ML17289A602

LER 92-020-00:on 920509,review of Plant Determined That Problems Associated W/Sys Minimum Flow Control Instruments Were Repetitive & Challenge Sys Operability.Caused by Poor Plant Construction.Plant Procedures modified.W/920605 Ltr

ML17289A602
Person / Time
Site:	Columbia
Issue date:	06/05/1992
From:	John Baker, Imel J WASHINGTON PUBLIC POWER SUPPLY SYSTEM
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
GO2-92-137, LER-92-020, LER-92-20, NUDOCS 9206110209
Download: ML17289A602 (8)

Text

TION SYSTEM REGULATORY INFORMATION DISTRIBUTION SYSTEM (RIDS)ACCESSION NBR:9206110209 DOC.DATE: 92/06/05 NOTARIZED:

NO FACIL:50-397 WPPSS Nuclear Project, Unit 2, Washington Public Powe AUTH.NAME AUTHOR AFFILIATION IMEL,J.D.Washington Public Power Supply System BAKER,J.W.

Washington Public Power Supply System'ECIP.NAME RECIPIENT AFFILIATION

.DOCKET¹05000397

SUBJECT:

LER 92-020-00:on 920509,review of plant determined that problems associated w/sys minimum flow control instruments were repetitive

&challenge sys operability.

Caused by poor plant construction.

Plant procedures modified.W/920605 ltr.4 DISTRIBUTION CODE: IE22T COPIES RECEIVED:LTR ENCL SIZE: TITLE: 50.73/50.9 Licensee Event Report (LER), ncident Rpt, etc.NOTES: RECIPIENT ID CODE/NAME PD5 LA DEAN,W.INTERNAL: ACNW AEOD/DOA AEOD/ROAB/DSP NRR/DLPQ/LHFB1 0 NRR/DOEA/OEAB NRR/DST/SELB 8D~D+g-LB8Dl EG FILE 02 RGN E 01 EXTERNAL: EG&G BRYCE,J.H NRC PDR NSIC POORE,W.COPIES LTTR ENCL 1 1 1 1 2 2 1 1 2 2 1 1 1 1 1 1 1 1 1 1, 1 1 3 3 1 1 1 1 RECIPIENT ID CODE/NAME PD5 PD ACRS AEOD/DSP/TPAB NRR/DET/EMEB 7E NRR/DLPQ/LPEB10 NRR/DREP/PRPBll NRR/DST/SICB8H3 NRR/DST/SRXB 8E RES/DSIR/EIB L ST LOBBY WARD NSIC MURPHY,G.A NUDOCS FULL TXT COPIES LTTR ENCL 1 1 2 2 1.1 1 1 1 1 2 2 1 1 1 1 1, 1 1 1 1 1 1 1~/v~pviyap 7iS/NOTE TO ALL"RIDS" RECIPIENTS:

PLEASE HELP US TO REDUCE WASTE!CONTACT THE DOCUMENT CONTROL DESK, ROOihi Pl-37 (EXT.20079)TO ELIMINATE YOUR NAME FROM DISTRIBUTION LISTS FOR DOCUMENTS YOU DON'T NEED!FULL TEXT CONVERSION REQUIRED TOTAL NUMBER OF COPIES REQUIRED: LTTR 32 ENCL 32

~ai WASHINGTON PUBLIC POWER SUPPLY SYSTEM P.O.Box 968~3000 George Washington Way~Richland, Washington 99352 June 5, 1992 G02-92-137 Docket No.50-397 Document Control Desk U.S.Nuclear Regulatory Commission Washington, D.C.20555

SUBJECT:

NUCLEAR PLANT WNP-2, OPERATING LICENSE NPF-21 LICENSEE EVENT REPORT NO.92-20 Transmitted herewith is Licensee Event Report No, 92-20 for the WNP-2 Plant.This report is submitted in response to the report requirements of 10CFR50.73 and discusses the items of reportability', corrective action taken, and action taken to preclude recurrence., Sincerely, J.W.Baker WNP-2 Plant Manager (Mail Drop 927M)Enclosure CC: Mr.John B.Martin, NRC-Region V Mr.C.Sorensen, NRC Resident Inspector (Mail Drop 901A, 2 Copies)INPO Records Center-Atlanta, GA Mr.D.L.Williams, BPA (Mail Drop 399)cyP0bgg0209 q20b05 pDp*QOCK PD~6 I 1 LlcENsEE EVEN4hPQRT (LER)AGILITY HAHE (1)Washington Nuclear Plant-Unit 2 T UHBR()PAGE (3)0 5 0 0 0 3 9 7 I OF ITLE (4)FLOW ELEMENT FOR LOW PRESSURE CORE SPRAY (LPCS)MINIMUM FLOW CONTROL NOT PROPERLY INSTALLED EVENT DATE 5)HONTH DAY YEAR YEAR LER HUHBER 6)SEQUENTIAL NUHBER EV I SION UHBER OTHER FACILITIES INVOLVED (8)REPORT DATE 7 YEAR FACILITY NAHES HONTH DAY HUHB RS(S)0 5 0 8 9 2 9 2 0 2 0 0 0 0 6 0 4 9 2 5 0 0 0 5 0 0 0 P ERAT IHG ODE (9)HIS REPORT IS SUBHITTED PURSUANT TO THE REQUIRENEHTS OF 10CFR E: (Check one or more of the following (ll)5 OWER LEVEL (10)0.402(b)0.405(a)(1)(i) 0.405(a)(l)(ii) 0.405(a)(1)(i i i)0.405(a)(1)(iv) 0.405(a)(1)(v) 0.405(C)0.36(c)(1) 0.36(c)(2) 0.73(a)(2)(i) 50.73(a)(2)(ii) 50.73(a)(2)(iii) 0.73(a)(2)(iv) 0.73(a)(2)(v) 0.73(a)(2)(vii) 0.73(a)(2)(viii)(A) 0.73(a)(2)(viii)(B) 0.73(a)(2)(x) 7.71(b)3.73(c)THER (Specify in Abstract elow and in Text, HRC orm 366A)LICENSEE COHTACT FOR THIS LER (12)J.D.Imel, Nuclear Engineer REA CODE TELEPHOHE NUHBER 0 9 7 7-2 2 9 5 COHPLETE OHE LINE FOR EACH COHPDHEHT FAILURE DESCRIBED IH THIS REPORT ('13)CAUSE SYSTEH COHPDHEHT HAHUFACTURER EPORTABLE 0 HPRDS c'<<.CAUSE SYSTEH COHPOHEHT r HAHUFACTURER EPORTABLE TO HPRDS SUPPLEHEHTAL REPORT EXPECTED (14)YES (If yes, carpiete EXPECTED SUBHISSION DATE)HO TRACT Ild)XPECTED SUBHISSIOH HOHTH DAY YEAR ATE (15)On May 5, 1992, it was determined that problems associated with the system minimum Qow control instruments were repetitive and challenged system operability.

Between December 1991 and April 1992, several instances were identified where the Qow indicating switch (which controls the minimum Qow valve).read onscale when the system was shutdown.Corrective actions initiated on these occasions had been ineffective in permanently resolving the problem.The root cause of this event is that the Qow element LPCS-FE-002 was not installed properly during Plant construction due to poor work practices.

This il)stallation allowed air to be entrained in sensing lines during pump operation, giving erroneously high readings which could have resulted in premature closing or failure to open of the minimum Qow valve.Plant procedures were modified to include a check of the instrument status prior to running the pump.Instrument sensing line taps-for LPCS-FE-002 will be modified, prior to returning the system to an operable status, to eliminate trapping gas bubbles in the instrument lines.The details of this event were communicated to all system engineers and Instrumentation and Control technicians and engineers.

Walk downs of other safety systems, prior to Plant restart from the current maintenance and refueling outage, will ensure no similar problems exist.

.LICENSEE EVENT REPORT~)TEXT CONTINUATION

~ACILITY NAHE (I)Mashlngton Nuclear Plant-Unit 2 OOCKET HUHBER (2)0 5 0 0 0 3 9 7 LER HUHBER (8)ear umber ev.No.2 2 0 0 AGE (3)2 F 5 ITLE (4)FLOW ELEMENT FOR LOW PRESSURE CORE SPRAY (LPCS)MINIMUM FLOW CONTROL NOT PROPERLY INSTALLED The LPCS system starts automaticany on a low reactor level or high drywell pressure.The pump is designed to run on minimum fiow until reactor pressure is low enough that injection can occur.Indication of minimum Qow valve position is available to the control room operator.The LPCS pump can be stopped if required due to this condition, and restarted from the'control room when reactor pressure is low enough for injection to occur.Multiple other low and high pressure safety related systems are available to supply core cooling.This event had minimal safety sigmficance.

There were no structures, systems, or components inoperable prior to the start of this event that contributed to the event.Plant n i i n Power Level-0%Plant Mode-5 (Refueling) vnD ri in On May 5, 1992,'it was determined from a review of completed work packages that problems associated with the system minimum fiow control instrument, LPCS-FIS-4, were repetitive and challenged system operability.

The system was inoperable for maintenance and testing at the time of discovery.

Between December 1991 and April 1992, several instances were identified where the Qow indicating switch (which controls the minimum fiow valve)read onscale when the system was shutdown.Corrective actions, refilling the instrument lines and verifying instrument calibration, initiated on these occasions had been ineffective in permanently resolving the problem.A Problem Evaluation Request (PER)was initiated to resolve this repetitive problem.Imm i iv A in The immediate corrective action was to change the surveillance procedure, PPM 7.4.5.1.7, and.the system operating procedure, PPM 2.4.3, to check LPCS-FIS-004 and verify proper indication after each operation of the LPCS pump.This action will remain in effect until completion of the final corrective action.hrEv in rr iv i n A.h Ev in It has been determined that, due to the physical installation of the instrument sensing line taps, air enters the instrument low pressure sensing line'when the pump is operated.LPCS-FIS-4 sends its signal to the minimum fiow valve, LPCS-FCV-11, to close it when system fiow is a770 gpm and to reopen it on low fiow conditions.

This protects the pump from potential damage due to extended

.LICENSEE EVENT REPORT ()TEXT, CONTINUATION ACILITY HANE (I)Mashington Huclear Plant'-Unit 2 KET HUHBER (2)0 5 0 0 0 3 9 7 LER HUHBER (8)ear umber ev.Ho.2 2 0 0 AGE (3)3 F 5 ITLE (4)FLOW ELEMENT FOR LOW PRESSURE CORE SPRAY (LPCS)MINIMUM FLOW CONTROL NOT PROPERLY INSTALLED operation at low fiow conditions.

Yable 3.3.3-2 of the Plant Technical Specifications specifies the-trip set point for the LPCS Pump Discharge Flow-Low (Minimum Flow)be M770 gpm with an allowable value of~900 gpm.In the event that LPCS-FIS-004 erroneously reads some high value, say 400 gpm, then the trip point of this switch could be as low as 370 gpm actual fiow., This would be a violation of the Technical Specification.

This lower setpoint would be conservative in regards to providing fiow to the reactor in the case of a design basis event since the minimum fiow valve would close sooner, resulting in greater injection fiow.However, this could lead to failure of the LPCS pump in the event the pump had to run for an extended period of time before reactor pressure was low enough to allow admission of LPCS fiow.If LPCS-FIS-004 is sensing fiow when there is none, the minimum Bow valve could close with an actual system fiow of less than 770 gpm.Technical Specifications require the valve be open to ensure LPCS pump fiow is>770 gpm.This is a condition prohibited by the Technical Specifications and is reportable pursuant to the requirements of 10CFR50.73(a)(2)(i)(B).

There were no structures, systems, or components inoperable prior to the start of this event that contributed to the event.The root causes for this event include: 1)fiow element LPCS-FE-002 was not installed properly during construction of the Plant due to poor work practices; and 2)The timeliness of resolving this installation weakness was poor in that the policy for ensuring that problems are reported to the appropriate level of management for consideration and correction was not enforced.This problem is caused by the differential pressure switch sensing lines being connected to the fiow element (LPCS-FE-002) in an incorrect configuration.

The vendor manual for LPCS-FIS.-004 specified the tubing come off the side, instead of the top, of the main piping.This limits air collection in the instrument lines.The first time this condition was identified was November 15, 1983, when it was recorded in the Instrumentation and Control Chronological History Sheet.In 1983, this problem was not brought to managements attention through a startup problem report and was thus not addressed at that time.When the LPCS pump is run, gas bubbles may gather in the sensing lines to LPCS-FIS-004 and LPCS-FT-003.

LPCS-FIS-004 spans 0 to 1100 gpm fiow with a change of 10 inches water column differential pressure.The control room indicator transmitter, LPCS-FT-003, spans 0 to 607.5 inches water column difFerential pressure for 0 to 8500 gpm Qow.The effect of an observed 2 inches water column difference is that the control room indicator would read an acceptable value (approximately zero), whereas local LPCS-FIS-004 would indicate a value of approximately 475 gpm.

V

.LICENSEE EVENT REPORT ()TEXT CONTINUATION

~AGILITY NANE (I)"'ashington Nuclear Plant-Unit 2 ET NURSER (2)0'0 0 0 3 9 7 LER NUHBER (8)ear'mber ev.No.2 2 0 0 AGE (3)4 F 5 ITLE (4)FLOW ELEHENT FOR LOW PRESSURE CORE SPRAY (LPCS)HINIHUH FLOW CONTROL NOT PROPERLY INSTALLED The LPCS pump is run quarterly, while the Qow indicating switch is checked monthly by surveillance procedure PPM 7.4.3.3.1.6.

The LPCS system, including the instrument lines, is filled and vented each time the system is drained.This problem may have previously gone undetected since the calibration and channel functional testing of LPCS-FIS-004 involves isolation of the instrument from the system.The condition would therefore not have been immediately observable to the test personnel.

B.F her rrective Ac ionThe in'strument sensing lines taps on LPCS-FE-002 will be modified to eliminate the problem of trapping gas bubbles in the instrument lines.This action will be completed by 6/15/92.A memorandum was issued to all system engineers and Instrumentation and Control Technicians on systems containing Qow orifices.The memorandum notified them to be alert for potential improper orientation of the Qow elements sensing line taps or improper routing or sloping of instrument lines that could cause problems with the Qow readings.System Engineers for the ECCS Systems, will perform walk downs on these systems looking for improper orientation of Qow element sensing line taps.This action will be completed by June 22, 1992.Management expectations regarding use of the problem reporting system were provided in two recent memorandums from the Plant Manager.fe i nifi This event resulted in a small chance of damaging the LPCS pump due to low Qow during system operation.

To have damage a combinations of events would have been necessary.

Enough air had to be trapped in the Qow sensing line to cause closure of the minimum Qow valve when injection Qow was still low enough to cause pump damage.Finally, LPCS would have had to start in response to an accident event and reactor pressure remained high enough that LPCS injection did not occur.This particular problem would not effect the performance of other emergency core cooling systems such as High Pressure Core Spray (HPCS), Reactor Core Isolation Cooling (RCIC), and three divisions of the Low Pressure Core Injection (LPCI)mode of Residual Heat Removal (RHR)operation.

These systems are capable of providing emergency'core cooling without LPCS.Consequently, the designed system redundancy ensures there was minimal safety significance due to the inaccuracy of LPCS-FIS-004.

.LICENSEE EVENT REPORT (I+i)TEXT CONTINUATION AGILITY HAHE (I Mashfngton kuclear Plant-Unft 2 00CrET kUHBER (2)0 5 0 0 0 3 9 7 LER HUHBER (8)ear umber ev.ko.2 2 0 0 AGE (3)5 F 5 ITLE (4)FLOW ELEMENT FOR LOW PRESSURE CORE SPRAY (LPCS)MINIMUM.FLOW CONTROL NOT PROPERLY INSTALLED i ilr v There have been no past events at WNP-2 where improper installation of differential pressure switch sensing lines resulted in air entrainment inoperability of the associated instruments.

Infrm in x Rfrn IIHHRf a$ygem Q~m~n~n Low Pressure Core Spray (LPCS)LPCS Flow Indicating Switch (LPCS-FIS-004)

LPCS Flow Orifice (LPCS-FE-002)

LPCSS Minimum Flow Valve (LPCS-FCV-11)

LPCSS Pump (LPCS-P-1)

High Pressure Core Spray{HPCS)Residual Heat Removal (RHR)BM BM BM BM BM BG BO FIS OR V P