05000244/LER-1980-003-01, /01T-0:on 800414,during Steam Generator Inservice Insp,One Tube in a Steam Generator & 34 Tubes in B Generator Showed Pluggable Indications.Probably Caused by Concentration of Caustics in Crevices
| ML17261A185 | |
| Person / Time | |
|---|---|
| Site: | Ginna  |
| Issue date: | 04/28/1980 |
| From: | Curtis A ROCHESTER GAS & ELECTRIC CORP. |
| To: | NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I) |
| Shared Package | |
| ML17249A866 | List: |
| References | |
| LER-80-003-01T, LER-80-3-1T, NUDOCS 8005020230 | |
| Download: ML17261A185 (4) | |
| Event date: | |
|---|---|
| Report date: | |
| 2441980003R01 - NRC Website | |
text
U. S. NUCLEAR REGULATORY COMMISSION NT REPORT (CAR 1282)05020 g5Ct
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8 60 61 DOCKET NUMBER 68 69 EVENT DATE EVENT DESCRIPTION AND PROBABLE CONSEQUENCES Qlo During normal steam generator (SG) tube inservice inspection, 1 tube in "A" SG and 34 tubes in "B" SG showed pluggable indications.
(T.S. 6.9.2.a(3)).
Eddy current test-ing showed 1 "A" SG tube and 3 "B" SG tube indications above tube sheet, and 31 "B"
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2 "B" outlet tubes with crevice indications and 1 "B" outlet tube without indication were pulled for analysis.
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Other 4 most likely having small defects over past several years and have recently exceeded plugging criteria.
After above tube pulling, tubes were either welded or mechanicall 3
plugged.
Crevice boil out procedure developed to be used in this outage.
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Westinghouse series 44 with Inconel tubes size 0.875 in. OD
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PHQNE.716 546-2700 ext. 2542 a
DISCOVERY DESCRIPTION Q32 Eddy current test of tubes for ISI LOCATION OF RELEASE Q NA
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Attachment tc LER 80-II13/01T-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, one (1) tube in the "A" steam generator and thirty-four (34) tubes in "B" steam generator showed degradation requiring plugging.
No other tubes displayed abnormal degradation upon evaluation of all the multifrequency eddy current data.
The one degraded tube in the "A" steam generator and three tubes in the "B" steam generator showed indications exceeding the plugging criteria.
The indications in these four tubes on the periphery of the steam generators were above the top of the tube sheet.
The indications in the other thirty-one tubes in the "B" steam generator were all in the tube sheet crevice.
The four periphery tubes which had indications are most probably defects which have been in the steam generator for several years and have now developed into pluggable indications.
These indications were small volume signals without a great amount of depth; each one was under 50%
through wall.
The thirty-one tubes with crevice indications were located in the same general area where thirteen other crevice indications had been found in previous inspections, March and December 1979.
Thirteen of the indi-cations found in this inspection were identified by all the eddy current frequencies.
Eighteen other indications were only identified by the 100 KHz absolute frequency.
The postulated cause of these crevice indications is caustic intergranular attack (IGA) of the tubing material resulting in ultimate cracking.
Two of these tubes with indications from the "B" steam generator inlet were removed by pulling, along with one without any indication in the outlet for metallurgical and chemical analysis.
The concentration of caustics in the tube sheet crevices is postulated to be the result of the changing molar ratio of previously concentrated Na and PO4 during the original phosphate chemistry used prior to November 1974.
Since that time all volatile treatment water chemistry has been main-tained with subsequent addition of full flow deep bed condensate deminer-alizers in January 1978.
In order to provide corrective action in the crevice region of the tube sheet a crevice flushing and boil out procedure has been developed for implementation during this outage.
In general, the multifrequency eddy current examination results of Ginna Station's steam generators show that the AVT chemistry with fullflow condensate polishing is proving extremely effective in minimizing corrosion effects above the tube sheet in the genera-tors.
Therefore, the plant willcontinue to operate with full flow condensate polishing to minimize the ingress of unwanted chemical species.
An eddy current examination and evaluation willbe performed in accordance with the ISI program at the next annual refueling outage.