ML063420609
| 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 1 R21 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.
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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
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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
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(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
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C Next Steps
- Technical Evaluation Updates and Completion
- Evaluations Support Current Restart Schedule
- Notifications to Stake-holders
- Ongoing Communications with NRC & State officials C
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Reference Drawings 11/4/2006 11
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Sandbed region is located on the exterior of Drywell L
Trenches located in concrete floor inside the Drywell in two locations crete at two locations inside the "to gain access -to..the drywell shell adjacent to the sand bed region. The purpose of clearing out the area was to obtain UT thickness measurements.
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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
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SKETCH SHOWING LOWER DRYWELL-SAND BED, TRENCH & SUMP
-H.P. V-9 L.P'. 6--Pu DRAINAGE CHANNEL 5ECTION 1113"- 1113 LOOK(ING WfE5T
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Trench Detail Sketch LIGHT DENSI' SILICONE INC.
DRYWELL T/CURB 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