ML20005E402

LER 89-028-00:on 891204,steam Generator 1D Power Operated Relief Valve Did Not Close on Train a Main Steam Isolation Signal During Valve Inservice Test.Caused by Failed Fuse. Fuse replaced.W/891229 Ltr

ML20005E402
Person / Time
Site:	Catawba
Issue date:	12/29/1989
From:	Glover R, Owen T DUKE POWER CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
LER-89-028, NUDOCS 9001050183
Download: ML20005E402 (7)

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l DUKE POWER-e l December:29, 1989' Document: Control Desk U.-S. Nuclear Regulatory Commission Washington, D. C. .

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Subject:

. Catawba Nuclear Station Docket No.. 50-413 LER 413/89  ; Gentlemen:

Attached.is~ Licensee Event Report- 413/89-28, concerning Technical

Specification violation as a result of the loss of Train 'A'--main steamdisolation for steam generator power operated relief-valves-duc sto a failed fuse.

This' event was considered to be of no significance with respect to the-Lhealth and safety of the public.

1Very'truly yours,

-[

Tony.B. Owen

-Station: Manager e

keb\LER-NRC.TBO xc: Mr. S..D. Ebneter American Nuclear Insurers  ;

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. Regional Administrator, Region II c/o Dottie Sherman, ANI Library '

U. S. Nuclear Regulator Commission The Exchange, Suite 245 101 Marietta Street, tM, Suite 2900 270 Farmington Avenue Atlanta, GA 30323 Farmington, CT 06032 M & M Nuclear Consultants Mr. K. Jabbour 1221 Avenues of the Americas U. S. Nuclear Regulatory Commission ,

New' York, NY 10020 Office of Nuclear Reactor Regulation Washington, D. C. 20555

.INPO Records Center Suite 1500 Mr. W. T. Orders 1100 Circle 75 Parkway HRC Resident Inspector Atlanta, GA 30339 Catawba Nuclear Station 10 183 691229 S OCK 05000413 PDC

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Catawba Nuclear Station, Unit 1 0 l5 l 0101014 I ll 3 1 lOFl 016 t*'

Technical Specification Violation As A Result Of The Loss Of Train A Main Steam Isolation For Steam Generator Power Operated Relief Valves Due To A Failed Fuse

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'R.M. Glover, Compliance Manager 81013 81311 1-13 121316 COMPLETE ONE LINE FOR E ACH COMPONENT F AILURE OtsCRISED IN THis REPORT n31

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l 1 I I I f I I i l I I I I I l l l 1 I I I I I I I I I SUPPLEMENT AL REPORT EMPECTED H43 MONTH DAY vtAR YtS ,l! y.s. to-,s.t. (KPLCTEO $USMIS$10N CA Til NO l l l A.m ACT ,0.,. . , ~ . . . ,.. . o ,, ,,-, ,. ..,,.. ,, , n .,

On December 4, 1989, at 1000 hours0.0116 days <br />0.278 hours <br />0.00165 weeks <br />3.805e-4 months <br />, Unit I was in Mode 1, Power Operation, at 100% Power. ISV1, Steam Generator (S/G) 10 Power Operated Relief Valve (PORV),

did not close on a Train A Main Steam Isolation signal during the periodic SV l Valve Inservice Test. At 1045 hours0.0121 days <br />0.29 hours <br />0.00173 weeks <br />3.976225e-4 months <br />, all four S/G PORVs were declared L

inoperable, and Technical Specification 3.3.2, Action 21, was entered for one i- train of Steam Line Isolation being inoperable. A work request had been written on December 3 to investigate / repair the SM PORV Train A Reset light. A failed l fuse (A-39 in cabinet IEATC12) was found in the Train A Main Steam Isolation I

circuit, and was replaced by 1235 hours0.0143 days <br />0.343 hours <br />0.00204 weeks <br />4.699175e-4 months <br />. By 1305 hours0.0151 days <br />0.363 hours <br />0.00216 weeks <br />4.965525e-4 months <br />, Action 21 was exited  ;

l and the S/G PORVs were returned to operable status following successful completion of the SV Valve Inservice Test. This incident is classified as an equipment failure, due to the mechanical failure of fuse A-39, a Bussman FNA type fuse. As documented in LERs 414/89-001 and 413/89-015, the Bussman FNA l fuses have experienced a high failure rate. The changeout of all remaining Bussman FNA fuses to Littlefuse type FLQ fuses is planned. Fuse A-39 was subsequently replaced with a Littlefuse type FLQ fuse. This incident has also been assigned a contributing cause of inadequate supervision, resulting from the Shift Supervisor not directing further immediate investigation of the unlit indicator light.

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0l0 012 oF 0 l6 vm n -. s ci muu nn l BACKGROUND The purpose of the Main Steam [EIIS:SB] (SM) System.is to transfer steam from 4- the Steam Generators [EIIS:HX] (S/Gs) to Main Turbine [EIIS:TRB] and Auxiliary Building loads. The controls for all four Main Steam Isolation Valves [EIIS:V]

(MSIVs) are identical. The Control Room (CR) switches [EIIS:XIS] for the valves are located on Main Control Board 1MC2. Since the_ valves provide a safety I

- function, circuitry'is provided for redundancy. Normally closed Trains A and B ' l Solid State Protection System (SSPS) contacts will automatically open on the j following signals: 1) High Steamline Flow coincident with Low Steamline-Pressure, 2) High Steamline' Flow Coincident with Low-Low T avg, or 3) High-High l Containment Pressure. This automatic action by either train of the SSPS will I e

close all of the MSIVs and their Bypasses, in addition to the S/G Power Operated i Relief Valves (PORVs).

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The Main Steam Vent to Atmosphere [E!IS:VL] (SV) and Main Steam Bypass to r Condenser [EIIS:S0] (SB) Systems control S/G pressure and Nuclear Steam Supply System (NSSS) thermal loading by relieving main steam as required to the main condenser and atmosphere.

4 A PORV is located on each' main steam line upstream of the MSIV. The PORVs are L pressure control valves provided primarily as overpressure protection devices to preserve the main steam safety valves. During 'nild pressure transients, the PORVs open to prevent main safety actuation. Following main safety actuation,

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the PORVs assist in' lowering main steam pressure and thereby aid in reseating

'the actuated safeties. This PORV function is not safety grade.

The PORVs-also provide a safety grade means of S/G depressurization and Reactor Coolant [EIIS:AB] (NC) System cooldown when the Condenser Dump valves are not available. PORV capacity is sufficient to effect a 50 degree F/hr cooldown rate.

However, as for the safety valves, PORV capacity is not great enough to cause I

unacceptable S/G blowdown should a valve inadvertently stick open. The PORVs are designed to close on any Main Steam Isolation signal.

Each PORV is provided with a manually controlled electric motor [EIIS:M0]

operated block valve (ISV25B, 268, 28A, and 27A for S/G PORVs ISV1, 7, 13, and 19, respectively). These valves primarily serve to isolate the S/G PORVs for maintenance. However, each block valve operator is designed for closure against .

l steam flow through a full open PORV. Thus, a block valve can limit S/G blowdown i ,

should a PORV stick open.

PT/1/A/4200/31, SV Valve Inservice Test-Quarterly, is used to periodically test the stroke times of ISV1, 7, 13, and 19. This test can be performed in any mode,'and allows any valve to be tested individually or all four to be tested at i

once. The valves to be tested, with their associated block valves closed, are l opened, then closed by the closure of a switched jumper installed across the

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e. texw- = = - = - -w. -. wa-w =c r- msw on 2,1 1 Train A SSPS output contacts for Main Steam Isolation. From the time this F switch is closed until it is removed and the PORVs are reset, rone of the PORVs-f are capable of opening automatically. However, they are all capable of being y -opened manually at any time during the test.

) EVENT DESCRIPTION' On December 3, 1989, with' Unit 1 in Mode 1, Power Operation, at 100% power, a Control Room Operator (CRO) noted that the SM PORV Train A Reset Light [EIIS:XI]

4 was not illuminated. This light should normally illuminate with Main Steam Isolation reset. Following changeout with a new bulb, the Shift Supervisor directed that a work request should be written to Inspect / Repair (I/R) the i light. Work Request 51777 OPS was initiated at 1110 hours0.0128 days <br />0.308 hours <br />0.00184 weeks <br />4.22355e-4 months <br />. An Out of Service 4 sticker was placed on the control board. The work request was then placed in i the appropriate box outside the Unit Coordinator's office for prioritization.

5 On December 4, 1989, Unit 1 was in Mode 1, Power Operation, at 100% power. At

. approximately 1000 hours0.0116 days <br />0.278 hours <br />0.00165 weeks <br />3.805e-4 months <br />, Performance Technicians began preparations to stroke

• time test the S/G PORVs, per PT/1/A/4200/31, SV Valve Inservice Test-Quarterly.

1 At approximately 1045 hours0.0121 days <br />0.29 hours <br />0.00173 weeks <br />3.976225e-4 months <br />, ISV1, S/G 1D PORV would not close on the isolation signal. At 1045 hours0.0121 days <br />0.29 hours <br />0.00173 weeks <br />3.976225e-4 months <br />, the CR0 declared the four S/G PORVs inoperable, because ISV1 would not close on a Train A SSPS signal which also. actuates ISV 7, 13, and

19. A Performance Engineer suspected that a fuse had blown or failed and

. subsequently, Work Request 51777 OPS was upgraded in priority for repair. Unit I was placed in a 6 hour6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> Action Statement for one train of Steam Line Isolation being inoperable, per Technical Specification 3.3.2, Action 21.

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At 1120 hours0.013 days <br />0.311 hours <br />0.00185 weeks <br />4.2616e-4 months <br />, on December 4, 1989, Instrumentation and Electrical (IAE)

Technicians replaced fuse A-39 (FNA 2 amp Bussman type) in cabinet 1EATC12. The reset light on panel 1MC2 was verified and a functional test was performed, per PT/1/A/4200/31. At 1235 hours0.0143 days <br />0.343 hours <br />0.00204 weeks <br />4.699175e-4 months <br />, the SM PORV TRN A Reset-light was declared operational. ISV1 was retested by the Performance PT at 1300 hours0.015 days <br />0.361 hours <br />0.00215 weeks <br />4.9465e-4 months <br />. The results were-satisfactory. The remaining PORVs were scheduled to be tested on December 5, 1989. The CR0 returned the S/G PORVs to operable status at 1305 hours0.0151 days <br />0.363 hours <br />0.00216 weeks <br />4.965525e-4 months <br />. The failed FNA fuse was sent to a Maintenance Engineering Services (MES)

Engineer for failure analysis.

Following a review of the status of Work Request 51777 OPS, the Operations Shif t Manager contacted a Projects Engineer at approximately 1900 hours0.022 days <br />0.528 hours <br />0.00314 weeks <br />7.2295e-4 months <br />, on December

. 4. Work Request 010872 IAE was initiated at 2040 hours0.0236 days <br />0.567 hours <br />0.00337 weeks <br />7.7622e-4 months <br /> to replace the FNA fuse with an FLQ (2 amp type Littlefuse) fuse. A partial completion notice had been sent to CNS Document Control on June 19, 1989 for Variation Notice CE-2131; however, the IAE Document Control area copy of CNBM-1717-01.12 was not marked to indicate the implementation of the exempt change. This change specified the required changeouts of the FNA type fuses with the FLQ type fuses, including those in 1EATC12. When fuse A-39 failed on December 4, 1989, the IAE g~~ .m..m.....m.m-

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0l0 0l4 oF 0l6 technicians properly used the Bill of Materials from IAE Document Control and

- replaced A-39 with an FNA_ type fuse instead of the FLQ type as required in the

, -.; exempt ~ change. PIR 1-C89-0366 was_ written on December 5, 1989 to document a 4 problem with the A-39 fuse replacement _on December 4, 1989 in 1EATC12. The PIR

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was sent to IAE for investigation. ,

CONCLUS10N:

This event has been attributed to Equipment Failure / Malfunction which resulted 3

in all four S/G PORVs.being declared inoperable. The failure of the FNA fuse

$ initiated the loss of the SM PORV Train A Reset Light as well as the resulting i Train A SSPS signal loss to ISV 1, 7, .13 and 19. The replacement of the'Bussman '

FNA fuses with the Littlefuse FLQ fuses resulted f-om previous mechanical

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P' i failures of: the Bussman fuse in 1986 at McGuire and Catawba-(see CNS LERs -

p 414/89-001 and 413/89-015). These failures prompted Design Engineering to a Q

-identify suitable replacements for all Class 1E applications. Design Study d CNDS-064: determined that the acceptable replacement fuse was the Littlefuse type 1

FLQ which was best suited for harsh environments. Design Engineering and-I' Nuclear Production initially recognized that all FNA fuses should be replaced.

_ Corrective actions taken as a result of _ the previous events included the planned

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a changeout of all'Bussman FNA fuses on both Units. The decision was made by Station Management' to postpone completion of- the FNA fuse changeouts until the

/ Unit 1 E004 Refueling Outage. Prior to this incident, the A-39 FNA fuse was 1 inspected on a monthly basis to visually verify the condition of the fuse, per

,e, Standing Work Request 7866 SWR. '

) This incident has a-contributing cause of management deficiency, due to the T Shift Supervisor not directing that further immediate investigation be performed

' after the bulb replacement was unsuccessful. After it was_ determined that a failed bulb was not the cause, more timely investigation into the cause and consequences of the reset light indication was warranted. 'As a corrective action, a review of Control Room indications and controls will be conducted to

.J determine if licensed Operators have received proper training, and have a good understanding of the functions of controls and gauges.

The Performance PT was performed as per procedure. Work Request 51777 OPS was 1 discussed between the Performance Technician and the CR0 prior to the start of 4

the PT. At that time, the main concern was that the reset light was not functioning. No inoperability had been declared prior to the start of the PT.

CORRECTIVE ACTION

SUBSEQUENT H 1) A work request was initiated to I/R the SM PORV Reset Trn A light.

2) Work request priority was upgraded to 2X following failed stroke time o test on ISV-1, u a l 8 9

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3) A-39 FNA fuse was replaced in cabinet 1EATC12.

- 4) A work request was initiated to replace the A-39 FNA fuse with the

Y -required FLQ fuse.

I PLANNED x

? -1) A systematic review of Control Room indications and controls will be 4 ' conducted to determine if Operators have received proper training and have good understanding of the function of~ controls and gauges (see LER 414/89-020, Planned Corrective Action No. 8.)

SAFi!TY ANALYSIS - j The S/G block valve (ISV25B) for 1SV1 was closed per PT/1/A/4200/31 at the time of the failure of ISV1 to automatically close upon an SSPS signal. Therefore, j no steag release occurred and steamline pressure was unaffected.

Each S/G has one PORV mounted on the main steam line upstream of the Main Steam

• Isolation Valves (MSIVs) for each steam line. The normal- and non-safety related

" function of these valves is to automatically open at approximately 1125 psig 4 steam pressure, thereby reducing steam pressure and preventing challenges to the-

-- main steam code safety valves, and automatically close at approximately 1092 psig steam pressure. This occurs upon steam pressure transients such as may be  ;

', induced by a Turbine trip or Unit runback. This portion of the PORV controls j

was unaffected by the fuse failure and the normal controls would have closed q L 1SV1; therefore, the ability of the PORVs to respond in this manner was not i degraded.

l The safety related function of the S/G PORVs is to open via manual pushbutton control by the Operator, from the Main Control Board, to mitigate the  !

consequences of a postulated S/G U-Tube rupture concurrent with Loss of Off-site  !

Power. This is accomplished by the safety related portion of the PORV controls,  !

which employs independent nitrogen supplies with solenoids and controllers powered by class 1E (essential) circuits. This portion of the PORV controls was j not affected by the fuse failure. Therefore, the ability of the S/G PORVs to j mitigate the consequences of a postulated S/G U-tube rupture event was unaffected and could have been accomplished if needed.

The fuse failure would- have caused the inability of S/G PORVs ISV1, 7,13, and  :

19, to close upon a Main Steam Isolation signal via the SSPS train A logic had they been open. The Main Steam Isolation signal exists to mitigate the consequences of a cooldown event by closing the MSIVs. During the period of time in which the fuse failure caused inoperability of the automatic PORV train A closure logic, we may conservatively assume that a single S/G PORV inadvertently opens and fails to close. This event is fully bounded by the

" Inadvertent Opening of a Steam Generator Relief or Safety Valve" scenario as discussed in Section 15.1.4 of the Catawba FSAR.

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0[0 Ol 6 0F 0l6 In this scenario, no credit is assumed for automatic closure of the single stuck open PORV; i.e., it is' assumed that the PORV failure mode, whether electrical or j 4 mechanical, prevents closure upon Main Steam Isolation. In the analyzed event, j Reactor Coolant System pressure and pressurizer level begin to recover  !

approximately 300 seconds into the event due to safety injection initiation.  !

Proper operation and ability of the PORV to close upon a Main Steam Isolation' i

signal would provide protection beyond what is assumed in the FSAR. It should  ;

be noted that SSPS train B was not affected by the fuse failure and would have functioned properly in response to Main Steam Isolation. Additionally, even

~though it is conservatively not credited in the FSAR, the Operator may also terminate this event by closing the PORV block valves. The Safety Injection  !

Emergency Procedure requires the Operator to observe steam pressure and perform  ;

f. the required isolations to terminate steam pressure decrease.

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$ It is concluded that all safety functions were intact during this event and j

.; would have been accomplished assuming the applicable postulated' worst case ,

accident scenario. The health and safety of the public was not affected by this 4 event.

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