ML20084K233
| ML20084K233 | |
| Person / Time | |
|---|---|
| Site: | Quad Cities  |
| Issue date: | 07/29/1974 |
| From: | Kalivianakis N COMMONWEALTH EDISON CO. |
| To: | Oleary J US ATOMIC ENERGY COMMISSION (AEC) |
| Shared Package | |
| ML20084K236 | List: |
| References | |
| AO-50-254-74-23, NJK-74-183, NUDOCS 8305190227 | |
| Download: ML20084K233 (3) | |
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July 29,1974 fir. John F. 0 ' Leary, Di rector Directorate of Licensing Regulation U. 5. Atomic Energy Commission Washington, D. C.
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Reference:
Quad-Cities fluclear Pcuer Station Unit i Docket lio. 50-254, DPR-29, Appendix A Sections 1.0.A.2, 3.2.B, Tab le 3.2.2, and 6.6.B. I.a Ocar dr. 0 ' Leary:
Enclosed please find Abnormal Occurrence Report No. 50-254/74-23 for Quad-Cit les Nuclear Power Stat ion. This was previously reported to Region iII, Di rectorate of Regulatory Operations by telephone en July 20, 1974, and to you and Region li t, Directorate of Regulatory Operations by telecopy on Juiv IG. 1 :J4.
This report is submitted to you in accordance wi th the rcquirements of Techni--
cal Specification 6.6.B.I.a.
Very truly yours, COMONWEALT!! EDIS0il C0tiPANY QUAD-CIT I ES i;UCLEAR POWER STATION
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&fedw-Me N. J. Kalivianakis Station Superintendent NJK/RAR/j eh cc: Region li t, Directorate of Regulatory Operations J. S. Abel
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h,EPORT NUMBER: A0 254/74-23 REPORT DATE: July 29, 1974 OCCURRENCE DATE: July 19, 1974 FACILITY: Quad-Cities Nuclear Power Station Cordova, Illinois 612.42 IDEllTIFICATION OF OCCURREllCE:
Reactor vessel level instrument LIS-1-263-58A exceeded its Limiting Condition f
for O peration.
CONDITIONS PRIOR TO OCCURRENCE Unit 1 in the hot shutd, win condition following a low power level scram.
DESCRIPTl0tl 0F OCCURRENCE:
After unit one scrammed from low level it was decided to check and recalibrate, if necessary, all the reactor pressure vessel level instrumentacion. While doing the instrument department surveillance tests, it was discovered that one of the four low level switches tripped at a setroint which exceeded the Techni-cal Specifications Limiting Condition for Operation. The swi tch LIS-1-263-53A trinnoa at a i m,.> i n r a.3 :., c h e: "S!!: :::t!:r 3.! cf thc Tud...;uu; Lv;. i w iuii, iists tne Limiting Londition f or Uperation as > +8 inches.
were needed to correct the situation.
No operator actions DESIGNATION OF APPARENT CAUSE OF OCCURRENCE':
The switch was inspected and no physical abnormalities could be found. The cause of the occurrence can only be attributed to instrument setpoint drift.
ANALYSIS OF OCCURRENCE:
Though one of the four reactor water level instruments had drifted out of limits there are no safety implications created by the drift. The reactor protection trip systems are arranged in a one out of two-twice logic and can tolerate the failure of one instrument channel. Therefore, since three of the four level switches had setpoints within the limits, the trip system would have functioned as designed.
CORRECTIVE ACTION:
The level switch was immediately recalibrated and functionally tested in accord-ance with instronent surveillance procedures, in January 1973, the setroints of the reactor level switches cere raised to alle.i for i nst rument drift to occar and still stay within the Technical Soccification w roints. The historiie of these instruments were revicwed and it is felt that no further increase of the setpoint is needed at this time. The review of the calibration data for thesc
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}AO,-50-254/74-23 switche's*will continue and any further action r6 quired will be performedtas needed to maintain the safe operation of the reactor.
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4 ALLURE DATA:
sThe. instrument in question is a Yarway Model 4418C. There are eight of these instruments used in both the unit one and unit two reactor protection systems.
Since the setpoints were changed in January 1973, they have been calibrated six times each for a total of forty-eight calibrations. On five occasions, the calibration results have been found out of limits. Two of those cases had vari-ations of less than one-half from the limiting setpoint. Thus, cummu t at ive ex-perience indicates that these switches have not had excessive occurrences of setpoint drift outside of limits.
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