ML18036A340

LER 91-015-00:on 910731,HPCI Sys Did Not Fulfill Safety Function Resulting from Low Suction Pressure Condition During Fast Startup.Caused by Design Deficiency.Permanent Time Delay Relay installed.W/910830 Ltr

ML18036A340
Person / Time
Site:	Browns Ferry
Issue date:	08/30/1991
From:	Jay Wallace, Zeringue O TENNESSEE VALLEY AUTHORITY
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
LER-91-015-01, LER-91-15-1, NUDOCS 9109090134
Download: ML18036A340 (12)

Text

ACCELERATED DISTRIBUTION DEMONS TION SYSTEM REGULATORY INFORMATION DISTRIBUTION SYSTEM (RIDS)

ACCESS10N NBR:9109090134 'DOC.DATE: 91/08/30 NOTARIZED: NO DOCKET FACIL:50-260 Browns Ferry Nuclear Power Station, Unit 2, Tennessee 05000260 AUTH. NAME 'UTHOR AFFILIATION WALLACE,J.E. Tennessee Valley Authority ZERINGUE,O.J. Tennessee Valley Authority RECIP.NAME RECIPIENT AFFILIATION

SUBJECT:

LER 91-015-00:on 910731,tripped occurred re HCIC sys.Caused by problem not anticipated zn design.HPCI turbine manually tripped & Temporary 'tame delay relays installed under D Temporary Alteractzon Control Form.W/910830 ltr.

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

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

NOTES: A RECIPIENT COPIES RECIPIENT COPIES D ID CODE/NAME LTTR ENCL ID CODE/NAME LTTR ENCL SANDERS,M.'OSS,T.

1 1 HEBDON,F 1 1 D 1 1 INTERNAL: ACNW 2 2 ACRS 2 2 AEOD/DOA 1 1 AEOD/DSP/TPAB 1 1 AEOD/ROAB/DSP 2 2 NRR/DET/ECMB 9H 1 1 NRR/DET/EMEB 7E 1 1 NRR/DLPQ/LHFB10 1 1 NRR/DLPQ/LPEB10 1 1 NRR/DOEA/OEAB 1 1 NRR/DREP/PRPB11 2 2 NRR/DST/SELB .8D 1 1 NRR/DST/SICB8H3 NRR/DST/SRXB 8E 1

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D NOTE TO ALL "RIDS" RECIPIENTS:

PLEASE HELP US TO REDUCE WASTE! CONTACT THE DOCUMENT CONTROL DESK, ROOi~I P1.-37 (EXT. 20079) TO ELliv!!NATE YOUR NAME FROM DISTRIBUTION LISTS FOR DOCUMENTS YOU DON'T NEED!

FULL TEXT CONVERSION REQUIRED TOTAL NUMBER OF COPIES REQUIRED: LTTR 33 ENCL 33

0 'L Tennessee Vatfey Authority, Post Office Box 2000, Decatur, 'Alabama 35609 O. J; 'Ike Zeringue Vice President. Browns Ferry Operations AU6 .3.0 1991 U.S'. Nuclear Regulatory Commission ATTN: Document Control- Desk

'Washington, D.C. 20555

Dear Sir:

TVA BROWNS FERRY NUCLEAR PL'ANT (BFN) UNIT 2 DOCKET NO. '50-260 FACILITY OPERATING LICENSE DPR-52 LICENSEE EVENT REPORT LER-50-260/91015 The enclosed report provides details concerning a condition, that alone could have prevented the High Pressure Coolant Injection system from

fulfilling its intended safety function. This even't resulted from a low suction pressure transient. This report. is submitted in accordance with 10 CFR 50.73(a)(2)(v).

Very truly yours, ESSEE VALLEY AUTHORITY 0.~~ Zeringu

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Enclosure cc: see .page 2 CG":C46 9105'050134 91f.f830 Pl:tr~ ADOCK 0.""0002yp0 9 PDR

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2 AUG 30 1991 t

U.S'. Nuclear Regulatory:Commission cc (Enclosure):

INPO Records Center Suite 1500 1100 Circle 75 Parkway Atlanta, Georgia 30339 NRC Resident Inspector, BFN Regional Administrator U.S. Nuclear 'Regulatory Commission Region II 101 Marietta Street, Suite 2900 Atlanta, Georgia 30323 Thierry M. Ross U.S. Nuclear Regulatory Commission One White Flint, North 11555 Rockville Pike Rockville, Maryland 20852

)I NRC Form 366 NUCLEAR REGULATORY COl%GSSION Approved OMB No. 3150-0104 (6-89) Expires 4/30/92 LICENSEE EVENT REPORT (LER)

FACILITY NAME (1) iDOCKET NUMBER (2) w F r i TITLE (4) High Pressure Coolant Injection (HPCI) System Did Not Fulfill Its Fn in 1 'Frmw i r n in F r T DAY I I I SE()UENTIAL I IREVISIONI I I I FACILITY NAMES IDOCKET NUMBER(S)

T Y

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1 I

1 I I I 1

I I I 083 09 I I 1

OPERATING I,ITHIS REPORT IS SUBMITTED PURSUANT TO THE RE()UIREMENTS OF 10 CFR 5:

MODE I I n ll win 11 I20.402(b) )20.405(c) (50.73(a)(2)(iv) )73.71(b)

POWER I /20.405(a)(l)(i) i50.36(c)(l) )~[50.73(a)(2)(v) )73.71(c)

LEVEL I /20.405(a)( l)(ii) i50.36(c)(2) (50.73(a)(2)(vii) [OTHER (Specify in l20.405(a)(l)(iii) /50.73(a)(2)(i) [50.73(a)(2)(viii)(A) ) Abstract below and in

[20.405(a)(l)(iv) /50.73(a)(2)(ii) )50.73(a)(2)(viii)(B) ( Text, NRC Form 366A) 4 1 v NTA F NAME I AREA CODE I i r P T P N I I iREPORTABLEi I I I iREPORTABLEi Y T T N F P I I I I P R P D 4 I

SUBMISSION Y m T ABSTRACT (Limit to 1400 spaces, i.e., approximately fifteen single-space typewritten lines) (16)

On July 31, 1991 at 1313 hours0.0152 days <br />0.365 hours <br />0.00217 weeks <br />4.995965e-4 months <br />, TVA began a performance test of the High Pressure Coolant Injection (HPCI) System. This test was part of the Unit 2 power ascension program. At the time, Unit 2 was at 77 percent power with a reactor temperature and pressure of 542'F and 965 psig. The HPCI system tripped from a low suction pressure transient. This HPCI system trip was reset automatically after approximately 10 seconds. This trip could have prevented the HPCI system from fulfilling its intended safety function. Therefore, this event is reportable in accordance with 10 CFR 50.73(a)(2)(v).

The root cause of this event is a problem not anticipated in design. It is apparent that the HPCI system may be subject to momentary, suction pressure transients capable of tripping the 'HPCI turbine. Ten seconds after the HPCI system tripped, the HPCI system restarted due to a start signal still being present. During the restart no low-pressure transient was experienced and the HPCI system ran for approximately five minutes.

The Immediate Corrective Action was to declare the HPCI system inoperable and the HPCI turbine was manually tripped. Temporary time delay relays were installed under a Temporary Alteration Control Form. HPCI injection to the reactor vessel was retested and HPCI was declared operable.

The long-term corrective action is to install permanent time delay relays on Units 1, 2 and 3. These installations will preclude a recurrence of this event.

NRC Form 366(6-89)

4 NRC Form A. U NU LEAR RE ULATORY OMNI SION Approve MB No. 150- 1 (6-89) Expires 4/30/92 LICENSEE EVENT REPORT (LER)

TEXT CONTINUATION FACILITY NAME (-1) IOOCKET NUMBER (2)

I I I ISEQUENTIAL I IREVISIONI I I I I I I I I I Br w F r TEXT (If more space is required, use additional NRC Form 366A's) (17)

On July 31, 1991 at 1313 hours0.0152 days <br />0.365 hours <br />0.00217 weeks <br />4.995965e-4 months <br />, TVA began conducting,a High Pressure Coolant Injection (HPCI) [BJ] performance test. This test was included in the BFN Power Ascension Program due to the significant amount of work performed on the HPCI system during the extended outage. At the time, Unit 2 was at 77 percent power with the reactor temperature and pressure of 542'F and 965 psig.

At 1320 hours0.0153 days <br />0.367 hours <br />0.00218 weeks <br />5.0226e-4 months <br />, a test start signal was generated to autostart the HPCI system to inject water from a condensate storage tank [KA] to the reactor vessel. During the HPCI system initiation, a low-pressure transient occurred on the HPCI system suction line. As designed, the HPCI system automatically tripped when the transi.ent occurred. After approximately 10 seconds, due to the start signal still being present, the HPCI system restarted and pumped coolant water to the reactor vessel without any additional low suction pressure transients.

As a result of the HPCI system trip and subsequent restart, the system did not meet the rated flow time requirement of 30 seconds as described in the final'afety analysis report. Accordingly, at 1320 hours0.0153 days <br />0.367 hours <br />0.00218 weeks <br />5.0226e-4 months <br /> the system was declared inoperable and limiting condition for operation (LCO) was entered. At 1325 hours0.0153 days <br />0.368 hours <br />0.00219 weeks <br />5.041625e-4 months <br />, after a brief discussion between the test director (non-utility, nonlicensed) and the Shift Operating Supervisor (utility, licensed), the HPCI system was manually tripped in the Unit 2 control room.

At 0640 hours0.00741 days <br />0.178 hours <br />0.00106 weeks <br />2.4352e-4 months <br /> on August 1, 1991, a temporary alteration to install a time delay relay in the low suction pressure trip circuitry was completed. At 1745 hours0.0202 days <br />0.485 hours <br />0.00289 weeks <br />6.639725e-4 months <br />, on August 1, 1991, the HPCI system performance test was completed, HPCI system was declared operable, and the LCO was exited.

This event was a result of a condition which alone could have prevented the fulfillment of an intended safety function and is reportable in accordance with 10 CFR 50.73(a)(2)(v) ~

The HPCI system is an emergency system that can be used to maintain an adequate coolant inventory inside the reactor vessel to prevent fuel clad melting as a result of postulated small breaks in the nuclear system process barrier. The system is designed to accomplish its safety function on a short-term basis without reliance on plant auxiliary power supplies other than the DC power supply. It is a part of the Emergency Core Cooling System (ECCS). The HPCI system is a single-train system.

Automatic Depressurization system (ADS), Residual Heat Removal/Low-pressure Coolant Injection system [BO], and Core Spray system [BM] provide an alternate means of fulfilling its safety function.

TS 3.5.E.2'llows the reactor to remain in operation for a period not to exceed seven days if the HPCI is inoperable, and if the redundant system and Reactor Core Isolation Cooling (RCIC) [BN] system is operable.

NRC Form 366(6-89)

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NRC orm 366 CL 0 CO SS 0 Approved NB No. 3150- 0104 (6-89) Expires 4/30/92 LICENSEE EVENT REPORT (LER)

TEXT CONTINUATION FACILITY NANE (1) IDOCKET NUNBER (2)

I I

'I I SEQUENTIAL I lREVISIONI I I I I I I I I I w rr i TEXT (If more space is required, use additional NRC Form 366A's) (17)

The design basis of the plant continued to be satisfied by the ability of Automatic Depressurization System to rapidly reduce reactor vessel pressure in a loss of coolant accident situation in which the HPCI fail's to automatically maintain reactor vessel water level and by the required Low-Pressure Coolant Injection systems being operable. Since alternate means of fulfilling HPCI's safety function were available, there was no safety consequence resulting from this event.

The root cause of this event is a .problem not anticipated in design. TVA personnel were unaware of the potential for a spurious, HPCI low suction pressure trip during turbine startup with a suction path available (i.e., no suction path valves closed). Although TVA had not received prior notification, discussions with the vendor revealed that the HPCI system is subject to momentary, suction pressure transients capable of tripping the HPCI turbine during a fast start-up.

The immedi'ate corrective actions were to manually trip the HPCI turbine and declare the system inoperable. TVA entered into LCO allowed by. TS 3.5.E.2.'o correct the condition, TVA installed a low suction pressure time delay relay. In the near term, this time delay relay has been installed as a temporary alteration. HPCI injection to reactor vessel was retested and HPCI was declared operable.

The long-term corrective=action is to install permanent time delay relays on Units 1 and 3 in the HPCI prior to each unit's next restart. Additionally, a permanent time delay relay will be installed on Unit 2 by September 30, 1991. These installations will preclude a recurrence of ~this event.

None.

A permanent low suction pressure trip time delay relay will be installed before Unit 1 restart.

A permanent low suction pressure trip time delay relay will be installed in Unit 2 by September 30, 1991.

A permanent low suction pressure trip time delay relay will be installed before Unit 3 restart.

Energy Industry Identification System (EIIS) 'Codes are identified in the text as [XZ].

NRC Form 366(6-89)

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