ML20005A539

Third Interim Deficiency Rept Re Buttonheads on Rock Anchor Tendons,Initially Reported on 800923.Group 1 Tendon Stresses Will Be Reduced to Prevent Possible Overstress.Next Rept Will Be Provided by 811014

ML20005A539
Person / Time
Site:	Bellefonte
Issue date:	04/27/1981
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, NCR-1257, NUDOCS 8106300438
Download: ML20005A539 (3)

Text

.

o ,

400 Chestnut Street Tower II April 27, 1981 Mr. J P. O'Reilly, Director Office of pection and Enforcement U.S. Nucl egulatory Comission Regien II - S to 3100 101 Marietta S eet Atlanta, Georgia 30303

Dear Mr. O'Reilly:

BE1.LEFONTE NUCLEAR PLANT UNITS 1 AND 2 - BUTTONHEADS ON ROCK ANCHOR TENDONS

- NCR 1257 - THIRD INTERIM REPORT The subject nonconformance was initially reported to NRC-0IE Inspector R. W. Wright on September 23, 1980, in accordance with 10 CFR 50.55(e).

This was followed by our interim reports dated October 23 and December 29, 1980. Em:losed is our third interim report. We expect to submit our next written report by October 14, 1981.

If you have any questions concerning this matter, please*get in touch with' "

D. L. Lambert at FTS 857-2581. ,

Very truly yours, TENNESSEE VALLEY AUTHORITY L. M. Mills, Manager Nuclear Regulation and Safety Enclosure oo: Mr. Victor Stallo, Jr., Director (Enclosure) [

Office of Inspection and Enforcement ,

U.S. Nuc3sar Regulatory Comission Washington, DC 20555 fl l

f.s \ . -

8106300 %1 S

ENCLOSURE BELLEFONTE NUCLEAR PLANT UNITS l'AND 2 BUTTONHEADS ON ROCK ANCHOR TENDONS NCR 1257

' ~- .

10 CFR 50.55(e)

THIRD INTERIM REPORT Description of Deficiency -

Inspection of the rock dichor tendon anchorheads in unit 1 indicates some 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 buttonhendind machine, or buttonheads that are bearing on adjacent buttonheads.

Interim Progress The 185 unit 1 rock anchor tendons have been inspected, and the inspection reveals 32 tendons had one or more raised buttonheads as follows:

(A) 18 tendons had one raised buttonhead )

(B) 7 tendons had two raised buttonheads ) Group I .

i (C) 3 tendons had three' raised buttonheads ) *

, (D) 2 tendons had four raised buttonheads ) *

(E) 1 tendon had six raised buttonheads ) Group II

'(F) 1 tendon had nine raised bu,ttonheads )

1 For purposes,of clarity, it is convenient to group the 28 tendons referenced in items A through C as group I, and those in items D through F as group II.

Double buttonheads are permitted and were in.spected for diameter but were not inspected for buttonhead height. It is not possible to grip the raised buttonheads to see if the wire .is loose. A review of the buttonheading cards indicated there is no direct correlation between double buttonheads and raised buttonheads for each affected tendon. On items E and F (the

. tendons that had six and nine raised buttonheads) there were four and six double buttonheads, respectively.

The group I tendons (that have three or less raised buttonheads) will not be reinspected. Each wire of. group'I will be conservatively considered to

< have failed, and the tendon stresses will be reduced according to the percentage of raised buttonheads to prevent any possible overstress.

^

The group II tendons 2.(all having greater than three rsised buttonheads)

( were reinspected to determine if the buttonheads were seated or unseated.

I Item F (the tendon having nine raised buttonheads) was reinspected and found to have only seven raised buttonheads. These seven tuttonheads had

. an oversized diameter and were resting on adjacent buttonheads. The buttonheads were not loose and were. determined to be bearing on adjacent buttonheads by the use of a feeler gtuge.

i s-

- . . . - - - . - - - = . _- - . - - - . - . .

- o For the other three tendons in group II '(items D and E), the reinspections determined the following:

1. Tendon having six raised buttonheads (item E) - All raised buttonheads had an oversized diameter and were seated on adjacent buttonheads.

2. Tendons having four raised buttonheads (iteE~D) - One tendon has four oversized diameter buttonheads bearing on adjacent buttonheadse The other had two oversized diameter buttonheads bearing on adjacent buttonheads and two double buttonheads seated on the anchorhead.

The raised buttonheads that are bearing on adjacent buttonheads are hot properly seated on the anchorhead. For the raised buttonheads for these group II tendons, the wires are considered acceptable because the buttonheads of these wires had an oversized diameter and were effectively seated on adjacent buttonheads as indicated by the feeler gauge testing. ,

The tendon stresses in these vertical tendons coupled to the rock anchor tendons need not be adjusted during the containment prestressing because the four group II tendons (tendons with the greatest number of raised buttonheads) were reinspected and no wire failure was found.

The inspection of unit 2 tendens will be performed concurrent with the contractor's installation of unit 2 vertical tendons.

O 9

e e

e S

e i

- -,