ML20005G109

LER 89-015-01:on 891026,concluded That Transmitter Was Out of Tolerance When Reactor Protection Sys Channel 2 Returned to Operable Status on 890924.Caused by leak-by in Instrument Manifold.Transmitter Recalibr successfully.W/900109 Ltr

ML20005G109
Person / Time
Site:	Davis Besse
Issue date:	01/09/1990
From:	Storz L, Stotz J TOLEDO EDISON CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
BB89-01340, BB89-1340, LER-89-015, LER-89-15, NUDOCS 9001180140
Download: ML20005G109 (4)

Text

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t EDO180N IDISON PLAZA t 330 MADISON AVENUE TOLEDO, OHIO 43052 o301 January 9, 1990 Log No.: BB89-01340 NP33-89-017, Rev. 1 l Docket No. 50-346 l License No. NPF-3 i

t United States Nuclear Regulatory Commission -

Document Control Desk i

Vashington, D. C. 20555 Gentlemen:

LER 89-015, Revision 1 t Davis-Besse Nuclear Power Station, Unit No. 1 l Date of Occurrence - September 24, 1989 Enclosed please find revision 1 to Licensee Event Report 89-015. The revisions are indicated by a revision bar in the left hand margin. Please '

discard or mark superseded any previous copies of this LER.

Yours truly,

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. tun f z Louis F. Storz Plant Manager Davis-Besse Nuclear Power Station LFS/plf Enclosure cct Mr. A. Bert Davis Regional Administrator USNRC Region III Hr. Paul Byron DB-1 NRC Sr. Resident Inspector

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f 4TLt iei Reactor Coolant System Flow Transmitter Erroneously Declared Operabic tytNT Catt (S) Lim NUMeth tst DEPORT Daf t (71 OTMER F ACILITIES INVOLVED ($1 MONTH day ygAq ytAR 8 8,0Q,'b "j[,$ MONTM day vtAR P Acsksty se AMES DOCLET NVMttRt3) 015l01010 I I l ol 4 ?l4 9 o Rla nl1lC n l1 ol1 olo c!n 0 1810 10 1 0 1 l I TMis At*0=T e oveMiTT40 evRouANT TO TMt R40vialMENTs or is CPR li ten.se er m., er eM we.*e> nti

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On October 26, 1989, while reviewing questions raised about activities

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, 1989. 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.  !

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

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011 01 ? oF gh vartn - .n mes mn.m Description of Occurrences ,

Vhile reviewing questions raised about activities associated with an earlier calibration of flov transmitter FTRC01A2, it was concluded that the 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 flow 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 flow transmitter was again declared inoperable and RPS Channel 2 was placed in the tripped condition in accordance with the action statement of Technical Specification 3.3.1.1.

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.

Apparent Cause of Occurrences j

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

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 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.

l The numbers were good for indicated flow with the reactor at 100 percent ,

I power. However, this calibration and evaluation was done with the reactor at i 25 percent power, and the indicated flov input was actually too high for this l power level, i

It is now thought that the zero shift was probably a result of leak-by in the instrument valve manifold which existed during the calibration on September 23, 1989. During the restoration of the transmitter to the RCS flow, valves were repositioned and tightened, and this caused what was seen as the shift.

i.

Analysis of Occurrence Vith the transmitter indicating high, it would have taken RPS Channel 2 longer to sense an RCS flow reduction to the trip setpoint. The other three channels vere operable during this time. The three operable channels provide required automatic protection (2 out of 3) even assuming a single failure under postulated accident conditions. Therefore, there is no safety significance to this finding.

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Ol1 0l 3 0F 0l3 78KT f# msg apsse e asseuw, ens acusanny kmC pain met eth Corrective Action to Prevent Recurrences On October 3, 1989, the transmitter was recalibrated successfully. An

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' engineering review of the process readings was conducted, and the channel was  !

restored to operable. i 1

Personnel who were involved with this event have reviewed the lessons learned.

i Failure Data:  !

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

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

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