ML101380215
| ML101380215 | |
| Person / Time | |
|---|---|
| Site: | Palo Verde  |
| Issue date: | 04/01/2010 |
| From: | Arizona Public Service Co |
| To: | Division of License Renewal |
| Regner L M, NRR/DLR, 415-1906 | |
| References | |
| TAC ME0254, TAC ME0255, TAC ME0256 | |
| Download: ML101380215 (30) | |
Text
PVNGS License Renewal Application Metal Fatigue Topics April 1, 2010
Discussion Topics
- Historical and general background
- Metal Fatigue Monitoring Program
- Cycle Counting Questions
- Class 1 Fatigue TLAA Evaluation Process
- Future actions
- NRC staff questions
Historical and general background
Initial development of PVNGS metal fatigue monitoring program
- Program required by PVNGS Technical Specification 5.5.5
- SYS80-PE-DE Compilation of NSSS Responses to Design Bases Dynamic Events for the System 80 Standard Design established applicable design cycles and their 40-year expected accumulation
- Class I metal fatigue analyses incorporated the SYS80-PE-DE limits and in some cases identified additional items of concern
Initial development of PVNGS metal fatigue monitoring program
- The initial Technical Specification program did not require all UFSAR transients to be monitored
- The UFSAR does not incorporate all of the additional limits (e.g. RCP stud tensioning/de-tensioning) - to be discussed later in this presentation
- PV staff identified that not all UFSAR transients were being counted
- Implemented expanded list of transients in January 1996
- ITS upgrade in 1998 established current requirements
- Not counted data between 85 and 95 was assumed to be an accumulation of 25% of the design allowed transients in all but a few cases Program Review - 1995
- Actual event counting has been in place since January 1996
- Unit 1, 2 and 3 records have now been reviewed for LRA support Performance of cycle counting since January 1996
Metal Fatigue Monitoring Program
- Current methodology:
- Cycle counting to ensure design assumptions are not exceeded
- Specific component locations are not specified
- Exception: Partial cycle (CBF-PC) methodology is used to track spray nozzle usage Current PVNGS Metal Fatigue Monitoring Program
- Recounts of all three units were reported in the response to RAI B3.1-4 (see RAI response Table 3.1-4)
- Recount Methodology
- Validated assumptions Addressing Cycle Count Assumptions
- Recount Methodology
- Best source selected (logs, MORs, LERs, WOs, interviews)
- Reviewed assumption of 25% accumulated cycles
- Actual data
- Comparison to 95 - 05 operating history Cycle Recount
Required by 10 CFR54.21 (c)(1)(iii)
Scope - All Class I components Methodology:
- Based on component locations
- Adds SBF for high usage locations (not discussed in this presentation)
- Continues cycle counting for Global monitoring
- Used for low 40-year design CUF
- No new industry issues since original design
- Industry experience indicates not a problem location
- Expands CUF monitoring
- CBF-C (CUF based on design cycle)
- CBF-PC (CUF based on partial cycle)
- CBF-EP (CUF based on event pairing)
- Establishes appropriate action limits and corrective actions Enhanced Metal Fatigue Monitoring Program
- SBF methodology (to be determined)
- FatiguePro is under evaluation for cycle counting and CBF monitoring
- Current manual cycle counting will continue until a suitable software program has been validated
- Enhanced program will be implemented no later than two years prior to the PEO (LRA commitment #39 as revised in Amendment 9)
Enhanced Program Status
Cycle Counting NRC Questions
Cycle Counting RAIs and Amendments
- Amendment 3 (annual update)
- Added Unit 3 record review results and revised one transient total to replace an estimate with data
- Revised current program action limit discussion to avoid confusion with the enhanced program limits
- Minor clarifications were included in the AMP OE discussion
Cycle Counting RAIs and Amendments (continued)
- Amendment 9 (result of RAI B3.1-1 thru 8)
- RAI B3.1-4 response provided the individual unit cycle totals from best available sources
- Corrected typographical errors
- Included enhanced monitoring implementation schedule
- Committed to selection of a suitable SBF methodology
- Clarified cycle projection methodology
Cycle Counting RAIs and Amendments (continued)
Most recent cycle count related DRAI set (DRAI 4.3-1 thru 9
- DRAI 4.3-1 Transients projected to exceed 40-year limits
- Projections are conservative and may not be reached
- 10CFR54.21(c)(1)(iii) permits aging management for TLAAs that are not validated or projected for the PEO
- NUREG 1800 paragraph 4.3.3.1.1.3 permits the use of GALL programs for aging management
- NUREG 1801 Vol 2 AMP X.M1 allows use of this program to manage aging and recommends no further evaluation if this program is selected to satisfy 10CFR54.21(c)(1)(iii)
- PVNGS took no exceptions to X.M1 and concludes fatigue reanalyses are not required based on projections. Corrective action will be initiated if needed based on program action limits
Cycle Counting RAIs and Amendments (continued)
- Presented for information only
- Concept of a worst case bounding unit
- Conservative Assumptions
- Highest unit total was used for 85-95 and for 95-05
- Lowest operating years was used for accumulation rate
- 42 years were used for projecting and added to above
- Zero accumulation assumed to be linear times 22/40
- If not expected still assumed 1 event
Cycle Counting RAIs and Amendments (continued)
- DRAI 4.3-2 Global monitoring criteria does not seem consistent
- Exceptions are explained in LRA table notes
- DRAI 4.3-3 Clarify the CBF-PC method
- DRAI 4.3-4 Program action limits (see commitment #39)
- DRAI 4.3-5 Some cycles do not agree with the UFSAR
- Some are derived from UFSAR sections other than 3.9.1
- Some come from specific analyses (e.g. RCP studs)
- Addition of cycles to the UFSAR is under consideration
Cycle Counting RAIs and Amendments (continued)
- DRAI 4.3-6 25% cycle assumption
- Review of best source data was presented in the response to RAI B3.1-4
- Compared assumption to actual data from recount efforts or data from 95-05
- Result:
- Four assumptions of 25% cycle accumulation are being reviewed: Rx Trip, Load Reject, Turbine Trip w/o Rx Trip and Depressurization by MSSV at 100% power
- Remaining 25 % assumptions are conservative
Cycle Counting RAIs and Amendments (continued)
- DRAI 4.3-7 Not all cycles were recounted
- Some had accurate data and did not require recount
- Some were not significant (e.g. plant loading at 5%/min)
- Some could not be recovered so the 25%
assumption was used and validated from 95-05 data
Cycle Counting RAIs and Amendments (continued)
DRAI 4.3-8 Questioned an incorrect table note (had been corrected in Amendment 9)
DRAI 4.3-9 Some cycles are not included in the UFSAR (similar to DRAI 4.3-5)
- Some come from specific analyses (e.g. RCP studs)
- Addition of cycles to the UFSAR is under consideration
Class 1 Fatigue TLAA Evaluation Process - LRA Section 4.3.2
- Identify TLAAs and Affected Components
- SRP Guidance, Industry Experience, CLB Search
- Retrieve Component Current Licensing and Design Basis Documents (CLB and CDB)
- Evaluate and Summarize CDB TLAAs
- Analysis Results - Analyzed Locations, CUFs, etc.
- Effects of Modification, Analysis, and Op. History
- Effects of Differences in Analysis Methods
- Identify Disposition Class 1 Fatigue TLAA Evaluation Process
- SRP Guidance
- NUREG-1800 Sect. 4.3 and Tables for Class 1
- Based on ASME III Subsection NB and NG and Industry Experience
- Industry Experience - Examples:
- Other LRAs
- NRC and NSSS vendor Bulletins, Notices, etc.
- CLB Search
- Word Search of CLB (FSAR, Docketed Reports, Letters, etc.)
- Confirm applicability to Palo Verde
- Identify other plant-specific TLAAs Identify TLAAs and Affected Components
- Research and Summarize History of CLB
- Confirm Current Licensing Basis
- Research Design and Analysis History
- Confirm Current Design Basis
- TLAAs are analyses, are therefore part of the CDB
- TLAAs are usually bases of the CLB (incorporated by reference) rather than included verbatim Retrieve Component Current Licensing and Design Basis Documents (CLB and CDB)
- Analysis Results
- All TLAA Results (e.g., all reported fatigue summaries)
- All Analyzed Locations
- Tabulated for Complex Components
- Effects of Modification, Analysis, and Operating History - Examples:
- Instrument Nozzle Half-Nozzle and MNSA Repairs (Several LRA Sections)
- Pressurizer Surge Line Thermal Stratification (LRA Section 4.3.2.9)
- Unit 2 Head Vent Repair - high part-life CUF, head replaced Fall 2009 (LRA p. 4.3-34)
Evaluate and Summarize CDB TLAAs
- Identify Disposition
- Based on Analysis History, Results, and Methods
- 10 CFR 54.21(c)(1)(i) - If simple design life or cycle ratios, etc.,
confirm adequate margin at 60 years
- 10 CFR 54.21(c)(1)(iii) - Used in most other cases
- Requires Aging Management
- 10 CFR 54.21(c)(1)(ii) - Reanalysis performed Evaluate and Summarize CDB TLAAs (Continued)
- Identify Disposition (Continued)
- 10 CFR 54.21(c)(1)(iii) monitoring methods are described in LRA 4.3.1, summarized by monitored location in Table 4.3-4
- Details of 10 CFR 54.21(c)(1)(iii) monitoring methods are location and analysis-specific. Examples:
- Global - monitor transients
- Cycle-based fatigue (CBF) - monitor transients, possible CUF impacts
- Stress-based fatigue (SBF) - impact of transients require reevaluation of CUF Evaluate and Summarize CDB TLAAs (Continued)
NRC Staff Questions
- Have we answered the questions and issues stated in this presentation?
- Does the staff have additional questions with respect to cycle counting or the PVNGS approach to metal fatigue?
- Review action items
- Future topics Thank you for your participation