ML17261A109

LER 79-006/01T-0 on 790321:degradation in 6 Tubes of Steam Generator B.Caused by Localized Residual Caustics Erosion at Support Plates & Stress Corrosion Mechanism Re Deformation at Tube Sheet & Operationsl Stresses

ML17261A109
Person / Time
Site:	Ginna
Issue date:	04/03/1979
From:	Curtis A ROCHESTER GAS & ELECTRIC CORP.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I)
Shared Package
ML17244A443	List: ML17244A442 ML17261A109
References
TASK-TF, TASK-TMR LER-79-006-01T, LER-79-6-1T, NUDOCS 7904090160
Download: ML17261A109 (4)

Text

NRC FORM 366 U. S. NUCLEAR REGULATORY COMMISSION t7-77) 79-006/01T-0 LICENSEE EVENT REPORT (CAR 1215)

CONTROL BLOCK: Q1 (PLEASE PRINT OR TYPE ALL REQUIRED INFORMATIONI

~o 7 8 9 N Y R E LICENSEE CODE G

I

'2'5 14 0 0 6

0 0 0 LICENSE NUMBER 0 0 0 0 Q' 25 26

'LICENSE TYPE

' 30 QE~QE 57 CAT 58 CON'T msl ~LQB 0 5 0 0 0 2 4 4 O0 0 3 2 1 7 9 s 0 4 0 3 7 9 80 QB 7 8 60 61 OOCKEThIUMBER 68 69 EVENT DATE 74 75 REPORT DATE EVENT DESCRIPTION AND PROBABLE CONSEQUENCES Qlo During normal steam generator (SG) tube inservice ins ection, 6 tubes in "B" SG

~93 showed degradattonre uirin lu in . T.S. 6.9.2.a 3 . Edd current testin

~93 indicated tubes R17C39 and R18C42 with wall loss below to of tube sheet, R28C12 and R35C75 with wall loss in center of support plates 1 and 2 respectively, and R43C55 and R43C56 showed indications similar to those reported in LER's 77-08 and 78-003.

~08 7 8 9 80 SYSTEM, CAUSE CAUSE COMP. VALVE CODE CODE SUBCODE COMPONENT CODE SUBCOOE SUBCODE

~OB ~CS Qll E Q12 ~SQ13 H T E X C H Qls ~PQ>> ~ZQls 7 8 9 10 11 12 13 18 19 20 SEQUENTIAL OCCURRENCE REPORT REVISION Qll LER(RO REPQRT ACTION FUTURE EVENT YEAR

~79 21 22 EFFECT

+

23 SHUTDOWN

~00 24 REPORT NO.

6 26

+~

27

~01 28 ATTACHMENT CODE 29 NPRDP TYPE

~T 30 PRIME POMP.

31 32 NO.

COMPONENT TAKEAI ACTIOhl ON PLANT METHOD HOURS +22 SUBh'IITTED FORh'I SUB. SUPPLIER MANUFACTURER Q18~ZQls ~ZQ20 ~ZQ22 0 0 0 0 Y Q23 ~NQ24 ~NQ28 1 2 0 Qs 33 34 35 36 37 40 41 42 43 44 47 CAUSE DESCRIPTION AND CORRECTIVE ACTIONS Q27 9 Possible localized residual caustics, erosion at support plates early in SG operation, and stress corrosion mechanism associated with deformation at tube sheet and opera-tional stresses. The 6 tubes were explosively plugged. SG is Westinghouse series 3 44 with Inconel tubes size 0.875 in. OD, 0.50 in. walls.

~14 m W~Q ~0I 7 8 9 80 FACILITY STATUS  % POWER OTHERSTATUS NA

~ METHOD OF DISCOVERY

~BQ31 Eddy current DISCOVERY DESCRIPTION Q32 test of tubes for ISI 7 8 9 10 12 13 44 45 46 80 ACTIVITY CONTENT 8

RELEASED OF RELEASE

~ZQ33 ~ZQ34 AMOUNTOF ACTIVITY NA Q NA I.OCATION OF RELEASE Q 7 8 9 10 44 45 80 PERSONNEL EXPOSURES NUMBER TYPE DESCRIPTION Q39 mll ~00 8 0 QEP~ZQ38 NA 7 9 11 12 13 80 PERSONNEL INJURIES 7 8 9 11 12 80 LOSS OF OR DAhIAGE TO FACILITY TYPE DESCRIPTION Q43 9 ~ZQ42 NA 7 8 9 10 PUBLICITY 7 904090 1c-~ NRC USE ONLY 80 7 8 9 10 68 69 80 o NAME DF PREPARER A. E. Curtis, III PHDNE 716/546-2700, ext 2263 ~ L

e Attachment to LER 79-006/01T-0 Rochester Gas and Electric Corporation R. E. Ginna Nuclear Power Plant, Unit No. 1 Docket No. 50-244 During the normal steam generator tube inservice inspection program, six tubes in the "B" steam generator were found to have degradation requiring plugging. These six tubes were explosively plugged. No other tubes dis-played abnormal degradation upon evaluation of all the multifrequency eddy current data. The "A" steam generator inspection results confirm that there has been no abnormal degradation of its tubes over the last operating period.

The "B" steam generator has also seen minimal changes over the last operating

'period.

Two tubes, R17C39 and R18C42, displayed external wall loss indica-tions four inches below the top of the tube sheet, of 58% and 75% respectively, believed due to localized residual caustics.

Two tubes, R28C12 and R35C75, displayed wall loss of 40 to 50% in the center of support plate 1 and 2 respectively. These same indications appear in previous inspection data but were not called out by data interpreters.

This erosion is postulated to be a result of erosion occurring in early operation of the steam generator by water flashing to steam in the geometric center of the support and eroding the tube wall. This mechanism could have occurred when the tube to tube support crevices were not packed with magnetite early in plant operation. Other tube to tube support intersections in low flow areas show similar indications but at much less tube wall loss, less than 20%.

Tubes R43C55 and R43C56 displayed distorted tube sheet signals, with OD tube wall loss associated with the distorted signal + 40% and 68%

respectively. These tubes are in the same area where previous leaks have occurred, as described in LER's 77-08 and 78-003.

In general, the multifrequency eddy current examination results of Ginna Station's steam generators show that the AVT chemistry with full flow condensate polishers is proving extremely effective in minimizing corrosion effects in the steam generators. Also, the good operating history of the steam generators for the last several years supports the benefits of AVT chemistry. Therefore, the plant will continue to operate with full flow con-densate polishing to minimize the ingress of unwanted chemical species.

An eddy current examination and evaluation will be performed in accordance with the ISI program at the next annual refueling outage.

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