ML18101A763

LER 95-007-00:on 950505,EDGs 1A,1B & 1C Simultaneously Paralleled to Electrical Grid,Resulting in Potential for Common Mode Failure of All Three Edgs.Caused by Mgt/Qa Deficiency.Procedures revised.W/950602 Ltr

ML18101A763
Person / Time
Site:	Salem
Issue date:	06/02/1995
From:	Pastva M, Summers J Public Service Enterprise Group
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
95-056, 95-56, LER-95-007, LER-95-7, NUDOCS 9506090150
Download: ML18101A763 (7)

Text

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Public Service Electric and Gas Company P.O. Box 236 Hancocks Bridge, New Jersey 08038-0236 Nuclear Business Unit June 2, 1995 U. S. Nuclear Regulatory Commission Document Control Desk Washington, DC 20555 Attn: Document Control Desk SALEM GENERATING STATION LICENSE NO. DPR-70 DOCKET NO. 50-272 UNIT 1 LICENSEE EVENT REPORT NO. 95-007-00 This Licensee Event Report is being submitted pursuant to the requirements of Code of Federal Regulation 10CFR50. 73 (a) (2) (ii) (B). Issuance of this report is required within thirty (30) days of event discovery.

SORC Mtg.95-056 MJPJ:vs C Distribution LER File 9506090150 950602 PDR ADOCK 05000272 S PDR The pmn*r is in your Sincerely, c 0 J. C. Summers General Manager -Salem Operations AeJef 'I J 95-2168 RE . 6/94 1PmC-FORM 366 . U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB NO. 3150-0104 (5-92)

• EXPIRES 5/31/95 ESTIMATED BURDEN PER RESPONSE TO COMPLY WITH THIS LICENSEE EVENT REPORT (LER) INFORMATION COUECTION REQUEST: 50.0 HRS. FORWARD COMMENTS REGARDING BURDEN ESTIMATE TO THE INFORMATION AND RECORDS MANAGEMENT BRANCH (MNBB 7714). U.S. NUCLEAR REGULATORY COMMISSION, WASHINGTON, DC 2CJ555.ooo1 AND TD (See reverse for required number of digits/characters for each block) THE PAPERWORK REDUCTION PROJECT {3150-0104)

OFFICE OF MANAGEMENT AND BUDGET, WASHINGTON, DC 205o3. ' . FACILITY NAME (1) -DOCKET NUMBER (2) II PAGE (3) Salem Generating Station -Unit 1 osooo*212 j OFf TITLE (4) Emergency Diesel Generators

!A, us' anc1 re SimultaneousJ_y' Paralleled to Grid -EVENT DATE (5) LEA NUMBER (6 REPORT NUMBER (7) OTHER FACILITIES INVOLVED (8) MONTH DAY YEAR SEQUE.,!"""""'" 1 REVISION FACILITY NAME DOCKET NUMBER YEAR MONTH DAY YEAR NUMBER NUMBER 05000 05 05 95 95 007 00 06 02 95 FACILITY NAME DOCKET NUMBER ----05000 OPERATING THIS REPORT IS SUBMITIED PURSUANT TO THE REQUIREMENTS OF 10 CFR §: (Check one or more (11) MODE (9) 1 20.402(b) 20.405(c) 50.73(a)(2)(iv) 73.7.1 (b) POWER 20.405(a)(1)0) 50.36(c)(1) 50.73(a)(2)(v) 73.71(c) LEVEL (10) 58% 20.405(a)(1)(ii) 50.36(c) (2) 50.73(a)(2)(vii)

OTHER i-20.4os(a)(1)

Oii) 50.73(a)(2)0)

50. 73(a) (2) (viii) (A) (Specify in Abstract 20.405(a)(1)(iv) x 50.73(a)(2)(ii) 50.73(a)(2)(viii)(B) below and in Te"1, NRC Farm 366A) 20.405(a)(1)(v)

50. 73 (a)(2) Oiil 50. 73 (a)(2)(x)

LICENSEE CONTACT FOR THIS LEA 12) NAME Michael J. Pastva, Jr. LER Coordinator TELEPHONE NUMBER (Include Area Cade) 609-339-5165 COMPLETE ONE LINE FOR EACH COMPONENT FAILURE DESCRIBED IN THIS REPORT {13) CAUSE SYSTEM COMPONENT MANUFACTURER REPORTABLE I CAUSE REPORTABLE SYSTEM COMPONENT MANUFACTURER TONPRDS TONPADS I I I I SUPPLEMENTAL REPORT EXPECTED (14) I EXPECTED MONTH DAY YEAR I I YES . SUBMISSION (If yes. complete EXPECTED SUBMISSION DATE) x NO DATE (15) ABSTRACT (Limit to 1400 spaces, i.e., approximately 15 single-spaced typewritten lines) (16) At 0421 hours0.00487 days <br />0.117 hours <br />6.960979e-4 weeks <br />1.601905e-4 months <br /> on 5/5/95, Unit 1 Emergency Diesel Generators (EDGs) lA, lB, and lC were simultaneously paralleled to the electrical grid. This resulted in the potential for a common mode failure of all three ( 3) EDGs and was not in compliance with Regulatory.Guide (RG) 1.108, Section c.2.b. This . occurrence is attributed to management/quality assurance deficiency, as the ' involved Operations shift was: not aware of RG

• L 108 recommendation to independently test the EDGs, not sufficiently aware of what constitutes preventive maintenance (PM) and "other than PM" and when the 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> clock starts for verifying EDG operability after "other than PM" is determined.

Contributors:

lack of Technical Specification 3.8.1.1 and procedure guidance on RG 1.108 requirements, inadequate guidance on PM and "other than PM" and when the 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> clock starts for verifying EDG operability for "other than PM". Procedure changes have been made to prohibit operation of more tr').an one EDG paralleled to the electrical grid at any one time, as per RG 1.108. All licensed Operations personnel have received guidance to understand what constitutes PM and "other than PM" I and ensure their understanding of TS 3.8.1.1. A review will be conducted to verify that RG 1.108 recommendations are adequately addressed within plant procedures.

This occurrence be reviewed during upcoming licensed operator -training.

I :.IRC FORM 366 (5-92)

• LICENSEE EVENT REPORT (LER) TEXT CONTINUATION Salem Generating Station Docket Number LER Number Page 2 of 6 Unit# 1 50-272 95-007-00 Plant and System Identification:

Westinghouse

-Pressurized Water Reactor Energy Industry Identification System (EIIS) codes appear in the text as {xx} Identification of Occurrence:

Emergency Diesel Generators lA, lB, and lC Simultaneously Paralleled To The Electrical Grid Event Date: May 5, 1995 Report Date: June 2, 1995 This report was initiated by Incident Report No.95-534 Conditions Prior to Occurrence:

Mode 1 Reactor Power 58% Unit Load 575 MWe Description of Occurrence:

At 0421 hours0.00487 days <br />0.117 hours <br />6.960979e-4 weeks <br />1.601905e-4 months <br /> on May 5, 1995, Unit 1 Emergency Diesel Generators (EDGs) lA, lB, and lC {VJ} were simultaneously paralleled to the electrical grid. This occurrence resulted in the potential for a common mode failure of all three (3) EDGs and constituted operation not in compliance with Regulatory Guide (RG) 1.108, Section C.2.b. The NRC was notified of this occurrence, at 1821 hours0.0211 days <br />0.506 hours <br />0.00301 weeks <br />6.928905e-4 months <br /> (same day), in accordance with 10CFR50. 72 (b) (2) (iii). Subsequent review of. this occurrence has determined it is applicable to 10CFR50.72(b)

(1) (ii) (B), as a condition outside the design basis of the plant, which is further described in the Safety Significance:

section of this report. Analysis of Occurrence:

At approximately 0500 hours0.00579 days <br />0.139 hours <br />8.267196e-4 weeks <br />1.9025e-4 months <br /> on May 4, 1995, lB EDG was removed from service and cleared and tagged. This was done to support routine preventive maintenance (PM), which included manual barring and replacement of the EDG exciter fuses. The expected duration of this PM was less than four (4) hours. Encountered equipment problems delayed return of

• • . . -e LICENSEE EVENT REPORT (LER) TEXT CONTINUATION Salem Generating Station Docket Number LER Number Page 3 of 6 Unit# 1 50-272 95-007-00 Analysis of Occurrence: (cont'd) the EDG to service: the EDG exciter cabinet was discovered to have missing bolts and the EDG local temperature panel fuse blew upon restoration of the EDG. These problems were resolved and, at approximately 0230 hours0.00266 days <br />0.0639 hours <br />3.80291e-4 weeks <br />8.7515e-5 months <br /> on May 5, 1995, the required repairs to lB EDG were completed.

At approximately 0300 hours0.00347 days <br />0.0833 hours <br />4.960317e-4 weeks <br />1.1415e-4 months <br /> (same day) the Operations Nuclear Shift Supervisor (NSS) determined that the repairs to resolve the encountered problems had changed the maintenance performed on lB EDG to "other than PM", i.e. "corrective maintenance" (CM). The determination of CM necessitated operability testing of the remaining EDGs. In addition, it was conservatively assumed that the CM had begun from when the EDG was originally removed from service, at 0500 hours0.00579 days <br />0.139 hours <br />8.267196e-4 weeks <br />1.9025e-4 months <br /> on May 4. With one (1) EDG inoperable, Technical Specification (TS) 3.8.1.1 requires operability testing of the remaining two (2) EDGs within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />. Based upon the determination that the maintenance was "other than PM", the Unit 1 Nuclear Shift Supervisor (NSS) assumed. that by 0500 hours0.00579 days <br />0.139 hours <br />8.267196e-4 weeks <br />1.9025e-4 months <br /> on May 5th, successful operability testing o-f lB EDG or both EDGs lA and lC was required.

However, it was reasoned that if operability testing of lB EDG proved unsuccessful, there would have been insufficient time to subsequently complete operability testing of lA and lC EDGs before 0500 hours0.00579 days <br />0.139 hours <br />8.267196e-4 weeks <br />1.9025e-4 months <br /> (same day). As such, the Operations shift assumed the most timely approach to meet the time constraints of the required testing was to perform concurrent operability testing on all three EDGs. Apparent Cause of Occurrence:

This occurrence is attributed to "Management/QA Deficiency", as classified in NUREG-1022, Appendix B. RG 1.108 is listed in Section 3A of the Updated Final Safety Analysis Report (UFSAR) and in the TS 3.8.1.1 bases. The involved Operations shift was not aware of the RG 1.108 recommendation to independently test the EDGs, attributed to lack of TS 3.8.1.1 and procedure guidance on RG 1.108. Specifically, there was no procedural restriction to prohibit paralleling more than one EDG at a time. In addition, inadequate guidance existed on what constitutes PM and "other than PM" or that the 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> timeframe for verifying EDG operability begins at the time it is determined that the maintenance is "other than PM". Based upon the aforementioned, the Operations shift interpreted that operability testing of lB EDG or both lA and lC EDGs was required by May 5th, in order to comply with TS 3.8.1.1 and RG 1.108.

LICENSEE EVENT REPORT (LER) TEXT CONTINUATION Salem Generating Station Docket Number LER Number Page 4 of 6 Unit # 1 50-272 95-007-00 Prior Similar Occurrence:

Review of documentation did not reveal a prior similar occurrence.

Safety Significance:

This occurrence is reportable pursuant to the requirements of 10CFR50.73(a)

(2) (ii) (B), as it is considered to have been outside design basis because it resulted in a condition where the EDGs potentially could not have been reliably sequenced.

Assessment of this occurrence identified two (2) credible worst case scenarios with more than one (1) EDG paralleled to the electrical grid. 1) Failure of Unit 1 13/4 KV transformer supplying two vital buses. This would cause the vital bus main breakers to trip, isolating the EDGs on their respective buses. Subsequent Loss of Offsite Power (LOOP). The vital bus powered by the unaffected 13/4 KV transformer would then be tripped via undervoltage or overcurrent protection as described in 2) below. The worst case is if the overcurrent protection actuates and locks out the affected vital bus. Buses powered from the failed SPT would not recognize the loss of power, as they would be isolated from it and not permitted to transfer to the alternate source because the bus voltage was supported by the EDGs. Loads running on the affected vital buses will continue to operate and are not expected to be degraded (electrically or mechanically) due to the EDGs running in the droop mode at a frequency between 60 and 61.8 Hz. As a result of the LOOP, the reactor would be tripped and require shutdown loads. Shutdown loads on the 2 affected vital buses would require manual sequencing.

Automatic sequencing in response to a LOOP is required by UFSAR Section 8.3. Note that if an accident signal is generated during this scenario, load sequencing will occur, per design requirements.

This scenario is less limiting than scenario 2. 2) Total loss of offsi te power resul tlng in no 4 .16KV or 13.8KV circuit breaker trips. This would result in

---LICENSEE EVENT REPORT (LER) TEXT CONTINUATION Salem Generating Station Docket Number LER Number Page 5 of 6 Unit# 1 50-272 95-007-00 Safety Significance: (cont'd) the EDGs supporting the total load, both vital and nonvital buses, for both Units 1 and 2. This overload condition of the EDGs would result in high current output from the EDGs as well as rapid system voltage collapse and frequency degradation.

Engineering review indicates that a relay race would occur between the bus undervoltage relays (70%) and the vital bus main feeder breakers overcurrent relays. If the bus undervoltage relays respond first, the Safeguards Equipment Cabinets (SECs) would trip the EDG breakers and sequence the appropriate loads. If the overcurrent relays on the main breakers respond first, all breakers on the buses would be tripped. The EDG breakers would then be reclosed and the vital bus repowered via the SEC. The SEC will attempt to reload as all load breakers will sequence and immediately trip and lock out. Manual resetting of overload multi-trips and manual sequencing of all loads would then be required to restore vital bus loads. This scenario alone is equivalent to a Station Blackout scenario, for which plant response and recovery actions have been analyzed for Salem. However, if a design basis accident occurred between the time that the bus overload trip occurred and was reset, no automatic sequencing would have occurred.

This could have prevented fulfillment of the SEC and EDGs' safety function as described in UFSAR Section 8.3 and Technical Specifications 3/4.3.2 and 3/4.8.1. Corrective Action: Procedure changes have been made to prohibit operation of more than one EDG paralleled to the electrical grid at any one time, consistent with Regulatory Guide 1.108. All licensed Operations personnel have received guidance to understand what constitutes PM and "other than PM", in order to better determine when demonstration of EDG operability is required.

Licensed Operations personnel have received guidance to ensure their understanding of TS 3.8.1.1 regarding action statement requirements for EDG testing if one or more EDGs are inoperable.

This included direction on timely initiation of EDG testing. A review will be conducted to verify that RG 1.108 LICENSEE EVENT REPORT (LER) TEXT CONTINUATION Salem Generating Station Docket Number LER Number Page 6 of 6 Unit# 1 50-272 95-007-00 Corrective Action: (cont'd) recommendations are adequately addressed within plant procedures.

This occurrence will be reviewed during upcoming licensed operator training.

MJPJ:vs REF: SORC Mtg.95-056 J. C. Summers General Manager -Salem Operations