ML20207K769

Interim Deficiency & Part 21 Rept Re Diesel Generator Breaker Trip Circuit.Initially Reported on 860523.Field Change Request EFCRB-14691 Issued to Modify Breaker Trip Circuit

ML20207K769
Person / Time
Site:	Vogtle
Issue date:	06/26/1986
From:	Foster D GEORGIA POWER CO.
To:	Grace J NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
References
REF-PT21-86, REF-PT21-86-338-000 GN-956, PT21-86-338, PT21-86-338-000, NUDOCS 8607300027
Download: ML20207K769 (3)

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8 Georgia Fbwer Company Fbst Otsce Box 282 Waynesbora Georgia 30830 Telephone 404 554 9961. Ext. 3360 404 724 8114. Ext. 3360 Y3 L D. O. Foster Georgia Power .

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United States Nuclear Regulatory Commission Region II File: X78G03-M114 Suite 2900 Log: GN-956 101 Marietta Street, Northwest Atlanta, Georgia 30323

Reference:

Vogtle Eler' e Generating Plant-Units 1 and 2; 50-424, 50-425; Diesel Gent.rator Breaker Trip Circuit; Letter GN-917 dated May 23, 1986 attention: Mr. J. Nelson Grace In previous correspondence on the above referenced subject, Georgia Power Company indicated the NRC would be informed of the results of

' the evaluation of this condition by June 27, 1986. Georgia Power Company has completed its evaluation and detennined that a reportable condition as defined by the reporting criteria of Parts 10 CFR 50.55(e) and Part 10 CFR 21 does exist. Based upon guidance in NUREG-0302 Revision 1 and other NRC correspondence, Georgia Power Company is reporting this condition per the reporting criteria of Part 10 CFR 50.55(e). A summary of our evaluation is enclosed.

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

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i Enclosure xc: U. S. Nuclear Regulatory Commission Document Control Desk i

Washington, D. C. 20555 J. H. Miller R. A. Thomas L. T. Gucwa J. P. O'Reilly D. R. Altman C. W. Hayes

) P. R. Bemis G. A. McCarley l G. F. Head i R. E. Conway J. A. Bailey D. S. Read J. T. Beckham 0. Batum Sr. Resident (NRC)

R. H. Pinson G. Bockhold C. S. McCall (OPC)

P. D. Rice C. E. Belflower J. E. Joiner (TSLA)

B. M. Guthrie J. F. D'Amico D. C. Teper (GANE)

D. E. Dutton E. D. Groover NORMS 8607300027 860626 PDR ADOCK 05000424

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EVALUATION OF A POTENTIALLY REPORTABLE CONDITION DIESEL GEhERATOR BREAKER TRIP CIRCUIT Initial Report: On April 25, 1986, Mr. R. E. Folker, Vogtle Project Quality Assurance Engineer, informed Mr. E. F. Christnot of the USNRC-Region II of a potentially reportable condition concerning the diesel generator breaker trip circuit. In letter GN-917 dated May 23, 1986, Georgia Power Company indicated that the NRC could expect to be informed of the results of the evaluation of this condition by June 27, 1986.

Background Information: A review of the circuit breaker trip circuit indicated a design condition existed that could prevent power from the diesel generator from reaching the emergency buses. This condition was reported on Operational Deficiency Report T-1-85-1810. Bechtel Power Corporation designed the diesel generator trip circuit.

The Class IE diesel generatar is the emergency onsite AC power source and provides power to Class 1E equipment in the event of loss of the preferred power sources (offsite power). Protective devices are provided to protect the diesel generator when abnormal operating conditions occur. To ensure that the diesel generators will be available to continuously provide standby power when needed, as required by Regulatory Guide 1.9, not all protective devices are allcwed to trip the diesel generator when abnormal operating conditions occur. During a loss-of-coolant accident (LOCA) concurrent with loss-of-offsite power, (LOSP) all the diesel generator protective trip devices are bypassed except for the following trips:

Engine overspeed Generator differential Low lube oil pressure High jacket water temperature The bypassing of all other diesel generator protective trips is accomplished I through a safety injection actuation signal (SIAS) permissive relay contact from relay K609, which is connected in series with two parallel connected relay contacts from lockout relays 186C-DGIA and 1868-DG1A, (please refer to attachment 1).

Each of the lock-out relays referred to above are actuated by protective devices which need to protect the diesel generators for other than a SIAS condition. Once actuated the lock-out relay contacts remain closed until reset for the next operation. During a SIAS, the parallel-connected lockout relay contacts are blocked by an open contact from relay K609. During normal operation or test (no SIAS signal present), the K609 contact is closed enabling the protective relay trips which actuate relays 186C-DG1A and 1868-DG1A described above.

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s Page two Engineering Evaluation: In d'e event, during a LOCA condition, the diesel generator unit experiences multiple abnormal operating conditions, multiple protective trip devices may be actuated. This could close both the parallel-connected lockout relay contacts. Under this condition, a " sneak circuit" is created which will allow the actuation of the diesel generator circuit breaker trip coil, tripping the circuit breaker open. The " sneak circuit" is the close circuit loop through contacts 1868-DG1A, 186C-DG1A, 152/a, K609 and another 152/a connected in series with the trip coil (TC).

Tripping the diesel generator circuit breaker will result in the loss of the emergency onsite AC power source to the safety related loads which will prevent the loads of one safety train from performing their safety related functions.

As required in R. G. 1.9, all protective relay trips, are bypassed except those previously discussed, during a LOCA. With the " sneak circuit", these requirements will not be met if multiple protective trips are actuated. The

" sneak circuit" will trip the diesel generator resulting in the loss of the standby source of power to the safety related circuit or load breaker. This coadition will prevent the performance of safety related functions. An assumed single failure in the opposite train coincident with a loss of offsite power, could cause the station to be without electrical power.

Review of Quality Assurance Program Breakdown: A review of the quality assurance program at Bechtel Power Corporation has concluded that there was not a significant breakdown of their quality assurance program.

Conclusion:

Georgia Power Company has concluded that this condition is reportable per the reporting criteria of Parts 10CFR21 and 10CFR50.55(e).

This condition represents a deficiency in the final design such that the design of the system does not conform to the FSAR and could have, if uncorrected, affected adversely the future operation of the Unit. Based upon guidance in NUREG-0302 Revision 1 and other NRC correspondence concerning duplicate reporting, Georgia Power Company is reporting this condition per the criteria of Part 10CFR50.55(e).

l Corrective Action: The " sneak circuit" was discovered during a review of' the diesel generator system. Field Change Request EFCRB-14691, dated l March 13, 1986, was issued to modify the breaker trip circuit. A safety l injection relay K649 contact was placed in series with a lockout relay contact as shown in EFCRB-14691.

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