ML20207L158

Final Part 21 & Deficiency Rept Re Design Problems W/B&W Steam Generators.Initially Reported on 820830.Nozzles Supplying Auxiliary Feedwater to Internal Headers Capped Off & New External Headers Installed to Preclude Failures

ML20207L158
Person / Time
Site:	Bellefonte
Issue date:	06/18/1986
From:	Gridley R TENNESSEE VALLEY AUTHORITY
To:	Grace J NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
References
REF-PT21-86, REF-PT21-86-283-000 PT21-86-283, PT21-86-283-000, NUDOCS 8607300204
Download: ML20207L158 (3)

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• TENNESSEE VALLEY AUTHORITY CHATTANOOGA. TENNESSEE 37401 SN 157B Lookout Place t~. ,

. auncy,: qu BLRD-50-438/82-64 BLRD-50-439/82-57 U.S. Nuclear Regulatory Comission Region II Attn: Dr. J. Nelson Grace, Regional Administrator 101 Marietta Street, NW, Suite 2900 Atlanta, Georgia 30323

Dear Dr. Grace:

BELLEFONTE NUCLEAR PLANT UNITS 1 AND 2 - DESIGN PROBLEMS WITH STEAM GENERATORS - BLRD-50-438/82-64, BLRD-50-439/82 FINAL REPORT The subject deficiency was initially reported to NRC-OIE Inspector D. Quick on August 30, 1982 in accordance with 10 CFR 50.55(e) as NCR BLN NEB 8210.

Enclosed is our final report. We consider 10 CFR Part 21 applicable to this deficiency.

If you have any questions, please get in touch with R. H. Shell at FTS 858-2688.

Very truly yours.

TENNESSEE VAL Y AUTHORITY R. L. Gridley, irector .

Nuclear Safety and Licensing i Enclosure cc: Mr. James Taylor, Director (Enclosure)

Office of Inspection and Enforcement U.S. Nuclear Regulatory Commission Washington, D.C. 20555 l

l Records Center (Enclosure)

! Institute of Nuclear Power Operations 1

1100 circle 75 Parkway, Suite 1500 Atlanta, Georgia 30339 H. B. Barkley, Manager (Enclosure) 205 Plant Project Services Babcock & Wilcox Company P.O. Box 10935 Lynchburg, Virginia 24506-0935 l I

8607300204 860618 PDR ADOCK 05000438

S PDR An Equal Opportunity Employer

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ENCLOSURE BELLEFONTE NUCLEAR PLANT UNITS 1 AND 2 DESIGN PROBLEMS WITH STEAM GENERATORS BLRD-50-438/82-64, BLRD-50-439/82-57 10 CFR 50.55(e)

NCR BLN NEB 8210 FINAL REPORT Description of Deficiency At the July 7, 1982, Babcock and Wilcox (B&W) Owners Group meeting, B&W (Lynchburg, Virginia) indicated that recent inspections of steam generators (SGs) at 177FA B&W operating plants revealed deformation of the auxiliary feedwater (AFW) header and damage to the header supports. There is also evidence of contact between the header and some adjacent SG tubes. The Bellefonte Nu' clear Plant (BLN) header design is similar to the 177FA plant design except that AFW is introduced to the header in the lower portion of the

SG (beneath the steam outlet nozzles) whereas the 177FA plant headers are located toward the top of the SG (in the superheat region). The postulated cause of the deficiency was a sudden drop of the header internal pressure resulting from the injection of a cold slug of AFW into the header while the header was dry.

The root cause of this problem was design error on the part of B&W. In its loading and stress analyses of the internal header, B&W failed to adequately consider those anticipated transients which require initiation of AFW after the steam generator water level has dropped to one foot or less. In these cases, it must be assumed that the internal header is filled with steam when AFW flow is initiated. Under such conditions, the internal header could collapse.

Safety Implications i

Internal damage to the SGs could reduce the SGs ability to dissipate heat from the reactor core, thus, potentially adversely affecting the ability to safely shutdown the reactor. '

Corrective Action The original. internal AFW headers will remain in the steam generators but will not be used. The nozzles which supplied AFW to the internal headers are being capped off. New external headers are being installed to prevent the types of failures experienced with the internal headers at operating plants. Steam condensation in the uninsulated riser pipes connecting the header to the steam generator will keep the header flooded during plant operation.

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Since the external header will be filled with water during operation, the forces associated with the introduction of cold water into steam (which caused failure of the internal headers) will not be present. The capping of the old AFW headers and the installation of the new headers, risers, and restraints are complete on the unit 1 steam generator. TVA has installed new AFW piping inside the D-ring to service the replacement header.

Consequently, the only outstanding work on unit 1 within the scope of the nonconformance is the installation of pipe supports for the new piping.

This remaining unit I work will be completed no later than six months before unit 1 fuel load.

No work, except steam generator and shroud drilling, has been performed on unit 2. Capping of the old AFW headers and permanent installation of the header, risers, restraints, and associated AFW piping and supports will be completed no later than six months before unit 2 fuel load.

Since the Bellefonte AFW headers are being replaced, no other TVA nuclear plants have B&W steam generators and B&W has instituted similar design changes for other steam generators of the same design in nuclear use, no further action is required to prevent recurrence.

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