ML19327C242

LER 89-025-00:on 891006,channel in power-range Nuclear Instrumentation Improperly Calibr,Rendering Channel Inoperable.Caused by Inadequate Technician Training.Maint Qualification Program developed.W/891113 Ltr

ML19327C242
Person / Time
Site:	South Texas
Issue date:	11/13/1989
From:	Ayala C, Chewning R HOUSTON LIGHTING & POWER CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
LER-89-025, LER-89-25, ST-HL-AE-3291, NUDOCS 8911210286
Download: ML19327C242 (6)

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The Light company P llouston. Texas 77001 _(713) 228 9211 Houston Lighting & Power --._._ _,. . . .~ ... _.O. . , _Ilox

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. . _ _ , _ . . , _ . _ . _ _ _ _ . _ , . . . . . j November 13, 1989 ST-HL-AE- 3291 r File No.: G26 10CFP50.73 .

L I- U. S. Nuclear Regulatory Commission Attention: Document Control Desk Washington, DC 20555 South Texas Project Electric Generating Station Unit 2 ,

Docket No. STN 50-499 Licensee Event Report 89-025 Regarding Technical Specification Violation Due to Failure to Properly Calibrate Power Range Nuclear Instrumentation Pursuant to 10CFR50.73, Houston Lighting & Power (HL&P) submits the attached Licensee Event Report 89-025 regarding a Technical Specification  ;

violation due to the failure to properly calibrate power range nuclear instrumentation. This event did not have any adverse impact on the health and safety of the public. ,

If you should have any questions on this matter, please contact Mr. C. A. Ayala at (512) 972-8628.

R. W. Chewnin Vice President #

Nuclear Operations RWC/BEM/n1 f I .

Attachment:

LER 89-025, South Texas, Unit 2 l

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I llouston 1.ighting & Power Cosupany ST-HL- AE- 3291 File No.: G26 Page 2 r .

CCl l Regional Administrator, Region IV Rufus S. Scott Nuclear Regulatory Commission Associate General Counsel 611 Ryan Plaza Drive, Suite 1000 Houston Lighting & Power Company Arlington, TX 76011 P. O. Box 1700 Houston, TX 77001 George Dick, Proj ect Manager U. S. Nuclear Regulatory Commission INFO Washington, DC 20555 Records Center l

1100 Circle 75 Parkway J. I. Tapia Atlanta, GA 30339-3064 Senior Resident Inspector c/o U. S. Nucletar Regulatory Commission Dr. Joseph H. Hendrie P. O. Box 910 50 Be11 port Lane Bay City, TX 77414 Be11 port, NY 11713

j. J. R. Newman,-Esquire D. K. Lacker  !

'Newman & Holtzinger, P.C. Bureau of Radiation Control i 1615 L Street, N.W. Texas Department of Health l Washington, DC 20036 1100 West 49th Street '

Austin, TX 78756-3189 R. L. Range /R. P. Verret Central Power & Light Company P. O. Box 2121 Corpus Christi, TX 78403 R. John Miner (2 copies)  ;

Chief Operating Officer City of Austin Electric Utility l 721 Barton Springs Road l Austin, TX 78704 R. J. Costello/M. T. Hardt City Public Service Board i P. O. Box 1771 s San Antonio, TX 78296 Revised 10/30/89 NL.DIST

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A ufRACT m , e. ,a M.,e. ... - ,. - - ,A, .,4 On October 6, 1989, Unit 2 was in Mode 1 at 100 percent power. At approximately 1406 hours0.0163 days <br />0.391 hours <br />0.00232 weeks <br />5.34983e-4 months <br />, during the performance of power range nuclear l Instrumentation calibrations, one channel was incorrectly calibrated. This  ;

condition, which rendered the channel inoperable, was not discovered until approximately 2340 hours0.0271 days <br />0.65 hours <br />0.00387 weeks <br />8.9037e-4 months <br />. Failure to place the inoperable channel in the tripped condition within six hours of its becoming inoperable is a violation ,

of Technical Specification 3.3.1. The cause of this event was the assignment j of a technician to perform the calibration who was not adequately trained. In addition, no means existi.d to confirm that the calibration was correct. A Maintenance Qualification Program has been developed to ensure that only qualified individuals will be assigned to perform specific maintenance tasks.

A method to verify that the power range nuclear instrumentation is properly calibrated will be incorporated in the appropriate procedures.

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On October 6, 1989, Unit 2 was in Mode 1 at 100 percent power. During the j performance of power range nuclear instrumentation calibrations, one channel  !

was incorrectly calibrated. This condition, which rendered the channel inoperable, was not discovered for approximately nine hours. Failure to place the channel in the tripped condition within six hours of its becoming inoperable is a violation of Technical Specification 3.3.1. This event was i determined to be reportable on October 13, 1989 and the NRC was notified at I

1520 hours0.0176 days <br />0.422 hours <br />0.00251 weeks <br />5.7836e-4 months <br />.

On October 5, 1989, Incore-Excore nuclear instrumentation measurements were performed in accordance with Technical Specifications to determine the target axial flux difference and new excore power range monitor calibration i parameters at 92 Effective Full Power Days. At approximately 0703 hours0.00814 days <br />0.195 hours <br />0.00116 weeks <br />2.674915e-4 months <br /> on October 6, 1989, recalibration of excore power range monitors was commenced to optimize the axial flux difference outputs to the new parameters. Upon ,

completion of power range channel NI-41 recalibration at approximately 1406 {

hours, it was observed to indicate an axial flux difference of approximately 5 i percent areater than the other power range channel indicators. Personnel performing the test concluded that since the indication was within the axial flux difference target range, and the redundant channels remained to be optimized, there was no reason to suspect any error in the channel. At 1542 l tours,' channel NI-42 was removed from service far recalibration to its new parameters. When completed at approximately 1900 hours0.022 days <br />0.528 hours <br />0.00314 weeks <br />7.2295e-4 months <br />, this indicated an  ;

axial flux difference approximately 5 percent less than channel NI-41. At l 2054 hours0.0238 days <br />0.571 hours <br />0.0034 weeks <br />7.81547e-4 months <br />, a second recalibration of the channel NI-42 was performed to determine which of the two channels was in error. At approximately 2340 l'

hours, the channel NI-42 was verified correct and channel NI-41 was declared inoperable.  !

During recalibration of channel NI-41, technicians discovered that a calibration error had occurred during a critical initial step of the calibration procedure which acccunted for the observed difference between the two power range channels. The calibration error was corrected. No other values were found out of tolerance and the channel was returned to service at 0228 hours0.00264 days <br />0.0633 hours <br />3.769841e-4 weeks <br />8.6754e-5 months <br /> on October 7, 1989. The HL&P technician who performed the initini calibration had previous experience with other power range instrumentation calibrations, however, he had not performed this calibration in the past. The surveillance procedure was properly followed and has been determined to be adequate for properly trained individuals.

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DESCRIPTION OF EVENT Cont Most calibrations are verified to be correct by comparing the output of the calibrated chennel to a redundant, operable channel. Power r.snge nuclear instrumentation is configured such that each channel monitors a different quadrant of the reactor core. Therefore, when new parameters are entered, a comparison of a calibrated channel to other channels is not valid for determining operability. At the time this calibration was performed, no means existed to verify the accuracy of the calibrated channel which prevented Operations and Maintenance personnel from determining if the calibration had been performed correctly.

CAUSE OF EVENT:

The cause of this event was improper calibration of the excore power range nuclear instrument channel due to inadequate training of the maintenance technician who was assigned to perform the calibration. This problem was not immediately detected because the calibration procedure did not provide a means to verify that the calibration was performed correctly.

ANALYSIS OF EVENT:

Each power range nuclear instrumentation channel provideo an input to the respective overtemperature delta temperature input to the Reactor Trip System.

Technical Specification 3.3.1 allows power operation to continue with one channel inoperable provided the channel is tripped within six hours. During this event, power operation continued from 1406 hours0.0163 days <br />0.391 hours <br />0.00232 weeks <br />5.34983e-4 months <br /> to 2340 hours0.0271 days <br />0.65 hours <br />0.00387 weeks <br />8.9037e-4 months <br /> on -

October 6, 1989 with channel NI-41 set nonconservatively, but not tripped.

At least two channels of power range nuclear instrumentation remained operable throughout this event.

Operation prohibited by Technical Specifications is reportable pursuant to 10CFR50.73(a)(2)(1)(B). This event did not have any adverse impact on the health and safety of the public.

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CORRECTIVE ACTION:

The following corrective actions are being taken as a result of this event:

1. HL&P has developed a Maintenance Qualification Program which will ensure that only qualifled individuals will be assigned to perform specific maintenance tasks. .This program is currently scheduled to be implemented on December 1, 1989.

2. A method to verify that the power range nuclear instrumentation le properly calibrated has been incorporated in the appropriate procedures.  !

ADDITIONAL INFORMATION:

There have been no previous events reported regardinF improper calibration of nuclear instrumentation which caused Technical Specification violations.

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