ML20133N965
| ML20133N965 | |
| Person / Time | |
|---|---|
| Site: | Bellefonte  |
| Issue date: | 07/09/1985 |
| From: | Hufham J TENNESSEE VALLEY AUTHORITY |
| To: | Grace J NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II) |
| References | |
| REF-PT21-85, REF-PT21-85-362-000 PT21-85-362, PT21-85-362-000, NUDOCS 8508140076 | |
| Download: ML20133N965 (2) | |
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9 1-i TENNESSEE VALLEY AUTHORITY CH ATTANOOGA. TENNESSEE 37401 1630 Chestnut Street Tower II July 9, 1985 BLRD-50-438/85-11 c_.
BLRD-50-439/85-11 U.S. Nuclear Regulatory Commission Region II
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Attn:
Dr. J. Nelson Grace, Regional Administrator ca 101 Marietta Street, NW, Suite 2900 Atlanta, Georgia 30323 cn t
Dear Dr. Grace:
BELLEFONTE NUCLEAR PLANT UNITS 1 AND 2 - CRACKSD CYLINDER BLOCK ON TDI DIESEL GENERATORS - BLRD-50-438/85-11 AND BLRD-50-439/85 FINAL REPORT i
i The subject deficiency was initially reported to NRC-OIE Inspector Al Ignatonis on March 18, 1985 in accordance with 10 CFR 50.55(e) as i
NCR 4030. This was followed by our first interim report dated April 12, j
1985. Enclosed is our final report. We consider 10 CFR Part 21 applicable i
to this deficiency.
i If you have any questions, please get in touch with R. H. Shell at j
FTS 858-2688.
Very truly yours, I
TENNESSEE VALLEY AUTHORITY
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.d.w
- 6. W. Hufham, Manager Licensing and Risk Protection 1
Enclosure cc (Enclosure):
Mr. James Taylor, Director Office of Inspection and Enforcement U.S. Nuclear Regulatory Conunission Washington, D.C.
20555 Records Center Institute of Nuclear Power Operations 1100 circle 75 Parkway, Suite 1500 Atlanta, Georgia 30339 i
i 8508140076 850709 PDR ADOCK 05000438-5 PDR J
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3 An Equal Opportunity Employer I h c7 7
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ENCLOSURE BELLEFONTE NUCLEAR PLANT UNITS 1 AND 2 CRACKED CYLINDER BLOCK ON TDI DIESEL GENERATORS 4
BLRD-50-438/85-11 AND BLRD-50-439/85-11 NCR 4030 10 CFR 50.55(e)
FINAL REPORT 4
i Description of Deficiency Upon the recommendation of the TDI Diesel Generator Owners Group, TVA implemented an extensive inspection and maintenance program that revealed cracks in components that would not ordinarily require inspection. Diesel generator 1B contained two cracks in the cylinder block extending 1-1/2-inches up the lip of the cylinder liner landing surface and 5/8-inch across the top of the block.
The exact cause of the cylinder block cracks cannot be determined. Trace 2
casting contaminants leading to degenerate graphite structure and reduced i
fatigue resistance properties have been identified by the TDI Diesel 1
Generator Owners Group as the most likely root cause of block cracking in TDI engines. However, since the cracked block at Bellefonte Nuclear Plant (BLN)
I exhibited only a relatively minor amount of degenerate graphite structure and had cracks only in the area of one cyliner, we feel that this is not the cause of cylinder block cracking. The cylinder block cracking is probably due to the very small cylinder liner to block clearance and a galled wrist pin and piston skirt assembly.
Sa fety Implications This type of cylinder block cracking has been analyzed by Failure Analysis
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Associates for the TDI Diesel Generator Owners Group and is considered to be l
a ligament crack. Extensive operating experience at other plants demonstrates that ligament cracks arrest at the cylinder liner landing and i
have no effect on engine operation because the cracks are fully contained between the liner and the block material beyond the cylinder head 1
i stud holes. Based on this, the condition is not considered to be detrimental to the safe operation of the plant.
Corrective Actions Corrective actions are not required to be taken since the cylinder block cracking is not detrimental to the diesel engine and the cracks are not expected to propogate.
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TVA and Transamerina Delaval have implemented the following actons to prevent the recurrance of future cracking in the diesel engine cylinder blocks.
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TVA has increased the clearance between the cylinder block and liner to reduce stress in the cylinder block on all BLN engines.
2.
TVA has replaced the galled piston skirt assembly and wrist pin in the affected cylinder.
3.
TVA will monitor the existing cracks for propogation.
4.
TVA will periodically inspect the cylinder block for additional cracks.
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5.
TDI has incorporated production changes to decrease stress in the cylinder block. These changes were to increase the cylinder block to liner clearance and increase the depth of cylinder stud bosses and the i
depth of stud hole threads.
6.
TDI has incorporated product enhancements to increase the cylinder block top thickness and improve material from the original class 40 to class 45 cast iron.
These changes will increase the allowable stress of the cylinder block.
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