ML20009G693

Final Deficiency Rept Re Expansion Anchor Failures, Originally Reported on 810310.Caused by Reduced Concrete Strength Due to Surface Drying & High Air Content.Anchor Replacement Will Be Completed by 811030

ML20009G693
Person / Time
Site:	Bellefonte
Issue date:	07/27/1981
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, NUDOCS 8108040557
Download: ML20009G693 (3)

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400 Chestnut Street Tower II July 27, 1981 BLRD-50-438/81-23 BLRD-50-439/81-25 '

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b g Mr. James P. O'Reilly, Director g7fghJ * * -

Office of Inspection and Enforcement .

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U.S. Nuclear Regulatory Coc: mission -

g Region II - Suite 3100 %j.\ u.s.qgy),s'$s ,ec 101 Marietta Street /,^ y Atlanta, Georgia 30303 (4X.L R '. G^ s w}g/

Dear Mr. O'Reilly:

BELLEFONTE NUCLEAR PLANT JNITS 1 AND 2 - EXPANSION ANCHOR FAILURES -

BLRD-50 438/81-23, BLRD-50-439/81 FINAL REPORT The subject deficiency was initially reported to NRC-0IE Inspector R. V. Crlenjak on March 10, 1981 in accordance with 10 CFR 50.55(e) as NCR 1381. This was followed by our first interim report dated April 9, 1981. Enclosed is our final report.

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 AUTfJRITY l

l L. M. Mills, Manager l Nuclear Regulation and Safety Enclosure cc: Mr. Victor Stello, Jr., Director (Enclosure) l Office of Inspection and Enforcement f U.S. Nuclear Regulatory Commission -$ 6 l Washington, DC 20555 5

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l 8108040557 810727

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FMCLOSURE BELLEFONTE NUCLEAR PLANT UNITS 1 AND 2 i

EXPANSION ANCHO.R FAI4URES  ;

l BLRD-50-438/81-23, BLRD-50-439/81-25 i 10 CFR 50.55(e)

FINAL REPORT Description of Deficiency j

i TVA General Construction Specification No. G-32 covers the installation and

testing of expansion shell anchors installed into hardened concrete. It requires inprocess testing of samples of anchors installed by a specific

! crew either in a specific location or over a period of time. The anchors i are proof loaded in tension to about 2 3 times the maximum design service load for the particular size of anchor.

For anchors installed in the M and P line walls of the Control Building between column lines C8 and C10, the rate of proof load failures was l excessive. A total of 36 of 68 3/4-inch anchors failed the proof load i test. Exc(pt for a few 1/4-inch anchors installed for small conduit, 3/4 inch was the only size used in these walls.  ;

Safety Implications a /

Failure of these anchors could lead to failure of the systems being supported by the anchors. As these systems may be safety related or their '

i failure could affect safety-related functions, the failure of the systems could adversely affect safety of operations of the plant.

{ Corrective Action i Six cores were taken from the M- and P-line walls in the area where the l excessive failures occurred. Three cores were also taken from a wall where

anchor failure rates were acceptable. The results showed that some areas

of the M- and P-line walls had unexpectedly low strength. The cores were

3-inch diameter by 3 inches long with one end being the wall surface. Tbe compressive strengths of the six cores ranged from 2200 to 4100 lb/in 2 l (corrected for length effects). Visual examination of some cores revealed I that about a 1-inch layer adjacent to the surface had a slightly different

! color than the remainder of the core.

t Review of concrete placement records indicates that the concrete was not I

damaged by freezing and was apparently cured in accordance with specifications. The records also showed that the air contents were at near the specified maximum. The color difference probably indicates a significant difference in the degree of hydration near the surface.

l This may indicate that curing compound was not uniformly applied or some localized drying occurred before application of the compound. The

, combination of reduced strength resulting from surface drying and high air content is the probable cause for the excessive failures.

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The proof load test reports for the period October 1980 through December 1980 were reviewed. There was no evidence that a problem existed with the 3/4-inch Phillips self-drilling anchor or that the crew used improper installation procedures.

All 3/4-inch self-drilling anch'>rs in the M- and P-line walls between column lines C8 and C10 and between elevation 680 and 687 will be replaced with wedge bolt or grouted anchor, , The wedge bolts and grouted anchors are embedded deep enough to ensure tha the reduced strength of the surface will not affect their capacity. Replacement will be completed by October 30, 1981.

As overall concrete strength is adequate to perform its safety function, no corrective action is required for the lower strength concrete areas.

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