ML17229A173

LER 96-005-00:on 961206,determined That Independent Operability of Trip Coils Had Not Been Adequately Tested. Caused by Inadequate Surveillance Procedure.Performed Testing of Coils & Revised procedures.W/961220 Ltr

ML17229A173
Person / Time
Site:	Saint Lucie
Issue date:	12/20/1996
From:	Benken E, Stall J FLORIDA POWER & LIGHT CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
L-96-337, LER-96-005-02, LER-96-5-2, NUDOCS 9612260012
Download: ML17229A173 (9)

Text

~ CATEGORY 1 REGULATORY INFORMATION DISTRIBUTION SYSTEM (RIDS)

ACCESSXON NBR:9612260012 DOC.DATE: 96/12/20 NOTARIZED: NO DOCKET FACIL:50-389 St. Lucie Plant, Unit 2, Florida Power & Light Co. 05000389 AUTH. NAME AUTHOR AFFILIATION BENKEN,E.J. Florida Power & Light Co.

STALL,J.A, Florida Power & Light Co.

RECIP.NAME RECIPIENT AFFILIATION

SUBJECT:

LER 96-005-00:on 961206,determined that independent operability of trip coils had not been adequately tested.

Caused by inadequate surveillance procedure. Performed testing of coils & revised procedures.W/961220 ltr.

DZSTRZBUTZON CODE: ZE22T COFZES RECEZVED:LTR 2 ENCL / SZZE:

TXTXE: 50.73/50.9 Licensee Event Report (XER), Incident Rpt, etc.

NOTES:

RECIPIENT COPIES RECIPIENT COPIES ID CODE/NAME LTTR ENCL ID CODE/NAME LTTR ENCL PD2-3 PD 1 1 WIENS,L. 1 1 INTERNAL: ACRS 1 1 B 2 2 AEOD/SPD/RRAB 2 2 FILE CEN 1 1 NRR/DE/ECGB 1 1 ELB 1 1 NRR/DE/EMEB 1 1 NRR/DRCH/HHFB 1 1 NRR/DRCH/HICB 1 1 NRR/DRCH/HOLB 1 1 NRR/DRCH/HQMB 1 1 NRR/DRPM/PECB 1 1 NRR/DSSA/SPLB 1 1 NRR/DSSA/SRXB 1 ' 1 RES/DET/EIB 1 1 RGN2 FXLE 01 1 D EXTERNAL: L ST LOBBY WARD 1 1 LXTCO BRYCE,J H 1 1 NOAC MURPHY,G.A 1 1 NOAC POORE,W. 1 1 NRC PDR 1 1 NUDOCS FULL TXT 1 1 E

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Florida Power & Light Company, P.O. Box 128, Fort Pierce, FL 34954.0128 December 20, 1996 L-96-337 10 CFR 50.73 U. S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, D. C. 20555 Re: St. Lucie Unit 2 Docket No. 50-389 Reportable Event: 96-005 Date of Event: December 6, 1996 Operation Prohibited by Technical Specifications

'breakers The attached Licensee Event Report is being submitted pursuant to the requirements of 10 CFR 50.73 to provide notification of the subject event.

Very truly yours, J. A. Stall Vice President St. Lucie Plant JAS/EJB Attachment cc; Regional Administrator, USNRC Region II Senior Resident Inspector, USNRC, St. Lucie Plant 96i22600i2 96i220 PDR ADQCK 05000389 8 PDR an FPL Group company M(

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NRC FORM 388 U.S. NUCLEAR REGULATORY COMMISSION APPROVED SY OMS NO. 31 60<104 sxFSIEs 04isorse (4.96)

ESTIMATED BURDEN PER RESPONSE To COMPLY WITH THIS MANDATO INFORMATION COLLECTION REQUESTI 60.0 HRS. REPORTED LESSON LEARNED ARE INCORPORATED INTO THE UCENSINO PROCESS AND F BACK TO NOUSTRY. FORWARD COMMENTS REGARDING BURDEN ESTIMAT LICENSEE EVENT REPORT (LER) TO THE INFORMATION ANO RECORDS MANAGEMENT BRANCH me F33I UW NUCLEAR REGIAATORY COMMISSION. WASHINGTON. OC 20666~1 AND TO THE PAPERWORK REDUCTION PROJECT (31600104), OFHCE 0 (See reverse for required number of MANAGEMENTAND BUDGET, WASHINGTON, OC 20603.

digits/characters for each block)

FACILITYNAME Ill DOCKET NISASBl (21 PAGE nl ST LUCIE UNIT 2 05000389 1 OF7 TITLE 14l Operation Prohibited by Technical Specifications due to Inadequate Surveillance Testing of Reactor Trip Breakers FACIUTY NAME DOCKET NUMSER SEQUENTIAL REVISION MONTH DAY OAY NUMBER NUMBER N/A FACIUlYNAM6 DOCKET NUMBER 12 06 96 96 005 00 12 20 96 N/A OPERATIN0 MODE (9) 20.2201 (b) 20. 2203 (0) {2)(v) 50.73{a) {2){i) 50.73(a)(2) {viii)

POWER LEVEL (10) 20.2203(a) (2) (i) 20.2203(a) (3) (ii) 60.73(a)(2)(ai) 73.71

<MC4':; <;:x"'.> OTHER

20. 2203 (a) {2){iii) 50.38(c)(1) 50.73(a) {2)(v) Specify in Abstract below or In NRC Form 3BBA 3 20.2203 (0) (2) (iv) 50.3 8(c) (2) 50.73(a)(2)(vii)

NAME TELEPHONE NUMBER Onc4aa hraa coda)

Edwin J. Benken, Licensing Engineer (561) 467 - 7156 REPORTABLE REPORTABLE cAUBE SYSTEM COMPONENT MANUFACTURER CAUSE SYSTEM COMPONENT To NPROS To NPRDS MONTH OAY YEAR EXPECTED YEB SUBMISSION

{Ifyee, complete EXPECTED SUBMISSION DATE). X No DATE (16)

ABSTRACT (umit to 1400 spaces, i.eapproximately 15 single. spaced typewritten lines) (18)

On December 6, 1996, St. Lucie Unit 2 was operating in Mode 1 at 100 percent reactor power. While performing a review as requested by NRC Generic Letter 96-01, "Testing of Safety Related Logic Circuits," FPL determined that the independent operability of trip coils associated with the Reactor Protective System (RPS) Trip Circuit Breakers (TCB) had not been adequately tested by surveillance procedure. The appropriate Technical Specification Action requirements were implemented for failure to perform a surveillance requirement. Additional testing was initiated and subsequently completed satisfactorily per Technical Specification requirements.

The cause of the event was an inadequate surveillance procedure for testing the operation of the reactor trip circuit breakers.

Corrective actions include: 1) Operability testing of the trip coils was performed to include additional testing of electrical contacts in the TCB circuit paths. 2) The surveillance procedure governing the testing of the Reactor Protective System logic was changed to include testing the required circuitry contacts. 3) Additional safety related electrical circuitry is continuing to be reviewed with regard to testing adequacy in accordance with the actions requested in NRC Generic Letter 96-01.

NRC FORM 366A U.S. NUCLEAR REGULATORY COMMISSI I4-9SI LICENSEE EVENT REPORT (LER)

TEXT CONTINUATION YEAR SEQUENTIAL REVISION ST. LUCIE UNIT 2 05000389 2 OF 7 96 005 00 TEXT ilfmore spece is required, use edditionel copies of fVRC f'orm 366Ai I17I On December 6, 1996, with St. Lucie Unit 2 operating in Mode 1 at 100 percent power, FPL engineering personnel determined that the independent operability of the undervoltage and shunt trip electrical logic paths for the Reactor Trip Circuit Breakers (TCBs) (EIIS:JC) may not have been adequately tested by current St. Lucie Unit 2 procedures. This determination was made following a review of a similar condition found at Palo Verde Station and an assessment of NRC Generic Letter, 96-01, "Testing of Safety Related Logic Circuits" for applicability to St. Lucie Plant. St. Lucie Unit 2 Technical Specification (TS) 4.3.1.1, requires that a functional test be performed at least once per 18 months or following maintenance or adjustment of the reactor trip circuit breakers to verify the independent operability of the undervoltage and shunt trips. At 1705 on December 6, 1996, based upon the above determination, Operations invoked Technical S, cification 4.0.3. for failure to perform a surveillance requirement within the allowed surveillance interval. A Condition Report (CR) was initiated to assess the validity of the testing requirements and review the operability of the TCBs.

TS 4.0.3 specifies that failure to perform a surveillance requirement within the allowed surveillance interval shall constitute noncompliance with the operability requirements for a Limiting Condition for Operation (LCO) TS 4.0.3 allows that action requirements may be delayed for up to 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> to

~

permit the completion of a surveillance when the allowable outage time limits of the LCO action requirements are less than 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />.

Following discovery of the above condition, functional testing was initiated at 2145, on December 6, 1996, to verify the independent operability of the undervoltage and shunt trips for the reactor TCBs.

This testing was completed satisfactorily at 2215 on December 6, 1996, and TS 4.0.3 was then exited.

The cause of the event was an inadequate surveillance test procedure. Operating Procedure 2-1400059, "Reactor Protection System - Periodic Logic Matrix Test," contains the instructions for performance of the operability test for the Reactor Trip Circuit Breakers shunt trip and undervoltage trip devices (coils). The surveillance test instructions of the procedure verified the satisfactory operation of both of the above shunt and undervoltage trip devices, and were consistent with vendor recommendations, however, the test did not verify the independent operation of the electrical contacts which operate the shunt and undervoltage trip coils. At the time of the event, the surveillance adequacy of the reactor trip circuit breakers had been identified for additional engineering review in accordance with the schedule referenced in the FPL response to Generic Letter 96-01, dated April 18, 1996.

This event is reportable under 10 CFR 50.73 (a)(2)(i)(B) as "any operation or condition prohibited by the plant's Technical Specifications." St. Lucie Unit 2 TS 4.3.1.1 requires that each reactor protective instrumentation channel be demonstrated operable by the performance of the channel check, channel calibration and channel functional test operations for the Modes and frequencies shown in table 4.3-".

NRC FORM 388A I4 9SI

NRC FORM 368A U.S. NUCLEAR REGULATORY COMMISSI I4-96I LICENSEE EVENT REPORT (LER)

TEXT CONTINUATION YEAR SEQUENTIAL REVISION ST. LUCIE UNIT 2 05000389 3 OF 7 96 005 00 TEXT /ifmore specs is required, use edditionel copies of NRC cform 366A/ I17I TS table 4.3.1 requires that at least once per 18 months and following maintenance and adjustment of the reactor trip breakers, the channel functional test shall include verification of the independent operability of the undervoltage and shunt trips. Following a,determination that the independent operability of the above undervoltage and shunt trip devices had not been adequately tested at St.

Lucia Unit 2, Operations personnel implemented the surveillance requirements of TS 4.0.3. As previously discussed, TS 4.0.3 specifies that failure to perform a surveillance requirement within the allowed surveillance interval constitutes noncompliance with the operability requirements fo'r an LCO and permits action requirements to be delayed for up to 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> to facilitate completion of the surveillance. FPL satisfactorily performed the additional, required testing of the electrical logic paths a<<ociated with the reactor trip circuit breakers within the allowable time constraints of TS 4.0.3.

The reactor trip circuit breakers are a functional unit of the Reactor Protective System (RPS) instrumentation at St. Lucie Plant. The operability of the RPS instrumentation and bypasses ensures that 1) the associated reactor trip will be initiated when a monitored parameter reaches its set point, 2) the specified coincidence logic is maintained, 3) sufficient redundancy is maintained to permit a channel to be out of service for testing or maintenance, and 4) sufficient system functional capability is available from diverse parameters.

The RPS is designed so that any single failure within the system will not prevent proper protective action at the system level when required. There are four Reactor Trip Channels associated with the RPS. A two-out-of-four RPS logic trip signal results in the deenergization of four trip path relays, which in turn results in the deenergization of undervoltage coils and energization of shunt trip coils on eight reactor TCBs (Refer to Figure 1). Either of the two trip coils associated with a reactor TCB is capable of tripping the breaker from an RPS actuation. Both of the trip paths are actuated by the same RPS relay and use different sets of relay contacts to actuate their associated trip coils (Refer to Figure 2). One or

>> both of these contacts changing state will result in the opening of the TCB. The following tests are performed at St. Lucie to verify the operability of the reactor TCBs:

The Trip Coil of each reactor TCB is tested by use of a test push-button which energizes the shunt trip coil and opens the breaker. This test is conducted at least every 18 months and following maintenance or adjustment of the TCB.

2. The Undervoltage (UV) Coil of each reactor TCB is tested by removing the power supply fuse which deenergizes the UV coil and opens the breaker. This test is also conducted every 18 months and following maintenance or adjustment of the TCB.

3. The RPS Periodic Logic Matrix Test is performed each month to verify that RPS trip path relays function correctly and the TCBs open when required.

NRC FORM 368A I4-96I

NRC FORM 368A U.S. NUCLEAR REGUlATORY COMINISSIO I4-9SI LICENSEE EVENT REPORT (LER)

TEXT CONTINUATION YEAR SEQUENTIAL REVISION ST. LUCIE UNIT 2 05000389 4 OF 7 96 005 00 TEXT (If more specs is required, use edditionel copies of NRC &rm 368AJ I17)

As described by the above tests, the ability of the reactor trip breakers to open on an RPS actuation signal is demonstrated by the RPS Logic Matrix Test, which is performed monthly. Additionally, the operability of the TCB trip coils and undervoltage coils is demonstrated at least every 18 months.

Performance of the above testing, however, does not specifically verify that the contacts in the electrical logic paths change state to actuate the undervoltage or shunt trip coils. Individual contacts that perform a safety function are required to be tested in accordance with the guidance provided by Generic Letter 96-01.

Subsequent to this event, FPL Engineering performed a review of the testing requirements associated with the reactor TCBs. This review determined that while the potential for an undetected failure of one contact in the electrical flowpath to an RPS TCB exists during performance of the RPS Logic Matrix Test, this will not result in the failure of the TCB to trip. The dual path, electrical arrangement associated with each reactor TCB is not designed as a redundant feature, as there is no separation or isolation, and common equipment is used in both paths. The two paths are diverse, however, in that different mechanisms (energization vs. deenergization and the use of different trip coils) are provided fo increased reliability of the trip mechanism.

A review of TCB surveillance tests performed at St. Lucie Unit 1 determined that at Unit 1, the RPS Logic Matrix Test Procedure, performed monthly, includes a verification of indicating lights (unique to Unit 1) provided in both the shunt and undervoltage trip paths. These indicating lights are not available at St. Lucie Unit 2. Additionally, St. Lucie Unit 1 Technical Specifications do not require a functional check be performed of the independent operability of the shunt and undervoltage trip paths. Therefore, this condition is not applicable to St. Lucie Unit 1.

Additional surveillance testing performed as a result of this event satisfactorily demonstrated that the electrical logic contacts responsible for actuating the undervoltage and shunt trip coils on the reactor TCBs were operational. No reactor trip paths were disabled as a result of the subject testing inadequacy, and sufficient system diversity and functional capability was maintained. Based upon the above, the protection of the'health and safety of the public was not adversely affected by the event.

Testing of the electrical logic contacts for the reactor trip circuit breakers was satisfactorily performed on December 6, 1996.

2. The St. Lucie Unit 2 Reactor Protection System - Periodic Logic Matrix Test Procedure (2-1400059) was revised to include additional verification of Trip Relay Contact operation during the 18 month surveillance performance.

NRC FORM 388A I4.96I

NRC FORM 366A U.S. NUCLEAR REGULATORY COMMISSIO 4.95I LICENSEE EVENT REPORT (LER)

TEXT CONTINUATION YEAR SEQUENTIAL REVISION ST. LUCIE UNIT 2 05000389 5 OF 7 96 005 00 TEXT (Ifmore space is required, use additional copies of NRC Form 368AJ I17I

3. In accordance with Generic Letter 96-01, FPL is continuing to review applicable safety relate logic circuitry and testing procedures to ensure that all circuit components required to be tested are adequately addressed by surveillance procedures.

None None NRC FORM 386A H-9S)

NRC FORM 388A U.S. NUCLEAR REGULATORY COMMISSI 14-96)

LICENSEE EVENT REPORT (LER)

TEXT CONTINUATION YEAR SEQUENTIAL REVISION ST. LUCIE UNIT 2 05000389 6 OF 7 96 005 00 TEXT fifmore space is reqvired, use additional copies of lIl'RC Form 866Al I17I REACTOR PROTECTIYE SYSTEM SIMPLIFIED LOGIC DIAGRAM I238$ 789109 1238$ 8789109 I234$ 8789109 I 2 3 8 $ 8 7 8 9109 INPUTS FROM IBSS MEAsUREMENT aIANNELS CHANNEL A CHANNEL 8 CHANNEL C CHANNEL D TRIP UNITS LCGIc A.B LOGIC AN LOGIC A 0 LOGIC 8-C LOGIC B.D LOGIC C.D LOGIC MATRICES I A87 ASl A8l I ACI ACI i AO2 881 8Ct 8CI 8Ci Kl1 187I 1871 SD4 CO > 807 807 COI LOGIC MATIYK RELAYS MA 120 VAC MB 120 YAC MC 120 VAC MD 120 VAC INSTRUMENT BVS INSTRUMENT BVS INSTRUMENT BUS INSTRUMENT BUS 4'AC 'I A80 VAC AB1 AB2 BVS BVS 2 A83 A84 MAIN AC1 AC2 AC3

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CIRCVIT BREAKERS AC4 AD1 AD2 A03 A04 TRIP MOTOR BC3 PA1113 BCI BC2 GENERATORS BC4 801 BD2 803 BD4 C01 C02 240 VAC C03 C04 TRIP CIRCIAT BREAKER KA CONTROL RELAYS ((

12$ YDC l(US B 12$ YDC I(US A I

MANUAL TT8PI 4 ~

I 12$ /USA ST UV ST KI KI UY 12$ YDC BVS B I +

MANUAL 778P 2 7 KA I TTYP aRCUIT BREAKERS ST ST

~ a am wanga ITY 9 DENOTES ADDITeNALREACTOR PIRCOD111807.

TRIP UNIT ON DIAT2 CCW LOSS OF FLOW 81DMDUALCEDM CEDM UeIYIDVALCEDM GEOM POWER SUPPLIES CONTROL SYSTEM POWER SUPPUES POWER SUPPUES CEDM CEDM CEDM CEDM CEDM CEDM CONTROL ELEMENT COILS COILS GOES CaLS Cals Gals DRIVE MECHANISMS NRC FORM 388A 14.96)

NRC FORM 388A U.S. NUCLEAR REGULATORY COMMISSI LICENSEE EVENT REPORT (LER)

TEXT CONTINUATION YEAR SEQUENTIAL REVISION 05000389 '7 OF 7 ST. LUCIE UNIT 2 005 96 00 TEXT (ifmore spece is reqirired, Irse eddidoneicopies of NRC Farm 3M4l I 1 7)

REACTOR TRIP CIRCUIT BREAKER SIMPLIFIED WIRING DIAGRAIYI (TYPICAL)

TEST PUSH BUTTON BKS NORMALLY NORMALLY 12m) I?

CLOSED OPEN EMERG INOT TESTEO INOT TESTEO TRIP IIIOEPENOENTLY) INOEPENOENTI.Y) PUSH BUTTON EE DPS R CLOSES MANUAL ON TRIP TEST PUSH BUTTON (RTGB)

UNDER VOLTAGE SHUNT UVD COIL TRIP COIL REEHEBRZS BKBQlZEB H?SPENT KB TC