ML12171A524
| ML12171A524 | |
| Person / Time | |
|---|---|
| Site: | Indian Point  |
| Issue date: | 07/11/2003 |
| From: | Westinghouse |
| To: | Atomic Safety and Licensing Board Panel |
| SECY RAS | |
| Shared Package | |
| ML12171A508 | List: |
| References | |
| RAS 22624, 50-247-LR, 50-286-LR, ASLBP 07-858-03-LR-BD01 | |
| Download: ML12171A524 (18) | |
Text
NYS000382 Submitted: June 19, 2012 AP1000 AP1 000 Draft Safety Evaluation Report lBB Open Items Presentation to NRC Staff Rockville, MD July 11, 2003 Westinghouse AP1000 AP1 000 Draft Safety Evaluation Report
- Two DSER Open Items Related to LBB
- 3.6.3.4 PWSCC
- 3.6.3.4 TGSCC
- PWSCC Open Item
- Requests W to include Combined Operating License applicant commitment to implement inspection plans, evaluation criteria, and other types of measures imposed on or adopted by operating PWRs with currently approved leak-before-break (LBB) applications as part of the resolution of concerns regarding the potential for PWSCC in those units
- Westinghouse has incorporated the COL item in the AP1000 DCD 8 BNFL Shdc 2 Westinghouse
~1ooci APl 000 Draft Safety Evaluation Report
- TGSCC Open Item
- Identifies TGSCC as a possible failure mechanism for AP1 000 piping systems
- If TGSCC crack morphology parameters are assumed, LBB bounding curves would be impacted, and it will be more difficult to demonstrate that AP1000 piping systems meet LBB
- Requests W to perform piping stress analysis and perform sensitivity analysis for 5 piping systems to demonstrate that AP1 000 piping systems can meet LBB GBNFL Shdc)
Westinghouse AP1000 W Position on TGSCC Open Item
- W does not agree that TGSCC is a possible degradation mechanism for AP1000 piping systems
- AP1 000 Bounding Analysis Curves as currently constructed are appropriate
- Fundamental requirement for LBB application is that stress corrosion cracking does not exist
- VC Summer experience with PWSCC does not apply to AP1000
- Assuming TGSCC crack morphology parameters as a surrogate for PWSCC is not consistent with LBB approach
- Therefore Wwill provide information to demonstrate that PWSCC and TGSCC do not apply to AP1 000 LBB piping systems 8BNFL s~oc1c
- Westinghouse 2
Alloy 690, Alloy 52, Alloy 152 in APl 000
- In view of the continuing occurrence of primary water stress corrosion cracking [PWSCC] of Alloy 600, and its associated welds Alloys 82 and 182, the decision was taken to preclude use of these materials in the AP1 000 design
- The materials selected for these applications are Alloys 690, 52 and 152, respectively
- The recent cracking experiences in Alloy 600 and associated welds in operating PWRs therefore have no relevance to the AP1000 Slide~
I/4.P1000 Alloy 690- Historical Perspective
- Thermally treated Alloy 690 [A690 TT] was adopted as the preferred alloy for SG heat transfer tubing applications in 1986
- A690 TT also began service as mechanical SG tube plugs at approximately the same time
- Since the initial replacement SG startup at D.C. Cook Unit 2 in May 1989, A690 TT is now in service at more than fifty PWRs worldwide
- Applications of A690 TT have since been extended to include SG divider plates, pressurizer heater sleeve penetrations, RV head penetrations (including CRDM pipes), and other small-bore instrument penetrations Slide!\
Westinghouse 3
.AP1000 Alloy 690 - Experience (Cont'd.)
- Several of the CE-repaired components, with A690 TT as the replacement material, have been in service since approximately 1989
- With over fourteen years of SG operating experience, at temperatures exceeding 328°C [622.4°F], and nearly sixteen years in pressurizer penetration applications at 343°C [650°F] there has not been a single incidence of environmental degradation of A690 TT Shde7 Westinghouse AP1000 Alloys 52 and 152
- With the extension of A690 TT applications to SG divider plates, RV and pressurizer penetrations, and other applications requiring welding, the A690 weld metal analogs Alloys 52 and 152 have been widely deployed
- Alloy 52 is used for gas-tungsten-arc [GTA] or gas-metal-arc [GMA]
welding; Alloy 152 is the stick electrode composition used for shielded metal-arc welding [SMAW]
- Alloys 52 and 152 contain the same nominal concentrations of Cr and Fe, with slightly less Ni - relative to Alloy 690 Shdc:X Westinghouse 4
A52 and A 152- Applications in PWRs
- The earliest application of these weld metal alloys was in CE pressurizers in which partial penetration welds were used to complete the repairs; these applications extend as far back as early 1989
- Westinghouse replacement SGs at N. Anna 1 and V. C. Summer were the first units to employ large-scale use of A52 and A152
- These SG applications included safe end-to-nozzle welds, and welding of the divider plate and stub runner to the channel head
- The initial SG applications went into service in late 1993, accruing nearly ten years of service since that time Slide9 Westilghouse
.AP1ooo Alloy 52 & Alloy 152- SCC Resistance
- Owing primarily to high Cr content, Alloys 690, 52, and 152 exhibit apparent immunity to primary water stress corrosion cracking (PWSCC)
- Service experience with Alloy 690 in SG heat transfer tubing applications, and Alloys 52/152 as buttering, cladding and weld filler materials has been exemplary, with no reported degradation
- Laboratory testing of each of these materials endorse the exceptional corrosion resistance - no known incidence of crack initiation or crack propagation in primary water environments in any of these materials Slide 10 WeSfinghouse 5
AP1000 Alloys 52 & 152 - SCC Resistance (Cont'd.)
- The laboratory tests of these weld metals continues to support the concept of "immunity" to PWSCC
- Even specimens precracked in fatigue will not propagate; details of these tests have been provided in the Revision 1 response to RAI 251.004
- Alloys 52 & 152 have been used in operating PWRs for RV nozzle repairs at V.C. Summer and Ringhals 3 & 4
- The use of Alloy 52 for an embedded flaw weld repair of CRDM pipe degradation at N. Anna Unit 1 was approved in late 1992, and generically approved in July 2003.
SINk 11 AP1000 Alloys 52 & 152- Conclusions
- There is no technical basis to judge that Alloy 52 & Alloy 152 will not preclude the occurrence of environmental degradation in PWR primary water environments Slide 12 Westinghouse 6
~1000 TGSCC Issues
- PWR experience with austenitic stainless steel has been excellent
- After more than 3000 reactor years of service, no TGSCC has occurred in piping
- TGSCC has occurred in other geometries, and these will be reviewed briefly
- The key requirements for TGSCC are high stress, high Oxygen content, and impurities such as Chlorides
- AP1000 builds on this extensive successful experience Sitek 1:\
Westinghouse AP1000 TGSCC Cracking Experience
- Palisades CEDM housings
- Summer 2001 was the most recent occurrence
- Earlier, CEDM seal housings had shown cracking
- These housings have a large volume of stagnant water, not vented
- Canopy Seal Weld Region Cracks- Numerous Occurrences
- EdF Auxiliary Unes, Drain Unes ( stagnant, High 0 2 , with chlorides)
- Common Theme - High Residual Stresses, Stagnant or Semi-Stagnant Flow Conditions, High Oxygen, Some Level of Cl fiBNFl Shdc I~
Westinghouse 7
How does APlOOO Ensure that TGSCC does not Occur?
- Dissolved Oxygen levels are kept to near zero, by a hydrogen overpressure, which scavenges all oxygen out of the water
- Chlorides are kept to extremely low levels by careful chemistry control at all times
- These controls, on both oxygen and Chlorides, have been used in the commercial PWR business since its beginning over thirty years ago, with great success
- Controlling to these low levels ensures that TGSCC cannot occur, as seen in the next slide Slide I~
Westinghouse Dissolved Oxygen and Chlorides that may lead to SCC A.P1ooo in Stainless Steel 1000 rTr:::~::-:--:::::r-:--::""""....,..,..,"?=~~~:=i'l sec- all heot tr.otmonts 304 so:
cmeolecl
- sersitizecl
- 0 0
rento!Ne o.or SCC-sofe area 0
10 100 1000 10000 CHLORIDE CONCENTRATION, ppm Slide 16 Westinghouse 8
Open Item 3.6.3.4-1 [PWSCC] -Conclusions
- Alloys 52 and 152 have been shown to exhibit excellent resistance to PWSCC, both in lab and field experience
- However, Westinghouse recognizes the reservations expressed by the NRC with respect to the limited [ca. 9.5 years] field experience
- Continued field experience - and laboratory evaluations currently underway- will accrue prior to final operation of AP1000
- Westinghouse remains confident this experience will validate the decision to extensively deploy these materials in the AP1000 primary system Slide 17 Westilghouse AP1000 Open Item 3.6.3.4-2 [TGSCC] -Conclusions
- TGSCC is a well known cracking mechanism in austenitic stainless steels
- However, as the direct consequence of the design and operation of the AP1 000 primary system, the environmental conditions necessary for its occurrence ( high 0 2 , chlorides) will not exist
- Therefore, it is concluded that there is no phenomenological basis to conclude that TGSCC will represent a failure mechanism in the AP1000 LBB piping systems- and leak-before-break is applicable Slide IR Westinghouse 9
~1ood APl 000 Piping Systems Designed for LBif
- AP1 000 LB8 Piping Systems are the same as those designed for AP600
- Some line sizes increased
- Line routings the same
- Stress analyses completed for AP600 demonstrate the feasibility that the AP1000 piping systems can be designed to meet bounding analysis curves
- AP1 000 LB8 Piping System isometric /layout drawings were reviewed by NRC in September 2002 Slide 19 Westinghouse l:\P1000 APl 000 Piping Systems Designed for LBB
- Reactor Coolant Loop
- Pressurizer Surge Line
- Direct Vessel Injection Lines A & 8
- Core Makeup Tank Inlet Lines A & 8
- ADS-1/2/3 Piping
- ADS-4 Piping A & B
- Normal RHR Piping
- Main Steam Lines A & B 8BNFL Slick 21l 10
Comparison of IRWST lnjection/DVI line TO '-UCTOA YUSH,.,
DVIA-AP600 DVIA-1000 Slide 21 Westinghouse
~1000 AP1 000 Piping Analysis Methodology
- AP1000 Piping Design Criteria Document (APP-GW-P1-001)
- Defines Mandatory Analysis Requirements for AP1 000 Piping Systems
- Applicable Loadings and Loading Combinations
- Methods of Analysis
- Acceptance Criteria
- Consistent with AP1000 DCD Sections 3.7 and 3.9
- Criteria Reviewed by NRC Staff at Westinghouse Office in September 2002 8BNFL ShdcU Westinghouse 11
AP1 000 Piping Analysis Methodology "---*--
(Continued)
- Pipe Rupture Protection Design Criteria Document (APP-GW-N1-001)
- Defines Mandatory Requirements for AP1 000 Pipe Rupture Protection
- Leak-Before-Break Bounding Analysis Methods
- Bounding Analysis Curve Margins
- Margin of 10 on leak detection capability
- Margin of 2 on flaw size
- Margin of 1 on load by using absolute summation method of maximum loads combination
- Consistent with AP1000 DCD Appendix 3B
- Criteria Reviewed by NRC Staff at Westinghouse Office in September 2002 CIBNFL shdc 2.' Westinghouse AP1000 AP1 000 Preliminary Stress Analysis
- Piping stress analysis for AP1000 candidate system in-progress
- DVI-A Piping Analysis Package
- Selected based on our experience with AP600
- Difficult to qualify
- Complicated piping system
- Some piping sizes were changed
- Contains smallest piping line qualified for LBB
- Subcompartment pressurization impacts if line would not meet LBB criteria CIBNFL Slidc14 westinghouse 12
.M~1ood t"<"*---
Preliminary Results Flgu" 1 1 t Af'1ooo Bounding Anatnla Cym for r CMJ. QY!.IRWST (Uno Numbers: l015A.01&A.t11A,020A,0%1Mio 1Mui.,02$A.1Z5A,127A)
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0 10000 15000 25000 NorJMIItr.*** .,II)
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Westinghouse AP1000 Preliminary Results Bau!! U.2 AptOOO Bounding Analnla Curyt lor r DVJ Cold TAR toRY (Lint llunlbttr: LOZ1A-Insul.)
10000~--~~----~--~~~--~--+-~----~"--~~~
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11000 tOOOO 15000 ~ 21000 Normoi--P'IIl 8BNFL Shdc 2fl Westinghouse 13
Preliminary Results F!s!m I.U AP1099 Bounding Ana!nl! Cum lor RHS D!Jchamt (Line Number:L011AI
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10000t---+-~ --------------------1 0 5000 10000 15000 20000 2$000 30000 Nonnai-IP81J Slide 27 Westinghouse AP1000 Preliminary Results F!gurt 8.1.4 AP1000 Boundlna Analyaft Curve for AccumuiJtor '"" laolatlon Yatvt CLint Number : L027 AI eoooo.o . - . - - - - - - - - - - - - . . . . . - - - - - - - - - - - . , . - - - ,
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~1000 Preliminary Results figure 1.1.1 AP100Q Boundlna Anatxale Cum for r Accumulator eo ftolatfqn Yatve IUne Number : L028A) 50000 l-----:---,--'--
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0 5000 Sltdcl9 Westinghouse AP1000 APl 000 Use of Design Acceptance Criteria BACKGROUND
- Westinghouse introduced AP1 000 at a meeting with NRC in April 2000
- Identified the need for Westinghouse to use Design Acceptance Criteria (DAC) in lieu of detailed piping design and analysis
- Basis:
- Previous certified designs used Piping DAC
- NRC can make safety determination without detailed piping design during Design Certification
- Piping design and analysis can be deferred to COL applicant
- Final piping design and analysis verified during ITAAC Shdc .111 Westinghouse 15
Four Main Issues Addressed in Pre-Certification Review
- Applicability of AP600 Test Program to AP1000
- Applicability of AP600 Safety Analysis Codes to AP1000
- Defer Detailed Engineering using Design Acceptance Criteria
- Applicability of AP600 Exemptions to 10CFR50 Shde 31 Westinghouse AP1000 APl 000 Pre-Certification Review
- WCAP-15614, "AP1000 Seismic and Structural Design Activities"
- Report submitted to NRC in 1/2001 outlines proposed DAC approach
- Piping design
- Structural design
- Included preliminary seismic analysis results
- NRC staff raised issues with our approach
- Westinghouse agreed to revise DAC approach for AP1 000
- Drop DAC approach for seismic I structural
- Use DAC approach for piping Slide Jl Westinghouse 16
APl 000 Pre-Certification Review #I&P1000 Conclusions
- Use of DAC Acceptable for AP1000 piping
- The use of CAC wm not affect the staffs ability to make necessary safety determination
- Contingent on ability to agree to an adequate piping CAC
- Some reliance on similarities of AP600 and AP1 000
- Identified LBB as an issue to be resolved
- Piping CAC could have been approved without reliance on similarities to AP600
- Degree of design detail at CC stage is a business decision br the applicant, provided safety determination can be made Shdc ll Westinghouse AP1000 Westinghouse Position on LBB Issues
- AP1000 materials not susceptible to sec
- COL Item incorporated to address resolution of industry issue for LBB
- Significant additional operating experience with AP1000 materials will be realized prior to first AP1000 is deployed
- BAC provided In DCD contain recommended LBB margins and are valid for AP1000 Slide 14 Westinghouse 17
Westinghouse Position on lBB Issues AP'1~
-~: ......
(Continued)
- SECY-02-0059 Approved DAC Approach for Piping
- Design Acceptance Criteria in lieu of detailed piping design and analysis
- W approach specifies that piping stress analysis be completed as part of COL application
- AP600 piping stress analyses can be used to demonstrate feasibility for AP1 000
- AP1000 piping stress analysis for DVI-A further demonstrates feasibility
- No additional piping analysis required Slide:\~
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