ML19327B986

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LER 89-017-01:on 890624,HPCI Sys,Steam Line Break Delta Pressure High Signal,Channel A,Isolation Occurred.Root Cause Investigation Underway.Work Request/Job Order Initiated Requesting Verification of readings.W/891106 Ltr
ML19327B986
Person / Time
Site: Brunswick Duke Energy icon.png
Issue date: 11/06/1989
From: Harness J, Jones T
CAROLINA POWER & LIGHT CO.
To:
NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
BSEP-89-0986, BSEP-89-986, LER-89-017, LER-89-17, NUDOCS 8911140345
Download: ML19327B986 (5)
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. ~*4 i.?E Carolina Power & Light Company t

Brunswick Nuclear Project P. O. Box 10429 .

Southport,.NC 28461-0429  !

t November 6, 1989 FILE: B09-13510C 10CFR50.73 SERIAL: BSEP/89-0086 1

U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555 BRUNSWICK STEAM ELECTRIC PLANT UNIT 1 DOCKET NO. 50-325 1ICENSE NO, DPR-71 3 ,

SUPPLEMENTAL LI.CENSEE EVENT REPORT 1-89-017-01 Gentlemen:

In accordance with Title 10 to the Code of Federal Regulations, the enclosed Supplemental Licensee Event Report is submitted. The original report fulfilled the requirement for.a written report within thirty (30) days of a reportabic occurrence and was in accordance with the format set forth in NUBEG-1022, i September.1983.

Very truly yours, J. L. Harness, Geni al Manager Brunswick Nuclear Project TMJ/mcg '

Enclosure cc: Mr. S. D. Ebneter '

Mr. E. G. Tourigny t BSEP NRC Resident Office 8911140345 891106 PDR ADOCK 05000325 "IE2A ,

S PDC

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Ort J uli e 24, 1989, System, steam Iine at 2105 !tou rs , a li t gtt l'r ess u t e C(x>latit occurred ,n l'n i t 1. break deIta pressute No other act ivi t ies At the t ime of t high signa 1, A chanw l't j 1e( t ioli t ilit l )

of the were event ,

iso 1ation the ins t rument at ion wh initiates ichinand progress,he no the un i t was in personnel were cold shutdown.

isolation was caused the found in the area unit by a spurious trip te'erenced signal .

it has1-E41-PDTM-N004-1.

been replaced. The re fe r enced of It is believed cause invest.igation of A similat event was trip unitredundant is a Division i ECCS11ip this reported in Rosemount 510 DU, and investigatiag similar problems have event has beon A root I been es t ab)ished actions will be industry. based upon w i t h510bot DI' h 1

. mo r id and husemou n tt rip un i t s aid cont.nts 1 ime iwt i(i ktishalsoRos emoun tin continuing e f f ort: by the Finai c or iet t ive This event vendor aul tin alt ernat ive would conditions not have been more detigned. as the tailureseveie mode under reasonable and caused the systems to cred.ble tutuite as 3)

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Brunswick Steam Electric Plant 'f'" " Wa" MU Unit 1 0l6l0loloj3l2l5 8l9 -

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0 l1 0l 2 0F 0 [4 uut a ese ese e assuns, essnaw auc ame uns w on Event A spurious isolation of the A chainnel, liigh Pressure Coolant Injection (llPCI/E41) (EIIS/BJ) System occurred.

Initial Conditions The Unit I reactor was in cold shutdown during the 20-day June 1989 outage for the replacement of the A Core Spray (CS/E21) pump motor (EIIS/BM/MO). The Automatic Depressurization System (ADS /B21) (EIIS/*), Reactor Core Isolation Cooling system (RCIC/E51) (EIIS/BN) and HPCI System were not required to be operable. HPCI and RCIC were isolated on low steam pressure as per design.

The B CS System and the A and B loops of the Residual licat Removal / Low Pressure Coolant Injection (RllR/LPC1/E11) (EIIS/BO) Systems wnre oparable.

The A loop of RHR was being utilir.cd in the shutdown cooling mode of operation. No testitig or evolv.clons were in progress at the time of the event.

Event Description On June 25, 1989, at 2105 hours0.0244 days <br />0.585 hours <br />0.00348 weeks <br />8.009525e-4 months <br />, the annunciators HPCI STEAM LINE BREAK delta j PRESSURE 111 end IIPCI ISOLATION TRIP SIGNAL A INITI ATED were received. The steam line break delta pressure signal immediately reset, and therefore, did not seal in when the Control Operator (CO) responded to the annunciation. The isolation annunciator and the A isolation channel indicating light remained illuminated. The A isolation valves did not change position as they were aircady closed. 1-E41-F041 is normally closed and the 1-E41-F003 was closed due to low steam pressure automatic isolation because the unit was in cold i shutdown. The C0 dispatched an A0 to the HPCI area and investigated the llPCI l Steam line High delta Pressure instrument, 1-E41-PDTM-N004-1, (EIIS/BJ/PDT)  !

located in the analog cabinets of the Control Room back panel area. The j instrument was found to be reading approximately minus twenty-five, which was ,

l within its expected range for the given conditions, and neither a gross failure or a trip was indicated on the master or slave analog unit. There i were no personnel noted in the area of the analog units or the llPCI System. A l l work request and job order (WR/JO 89-ANYV1) was initiated for the Instrument {'

& Control (I&C) personnel to investigate the cause of the isolation and tracking limiting conditions for operation (LCOs), TI-89-1159 and 1160, were initiated. The isolation was not reset until the I&C personnel had the opportunity to investigate a possibic cause. The I&C personnel checked the voltage across the instrument contacts which would have resulted in the isolation signal but no problem was indicated. The analog trip unit was replaced with a spare trip module and the tracking LCOs were cancelled on June 26, 1989, at 1215 hours0.0141 days <br />0.338 hours <br />0.00201 weeks <br />4.623075e-4 months <br /> after successful completion of applicable i portions of surveillance test procedure IMST-ilPCI21M, HPCI St.com Line Break High D/P Trip Unit Channel Calibration, for the postmaintenance testing of 1-E41-PDTM-N004-1. The original trip unit was turned over to Technical Support (T/S) for a root cause evaluation.

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  • (KPIRES: $/31/N I PAS $40?T N4AAt nl , EK8 CELI NUMDER LI LE2NUM98211 *All (3 BrunBWick Steam Electric P.lant P" U*E Unit 1 or 0 l5 l0 l0 l013 l 215 81 9 0 l 1l 7 -

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, 13tf a sino ausse e soceent use ensuunst Anc paue asseW 6:n Event Investigation The root cause of the N004-1 trip is still under investigation. A similar event was reported in LER 2-89-008. Both events involved Rosemount 510 DU trip unita, which were apparently tripped without a trip indication. These units were the first analog trip units Rosemount marketed, and the components of the 510 DU trip uni.ts are, in general, approximately 10 years old, even though they were not installed until the early 1980s at Brunswick. A search of NPRDS data resulted in eleven other possibic similar problems at Branswick, beginning in 1982, as well as others at different plants. The Ic arick plant has experienced similar problems over the past two years and has been conducting an investigation but has not yet determined the problem. In addition, Rosemount is researching the problem on a generic basis and has not identified the cause. Selected Brunswick equipment which has experienced problems was being bench tested and Technical Support was abic to duplicate the problem. The testing consisted of monitoring the voltage output of the analog trip unit as the ambient temperature increased and the input voltage was varied. Testing indicates that. these failures can occur in one of two ways:

1. The voltage output of the trip unit increasing and maintaining at above 0.0 volts direct current (VDC).
2. . The voltage output of the trip unit momentarily increasing above 0.0 VDC.

l l Voltages of 11-16 VDC have been observed. These increases pick up the instruments 24 VDC slave relay (Ells /JE/RLY) resulting in the observed l spurious trips. t l

l Root Cause An investigation as to the root cause is still underway by the vendor.

l i Corrective Actions As a result of the event reported in LER 2-89-008, a WR/JO was initiated requesting that the voltage output readings on ot.her, normally deenergized, analog trip units be verified. Normally energized units would trip if their voltage output were to be checked. This, combined with the fact that the l

energized units have not exhibited spurious trips, has limited the voltage i

output verifications to normally deenergized units. On July 7, 1989, two additional trip units were found to have an elevated voltage output. The 2-B21-PTS-N023 B-2 was found to be putting out approximately 13 volts DC but 1

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was not tripped. The referenced unit supplies a Reactor Pressure liigh annun-clator only. The 2-D21-LTM-N017 B-2 was found to be putting out approximately 16 or 17 volts DC and was tripped but did not indicate a tripped or failed condition. This instrument is not a Technical Specification instrument and supplies one half of the high level trip circuitry for the HPCI System. In both instances, the associated analog cards were pulled and the contact stabs were cleaned. Af ter clenning, the voltage output for the trip units dropped to less than I volt DC. The WR/JO was lef t open to see if cleaning the contacts had solved the problem or had simply masked it. On July 10, 1989, the voltage output for the af fected units was rechecked. The 2-B21-LTM-N017 B-2 high 1cvel trip unit for HPCI was again found to be tripped without indication. At that time the unit was replaced and bench testing of the original unit was commenced.

The testing did not determine the root cause, but a slight output voltage increase was noted with increasing ambient temperature.

As a temporary measure, special procedure (SP)89-038 was developed to periodically check the output voltage of inservice Rosemount 510 DU trip units for both Unit 1 and 2. This procedure outlines the steps to be taken in the event a trip unit is found to have an output voltage different from what is expected. l In addition, the stock Ictel of Rosemount 710 DU trip units has been raised.  ;

These trip units are the newer models furnished by Rosemount. Although the '

schematics of both models are virtually identical, the physical layout of the components are different and the 710 DU trip units have been " life qualified" i by Rosemount where as the 510 DU units were not. A unit is considered " life qualified" by the vendor after test data is collected, under varying and ,

extreme environmental conditions, and utilized to develop a curve indicating )

the expected time that the instrument will function in given conditions.

i Technical Support hand carried 510 DU trip units to Rosemount and worked with  !

them to set up a test facility to determine the root cause of the trip  !

problems. The vendor hr.s been successful in duplicating the failurec and is

. continuing testing and analysis to determine the root cause(s). Final I corrective actions will be based upon continuing efforts by the vendor and the industry, which the NRC is following f rom a generic standpoint.

Event Assessmeg J This event would not have been more severe under other reasonable and credible alternative conditions as the failure mode caused the systems to actuate as k designed.

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F ACILITY N AME H) DOCERT NUMf dR Qi PAGE W

> Brunswick Steam Electric Plant Unit 1 0 l 5 l 0 l 0 l 0 l 312 ] 5 1 lOFl0 14 -

l nT'ai* Spurious Isolation of High Pressure Coolant Injection Channel A Caused by Suspected Failure of Rosemount 510 DU Trip Unit EVENT DATE 19) LER NUMSER (6) REPORT DATE (7) OTHE R F ACitlTIES INVOtVED ISI YEAR YEAR sto 6ai MONTH DAY YEAR P ACILITv h AMts DOChtT NUMSER(si MONTH l DAY p ,

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LICEN8tt CONT ACT FOR THis LER H2) . j NJ.M E TELEPHONE NUM84R  !

ARE A CODE i T. M. Jones, Specialist - Regulatory Comp 11arece 9 l1l9 4;5;7l i 2l0 ;3;9 i COMPLETE ONE LINE FOR EACH COMPONENT F AILURE DESCRIBED IN THis REPORT tt31 Rt *OR i A Lt R ORfA i -

CAUSE SY8itM COMPONENT M A% AC. y pn g CAush SYST E M COMPONENT MAMAC- pp X JE t lPt DlT R 1 3l6l9 Y_ i i 1 l l l 1 l l I l l l ! l l l i I I l M SUPPLEMENTAL REPORT EXPICTED (14) MONTH DAY YEAR SUOMISSION i Yt5 III ven. tonswere futCTED SU66,13SION DMll f NO l l l A 72. AC r m,=, e. vuo e ,.e . ,e.-.., ,= ey, e ,, ,,el.m e, H.,

On June 24, 1989, at 2105 hours0.0244 days <br />0.585 hours <br />0.00348 weeks <br />8.009525e-4 months <br />, a liigh Pressure Coolant injection (llPCI)  !

System, steam line break delta pressure high signal, A channel, isolation occurred on Unit 1. At the time of the event the unit was in cold shutdown.

No other activities were in progress, and no personnel were found in the crea of the instrumentation which initiates the referenced signal. It is believed the isolation was caused by a spurious trip of redundant Division 1 ECCS trip unit 1-E41-PDTM-N004-1. The referenced trip unit is a Rosemount 510 DU, and 1 l it has been replaced. A similar event was reported in LER 2 89-008. A root l I

l cause investigation of this event has been inconclusive. Limerick is also l investigating similar problems with Rosemount 510 DU trip units and contacts ,

have been established with both Limerick and Rosemount. Pinal corrective l actions will be based upon continuing ef forts by the vendor and the i industry. !i 0 This ever.t would not have been more severe under reasonable and credible ,

alternative conditions as the f ailure modo caused the systems to actuate as l i designed. l 1

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Event ,

i L ' A spurious isolation of the A channel, liigh Pressure Coolant Injection (llPCI/E41) (EIIS/BJ) System occurred, e

Initial Coniltions The Unit i reactor was in cold shutdown during the 20-day June 1989 outage for the replacement of the A Core Spray (CS/E21) pump motor (EIIS/BM/MO). The Automatic Depressurization System (ADS /B21) (EIIS/*), Reactor Core Isolation Cooling system (RCIC/E51) (EIIS/BN) and IIPCI System were not required to be operable.' IIPCI and RCIC were isolated on low steam pressure as per design.

The B CS System and the A and B loops of the Residual lleat Removal / Low

~

Pressure Coolant Injection (RllR/LPCI/ Ell) (EIIS/BO) Systems were operable. 2 The A loop of RilR was being utilized in the shutdown cooling mode of )

. operation. No testitig or evolutions were in progress at the time of the event. j Event Description On June 25, 1989, at 2105 hours0.0244 days <br />0.585 hours <br />0.00348 weeks <br />8.009525e-4 months <br />, the annunciators llPCI STEAM LINE BREAK delta PRESSURE III and flPCI ISOLATION TRIP SIGNAL A INITIATED were received. The i steam line break delta pressure signal immediately reset, and therefore, did j not seal in when the Control Operator (CO) responded to the annunciation. The  :

Isolation annunciator and the A isolation channel indicating light remained illuminated. The A isolation valves did not change position as they were already closed. 1-E41-F041 is normally closed and the 1-E41-F003 was closed j due to low steam pressure automatic isolation because the unit was in cold  !

shutdown. The C0 dispatched an AO to the llPCI area and investigated the llPCI ,

Steam line liigh delta Pressure instrument, 1-E41-PDTM-N004-1,-(EIIS/BJ/PDT) i located in the analog cabinets of the Control Room back panel area. The '

instrument was found to be reading approximately minus twenty-five, which was within its expected range for the given conditions, and neither a gross failure or a trip was indicated on the master or slave analog unit. There were no personnel noted in the area of the analog units or the llPCI System. A work request and job order (WR/JO 89-ANYW1) was initiated for the Instrument

& Control (ISC) personnel to investigate the cause of the isolation and tracking limiting conditions for operation (LCOs), TI-89-1159 and 1160, were initiated. The isolation was not reset until the I6C personnel had the opportunity to investigate a possible cause. The 160 personnel checked the i s voltage across the instrument contacts which would have resulted in the J isolation signal but no problem was indicated. The analog trip unit was i replaced with a spare trip module and the tracking LCOs were cancelled on l June 26, 1989, at 1215 hours0.0141 days <br />0.338 hours <br />0.00201 weeks <br />4.623075e-4 months <br /> after successful completion of applicable i portions of surveillance test procedure IMST-llPCI21M, llPCI Steam Line Break Iligh D/P Trip Unit Channel Calibration, for the postmaintenance testing of l 1-E41-PDTM-N004-1. The original trip unit was turned over to Technical i Support (T/S) for a root cause evaluation. I

  • EIIS component identifier not found. ,

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d1 0l3 0F 0 l4 init c me= som a seemos em masu-w me e=== asse w on Event Investigation The root cause of the N004-1 trip is still under investigation. A similar event was reported in LER 2-89-008. Both events involved Rosemount 510 DU trip units, which were apparently tripped without a trip indication. These units were the first analog trip units Rosemount marketed, and the components of the 510.DU trip units are, in general, approximately 10 years old, even though they were not installed until the early 1980s at Brunswick. A search of NPRDS data resulted in eleven other possibic similar problems at Brunswick, beginning in 1982, as well as others at different plants. The Limerick plant has experienced similar problems over the past two years and has been conducting an investigation but has not yet determined the problem. In addition, Rosemount is researching the problem on a generic basis and has not identified the cause. Selected Brunswick equipment which has experienced problems was being bench tested and Technical Support was able to duplicate the problem. The testing consisted of monitoring the veltage output of the analog trip unit as the ambient temperature increased and the input voltage was varied. Testing indicates that these failures can occur in one of two ways:

1. The voltage output of the trip unit increasing and maintaining at above 0.0 volts direct current (VDC).

2, . The voltage output of the trip unit momentarily increasing above 0.0 VDC.

[

Voltages of 11-16 VDC have been observed. These increases pick up the

! instruments 24 VDC slave relay (EIIS/JE/RLY) resulting in the observed f spurious trips.

F poot Cause An investigation as to the root cause is still underway by the vendor.

(

Corrective Actions As.a result of the event reported in LER 2-89-008, a WR/JO was initiated requesting that the voltage output readings on other, normally deenergized, analog trip units be verified. Normally energized units would trip if their voltage output were to be checked. This, combined with the fact that the energized units have not exhibited spurious trips, has limited the voltage output verifications to normally deenergized units. On July 7, 1989, two additional trip units were .found to have an elevated voltage output. The 2-B21-PTS-N023 B-2 was found to be putting out approximately 13 volts DC but g,,m .u.o.o...........

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  • Unit 1 '

0 l5 l0 lo l0 l3 l 2l5 8l9 -

0 l 1l 7 -

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\n was not tripped. The referenced unit supplies a Reactor Pressure liigh annun-clator only. The 2-B21-LTM-N017 B-2 was found to be putting out approximately 16 or 17 volts DC and was tripped but did not indicate a tripped or failed condition. This instrument is not a Technical Specification instrument and supplies one half of the high 1cvel trip circuitry for the IIPCI System. In both instances, the associated analog cards were pulled and the contact stabs were cleaned. After cleaning, the voltage output for the trip units dropped to less than 1 volt DC. The WR/JO was left open to see it cleaning the contacts had solved the problem or had simply masked it. On July 10, 1989, the voltage output for the affected units was rechecked. The 2-821-LTM-N017 B-2 high level trip unit for HPCI was again found to be tripped without indication. At that time the unit was replaced and bench testing of the original unit was commenced.

The testing did not determine the root cause, but a slight output voltage increase was noted with increasing ambient temperature.

As a temporary measure, special procedure (SP)89-038 was developed to periodically check the output voltage of inservice Rosemount 510 DU trip units for both Unit 1 and 2. This procedure outlines the steps to be taken in the event a trip unit is found to have an output voltage different from what is expected.

In addition, the stock level of Rosemount 710 DU trip units has been raised.

These trip units are the newer models furnished by Rosemount. Although the t schem.itics of both models are virtually identical, the physical layout of the components are different and the 710 DU trip units have been " life qualified" by Rosemount where as the 510 DU units were not. A unit is considerud " life qualified" by the vendor after test data is collected, under varying and extreme environmental conditions, and utilized to develop a curve indicating the expected time that the instrument will f'metion in given conditions.

Technical Support hand carried 510 DU trip units to Rosemount and worked with them to set up a test facility to determine the oot cause of the trip problems. The vender hr.s been successful in duplicating the failures and is ,

continuing testing and analysis to determine the root cause(s). Final corrective actions will be based upon continuing efforts by the vendor and the industry, which the NRC is following from a generic standpoint.

Event Assessment This event would not have been more severe under other reasonabic and credible alternative conditions as the failure mode caused the systems to actuate as des ig;ned.

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