NRC-96-0012, Special Rept:On 960109,debonded & Damaged Control Ctr HVAC Duct Sealant Found.Areas of Debonded & Damaged Sealant Repaired

Special Rept:On 960109,debonded & Damaged Control Ctr HVAC Duct Sealant Found.Areas of Debonded & Damaged Sealant Repaired

ML20100C030
Person / Time
Site:	Fermi
Issue date:	01/23/1996
From:	Gipson D DETROIT EDISON CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
CON-NRC-96-0012, CON-NRC-96-12 NUDOCS 9601290484
Download: ML20100C030 (3)

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f. , -. Douglas R. Gipson Senior Wce President I fMicar Generahon Detroit r.-

6400 Nort's Duse Highway Newport, Mehigan 48166 (313) 586 & %

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January 23,1996 l NRC-%-0012 l 1

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U. S. Nuclear Regulatory Commission Attn: Document Control Desk Washington D. C. 20555 1

References:

Fermi 2 i NRC Docket No. 50-341 NRC License No. NPF-43 ,

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Subject:

Special Report of Debonded and Damaged Control Center Heating, Ventilation. and Air Conditioning (CCHVAC) Duet Sealant In accordance with Technical Specification 4.7.2.2, this special report is being submitted to describe debonded and damaged CCHVAC duct sealant tiat was .

found on January 9,1996.

On January 9,1996, while performing a visual inspection of CCHVAC duct work silicone sealant required by Technical Specification 4.7.2.2, two areas of debonded sealant were identified by the system engineer:

• Normal intake - Approximately four inches of debonded sealant was identified at a duct companion flange.

• Division 2 Supply Plenum - Approximately four inches of debonded sealant I was identified at a gasketed joint where the duct intersects the plenum.

In both of the above cases, the sealant was applied over gasketed ductjoints over the exposed edge of the gasket. The gasket provides the primary pressure ,

boundary seal for the duct. The gasket appears to be intact and is providing a seal; therefore, both ducts have been judged to be capable of performing their intended function.

9601290484 960123 PDR ADOCK 05000341 S PDR ZUUU(U 3

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. l January 23,1996 NRC-96-0017 Page 2 l l

l These two areas of debonded sealant can most likely be attributed to poor application technique at the time the sealant was applied to the duct. These areas are isolated exceptions and are not representative of the remainder of the sealant applied to the ducts. The remainder of the accessible sealant, hundreds oflinear feet, has been visually inspected with no other areas of debonded sealant identified to date. l The areas of the debonded sealant have been repaired. As required by Technical Specifications 4.7.2.2, these two ducts are subject to annualinspection which ,

would identify any continued degradation. The seams where debonding occurred i will also be inspected quarterly until the next annualinspection.  ;

Three other small areas of sealant subjected to mechanical damage have been ,

identified:

4 e Two sections of sealant each approximately four inches long on top of the duct between filter housings have been subjected to mechanical damage, i.e.,  ;

missing or torn scalant. In both cases the sealant was applied over weld: and  ;

1 mechanical seams. This duct has also been judged to be capable of  !

performing its intended function, e Approximately six to eight inches of sealant located on the top of a gasketed I companion flange on the recirculation duct has been subjected to mechanical j damage. The damage is located at a gasketedjoint where the gasket is the  :

primary seal. Since the gasket appears to be intact, this duct has also been judged to be capable of performing its intended function.

1 The areas of damaged sealant have also been repaired. Any leakage of air into

-_ these ducts would be filtered by the recirculation filter. Because pressure

boundary leakage is not a critical requirement for these ducts, these ducts are not periodically leak tested. However, these ducts are included in the annual visual inspection program.

The CCHVAC ducts with sealant applied that can be a source of unfiltered inleakage are leak tested periodically. The accessible sealant is visually inspected for deterioration annually. The visual inspections are intended to assure that the onset of general deterioration does not go undetected between leak tests.

, January 23,1996 l NR.C-96-0012 i Page 3 i

Based on the visual inspection, the areas of debonded and damaged sealant are I limited to a small fraction of the installed sealant. The remainder of the accessible sealant does not appear to be deteriorated and the CCHVAC duct leakage will remain below the allowable values used in the post accident dose -

calculations. Continued operation is justified because the observed degradation 1 is not indicative of general deterioration and because the observed degradation ,

does not adversely affect the leakage integrity of the system.

The following commitment is made in this letter:

The seams where debonding occurred will also be inspected quanerly until the next annual inspection. >

For further information please contact Mari Jaworsky, Compliance Engineer, at (313) 586-1427.

Sincerely, .

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cc: T. G. Colburn I M. J. Jordan i H. J. Miller i T. Vegel l

Region III  !

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