ML18038B932

LER 97-003-00:on 970711,determined That HPCI Turbine Speed Lower than Indicated.Caused by Improper Evaluation of Valve Leak.Work Orders to Troubleshoot HPCI Initiated

ML18038B932
Person / Time
Site:	Browns Ferry
Issue date:	08/07/1997
From:	Jay Wallace TENNESSEE VALLEY AUTHORITY
To:
Shared Package
ML18038B931	List: ML18038B930 ML18038B932
References
LER-97-003-03, LER-97-3-3, NUDOCS 9708140241
Download: ML18038B932 (10)

Text

NRC FORM 366 U.. UCLEAR REGULATORY COMMISSION APPROVED BY OMB NO. 3150%104

(~5) EXPIRES 04/30/98 ESTIMATED BURDEN PER RESPONSE TO COMPLY WITH THIS MANDATORYINFORMAIION COLLECTION REQUEST:

LICENSEE EVENT REPORT (LER) 50.0 HRS. REPORTED LESSONS LEARNED ARE INCORPORATED INTO THE UCENSING PROCESS AND FED BACK TO INDUSTRY. FORWARD COMMENTS REGARDING (See reverse for required number of BURDEN ESTIMATE TO THE INFORMATIONAND RECORDS digits/characters for each block) MANAGEMENT BRANCH IT% F33), UD. NUCLEAR REGUIATORY COMMISSION, WASHINGTON. DC 205554001, FAclLITYNAMs 11) DOCKET NVMDER IT) PAos G)

Browns Ferry Nuclear Plant (BFN) Unit 2 05000260 1OF5 T)TLs Ia)

Field measurements of the HPCI turbine speed indicated speed was lower than the speed displayed in Control Room.

The cause was an improper evaluation of a valve leak which resulted in water intrusion into a unsealed junction box.

EVENT DATE (5) LER NUMBER 6 REPORT DATE (7) OTHER FACIUTIES INVOLVED (8)

FACIUTY NAME MDNTH SEQUENTIAL REVISION MONTH DAY YEAR DAY YEAR NUMBER NUMBER N/A FAClUTY NAME 97 97 s 07 97 N/A OPERATING THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR: Check one or more) (11)

MODE (9) 20.2201(b) 20.2203(a)(2)(v) 50.73(a) (2)(l) 50.73(a) 20,2203(a)(1) 50.73(a)

POWER LEVEL (10)

'00 20.2203(a)(2)(l) 20.2203(a)(3)(l) 20.2203(a)(3)(ii) 50.73(a)(2)(ll) 50.73(8)(2)(ill) 73.71 20.2203(a)(2)(ii) 20.2203(a)(4) 50.73(a)(2)(iv) OTHER 20.2203(a)(2)(iii) 50.36(c)(1) 50.73(a)(2)(v) 20.2203(a)(2)(iv) 50.36(c)(2) 50.73(a)(2)(vii) below or in LICENSEE CONTACT FOR THIS LER (12)

TELEPHONE NL/MBER Ilododa Area Coda)

James E. Wallace, Ucensing Engineer (205) 729-7874 COMPLETE ONE LINE FOR EACH. COMPONENT FAILURE DESCRIBED IN THIS REPORT (13 CAUSE SYSTEM COMPONENT MANUFACTURER REPORTABLE TO NPRDS CAUSE SYSTEM COMPONENT MANUFACTURER REPORTABLE TO NPRDS SUPPLEMENTAL REPORT EXPECTED (14) MONTH DAY YEAR EXPEGTED YES SUBMISSION (If yes, complete EXPECTED SUBMISSION DATE). X NO DATE (15)

ABSTRACT (Limit to 1400 spaces, I.e., approximately 15 singlewpaced typewritten lines) (16)

On July 11, 1997, at 1910 hours0.0221 days <br />0.531 hours <br />0.00316 weeks <br />7.26755e-4 months <br />, with Units 2 and 3 at 100 percent power, and Unit 1 defueled, it was determined that the HPCI turbine speed was lower than indicated. Specifically, during the performance of a surveillance instruction (Sl) for testing the HPCI flow rate at normal reactor vessel pressure, field measurements of the HPCI turbine speed IdentiTied that the HPCI turbine speed was lower than the speed displayed in the Unit 2 Control Room. Since the HPCI turbine speed did not meet its Sl acceptance criteria, HPCI was declared inoperable. The root cause of this faulty display was due to an improper evaluation of a valve leak. The valve leak resulted in water intrusion ln an unsealed unction box causing grounds to some HPCI cables. HPCI was declared inoperable. The immediate corrective actions ncluded troubleshooting and sealing of the junction box. Corrective actions to preclude recurrence will be to perform and document a walkdown of the HPCI, RCIC, and Reactor Feedwater Pump rooms where steam condensate could leak on Junction boxes and to seal those conduit terminations deemed to be unacceptable. This report is submitted in accordance with 10 CFR 50.73 (a)(2)(v) as any event or condition that alone could have prevented the fulfillment of thB safety function of structures or systems needed to mitigate the consequences of an accident. No previous LER was Identified where HPCI turbine speed was affected by water intrusion.

9708i40241 970807 PDR ADOCK 05000260 S PDR

NRC FORM 366A U.S. NUCLEAR REGULATORY COMMISSION (466' LICENSEE EVENT REPORT (LER)

TEXT CONTZNUATZON FACILITY NAME DOCKET LER NUMBER NUMBER NUMBER Bzowns Ferry Unit 2 05000260 2 of 5 97 -- 003 -- 00 T more space s requir ~ use a iriona copies o orm I1 )

Z. PLANT COND ZTZONS At the time of the discovery of the condition, Unit 2 and Unit 3 were at 100 percent power. Unit 1 was shutdown and defueled.

ZZ. DESCRZPTZON OF EVENT A. Event On July HPCI [BJ]

ll,turbine 1997, at approximately 1910 hours0.0221 days <br />0.531 hours <br />0.00316 weeks <br />7.26755e-4 months <br /> during the testing of speed [TAC] at normal RPV pzessuze surveillance instruction (2-SZ-4.5.E.1.d)., field measurements identified that

.the HPCI turbine speed was lower than the speed displayed in the Unit 2 Control Room. Since the HPCZ turbine speed did not meet its surveillance instruction acceptance criteria, HPCI was declared inoperable.

At 2200 hours0.0255 days <br />0.611 hours <br />0.00364 weeks <br />8.371e-4 months <br />, TVA made a four-hour notification to the NRC concerning the inoperability of HPCZ in accordance with 10 CFR 50.72(b)(2)(iii).

Diagnostic data and observations made during HPCI testing indicated the presence of a station ground that was affecting the HPCI tachometer. Grounding tests of the tachometer to component cables indicated some but not all cables had ground shorts. A review of HPCI connection diagrams revealed potential inspection points for grounds within a junction box. This junction box was opened, and water intrusion and terminal box corrosion was evident. The junction box terminal strips were replaced and two conduit terminations were sealed to make them watertight. At 1501 hours0.0174 days <br />0.417 hours <br />0.00248 weeks <br />5.711305e-4 months <br /> on July 15, 1997, after the calibration of the tachometer, the flow rate testing was successfully reperformed. HPCZ was declared operable, and HPCI was returned to service.

This report is submitted in accordance with 10 CFR 50.73 (a)(2)(v) as any event or condition that alone could have prevented the fulfillment of the safety function of structures or systems needed to mitigate the consequences of an accident.

B. Zno erable Structures Co onents or S stems that Contributed to the Event:

None.

NRC FORM 366A (445)

NRC FORM 366A 0 U.S. NUCLEAR REGULATORY COMMISSION (4-95)

LICENSEE EVENT REPORT (LER)

TEXT CONTINUATION ZACILITY NAME DOCKET NUMBER NUMBER Browns Ferry Unit 2 05000260 3 of 5 97 003 00 TEXT more space s requir, use a irioea copies o orm (17)

C. Dates and A roximate Times of Ma or Occurrences:

July 11, 1997 at 1910 hours0.0221 days <br />0.531 hours <br />0.00316 weeks <br />7.26755e-4 months <br /> CDT During a Surveillance Instruction, HPCI turbine speed was lower than indicated on Unit 2 control Room instrumentation.

Since the HPCI turbine speed did not meet its surveillance instruction acceptance criteria, HPCI was declared inoperable.

at 2200 hours0.0255 days <br />0.611 hours <br />0.00364 weeks <br />8.371e-4 months <br /> CDT A four-hour notification was made to the NRC in accordance with 10 CFR 50.73'(b)(2)(iii) .

July 15, 1997 at 1501 hours0.0174 days <br />0.417 hours <br />0.00248 weeks <br />5.711305e-4 months <br /> CDT After troubleshooting efforts, HPCI was declared operable and was returned to service.

D. Other S stems or Seconda Functions Affected:

None.

E. Method of Discove The condition was discovered when field measurements indicated that the HPCI turbine speed did not meet HPCI acceptance criteria.

F. erator Actions:

Operators tripped HPCI and declared it inoperable.

G. Safet S stem Re onses:

None.

CAUSE OF THE EVENT A. Immediate Cause:

The immediate cause of the condition was that the HPCI turbine speed did not meet its required acceptance criteria during an SI.

NRC FORM 366A (4-95)

iO NRC FORM 366A U.S. NUCLEAR REGULATORY COMMISSION (4.95)

LZCENSEE EVENT REPORT (LER)

TEXT CONTINUATION PACZLZTZ NAME DOCKET PAGE NUMBER NUMBER Browns Ferry Unit 2 05000260 4 of 5 97 003 00 TEXT more space requir, use s iuo copies o orm (17)

B. Root Cause:

The root cause of this event was due to an improper evaluation of a valve leak". The valve leak resulted in water intrusion causing grounds on some HPCI cables in an unsealed junction box.

C. CONTRIBUTING FACTOR The junction box involved in this event was not sealed, nor was it required to be sealed by TVA drawings.

to allow any water intrusion to drain. Since the conduit No weep hole was found termination was not watertight and the conduit termination was over the center line .of the terminal strips, water fell on the strips causing spurious grounds.

This conclusion is supported by the fact that an erratic tachometer reading disappeared after the junction box terminal strips were replaced and two conduit tezminations were sealed to make them watertight.

ZV. ANAIiYSZS OF THE EVENT The HPCI system is provided to ensure that the reactor is adequately cooled to limit fuel cladding temperature in the event of a small line break in the nuclear system and loss of coolant which does not result in rapid depressurization of the reactor vessel. The HPCI system permits the plant to be shutdown while maintaining inventory until the reactor vessel is depressurized.

The grounds in the HPCI cables affected only the turbine speed indications and had no effect on the automatic operations of HPCI.

HPCI would have been able to perform its safety function (e.g., rated flow, etc.). Therefore, the safety of the plant, its personnel or the public was not compromised.

V. CORRECTZVE ACTIONS A. ImrMidiate Corrective Actions:

Operations personnel tripped HPCI. Work orders to troubleshoot HPCI were initiated.

Calibrations were performed to ensure various subcomponents were within calibration criteria which could have resulted in the event. Troubleshooting continued until the root cause of the event was identified. Rework of the junction box and subsequent successful performance of the SI ensured that HPCI will be able to perform its intended safety function. HPCI was declared operable and returned to service.

NRC FORM 366A (445)

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NRC FORM 366A U.S. NUCLEAR REGULATORY COMMISSION (495)

LICENSEE EVENT REPORT (LER)

TEXT CONTINUATION FACZLZTY NAME DOCKET NUMBER NUMBER Browns Ferry Unit 2 05000260 5 of 5 97 003 00 T moro space m requir ~ use a buona copes o orm (1 )

B. Corrective Actions to Prevent Recurrence:

Corrective actions to preclude recurrence will be: (1) to perform and document a walkdown of the HPCI, RCIC, and Reactor Feedwater Pump rooms where steam condensate could leak on junction boxes and to seal those conduit terminations deemed to be unacceptable, (2) to develop continuing training modules tb address this event and management expectations on reviewing the effects of plant leaks and the reporting of such leaks, (3) to issue a Site Bulletin to heighten the awareness of plant personnel to this event.

vz. ADDZTZOMAL ZHFORHKTZON A. Failed Co onents:

None.

B. Previous LERs on Similar Events:

TVA has previously issued LERs for an inoperable HPCI due to various design and equipment concerns. However, water intrusion was not the cause in any of the previous LERs. Therefore, no previous LER corrective actions would have precluded this event.

VZZ. COMMZITIENTS Junction box walkdowns will be performed and documented foz the HPCI, RCIC, and reactor feedwatez pump rooms where steam condensate could leak on junction boxes. Based on the walkdowns, conduit terminations deemed to be unacceptable will be sealed by September 8, 1997.

Training will develop continuing training modules to address this event and management expectations on reviewing the effects of plant leaks and the reporting of such leaks. These modules will be completed by December 22, 1997.

A Site Bulletin will be issued to heighten the awareness of plant personnel to this event. This bulletin will be issued by September 10, 1997.

Energy Industry Identification System (EIIS) system and component codes are identified in the text with brackets (e.g., [XX]).

NRC FORM 366A (4-95)

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