ML20040C825
| ML20040C825 | |
| Person / Time | |
|---|---|
| Site: | Bellefonte  |
| Issue date: | 01/18/1982 |
| From: | Mills L TENNESSEE VALLEY AUTHORITY |
| To: | James O'Reilly NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II) |
| References | |
| 10CFR-050.55E, 10CFR-50.55E, NUDOCS 8201290279 | |
| Download: ML20040C825 (3) | |
Text
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e TENNESSEE VALLEY AUTHORITY NRC REGL'A' i-
^ NT4, GE0nd CH ATTANOOGA TENNESSEE 37401 400 Chestnut Street Tower II January 18,(982IMJ 21 A 9 2*
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4 RECENED Mr. James P. O'Reilly, Director
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Dear Mr. O'Ibilly:
BELLEEONTE NUCLEAR PLANT UNITS 1 AND 2 - BtTI'KNHEADS ON ROCK ANCHOR THOONS -
C-N NCR 1257 - FINAL REPORP We subject nonconformance was initially reported to NIC-OIE nspector R. W. Wright on September 23, 1980 in accordance with 10 CFR 50.55(e). %is was followed by our interim reports dated October 23 and December 29, 1980 and April 27 and October 7, 1981. Enclosed is our final report.
If you have any questions concerning this matter, please get in touch with R. H. Shell at FIS 858-2688.
Very truly yours, TENNESSEE VALLEY AITINORITY
. M. Mills, Man,er Nuclear Regulation and Safety Enclosure cc: Mr. R. C. DeYoung, Director (Enclosure)
Office of Inspection and Enforcement U.S. Nuclear Regulatory Cmmission Washington, DC 20555 l
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z ENCIDSURE BELLEFONTE NUCLEAR PIANP UNITS 1 AND 2 BUTIONHEADS ON ROCK ATHOR TENDONS 10 CFR 50.55(e)
NCR 1257 FINAL REPORT Description of Deficiency Inspection of the rock anchor tendon anchorheads in unit 1 indicates that sane of the tendon wire buttonheads may not be properly seated on the anchorhead.
Buttonheads have been found raised approximately 1/8 inch higher than they should be.
Raised buttonheads can be an indication of a broken or overstressed wire, double buttonheading caused by a slip of the buttonheading machine, or buttonheads that are bearing on adjacent buttonheads.
Safety Implications As a result of TVA's inspection of the subject raised buttonheads and subsequent analysis, it has been determined that the affected tendons will be able to perform their intended safety function. % us, there is no condition adverse to the safety of operations of the plant.
Corrective Action We fourth interim report on this deficiency detailed the results of the inspection of 175 of the unit 2 rock anchor tendons. All 185 unit 2 rock anchor tendons have now been inspected. Following is a sumary of the findings.
Of the 185 unit 2 teMons inspected, 8 teMons had one or more raised buttonheads as follows:
A.
Six tendons had one raised buttonhead.
B.
One tenSon had two raised buttonheads.
C.
One tendon hM three raised buttonheads.
All of these raised buttonheads have an oversized diameter and are seated on adjacent buttonheads. As such, the tendon wires are considered acceptable and no adjustments will be made to stress levels in the unit 2 vertical tendons as a result of raised buttonheads. %e raised buttonheads are not evidence of wire failure in unit 2.
%us, there is no corrective action required for unit 2 as a result of this deficiency.
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o i For unit 1, corrective action was taken as delineated in the third interim report on this deficiency. W erein, it was stated that the tendon stresses would be reduced for 28 unit i vertical tendons because of raised buttonheads on the rock anchor tendons. It should be noted that the raised buttonheads were not checked to determine whether they were seated or unseated. Instead, each wire affected was conservatively conside:ed to have failed and the tendon stress levels were to be reduced. '1Venty-two of these 28 tendons have had their stress levels appropriately reduced. W e stresses for the remaining 6 of these 28 tendons have not yet been reduced and will not be reduced as discussed below.
W e conservative assumption of wire failure because of raised buttonheads is not supported by the unit 2 data.
It is likely that the stresses in the unit 1 tendons did not need to be reduced. W e six remaining tendons (and the 22 for which stress levels were reduced) also had oversized buttonheads which apparently caused the raised condition and not overstressed wire. For this reason, the remaining six tendons in unit I will not have stress levels reduced.
To prevent recurrence of possible overstressing, the posttensioning contractor, Inryco, instituted a procedural ci.ange, Inryco EUR #17. Were is now a requirement to inspect each anchorhead on every tendon after stressing and document any raised buttonheads.
All corrective action for this deficiency is canplete. Corrective action to prevent recurrence has been taken. TVA has no other nuclear plants with a prestressed containment. %us, no other TVA nuclear plants are affected.
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