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TENNESSEE VALLEY AUTHORITY

6N 38A Lookout Place,

Chattanooga, Tennessee 37402-2801*

March 23, 1990-

U.S. Nuclear Regulatory ConanassionWashington, D.C. 20555

Attention Document Control Desk

Gentlement

TENNESSEE VALLEY AUTHORITY - SEQUOYAH NUCLEAR PLANT UNIT 1 - DOCKET NO.50-327 - FACILITY OPERATING LICENSE DPR-77 - LICENSEE EVENT REPORT (LER)50-327/90004 '

The enclosed LER provides details of an event wherein two handswitchescontrolling isolation valves on the steam supply line to the Unit 1turbine-driven auxiliary feedwater pump were found mispositioned. This' eventis being reported in accordance with 10 CFR 50.73, paragraph a.2.ii.B.

Very truly yours,

TENNESSEE VALLEY AUTHORITY

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R. Bynum, ce PresidentNuclear Power Production

Enclosurecc (Enclosure):

INPO Records CenterInstitute of Nuclear Power Operations1100 Circle 75 Parkway, Suite 1500Atlanta, Georgia 30339

NRC Resident InspectorSequoyah Nuclear Plant2600 Igou Ferry RoadSoddy Daisy Tennessee 37379

Regional AdministrationU.S. Nuclear Regulatory CommissionOffice of Inspection and EnforcementRegion II101 Marietta Street, Suite 2900Atlanta, Georgia 30323

9003290003 900323 I

.PDR ADOCK 050003273 FDC 1

An Equal Opportunity Employer

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At 0935 Eastern standard time (EST) on February 21, 1990, with both Units at 100-percentpower, it was discovered that two handswitches controlling the operation of isolationvalves on the steam supply line to the Unit I turbine-driven auxiliary feedwater pump(TDAFWP) were in the manual position. In this position, the isolation valves would noth;ve automatically closed upon high temperature detection in the TDAFWP room. Thisconfiguration was not bounded by the current environmental analysis for the TDAFWProom. Upon discovery, the unit operator placed the handswitches in the P-auto positioncnd verified the equivalent Unit 2 handswitches were in the correct postion. The exacttime at which the handswitches became mispositioned could not be determined nor couldthe root cause of the event be determined. The handswitches were last verified to be inthe P-auto position at 0700 EST on February 21, 1990. It is believed that thehandswitches were inaovertently pushed in to the manual position between 0700 and0935 EST, as the result of someone leaning against the control panel or placing aprocedure on top of the panel. As corrective action, the event will be discussed withlicensed operators by March 30, 1990.

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Description of Event

At 0935 Eastern standard time (EST) on February 21, 1990, with both Units 1 and 2 inMode 1 (100-percent power, 2.235 pounds per square inch gauge, 578 degrees Fahrenheit),it was discovered that Handswitches 1-HS-1-17 and 1-HS-1-18 (EIIS Code HS) were in themanual position (pushed in). These handswitches control operation of Valves 1-FCV-1-17cnd 1-FCV-1-18, respectively. These valves (EIIS Code ISV) are the series isolationvalves on the main steam supply line to the Unit 1 turbine-driven auxiliary feedwater ;

pump (TDAWP) (EIIS Codes P and BA). The normal position of these handswitches is theP-auto position. The isolation valves were opent hence, there was no TDA NP operabilityc:ncern. However, with the handswitches in the manual position, the isolation valves ;

w:uld not have automatically closed upon- high temperature detection in the TDAWP room. *

This configuration was not bounded by the current environmental analysis for the TDAWPr om and surrounding areas in the auxiliary building. Upon discovery of thehandswitches being in the manual position, the unit operator immediately placed thehandswitches in the P-auto position. The equivalent handswitches on Unit 2 were thenvarified to be in the correct position. The subject handswitches are located in thehorseshoe area on Control Panel 1-M-4 immediately behind the handrail at the front of '

the panel.

The exact time at which the handswitches i.ecame mispositioned has not been determined.The handswitches were last verified to be in the P-auto position for the 0700 EST,Fr.bruary 21, 1990, performance of Administrative Instruction (AI) 5, " Shift and ReliefTurnover, Appendix B2." This AI appendix is a status checklist of vital systemsp riormed each shift by the oncoming shift unit operator. Previous enctming shifts hadclso verified the handswitches to be in the P-auto position for AI-5, Appendix B2,parformances.

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B3 tween 0700 and 0935 EST, there were a limited number of personnel in the horseshoecrea. Access to the horseshoe area is administrative 1y controlled by AI-30. " NuclearPlant Conduct of Operation," with permission from the unit operator or assistant shiftoperations supervisor required for entry. Aside from operating shift personnel, threeparsons are known to have entered the horseshoe area in the timeframe in question. Twot:chnical report writers were in the vicinity of Panel 1-M-4 walking down newly preparedprocedures prior to their implementation. The technical report writers performedcctivities such as verifying annunciator window labels and control equipmentn:menclature for 15 procedures between approximately 0850 and 0945 EST. In statementscbtained following this event, both technical report writers indicated they did nottcuch any controls, did not lay any procedures on the control panels, and did not leanceross the control panel handrail at any time. The third nonoperator known to havecntered the horseshoe area was the auxiliary feedwater (AFW) system engineer, who begana routine visual inspection of AFW system instrumentation and controls at approximately0930 EST. It was during the course of this inspection that the system engineer noticedthe subject handswitches were in the manual position and immediately notified the unitoperator.

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cause of Event

The root cause of this event could not be determined with certainty. An investigationw s conducted that included obtaining statements from personnel on duty at the time of I

the event and follow-up interviews with the unit operators, technical report writers,cnd the system engineer involved. A review was also conducted of AI-5. Appendix B2, ;

packages performed during February. This review found the valves had been consistentlysigned off as being in the P-auto position. Performances of surveillance testing during i

Fcbruary that manipulated the subject handswitches were also reviewed. The valves were ;

cgain left in the P-auto position. In addition, maintenance requests that wereperformed in the TDAFWP room during February were reviewed. No work was identified thatwould have required the subject handswitches to be placed in the manual position.H:nce, the investigation could not positively determine how or when the handswitches

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'w:re mispositioned. However, it is believed that the handswitches were inadvertentlypushed in to the manual position between 0700 and 0935 EST on February 21, 1990, as ther sult of someone leaning against the control panel or placing a procedure on top of the j

panel. The preponderance of evidence obtained during the investigation indicates that I

the handswitches were in the P-auto position prior to that time. ||

Analysis of Event'

This event is being reported in accordance with 10 CFR 50.73, paragraph a.2.ii.B. as acondition that was outside the design basis of the plant. NRC was notified of the event ;

by telephone call at 1156 EST on February 21, 1990, in accordance with 10 CFR 50.72,paragraph b.1.ii.A, as an unanalyzed condition that significantly compromised plantsafety. After further review, it has been determined that the event should be morecppropriately reported as a condition outside the design basis of the plant. The designintent of the subject isolation valves is to automatically close upon detecting adownstream TDAFWP supply line break. The current environmental analysis for the TDAFWP i

room takes credit for automatic isolation of steam flow into the pump room upond tection of high temperature in the room during a postulated steam supply line break.Defeating the automatic isolation feature (by having the isolation valve handswitches inmanual) would result in an increased time required to mitigate the event throughoperator action, which would allow more mass and energy to be released than presentlycnalyzed. This would result in more severe environmental conditions in the TDAFWP roomthan in the current analysis. In addition, the effects of this steam line break might

[ no longer be limited to the TDAFWP room, and additional areas of the auxiliary buildingi could require analysis to define new environmental conditions for equipment

qualification. In accordance with the guidance of NRC Generic 1.etter 88-07, anycquipment subject to these new conditions would have to be considered unqualified until[

| cdequate documentation could be developed to establish that the equipment would perform( its intended function in the relevant environment. Consequently, this event is

considered to have represented a condition outside the design basis of the plant.| However, because the mispositioned handswitchris were detected and correctly repositionedI promptly (within few hours at most), the duration of any increased risk was minimal.

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Corrective Action

The immediate action taken was to place the two Unit I handswitches in the P-autoposition and verify the equivalent Unit 2 handswitches were in the correct position.B:cause the root cause of the event could not be determined with certainty, no specificp3rsonnel actions have been taken. However, this event will be discussed with licensed

cperators by March 30, 1990.

Additional Information

No previous events could be identified that reported mispositioning of the TDAFWP steamsupply isolation valve handswitches. There is, however, a limited similarity betweenthis event and a violation cited in Inspection Report 50-327, 328/88-20 concerning thehindswitch for a centrifugal charging pump being incorrectly positioned in thepull-to-lock position. In this case, the handswitch was purposely placed in thepull-to-lock position, but was not identified to or by the oncoming shif t during theshift turnover process. One of the corrective actions taken in response to thisvioletion was a revision to AI-5 to strengthen the main control room shift turnoverprocess by including a control board walkdown by the oncoming shift operationscupervisor and requiring completion of the appropriate appendix checklist (such asAppendix B2, depending on operating mode) by the unit operator. It is, in part, becauseof the effectiveness of this corrective action that such a high level of confidenceexists that the handswitches discussed in this LER were in the P-auto positio.1 at shiftturnover on February 21, 1990.

Commitment

This event will be discussed with licensed operators by March 30, 1990.

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