ML20085F823
| ML20085F823 | |
| Person / Time | |
|---|---|
| Site: | Palisades  |
| Issue date: | 06/14/1974 |
| From: | Sewell R CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.) |
| To: | Oleary J US ATOMIC ENERGY COMMISSION (AEC) |
| Shared Package | |
| ML20085F780 | List: |
| References | |
| AO-10-74, NUDOCS 8308230494 | |
| Download: ML20085F823 (3) | |
Text
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Campany General Offices. 212 West Michigan Avenue. Jackson. Michigan 49201
- Area Code S17 788-0550 June 14, 1974 i
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C Mr. John F. O' Leary, Director
[C Docket 50-255 k$
i Directorate of Licensing h,, J 7[O[(;,
License DPR-20
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US Atomic Energy Cornission lj Palisades Plant Washington, DC 205L5 c.;,hi,fjpg
'S A0-10-74
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Dear Mr. O' Leary:
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N The attached report describe n
rrence that took place on May 5,197h but was not classified as an " abnormal occurrence" until June b.
It covers the recent primary-to-secondary tube leakage in "A" steam 6enerator. This report is only preliminary as investigations into the cause are under way. A schedule of submittals of additional infor-mation will be provided during the week of June 17,197h.
Yourc ':cr; tr'fi,
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f RBS/ map Ralph B. Sewell Nuclear Licensing Administrator CC: JGKeppler, USAEC
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ABNORMAL OCCURRENCE REPORT Palisades Plant 1.
Peport No: A0-10-7h, Docket 50-255 2a.
Report Date: June 14, 197h 2b.
Occurrence Date: May 5,197h-(Classified as an Abnormal Occurrence June h,1974) 3.
Facility: Palisades Plant 4.
Identification of Occurrence:
"A" Steam Generator Tube Leakage 5
Conditions Prior to Occurrence: Plant in the cold shutdown condition.
Preparations were being made to run the primary coolant pumps to sweep air from the primary coolant system.
6.
Description of Occurrence: As primary system pressure was being raised to allow primary coolant pump operation, a primary-to-secondary leak developed in the "A" steam generator.
Based on the change in water level on the secondary side of the steam generator, the leakage rate was estimated at 10 to h2 gallons per minute. The primary pressure et the Lime the leak occurrea was approximately 200 psig. Further investigation revealed a tube in Quadrant III, Line 3, Row 110, to have a 100% through wall defect. This defect was located in the vertical tangent to the hot leg bend. Approximately 18 near-neighbor tubes were eddy-current tested and it was determined that therc was no change in their. condition as compared to the results of the fall 1973 eddy-current testing that was conducted at the plant.
The de-fective tube was plugged and the secondary side of the steam generator was refilled.
An additional tube was found to have a slight secondary to primary leak. This tube was in Quadrant II, Line 3, Row 109 This tube van also plugged. Again, the leak was located by eddy-current testing in the vertical tangent to the hot leg bend. Additional eddy-current testing was performed on approximately 200 tubes in the immediate vicinity of the two tubes found to be leaking. The results of this testing revealed indications of defects in the one tube at the vertical tangent to the hot leg bend and eight other tubes be-tween Support Elevations 10 and 12.
A' comparison of the eddy-current test data obtained in May to that obtained in the fall of 1973 re-vealed that defects that were detected in the fall of 1973 have not changed.
7 Designation of Cause:
Unknown 8.
Analysis of Occurrence: Baced on the comparative analysis of the eddy-current test results, we have concluded that the degradation of the steam generator tubing described in Iten 6 above has occurred I
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.l' ABNORMAL OCCURRENCE REPORT Palisades Plant (Contd) since the fall of 1973 eddy-current testing and, therefore, during a period of time when the unit has been in the cold shutdown con-dition. With the steam generators either in dry or vet lay-up condition, the mechanism of the degradation is unknown at this time although it is thought to be different from the previous degradation experienced in the Palisades steam generators.
9 Corrective Action: A detailed investigation is under way to determine the cause of the additional degradation discovered in May 1974. This investigation includes eddy-current testing of the hot leg tubes in both steam generators that were tested in the fall of 1973 and at least 100 cold leg tubes in each steam generator and metallographic examination of 6 removed tube samples (2 broken at defect location during removal).
In addition, an investigation is being performed to identify possible corrosion mechanism under the conditions ex-perienced. The results of these investigations are not yet available.
10.
Failure Data:
Primary-to-secondary leakage was experienced at the Palisades Plant in January 1973 and August 1973 These failures are attributed to tube wastage during plant operation due to a phosphate corrosion meennnism.
Tha aacredatien repcrted in this rcpart occurred during plant shutdown. While the mechanism of the degradation is unknown, it is not presently considered to be similar to the vastage mechanism experienced during the first two occasions of primary-to-secondary tube leakage.
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