ML20085F599

AO AO-19-74:on 740906,steam Generator Liquid Blowdown Monitor R1A-0707 Failed to Trip Isolation Valves on High Radiation.Caused by Alarm Electronic Tracking Unit Not Being in Sequence W/Meter Face Alarm Setpoint

ML20085F599
Person / Time
Site:	Palisades
Issue date:	09/16/1974
From:	Sewell R CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.)
To:	US ATOMIC ENERGY COMMISSION (AEC)
Shared Package
ML20085F600	List: ML20085F599 ML20085F602
References
AO-19-74, NUDOCS 8308230046
Download: ML20085F599 (2)

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/'  % CORSum8lS H, J POW 8r h'Cro- 2 Company

(?d (f(, T)\T O 2d tl' c,eneral OHeces 212 West M*chigan Avenue. Jacuon, M chegan 49201 e Area Code St7 788-0550 September 16, 1974

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Directorate of Licensing 5 Re: Docket No 50-255 U3 Atomic Energy Commission ,1 1/ License No DPR-20 Washington, DC 205h5 .,

/ Palisades Plant

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Gentlemen:

Attached is Abnormal Occurrence Report A0-19-74 covering the steam generator liquid blowdown monitor failure to trip on high radia-tion. This failure did not involve a release to the environment above allowable limits. The high radiation experienced was due to the residual radioactivity in the steam generator from the August 1973 tube leakage and not a recurrence of tube leakage.

Yours very truly, Ralph B. 'Seve11 (Signed)

DAB / map Ralph B. Sewell Nuclear Licensing Administrator CC: JGKeppler, USAEC i

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. ABNORMAL OCCURRENCE REPO Palisades Plant r* Docket No 50-255

1. Report Number: A0-19-74 2a. Report Date: September 16, 1974 2b. Occurrence Date: September 6, 1974 3 Facility: Palisades Plant

h. Identification of Occurrence: Failure of steam generator liquid ,

blowdown monitor (RIA-0707) to trip isolation valves on high l radiation. i 5 Conditions Prior to Occurrence: Hot shutdown.

6. Description of Occurrence: Plant personnel found the steam generator blowdown monitor reading slightly above the alarm set point. This alarm set point should have closed the steam generator blowdown valves and the blowdown tank discharge valve.

7 Designation of Apparent Cause: The apparent cause was traced to the alarm electronic tracking unit which was not in sequence with the meter face alarm set point. In addition, the quarterly trip function test procedure (RMC7(A)] appeared to be inadequate in determining this type of variation.

8. Analysis of Occurrence: Investigation of the monitor disclosed that the tracking unit was found to alarm at 9,000 cpm, while the meter face indicated that the alarm was set at h,000 cpm.

The current procedure (RMC-7( A)] teste'd the operability of all of the trip functions once the alarm was actuated but did not address itself to checking to determine if the Radiation Instrument Annunciator alarmed at the proper meter setting.

During a failure of this type, activity in the discharge liquid could have caused the concentration in the discharge to exceed Technical Specifications requirements. However, the activity in the blowdown liquid was measured and found to be of the same type (spectrum) as previously observed and of a level well below the permissible dis-charge limits. The high radiation experienced was due to the residual radioactivity in the steam generator from the August 1973 tube leakage and not a recurrence of tube leakage.

9 Corrective Action:

(1) Steam Generator Blowdown }bnitor (RlA-0707) was removed from service, repaired and reinstalled.

(2) The process monitor quarterly test procedure [RMC-7(A)] is being revised to ensure proper detection of out-of-sequence settings of the trip function.

10. Failure Data: There are no records of any previous failures of this type.

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