ML110040408

Buried Piping Inspection Program, IP2 CST Return Line Piping (ACRS - 09/10/09)

ML110040408
Person / Time
Site:	Oconee
Issue date:	09/10/2009
From:	Advisory Committee on Reactor Safeguards
To:
References
FOIA/PA-2011-0021
Download: ML110040408 (10)

Text

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P k-- ý1ý dýý -ý Buried PipingInspection Program I

IP2 CST Return Line Piping

• On February 15, 2009 a leak was identified in the Unit 2, 8" condensate storage tank (CST) return line.

• The leak was below the AFW pump room.

" The floor slab was removed and the leaking pipe was excavated.

" The section of pipe with the leak was replaced and the line was returned to service.

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S ~00 Buried PipingInspection Program I m IP2 CST Return Line Piping

-- Aging Management Program

• As described in the LRA, the IPEC buried piping inspection program is a new program that must be implemented prior to the PEO.

SIdThe foundational elements of the program are being implemented in accordance with an Entergy fleet procedure for buried piping program.

• The program includes all site buried piping including piping in systems that are in the scope of license renewal.

S*The program requires consideration of industry and site operating experience during implementation.

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Buried Piping knspectionProgram I. IP2 CST Return Line Piping

_* Previous Inspections

• In the Fall of 2008, three IP2 CST pipes were exposed at two locations for

tA approximately 10' of each piping run.

An upper location was excavated close to the CST and a lower location was excavated approximately 100' down the hill.

- The three inspected lines were:

(a) 12" line- AFW supply I(b) 8" line - CST return (c) 10" line- CST overflow 39

Buried PipingIn spection Program 1P2 CST Return Line Piping Previous Inspections U. °The inspection of the upper location identified five areas which required coating repairs.

ii i ° The inspection of the lower location identified the need for two minor coating repairs on the 8" and 10" lines.

• UT measurements performed on the exposed sections showed that pipe thickness remains at nominal thickness.

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I0 0 Buried PipingInspection Program IP2 CST Return Line Piping Cause of the leak ANOI S*A failure analysis indicated that the leak in the CST return line was caused by external corrosion.

K

• The corrosion occurred at localized areas of coating damage.

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-4 0 Buried Piping Inspection Program IP2 CST Return Line Piping Contributing Causes P ° The localized failure of the protective coating was caused by rocks introduced during original plant construction.

S°The localized corrosion was exacerbated by the slow soil drainage which results in intermittent submergence of the piping at lower site elevations due to rainfall.

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Buried Piping Inspection Program IP2 CST Return Line Piping Corrective Actions

° In response to the leak, six additional locations is have been selected for inspection. These include Aboth Unit 2 and Unit 3 piping.

- The selected locations include CST and service

!- water piping in locations with similar drainage conditions.

S°Guided wave ultrasonics is the NDE method selected for this inspection.

° Additional inspections or testing will be implemented as appropriate based on the inspection results.

• y The inspections will be completed by October 2009.

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Buried PipingInspection Program

_IP2 CST Return Line Piping jd Industry Operating Experience o A search of industry operating

• q experience was performed for this event using the INPO web.

• Industry OE from this search was noted and the information was considered during the evaluation of this event.

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0 Buried PipingInspection Program iP2 CST Return Line Piping

_* Conclusion I

• There was no safety impact as a result of the leaking CST pipe.

1-0

• The affected pipe remained within the ASME XI

• structural requirements and remained operable.

- Multiple barriers remained in place to ensure that the minimum required CST inventory was maintained.

°2 Monitoring confirmed that the CST level did not drop below the required level as a result of this

_ leak.

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M+/-i Buried Piig Inspection Progr-am Program Improvements

" LRA commitment was to the GALL program, which entailed a limited number of inspections.

" The enhanced program will include multiple inspections.of buried piping both prior to and during the PEO.

" The IPEC program requires that piping segments be classified as high, medium, or low safety significance.

" Under.the program schedule provisions, High impact piping segments will be inspected during the current license -period.

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