ML20202D047
| ML20202D047 | |
| Person / Time | |
|---|---|
| Site: | Bellefonte  |
| Issue date: | 03/20/1986 |
| From: | Gridley R TENNESSEE VALLEY AUTHORITY |
| To: | Grace J NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II) |
| References | |
| NUDOCS 8604110490 | |
| Download: ML20202D047 (3) | |
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TENNESSEE VALLEY AUTHORITY i
SN 157B Lookout Place bl'![b arc
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86 BLRD-50-438/81-07 BLRD-50-439/81-07 U.S. Nuclear Regulatory Commission Region II Attn:
Dr. J. Nelson Grace, Regional Administrator 101 Marietta Street, NW, Suite 2900 Atlanta, Ceorgia 30323
Dear Dr. Grace:
BELLEFONTE NUCLEAR PLANT UNITS 1 AND 2 - CORROSION OF CARBON STEEL PIPING IN THE ESSENTIAL RAW COOLINC WATER SYSTEM - BLRD-50-439/81-07, BLRD-50-439/81-07
- FINAL REPORT The subject deficiency was initially reported to NRC-OIE Inspector F. S. Cantrell on December 30, 1980 in accordance with 10 CFR 50.55(e) as NCR BLN NEB 8010.
Enclosed is our final report. This nonconformance has also been reported for Sequoyah and Watts Bar Nuclear Plants.
If you have any questions, please get in touch with R. H. Shell at FTS 858-2688.
Very truly yours, TENNESSEE VALLEY AUTHORITY s
R. L. Gridley Manager of Licensing Enclosure cc:
Mr. James Taylor Director (Enclosure)
Office of Inspection and Enforcement U.S. Nuclear Regulatory Commission Washington, D.C.
20555 Records Center (Enclosure)
Institute of Nuclear Power Operations 1100 Circle 75 Parkway, Suite 1500 Atlanta, Ceorgia 30339 8604110490 860320
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PDR ADOCK 05000438 s
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An Equal Opportunity Employer
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ENCLOSURE BELLEFONTE NUCLEAR PLANT UNITS 1 AND 2 CORROSION OF CARBON STEEL PIPING IN THE ESSENTIAL RAW COOLING WATER SYSTEM BLRD-50-438/81-07 AND BLRD-50-439/81-07 1
NCR BLN NEB 8010 10 CFR 50.55(e)
FINAL REPORT Description of Deficiency I
j It has been found that the original criteria for the use of carbon steel piping in raw water systems at TVA nuclear plants may not be adequate.
j Corrosion has been found to cause greater than predicted pressure drops when pipes are sized according to standard industry practice.
In addition, the corrosion can cause a thinning of the pipe wall, which may not have been accounted for in the design of the systems. This condition could affect all i
raw water systems with carbon steel piping, such as the Essential Raw Cooling Water (ERCW) system and the High Pressure Fire Protection system (reference NCR BLN MEB 8206, BLRD-50-438/82-65, and BLRD-50-439/82-58).
a Corrosion of carbon steel raw water piping causes greater flow degradation than had been recognized by the industry prior to 1976.
(Such industry standards may be found in technical paper No. 410 published by Crane company and Cameron Hydraulic Data published by Ingersoll-Rand Company).
TVA's initial ERCW system design had been based on those optimistic industry standards.
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The problem of corrosion has been the subject of considerable study at TVA.
This condition was originally discovered on TVA's Browns Ferry Nuclear Plant 1
and is being corrected under NCRs SQN NEB 8035 and WBN NEB 8017 for Sequoyah and Watts Bar Nuclear Plants.
Browns Ferry and Sequoyah Nuclear Plants are currently conducting a surveillance program in order to monitor the capability of their emergency equipment cooling water (EECW) and essential raw cooling water (ERCW) systems.
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Safety Implications The corrosion of carbon steel piping in the ERCW system could affect the capability to remove the specific heat load required of them under the worst condition of two-unit operation.
Failure to remove sufficient heat from the components served by the ERCW could result in loss of equipment necessary for a safe shutdown and therefore could adversely affect the safe operation of the plant.
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! Corrective Action TVA has completed the reevaluation of the Bellefonte ERCW system in accordance with criteria stated in TVA's Office of Engineering (OE) Design i
Guide No. DG-M3.5.1, " Pressure Drop Calculations for Raw Water Piping and Fittings," and found that changes must be made to ensure operability of the system over the plant life. These changes involve applying a cement mortar i
lining to the existins carbon steel yard piping, changing selected pipe i
segments within the buildings to stainless steel, and requalifying certain components for lower flows as discussed in the seventh interim report. The cement mortar lining of the yard piping will be implemented under Engineering l
Change Notice (ECN) 1466. Piping changes will be made under ECN 1457.
As a part of TVA's investigation of corrosion of carbon steel piping detailed in the report entitled " Corrosion in Carbon Steel Raw Water Piping" (attached i
to a letter from L. M. Mills, TVA, to J. P. O'Reilly, NRC Region II, dated August 25, 1981, for Sequoyah Nuclear Plant NCR SQN NEB 8035), the average wall reduction of all. samples was measured and found to be less than 0.040 inch, except for a very few samples where exterior corrosion predominated.
The design of all raw water piping on Bellefonte is such that an average wall reduction of 0.040 inch is acceptable. Therefore, the effects of interior corrosion on the average wall reduction has been accounted for in the design i
of the systems.
Localized corrosion of piping may result in leaks in the systems. However, the anticipated rate of leakage would be quite small in l
comparison to the rated flow of the system, and TVA plans to inspect and/or j
pressure test the piping in accordance with ASME Section XI requirements as part of the in-service inspection program required by the plant technical i
l specifications.
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To prevent recurrence of this deficiency in future systems, pressure drop calculations for future piping systems at BLN and other TVA nuclear facilities will be performed in accordance with the criteria stated in DC-M3.5.1.
j TVA has upgraded the design guide to a design standard, DS-M3.5.1.
Classification as a design standard will ensure that all new pressure drop calculations a
I comply with the criteria as stated in the design standard.
(A design guide is optional and does not ensure compliance with the criteria.) All i
safety-related systems in TVA's other nuclear facilities, either in operation
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or under construction, have been evaluated using the criteria stated in DS-M3.5.1.
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All corrective action required to resolve the deficient condition will be completed at least six months before fuel loading of'the respective units.
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