ML20028H714

LER 90-019-00:on 901226,isolation Signal Caused Reactor Water Cleanup Inlet Inboard Isolation Valve to Automatically Close.Caused by de-energized HPCI Isolation Relay.Riley Scam Temp Switch Units Will Be replaced.W/910124 Ltr

ML20028H714
Person / Time
Site:	Brunswick
Issue date:	01/24/1991
From:	Harness J, Toler W CAROLINA POWER & LIGHT CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
BSEP-91-0043, LER-90-019-02, NUDOCS 9101290118
Download: ML20028H714 (4)

Text

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Cp&L Carolina Power & Light Company Brunswick Nuclear Project P O. Box 10429 c,euhpo rt . N.C. 28461 0429 January 24,1991 '

FILE: B09 13510C 10CFR50.73 SERIAL: BSEP/91 0043 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, D. C. 20555 BRUNSWICK STEAM ELECTRIC PLANT UNIT 2 DOCKET No. 50 324 LICENSE NO. DPR 62 LICENSEE EVENT REPORT 2 90-019 Centlemen:

In accordance with Title 10 of the Code of Federal Regulations, the enclosed Licensee Event Report is submitted. This report fulfills tha requirement for a written report within thirty (30) days of a reportable occurrence and is submitted in accordance with the format set forth in NUREC 1022, September 1983.

Very truly yours,

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. L. Harn s, Ceneral Manager Brunswick clear Project WRT/

Enclosure cc: Mr. S. D. Ebneter Mr. N. B. Le BSEP NRC Resident Office l

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Mc I OHM M U $. NUCLfAR fiE GULATORY COMM!SL:ON APPROVED OMB f40. 31bO0104 EXPlRE b: o/30/92 l ESTIMATLD BURDE N PE R RESPONSE TO COMPLY W"TH TH1$ INFORMATiON COLLECTION REQUEST: 50.0 HRS FORA ARD COMMENTS REGARDiNO BUR EN ESMATM THE REC H $ AND RUOMS MANAGEMENT BRANCH

. ' LICENSEE *"* VENT REPORT (LER) (P-130). U $ NUCLEAR 873ULATORY COMM!$$10N. WASHINOTON. DC 2D555.

AND TO THE PAPERWORK REDUCTION PROJECT (3150-0104). OFFICE OF MANAGE MENT AND BUDGET, WASHINGTON. DC 20503.

rAoutvNAMen) Brunswick F**am Electric Plant Unit 2 DOCPIT NUMBER (2) PAGE (3) 05000324 01 0F 03 T:Ta m RVCU ISOLATION DURING HPCI MST DUE TO SPURIOUS ACTUATION OF STEAM LEAK DETECTION INSTRUMENTATION f VENT DATE ($) LEf4 NUMDER f6) f4 FOM DATE (7) OTHER FACIUTitS INCLVED (8)

M? NTH DAY YEAR YEAR LEO NO. REV. NO. MONTH DAY YEAR FAaUTYNAME DOCPIT NUYDER 12 26 90 90 - 019 - 00 01 24 91 THIS RE80RT l$ SUBMTTED PUR$UANT TO THE REQUIREMENTS OF 10 CFR $ (Check one or more of the following)(11) 014 RATING MDDE (9) 1 20.402(t>) 20.OS(c) X S0.73(aX210v) 13 71(b)

POWE 81 20 405(aH110) 50.E(c)(1) 50.73ta H2Hv) 73.71(c)

LEVEL 00) 100 20.40S(aH901) 50.M(cM2) Mh(2)M) OTHER (Spech in Abstract and Text) 20 435taHilfm) 50.73(a)(2)C) 50.73(aH2)fvtH)(A) 20 40$(a)0Hiv) 50.73:aH7)(u) $0 7 hah 2HvmHB) 20 435(aH1Hv) $0.73(a):2 Hill) 50.73taH2Hn)

UCE NSEE CONTACT FOR THl$ LIR (12)

NAME VILLIAM R. TOLER, RECULATORY COMPLIANCE TELEPHONE NUMBER (919) 117-2701 COMPLETE **4E UNE FOR EACH COMPONENT F AILURE DESCRIBED IN THIS REFORT (13)

CAutE S f STE M COMPONE NT MANUF ACTURE R REPORTABLE TO NPRDS wh CAUSE SYSTEM COMPONENT MANUFACTURER REPORTABLE TO NPRDS SUPPLEMENTAL REFORT EXPECTED (14) EXPECTED MONTH DAY YEAR SUBMISSION 4 Eh Of yes. comrWete EXPECTED $UDM:SSION DATE) X NO DATE (15)

Y ADETRACT (Umrt to 1400 spaces, te. apprommateiy fmeen sangie space taewetten enes) 06)

At 0836 on December 26, 1990 an "A" logic Group 3 isolation signal caused the Reactor Water Cleanup (RWCU) Inlet Inboard Isolation Valve (2-G31-F001) to automatically close. This occurred when scheduled maintenance on the High Pressure Coolant Injection (HPCI) system created an electrical disturbance which tripped the Riley SCAM module (temperature switches) of the RVCU Steam Leak Detection System (SLDS) and resulted in a spurious isolation signal. The Control Operator became aware of this through appropriate Control Room indication and annunciation. The isolation valve was reopened at 0858 and the RVCU System was returned to service.

The susceptibility of these switches to spurious trips has been documented in General Electric Service Information Letters (SILS 416 and 443) and IE Information Notice 86-69. CP&LS original plans were to install time-delay relays in the SLDS circuitry to reduce the probability of spurious trips; however, it has since been determined this was only a partial remedy for broader problems with the current SLDS. Current plans include replacing the existing Riley SCAM temperature switch units with more modern NUMAC hardware.

During this event the Reactor was at 100 percent power. The event had no safety significance since Emergency Core Cooling Systems were operable and the RVCU isolation system operated per design. Prior events involving Riley SCAM modules are reported in LERs 2-83 58, 2-84-17, 1-86-008, 1-86-014, 2-87-007, 2-87-009, 1-88-002, 2-88 020, 1-89-004 and 1-89-005.

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TEXT CONTINUATION MAN ^=wT BRANCH es3m. u.s NUCttAR ntoutATOnY COMMISSION.

WASHINGTON, DC 70555. AND TO THE PAFYRWORK RLDUCTION PfGiECT 1

Q1SO4104). OFFICE OF MANAGEMENT AND DVDGET, WASHiNOTON,0C 20503 F Atlu1V NAMC (1) DOC MT LER NUMBER (6) PAGE (3)

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Brunswick Steam Electric Plant Unit 2 05000324 YEAR NUMBER NUMBER 02 of 03 90 - 019 -

00 f(KT ($ MORL Sr ACE l$ flEOUIRED, USC ADDITIONAL NFC FORM 306A'S)(17)

EVENT A spurious Primary containment Croup 3 isolation was generated in the "A" logic during performance of the llPCI Steam Leak Detection Channel Calibration (2MST-IIPCI25Q) resulting in auto closure of Reactor Vater Cleanup (RUCU) Inlet Inboard Isolation Valve 2-031-F001.

INITIAL CONDITIONS Unit 2 was operating at 100 percent power. The Reactor Core Isolation Cooling System (EIIS/EN), Core Spray (EIIS/BM), Residual llent Removal / Low Pressure Coolant Injection (EIIS/BO), and Automatic Depressurization systems were operable and in standby readiness. Required surveillance was in progress for the liigh Pressure Coolant Injection (EIIS/BJ) system with work being performed in the Steam Leak Detection Panel 2 -Ill2 - P614 (EIIS/IJ/PNL), located in the back panel area of the control Room.

EVENT DESCRIPTION On Dc ember 26,1990 at 0836, a Primary Containment Isolation System (EIIS/JM) Croup 3 isolation was received while performing a step in 2MST-llPCI25Q which requires an external lead (terminal CC-19) in panel E614 to be lif ted, labeled and taped. Leads are lif ted during this Maintenance Surveillance Test (MST) to remove power from the temperature switches for personnel safety, The lead on terminal CC-19 was the first of six leads to be lif ted. When this lead was lif ted, llPCI isolation relay (2-B21B-K4A) (EIIS/BJ/RLY) deenergized and the RWCU Steam Leak Detection Differential Temperature switch module (EIIS/CE/IJ/TDS/ MOD) in the same cabinet tripped, causing RWCU Inlet Inboard Isolation Valve "C31-F001" (EIIS/CE/ISV) to close. The isolation module reset almost immediately (0.018 seconds) af ter the trip indicating no actual leak condition existed. AT 0841 I60 personwl were directed to finish lifting the remaining leads in panel P614 which was accomplished without further incident. At 0858 the isolation valve was reopened and preparations for returning the RWCU system to service were begun.

EVENT INVESTICATION The Emergency Response Facility Information System (ERFIS) alarm t showed chronologically that a Group 4A signal (HPCI "A" logic) was generated, yperfollowed by a Steam Leak Detection Differential Temperature llI DTEMP signal, immediately followed by a Group 3A (RVCU "A" logic) signal and immediate subsequent closure of C31-F001. The installed Riley SCAM modules used in the Steam Leak Detection System (SLDS) are extremely sensitive and have a history of causing spurious system isolations. The susceptibility of these types of modules to spurious trips has been documented by General Electric Service Information Letters (SILS 416 and 443) and by IE Information Notice (IEN) 86-69. The IEN addressed recurring problems which have been identified by LERs throughout the nuclear industry. The predominant source of the monitor trips was identified as the operation of the read / set switch. Other identified trips were attriputed to electrical noise and nearby maintenance activities. The Riley SCAM modules affected in this event were in the proximity of the IIPCI isolation relay (2-B21B-K4A) which was deenergized while performing 2MST-IIPCI25Q.

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HIC FORM 366A U.S. NUCLEAR REOULATORY COMMIS$10N APPROVZO OMB No. 31500104 EXPIRES: 4/30S2 ESTIMATED BURDEN PER RESDONSE To COMPLY WITH THIS INFORMATION LICENSEE EVENT REPORT _ (LER) C '@n"lM'glu"A'EE"TE coy To THE nEcoRos ANo nEPoRTs TEXT CONTINUATlON MANWMM BRANCH (4530). U.S. NUCLEAR REOULATORY COMMIS$0N.

WA$HINGTON. DC 20555. AND TO THE PAPERWORK REDUCTION PR3 JECT (3150-0104). OFFICE oF MANAGEMEP(T AND BUDGET. WA$HINGTON.DC 20503 FACluTY NAME (1) DOCKET LER NUMBER (6) PAGE (3)

NUMBD. (2)

Brunswick Steam Electric Plant Unit 2 swu m m 05000324 'rtAR NUMBER NUMBER 90 - 019 - 00 1E rt (tF MORE $0 ACE I$ REQUIRED. USE ADDITIONAL NRC FORM 306A*S) (17)

EVENT CAUSE This event resulted from a spurious isolation signal generated when the HPCI isolation relay (2-B21B-K4A) deenergized causing a mome. *.ary disturbance of the

• Steam Leak Detection Instrumentation power circuitry suffit lent to induce the trip

, of the Riley SCAM module.

CORRECTIVE ACTION A prior LER (2-88 020) documented an RWCU isolation during a HPCI MST due to a spurious trip of Riley Temperature Switches in the Steam Leak Detection System.

Corrective action for this LER stated that a project (PCN 02300) had been approved to replace the RWCU/HPCI/RCIC isolation relays with one-second time delay relays.

Implementation of these changes were scheduled to be completed on both units in 1990; however, since this project represented only a partial remedy for broader problems with the current Steam Leak Detection System, it has been cancelled and the scope absorbed into a new project (PCN 00051). The new project will include replacing the existing Riley SCAM temperature switch units with more modern NUMAC

. hardware. A major consequence of this project is expected to be a reduction in spurious isolations caused by the leak detection instrumentation. The Unit 1 modification is scheduled to be im lemented during Refueling Outage B109R1 in 1992 and the Unit 2 modification is sch duled to be implemented during Refueling Outage B211R1 in 1993.

EVENT ASSESSMEN_T The isolation module automatically reset almost immediately after the trip indicating- no actual leak condition existed. Additionally, a system walkdown revealed no leaks. The RWCU system isolated per design-therefore there is no-safety significance associated with this event.

Prior events involving Riley SCAM modules and inadvertent system isolations are reported in LERs 2-83-58, 2-84-17, 1-86-008, 1-86-014, 2-87-007, 2-87-009, 1-88-002, 2-88-020, 1-89-004, and 1-89-005.

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