ML20086D023
| ML20086D023 | |
| Person / Time | |
|---|---|
| Site: | Diablo Canyon  |
| Issue date: | 01/15/1975 |
| From: | Crane P PACIFIC GAS & ELECTRIC CO. |
| To: | Knuth D US ATOMIC ENERGY COMMISSION (AEC) |
| Shared Package | |
| ML20086D026 | List: |
| References | |
| NUDOCS 8311300037 | |
| Download: ML20086D023 (3) | |
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Dr. Donald F. Knuth, Director
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Directorate of Regulatory Operations E"ifEE,;;,,,,,.
Office of Regulation
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U. S. Atomic Energy Commission Washington, D. C. 20545 Re:
Dockets 50-275
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Dear Dr. Knuth:
Invcatigation of the deficiencies.in the Unit 1 steem gn-erator primary nozzle safe ends, reported to your office March 29, 1974, has been completed.
Interconnected circumferential surface in-dications in the first stainless steel weld pass were found in 'six of the eight Unit 1 steam generator nozzle safe ends.
No similar indica-tions were found in the nozzles of the reactor vessel or pressurizer of either unit, or of the Unit 2 steam generators, although these all were examined visually and by dye penetrant.
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Steps to correct this condition were developed through con-sultation between PGandE and Westinghouse engineers and. metallurgists.
i These measures were included in Deviation Report Number 214.
The dye penetrant indications were removed by shallow grinding.
The maximum depth of grinding was ninety-seven thousandths of an inch '(0.097").
Ground areas were blended to eliminate stress risers. ' Maps showing the extent and depth of the grinding were prepared and were submitted:
to Westinghouse for review.
Westinghouse's study of the ground areas determined that the wall thickness of each nozzle still met design re-quirements.
The. repair work has been completed and Deviation Report.
Number 214 was closed January 3, 1975.
Our study of the surface indications led to the conclusion that they were the result of intergranular attack by a corrosive en-vironment.
The probable contaminating media, the marine at:mosphere, was admitted to the nozzle surfaces during on-site storage by the absence of a plastic protective cover from the safe-ends. TA possible 8311300037 750115 PDR ADOCK 05000275
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Dr. Donald F. Knuth January 15, 1975 U. S. Atomic Energy Commission Page 2 contributing media was an aluminum paint, Harris Paint Company (type TTP-28).
Analysis of a paint sample determined it to contain 200 ppm chloride.
The aluminum paint was applied to the safe end surfaces for storage protection as a substitute for the plastic liquid envelope.
To preclude a recurrence of the problem the following pro-cedures were adopted:
1.
The aluminum paint was removed mechanically and the safe ends cleaned with acetone.
Visual and liquid penetrant examinations were made.
They were then covered by a plastic liquid envelope.
2.
In preparation for welding of the primary loop piping the plastic envelope was removed from the safe ends, which were cleaned with acetone followed by a demineralized water rinse.
When welding operations were not in progress, the safe ends and weld junctions were protected with sheet polyethylene covering.
3.
Prior to insulation stainless steel areas were cleaned with acetone followed by a demineralized water rinse.
The cleaned areas were tested to assure chlorine and fluorine levels not greater than 0.0015 mg C1/dm2 and 0.0015 mg 2
Fl/dm, respectively.
These steps have been incorporated in the installing con-tractor's erection procedures to assure a clean system during' storage, erection and operation.
PGandE, Westinghouse and the installing contractor have re-viewed Quality Assurance procedures pertaining to receipt, storage and installation of equipment, and appropriate changes have been made..to strengthen the program to preclude occurrences of a similar nature in the future.
Field engineering and inspecting personnel have been re-familiarized with the quality requirements of construction activities and have been impressed with the necessity to ensure full and complete compliance with program requirements.
7 Very truly yours, 92 l
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Mr. R. H. Engelken, Director Directorate of Regulatory Operations Region V k*
All parties, Board members, Richard L. Black, Angelo Giambusso, Nathaniel H. Goodrich, Alan S. Rosenthal, Secretary-Docketing and Service Section, James R. Yore L.
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