ML18227D451

09/30/1977 Letter Report of Abnormal Indications from Metal Impact Monitoring System

ML18227D451
Person / Time
Site:	Turkey Point
Issue date:	09/30/1977
From:	Robert E. Uhrig Florida Power & Light Co
To:	Lear G Office of Nuclear Reactor Regulation
References
Download: ML18227D451 (8)

Text

DISTRIBUTION AFTER ISSUANCE OF OPERATING LICENSE US NUCI.EAR REGULATORY COMM ON DOCKET NUMBER NRC FORM 195 I2-7BI FILE NUMBER NRC DISTRIBUTION FoR PART 50 DOCKET MATERIAL TO: FROM: DATE OF DOCUMENT G Lear Florida Power G Light Co 9.-3 0-77.

Miami, Fla DATE RECEIVED R E Uhrig 10-4-77

@LETTER ONOTORIZEO PROP INPUT FORM NUMBER OF COPIES RECEIVED

/ORIGINAL @UNCLASSIFIED SCOPY DESCRIPTION ENCI.OSURE lp Report of abnormal indications from metal impact monitoring system....Sept 16-18, 1977 PLANT NAME: Turkey Point g4 10-4-77, ehf SAFETY FOR ACTION/INFORMATION BRANCH CHIEF: 7 INTERNAL D IST RIBUTION NRC PDR I GE (2)

OELD HANAUER CHECK STELLO EISENHUT SHAO BAER BUTLER GRIMES J. COLLI S EXTERNAL DISTRIBUTION ONTROL NUMBER LPDR:

TIC NSIC 16 CYS ACRS SENT CATE

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P. OX 013100, MIAMI, FL'33101 i4!/r 0

F LORI DA POWER & LIGHT COMPAN Y September 30, 1977 L-77-307 Office of Nuclear Reactor Regulation Gl Attention: Mr. George Lear, Chief Operating Reactors Branch 53 ~

Division of Operating Reacto @) OCPq )g~~

U. S. Nuclear Regulatory Commission >~i Pe+~ R1g CO~ ISS +~IQyg Washington, D. C. 20555 , ~(sm1~"

Re: Turkey Point. Unit 4 Cg Docket No. 50-251 Metal Impact Monitoring S stem ll 0~

Dear Mr. Lear:

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 S Light Company is forwarding the attached evaluation "Report of Abnormal Indications from Metal Impact Monitoring System, Turkey Point. Unit No. 4, September 16-18, 1977". The conclusions stated in the report are that the abnormal indications were false alarms and thus are not a safety consideration.

Very truly yours, Robert E. Uhrig Vice President.

REU:WAK:dt Attachment cc: Mr. James P. O'Reilly, Region II Robert Lowenstein, Esquire 17 PEOPLE... SERVING PEOPLE

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REPORT OF ABNOKML INDICATIONS

, FROM METAL XMPACT MONITORING SYSTEM TURKEY POINT UNIT NO. 4 SEPTEMBER 16-18, 1977 The Metal Xmpact Monitoring System (MIMS) generated numerous alarms between 7:30 P.M. Friday, September 16 and 3:30 A.M. Sunday, September 18. See Attachment 1 for details.

During the periods of MXMS alarms, the control room opera-tors listened to the MXMS loudspeaker in the control room and heard no unusual noises. The normal flow and back-ground noises were the only sounds present. Therefore, no action was taken since the alarms appeared to be false.

On Tuesday, September 20, a stage by stage check of the MIMS electronics was begun. Refer to Attachment 2, a block diagram of the MIM System. Stage 6, the tuneable filter, was found to be oscillating. WithTheno integrated was producing 300 millivolts of output.

input, it circuit amplifier (type 741) for this stage was replaced.

This stopped, the oscillations.

On Wednesday, September 21, the check of the MIMS was completed. No further problems were found. Live signals from the transducers were monitored and the alarm setpoints were checked. The false alarms which occurred over the weekend are attributed to oscillations generated in stage 6.

These were interpreted as metal impacts by the following stages, and alarms were generated.

As a result of this occurrence, the following actions are being undertaken:

a ~ The MIMS channel which is'being monitored for alarms will be the same channel selected for the control room speaker (by procedure).

b. All three MIMS channels will be operated at, 10 G full scale sensitivity (by procedur'e).

c ~ A procedure which the control room operators can use for verifying the validity of MIMS alarms is being written.

d. The weekly check of the MIMS transducer output will be expanded to include a check for operability of the MIMS electronics.

e. A procedure for normal operation of the MIMS is being written which will include Items a, b, and d.

ATTACHMENT 1 0

I HIif System created numerous alarms over the period 7:30 P H., Friday, September 16, until 3:30 P.M., Sunday, September 18.

Time Descri tion 7 :30 P.M.,'Friday Random'ingle events, about two per hour Amplitude about 4 to 7 volts.

3:00 A.H.,Saturday (2 -.

3 times size of impacts detected on initial pump runs.)

'5'.GG A.M., Saturday Random events, about 25 per hour. -,Mostly single events 7:00 A.bt"., Saturday but'some indicated full scale (10 per second). Amplitude AND 8 to 10 volts. (Full scale is 10 volts.)

S:20 A.N+, Saturday

. 10:00 A.M., Saturday Noon, Saturday About 7 events in 12 minutes. Amplitude about 8 single eve'nts. volta'ostly 6:30 P.f3., 'Saturday Numerous events, from 63; volts to offscale. Rate from 9:30 P.g., Satu,"day 'single to offscale. Stopped abruptly at 9:25 P.H J

r 3:15 to 3:30 A.N., -5 more events, mostly large and high rate Nearly Sunday offscale.

After 3:30 A.M., Sunday, no further indications of events.

Operator" rqgoi that speaker in coniro1 room sounded as always - flow noise plus background.

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