ML17320A799
| ML17320A799 | |
| Person / Time | |
|---|---|
| Site: | Cook  |
| Issue date: | 10/10/1983 |
| From: | Will Smith INDIANA MICHIGAN POWER CO. (FORMERLY INDIANA & MICHIG |
| To: | James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| References | |
| NUDOCS 8310210036 | |
| Download: ML17320A799 (10) | |
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INDIANA & MICHIGAN ELECTRIC COMPANY DONALDC. COOK NUCLEAR PLANT P.O. Box 458, Bridgman, Michigan 49106 (616) 465-5901 HQ Z~p~~~
October 10, 1983 Mr. J.G. Keppler, Regional Administrator United States Nuclear Regulatory Commission Region III 799 Roosevelt Road Glen Ellyn, IL 60137
Dear Mr. Keppler:
The purpose of this letter is to inform you of actions taken by Indiana and Michigan Electric Company during the scheduled refueling outage of the Unit 1 reactor at the Donald C.
Cook Nuclear Plant.
This outage commenced on July 15, 1983.
Our initial plans were to perform an Eddy Current Examination utilizing Westinghouse Corporation on two steam generators prior to refuelixg activities and upon completion of the refueling to perform an eddy current inspection of the two remaining steam generators.
Upon disassembly of Reactor Coolant Pump No.
12, it became apparent that the repairs needed on our Reactor Coolant Pumps would extend this outage and a decision was made to perform Eddy Current examinations on all four (4) steam generators prior to refueling.
The performance of Eddy Current Testing in the steam generators was not required during this outage by ASME Code Section XI, 1974 Edition, 1975 Addenda, Re ulator Gus.
e 1.83 or t e Una.t 1
Tec nz.cal S ecx, xcatzons.
However, Plant Management and Sensor Amer>.can Electric Power Corporation Management had planned an eddy current inspection program for the Unit 1 Steam Generators.
The scheduled steam generator (S/G) eddy current testing (ECT) on Cook Unit 1 started July 23 and was completed August 8.
Two thousand seven hundred and forty (2740) tubes in each S/G were inspected.
Indications of imperfections
(<20% through-wall damage),
degradation (20-39% through-wall damage),
and defects
(>40% through-wall damage) were found in the hot legs of all four S/G's.
The indications can be divided into two groups:
1) those occurring in the anti-vibration bar zone near the top of the tube bundle, and
- 2) those occurring on top of the tube sheet.
In addition to these indications, tube denting at the top of the tube sheet, primarily in the sludge pile region, was reported.
Totals for each of the four S/G's and the remedial action taken when necessary are identified in the following data summarization.
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Mr. J.G. Keppler, egional Administrator October 10, 1983 Page 2
(20%
Hot Le Xndications 20-39%
> 40%
Total Dents S/G No.
11 S/G No.
12 S/G No.
13 S/G No.
14 31 43 22 34 Breakdown 4 20%
S/G No.
11 1/30 S/G No.
12 2/41 S/G No.
13 2/20 S/G No.
14 4/30
- Top of Tubesheet 1
2 34 20-39%
0/1 3/5 32/0 3/5
>40%
0/2 0/2 5/0 0/2 8
2 53 32 5
59 8
2 44 Of Hot Le Xndications (AVB/TTS*)
127 153 233 132 S/G No.
11 Row 18, Column 56 Row 2, Column 84 S/G No.
12 Row 14, Colum 83 Row 13, Column 85 Row 14, Column 82*
- Plugged by mistake.
S/G No.
13 Desi nated Tubes Plu ed Xndication 44% H/L Mechanical Plug C/L Mechanical Plug 68% H/L Mechanical Plug C/L Mechanical Plug 80% H/L Mechanical Plug C/L Mechanical Plug 64% H/L Mechanical Plug C/L Mechanical Plug 20% H/L Mechanical Plug C/L Mechanical Plug Row 1, Column 19**
N/A H/L Mechanical Plug C/L Mechanical Plug Row 1, Column 60*
N/A H/L Mechanical Plug C/L Mechanical Plug
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Mr. J.G. Keppler, egional Administrator October 10, 1983 Page 3
S/G No.
13 Con't Row 1, Column 63 1 Row 1, Column 66 2 Row 36, Column 38 Row 36, Column 45 Row 41, Column 55 Row 36, Column 62 Row 36, Column 63 Indication Plug N/A H/L Mechanical Plug Plug 42% H/L Mechanical Plug Plug 51% H/L Mechanical Plug Plug 41% H/L Mechanical Plug Plug 80% H/L Mechanical Plug Plug 54% H/L Mechanical Plug Plug C/L Mechanical C/L Mechanical C/L Mechanical C/L Mechanical C/L Mechanical C/L Mechanical C/L Mechanical Plugged because of unmeasurable indications on inside of tubes 1
Plugged because of partial restriction S/G No.
14 Row 12, Column 17 Row 21, Column 31*
Row 17, Column 33*
Row 18, Column 33*
70% H/L Plug 84% H/I, Plug (See N/A H/L Plug N/A H/L Plug Mechanical Plug C/L Mechanical Welded Plug C/L Mechanical Note 1)
Welded Plug C/L Mechanical Welded Plug C/L Mechanical 116 inches of tube removed from H/L side Note 1
This tube was initially plugged with a mechanical plug and subsequently with a welded plug after tube removal.
The 11 tubes having through-wall defects greater than 40% were plugged.
Additionally, four row 1 tubes in S/G No.
13 were
- plugged, 3 due to unmeasurable indications of cracking on the inside of the tube at the U-bend hot leg tangent point and one because of a partial restriction (probably due to ovaling) at the U-bend cold leg tangent point.
- Also, an additional tube was mistakenly plugged by Westinghouse in S/G No. 12.
A meeting was held with Westinghouse on August, 8 to discuss the results of this eddy current inspection, particularly the unexpected damage found at the top of the tube sheet.
In order to evaluate the severity of this potential problem, we removed three tubes from the hot. leg side of S/G No.
14 on September 9,
1983.
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Mr. J.G. Keppler, egional Administrator October 10, 1983 Page 4
The three tubes were designated as Row 21 Column 31, Row 17 Column 33 and Row 18 Column 33.
The tube designated Row 21 Column 31 was previously plugged because of a 84% tubesheet indication.
The plug on the hot, leg side required removal prior to pulling this tube and the plug in the cold leg side remained in place.
The tube rem'oval required the mechanical plugging of the additional two tubes on the cold leg side of the steam generator.
All three tubes were cut just below the second support plate and then were pulled through the tubesheet opening by means of an integral gripper attached to a hydraulic ram system.
Once the tubes were removed the tube sheet holes were prepared, and a semi-automatic welding tool was installed in the channel head.
The welding tool was remotely controlled from an area away from the steam generator platform.
The weld plugs were installed in the prepared tube sheet holes and welded into place.
The equipment and procedures were qualified by Indiana and Michigan Electric Company Maintenance personnel and the welding was performed by our Maintenance personnel with direction being provided by Westinghouse personnel.
The final step in the process was a visual inspection of the welds by a Westinghouse Quality Assurance Engineer who indicated that the welds were acceptable.
In addition, the steam generator was filled with water to 45 feet above the tubesheet and a leak test was performed around the welded plugs with no evidence of leakage noted.
The tube samples were shipped to the Remote Metallography Facility of the Westinghouse Research and Development Center for nondestructive and destructive examination.
Plant and AEPSC personnel are currently waiting for a report from Westinghouse.
It is anticipated that this report will assist us in characterizing this tube degradation mechanism and help us to formulate a corrective action program for this problem.
Respectfully, W.G.
- mith, r.
Plant Manager
/jas cc:
See Attached Distribution
'I II d
Mr. J.G.'eppler, gional Administrator October 10, 1983 Page 5
cc: B.A. Svensson E.L. Townley R.F. Hering S.H. Steinhart J.R.
Jensen R.F. Kroeger J.F. Stietzel R.L. Otte File
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