ML20012C427

LER 90-003-00:on 900211,inadvertent Containment Vent Isolation Occurred.Caused by Lack of Attention to Detail in That Operator Did Not Look Closely Enough at Switch Designations.Personnel Involved counseled.W/900312 Ltr

ML20012C427
Person / Time
Site:	Sequoyah
Issue date:	03/12/1990
From:	Bynum J, Hipp G TENNESSEE VALLEY AUTHORITY
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
LER-90-003-01, LER-90-3-1, NUDOCS 9003210270
Download: ML20012C427 (4)

Text

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, % I ' 'f TENNESSEE VALLEY AUTHORITY

', Chattanooga, Tennessee 6N 38A Lookout-Place March 12, 1990-U.S. Nuclear Regulattery Commission ATTN: Document Control Desk Washington, D.C. 20555 Gentlemen:

TENNESSEE VALLEY AUTHORITY - SEQUOYAH NUCLEAR PLANT UNIT 2 - DOCKET NO.

328 - FACILITY OPERATING LICENSE DPR LICENSEE EVENT REPORT (LER) 4 50-328/90003 s

The enclosed LER provides details of an event wherein an inadvertent containment vent isolation occurred on Unit 2 as a result of a lack of attention to detail by a reactor operator. This event is being reported in accordance with 10 CFR 50.73, paragraph a.2.1.v.

Very truly yours.

TENNESSEE VALLEY AUTHORITY R. Bynum .Vice President  !

uclear Power Production Enclosure cc (Enclosure):

Regional Administration

U.S. Nuclear Regulatory Commission ,

Office of Inspection and Enforcement }

Region II. l 101 Marietta Street, Suite 2900 Atlanta, Georgia 30323 INPO Records Center Institute of Nuclear Power Operations  !

1100 Circle 75 Parkway, Suite 1500 Atlanta, Georgia' 30339 NRC Resident '1spector Sequoyah Nuclear Plant 2600 Igou Ferry Road Soddy Daisy, Tennessee 37379  ;

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l An Equal Opportunity Employer l

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F ACILITV NAME til DOCRaf NUMBE R (2) PAGE G S;quoyah Nuclear Plant, Unit 2 0 l6 l 010 l 013 l 2 l8 1 l0F!013

'"Inadvertant containment vent isolation event resulting from a lack of attention to >

dstail while blocking a radiation monitor tVtNT DATE (St LER NUMetRqsl REPORT DAf t 171 OTHER F ACILITEt$ INVOLVED 18)

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CAUSE OY ST E M COMPONENT yFAC g TONPR S CAUSE COMPONENT TO NPA 1 1 I I I I I I I I I I I I I I I I I I I I I I I l I I SUPPLEMENT AL REPORT EXPtCTED 114) MONTH DLv VIAR YES (19 v.s. comer.n EX9tCTED SUOMI53 TON DA rts f NO l l l t..mCTu-........,.-.--<.~,...,..,(i.,

On February 11, 1990, with both Unit I and Unit 2 at 100-percent power, an (nadvertent containment vent isolation (CVI) occurred on Unit 2. The reactor operators were preparing to purge containment, a process that includes source checking the containment vsnt exhaust radiation monitors to ensure operability. While attempting to block these Unit 2 radiation monitors prior to source checking, the equivalent Unit i radiation monitors were blocked instead. Consequently, when one of the Unit 2 radiation monitors w s source checked, a CVI was initiated. After determining the cause of the CVI, the op2rators initiated actions to recover from the CVI after which the containmeat purge wIs conducted. The root cause of this event has been attributed to a lack of attention to detail in that the operator did not look closely enough at the switch designations whsn blocking the containment purge radiation monitors. A contributing cause of the svant was that communication between the operators regarding which radiation monitors to block was not conducted in accordance with the established procedure. As correctivo action, the personnel involved have been counselled regarding the event and the importance of proper conduct of operation. In addition, this event has been placed in a training letter for distribution to licensed personnel.

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. Description of Event At 1246 Eastern standard time on February 11, 1990, with both Unit 1 and Unit 2 in Mode 1 (100-percent power, 2,235 pounds per square inch gauge, 578 degrees Fahrenheit),

an inadvertent B train containment vent isolation (CVI) (EIIS Code JM) occurred on Unit 2. The Unit 2 reactor operators (R0s) had been preparing to purge containment using Surveillance Instruction 410.2, " Containment (Upper, Lower) Purge." In preparation, the Unit 2 auxiliary building assistant unit operator (AUO) was verifying that radiation monitors (EIIS Code IL) 2-RM-90-130 and -131 were properly aligned to monitor the containment purge air exhaust using System Operating Instruction 90.1,

" Radiation Monitoring System." While the AUO was manipulating valves during this slignment, the 2-RM-90-130/131 instrument malfunction alarm annunciatst. as the result of a low flow condition The Unit 1 lead R0 acknowledged the alarm at Panel 0-M-12 and immediately notified the Unit 2 R0s of the alarm. (Panel 0-M-12 is closer'to the Unit 1 horseshoe than to the Unit 2 horseshoe.) Because of concern that a CVI might result from the AUO's clignment actions on Radiation Monitors 2-RM-90-130 and -131, the Unit 2 R0s directed the Unit 1 RO, who was still by Panel 0-M-12 to block the two radiation monitors. This operation requires turning two handswitches (HS-90-136Al and -136A2) clockwise to the appropriate radiation monitor position and pulling out the switches to eccomplish the blocking function. Tht. Unit 1 RO turned the switches to what he thought ware the Unit 2 containment purge radiation monitor (2-FM-90-130 and -131) positions, but which were in fact the equivalent Unit I radiation monitor positions (1-RM-90-130 and -131). When the Unit 1 RO completed the blocking process, he informed the Unit 2 R0s that the radiation monitors were blocked.

The Unit 2 R0s continued with the preparations to purge Unit 2 contcinment. Believing that Radiation Monitars 2-RM-90-130 and -131 had been blocked, the Unit 2 R0s directad the AU0 to source check the radiation monitors to ensure operability as required by SI-410.2. When the source check was performed on Radiation Monitor 2-RM-90-131, a high radiation alarm was received, and a B train CVI was initiated on Unit 2. Upon investigating the cause of the CVI, the Unit 1 RO discovered the incorrect radiation monitors had been blocked. The Unit 2 operator immediately reset the high radiation signal and initiated actions to recover from the CVI. After completing the CVI recovery, the alignment of the Unit 2 containment purge radiation monitors was raverified, 2nd the containment purge was initiated.

Cruse of Event The root cause of this event has been attributed to a lack of attentioa to detail in that the Unit 1 R0 did not look closely enough at the switch designations when blocking the containment purge radiation monitors. As a consequence, the Unit 2 radiation monitors were not blocked, which resulted in a CVI when one monitor was source checked.

A contributing caust of the event was that communication between the Unit 1 and the Unit 2 R0s was not conducted in accordance with Administrative Instruction 30, " Nuclear Plant Conduct of Operation." Repeat back and closed loop communication was not utilized in sufficient detail. The unit designation of the radiation monitors was not explicitly stated between the operators. If the words " Unit 2" had been communicated back and forth, it is poadible the Unit 1 RO might have caught his error before the CVI occurred.

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0l0 0 l3 OF 0 l3 n muow,wau w.a.u=ea*r m ac w m nim An51ysis of Event This event is being reported in accordance with 10 CFR 50.73, paragraph a.2.1.v. as an cngineered safety feature (ESP) actuation that was not part of a preplanned sequence.

Ths containment purge ventila*: ion system is described in Section 9.4.7 of the SQN Updated Final Safety Analysis Report (UFSAR). The containment purge exhaust radiation

- monitors are described in Section 11.4.2.2.6 of the UFSAR.

Upon receipt of the CVI signal, the equipment required to actuate on a CVI signal parformed as desig;ned. Following the CVI, Operations personnel verified that an actual high radiation condition did not exist and took appropriate actions to recover from the CVI. If Unit i had been purging containment, the potential consequence of the intdvertent blocking of the Unit 1 containment purge exhaust radiation monitors could have been a radiological release that would normally have been detected and stopped by tha purge exhaust monitors. The probability of an extended release is minimal for two rcasons: (1) 1-RM-90-106 (lower containment) and -112 (upper containment) were still opsrable and would have initiated a CVI if a high radiation condition had exis;ed inside containnant, and (2) the alarm circuits were still functional on 1-RM-90-130 and -131 end would have alerted the control room operators of any high radiation condition in the purge exhaust. However, because Unit l was not purging containment and Unit 2 ESF equipment operated as designed, it can be concluded that there were to adverse consequences to the health and safety of plant personnel or the general public as a rsoult of this event.

Corrective Action The immediate action taken was to determine the cause of the CVI and to initiate actions for r;ecovery from-the CVI. As corrective action to prevent recurrence, the shift opsrations supervisor and the personnel involved have been counselled by the Operations Mar.ager regarding the event and the importance of proper conduct of operation. In eddition, this event has bean placed in a training letter for distribution to licensed parsonnel.

Additional Information There have been 50 previously reported occurrences of CVIs at SQN since 1984 Of these prsvious occurrences, 14 were the result of personnel errors that most frequently occurred during maintenance activities. No previous occurrences could be identified that'resulted froto blocking the incorrect radiation monitor.

Commitment None.

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