ML20042E202

LER 90-005-00:on 900315,inadvertent Containment Vent Isolation Occurred While Preparing to Purge Containment. Caused by Lack of Attention to Detail by Operator.Operator Counseled & Received Administrative reprimand.W/900413 Ltr

ML20042E202
Person / Time
Site:	Sequoyah
Issue date:	04/13/1990
From:	Bynum J, Hipp G TENNESSEE VALLEY AUTHORITY
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
LER-90-005, LER-90-5, NUDOCS 9004200402
Download: ML20042E202 (5)

Text

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.t TENNESSEE VALLEY AUTHORITY t

6N 38A Lookout Place' i Chattanooga, Tennessee 37402-2801 April 13 -1990  ;

i U.S. Nuclear Regulatory Comission

. ATTN: Document Control Desk Washington, D.C. 20555 ,

t i Gentlemen TENNESSEE VALLEY AUTHORITY - SEQUOYAH NUCLEAR PLANT UNIT'2 DOCKET NO. -

50-328 - FACILITY OPERATING LICENSE DPR LICENSEE EVENT REPORT-(LER) 50-328/90005 ,

The enclosed'LER provides' details of an event wherein an inadvertent I containment vent isolation occurred-on Unit 2 as a result of a lack of '

attention to detail by.a reactor operator. This event is beir.g reported in accordance with 10 CFR 50.73. paragraph (a)(2)(iv).

Very truly yours, i

TENNESSEE VALLEY AUTHORITY i m-h.R.Bynum, Ace President Nuclear Power Production .

Enclosure

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INPO Records Center Institute of Nuclear Power Operations 1100 Circle 75 Parkway, Suite 1500 Atlanta, Ceorgia 30339 NRC Resident Inspector i Sequoyah Nuclear Plant 2600 Igou Ferry Road '

Soddy Daisy, Tennessee 37379 Regional Administration ,

U.S. Nuclear Regulatory Commissicn  ;

Office of Inspection and Enforcetent '

Region II 101 Marietta Street, Suite 2900 l Atlanta, Georgia 30323 g,

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AHTuCT wei,se n....,...~,.,,, ,, ,,,-,...,ne On March 15, 1990, with Unit 1 at 85 percent power and Unit 2 at 100 perceht ponr. an

( inidvertent containment vent isolation (CVI) occurred on Unit 2 while preparing to purge containment. While attempting to block a Unit 2 radiation monitor before performing a satpoint change an operator blocked the corresponding Unit i radiation monitor.

Consequently, during performance of the actpoint change, a Unit 2 CVI occurred. After determining the cause of the CVI..the operators recovered from the CVI and continued

! preparing to purge containment. The root cause of this event has been attributed to a l

icek of attention to detail in that the operator did not look closely enough at the switch designations when blocking the containment purge radiation monitor. As corrective action, the personnel involved have been counselled regarding the event, and ths involved operator has received an appropriate administrative reprimand. The involved operator and his immediate supervisor will discuss this event with other licensed personnel during shift turnover meetings and/or requalification training. In cddition, new backplate labels are being installed on the handswitches that control blocking for the radiation monitors to improve the clarity of unit designation.

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nxw a. wNac w as,mtm Description of Event i At 1353 Eastern standard time (EST) on March 15, 1990, with Unit 1 in Mode 1 (85 percent power, 2,235 pounds per square inch gauge [psig], 573 degrees Fahrenheit [F)) and Unit 2 in Mode 1 (100 percent power, 2,235 psig, 578 degrees F), an inadvertent B train c:ntainment vent isolation (CVI) (EIIS Code JM) occurred on Unit 2 while preparing to ,

purge containment. Surveillance Instruction (SI) 410.2, " Containment (Upper, Lower) i Purge," was in progress, which directed a setpoint change be performed on the '

containment purge Radiation Monitors (EIIS Code IL) 2-RM-90-130 and -131. The instrument mechanics (IMs) were performing SI-291.3, " Readjustment of Setpoints for R diation Monitors with Variable Setpoints and Block Functions," to adjust the radiation monitor setpoints. Radiation Monitor 2-RM-90-130 had been blocked, and the setpoint cdjustment had been completed. The IMs then notified the Unit 1 balance of plant (BOP) '

cperator to unblock 2-RM-90-130 and block 2-RM-90-131. (The Unit 1 BOP operator has-  !

r:sponsibility for manipulating both Unit 1 and Unit 2 radiation monitor block handswitches, which are mounted closer to the Unit 1 horseshoe than to the Unit 2 horseshoe.) The BOP operator unblocked 2-RM-90-130 with Handswitch 0-HS-90-136Al and th:n turned Handswitch 0-HS-90-136A2 to what he thought was the position to block 2-RM-90-131. In fact, the BOP operator had misread the switch designation and had '

blocked the Unit 1 B train containment purge radiation monitor (1-RM-90-131). The BOP optrator then informod the IMs that 2-RM-90-131 was blocked. When the hign radiation satpoint was reached during the ensuing setpoint adjustment, the radiation monitor gsnerated a CVI initiation signal as designed. However, because the radiation monitor >

w:s not blocked, an inadvertent B train CVI occurred on Unit 2. As a design function of th) CVI, the isolation valves for the containment lower and upper compartment area i monitors (2-RM-90-106 and -112) closed. Consequently, Limiting Condition for Operations (LCO) 3.3.3.1 (radiation monitoring instrumentation), LCO 3.4.6.1 (reactor coolant system leakage detection), and LC0 3.3.2 (engineered safety features actuation system instrumentation) were entered at 1353 EST. .

Upon investigating the cause of the CVI, the BOP operator discovered the incorrect rcdiation monitor had been biccked. The Unit 2 operators reset the high radiation '

signal on 2-RM-90-131 and initiated System Operating Instruction (SOI) 88.1, "C ntainment Isolation System," to realign the system to its normal configuration and to rcopen the isolation valves for 2-RM-90-106 and -112. At 1355 EST, LCOs 3.3.3.1, 3.4.6.1, and 3.3.2 were exited. Preparations to purge containment were resumed and at 1510 EST, the Unit 2 operators initiated a lower containment purge using the B train fcns.

C use of Event i Th3 root cause of this event has been attributed to a lack of attention to detail in that the Unit 1 BOP operator did not look closely enough at the switch designations when j ettempting to block Radiation Monitor 2-RM-90-131. As a consequence, the correct rcdiation monitor was not blocked, which resulted in a CVI when the high radiation setpoint was adjusted.

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This event is being reported in accordance with 10 CFR 50.73, paragraph (a)(2)(iv), as cn engineered safety feature (EST) actuation that was not part of a preplanned s quence. The containment purge ventilation system is described in Section 9.4.7 of the i 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.  !

s Upon receipt of the CVI signal, the equipment required to actuate on a CVI signal performed as designed. 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 1 had been purging containment using the B train fans at the time of the _

cvent, the potential consequence of the inadvertent blocking of the Unit 1 B train l ctntainment purge exhaust radiation monitor (1-RM-90-131) could have been a radiological '

release that would normally have been detected and stopped by the purge exhaust monitor. The probability of an extended release is minimal for two reasons:

(1) 1-RM-90-106 (lower containment) and -112 (upper containment) were still operable and would have initiated a CVI if a high radiation condition had existed inside containmentI cnd (2) the alarm circuit was still functional on 1-RM-90-131 and would have alerted the control room operators of any high radiation condition in the purge exhaust. However, b cause Unit I was not purging containment and Unit 2 ESF equipment operated as d3 signed, it can be concluded that there were no adverse consequences to the health and  ;

s:fety of plant personnel or the general public as a result of this event.

Corrective Action The immediate action taken was to determine the cause of the CVI and to initiate actions for recovery from the CVI. As corrective action to prevent recurrence, the shift operations supervisor and the personnel involved have been counselled by Operations management regarding the event and the importance of proper conduct of operations. In cddition, the BOP operator involved has received an appropriate administrative r0primand. This event is the second CVI at SQN to result from blocking an incorrect rediation monitor. LER 50-328/90003 reported a similar_ event that occurred on F2bruary 11, 1990. Corrective actions implemented as a' result of the February 11 event included counselling of involved personnel and review of the event in a training letter distributed to .1.icensed personnel. The BOP operator in the March 15 event was not involved in the February 11 event, but had received the training letter reviewing the Fcbruary 11 event. Because of the similarity of the two events. TVA has reviewed the cvents collectively and has developed two further corrective actions:

1. The BOP operator involved and hfs immediate supervisor will discuss this event with other licensed personnel during shift turnover meetings and/or requalification training. This communication technique is expected to yield additional effectiveness through peer involvement. This action will be completed by July 1, 1990.

2. New backplate labels are being installed on Handowitches 0-HS-90-136Al and -136A2.

These handswitches control blocking for Train A and B radiation monitors, respectively. The new backplate labels improve the clarity of unit designation for the radiation monitors.

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j Additional Information i There has been one previously submitted LER reporting a CVI at SQN that resulted from ,

blocking the incorrect radiation monitor, as previously discussed.

Conanitment The BOP operator involved and his immediate supervisor will discuss this event with other licensed personnel during shift turnover meetings and/or requalification training. This action will be completed by July 1, 1990.

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