ML20085J865

Ao:On 740604,during Functional Test on Main Steam Line Radiation Monitor D,Trip & Alarm Did Not Function.Cause Unknown.Monitor Replaced

ML20085J865
Person / Time
Site:	Dresden
Issue date:	06/12/1974
From:	Stephenson B COMMONWEALTH EDISON CO.
To:	Oleary J US ATOMIC ENERGY COMMISSION (AEC)
Shared Package
ML20083L264	List: ML20083L261 ML20085J865
References
420-74, NUDOCS 8310190149
Download: ML20085J865 (2)

Text

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(V l wy Address Reply to: Post Othee Box 767 '

N Chicago, Ilhnois 60690 BBS Ltr.d420-74 Dresden Nuclear Power Station R. R. #1 Morris, Illinois 6045 tn, June 12, 1974 4 D o

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Mr. J. F. O' Leary, Director $% h R

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Directorate of Licensing y U. S. Atomic Energy Con:missicn

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SUBJECT:

LICENSE DPR-25. DRESDEN NUCLEAR POWER STATION UNIT #3. REPO

_OF ABNOR!'AL OCCURRENCE PER SECTION 6.6.B.1.a OF THE TECIINICAL SPECIFICATIONS.

MAIN STEAM LINE RADIATION MONITOR TEST FAILURE.

References:

1) Notification of Region III of AEC Regulatory Operations Telephone: Mr. F. Maura,1330 hours0.0154 days <br />0.369 hours <br />0.0022 weeks <br />5.06065e-4 months <br /> on June 4,1974 Telegram: Mr. J. Keppler,1425 hours0.0165 days <br />0.396 hours <br />0.00236 weeks <br />5.422125e-4 months <br /> on June 4,1974

2) Dwas: P & ID M-12 S&L 12E2464 Lear br. u'i.cary:

This letter is to report a condition relating to the operation of the unit at about 0030 hours3.472222e-4 days <br />0.00833 hours <br />4.960317e-5 weeks <br />1.1415e-5 months <br /> on June 4,1974. At this time, during routine testing of the "D" main steam line (MSL) radiation monitor, an upscale trip failure was reported. This malfunction is contrary to Table 3.2.1 of the Technical Specifications which requires that two radiation nonitors per trip channel be operable.

PROBLEM At the time of the occurrence, Unit 3 was in the startup mode at 0 MWt power. Routine weekly surveillance nas in progress on the main steam line radiation monitor. During the functional test on monitor "D",

the trip and alarm did not function. Approxic:stely 20 minutes later, a spurious alarm and trip was received from the "D" monitor.

The Instrument department was immediately notified, and invest-igation into the problem began at approximately 0800 hours0.00926 days <br />0.222 hours <br />0.00132 weeks <br />3.044e-4 months <br /> on June 4,1974.

The normal function of the radiation monitors is to initiate a reactor scram and isolation if background radiation exceeds 3007. normal level.

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Mr. J. F. O'L2 cry p(_/ Junn 12, 1974 INVESTICATION The Instrument department ran several tests on the "D" radiation monitor at approximately 0900 hours0.0104 days <br />0.25 hours <br />0.00149 weeks <br />3.4245e-4 months <br /> on June 4,1974. No abnormalities were noted. The monitor was again successfully tested several times throughout the day. The monitor was then replaced with a sr're so that further bench checks could be made.

_ CORRECTIVE ACTION The corrective action, completed on June 4, 1974, was to replace tho "D" main steam line radiation monitor with a spare unit. The monitor will be bench checked to determine the cause of the trip failure.

EVALUATION The main steam line radiation monitoring system consists of four monitors connected in a one-out-of-two-twice logic configuration. The remaining three monitors functioned properly during the surveillance. It is therefore concluded that the safety of the general public or the plant personnel was not jeopardized as a result of this occurrence.

The cumulative experience to date indicates that the radiation conitors seldoa walfunction, and the few problem. thet have occurred were unrelated to this occurrence.

Sincerely, B. B. Stephenson Superintendent BBS:WEH:do 1

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