ML20113E589
| ML20113E589 | |
| Person / Time | |
|---|---|
| Site: | Bellefonte  |
| Issue date: | 03/20/1985 |
| From: | Hufham J TENNESSEE VALLEY AUTHORITY |
| To: | Grace J NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II) |
| References | |
| REF-PT21-85, REF-PT21-85-218-000 PT21-85-218, PT21-85-218-000, NUDOCS 8504160537 | |
| Download: ML20113E589 (2) | |
Text
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TENNESSEE VALLEY AUTHORITY
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"9 M'addh :)p7,J90 BLRD-50-438/84-48 BLRD-50-439/84-44 U.S. Nuclear Regulatory Cmmission Region II Attn:
Dr. J. Nelson Grace, Regional Administrator 101 Marietta Street, NW, Suite 2900 Atlanta, Georgia 30323
Dear Dr. Grace:
BELLEFOITE NUCLEAR PLANI LNITS 1 AND 2 - INAIEQUATE PESSURIZER SUPPORT ATTAGENTS - BLRD-50-438/84-48 AND BLRD-50-439/84 FINAL EPORT The subject deficiency was initially reported to NRC-0IE Inspector P. E. Fredrickson on Septaber 6,1984 in accordance with 10 TR 50.55(e) as NCR BLN GB 8413 Our first interim report was submitted October 9,1984.
Enclosal is our final report. We consider 10 TR 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 VALLEY AUTHORITY
./
prd. W. Hufham, Manager Licensing and Regulations Enclosure cc:
Mr. James Taylor, Director (Enclosu e)
Office of Inspection and Enforcement U.S. Nuclear Regulatory Cmmission Washington, D.C.
20555 o
Records Ceter (Enclosure)
Institute of Nuclear Power Operations 1100 circle 75 Parkway, Suite 1500 Atlanta, Georgia 30339 8504160537 850320 PDR ADOCK 05000438 g
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An Equal Opportunity Employer N
ENCLCSURE *
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r BELLEFWTE NUCLEAR PLANT UNITS 1 AND 2 INADEQUATE PRESSURIZER SUPPORT ATTACHIENTS BLRD-50-438/84-48, BLRD-50-439/84-44 NCR BLN GB 8413 10 TR 50.55(e)
FINAL REPORT Description of Deficiency TVA has determined that the pressurizer's upper support wall attachments are These two wall attachments are part of Babcock and Wilcox's inadequate.
(B&W) support scheme for the pressurizer, and each attachment utilizes two These shear bars are separated from the wall attachment's anchor shear bars.
plates by gaps which allow for thermal growth of the upper support menber.
Because of these gaps, each wall attachment would see a loss of coolant accident (LOCA) induced load separately. However, because LOCA load analysis asstrued the attachments would see a LOCA-induced load simultaneously (i.e.,
did not account for these gaps), the actual load at each support point is j
approximately twice the design load.
A second problem involving the shear bars also exists in that original design calculations called for dimensions on the shear bar which are larger than those called for in the current plant design. As a result of these reduced dimensions, the required shear strength cannot be developed from the shear bars.
The principal cause of this problem was the inadequate substantiation of the design asstrnption by B&W personnel concerning the suitability of the gap l
between the shear bar and the anchor plate with a contributing factor being l
an ' inaccurate transfer of documentation (a change of the shear bar and associated weld geometries from a B&W stress report) to construction drawings.
Safety Inclications y
The underdesigning of the pressurizer upper support wall attachments could allow these attachments to fail during a LOCA. This failure could then allow greater than expected movements of the pressurizer vessel which could lead to damage of nearby safety-related equipnent and piping. This damage could then adversely affect the safe shutdown of the plant.
Corrective Action B&W has issued field change package (FCP) 295, which provides for the removal of the existing shear bars and for replacement with shear bars designed to be mounted flush to the anchor plates and to resist all applied load conditions.
This new design also provides for a sharing of loads by the embedded plates at the tm wall attachments. All work to install these new shear bars is completed for unit 1 and is scheduled to be completed by June 20, 1987 for unit 2.
l
BW has informed th3 managers responsible for the design stress analysis and ths gensration of Icads for reactor coolant %ystem (RG) supports and restraints to increase their personnel's awareness of the need to substantiate design asstrnptions. Also, BW will promptly inform TV A by letter of any design changes that may affect hardware geometry, welding, etc.