ML18036B338

LER 93-007-00:on 930527,mechanical Seal for 2A Reactor Recirculation Pump Failed.Caused by Inadequate Procedures. Site Procedures Revised to Require Seal Purge Flow to Be established.W/930623 Ltr

ML18036B338
Person / Time
Site:	Browns Ferry
Issue date:	06/23/1993
From:	Knuettel E, Zeringue O TENNESSEE VALLEY AUTHORITY
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
LER-93-007-01, LER-93-7-1, NUDOCS 9306300206
Download: ML18036B338 (18)

Text

ACCEI.ERATED'OCUMENT DISTKKUTIONSYSTEM REGULA'ZOY INFORMATION DISTRIBUTIO!SYSTEM (RIDE)

ACCESSION NBR:9306300206 DOC.DATE: 93/06/23 NOTARIZED: NO DOCKET FACIL 50-260 Browns Ferry Nuclear Power Station, Unit 2, Tennessee 05000260 AUTH. NAME KNUETTEL,E.T.

'UTHOR AFFILIATION Tennessee Valley Authority ZERINGUE,O.J. Tennessee Valley Authority RECIP.NAME RECIPIENT AFFILIATION'UBJECT:

LER 93-007-00:on 930527,mechanical seal for 2A reactor recirculation pump failed. Caused by inadequate procedures.

Site procedures revised to require seal purge flow to be established.W/930623 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 LTTR ENCL ID- CODE/NAME LTTR ENCL PD2-4 1 1 PD2-4-PD 1 1 ROSS,T. 1 1 INTERNAL: ACNW 2 2 ACRS 2 2 AEOD/DOA 1 1 AEOD/DSP/TPAB 1 1 AEOD/ROAB/DSP 2 2 NRR/DE/EELB 1 1 NRR/DE/EMEB 1 1 NRR/DORS/OEAB 1 1 NRR/DRCH/HHFB 1 1 NRR/DRCH/HICB 1 1 NRR/DRCH/HOLB .1 1 NRR/DRIL/RPEB 1 1 NRR/DRSS/PRPB 2 .

2 RR'/DSSA/SPLB 1 1 NRR/DSSA/SRXB 1 1 EG FILE 02 1 1 RES/DSIR/EIB 1 1 RGN2 FILE 01 1 1 EXTERNAL'G&G BRYCEF J ~ H 2 2 L ST LOBBY WARD 1 1 NRC PDR 1 1 NSIC MURPHYFG.A 1 1 NSIC POOREFW 1 1 NUDOCS FULL TXT 1 1 NOTE TO ALL"RIDS" RECIPIENTS:

PLEASE HELP US TO REDUCE WASTEI CONTACI'HE DOCUMENT CONTROL DESK, ROOM Pl-37 (EXT. 504-2065) TO ELIMINATEYOUR NAME FROM DISTRIBUTION LISTS FOR DOCUMENTS YOU DON'T NEED!

FULL TEXT CONVERSION REQUIRED TOTAL NUMBER OF COPIES REQUIRED: LTTR '32 ENCL 32

Tennessee Valley Autftority, Post Office Box 2000, Decatur, Alabama 35609.2000 O. J. "Ike" Zeringue Vice President. Browns Ferry Nuclear Plant June 23, 1993 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, D.C. 20555

Dear Sir:

TVA BROWNS FERRY NUCLEAR PLANT (BFN) UNITS 1, 2, AND 3 DOCKET NOS. 50-259, 260, AND 296 FACILITY OPERATING LICENSE DPR-33, 52, AND'8 LICENSEE EVENT REPORT 50-260/93007 The enclosed report provides details concerning a manual reactor shutdown due to a recirculation pump seal leak. This event occurred during startup from the Unit 2, Cycle 6 refueling outage.

This report is submitted in accordance with 10 CFR 50.'73(a)(2)(i)(A) due to the manual shutdown of the plant as required by technical specification.

requirements.

Sincerely,

0. J. Zeringue Enclosure cc: See page 2 rgu>

9306300206 930623 PDR ADOCK 05000260

-PDR

0 U.S. Nuclear Regulatory Commission June 23, 1993 cc (Enclosure):

INFO Records Center Suite 1500 1100 Circle 75 Parkway Atlanta, Georgia 30339 Paul Krippner American Nuclear Insurers Town Center, Suite .300S 29 South Main Street West Hartford, Connecticut 06107 NRC Resident Inspector Browns Ferry Nuclear Plant Route 12, P.O. Box 637 Athens, Alabama 35609-2000 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

NRC Form 366 NUCLEAR REGULATORY COttlISSION Approved OHB No. 3150-0104 (6-09) Expires 4/30/92 LICENSEE EVENT REPORT (LER)

FACILITY NAHE (1) IDOCKET NUMBER (

r wn rr N 1 r P TITLE (4) Reactor Shutdown Due To Recirculation Pump Seal Leakage.

V T D SEQUENTIAL I IREVISIONI I I I FACILITY NAHES IDOCKET NUHBER(S)

I I I I I N 0 I I I I I I I I I I I OPERATING I ITHIS REPORT IS SUBHITTED PURSUANT TO THE REQUIREHENTS OF 10 CFR 5:

NODE w I I N I20.402(b) IZ0.405(c) I50.73(a)(2)(iv) I73.71(b)

POWER I I20.405(a)( l)(i ) I ISO 36(c)(1) I50.73(a)(2)(v) I73.71(c)

LEVEL I20.405(a)( l)(ii) I50.36(c)(2) I50.73(a)(2)(vii) IOTHER (Specify in I

I20.405(a)( l)(iii ) I~I50.73(a)(2)(i) I50.73(a)(2)(viii)(A) I Abstract below and'n I20.405(a)( l)(iv) I50.73(a)(2)(ii) I50.73(a)(2)(viii)(B) I Text, NRC Form 366A)

.4 1 v 1 I AREA CODE T. n m li n i n i r N F P NT IREPORTABLEI IREPORTABLEI I I Y T N N F I I I I 0 P I I PP N P I SUBHISSION I I I f m 1 D ABSTRACT (Limit to 1400 spaces, i.e., approximately fifteen single-space typewritten lines) (16)

On May 27, 1993, at 2015 hours0.0233 days <br />0.56 hours <br />0.00333 weeks <br />7.667075e-4 months <br />, while operating at approximately eight percent power in the run mode following the BFN Unit 2 refueling outage, the Number 2 mechanical seal for the 2A Reactor Recirculation pump failed and the pump was removed from service. The Limiting Condition for Operation for Technical Specification 3.6.F.1 (TS) was entered which requires the plant be placed in a hot shutdown condition within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> after taking one recirculation loop out of service. At 2225, an orderly plant shutdown was initiated in accordance with TS requirements. On May 28, at 0140, plant shutdown was completed in an orderly manner. This event is being reported in accordance with 10 CFR 50.73(a)(2)(i)(A) as a condition that resulted in manual shutdown of the plant required by the plant's TS.

The root cause of the recirculation pump seal failure was due to inadequate procedures. An investigation of this event determined that the pump seal failed due to a small amount of loose particles (e.g., welding related material) collecting in the seal spring packing assembly causing the spring to jam and the seal not to seat properly. To prevent this problem from recurring, TVA revised site procedures before to require seal purge flow to be established, to supply water to the seal cavity opening the recirculation pump isolation valves following maintenance activities.

NRC Form 366(6-89)

~I NRC Form 366A U.S. NUCLEAR REGULATORY COMMISSION Approved OHB No. 3150-0104 (6-89) Expires 4/30/92 LICENSEE EVENT REPORT (LER)

TEXT CONTINUATION FACIL'ITY NAME (1) IDOCKET NUMBER (2)

I I I I SEQUENTIAL I I REVI S ION I I I I I Browns Ferry Uni t 2 I 8 I I I I TEXT (If more space is required, use additional NRC Form 366A's) (17)

I. PLANT CONDITIONS Unit 2 was in the run mode at approximately eight percent power following the Cycle 6 refueling outage. Units 1 and 3 were shutdown and in a defueled condition.

II- DESCRIPTION OF EVENT A. ~~at:

On May 27', 1993, Operations personnel in the control room received indication of an abnormal seal pressure on the 2A recirculation [AD]

pump's number 2 seal. An inspection team entered the drywell at 1945 to check the recirculation pump seal alarm and to check for leakage. While the inspection team was in the drywell, the number 2 seal on the 2A recirculation pump started leaking excessively (approximately 5 gpm).

Control room personnel were notified at 2013 of the leaking seal. At 2015 the 2A Reactor Recirculation System pump was removed from service and Technical Specification (TS) Limiting Condition for Operation (LCO) 3.6.F.l was entered. This TS section requires the plant be placed in a hot shutdown condition within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> after taking one recirculation loop out of service.

At 2225, an orderly plant shutdown was initiated in accordance with TS 3.6.F.l. Since replacement of the recirculation pump seal could not be performed within the TS LCO, Unit 2 was shutdown and an Unusual Event (UE) was declared. On May 28, at 0140, the UE was terminated after all control rods were inserted and the mode switch was placed in the shutdown position.

Subsequent investigation by TVA and representatives from the recirculation pump manufacturer determined that the cause of the seal leak was due to small particles in the recirculation system inhibiting the pump seal spring assembly.

This event is being reported in accordance with 10 CFR 50.73(a)(2)(i)(A) due to the completion of plant shutdown required by TS requirements.

NRC Form 366(6-'89)

I J

NRC Form 366A U. . NUCLEAR REGULATORY COHHISSION Approved OHB No. 3150-0104 (6-89) Expires 4/30/92 LICENSEE EVENT REPORT (LER)

TEXT CONTINUATION FACILITY NAHE (1) IOOCKET. NUHBER (2)

I ISE()UENTIAL I IREYISIONI I I I I Browns Ferry Uni t 2 I I I I I F

TEXT (If more space is required, use additiona1 NRC Form 366A's) (17)

B. Ia t t t t t t t h None.

C.

May 27, 1993, at 2015 CDT 2A Reactor Recirculation System pump removed from service due to seal leakage and entered 24-hour LCO.

May 27, 1993, at 2225 CDT Initiated shutdown of Unit 2 reactor to cold shutdown, declared UE, and notified NRC within one hour of event in-accordance with 10 CFR 50.72(a)(3) and 50.72(b)(l)(i)(A).

May 28, 1993, at 0140 CDT UE terminated after all control rods were inserted and mode switch placed in shutdown'osition.

D. th None.

E 'h V e Abnormal Reactor Recirculation System. pump seal pressure indication in the control room alerted Operations personnel.

Operations personnel responded to the abnormal Reactor Recirculation System pump seal pressure indication by sending an inspection team into the drywell to check the pump seal alarm and for any seal leakage. Unit 2 was shutdown in an orderly fashion, due to the 2A Reactor Recirculation System pump's number 2 seal leaking excessively, as required by the plant's TS.

G.

None.

NRC Form 366(6-89)

0 C

NRC Form'366A U.. NUCLEAR REGULATORY COMMISSION Approved OMB No. 3150-0104 (6-89) Expires 4/30/92

'LICENSEE EVENT REPORT (LER)

TEXT CONTINUATION FACILITY NAME (1) (OOCKET,NUMBER (2) PA I i SE()VENT IAL i i REVISION (

Browns Ferry Uni t 2 I I I I I TEXT (If more space is required, use additional NRC Form 366A's) (17)

III. CAUSE OF THE EVENT The immediate cause of the event was excessive leakage past the 2A Reactor Recirculation System pump mechanical seal.

B. @~tstgI~:

The root cause of the event was inadequate procedures. Specifically, plant procedures failed to require seal purge flow to be established, prior to restarting the recirculation pumps, to supply water to the seal cavity prior to opening the recirculation pump isolation valves following maintenance activities. Opening the recirculation pump valves prior to establishing seal purge flow allowed small particles to enter the seal spring assembly, which resulted in the pump seal leakage.

An investigation performed by TVA and vendor personnel subsequent to the event determined that the pump seal failed due to a small amount of loose particles collecting in the seal spring packing assembly causing the spring to jam. The function of the seal spring packing assembly is to hold, the rotating face and carbon stationary face of the seal together.

Very small amounts of debris in the spring assembly will cause the assembly to-malfunction. Jamming of the spring assembly caused the seal not to seat properly, which resulted in the excessive leakage.

The loose particles collected from the seal assembly were sent to Southwest .Research Laboratory for material characterization. The laboratory results indicated that the average size of the particles was

.008 square inches. The particle sizes ranged from .02 to .0016 square inches. The particles were determined to be weld related materials (i.e.,

iron particles and slag).

C.

The reactor vessel piping decontamination activities disturbed existing particles in the Reactor Recirculation System during the Unit 2, Cycle 6 refueling outage. The age and the origin of these particles are not known.

NRC Form 366(6-89)

~i NRC Form 366A U.. NUCLEAR REGULATORY COHHISSION Approved OHB No. 3150-0104 (6-09) Expires 4/30/92 LICENSEE EVENT REPORT (LER)

TEXT CONTINUATION FACILITY NAME -(1) IDOCKET NUHBER (2)

I I I I SEqUENTIAL I I REVISIONI I I I I Browns Ferry Unit 2 I A I I I I TEXT (If more space is required, use additional NRC Form 366A's) (17)

C IV. ANALYSIS OF THE EVENT This event occurred with Unit 2 in the run mode at approximately eight percent power following the BFN Unit 2 refueling outage. Units 1 and 3 were shutdown and in a defueled condition.

Drywell leakage increased and the seal pressure equalized across the two stages, alerting the operators of a recirculation pump seal malfunction. The pump leakage was calculated to be approximately 5.66 gpm during the shutdown process.'he seal construction is such that even during catastrophic seal failure, the maximum leakage is limited to approximately 60 gpm by the breakdown bushing with minimal impact on the containment pressure. At no time during the event was any safety system challenged. No safety consequences resulted from the event, since the affected systems responded properly to perform their intended safety functions. Therefore, the plant and the public safety was not adversely affected and the safety of the plant personnel was not compromised. The mode switch was placed in "Shutdown" on May 28, 1993, at 0140 hours0.00162 days <br />0.0389 hours <br />2.314815e-4 weeks <br />5.327e-5 months <br /> and the condition of cold shutdown was achieved.

V. CORRECTIVE ACTIONS tv t

'TVA personnel and representatives from the recirculation pump manufacturer disassembled the pump seal and inspected the mechanical seal assembly to determine cause of the leakage.

B. tv At t TVA revised Operation Instruction 2-0I-68, "Reactor Recirculation System" to require seal purge flow to be established, prior to restarting the recircul'ation pump, to supply water to the seal cavity before opening the recirculation pump isolation valves following maintenance activities.

Specifically, this revision requires that CRD purge flow be turned on before the suction or discharge valves are opened after any maintenance that requires draining the pump cavity. Maintenance Instruction MCI-068-PMP001, "Maintenance of Reactor Recirculation Pumps," was revised to require seal flow to be on following seal maintenance activities before the suction or discharge valves are opened. These procedure requirements will prevent the loose particles from collecting in the pump seal spring assembly.

NRC Form 366(6-89)

0 NRC Form 366A U.. NUCLEAR REGULATORY COHHISSION Approved OHB No. 3150-0104 (6-09) Expires 4/30/92 LICENSEE EVENT REPORT (LER)

TEXT CONTINUATION FACILITY NAHE (1) iDOCKET NUHBER (2)

I I, I I SEQUENTIAL I REVIS ION I I I I I Browns Ferry Uni t 2 I Y I I I I TEXT (If more space is required, use additional NRC Form 366A's) (17)

VI. ADDITIONAL INFORMATION 2A seal spring holder assembly.

B. v None.

VII. COMMIXNEHTS None.

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

NRC Form 366(6-09)

r 4