ML19256G081

LER 79-114/03L-0:on 791122,RCS Indicated Flow Below Tech Spec Requirements.Cause Undetermined.Flow Transmitter Signal Output Circuits Operating Normally.Actual RCS Flow & Transmitter Calibr Will Be Checked & Tubing Backfilled

ML19256G081
Person / Time
Site:	Davis Besse
Issue date:	12/20/1979
From:	Werner J TOLEDO EDISON CO.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
Shared Package
ML19256G080	List: ML19256G079 ML19256G081
References
LER-79-114-03L, LER-79-114-3L, NUDOCS 7912270398
Download: ML19256G081 (3)

Text

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U.S. NUCLE AR REGULATORY COMMISSION NRC FORM 36G (7-77 ) ~

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

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7 8 t>0 63 COCK ET NUYJER EVENT DESCRIPTION AND PROB ABLE CONSEQUENCES h l

o 2 @n November 22 and 25, 1979 while nerforming surveillance testing, it was discovered

-j o 3 l that Reactor Coolant System (RCS) indicated flow was below the requirement of Tech-o a l nical Specification 3.2.5 which requires a minimum four reactor coolant pump flowrate l s I of 396,880 gpm. There was no danger to the health and safety of the public or to l o

o o l station personnel. More than adequate RCE flow existed at all times since the actual o 7 l thermal power was significantly below 1007. (2772 MUt) during the period of the l

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o e l occurrence. (NP-33-79-132) 00 CAUSE C O*/ P. VALVE SYSTEM CAUSE SUBCODE SUBCODE COMPONENT CODE SUBCOD!

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41 g lx[g 42 lxjg 43 44 xlxlxlxlg 47 33 CAUSE DESCRIPTION AND CORRECTIVE ACTIONS h 1 o l Investigation into the problem has determined that all flow circuits were operating l i i normally and correctly for the flow transmitter signal output. A complete, accurate 1

,,,7, l secondary system heat balance to determine the actual RCS flow will be performed. The; g,g3l l calibration of at least one of the flow transmitters per loop will be checked and l g,,4 ; l the instrument tubing backfilled. 80 7 8 9 oTHER STATUS DiSCOV RY DISCOVERY DESCRIPTION 5  % POWER NA .l B 5099.01 l i s W @ l0 l8 l1 l' @l" '

• l@l Surveillance Test ST 7 8 ACTIVITY CO TENT LOCATION OF RELEASE RELE ASED OF RE LE ASE AYOUNT OF ACTIVITY NA l l1 l6 l l Z l @ [zj@l NA 44 l

45 60 7 8 9 IJ 11 PERSONNEL f xPOSURES NUYBER TYPE DESCRIPTION 1 7 1010l0j@lz @l NA l

,ERSom.Et'iN,unS NUY9ER DESCR 6P TION

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1 x 10 0 0181 NA 1643 249 BJ l

7 8 9 11 12 LOSS OF OR t' AM AGE TO F ACILITY li l 98 l9 l z l@f$$

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7 8 9 10 419-259-5000, Ext. 231 DVR 79-174 NAME OF PREPAHER _

John Werner PHONE.

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TOLEDO EDISON COMPANY DAVIS-BESSE NUCLEAR POWER STATION UNIT ONE SUPPLEMENTAL INFORMATION FOR LER NP-33-79-132 DATE OF EVENT: November 22, 1979 FACILITY: Davis-Besse Unit 1 IDENTIFICATION OF OCCURRENCE:

Reactor Cooiant System (RCS) total indicated flow indicated below specification limit Conditions Prior to Occurrence: The unit was in Mode 1 on November 22, 1979 with 25, 1979 with Power power (MWt) = 2245 and Load (Gross MWe) = 765; and on November (MWt) = 2023 and Load (Gross MWe) = 684.

Description of Occurrence: On November 22, 1979 at about 0300 hours0.00347 days <br />0.0833 hours <br />4.960317e-4 weeks <br />1.1415e-4 months <br /> while performing ST 5099.01, " Miscellaneous Instrument Shif t Checks", it was discovered that RCS in-This value is below the requirement of Technical Speci-dicated flow was 396,000 gpm.

fication 3.2.5 which requires a minimum four reactor coolant pump flowrate of 396,880 gpm, or if not restored within two hours to reduce thermal power to less than 5% of rated thermal power.

Reac-This placed the unit in the action statement of Technical Specification 3.2.5. 5099.01 tor power was reduced to about 73% (684 MWe) and the applicable portion of ST was again performed. Flow was found to be 397,294 gpm which was within Technical Speci-fication 3.2.5.

Again on November 25, 1979 at about 0620 hours0.00718 days <br />0.172 hours <br />0.00103 weeks <br />2.3591e-4 months <br /> while performing ST 5099.01, RCS indi-cated flow was fcund low, out of specification. Power was reduced to 67% (627 MWe) and flow was again checked and found to be within Technical Specification 3.2.5.

Designation of Apoarent Cause of Occurrence: Investigation into the cause of the decrease in the flow indication is continuing at this time.

Analysis of Occurrence:

There was no danger to the health and safety of the public or to station personnel. More than adequate RCS flow existed at all times since the actual thermal power was significantly below 100% (2772 MWt) during the period of this occurrence.

Corrective Actian: On November 22, 1979 under work request IC-58-ll-79, Reactor Protection System Channel 3 was placed in test and the RCS flow circuitry checked and found within specifications with test signals. All loop flow inputs to the Reactor Protection System wcne checked and various computer points for total flow were verified to operate properly and were found to be consistent with each other.

All reactor coolant pump motor voltages and currents were checked and found to be at their normal values.

LER #79-114 1643 250

TOLEDO EDISON COMPANY DAVIS-BES3E NUCLEAR POWER STATION UNIT ONE SUPPLEMENTAL INFORMATION FOR LER NP-33-79-132 PAGE 2 Af ter reviewing past records, it was observed that loop 1 RCS flow was less than 1%

lower than previous values and loop 2 flow was 2-3% lower than previous values. All four loop 2 flow transmitter outputs were then checked and found to be producing the same flow signal. When compared to alignment data the loop 2 flow transmitter voltages were at the value expected for the flow indicated. It was concluded that all flow circuits were operating normally and correctly for the flow transmitter signal output. The loop 2 flow gentile tube was examined by a B&W technical repre-sentative with the aid of a boroscope but no obvious defects were noted.

Required instrument calibration is currently in progress to perform a complete, accurate secondary system heat balance to determine the actual RCS flow. After RCS fill the calibration of at least one of the flow transmitters per loop will be checked and the instrument tubing backfilled to insure no gases are trapped in the tubing or in the gentile internals, prior to the unit returning to power operation.

Failure Data: There have been no previous occurrences of a low RCS flow.

LER #79-114 1643 251