ML031920229
| ML031920229 | |
| Person / Time | |
|---|---|
| Site: | South Texas  |
| Issue date: | 06/05/2003 |
| From: | Southern Nuclear Operating Co |
| To: | Office of Nuclear Reactor Regulation |
| Thadani M, NRR/DLPM, 415-1476 | |
| Shared Package | |
| ML031920451 | List: |
| References | |
| Download: ML031920229 (45) | |
Text
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Bottom Mounted Instrument Penetration Tube Condition Update cUz1 0
6/503 I
STP Participants Tom Jordan Mark McBumett Steve Thomas Rick Gangluff Michael Lashley Bill Humble Ron Baker Wayne Harrison Ulhas Patil Steve Hunt John Broussard Chong Chiu Ron Latanision John Hall VP, Engineering & Tech Services Manager, Quality & Licensing Manager, Plant Design Manager, Chemistry Test Engineering Supervisor NSSS Supervisor Materials Specialist Licensing Engineer Design Engineer Dominion Engineering Dominion Engineering Performance Improvement Intnl.
Exponent Failure Analysis Assoc.
Westinghouse/CE 6/5103 2
I
INTRODUCTORY REMARKS Mark McBurnett Manager, Quality & Licensing 65/03 3
Agenda Introductory Remarks Progress Summary NDE Activities Cause Analysis and Status Repair Plan Corrosion Assessment Concluding Remarks Mark McBumett Tom Jordan Michael Lashley Steve Thomas Steve Thomas Rick Gangluff Mark McBumett 6/5/03 4
2
I Desired Meeting Outcomes
- NDE results and cause analysis are understood
- Future NDE and testing is understood
- Supporting analyses and schedule are understood
- Documents provided for submittal and inspection are understood
- Future NRC / STP meetings are identified
- NRC questions and needs are clearly understood 65/03 5
PROGRESS
SUMMARY
Tom Jordan Vice President, Engineering & Technical Services 6/5103 6
3
3 Summary Found residue on two BMI penetrations on April 12
-150 mg of residue on Penetration #1 3 mg of residue on Penetration #46 615103 7
6/5M 8
8/5103 8
4
Penetration #1 W5103 9
Penetration #46 6103 10 6/5103 10 5
Efforts to Date
- Completed inside vessel NDE
- Selected vendor; commenced design and preparations for half-nozzle repair
- Continuing with activities under the vessel 615/03 11 Overview of NDE Results
- No cracks found in other penetration tubes
- No surface breaking indication in any J-groove weld 6/5/03 12 6
Planned Activities
- Additional inspection
- Design and repair activities
- Sample removal and analysis
- NRC review
- Cause analysis 6/5/03 13 Key Points
- Careful, deliberate process
- NDE campaign successful
- Condition / repair scope known
- Repairs enable safe return to operation
- Close cooperation with industry and NRC on cause analysis 6/5/03 14 7
NDE ACTIVITIES Michael Lashley Test Engineering Supervisor 6/5/03 15 BMI Guide Tube Penetration l fr 6/5/03 16 8
Base Inspections Scope
- Penetration 1 & 46
- UT from penetration tube ID
- Enhanced visual exam of J-groove weld surface
- Volumetrically interrogate vessel base metal for wastage
- Remaining penetrations
- UT from the penetration tube ID
- Enhanced visual exam of J-groove weld surface 615103 17 STP BMI Approach follows EPRI MRP CRDM Approach
- Define NDE objectives Identify relevant flaw mechanisms Define inspection locations and volumes Define range of flaws to address
- Mockup design and procurement
- Demonstration protocol and schedule Non-blind I blind Detection / sizing I location False calls 615103 18 9
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6/5103 21 Confirmatory Inspection Scope
- Penetration I & 46
- ET from penetration tube ID
- Remaining penetrations
- ET from the penetration tube ID of two other penetrations (2 & 6)
- ET of J-groove weld surface of six other penetrations (9, 12, 33, 34, 38 & 41) 6/5103 22 11
Activities April 21 - May 26
- Mockup fabrication (CIP samples & full scale mockup)
- NRC presentation
- Demonstration / vendor selection
- Demonstration / equipment checkout
- Base scope inspections
- Confirmatory Inspections Demonstrations, base scope inspections, and confirmatory inspections were witnessed by NRC Inspection Team 615103 23 Summary of Results
- Penetration #1
- Three axial indications, one leak path
- No crack-like indications on J-Groove weld
- Visual grinding marks in side of tube
- Penetration #46
- Two axial indications, one leak path
- No crack-like indications on J-Groove weld 6/5103 24 12
Penetration #1 615/03 25 Penetration #46 615103 26 13
UT Examination Probes
- Circumferential probe
- Axial probe
- O-degree mapping 27 615103 Time of Flight Diffracted (TOFD)
Receiver Transmitter 1l-IS Low-amplitude, secondary wave generated by excitation of flaw 6/5/03 28 14
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Penetration #46 Axial Scan 6/503 33 Penetration #46 Leak Path
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Penetration #34 Fabrication Discontinuity 6t5/03 35 615/03 35 Enhanced Visual 6/5/03 36 6/5/03 38 18
Penetration Overview W53 37 Penetration #1 Visual WSWE0 38 6/5103 38 19
Confirmatory Examinations
- Bobbin coil eddy current on penetration ID
- Penetration #1 displayed a tube ID surface-breaking flaw
- Penetration #46 displayed a tube ID sub-surface flaw
- Two other reference penetrations displayed no flaws
- Array coil eddy current on J-Groove weld
- Penetration 1, 46, 33 & 5 others scanned
- No flaws identified 615103 39 Eddy Current Probe Operation
- 18 coil array
- X coil windings
- 2rowsof9coils
- 1.6" coverage Pro l
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Eddy Current Probe 6/5103 41 Eddy Current J-Groove Probe 6/5103 42 21
Calibration Setup
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6/5/03 43 Penetration 33 J-Groove exam 6/5103 22
Additional Confirmatory Inspections and Tests
- Wastage UT (phased array)
- Other
- Rod test
- Bubble test
- Profilometry
- Visual of tube ID
- Visual of vessel bore
- Metallurgical sample
- Boat sample 615103 45 Developing Technology to Identify Wastage 6503 46 23
CAUSE ANALYSIS and STATUS Steve Thomas Manager, Plant Design 6/503 47 What Was Found
- Residue on two nozzles
- Total of five flaws in the two nozzles
- One flaw in each nozzle provides a leak path
- Only one flaw fully penetrated nozzle
- Three embedded flaws
- Discontinuities
- Grinding marks 6/5/03 48 24
Other Observations
- No flaws in the 55* other nozzles
- No evidence of circumferential cracks
- No evidence of ID initiated cracks
- Penetration #31 will be examined during repair 615103 49 Mdd RP Feb. Md.
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PWSCC May Not Be the Cause cx" I
ITta 615103 51 6/5/03 51 Tube Coldworking Not a Likely Contributor 1976 Combustion Engineering Nuclear Fabrication Practice 101-3-0 states:
5.8.1 REMINDER
Use the bull's eye level and alternate welds as necessary to insure alignment 5.8.4 Cold straighten, as necessary, all tubes which are out of alignment 6/5/03 52 26
615/03 53 Analysis Shows Minimal Displacement During Welding PIRTY 17 D.. D2
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Conclusion Coldworking is not a significant contributing factor 6/5/03 55 Axial Scan of Penetration 46 with Flaws Overlayed 8.11 Z(in) 15.62 615/03 56 6/5/03 56 28
Most Likely Causes
- Residual fabrication stresses
- J-groove weld grinding, welding, welding rework
- Weld cracking; fabrication defects / contaminants
- Combination of one or more with PWSCC 615103 57 Root Cause Focus I
I
- cwdknO, 615/03 58 29
Planned Additional Testing
- Volumetric UT of vessel around #1 and #46
- Visually examine inside bore #1 and #46
- Perform after nozzle capped and separated
- Possibly detect irregularities
- Look for known through-wall flaw in #1 615103 59 Planned Additional Testing (cont'd)
- Eddy current profilometry of #1 and #46
- Performed from the bottom after nozzle is capped and separated from guide tube
- Captures data on ID characteristics like ovalization at J-groove weld zone
- Visual exam of vessel at #1 and #46 after portion of old nozzle removed 615103 60 30
II Planned Additional Testing (cont'd)
- Metallurgical analyses of removed nozzle ends
- Boat samples from #1-and #46 flaw zones 6/5103 61 Repair and Startup Are Safe
- Inspections limit repair scope to the two leaking nozzles
- Extensive NDE reveals no flaws in other nozzles 615/03 62 31
Repair and Startup Are Safe (cont'd)
- Regardless of final root cause, half-nozzle repair is the appropriate corrective action
- Bounds potential causes
- Establishes new ASME Code pressure boundary
- Utilizes proven industry process
- Upgrades material to Alloy 690 6/5103 63 Repair and Startup Are Safe (cont'd)
- Evaluation of evidence indicates minor nozzle leakage is worst potential consequence 6/503 64 32
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Severe Consequences Not Likely Small Break Loss of Coolant Accident (SBLOCA)
- Residual stresses favor axial crack orientation
- No circumferential cracks 6/5103 65 Flaw Locations and Stresses TV d
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6/5)03 VM& Airm.
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Severe Consequences Not Likely (cont'd)
Small Break Loss of Coolant Accident (SBLOCA)
- Residual stresses favor axial crack orientation No circumferential cracks
- Robust design
- Limiting flaw size 615/03 67 Limiting Flaw Size 6/
10 }8 34
Severe Consequences Not Likely (cont'd)
Small Break Loss of Coolant Accident (SBLOCA)
- Residual stresses favor axial crack orientation
- No circumferential cracks
- Robust design
- Limiting flaw size
- Very large safety factor
- Bare metal inspection
- Leak before break 6/5)03 69 Severe Consequences Not Likely (cont'd)
No evidence of vessel wastage
- No significant iron in residue
- No wastage residue
- No visual indication
- Confirmed by UT 615J03 70 35
Severe Consequences Not Likely (cont'd)
Loose Parts
- No flaws above weld
- No circumferential flaw
- Residual stresses favor axial crack orientation 6/5/03 71 Conclusions
- We have good data
- Repair scope limited to #1 and #46
- Repair bounds likely causes
- Root cause will determine monitoring plan 6/5/03 72 36
REPAIR PLAN Steve Thomas Manager, Plant Design
@5103 73 Half-Nozzle Repair 6503 74 37
Deploy Plug; Cut Guide Tube / Nozzle STEP 1 6/5/03 AsqE YHR.SLE O.,e tUBE 7!5 Inspect for Leaks 615/03 STEP 2 INSPECT FOR LEAKS 76 38
Cut Nozzle Flush with Head mm OR FM STEP 3 6/5/03 ON E
77 K MD FMK 77 Form Weld Pad and NDE TOOuNG r PLIVOR 6/103 STEP 4 WELD PAD.
78 39
Machine Bore and Form Weld Prep STEP 5 615103 iCRR eOn7 FORM WEmD PREP 79 Install Nozzle; Weld; NDE WLD m UP STEP 6/5103
.SI0 80 40
Install Tube; Weld; NDE; Remove Plug STEP 7 Nll tall:E GOt IOC 615103 By 81 Analyses Supporting Repair Residual Stress &
Urniting Flaw Analysis Crack groth analysis to assure integrlty d shell Corrosion analysis ASME Stress Analysis ASME Fatigue Analysis ASME Design and Analysis is consistent with the original reactor vessel requirements 82 6/5/03 41
CORROSION ASSESSMENT Rick Gangluff Manager, Chemistry 615103 83 Half-Nozzle Replacement Corrosion Assessment
- Small gap between Alloy 600 remnant and new Alloy 690 nozzle
- No mechanism to concentrate boric acid
- Corrosion rates are very low (1.5 mil/yr) 615/03 84 42
Corrosion Rates Addressed by CEOG for Nozzle Replacement
- NRC found CEOG report methods and analyses to be acceptable
- STP plant-specific analyses in accordance with SER nearing completion 6/5103 85 BMI General Corrosion Acceptable
- Corrosion rate identified in report acceptable for STP based on projected capacity factors
- Lifetime increase in diameter
- 24 years 0.073"
-44 years 0.135"
- Less than most limiting nozzle 6/5103 86 43
CONCLUDING REMARKS Mark McBurnett Manager, Quality & Licensing 6/5103 87 Deliverables Nozzle finite element stress analysis Avail.
Flaw size limits to prevent net section collapse Avail.
NRC site review visit TBD Submit LER 6-12 NDE inspection report 6-14 Design change (Section 1i1,Section XI, corrosion) 6-14 Annulus dilation analysis 6-15 Submit temper bead relief request 6-17 Nozzle inservice acceptability analysis 6-30 615/03 88 44
- 3 Deliverables (cont'd)
Preliminary cause report (FMEA summary, bounding cause, safety significance, corrective action, monitoring plan) 7-12 Rockville meeting (cause report)
Public meeting at STP Relief request approval Half-nozzle lab analysis report 9-21 Boat sample analysis report 9-21 Submit LER supplement (final cause report summary) 10-12 615103 89 Conclusions
- NDE campaign successful
- Condition/repair scope known
- Repairs enable safe return to operation
- Continued close cooperation with industry and NRC on cause analysis 615103 90 45