ML063420609

Powerpoint: Oyster Creek 1R21 Outage Startup PORC Update on Drywell Shell Inspections November 4, 2006 (PA)

ML063420609
Person / Time
Site:	Oyster Creek
Issue date:	11/04/2006
From:	- No Known Affiliation
To:	Office of Nuclear Reactor Regulation
References
%dam200701, TAC 8261
Download: ML063420609 (16)

Text

Oyster Creek 1R21 Outage Startup PORC Update on Drywell Shell Inspections November 4, 2006 11/4/2006 I

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Agenda

° Issues Identified

" External Questions and Concerns

" Actions Initiated

" Corrective Actions

° Drywell Shell Integrity

" Conclusions

° Next Steps

° Reference Drawings 11/4/2006 2

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Issues Identified

• Standing water was identified in the trench inside the Drywell at the Drywell floor level in Bay'5 when the foam fill was removed for planned inspections.

• Dampness was identified in the other trench in bay 17, however, no standing water was present.

11/4/2006 3

Q (. C Actions Initiated

• Performed detailed drawing reviews to identify potential sources of water

• Obtained water samples and performed lab analysis

• Performed in plant inspections to identify potential leakage paths

• Performed a dye tracer test in the sub pile room trough to determine leakage source 11/4/2006 5

Actions Initiated continued "

• Removed additional concrete to perform UT exams to determine any impact to the Drywell shell

• Prepared a comprehensive engineering evaluation to evaluate the impact of water on the Drywell shell integrity

° Performed field repairs and modifications to mitigate future water intrusion 11/4/2006 6

Corrective Actions

• Inspection of the stainless steel liner (VT_ 1) of the Drywell floor drain sump confirmed that the liner remains leak tight.

• Sealed the concrete curb to Drywell shell interface at the perimeter of the Drywell with approved caulking materials.

• Repaired leakage paths in the sub pile room. drainage trough

° Caulked the. concrete to Drywell shell interface in bay #5 and #17 trenches

• Performed a-post modification leakage test of-the trough-to confirm the repairs were adequate 11/4/2006 7

( C Drywell Shell Integrity Review

• Engineering evaluations were developed to evaluate the current acceptability of the drywell shell

" Specific areas evaluated included:

- Detailed field walk-downs and inspections Chemistry sample analysis of the water in-the bay #5 trench

- Non destructive and visual examinations.of the Drywell shell.

in both trenches and on the exterior side in the sand bed region.

- Removal of additional concrete on the bottom of bay #5 trench and completion of non destructive and visual examinations

- A corrosion evaluation of the Drywell shell steel, in contact with concrete in the presence of water -

11/4/2006 8

( ( (k Conclusions

" Investigations concluded that the likely entry point for the water was a deteriorated connection at the sub-pile room drainage trough

• Non destructive exams confirmed that the drywell shell thickness maintains adequate margin by exceeding the required minimum wall thickness

" Established that the drywell shell structural integrity is not impacted by continued water in the drywell elevation 10'-3" concrete

• Drywell structural integrity is maintained and continues to meet all of its design bases requirements

• Will perform additional inspections during 2008 refueling outage 11/4/2006 9

( C C Next Steps

• Technical Evaluation Updates and Completion

• Evaluations Support Current Restart Schedule

• Notifications to Stake-holders

• Ongoing Communications with NRC & State officials

.11/4/2006 10

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Reference Drawings 11/4/2006 11

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Sandbed region is located on the exterior of L

Drywell Trenches located in crete at two locations inside the concrete floor inside the "to gain access -to..the drywell shell adjacent to the sand bed region. The purpose of clearing Drywell in two locations out the area was to obtain UT thickness measurements.

11/4/2006 12

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Top View - Drywell Floor Sketch" 11/4/2006 13

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Plan View of Trough and Trenches SEE DETAIL-J" CROSS SECTIONt AREA.

OF xmaemm KEY PLAN, tSCft~q Mw 11/4/2006 14

K K SKETCH SHOWING LOWER DRYWELL-SAND BED, TRENCH &SUMP

-H.P. V-9 5ECTION 1113"- 1113 L.P'. 6--Pu LOOK(ING WfE5T DRAINAGE CHANNEL

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Trench Detail Sketch LIGHT DENSI' SILICONE INC.

T/CURB DRYWELL M,_EL. 1I'-0" VARIES RTV FOAM CROSS-SECTION AREA OF TRENCHES IN BAYS 5 & 17 11/4/2006 17

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External Questions and Concerns

• Analysis of data from 2 UT measurements in upper region

• Previously unidentified construction issues (voids, cracks) effect on design bases/assumptions

• Completion of repairs prior to completion of evaluations

• Assurance that corrosion has been arrested (water and iron oxide present in trench)

• Questions were reviewed and addressed during combined 11AMrGen, NRC and State meeting on 11/3/2006 4