is floating). Therefore, any contact with the frame would not short the system and blow fuses or circuit breakers rendering the diesel generator inoperative.

Pleas'e contact rm. if you have any questions.

Very trul yours,

/

. Aillard

~ Pro5ect Hanager Susquehanna Pro5ect JMH:b5r/1001 cc: E. A. Gustafson ~J. R. Schrriedel File: 7.7