ML20081L986
| ML20081L986 | |
| Person / Time | |
|---|---|
| Site: | Bellefonte  |
| Issue date: | 11/10/1983 |
| From: | Mills L TENNESSEE VALLEY AUTHORITY |
| To: | James O'Reilly NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II) |
| References | |
| REF-PT21-83 10CFR-050.55E, 10CFR-50.55E, NUDOCS 8311170010 | |
| Download: ML20081L986 (2) | |
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' TENNESSEE VALLEY AUTHORITY CHATTANOOGA. TENNESSEE 374of 400 Chestnut Street Tower II 0 3 fl0 V I4 m g *. 2 2.l November 10, 1983
- 'BLRD-50-438/82-45
'n-LBLRD-50-439/82-41' U.S. Nuclear Regulatory Coinnission Region II:
Attn:
.Mr. James P. O'Reilly, ' Regional Administrator
.101 Marietta Street, NW, Suite 2900
' Atlanta, Georgia 30303
Dear Mr. O'Reilly:
'.BELLEFOMTE NUCLEAR PLANT UNITS 1 AND 2 - BABCOCK & WILCOI DESIGN OF REACTOR C00LA57 SYSTEM SUPPORTS AND RESTRAINTS - BLRD-50-438/82-45,
-BLRD-50-439/82 FINAL REPORT
~
The subject deficiency was initially reported to NRC-0IE Inspector R. V. Crlenjak on June 18, 1982 in accordance with 10 CFR 50.55(e) as NCR BLN BLP 8220. This was followed by our interim reports dated July 19, Septemb' r 24, and December 20, 1982 and June 20, 1983 Enclosed is our e
final report. We consider 10 CPR Part 21 applicable to this deficiency.
If you have any questions concerning this matter, please get in touch with
. R. H. Shell at FTS 858-2688.
Very truly yours, TENNESSEE VALLEY AUTHORITY 83'11'17001'O B311 gDRADOCK05000bs L. M. Muls, k nager PDR Nuclear Licensing Enclosure-l cc (Enclosure):
Mr. Richard C. DeYoung, Director Office of Inspection and Enforcement U.S. Nuclear Regulatory Commission Washington, D.C.
20555 Records. Center Institute of Nuclear Power Operations 1100 Circle 75 Parkway, Suite 1500
- Atlanta, Georgia 30339 j.
Babcock & Wilcox Company P.O. Box 1260 Y..
$pCWg'@'
Lynchburg, - Virginia 24505 g
. Attention:
Mr.~H. B. Barkley 1983-TVA' 50rH ANNIVERSARY
[E.
1 An Equal Opportunity Employer
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r-ENCLOSURE BELLEFONTE NUCLEAR PLANT UNITS 1 AND 2 BABCOCK & WILCOX DESIGN OF REACTOR COOLANT SYSTEM SUPPORTS AND RESTRAINTS NCR BLN BLP 8220 BLRD-50-438/82-45, BLRD-50-439/82-41 10 CFR 50.55(e)
FINAL REPORT Description of Deficiency The Babcock & Wilcox (B&W) of Lynchburg, Virginia, design of Reactor Coolant System (RCS) supports and restraints was based on an erroneous assumption at the B&W-TVA interface. The B&W stress report for the RCS supports and restraints assumes that the TVA-supplied embedments are of equivalent strength to the B&W-designed attachments (FY = 50 ksi). TVA-supplied embedments are of lesser strength (FY = 36 ksi). Thus, welds and shear bars at the interface points are potentially undersized and overstressed.
This deficiency resulted from B&W's failure to adequately check the transfer of interface information from TVA embedment drawings to the B&W stress report.
There have been no similar deficiencies in the past for B&W-designed supports and restraints.
Safety Imolications Had this condition remained uncorrected, the erroneous assumptions made by B&W in the design of the RCS supports and restraints could have resulted in undersized and overstressed welds and shear hars.
This condition jeopardizes the integrity of the RCS system. Thus, this condition could have adversely affected the safe operation of the plant.
Corrective Action Independent review of the supports and restraints stress report by both TVA and B&W has confirmed that the nonconforming condition is applicable only to the shear block us ;d on the hot leg elbow restraint (mark No.10-18 on TVA drawing 1RN0430-X2-16). The original SA-533 shear block will be replaced for both units 1 and 2 with the A36 shear block using " Method 1" in attachments 1 and 2 of B&W letter D-4475.
The strength of the A36 shear bar material matches that of the embedment. The new shear bar design makes up for the decrease in the strength of the shear bar material by increasing the amount of weld surface. Postweld heat treatment is not required for this design.
The redesigned shear bar and the use of the correct yield strength in the stress report constitute the corrective action. This shear block replacement will be accomplished by September 15, 1984, for unit 1 and March 15, 1986, for unit 2.
The action taken by B&W to prevent recurrence is to require full documentation of all input data in the stress report. B&W will revise the. stress report.