ML20084B704

Ro:On 780813,metal Impact Monitoring Sys Alarmed Six Times in 1 H.Caused by Acoustic Emissions Produced by Reactor Vessel During Periods of Changing Pressure & Temp.Tubesheet Photographs of Steam Generators Verified

ML20084B704
Person / Time
Site:	Turkey Point
Issue date:	08/25/1978
From:	Robert E. Uhrig FLORIDA POWER & LIGHT CO.
To:	Schwencer A Office of Nuclear Reactor Regulation
Shared Package
ML20084B707	List: L-77-228, Forwards Rept on Sys Disturbance 770516 ML20084B704 ML20084B732 ML20084B752
References
NUDOCS 8304070034
Download: ML20084B704 (2)

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( VIAMI. FL 33101 O" O. BOX 013100, lE FLORIDA POWER & LIGHT COMPANY August 25, 1978 L-78-278 Office of Nuclear Reactor Regulation Attention: Mr. A. Schwencer, Chief Operating Reactors Branch #1 Division of Operating Reactors U. S. Nuclear Regulatory Commission Washington, D. C. 20555

Dear Mr. Schwencer:

Re: Turkey Point Unit 4 Docket No. 50-251 Metal Impact Monitoring Sys tem The Order for Modification of License for Turkey Point Unit No. 4, dated August 2, 1977, amended paragraph 3.D of License DPR-41. Pursuant to the requirements of this Order, Florida Power & Light Company is for-warding the attached evaluation " Report of Abnormal Indica tions from Metal Impact Monitoring System, Turkey Point Unit No. 4." The indications occurred on August 13, 1978 during the unit cooldown for refueling.

Very ly yours,

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Robert E. Uhrig Vice President REU/RJA/ mal Attachment cc: Mr. James P. O'Reilly, Region II Robert Lowenstein, Esquire t

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v REPORT OF ABNORfMh INDICATIONS FROM METAL IMPACT MONITORING SYSTEM (MIMS)

TURKEY POINT UNIT 4 August 13, 1978 On August 13, 1978, while Turkey Point Uni.t 4 was cooli ng down for a scheduled refueling outage, t.he MIMS alarmed 6 times during a one hour period. The 6 events were all separate, single, low energy indicationa. No other alarms were experienced during the remainder of the cooldewn.

Our review of the MIris data concluded that the most prob-able cause of the alarms was normal acoustic emissions produced by the reactor vessel during periods of changing pressure and temperature.

Upon shutdown, tubesheet photographs of all 3 steam gen-erators verified that no tube plugs had become loose.

This information supported the conclusion that the indi-cations were not caused by loose parts. Iloweve r , if the assumption is made that the alarms were caused by a loose part (s) , the separate, low energy impacts indicate a single object. This is consistent with prior MIMS indi-cations on this unit. This information, along with the continuing commitment of performing core barrel motion me;isurements after unit heat up, and for continued loose parts moni toring, ensures continued safe operation of Turkey Point Unit 4.

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