ML20012D861

LER 90-004-00:on 900221,handswitches Controlling Operation of Isolation Valves on Steam Supply Line to Auxiliary Feedwater Pump Found in Manual Position.Cause Undetermined. Handswitches Placed in P-auto position.W/900323 Ltr

ML20012D861
Person / Time
Site:	Sequoyah
Issue date:	03/23/1990
From:	Bynum J, Hipp G TENNESSEE VALLEY AUTHORITY
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
LER-90-004, LER-90-4, NUDOCS 9003290003
Download: ML20012D861 (5)

Text

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• TENNESSEE VALLEY AUTHORITY

, 6N 38A Lookout Place Chattanooga, Tennessee 37402-2801 March 23, 1990 U.S. Nuclear Regulatory Conanassion Washington, D.C. 20555 Attention Document Control Desk Gentlement TENNESSEE VALLEY AUTHORITY - SEQUOYAH NUCLEAR PLANT UNIT 1 - DOCKET NO.

50-327 - FACILITY OPERATING LICENSE DPR LICENSEE EVENT REPORT (LER) 50-327/90004 '

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

Very truly yours, TENNESSEE VALLEY AUTHORITY su - i R. Bynum, ce President Nuclear Power Production Enclosure cc (Enclosure):

INPO Records Center Institute of Nuclear Power Operations 1100 Circle 75 Parkway, Suite 1500 Atlanta, Georgia 30339 NRC Resident Inspector Sequoyah Nuclear Plant 2600 Igou Ferry Road Soddy Daisy Tennessee 37379 Regional Administration U.S. Nuclear Regulatory Commission Office of Inspection and Enforcement Region II 101 Marietta Street, Suite 2900 Atlanta, Georgia 30323 9003290003 900323 I

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$Vtuit$$ON YES III res remo,ete L APECTED SV0 MISSION DATRI NO l l l An ut CT to ,, ,, , m . . . .,,,,. , ,,, . , <, ,,,, ,,,,,, nie, At 0935 Eastern standard time (EST) on February 21, 1990, with both Units at 100-percent power, it was discovered that two handswitches controlling the operation of isolation valves 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 not h;ve automatically closed upon high temperature detection in the TDAFWP room. This configuration was not bounded by the current environmental analysis for the TDAFWP room. Upon discovery, the unit operator placed the handswitches in the P-auto position cnd verified the equivalent Unit 2 handswitches were in the correct postion. The exact time at which the handswitches became mispositioned could not be determined nor could the root cause of the event be determined. The handswitches were last verified to be in the P-auto position at 0700 EST on February 21, 1990. It is believed that the handswitches were inaovertently pushed in to the manual position between 0700 and 0935 EST, as the result of someone leaning against the control panel or placing a procedure on top of the panel. As corrective action, the event will be discussed with licensed 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 in Mode 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 the manual position (pushed in). These handswitches control operation of Valves 1-FCV-1-17 cnd 1-FCV-1-18, respectively. These valves (EIIS Code ISV) are the series isolation valves 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 the P-auto position. The isolation valves were opent hence, there was no TDA NP operability c: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 TDAWP r om and surrounding areas in the auxiliary building. Upon discovery of the handswitches being in the manual position, the unit operator immediately placed the handswitches in the P-auto position. The equivalent handswitches on Unit 2 were then varified to be in the correct position. The subject handswitches are located in the horseshoe 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 Relief Turnover, Appendix B2." This AI appendix is a status checklist of vital systems p riormed each shift by the oncoming shift unit operator. Previous enctming shifts had clso verified the handswitches to be in the P-auto position for AI-5, Appendix B2, parformances. ,

B3 tween 0700 and 0935 EST, there were a limited number of personnel in the horseshoe crea. Access to the horseshoe area is administrative 1y controlled by AI-30. " Nuclear Plant Conduct of Operation," with permission from the unit operator or assistant shift operations supervisor required for entry. Aside from operating shift personnel, three parsons are known to have entered the horseshoe area in the timeframe in question. Two t:chnical report writers were in the vicinity of Panel 1-M-4 walking down newly prepared procedures prior to their implementation. The technical report writers performed cctivities such as verifying annunciator window labels and control equipment n:menclature for 15 procedures between approximately 0850 and 0945 EST. In statements cbtained following this event, both technical report writers indicated they did not tcuch any controls, did not lay any procedures on the control panels, and did not lean ceross the control panel handrail at any time. The third nonoperator known to have cntered the horseshoe area was the auxiliary feedwater (AFW) system engineer, who began a routine visual inspection of AFW system instrumentation and controls at approximately 0930 EST. It was during the course of this inspection that the system engineer noticed the subject handswitches were in the manual position and immediately notified the unit operator.

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0l 0 0l 3 0F 0l4 text u, . < ec w,,,asuv nn cause of Event The root cause of this event could not be determined with certainty. An investigation w 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 consistently signed 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 were performed in the TDAFWP room during February were reviewed. No work was identified that would 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 ,

w:re mispositioned. However, it is believed that the handswitches were inadvertently '

pushed in to the manual position between 0700 and 0935 EST on February 21, 1990, as the r 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. l l

Analysis of Event This event is being reported in accordance with 10 CFR 50.73, paragraph a.2.ii.B. as a condition 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 plant safety. After further review, it has been determined that the event should be more cppropriately reported as a condition outside the design basis of the plant. The design intent of the subject isolation valves is to automatically close upon detecting a downstream 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 upon d 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 in manual) would result in an increased time required to mitigate the event through operator action, which would allow more mass and energy to be released than presently cnalyzed. This would result in more severe environmental conditions in the TDAFWP room than in the current analysis. In addition, the effects of this steam line break might

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no longer be limited to the TDAFWP room, and additional areas of the auxiliary building i could require analysis to define new environmental conditions for equipment qualification. In accordance with the guidance of NRC Generic 1.etter 88-07, any

[ cquipment subject to these new conditions would have to be considered unqualified until l 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.

l However, because the mispositioned handswitchris were detected and correctly repositioned I

promptly (within few hours at most), the duration of any increased risk was minimal.

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0l 0 0l4 OF 0l4 rixt u = . . w ,==c s an4 w on Corrective Action The immediate action taken was to place the two Unit I handswitches in the P-auto position 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 specific p3rsonnel 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 steam supply isolation valve handswitches. There is, however, a limited similarity between this event and a violation cited in Inspection Report 50-327, 328/88-20 concerning the hindswitch for a centrifugal charging pump being incorrectly positioned in the pull-to-lock position. In this case, the handswitch was purposely placed in the pull-to-lock position, but was not identified to or by the oncoming shif t during the shift turnover process. One of the corrective actions taken in response to this violetion was a revision to AI-5 to strengthen the main control room shift turnover process by including a control board walkdown by the oncoming shift operations cupervisor and requiring completion of the appropriate appendix checklist (such as Appendix B2, depending on operating mode) by the unit operator. It is, in part, because of the effectiveness of this corrective action that such a high level of confidence exists that the handswitches discussed in this LER were in the P-auto positio.1 at shift turnover on February 21, 1990.

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

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