ML20028G920

LER 90-020-00:on 900829,ventilation Sys Inoperable Due to Train B Diesel Generator Out of Svc.Caused by Stuck Microswitch Contacts on Pressure Switch 0-PS-311-172. Pressure Switch Adjusted & Returned to svc.W/900926 Ltr

ML20028G920
Person / Time
Site:	Sequoyah
Issue date:	09/26/1990
From:	Bynum J, Whittemore C TENNESSEE VALLEY AUTHORITY
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
LER-90-020, LER-90-20, NUDOCS 9010030244
Download: ML20028G920 (5)

Text

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TENNESSEE VALLEY AUTHORITY '

6N 38A Lookout Place, Chattanooga, Tennessee 37402-2801

't September 26, 1990 i U.S. Nuclear Regulatory Commission ATTN - Document Control Desk Washington, D.C. 20555 Gentlemen I TENNESSEE VALLEY AUTHORITY - SEQUOYAH NUCLEAR PLANT UNIT 1 - DOCKET NO.- I 50-327 - FACILITY OPERATING LICENSE DPR LICENSEE EVENT REPORT (LER) 50-327/90020 )

The enclosed LER provides details concerning an entry into Limiting Conditions J for Operation 3.0.5 and 3.7.7 when both trains of the main control room emergency ventilation system were declared inoperable. The B train diesel i generator was out of service for maintenance when the A train of the main control room air handling unit failed to start because of a malfunctioning _

pressure switch.

This event is being reported in accordance with 10 CFR 50.73(a)(2)(1)(B) as an operation prohibited by the plant's technical specifications.

Very truly yours.

I TENNESSEE VALLEY AUTHORITY-

=:

. R. Bynum, Vice President.

Nuclear Operations

Enclosure:

l ccL(Enclosure):

Mr. J..N.' Donohew, Project Manager U.S. Nuclear Regulatory Commission l One White Flint, North' 11555 Rockville Pike Rockville, Maryland- 20852 1

INPO Records Center  !

Institute of Nuclear Power Operations q 1100 Circle 751 Parkway, Suite 1500 Atlanta, Georgia. 30339 NRC Resident Inspector Sequoyah Nuclear Plant 2600-Igou Ferry Road Soddy Daisy,' Tennessee 37379 g Mr. B. A. Wilson, Project Chief L U.S. Nuclear Regulatory Commission

-Region II f,

101'Marietta Street, NW, Suite 2900

-Atlanta, Georgia :30323 Q' ' Q Ij ggg

[ 9010030244 900926 W \

\

E PDR ADOCK 05000327; An Equal Opportunity Employer S PNUr

y-NRC Form 366 U.S. NUCLEAR REGULATORY COMMIS$10N Approved OMB No. _

3150-0104 a (6J89)- Empir:s 4/30/92

E N E M NT M T (L W r .

FACILITY NAME (1) lDOCKETNUMBER(2)lPAGE(3)

Seouovah Nuclear Plant. Unit 1 1015l0101013 12 17 lil0Fl 01 4 TITLE (4) Control room emergency ventilation system was inoperable due to the B train diesel generator being out of service for maintenance and the A train main control room air handlina unit faillna to start EVENT DAY (5) l LER NUMDER (6) l REPORT DATE (7) l OTHER FACILITIES INVOLVED (8) l l l l l$EQUENTIALl l REVISION l l l l FACILITY NAMES lDOCKETNUMBER(S)

MONTHl DAY lYEAR lYEAR I l NUMBER I i NUMBER lMONTHl DAY lYEAR l Seaeovah. Unit 2 1015101010131218 l l l l_I l_l l 1 l i I 01 81 21 91 91 01 91 01 ! 0 l 2 Ml I 0 1 0 1 01 91 21 61 91 01 10151010101 1 1 OPERATING l lTHl$ REPORT IS W ulTTED PURSUANT TO THE REQUIREMENTS OF 10 CFR %:

H00E l l (Check ote or i:m 3f the f e11owina)(11)

(9) I 11 l20.402(b) !_l20.405(c) l_l50.73(a)(2)(iv) l_l73.71(b)

POWER l l_l20.405(a)(1)(1) l_l50.36(c)(1) l_l50.73(a)(2)(v) l l73.71(c)

LEVEL l l_l20.40S(a)(1)(11) l_l50.'36(c)(2) l_l50.73(a)(2)(vii) l_l0THER(Specifyin (10) 1 0! 91 91 l20.405(a)(1)(iii)lKXl50.73(a)(2)(i) l_l50.73(a)(2)(viii)(A) l Abstract below and in l_l20.405(a)(1)(iv) l_l50.73(a)(2)(ii) l_l50.73(a)(2)(viii)(B)l Text. NRC Form 366A) l 120.405(a)(1)(v) l 150.73(a)(2)(iii) l 150.73(a)(2)(x) l LICENSEE CONTACT FOR THIS LER (12)

NAME l TELEPHONE NUMBER lAREACODEl C. H. Whittemore. Comollance Licensino I61115l8I4l3l-l7l2l1 10 COMPLETE ONE LINE r0R EACH COMPONENT FAILURE DESCRIBED IN THIS REPORT (13) l l l l REPORTABLE l l l l l l REPORTABLE l CAUSElSYSTEMl COMPONENT lMANUFACTURERl TO NPRDS I ICAUSElSYSTEMI COMPONENT IMANUFACTURERI TO NPRDS I I l l l 1 I i  ! I I I I I I I l l l l I i1 1 I I l l l l l l l l l l l ,

I I I I l l l l l 1 l FH l 31 1 l IlbilS$1 Wl DI 21 41 9 l NO l l l l l l l l l l l l  ! l SUPPLEHCNTAL REPORT EXPECTED (14) l EXPECTED lMONTHlDAY l YEAR l_ l SUBMISSION l l l

_l YES (If ves. comolete EXPECTED SUBMISSION DATE) l X l NO I DATE (15) l l l I l l ABSTRACT (Limit to 1400 spaces, i.e.. approximately fif teen single-space typewritten lines) (16)

On August 29, 1990, at 0935 Eastern daylight time (EDT) with Unit 1 in Mode 1 at 99.5 percent power and Unit 2 in Mode 1 at 72.2 percent power, Limiting Conditions for Operations (LCOs) 3.0.5 and 3.7.7 were entered when both trains of the control room emergency ventilation systems (CREVS) were declared inoperable. The 1B-B emergency diesel generator (D/G) was out of service for scheduled surveillance-and maintenance activities when the A train main control room (MCR) air handling unit (AIIU), which is attendant equipment for the control room emergency ventilation system failed to start.

Operations' personnel directed expedient return to service of the 1B-B D/G and directed l

immediate troubleshooting activities on the A train MCR AliU. Maintenance's personnel determined the root cause of the AHU failing to start to be a pressure switch with contacts stuck closed. The pressure switch was adjusted and calibrated. The AHU operated properly when tested and was returned to service. LCOs 3.0.5 and 3.7.7 were exited at 1355 EDT on August 29, 1990.

l l

l HRC Form 366(6-89)

s! NR'C form 366A 'O.$. NUCLEAR REGULATORY COMMIS$10N Approved OMB No. 3150-0104 (6289) Expires 4/30/92 bb b b h iEXT CONTINUATION FACILITY NAME (1) lDOCKETNUMBER(2) l LER NUMBER (6)- 1 l PAGE.(3) l l l l$EQUENTIALl l REVISION l l l l l Sequoyah Nuclear. Plant Unit 1 l lYEAR l l NUMBER 'l l NUMBER l l l l l l 101510101013 12 17 19 10 l - l 0 l 2 1 0 1 - 1 0 l 0 1 01 210Fl 01 4 TEXT (If more space is required, use additional NRC form 366A's) (17)

Dey ription of Event 01 August 29, 1990, at 0935 Eastern daylight time-(EDT) with Unit 1 in Mode 1 (79.5 percent power, 2,235 pounds per square inch gauge [psig], and 578 degrees  !

Fahrenheit (F]) and Unit 2 in Mode 1 (72.2 percent power, 2,235 psig, and 568 degrees l

'r') in a coastdown in preparation for the Unit 2 Cycle 4 (U2C4) refueling-outage, Limiting Conditions for Operations (LCOs) 3.0.5 and 3.7.7 were entered when both trains of the control room emergency ventilation systems (CREVS) were declared inoperable. l l

The main control room habitability system (MCRHS) (EIIS Code UG) is designed to provide a safe location for operators to perform their respective duties during accidents and 3 normal operations. The MCRHS has redundant equipment trains. One feature of the MCRHS T is the CREVS (EIIS Code VI), which operates during a main control room (MCR) isolation. The MCR air handling units (AHUs) are attendant equipment for the CREVS and are required to be operable during accidents and normal operations. The AHUs are i safety-related equipment and are aligned with their respective trains of CREVS during '

-testing of the MCRHS. On August 26, 1990, the B train MCR AHU had an alarm indicating' l trouble in the system. The operating A train MCR AHU was shut down, and B train MCR AHU was placed in service to allow personnel to troubleshoot the alarm. When B train was started, the alarm cleared on B train and the identical alarm on A train annunciated. The-dec b ion was made to leave B train in operation and place A train in

l. standby and begin researching the reason for the alarm on A train. Technical l Specification LCO 3.7.7 requires with one train operable, to restore the inoperable l

system to operable status within seven days.

L On August 29, 1990, Maintenance personnel performed preventative maintenance (PM) 54,

!- which is a monthly PM to check the condition of the normal air filters in the MCR i

AHUs. This PM checks and records the pressure differential across the filters. The reading-for the B train AHU filters was 0.05 inches of water gauge, which is below the required value for filter changeout. However, the instruction also allows the filters to be changed out at the discretion of the craft. It was decided to change out the filteis. The B train AHUs were stopped, and the swapover to the A train was

-unsuccessfull because the A train failed to start. Operations attempted to restart the A train MCR AHU several times, but was unsuccessful. When these efforts failed, the shift operations supervisor declared the A train inoperable, and LCOs 3.7.7 and-3.0.5-H were entered. Technical Specification LCO 3.7.7 requires with one train operable, to  ;

restore the inoperable system to operable status within seven days. LCO 3.0.5 was  ;

j -entered because the emergency power supply for the B train AHU was out of service. On L August 29,-1990. the 1B-B diesel generator (D/G) (EIIS Code EK) had been removed from service for periodic maintenance activities to be performed, resulting in the B train l AHU being declared inoperable. Operations personnel directed expedient return to l service of the 1B-B D/G and directed immediate troubleshooting activities of the  !

A train AHU. -

l INRCform 366(6-89)

R  :- - - _ _ _ - _ _ _ _ _ _ _ _ - _ _ _ - -

7 1

W ,

c4 NRC Form 366A U.S. NUCLEAR REGULATORY COMMIS$10N Approved OMB No. 3150-0104 (6*89) Expires 4/30/92 W EN E EE NT R M RT M TEXT CONTINUATION FACILITY NAME (1) lDOCFfNUMBER(2)l LER NUMBER (6) l I PAGE (3) l l l l$EQUENTIALl l REVISION l l l l l Sequoyah Nuclear Plant Unit 1 l lYEAR l 1 NUMBER I l NUMBER l l l l l 101510101013 12 17 19 10 l- l 0 1 2 1 0 l--I 0 1 0 1 01 310Fl 01 4 TEXT (If more space is required, use additional NRC Form 366A's) (17)

Troubleshooting centered around Pressure Switch 0-PS-311-172 (EIIS Code PIS).- When the AHU did not start, the breaker was found in a tripped position. The breaker was reset and again tripped. The craftsman, suspecting the pressure switch had stuck contacts, tapped the pressure switch and then verified the AHU would start without tripping the breaker. Instrument Maintenance found that the pressure switch was also out of calibration. The reason for the pressure switch being out of calibration is indeterminate. The pressure switch has a history of being found out of calibration.

While the as-found calibration of the pressure switch did not prevent it from performing its function, a CAQR was initiated to determine the proper corrective action for the poor performance of this switch. The switch was recalibrated and cycled several times during this activity to veriff operability. The reason for the stuck contact is indeterminate. As a precautionary measure, a work request (WR) was initiated to replace the pressure switch at a later date. Operations declared the

'A train MCR AHU operable and exited LCOs 3.0.5 and 3.7.7 at 1335 EDT on August 29, 1990. The pressure switch is installed to detect a freon leak in the chiller and freon piping. Freon is an asphyxiant, and the pressure switch is installed for personnel safety.

Cause of Event The cause of the entry into LCO 3.0.5 was the failure of the A train MCR AHU to start concurrently with the B train emergency power supply out of service. The root cause of the A train MCR AHU failing to start was a pressure switch (0-PS-311-172) with stuck microswitch contacts. The reason for the stuck contact is indeterminate.

Analysis of Event This event is being reported in accordance with 10 CFR 50.73(a)(2)(1)(B) as an operation prohibited by the plant's technical specifications. The MCRHS is designed to i

provide a safe location for personnel controlling plant operations during normal operations and during and following accidents. There are two 100-percent redundant l equipment trains for the MCRHS, Train A and Train B. One feature of the MCRHS is the l CREVS. During MCR isolation, the CREVS supplies a limited amount of outside air for pressurizing the MCR to at least one-eighth inch water gauge positive pressure. The MCR AHUs are attendant equipment for the CREVS to ensure the one-eighth inch water gauge positive pressure is maintained. The AHUs are safety-related and aligned with their respective train of CREVS during testing of the MCRHS.

In this event although Train B of CREVS was administrative 1y declared inoperable because of the 1B-B D/G being out of service for routine maintenance and testing, offsite power was available and it is expected that Train B of CREVS would have been able to perform its designated function if it had been required. Accordingly, there were no adverse safety consequences associated with this event.

NRC form 366(6-89)

i.

NitC {orm*366A - U.$. NUCLEAR REGULATORY COMMIS$104 Approved OMB No. 3150-0104-(6189) Expires 4/30/92 LMNHEMNTREMI(LER)

TEXT CONTINUATION FACILITY NAME (1) lDOCKETNUMBER(2)l LIR.NUNCER f6) l l PAGE (3) l l l.lSEQUENilAtl l REVISION l l } l l Sequoyah Nuclear Plant Unit l' l' lYEAR l I NUMBER l l NUMBER l l l l l 10151010!013 12 17 19 10 1 - 1 0 1 2 1 0 1--! O l 0 1 01 410rl 01 4 TEXT (If more space is required, use additional NRC Form 366A's) (17)

Corrective Action Maintenance's persor.nel immediately began to troubleshoot the failure of Train A MCR

'AHU,to start. The.cause of.the failure was determined to be a pressure switch with hn stuck contacts. The pressure switch was adjusted, calibrated, and ths AHU returned to service. A WR (C003888) has been written to replace the press're u switih. Condition Adverse to Quality Report SQP-900363 has been initiated to determine the correct'.*;e action for the poor performance of this particular pressure switch and to determine if

.other similar pressure switches have the same performance problem.

J Additional Ir. formation A review of LERs and previous event raports indicated one similar event. LER 327/88011 concerned LCO 3.0.5 entry caused by removal of a D/G from service when the opposite i train of_CREVS was out of service. Although similar, the previous LER was the result I of knowingly removing a-D/G from service with the opposite train of CREVS inoperable.

In the August 29, 1990, event, the D/G was already out of service, and the failure of the' opposite train of MCR AHU to start"during the swapover could not have been foreseen. Therefore, the only similarity in the two events is the equipment involved in the 3.0.5 entry.

j Commitments '!

None.

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{ -NRC Form 366(6-89)

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