ML17229A375

LER 97-006-00:on 970501,operation Was Prohibited by TS Due to Inadequately Tested Degraded Voltage Sys.Revised Unit 1 ESFAS Surveillance Test procedure.W/970602 Ltr

ML17229A375
Person / Time
Site:	Saint Lucie
Issue date:	06/02/1997
From:	Frehafer K, Stall J FLORIDA POWER & LIGHT CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
L-97-145, LER-97-006, LER-97-6, NUDOCS 9706100099
Download: ML17229A375 (13)

Text

CATEGORY j.

REGULATO INFORMATION DISTRIBUTION TEM (RIDS)

AGCESSION NBR:9706100099 DOC.DATE:. 97/06/02 NOTARIZED: NO DOCKET FACIL:50-335 St. Lucie Plant, Unit 1, Florida Power a Light Co. 05000335 AUTH:NAME'UTHOR AFFILIATION FREHAFER,K.W. Florida Power 6 Light Co.

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

RECIP.NAME RECIPIENT AFFILIATION

SUBJECT:

LER 97-006-00:on 970501,operation was prohibited by TS due to inadequately tested degraded'oltage sys.Revised Unit 1 ESFAS surveillance test procedure.W/970607 ltr. .

DISTRIBUTION CODE: IE22T COPIES RECEIVED:LTR ! ENCL .( SIZE:

TITLE: 50.73/50.9 Licensee Event Report (LER), Incident Rpt, etc.

NOTES:

RECIPIENT COPIES RECIPIENT COPIES ID CODE/NAME'D2-3 LTTR ENCL ID CODE/NAME LTTR ENCL PD 1 1. WIENS,L. 1 1 INTERNAL: ACRS 1 AEGD/PSQQ/RAB 2 2 AEOD/SPD/RRAB I FILE CENTERRI 1 1 NRR/DE/ECGB 1 NRR/DE/EELB 1 1 NRR/DE/EMEB 1 NRR/DRCH/HHFB 1 1 NRR/DRCH/HICB 1 NRR/DRCH/HOLB 1 1 NRR/DRCH/HQMB 1 NRR/DRPM/PECB 1 1 NRR/DSSA/SPLB 1 NRR/DSSA/SRXB 1 1 RES/DET/EIB 1 RGN2 FILE 01 1 '1 EXTERNAL: L ST LOBBY WARD 1 1 LITCO BRYCE,J H 1 1 NOAC POOREFW. 1 1 NOAC QUEENER,DS 1 1 NRC PDR 1 1 NUDOCS FULL TXT 1 1 NOTE TO ALL "RIDS" RECIPIENTS:

PLEASE HELP US TO REDUCE WASTE! CONTACT THE DOCUMENT CONTROL DESK, ROOM OWFN 5D-5(EXT. 415-2083) TO ELIMINATE YOUR NAME FROM DISTRIBUTION LISTS FOR DOCUMENTS YOU DON'T NEED!

FULL TEXT CONVERSION REQUIRED TOTAL NUMBER OF COPIES REQUIRED: LTTR 25 ENCL 25

Florida Power & Light Company, 6501 South Ocean Drive, Jensen Beach, FL 34957 June 2, 1997 APL L-97-145%

10 CFR 50.73 U. S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, D. C. 20555 Re: St. Lucie Units 1 and 2 Docket No. 50-335 Reportable Event: 97-006 Date of Event: May 1, 1997 Operation Prohibited by Technical Specifications 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/KWF Attachment cc: Regional Administrator, USNRC Region II P igeyjqqgesident Inspector, USNRC, St. Lucie Plant 9706100099 970602

'PDR ADOCK 05000335 l S PDR II!IIII!fllllllllllllllllllflllllffllffl an FPL Group company

NRC FORM 466 u. CLEAR REGULATORY COMMISSION APPROVED SY OINI No. S 1604104 (4.06) EXPSIES 04130ISS ESllMATEO BURDEN PER RESPONSE TO COMPLY WITH THIS MANOATO INFORMATION COLLECTION REQUEST: 60.0 HRS. REPORTED LESSON LEARNED ARE INCORPORATED INTO THE UCENSINO PROCESS ANO F LXCENSEE EVENT REPORT (LER) SACK TO seOUSTIIY. FORWARD COMMENTS REOAROINO BURDEN ESllMAT TO THE INFORMATION AND RECORDS MANAGEMENT BRANCH IT% F331

'I UB. NUCLEAR REGIAATORY COMMISSION, WASHINGTON, DC 206664001 AND TO THE PAPERWORK REDUCTION PROJECT (316041041, OFRCE 0 (See reverse for required number of

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MANAOEMENTANO SUDOET, WASHINOTON, DC 20603.

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FACIUTYNAME ul DOCKET NIEVSER 12) PAOE Isl ST. LUCIE UNIT 1 05000335 1 OF7 IE ial Operation Prohibited by Technical Specifications Due to Inadequately Tested Degraded Voltage System SEQUENTIAL FACIUTYNAME DOCKET NUMBER MONTH DAY YEAR REVISION NUMBER NUMBER MONTH DAY YEAR St. Lucle Unit 2 05000389 FACIUTY NAME 5 1 97 97 006 0 6 2 97 DOCKET NUMBER 05000 OPERATINQ MODE (6) 20.2201(b) 20.2203(a)(2) (v) 60.73(e) (2) (i) 50.73(a)(2)(viii)

POWER LEVEL (10) 20.2203(0)(2)(g 20.2203(a) (3) (ii) 50.73(a) (2)(iii) 73.71 OTHER 20.2203(a)(2) (Hi) S0.36(o) (1) 50.73(a) (2)(v) Specify In Abstract below 20.2203(a)(2)(iv) or In NRC Form SBBA S0.36(c)(2) S0.73(a) (2) (v(i)

NAME TELEPHONE'UMBER OncMe Area Code)

K. W. Frehafer, Lincenslng Engineer (561) 468%284 CAUSE SYSTEM COMPONENT MANUFACTURER To NPRDS 'AUSE SYSTEM MANUFACTURER REPORTABLE To NPRDS MONTH DAY YEAR EXPECTED YES SUBMISSION (If yes, complete EXPECTED SUBMISSION DATE). X No DATE (16)

ABSTRACT (Umit 40 1400 spaces, I.e., approximately 16 s)ngie-spaced typewritten lines) (16)

On May 1, 1997, Unit 1 was in Mode 1 at 100 percent power and Unit 2 was in Mode 6 and defueled for a refueling outage. As a result of the on-going review of the Unit 2 Engineered Safety Features Actuation System (ESFAS) Test Procedure for compliance with NRC Generic Letter 96-01, it was discovered that the Safety Injection Actuation Signal (SIAS) permissive contact for degraded voltage protection was not adequately tested as required by the Technical Specifications.

The cause of the event was inadequate surveillance test procedures which did not test the degraded voltag protection system SIAS permissive contact. This contact provides an ESFAS function which initiates load shed and Emergency Diesel Generator (EDG) start for a sustained degraded voltage condition.

The Unit 1 A EDG was declared inoperable, due to a missed surveillance, at approximately 0900 on 5/1/97.

Testing of the degraded voltage system SIAS permissive was successfully performed at approximately 1630 on 5/1/97, and the 1A EDG was subsequently declared operable. Operability of the Unit 1 B EDG was demonstrated via a previous event where the degraded voltape permissive signal was provided by a Containment Isolation Actuation Signal (CIAS) contact. Testing of the Unit 2 degraded voltage system ESFAS permissives was satisfactorily completed May 9, 1997.

The Unit 2 ESFAS surveillance test procedure was revised to ensure the degraded voltage system SIAS permissive contact is tested. The Unit 1 ESFAS surveillance test procedure will be revised to ensure the degraded voltage system ESFAS permissive contacts are tested.

NRC FORM 366 (4-96)

4RC FORM 366A U.S. NUCLEAR REGULATORY COMMLSSIO I4-96)

LZCENSEE EVENT REPORT (LER)

TEXT CONTINUATION YEAR SEQUENTIAL REVISION ST. LUCIE UNIT 1 05000335 2 .OF 7 97 006 0 TEXT llfmore opooo io rerlulrod, uoo odditlonol oopko of HRC f'orm 3MAJ I17I On May 1, 1997, Unit 1 was in Mode 1 at 100 percent power and Unit 2 IH~as in Mode 6 and defueled for a refueling outage. While performing a review of the Unit 2 Engineered Safety Features Actuation System (ESFAS) fEIIS:JE] Test Procedure, 2-0400050, Rev. 22, for compliance with NRC Generic Letter (GL) 96-01, it was.discovered that the Safety Injection Actuation Signal (SIAS) permissive contact for degraded voltage protection may not have been*adequately tested in accordance with Technical Specifications.

Failure of the contact would not allow the degraded voltage system to initiate load shed and Emergency Diesel Generator (EDG) start within the time specified in the Technical Specifications.

At the time of discovery, Unit 2 was in a mode where degraded voltage protection was not required.

Engineering determined that the Unit 1 B train degraded voltage system was functional based on a previous event that demonstrated operability. However, the Unit 1 A EDG was declared inoperable and the ACTION statement for Technical Specification 3.8.1.1 was entered. The Unit 1 A train degraded voltage SIAS permissive contact was successfully tested and the 1A EDG was returned to service.

The degraded voltage protection system consists of a set of undervoltage relays, set to a higher voltage level than the loss of voltage relays, and two time. delays. The first time delay is of a length of time sufficient to establish the existence of a degraded voltage condition. At the end of this delay, an alarm in the control room alerts operators to the degraded voltage condition. An interlock with the SIAS is included such that a subsequent SIAS will immediately separate the Class 1E power distribution system from the offsite power system and the EDGs are started and loaded. The second time delay is of a limited duration such that the permanently connected Class 1E loads will not be damaged by operation at reduced voltage for that time period. Following this delay, if not corrected, the Class 1E power distribution system is separated from the offsite power system and the EDGs are started and loaded.

The St. Lucie Unit 1 and 2 Technical Specifications include limiting conditions for operation, surveillance requirements, trip setpoints,'nd allowable values for the degraded voltage relays and associated time delay relays. Since the degraded voltage protection system is. considered part of the loss of power protection system, it has been determined that the surveillance test requirements for the degraded voltage protection system should consist of functional verification every 18 months, during refueling.

The load shed and EDG start ESFAS function is tested by initiating a complete loss of power to the busses, which results in the first level of protection, the loss of voltage relays, initiating load shed and EDG start.

Functioning of load shed is thus verified only for a complete loss of power. It was determined that the SIAS permissive contact that initiates load shed and EDG start for a sustained degraded voltage condition was not verified by test, which is contrary to the Technical Specifications requirements.

There are differences between the St. Lucie Units 1 and 2 degraded voltage protection systems. These differences and the identified test deficiencies are described below:

NAG FORM 388A I4-96I

4RC FORM SSSA U.S. NUCLEAR REGULATORY COMMISSIO (4-95)

LLCENSEE EVENT REPORT (LER)

TEXT CONTINUA1 ION YEAR SEQUENTIAL REVISION ST. LUCIE UNIT 1 05000335 3 OF 7 97 006 0 TEXT /ifmore space is required, use additional copies of NRC Form 366A/ I17)

Unit 1 description:

The degraded voltage system for St. Lucie Unit 1 consists of 2 undervoltage relays (27-1 and 27-4),

connected in a 2 out of 2 logic, with permissives for SIAS, Containment Isolation Actuation Signal (CIAS),

and Main Steam Isolation Signal (MSIS). When both relays detect a degraded voltage condition with a coincident or subsequent SIAS, CIAS or IVISIS, relay 27X4 is actuated, which initiates load shed and EDG starting. See Figure 1 for a simplified drawing:

Procedure 1-0970027 calibrates and tests the undervoltage relays. Both the degraded voltage relays are actuated together but the SIAS, CIAS, or MSIS permissive contacts are jumpered out and therefore not included in the testing. The Unit 1 ESFAS procedure 1-0400050 does not test the degraded voltage ESFAS permissives; during Loss Of Offsite Power (LOOP) and LOOP/ESFAS testing, a loss of voltage is initiated by opening the startup transformer circuit breakers, producing an immediate and total loss of voltage which is detected by other undervoltage relays.

Unit 2 description:

The 4160V bus degraded voltage system for St. Lucie Unit 2 consists of 3 undervoltage relays (27M-A, 27N-B, and 27N-C), connected in a 2 out of 3 logic, with a SIAS permissive contact. When 2 of the 3 relays detect a degraded voltage condition and time out, without a coincident SIAS, an annunciator alarms in the control room to alert the operators to the degraded voltage condition. A subsequent SIAS will initiate an immediate load shed, EDG start, and load sequencing. See Figure 2 for a simplified drawing.

Procedure 2-0920020 calibrates and tests the undervoltage relays. This includes using the trip test pushbuttons for two relays at a time and observing a test light to indicate energization of the load shed bus, isolated during testing, to verify the logic. The SIAS contact is bypassed by a jumper and is not included in the testing. Procedure 2-0400053 tests the safeguards relays; however, the relays associated with the SIAS Group 7, which includes the degraded voltage permissive, are stated as being tested in accordance with OP 2-0400050, "Periodic'Test of the Engineered Safety Features." Therefore, the interlo k is not tested in this procedure. However, procedure 2-0400050, up to revision 22, did not test the degraded voltage interlock since during Loss Of Offsite Power (LOOP) and LOOP/ESFAS testing a loss of voltage is initiated by opening the startup transformer circuit breakers, producing an immediate and total loss of voltage which is detected by other undervoltage relays.

The cause of the event was inadequate ESFAS surveillance test procedures in that the SIAS permissive contact that initiates load shed and EDG start for a sustained degraded voltage condition was not verified by test. This latest issue was found as part of the continuing review of St. Lucie test and surveillance procedures against the plant Technical Specifications requirements as committed to in response to GL 9-

01. St. Lucie has reported previous discoveries in the past. GL 96-01 recognized that surveillance NRC FORM 388A I4-951

SRC FORM SSSA (4-95)'ICENSEE EVENT REPORT (LER)

U.S. NUCLEAR REGULATORY COMMISSIO TEXT CONTINUATION YEAR SEQUENTIAL REVISION ST. LUCIE UNIT 1 05000335 4 OF 7 97 006 0 TEXT /ifmore space is rerluired, use addilionel copies of NRC Farm 366A/ '17I procedures may not adequately test all required logic paths, and the industry as a whole has identified and reported problems found as a result of th'ese reviews.

his event is reportable in accordance with 10 CFR 50.73(a)(2)(i)(B), as any operation prohibited by the plant's Technical Specifications.

Degraded voltage protection is a requirement instituted as a result of incidents at the Millstone and Arkansas Nuclear One plants. These events disclosed the possibility of degraded voltage conditions that co uld exist on plant emergency busses undetected by the loss of offsite power relays. Sustained operation at lower voltages could cause damage to safety related components. Branch Technical Position PSB-1 re quired the installation of a degraded voltage protection system that would prevent this occurrence, in ad dition to the loss of voltage relays.

PSB-1 also imposed requirements that the plant Technical Specifications be revised to include limiting conditions for operation, surveillance requirements, trip setpoints, and allowable values for the degraded voltage relays and associated time delay relays. The Technical Specifications for St. Lucie Units 1 and 2 incorporated the requirements for degraded voltage protection in accordance with PSB-1. Since the degraded voltage protection system is considered part of the loss of power protection system, it has been determined that the surveillance test requirements for the degraded voltage protection system should consist of functional verification every 18 months, during refueling.

0 perability of 'tlie Unit 1 B train degraded voltage system was demonstrated via the event described in LER 33 5 96-007, where the degraded voltage permissive signal was provided by a CIAS contact. This resulted in load shed of the B train emergency busses and start of the 1B EDG. This constituted an acceptable test SI nce performance of the Integrated Safeguards procedure demonstrates that a SIAS signaI will initiate a C IAS signal. Therefore, credit was taken for an operable degraded voltage permissive signal.

S ince surveillance testing had not been performed for the Unit 1 A train, the 1A EDG was declared in operable, due to a missed surveillance, at approximately 0900 on 5/1/97. A Letter of Instruction was P repared to perform testing to verify the functioning of the SIAS permissive contact (LOI ¹1-LOI-l&C-18 ).

The scope of-the I Ol test procedure was limited to verification of the SIAS permissive contact used in the d egraded voltage actuation logic (as opposed to SIAS, CIAS and MSIS). Based upon review of the design b sis for the degraded voltage circuit, the presence of the CIAS and MSIS permissive contacts is considered to be a conservative design feature, not required by the Technical Specifications; therefore, surveillance te sting of the CIAS and MSIS permissive contacts is not required. Testing was successfully performed at ap proximately 1630 on 5/1/97, functioning of the SIAS permissive was verified, and the 1A EDG was d clared operable.

Testing was successfully performed on both A and B trains of the Unit 2 degraded voltage system SIAS P ermissive contacts as of May 9, 1997. This completes the GL 96-01 reviews for Unit 2. The Unit 1 re views will be completed by the end of the Fall 1997 Unit 1 Cycle 15 refueling outage.

l

%RC FORM SSSA U.S. NUCLEAR REGULATORY COMMISSIO (4-95)

LICENSEE EVENT REPORT (LER)

TEXT CONTINUATION YEAR SEQUENTIAL REVISION ST. LUCIE UNIT 1 05000335 5 'OF 7 97 006 0 TEXT (/fmore speceis required, use edditionel copies of NRC Form 3MAi I17I In general, surveillance procedures for St. Lucie Units 1 and 2 provide for calibratioh and test of the degraded voltage'etection relays, time delay relays, and the relay logic. Although the degraded voltage protection ESFAS permissive contacts had not been specifically tested during past ESFAS test surveillances, testing has been satisfactorily performed that verifies the operability of these conta'cts.

Therefore, this condition had no adverse affect on the protection of the health and safety of the public.

Testing of the Unit 1 A train degraded voltage protective system ESFAS functions was successfully demonstrated on May 1, 1997.

2. The Unit 2 ESFAS Test Procedure (2-0400050) was revised to incorporate testing of the SIAS interlock with degraded voltage protection. Testing of the degraded voltage protection SIAS interlock for both Unit 2 trains was completed on May 9, 1997.

3. The Unit 1 ESFAS Test Procedure (1-0400050) will be revised to incorporate testing of the SIAS degraded voltage protection permissive contacts.

LER 389 96-007 describes the discovery of a failure to adequately test the MSIS Actuation Logic during GL 96-01 reviews.

LER 389 96-006-0 describes the discovery of a failure to adequately test Auxiliary Feedwater Actuation Logic during GL 96%1 reviews.

y LER 389 96-005-0 describes the discovery of a failure to adequately test the Reactor Trip Breakers during GL 96-01 reviews.

LER 335 96-007 describes the incident where the degraded voltage permissive signal was provided by a CIAS contact.

NRr,'RAM sRRd (d 4fil

NRc FORM 366A U.S. NUCLEAR RMULATORYCOMMISSIO 14-95)

L1CENSEE EVENT REPORT (LER)

TEXT CONTINUATION YEAR SEQUENTIAL REVISION ST. LUCIE UNIT 1 05000335 6 OF 7 1 97 006 0 TEXT Iifmore spece is reqvired, use edditionel copies of NRC Form 366AI I 17) 27~ I 27<

CIS SIAS MSIS 27x4 A CONTACT FROM 27X4 INITIATES 4.16KV LOAD SHED AND EDG START I

Figure 1 Unit 1 Degraded Voltage Protection Scheme UPI cll410 lRRh M,OCl

0 10 NRC FCRM 366A U.S. NUCLEAR REGULATORY COMMISSIO

$ 4 95)

LICENSEE EVENT REPORT (LER)

TEXT CONTINUATION YEAR SEQUENTIAL REVISION St. Lucie Unit 1 05000335 7 OF 7 97 006 0 TEXT llfmore space i's required, use additional copies of NRC Form 388Al I17I

(+)

27N-A 27N-C 27N-C 2l3 COINCIDENT LOGIC 27N-B 27N-A 27DX

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27DX'RIP SIAS (GROUP 7)

BUS 0 0 ENERGIZING THIS BUS INITIATES LOAD SHED AND EDG START Figure 2 Unit 2 Degraded Voltage Protection Scheme NAc FORM 388A I4-95)