ML18144A706

LER 1976-043-01 for St. Lucie Unit 1, Missing Standpipes in Steam Generator a Feed Ring

ML18144A706
Person / Time
Site:	Saint Lucie
Issue date:	12/21/1976
From:	Schmidt A Florida Power & Light Co
To:	Moseley N NRC/IE, NRC/RGN-II
References
PRN-LI-76-305 LER 1976-043-01
Download: ML18144A706 (3)

Text

P. O. BOX 013100, MIAMI, FL 33101 FLORIDA POWER 8l LIGHT COMPANY December 21, 1976 PRN-LI-76-305 Mr. Norman C. Moseley, Director, Region II Office of Inspection and Enforcement U. S. Nuclear Regulatory Commission 230 Peachtree Street, N.W., Suite 818 Atlanta, Georgia 30303

Dear Mr. Moseley:

REPORTABLE OCCURRENCE 335-76-43 ST. LUCIE UNIT 1 DATE OF OCCURRENCE: AUGUST 13, 1976 STEAM GENERATOR FEED RING UPDATE REPORT NO. 1 The attached Licensee Event Report is being submitted to update our,initial report of August 26, 1976.

Very truly yours, D. chmidt Vice President Power Resources MAS/cmp Attachment cc: Robert Lowenstein, Esquire Director, Office of Inspection and Enforcement (40)

Director, Office of Management Information and Program Control (3)

PEOPLE... SERVING PEOPLE

CONTROL BLOCK: UPDATE Il (PLEASE PAINT AU. AEQUIAED INFORMATION)

LICENSE lICENSEE EVENT NAME UCENSE NUMBER TYPE TYPE 1 F L S L S 1 0 0 0 0 0 0 0 0 0 4[1)1 1 ~o

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89 14 15 25 26 30 31 32 REPORT REPORT Supplementary 1

8 CON'T CATEGORY 57 58 TYP~E

~T 59 SOURCE 60 L 0 61 5 0 COCKET NUMBER 0 3 3 5 68 69 0 8137

-Wc.'4Z CATE 6

74 1 2 75 REPORT CATE 2 1 7 6 80 EVENT OESCRIPTION During a special inspection of Steam Generators "A" and "B" in order to 8 9 60 accomplish tack welding of the standpipes for the feed ring, three 8 9 80 standpipes were found missing in the "A" S/G. The missing standpipes 8 9 80 retrieved and one further stand i e was removed for ins ection

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were and 89 80 anal sis. No other discre ancies were found in the "A" S G. No

89. PRhIE 80 SYSTBA CAUSE COMPCNSfT CCMPChB4T COOE COOE COMPONENT COOS SUPFUER M ANUS@..a.'RCi VQLATION

~ca ~o H TE XCH N C 4 9IO 8 9 10 11 12 17 43 CAUSE OESCRIPTION As previously reported, the cause was cyclic fatigue and failure. The Be 80 failed standpipes from the "A" S/G were inspected at the vendor '

8 9 manufacturin facilit . The investi ation disclosed the followin 89 FACAJZY METHOO CF 80 STATUS POW R OTHER STATUS OISCOVERY OISCCVERY OESCRIPTION

~z ~oo o N/A N/A 8 9 10 12. 13 44 45 4S FORM OF AMOUNT OF ACTIVITY LOCAT:ON OF RElEASE N/A 8 9 10 11 44 45 PERSON¹L EXPOSURES N A 8 9 11 12 13 80 PEAS'ON¹L INJURIES NUMBER OESCRIPTION ae Loaoof 11 12 80 03~LE CONSEGUENCES N/A 9 80 LOSS GR OAMAGE TO FACIUTY TYPE OESCRIPTION

+Z None Plant was shut down

a. xca won was comp et d for fuel insaoc 9 10 mo before the =uel inspection was. 80 PUBUCITY N/A AOGITIONAL FACTORS See Page two for continuation of Event Description and Cause Description.

M. A. Schoppman 80 NAME:

305/552-377 9 FHONE:

Reportable Occurrence 335-76-43 Licensee Event Report Update gl Pa e Two EVENT DESCRXPTION (Continued) discrepancies were found in the "B" S/G.

CAUSE DESCRXPTION (Continued)

The failed standpipes were in regions immediately adjacent to the feed ring header where the flow rate and turbulence in the feedwater ring is the greatest.

All three failed standpipes had evidence of flow induced vibrations as indicated by rubbing contact between the O.D. of the standpipe and the X.D. of the nipple at the junction with the feedwater ring.

One standpipe had become unthreaded due to vibra-tion. The other two failures resulted from fracture of the nipple. In each case the fractured area contained fatigue cracks which initiated the failure.

Corrective action has been taken as follows: The 74 standp'pcs were removed from each S/G thus eliminating the vibration mechan-ism. The 74 holes in the bottom of each feed ring were welded closed. Holes were cut in the top of each feed ring and 36 four inch, 90'traight elbows were installed in each S/G, with the open end facing th'e interior of the S/G. This mee-'s the original design intent of preventing the feed rings fro=~

draining while still allowing feed water flow. This action was

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processed in. accordance with the requirements of 10 CFR 50.59.