ML17289B101

LER 92-044-00:on 921208,HPCS Sys Pump Suction Valve Switchover Occurred,Due to Spurious Actuation of Either One or Both CST Pipe Break Detectors.Engineering Will Evaluate Replacement of Detectors & Alternate design.W/930106 Ltr

ML17289B101
Person / Time
Site:	Columbia
Issue date:	12/30/1992
From:	John Baker, Mackaman C WASHINGTON PUBLIC POWER SUPPLY SYSTEM
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
GO2-93-004, GO2-93-4, LER-92-044, LER-92-44, NUDOCS 9301120163
Download: ML17289B101 (7)

Text

QCCELEIUlT+ DOCUMENT DISTIIUTIONSYSTEM REGULAT INFORMATION DISTRIBUTIO STEM (RIDS)

ACCESSION NBR:9301120163 DOC.DATE: 92/12/30 NOTARIZED: NO DOCKET

, FAC3L:50-397 WPPSS Nuclear Project, Unit 2, Washington Public Powe 05000397 A0'EH.NAME 'UTHOR AFFILIATION MACKAMAN,C.D. Washington Public Power Supply System BAKER,J.W. Washington Public Power Supply System RECIP.NAME RECIPIENT AFFILIATION R

SUBJECT:

LER 92-044-00:on 921208,HPCS sys pump suction valve switchover occurred,due to spurious actuation of either one or both CST pipe break detectors. Engineering will evaluate replacement of detectors a alternate design.W/930106 ltr.

DISTRIBUTION CODE: IE22T COPIES RECEIVED:LTR ENCL SIZE:

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

NOTES:

A RECIPIENT COPIES RECIPIENT COPIES ID CODE/NAME LTTR ENCL ID CODE/NAME LTTR ENCL D PD5 LA 1 1 PD5 PD 1 1 CLIFFORD,J 1 1 D INTERNAL: ACNW 2 2 ACRS 2 2 AEOD/DOA 1 1 AEOD/DSP/TPAB 1 "

1 AEOD/ROAB/DSP 2 2 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 1 1 NRR J3 ./SPLS8D1 1 1 NRR/DST/SRXB 8E 1 1 EG FZL 02 '1 1 RES/DSIR/EIB 1 1 GR5 FILE 01 1 1 EXTERNAL EG&G BRYCE F J ~ H 2 2 L ST LOBBY WARD 1 1 NRC PDR 1 1 NSIC MURPHYFG.A 1 1 NSIC POORE,W. 1 1 NUDOCS FULL TXT 1 1

'D D

D NOTE TQ ALL"RIDS" RECIPIENTS:

PLEASE HELP US TQ REDUCE WASTEI CONTACT THE DOCUMENT CONTROL DESK, ROOM Pl-37 (EXT. 504-2065) TQ ELIMINATEYOUR NAME FROM DISTRIBUTION LISTS FOR DOCUMENTS YQU DON'T NEEDI FULL TEXT CONVERSION REQUIRED TOTAL NUMBER OF COPIES REQUIRED: LTTR 31 ENCL 31

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WASHINGTON PUBLIC POWER SUPPLY SYSTEM P.O. Box 968 ~ 3000 George Washington Way ~ Richland, Washington 99352 January 6, 1993 G02-93-004 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.92-044 Transmitted herewith is Licensee Event Report No.92-044 for the WNP-2 Plant. This report is submitted in response to the report requirements of 10CFR 50.73 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)

JWB/CDM/cgeh Enclosure CC: Mr. J. B. Martin, NRC - Region V Mr. R. Barr, NRC Resident Inspector (Mail Drop 901A, 2 Copies)

INPO Records Center - Atlanta, GA Mr, D, L. Williams, BPA (Mail Drop 399)

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~prPJ 930ii20i63 92123005000397 PDR ADOCK S PDR

LICENSEE EVE REPORT (LER)

FACILITY NAME (1) OCKET NUHBER (2) AGE (3)

Washin ton Nuclear Plant Unit 2 DIS IOIOIDI3I9I7 1 OF 5 ITLE (4)

HIGH PRESSURE CORE SPRAY (HPCS) SYSTEM PUMP SUCTION VALVEAUTOMATIC SWITCHOVER ACTUATION EVENT DATE (5) LER NUHBER (6) REPORT DATE (7) OTHER FACILITIES INVOLVED (B)

HONTH DAY YEAR YEAR SEQUENTIAL EVI SION HOHTH DAY YEAR FACILITY NAMES OCKET NUHBERS(S)

'$:R UMBER UMBER l5lplplpl I I 1I 2 Ols . I2 9I2- 0 I 4 I 4 olo . 1I2 3lo 912 l5lplplpl I I E RATING HIS REPORT IS SUBHITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR 5: (Check one or more of the folloMing) (11)

ODE (9) 1 OMER LEVEL 0.402(b) 0 ~ 405(C) 0.73(a)(2)(iv) .7'I (b)

(10) 0.405(a)(1)(i) 0.36(c)(1) 0.73(a)(2)(v) .73(c) 0.405(a)(1)(ii) 0.36(c)(2) 0.73(a)(2)(vii) THER (Specify in Abstract 0.405(a)(1)(iii) 0.73(a)(2)(i) 0.73(a)(2)(viii)(A) ioH and in Text, NRC 0.405(a)(1)(iv) 0.73(a)(2)(ii) 0.73(a)(2)(viii)(B) Form 366A) 0.405(a)(1)(v) 0.73(a)(2)(iii) 0 '3(a)(2)(x)

LICENSEE CONTACT FOR THIS LER (12)

TELEPHONE NUHBER C. D. Mackaman, Compliance Engineer REA CODE I p I 9 I 7 I 7 I - I 4 I 1 I 5 I 5 COMPLETE ONE LINE FOR EACH COMPONENT FAILURE DESCRIBED IN THIS REPORT (13)

CAUSE SYSTEH COMPONENT MANUFACTURER EPORTABLE P<$)i';,."). CAUSE SYSTEH COHPONEHT HANUFACTURER EPORTABLE )~,",?'j,";.

0 NPRDS TO NPRDS I I I I I I I I I I I I I I I I I I I I I I I I I I I I SUPPLEMEN'TAL REPORT EXPECTED (14) EXPECTED SUBMISSION HOHTH DAY YEAR ATE (15)

I YES ( If yes, complete EXPECTED SUBMISSION DATE) XI NO TRAGT os)

At 00:41 on December 8, 1992, with the Plant operating at 100% power, a High Pressure Core Spray (HPCS) System pump suction valve switchover occurred. The switchover actuation consists of the automatic closure of Condensate Storage Tank Suction Valve HPCS-V-1, and the opening of Suppression Pool Suction Valve HPCS-V-15.

At the time of the suction valve switchover, the Plant Control Room Operators received a momentary "HPCS SUCTION SWITCHOVER CST LEVEL LOW" annunciator. The closure of HPCS-V-1 and opening of HPCS-V-15 was by Plant design. After verifying that no actual high Suppression Pool or low-Condensate Storage Tank Level condition existed, the Plant Control Room Operators restored the system to the pre-event line-up as an immediate corrective'action at 01:12.,

The root cause of this event is indeterminate. However, it is suspected that the cause was the spurious actuation of either one or both Condensate Storage Tank pipe break detectors (HPCS-LS-3A/3B). The detectors were found with excessive setpoint drift, and may be susceptible to radio frequency interference (RFI). As corrective actions, the interval for calibration of HPCS-LS-3A/3B will be reduced from 18 months to one month to limit the setpoint drift. In addition, Engineering will evaluate replacement of the existing detectors with an alternative design to eliminate the setpoint drift. Maintenance will investigate the susceptibility of the detectors to RFI.

This event posed no th'reat to the health and safety of either the public or Plant personnel.

\

LICENSEE EVENT REPORT R)

TEXT CONTINUATION AGILITY NAHE (1) OOCKET NUHBER (2) LER NUHBER (8) AGE (3) ear umber ev. No.

Washington Nuclear Plant - Unit 2 0 5 0 0 0 3 9 7 2 4 4 0 2 F 5 ITLE (4)

HIGH PRESSURE CORE SPRAY (HPCS) SYSTEM PUMP SUCTION VALVE= AUTOMATIC SWITCHOVER ACTUATION Power Level - 100%

Plant Mode - 1 (Power)

Even D ri in r

At 09:41 on December 8, 1992, with the Plant operating in Mode 1 at 100% power, a High Pressure Core Spray (HPCS) System pump suction valve switchover occurred. The Plant configuration at the time was, such that the HPCS pump suction was lined up to the Condensate Storage Tanks, with suction valve HPCS-V-1 opep (the normal line-up) and Suppression Pool Suction Valve HPCS-V=15 closed. The switchover actuation was the automatic closure of HPCS-V-1 and the opening of HPCS-V-15.

At the time of the suction valve switchover, a momentary "HPCS SUCTION SWITCHOVER CST LEVEL LOW" alarm was received by the Plant Control Room Operators. The alarm duration was very brief and,

~

cleared immediately, with no operator action. Although the switchover was unexpected, the closure of HPCS-V-1 and the opening of HPCS-V-15 was by Plant design. Initial investigation by the Operations crew was to validate the alarm. Review of the computer data for the Condensate Storage Tank and Suppression Pool levels indicated that both levels were within their acceptable bands, with no apparent level peiturbations or trends; The Control Room Supervisor then dispatched an Equipment Operator to the level switches to determine the cause of the alarm. The Equipment Operator could not find any abnormal conditions, nor did there appear to be any ongoing maintenance or other activities in the area.

With the Condensate Storage Tank and Suppression Pool levels verified within their acceptable bands, the Plant Control Room Operators restored the HPCS system to the pre-event line-up (HPCS-V-15 was closed and HPCS-V-1 was re-opened) at 01:12.

In accordance with 10CFR 50.72(b)(2)(ii), this event was reported as an unplanned automatic ESF actuation 'o the NRC Operations Center via the Emergency Notification System at 01:26 on December 8, 1992.

Immedi rrec iv Ac i n Plant Control Room Operators realigned the HPCS pump suction valves to the normal pre-event line-up.

rther Ev luation and rrec iv Action F~FI!

This event is reportable under 10CFR 50.73(a)(2)(iv) as an event or condition that resulted in manual 'or automatic actuation of any Engineered Safety Feature.

ICENSEE EVENT REPORT R)

TEXT CONTINUATION AGILITY NAME (1) OOCKET NUMBER (2) LER NUMBER (8) AGE (3) ear umber ev. No.

Washington Nuclear Plant - Unit 2 0 5 0 0 0 3 9 7 2 44 0 3 F 5 ITLE (4)

HIGH PRESSURE CORE SPRAY (HPCS) SYSTEM PUMP SUCTION VAI.VE AUTOMATIC SWITCHOVER

'CTUATION There were no structures, systems or components that were inoperable at the start, of this event that contributed to the event.

The "HPCS SUCTION SWITCHOVER CST LEVEL LOW" alarm and associated HPCS pump suction valve switchover circuitry are actuated by two Condensate Storage Tank low level switches (HPCS-LS-1A/1B) and two pipe break detectors (HPCS-LS-3A/3B) arranged in a one-out-of-one logic. The. input from level switches HPCS-LS-1A/1B comes from two Magnetrol float switches, and the input from pipe break detectors HPCS-LS-3A/3B comes from two Fluid Components Incorporated (FCI) solid state electronic fluid flow, detectors.

Post event calibration of HPCS-LS-1A/1B and HPCS-LS-3A/3B found HPCS-LS-lA & 1B to be within their normal calibration trip setpoint tolerances, requiring no adjustments. However, both HPCS-LS-3A A 3B were found to have drifted,out of their normal calibration trip setpoint tolerances, requiring adjustments. HPCS-LS-3A had drifted +33.75% (toward the trip setpoint) and HPCS-LS-3B had drifted -46.25% (away from the 'trip setpoint). The normal calibration tolerance is

+0/-12.5%. The trip setpoint drift of +33.75% meant that only a 53 millivoltsignal would be required to cause HPCS-LS-3A to trip. This fact, and previous experience with field located solid state electronic components, prompted investigators to suspect that the actual mechanism for the actuation was a lower than normal trip setpoint, in conjunction with RFI from a portable 'purious radio transmission in the area of the FCI detectors. Although no one was found in the area with a radio during the initial investigation by Operations, the susceptibility of the detectors to RFI will be further investigated. A supplemental LER will be submitted if the investigation provides conclusive evidence that RFI was the root cause.

A historical search was conducted to determine setpoint drift values for HPCS-LS-3A/3B during calibration intervals preceding this event. The only data available was for the intervals, from the setpoint change calibration on September 8, 1991 to April 7, 1992, and April 7, 1992 to the post event calibration of December 8, 1992. Prior to this time PPM 10.27.23 did not require the "as found" data to be recorded. During the first seven month period, HPCS-LS-3A had drifted

+11.25% and HPCS-LS-3B had drifted +68.75%, and during the subsequent eight month period, HPCS-LS-3A had drifted +33.25% and HPCS-LS-3B had drifted -46.25%. From this data it was concluded that the excessive setpoint drift is a recurring problem that should be resolved by Engineering, and the normal calibration interval of 18 months should be shortened to one month to limit the setpoint drift. The calibration interval may be extended after three months based upon evaluation of the monthly setpoint drift values.

The Root Cause for this event is indeterminate since a formal root cause analysis failed to provide a conclusive root cause for the HPCS pump suction valve switchover actuation.

L'ICENSEE EVENT REPORT ER)

TEXT CONTINUATION AGILITY NAHE (1) DOCKET NUNBER (2) LER NUMBER (B) AGE (3) ear unbent ev. No.

Washington Nuclear Plant - Unit 2 3

0 5 0 0 0 9 7 2 44 0 4 F 5 ITLE (4)

HIGH PRESSURE CORE SPRAY (HPCS) SYSTEM PUMP SUCTION VALVE AUTOMATIC SWITCHOVER

. ACTUATION her rr v A 'n

1. Reduce the interval for calibration of HPCS-LS-3A/3B from 18 months to one month. This will be completed by January 31, 1993. After three months at the monthly interval, Technical Staff will evaluate increasing the interval to six months.

2. Expedite evaluation of Technical Evaluation Request (TER) No. 92-0290, that recommended replacement of HPCS-LS-3A/3B with an alternative design to provide a more reliable and repeatable response time of less than or equal to one (1) second. The TER evaluation will be completed by February 28, 1993.

3. Maintenance will investigate the susceptibility of the FCI pipe break detectors to RFI from portable radio transmissions under MWR No. AP1526. This will be completed by January 31, 1993.

4. Amend the Root Cause Analysis and submit a supplemental LER if the Maintenance investigation provides conclusive evidence that RFI was the root cause. This will be completed by February 28, 1993.

pffft N There is no safety significance associated with this event, as there was no actual Colidensate Storage Tank or Suppression Pool level change. The HPCS system pump suction valve switchover operated as designed, with the safety function being continuously satisfied by either the Condensate Storage Tanks or the Suppression Pool as a water source. Accordingly, this event posed no threat to the health and safety of either the public or Plant personnel.

imilar Ev n LER 90-011, "High Pressure Core Spray (HPCS) System Pump Suction Valve Switchover Actuation

- Cause Unknown." The cause of this event was indeterminate, attributed to an apparent spurious transient. The Suppression Pool level switches, and Condensate Storage Tank level switches and pipe break detectors were calibrated and returned to service with no further corrective action identified.

LICENSEE EVENT REPORT ER)

TEXT CONTINUATION AGILITY NAME (I) DOCKET NUM8ER (2) LER NUM8ER (8) AGE (3) ear umber ev. No.

Washington Nuclear Plant - Unit 2 0 5 0 0 0 3 9 7 2 44 0 5 F 5 ITLE (4)

HIGH PRESSURE CORE SPRAY (HPCS) SYSTEM PUMP SUCTION VALVE AUTOMATIC SWITCHOVER ACTUATION EII Inf rm Tex Ref rence BHHRf

$ gggm Q~m~nn High Pressure Core Spray (HPCS) BG HPCS-V-1 BG Suppression Pool NH Condensate Storage Tank KA TK HPCS-LS-1A BG LIS HPCS-LS-1B BG LIS HPCS-LS-3A BG MS HPCS-LS-3B BG MS