ML19332D311

LER 89-015-00:on 890924,RCS Flow Transmitter Out of Tolerance When Reactor Protection Sys Channel 2 Returned to Operable Status.Caused by leak-by in Instrument Manifold Seen as Zero Shift.Transmitter recalibr.W/891127 Ltr

ML19332D311
Person / Time
Site:	Davis Besse
Issue date:	11/27/1989
From:	Storz L, Stotz J TOLEDO EDISON CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
LER-89-015, NP-33-89-017, NUDOCS 8911300343
Download: ML19332D311 (4)

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Neon EDISDN PLAZA r 300 MADISON AVENUE November 27, 1989 tottoo, GHto 436520301 j Log No.: BB89-01255 -

NP33-89-017 j Docket No. 50-346 ,

License No. NPF-3 t

United States Nuclear Regulatory Commission l Document Control Desk Vashington, D. C. 20555 Gentlement LER 89-015 l Davis-Besse Nuclear Power Station, Unit No. 1  :

Date of Occurrence - September 24, 1989 +

Enclosed Licensee Event Report 89-015 which is being provided in accordance with 10CTR50.73(a)(2)(i) to provide written notification of the subject occurrence. ,

Yours truly,

-M(

Louis F. Storz Plant Manager ,

Davis-Besse Nuclear Power Station l LFS/p1f Enclosure cci Mr. A. Bert Davis Regional Administrator ^

USNRC Region III Mr. Paul Byron  ;

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UCENSEE EVENT CEPORT (LER)

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associated with the calibration of FTRC01A2, it was concluded that the transmitter was out of tolerance when RPS Channel 2 was returned to operable status on September 24, *,989. RPS Channel 2 was inoperable for about 38 hours4.398148e-4 days <br />0.0106 hours <br />6.283069e-5 weeks <br />1.4459e-5 months <br /> ,

without satisfying the action statement of Technical Specification 3.3.1.1.

The most probable cause of the calibration problem was a leak-by in the instrument manifold that was incorrectly seen as a zero shift. Consequently, when the transmitter was valved back into the RCS flow process and the equalizing valve tightened, the transmitter output was erroneously high.

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l' On October 3, 1989, the transmitter was recalibrated successfully. An-engineering review of the process readings vas conducted and the channel restored to operable. Individuals involved have reviewed the incident and results for lessons learned.

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While reviewing questions raised about activities associated with an earlier calibration of flow transmitter FTRC01A2, it was concluded that the I transmitter was in fact inoperable when declared operable on September 24, 1989, at 0502 hours0.00581 days <br />0.139 hours <br />8.300265e-4 weeks <br />1.91011e-4 months <br />. FTRC01A2 senses Reactor Coolant System (RCS-AB) Loop 2 Hot Leg flov and inputs to Reactor Protection System (RPS-JC) Channel 2. The calibration had been performed with the reactor at 25 percent power. On September 25, 1989, at 1412 hours0.0163 days <br />0.392 hours <br />0.00233 weeks <br />5.37266e-4 months <br />, with the reactor at 100 percent full power, the flov transmitter was again declared inoperable and RPS Channel 2 vas placed in the tripped condition in accordance with the action statement.of Technical Specification 3.3.1.1.

t on October 26, 1989, the review concluded that there was firm evidence that the transmitter had been inoperable for approximately 38 hours4.398148e-4 days <br />0.0106 hours <br />6.283069e-5 weeks <br />1.4459e-5 months <br /> without the action statement of Technical Specification 3.3.1.1. being satisfied. This is reportable under 10CFR50.73(a)(2)(1)(B) as a condition prohibited by Technical Specifications.

l Apparent Cause of Occurrences

! The cause of returning the transmitter to an operable status when it was actually inoperable was personnel error when evaluating the transmitter output data.

l On September 23, 1989, work vas initiated to replace FTRC01A2 which had drifted high and had been previously declared inoperable. A new transmitter was installed and calibrated using Plant Procedure DB-MI-03062, Channel Cal of l FTRC01A2. During this process, the transmitter was thought to be experiencing l a zero' shift. After completion of the string calibration, restoration was completed and the RCS flow input to RPS Channel 2 was evaluated as acceptable.

The numbers were good for indicated flow vith the reactor at 100 percent power. However, this calibration and evaluation was done with the reactor at l 25 percent power, and the indicated flov input was actually too high for this power level. ,

l It is now thought that the zero shift was probably a result of leak-by

in the instruhlent valve manifold which existed during the calibration on September 23, 1989. During the restoration of the transmitter to the RCS flov, valves were repositioned and tightened, and this caused what was seen as the shift.

Analysis of Occurrence Vith the transmitter indicating high, it would have taken RPS Channel 2 longer to sense en RCS flow reduction to the trip setpoint. Although technically inoperable, it vould have provided some degree of protection. The other three l channels vere operable during this time and would have provided protection but

with less redundancy. Therefore, there is little safety significance to this l finding.

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on October 3, 1989, the transmitter was recalibrated successfully. An i engineering review of the process readings was conducted, and the channel was  !

restored to operable. 1 Personnel who were involved with this event have reviewed the lessons learned.  ;

Failure Datat .

Although there have been previous flov transmitter failures, this is the first which has led to an LER since 1983. ,

REPORT NO.: NP33-89-017 PCAO NO.: 89-0517  !

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