ML20212R369

Revised Part 21 & Deficiency Rept Re Lockout of Chemical Vol & Control Sys Centrifugal Charging Pump During ESF Actuation Sys Preoperational Testing.Initially Reported on 860110. Reset Time of Load Shed Circuit Reset Timer Adjusted

ML20212R369
Person / Time
Site:	Vogtle
Issue date:	01/14/1987
From:	Rice P GEORGIA POWER CO.
To:	Grace N NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
References
REF-PT21-87-004-000 GN-1331, PT21-87-004-000, PT21-87-4, NUDOCS 8702020616
Download: ML20212R369 (3)

Text

Georg.a Power Car;w/

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Ic'rs"ce Box 2B2oN N b , =ay 3414 404 73 en ===

P. D. Rce Cieorgia Power c,w w.

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January 14, 1987 t, C

United States Nuclear Regulatory Commission Region II, Suite 2900 File: X7BG03-1136 101 Marietta Street, Northwest Log: GN-1331r*o Atlanta, Georgia 30323

Reference:

Vogtle Electric Generating Plant-Units 1&2;50-424,50k5; ESFAS Load Sequencer Board; GN-1315 dated January 10, 1987 Attention: Mr. J. Nelson Grace In previous correspondence (GN-1315), Georgia Power Company identified a reportable condition pursuant to the requirements of 10CFR50.55(e) and 10CFR21 involving a lockout of the Chemical Volume and Control System centrifugal charging pump during engineered safety features actuation system (ESFAS) preoperational testing. The condition resulted from an overlap of the load shed and first sequencer step signals in the ESFAS logic and was corrected by adjusting the timing set points for these signals.

Subsequent to the issuance of GN-1315, Georgia Power Company learned that other loads actuated in the first sequencer step of the ESFAS logic were not addressed in the evaluation summary attached to GN-1315.

Therefore, Georgia Power Company wishes to submit the attached revised evaluation summary to provide this additional information.

This response contains no proprietary information and may be placed in the USNRC Public Document Room.

Yours truly, w4 P. D. Rice REF/PDR/wkl Attachment xc: U. S. Nuclear Regulatory Commission Document Control Desk Washington, D. C. 20555 H. G. Baker

~

D. R. Altman L. T. Gucwa J. P. O'Reilly J. A. Bailey C. W. Hayes G. F. Head G. Bockhold, Jr. G. A. McCarley R. E. Conway J. F. D'Amico R. W. McManus R. H. Pinson W. D. Drinkard Sr. Resident (NRC)

B. M. Guthrie C. C. Garrett (OPC) J. E. Joiner (TSLA)

R. A. Thomas D. Feig (GANE) NORMS 8702020616 870114 Sp PDR ADOCK 05000424 S PDR q

EVALUATION OF A POTENTIALLY REPORTABLE CONDITION ESFAS LOAD SEQUENCER BOARD Initial Report: On January 7, 1987, Mr. C. W. Ha'yes, Vogtle Quality Assurance Manager, notified Mr. M. V. Sinkule of the USNRC Region II of a potentially reportable condition associated with the centrifugal charging pump feeder breaker lockout during a safety injection (SI) condition with subsequent loss of offsite power (LOP). This condition was initially discovered during engineered safety features actuation system -

(ESFAS) preoperational testing and documented in Operations Deficiency Report ODR T-1-86-4271.

Background Information: The safety features sequencer board (SFSB) is an electronic logic system with two primary functions:

A. It monitors the voltage on the 4 KV engineered safety features (ESF) bus and sheds selected loads on that bus in the event that bus voltage is lost or degraded.

B. It initiates starting of the emergency diesel generator (EDG),

and implements the preprogrammed loading of ESF loads on the ESF buses.

The SFSB is designed to be operable when either or both LOP and/or SI occur. The SFSB is designed to provide maintained and momentary step sequence actuation to allow circuit breakers to close in accordance with preprogrammed sequencer steps.

The SFSB has nine (9) load sequence steps at 5-second intervals. The first step is set at 0.5 second after the EDG supply breaker is closed.

This step consisted of load groups 1A (centrifugal charging pump) and 2C (three (3) 480V load centers).

During the test simulating an SI condition with subsequent loss of offsite power, the centrifugal charging pump feeder breaker and two (2) load center breakers failed to reclose during sequencing, as required, after being shed from the bus.

The circuit breakers used on VEGP for this application are equipped with an anti-pump feature which locks the breakers in the open position if close and trip signals are present at the same time. In the condition identified, two signals, i.e., load shed to open the breaker and the first sequencer step to close the breaker, were simultaneously present at the first step load breakers. This caused the breakers' anti-pump feature to operate and lock out the breakers, preventing it from closing.

A broadness review and testing confirmed that the condition existed only in the circuit breakers for the first load sequence step. This condition does not occur with subsequent load sequence steps because the load shed signal to open the breakers resets prior to initiation of the close signals. Subsequent to implementation of corrective actions below, a third load group, 2A, was connected to the first sequencer step.

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Engineering Evaluation: This deficiency, had it remained uncorrected, coupled with the loss of offsite power could have resulted in the loss of first step sequencer loads (load groups 1A and 2C) on both electrical trains. Coincident loss of both electrical trains A and B load groups 1A would have resulted in loss of charging pump capability, until such time that the charging pump circuit breaker could be closed manually.

This condition represents a safeguard system availability less than the minimum assumed in the safety analyses. Consequently, this condition is considered reportable. Load group 2C breakers of both electrical trains A and B could have failed to reclose resulting in loss of additional functions. These were not evaluated further for l reportability, but were assumed to fail and the corrective action was implemented on all first step sequencer load groups.

Quality Assurance Program Breakdown Evaluation: The root cause of this deficiency was an engineering oversight. Engineering did not recognize that the first step sequence would create simultaneous trip and close signals to the circuit breakers. This condition was determined to exist only for the first load sequence step. A quality assurance program review has concluded that this condition is an isolated case and does not constitute a significant breakdown in Bechtel's quality assurance programs.

Conclusion:

Based on the results of the evaluation above, Georgia Power Company has concluded that this condition is reportable parsuant to

the requirements of 10CFR50.55(e) and 10CFR21. Based on USNRC guidance in NUREG-0302, Revision 1, and other USNRC correspondence concerning

duplicate reporting, Georgia Power Company is reporting this condition

pursuant to the requirements of 10CFR50.55(e).

1

! Corrective Action: This condition was resolved by the adjustment of the reset time of the load shed circuit reset timer from 1.0 second to 0.5 second. This assures that the load shed contact will open before the load sequencing starts. The implementation of this design modification in Units 1 and 2 was completed on December 1,1986, through Field Change Request E-FCRB-1507N.

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