ML19270H044

LER 79-062/03L-0 on 790521:automatic Feedwater Suction Pressure Switches Found Outside Specified Tolerance.Caused by Instrument Drift & Component Failure.Switches Returned to Normal Tolerances on 790522

ML19270H044
Person / Time
Site:	Davis Besse
Issue date:	06/15/1979
From:	Hitchens D, Nelson J TOLEDO EDISON CO.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
Shared Package
ML19270H037	List: ML19270H036 ML19270H044
References
L79-506, LER-79-062-03L, LER-79-62-3L, NUDOCS 7906220403
Download: ML19270H044 (5)

Text

U. S. NUCLE AR REGUL ATORY COMMISSION NRC FORM JUG I7 72)

LICENSEE EVENT REPORT l l l l l (PLEASE PRINT OR TYPE ALL REQUIRED INFORMATION)

CONTROL BLOCK: l l 1

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1 8 9 l 0 l H ] D l B l S l 1 l@l LICENSE LICENSEE CODE 14 15

@ l 0%7.hH l - l 0 l 0 l N ] PLICENSE 25 26 l F TYPE l- lJ00 l 3 l@[ 4l 1l 1l 57 G T 58 CON'T

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3[gc l L lgl 0 l 5 l 0 l- l 0 l 3 l 4 l 6 64 69 Q]EVENT O lDATE5 l 2 l1 l 7 l 9REPORT 14 7S l@lDATE 016 l80ll 5 l 7 l 9 l I 8 00 61 DOCKET NUV0E R EVENT DESCRIPTION AND PROBABLE CONSEQUENCES h suction pressure switches PSL107C. PSL4928B.]

o 2 l On 5/21/79, the auxiliary feedwater (AFW) and the pressure setooints of PSL4929A. PSL4929BJ o 3 l and PSL4930A were found inoperable,

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The station o 4 I and PSL4931A were discovered to be outside of the specified tolerances.

l l o I s l l was in Mode 5 at the time of occurrence and throughout the corrective action. At no of either AFW l o c l time would the above combinations of f ailures have caused inoperability the_ health and_ safety of the public or station per- l loj7j ltrains. There was no danger to I

o a jsonnel. (NP-33-79-64)

COMP. V ALV E SYSTEM CAUSE CAUSE SUBCOD6 SUBCODE CODE SU3 CODE COMPONENT CODE CoOE fit 618 I c I n l@ LE_j@ lE lh l Il Nl Sl Tl Rl Ulh l S lh W h 33 18 19 20 REVISION 9 10 11 12 7 OCCURRENCE REFORT SE QUE N TI AL No, CODE TYPE REPoR T No.

LER _. EVENT YE AR l0l6l2l y l0l3l lL l l-l l 0l h gEg'RO l7 l9 22l [._J 23 24 26 27 28 2'1 Ju 31 32

_ 21 A fER MA HoVHS S B i TED FO ? b B. SUPPLI KEN A G oN FL *T T Ch l Sl 3l 8 247 lg bhl Zlh 33 34 l35 Zlh dh 36 3l1 DI Ol 6l 40Ol 41 l2N lg 4 l43Al@ 44 27 CAUSE DESCRIPTION AND CORRECTIVE ACTIONS causes of the inoperability.

i o 1 Component failure and instrument drift are the apparent li j i j i Further investigation of the root cause of the failure will be conducted when the cauilp-i acnt is returned to operation. On 5/22/79, the pressure switches were returned within

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i 3 l tolerance or replaced. The frequency of the testing will be increased to determine li14j l the required calibration f requency. 80 7 8 9 IS HY DISCovEHY DESCRIPTION

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D TOLEDO EDISON COMPANY DAVIS-BESSE NUCLEAR POWER STATION UNIT ONE SUPPLEMENTAL INFORMATION FOR LER NP-33-79-64 DATE OF EVENT: thy 21,1979 FACILITY: Davis-Besse Unit 1 IDENTIFICATION OF OCCURRENCE: Failure of Auxiliary Feedwater (AFW) Suction Pres-sure Switches Conditions Prior to Occurrence: The unit was in Mode 5, with Power (MWT) = 0, and Load (Gross MWE) = 0. Description of Occurrence: During performance of Maintenance Work Order IC-269-79 on May 21, 1979 to satisfy surveillance requirements of Technical Specification 4.7.1.2.d, it was discovered that the Auxiliary Feedwater (AFW) suction pressure switches PSL-107C, PSL-4928B, and PSL-4930A would not actuate to their desired positions. In addition, during performance of this same maintenance work order, it was discovered that the AFU suction pressure switches PSL-4929A, PSL-4929B, and PSL-4931 A would actuate at a pressure below the specified tolerances. Specific All of information on each pressure switch is provided on the attached tabulation. the switches were manufactured by Static-O-Ring, model numbers 12V2-E4-TTLLX3 and 6V2-ES-TTX4. The station was in Mode 5 at the time of the occurrence and throughout the correc-tive action. This incident is being reported as documentation of a component failure. Designation of Apparent Cause of Occurrence: The cause of the occurrence is component failure possibly thic to vibration of the pressure switches. The three switches which would not actuate, even with 0 psig applied, were removed and a bench calibration was subsc-a t t empted . Although the switches could be adjusted to the required setpoint, quent calibration checks indicated that the actuation setpoint could not be repeated. The setpoints of the remaining three failed switches had drif ted outside of the speci-fled tolerance. The root cause of this occurrence is still under investigation. Analysis of Occurrence: There was no danger to the health and safety of the public or to station personnel. PSL-107C, AFPT #2 Steam Inlet is one of four such switches. The logic behind their actuation is two out of four, and with this switch inoperable, the logic would not have been rendered inoperable. Of the remaining five defective switches, two were associated with AFP #1 suction pressure, and three were associated with AFP #2 suction pressure. On AFP #1, PSL-4928A&B measure "before strainer suction pressure" and PSL-4930A&B measure "after strainer suction pressure". On PSL-4930A&B the logic is such that either the "A" or "B" switch will provide the 2347 293 LER #79-062

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TOLEDO EDISON COMPANY DAVIS-BESSE NUCLEAR POWER STATION UNIT ONE PAGE 2 SUPPLEMENTAL INFORMATION FOR LER NP-33-79-64 i intended safety function. Since PSL-4930B actuated within the specified tol- i On AFP #2, PSL-4929A&B erance, the equipment would have operated as required. measure "before strainer suction pressure" and PSL-4931A&B measurethe "af "B" ter switch strainer suction pressure". In the case oftherefore, PSL 493] A&B switches, the equipment would have per-actuated within its specified tolerance;The "before strainer suction" pressure formed the intended safety function. switches PSL-4929ALB both did actuate, however, PSL-4929A actuated 1.55atpsig 2.47instead psig instead of the minimum allowed 2.8 psig and PSL-4929B actuated at of the minimum allowed 2.8 psig. Therefore, AFP l-1 operation could have been af fected by the defective pressure swi tche s . AFP 1-2 would have operated properly except if the normal condensate tank supply to the AFW Pump 1-2 had failed, the automatic transfer to the service water supply would have transferred at 1.55 psig instead of the minimum allowed 2.8 psig. AFP l-2 would have provided the required supply of feedwater to the steam genera-tors if the normal supply of condensate had failed. Also, the monthly performance of ST 5071.01, "AFW Monthly Test", when the unit was in operation, verified that both AFP suctions were automatically transferred upon a loss of normal condensate supply. Corrective Action: On May 22,1979, PSL-4929A, PSL-4929B, and PSL-4931A were The recalibrated to within tolerance under Maintenance Work Order IC-269-79. remaining three pressure switches PSL-4930A, PSL-4928B, and PSL-107C were replaced Surveillance Test ST 5071.01, " Auxiliary under Maintenance Work Order IC-272-79. Feedwater Monthly Test" will be performed to prove operability of the pressure switches prio'r to the unit startup. A program is being instituted by the Instrument andreturnsControl to section to investigate power operation. In the possibility of vibration effects once the unit addition, until a calibration history on these switches can be determined, the f requency of calibration checks will be increased from once every eighteen months to once every three months. The required calibration frequency will be established from this historical data. This is Failure Data: There have been no previously reported similar occurrences. the first tbac the calibration check has been performed since the setpoints on these switches were established. 2347 294

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LER #79-062

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5o ISCEDIATE AS LEFT h<g SWITCH NAME NUMBER DESIRED SETPOINT AS FOUND READING CORRECTIVE ACTION READING g: enf g mmm AFPT #2 Inlet PSL-107C 9.0 1 1.0 psig would not actuate replaced 9.01 psig ZgE Steam Pressure (decreasing) with 0 psig switch (decreasing) hM8 applied g yZ

                                                                                                    =nn m t"*  o AFP #1 Before        PSL-4928B  3.3 1 0.5 psig   would not actuate  replaced         3.29 psig     @ g ':s Strainer Suction                (decreasing)     with 0 psig        switch           (decreasing)  *y W @

Pressure applied djk o~ z E5

• m AFP #1 Af ter PSL-4930A 1.0 1 0.5 psig would not actuate replaced 1.00 psig oy Strainer Suction (decreasing) with 0 psig switch (decreasing) $

Pressure applied 75* z 7E AFP #2 Before PSL-4929A 3.3 1 0.5 psig 2.47 psig recalibrated 3.33 psig gy Strainer Suction (decreasfag) (decreasing) switch (decreasing) 4a Pressure fM

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AFP #2 Before PSL-4929B 3.3 1 0.5 psig 1.55 psig recalibrated 3.19 psig Strainer Suction (decreasing) (decreasing) switch (decreasing) Pressure AFP #2 After PSL-4931A 1.0 1 0.5 psig would not actuate recalibrated 0.95 psig Strainer Suction (decreasing) with 0 psig switch (decreasing) Pressure applied E

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