L-78-104, Transmitting Evaluation Report of Abnormal Indications from Metal Impact Monitoring System, Turkey Point Unit No. 4.

Transmitting Evaluation Report of Abnormal Indications from Metal Impact Monitoring System, Turkey Point Unit No. 4.

ML18227D408
Person / Time
Site:	Turkey Point
Issue date:	03/23/1978
From:	Robert E. Uhrig Florida Power & Light Co
To:	Schwencer A Office of Nuclear Reactor Regulation
References
L-78-104
Download: ML18227D408 (10)

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REGUI ATORY INFORMATION DISTRIBUTION SYSTEM <RIDS)

DISTRIBUTION FOR INCOMING MATERIAL 50-25i REC: SCHWENCER A .ORG: UHRIG R E DOCDATE: 03/23/78 NRC FL PWR 8c LIGHT DATE RCVD: 03/27/78 DOCTYPE: LETTER NOTARIZED: NO COPIES RECEIVED

SUBJECT:

LTR 3 ENCL 3 FORWARDING EVALUATION ENTITI ED: "REPT OF ABNORMAL INDIACTIONS FROM METAL IMPACT MONITORING SYSTEMS UNIT NO 4. "i PURSUANT TO ORDER FOR MODIFICATION OF LIC NO DPR-4i DTD 08l02/77.

PLANT NAME: TURKEY PT 83 REVIEWER INITIAL: XJM DISTRIBUTOR INITIAL:

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Office of Nuclear Reactor Regulation Attention: Mr. A. Schwencer, Chief grail Operating Reactors Branch gl CP Division of Operating Reactors ll U. S. Nuclear Regulatory Commission Washington, D. C. 20555 g+4 +p

Dear Mr. Schwencer:

c g< +.~~g Re: Turkey Point. Unit 4 Docket No. 50-251 j

Metal Im act Monitorin S stem 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 forwarding the attached evaluation "Report of Abnormal Indications from Metal Impact Monitoring System, Turkey Point Unit No. 4." The indications were first noticed on March 9, 1978 while reviewing the MIMS tapes recorded during the Unit 4 startup.

Very truly yours, Robert E. Uhrig Vice President REU:RJA:dt Attachment cc: Mr. James P. O'Reilly, Region II Robert Lowenstein, Esquire

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PEOPLE... SERVING PEOPLE

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REPORT OF ABNORMAL XNDICATXONS FROM METAL XMPACT MONITORING SYSTEM Turkey Point Unit 4 Ma'rch 7-8', 1978 XNTRODUCTXON At the Florida Power and Light Company Turkey Point Plant Unit 54, Metal Impact Monitoring alarms were observed on March 7, l978. The Metal Impact Monitoring System incorporates three channels, with the transducers all,mounted on the in-core moveable detector thimble conduits near the bottom of the reactor vessel.

During heatup of the Reactor Coolant System, magnetic tape recordings of the signals of the Metal Impact Monitoring System were made continuously. Nith the reactor coolant flow at steady sta'te conditions, metal impacts were detected during two brief periods, one with two reactor coolant pumps running, and one with three pumps operating. Subsequently, a tape for the impacting period was transmitted 6o the NSSS vendor for analysis.

The tape recordings for two-pump operation, with pumps B and C running, were taken on March 7, l978, with the reactor coolant temperature of 240'F and pressure of 350 psig. The recording with all three pumps operating was taken on March 8, 1978, with reactor coolant conditions of 540'F and 2235 psig.

ANALYSXS During the analysis of this tape, the signals were played through a high pass filter to eliminate 60 Hz noise. The output signals were recorded on light sensitive paper of a recording oscillograph. The tape recorder reproduce speed and the paper speed of the oscillograph were set, so as to obtain a frequency response of 20,KHz and clear indication of waveform shape of the impacts. The oscillograph charts were examined to determine the rate of impacts over a given time interval, and the amplitude of the impacts. Frequency spectra were also generated for selected impacts as a factor in determining the mass of the object. The results of this analysis are summarized in Table'X.

Xn reviewing these data, consideration was given to the rise time of the signal wavegozm of the impacts. Techniques

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C ~ I based on the rise time of the signal waveform og the impacts can be used to determine if the impacts axe agai,nst the vesse1 wall, or agar".nst other surfaces, Xg the rise times of the signal waveforms seen by all transducezs axe rapid, on the order of 100 microseconds, thxs is a fair indication that the impacts are nearby and against the reactor vessel wall. Signals with much 1onger rise times, up to the oxdex of mi11iseconds, are an indication that the object is either impacting another surface or is impacting fax away.

Xn perfoxming this analysis, reference was made to Metal Xmpact Monitoring System data taken during July, 1977 at this plant,.

CONCLUSIONS The results of the analysis of, the data, and a red.ew of the July, 1977 data for two-pump operation indicates that:

1. The waveform of the impact signals were'he same as for July, 1977.

2. The rate of impacts were approximately the same for'l both -peri.ods.

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3. The amplitude of the impacts were moderately higher in March, 1978 than in July, 1977; however, the plant operating, conditions under which the impacts occurred" were not identical. 1

4. The data, from both periods shows no sudden ctime changes, i.e., successive impacts always occurred at the same location. No signal overlaps or impacts within 10 milli-seconds of each other wexe found. Therefore, it can be concluded to a high degree of confidence that there is only one loose object, impacting in the bottom of the reactor vessel.

Based on the relative amounts of the high and low frequency content in the impact signals, the mass of the loose object is estimated to be less than one (1) pound.

The impacts were found to be both against t:he reactor vessel wall and other structures in the bottom of the reactor vessel.

7. The continued safe operation of Turkey Point Unit 4 is not affected by the occurrence of the metal impacts as described in this report.

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TABLE I

SUMMARY

OF RESULTS Maximum Temp. Pumps Amplitude of Rate Observation Background

~DF Runni n<u Si nal G- /5 Period Sec. ~Noise G-240 350 B. C. 1.8-8* 2.4 11.0 1 ~ 25 (3/7/78) Steady (Avg 2 8**)

State 540 2235 A,. B . C . 0.8-4.7* 3.1 9.5 0.67 (3/8/78) Steady (Avg, l.43~*)

State The following data refer to recordings made during July, 1977.

90 400 A. B. 0 7 4p p*** 2.6 12,0 0.7 (2 Minute (Avg. 1.5**)

Runs)

• Maximum aplitude refers to greatest peak amplitude of any channel for the same impact.

• ~Average amplitude refers to average of peak amplitude of all three channels for the same impact.

~*Response limited by Visicorder saturation.

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