05000369/LER-1981-169, Forwards LER 81-169/03L-0.Detailed Event Analysis Encl

Forwards LER 81-169/03L-0.Detailed Event Analysis Encl

ML20033B386
Person / Time
Site:	McGuire
Issue date:	11/20/1981
From:	Parker W DUKE POWER CO.
To:	James O'Reilly NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
Shared Package
ML20033B387	List: 05000369/LER-1981-169, Forwards LER 81-169/03L-0.Detailed Event Analysis Encl 05000369/LER-1981-169-03, /03L-0:on 811021,channel 3 Monitoring Loss of Flow in Reactor Coolant Loop C Appeared to Be Out of Calibr & Declared Inoperable.Caused by Malfunctioning Flow Transmitter.Transmitter Replaced & Root Line Leak Repaired
References
NUDOCS 8112010348
Download: ML20033B386 (3)

LER-1981-169, Forwards LER 81-169/03L-0.Detailed Event Analysis Encl

Event date:
Report date:
3691981169R00 - NRC Website

text

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f,Rg DUKE Powen CObiPANY

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l'OWER DUILDING

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. November 20, 1981 273-4o83 Mr. J. P. O'Reilly, Director U. S. Nuclear Regulatory Commission l./ / p,/*

Region II 101 Marietta Street, Suite 3100 f * ;\\,b Atlanta, Georgia 30303 8

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2 NOV3 0198% '.

Re: McGuire Nucir.ar Station Unit 1 Docket N.

50-369 v.k,cga,T," yf lIl

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Dear Mr. O'Reilly:

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Please find attached Reportable Occurrence Report R0-369/81-169. This report concerns T.S.3.3.1, "As a Minimum, the Reactor Trip System Instrumentation Chan-nels and Interlocks of Table 3.3-1 Shall be Operable..

". This incident was considered to be of no significance with respect to the health and safety of the public.

j Ve,ry truly yours, x

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_ o_

William O. Parker, Jr.

PBN/smh Attachment cc: Director Records Center Office of Management and Program Analysis Institute of Nuclear Power Operations U. S. Nuclear Regulatory Commission 1820 Water Place Washington, D. C.

20555 Atlanta, Georgia 30339 Ms. M. J. Graham Resident Inspector-NRC McGuire Nuclear Station MEAL COPY 8112010348 811120

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McGUIRE NUCLEAR STATION ~

t REPORTABLE OCCURRENCE REPORT NUMBER: 81-169 f

REPORT DATE: November 20, 1981 OCCURRENCE DATE: October 21, 1981 i

FACILITY: 'McGuire Unit 1; Cornelius, N.C.

i i

IDENTIFICATI0N'0F OCCURRENCE: Channel 3 of the Reactor Procective System instrumen-tation monitoring loss of flow in Reactor Coolant loop C was declared -inoperable on October 21, 1981.

CONDITION PRIOR TO OCCURRENCE: Mode 1; conducting low power (< 30%) operations tests.

DESCRIPTION OF OCCURRENCE: The Reactor Coolant Flow and Protective System monitors flow in the four reactor coolant loops by three differential pressure measurements in l'

each loop. The channel 3 loop C flow indication appeared to be out of calibration when it did not agree with"the other loop C flow channels within specified tolerance limits.

Subsequently, the channel was placed in the tripped condition in accordance with the applicable Technical Specification Action Statement.

During the Investigation of the problem a leak was discovered at a loose. fitting on the "hi leg" instrument root line common to the three loop C flow transmitters.

Re-pair of the leak required isolation of all three loop C flow transmitters, which was contrary to the mode 1 conditions of operation of Technical Specification 3.3.1.

It was determined (based on provisions in Technical Specification 3.0.3) that the loop flow transmitters could be isolated for a period up to one hour before initiation of j

reactor shutdown procedures was necessary.

i At 1752 on October 21, the loop C flow transmitters were isolated and repair of the instrument root line was started.- At 1820 the job was completed and the flow instru-mentation was returned to service. All three flow monitors returned to their previous i

inoications with channel 3 remaining out of tolerance.

i APPARENT CAUSE OF OCCURRENCE: When the loose fitting on the instrument root line was discovered, it was thought to be the most probable cause for the variance of the chan-

.nel 3 flow transmitter.

It was later determined that the flow transmitter itself was malfunctioning (attempts to calibrate it could not bring it within limits).

ANALYSIS OF OCCURRENCE: Although the instance of the root line leak was eventually determined not to be the cause of the erroneous flow indication, its occurrence and 4

repair were the more significant aspects of the incident. The occurrence of the faul-ty flow transmitter has not been a recurring problem and is considered an isolated in-stance of component failure.

SAFETY ANALYSIS

The isolation of the loop C flow transmitters left inoperable all three of the redundant flow measuring devices. However, reliable verification of loop flow was continuously available through diverse flow monitoring instrumentation, such' as loop temperature indicators and the reactor coolant pump monitoring instruments.

4 J

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Report Number 81-169 Page 2-Isolation of one loop's flow transmitters functions to trip that loop's low flow co-incidence bistable; thus, a low. flow condition sensed in any one of the remaining three loops will cause a protective trip. The reactor protective system, therefore, was in a more conservative mode of operation during the flow transmitters' isolation.

Thus, considering the conservative condition of the protection system and the avail-ability of flow verifying instrumentation, safe plant operation and the health and safety of the public were unaffected by this incident.

CORRECTIVE ACTION

. After the repair of the leaking instrument root line it was ne-cessary to replace the loop C, channel 3 flow transmitter.

The Veritrak, model 59' DP 4, transmitter was replaced and calibrated in accordance with the procedure, "Re-actor Coolant System Flow Calibration". Proper operation was verified and the chan-

- nel-was declared operable on October 22, 1981.

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