recommendations for using current sentinel location ... · screening and assessment methodologies...
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2016 © Idom Nuclear Services
Recommendations for Using Current Sentinel Location Screening and Assessment Methodologies for License
Renewal Environmental Fatigue Calculations Tiberio García
Iñaki Gorrochategui Ainara Mira
(IDOM) Marta Álvaro
(Tecnatom)
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• Introduction
• Objective
• Identification of sentinel locations
• Assessment of sentinel locations
• Conclusions
Table of contents
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Introduction Long Term Operation (LTO)
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Long Term Operation
Operation beyond an established time frame defined by, for example, licence term, design, standards, licence and/or regulations (TYPICALLY 30-40 YEARS)
CONTINUE OPERATING UP TO 60 YEARS
INCREASE THE PROFITABILITY OF THE INVESTMENTS
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Introduction Time Limited Ageing Analyses
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SAFE LONG TERM OPERATION
SAFETY ANALYSES
Basic feature of any design
Use assumed time limits
TIME LIMITED AGING ANALYSIS (TLAA)
6 conditions
METAL FATIGUE IS A TLAA
NEEDS TO BE REEVALUATED
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Introduction LTO in Spain
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SPAIN
EEUU
Instruction IS-22
Regulation 10 CFR 54
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Introduction Metal fatigue TLAA: Environmental Assisted Fatigue (EAF)
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NUREG 1800 Rev. 2
Environmental fatigue in Class 1 pressure boundary components is considered a TLAA
As minimum, critical location selected in NUREG/CR-6260
Should be considered additional component locations
SENTINEL LOCATIONS Indicator of the damage accumulated by the EAF effect
LICENSE RENEWAL
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Introduction Metal fatigue TLAA: Environmental Assisted Fatigue (EAF)
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EAF TLAA TWO STEPS
1º SCREENING SENTINEL LOCATIONS
EPRI TR-1024995 METHODOLOGY
2º ASSESSMENT TO JUSTIFY THAT CUF VALUE CONSIDERING
ENVIRONMENTAL EFFECT MEETS ASME REQUIREMENT
CUF = �niNi
< 1m
i=1
THE EFFECT OF THE ENVIRONMENT is taken into account according to:
CUFen = Fen · CUF Fen
SULFUR CONTENT
TEMPERATURE
DISSOLVED OXYGEN
STRAIN RATE
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Introduction Fen formulation
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NUREG 1800 REV. 2 LETS TO USE THE FOLLOWING SET OF FEN FORMULATION:
CARBON STEEL AND LOW ALLOY STEEL
Fen from NUREG/CR-6583 combined with S-N curves from ASME Section III Code.
Fen from NUREG/CR-6909 Appendix A combined with S-N curves from ASME Section III Code or the ones from NUREG/CR-6909.
AUSTENITIC STAINLESS STEEL
Fen from NUREG/CR-5704 combined with S-N curves from ASME Section III Code.
Fen from NUREG/CR-6909 Appendix A combined with S-N curves from this reference.
NICKEL BASED ALLOY
Fen from NUREG/CR-6909 Appendix A combined with S-N curves from this reference.
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Objective MAIN ISSUES AND OBJECTIVE
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MAIN ISSUES
FATIGUE ANALYSIS OF CURRENT NPPs
WERE DONE SOME DECADES AGO
HAVE BEEN REVIEWED SEVERAL TIMES
ACCURACY OF AVAILABLE INFORMATION
CANNOT BE ENOUGH
OBJECTIVE
TO PROVIDE SOME RECOMMENDATIONS THAT SOLVE POSSIBLE ISSUES
THAT COULD BE FOUND IN THE RESOLUTION OF EAF TLAA
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Identification of sentinel locations EPRI methodology
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NPP have a different level of detail in their calculations, especially depending on its age.
NPP may have performed modifications during its operating life – Replacement of Steam Generators, Replacement of RPV Head, Uprating, etc
Re-evaluate the stress reports, either in all calculated locations or only in the most limiting ones.
GENERAL APPLICATION
The recommended procedure for identification of sentinel locations applicable to the USA design plants is described in EPRI TR-1024995.
HOWEVER
How to use the general EPRI procedure to REAL SITUATIONS RECOMMENDATIONS
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Identification of sentinel locations ASME vs. NUREG 6909
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1/6 For the selection of sentinel locations NUREG-1800 Rev. 2 offers the possibility of using either NUREG-6583 (CS and LAS) and NUREG-5704 (SS) in combination with original ASME S-N curves, or NUREG-6909.
NUREG 6909 Requires to re-evaluate CUF values according to its own S-N curves
IN MANY CASES, CUF VALUE IS ONLY AVAILABE
IT CANNOT BE RE-EVALUATED
USING NUREG-6583 (CS AND LAS) AND NUREG-5704 (SS) WITH ASME S-N CURVES
IS APPROPIATE FOR THE SCREENING
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If all stress ranges (Salt i) and number of cycles (ni) ARE KNOW
Identification of sentinel locations Nickel based alloys NUREG-6909 re-evaluation
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2/6 FOR NICKEL ALLOYS, ONLY NUREG-6909 CAN BE USED
RE-EVALUATION OF CUF ACCORDING TO NUREG-6909 IS INMEDIATE
CONSERVATIVE ESTIMATION
If all stress ranges (Salt i) and number of cycles (ni) ARE NOT KNOW
𝐂𝐔𝐔𝟔𝟔𝟔𝟔 = 𝟏𝟔 · 𝐂𝐔𝐔𝐎𝐎𝐎𝐎𝐎𝐎𝐎𝐎
SOME CONSIDERATIONS SHALL BE INCLUDED IN THE SCREENING PROCESS
NOTE:
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It can be continued with the screening process
Identification of sentinel locations Common Basis Model
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3/6 EPRI: VERIFICATION OF COMMON BASIS MODEL
AFIRMATIVE
COMMON BASIS STRESS EVALUATION PROCEDURE
To compute an estimated CUF
NEGATIVE
Some limitations for its use
ALTERNATIVE BASED ON KUPPER AND GRAY METHODOLOGY
If all loc. of the system/equipment have been calculated with the
same level of conservatism
If not, loc. with the same type of fatigue calculation must be classified in different groups
TYPES OF FATIGUE CALCULATIONS C.T. Kupper and M.A. Gray, “License Renewal Environmental Fatigue
Screening Application”, PVP 2014-29093. Proceedings of the ASME 2014 Pressure Vessels & Piping Conference. 2014.
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In some combination of thermal zone/material CUF IS NOT CALCULATED at any location in contact with the coolant environment
Identification of sentinel locations Conservative CUF estimation
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4/6
If additionally, CBSEP IS NOT APLICABLE
It is strictly valid for cylindrical and plate
components
It can be evaluated to ASSIGN
CUF 𝑖𝑖 𝑐𝑐𝑖𝑐𝑐𝑐𝑐 𝑒𝑖𝑒𝑖𝑒𝑐𝑖𝑒𝑒𝑖𝑐
CUF𝑤𝑖𝑐𝑤𝑐𝑤𝑐 𝑐𝑐𝑖𝑐𝑐𝑐𝑐𝑒𝑖𝑒𝑖𝑒𝑐𝑖𝑒𝑒𝑖𝑐
If it can be verified that CUF of location that is not in contact with environment is higher
than the rest of locations of thermal zone/material
CUF available Highest CUF value Not in contact with
environment
CUF not available In contact with
environment
NOTE: SOME CONSIDERATIONS SHALL BE INCLUDED IN THE SCREENING PROCESS
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If the CUF has been calculated with NUREG-6909 S-N curve the EPRI criteria can be used.
If the CUF has been calculated multiplying by ten original CUF only the following criteria apply: If in one thermal zone there is one or more nickel based alloy candidate
sentinel location, all of them will directly promote to initial sentinel location.
Only can be applied the technique that establishes that if the sentinel location shows a conservative CUFen value for 40 years lower than 0.8 it could be excluded from the final list of sentinel locations.
Identification of sentinel locations Sentinel locations screening
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5/6 SOME LIMITATIONS SHOULD BE INCLUDED IN “Ranking and sentinel location identification for each material and thermal zone” and “Guidelines for reducing the number of sentinel locations” of EPRI document
DUE TO THESE RECOMMENDATIONS
FOR NICKEL BASED ALLOY LOCATIONS 1
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All of them will directly promote to initial sentinel location. Only can be applied the technique that establishes that if the sentinel location
shows a conservative CUFen value for 40 years lower than 0.8 it could be excluded from the final list of sentinel locations.
Identification of sentinel locations Sentinel locations screening
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5/6 SOME LIMITATIONS SHOULD BE INCLUDED IN “Ranking and sentinel location identification for each material and thermal zone” and “Guidelines for reducing the number of sentinel locations” of EPRI document
DUE TO THESE RECOMMENDATIONS
Locations where the CUF value represents to other ones that are not in contact with the coolant environment
2
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Identification of sentinel locations Component replacement
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6/6 FOR SYSTEMS OR COMPONENTS INSTALLED AFTER THE INITIAL OPERATION OF THE NPP
The following constraints must be introduced in the application of the criteria defined in section “Guidelines for reducing the number of sentinel
locations” of document EPRI TR-1024995
- One sentinel location of a component installed from the start of plant operation CAN COVER one initial sentinel location of other component installed later if the criteria of “Guidelines for reducing the number of sentinel locations” of document EPRI TR-1024995 are accomplished.
VESSEL BODY SENTINEL LOCATION CUFEN= 2.3
VESSEL HEAD WAS CHANGED
VESSEL HEAD SENTINEL LOCATION CUFEN= 1.2
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- One initial sentinel location of a component installed later than the start of plant operation CANNOT COVER one initial sentinel location of other component installed at the beginning of plant operation even if the criteria of “Guidelines for reducing the number of sentinel locations” of document EPRI TR-1024995 are accomplished.
Identification of sentinel locations Component replacement
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6/6 FOR SYSTEMS OR COMPONENTS INSTALLED AFTER THE INITIAL OPERATION OF THE NPP
The following constraints must be introduced in the application of the criteria defined in section “Guidelines for reducing the number of sentinel
locations” of document EPRI TR-1024995
VESSEL HEAD SENTINEL LOCATION CUFEN= 2.3
VESSEL HEAD WAS CHANGED
VESSEL BODY SENTINEL LOCATION CUFEN= 1.2
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Assessment of sentinel locations
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ASME vs. NUREG 6909
FOR ASSESSMET PHASE, IT IS PROPOSED NUREG-6909
THREE MAIN REASONS:
Final sentinel locations that result from the screening process usually correspond to locations whose fatigue calculations are detailed in the stress reports, hence, the CUF value can be re-evaluated according to NUREG/CR-6909.
Nickel based alloys are only addressed in NUREG/CR-6909, this document must necessarily be employed for these materials. In order the calculations for all materials (CS, LAS and SS) be consistent it is more appropriate to use the same formulation for all of them.
To be consistent with the position of the NRC about how to consider the effects of the environment in the fatigue design of new reactors.
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Accurate methods to calculate Fen, as integrated method, are difficult
to be used
IN MANY CASES, ESPECIALLY IN OLD PLANTS, THIS
INFORMATION IS NO AVAILABLE
Assessment of sentinel locations Fen calculation
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Depending on the conservatism needed for the assessment of the sentinel locations an increasing degree of accuracy can be necessary in the estimation of the parameters contributing in the calculation of the Fen factor.
START CONSERVATIVE AND SIMPLE APPROACH
Enveloping values of all parameters: temperature, dissolved oxygen, sulphur content and strain rate
IF HIGHER ACCURACY IS NEEDED
Then plant specific values should be used
ALTERNATIVES
RECALCULATION FEM
MONITORING SBF
FLAW TOLERANCE METHOD
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Conclusions Recommendation
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SOME RECOMMENDATIONS ARE PROVIDED TO SOLVED SOME ISSUES THAT COULD BE
FOUNDED IN THE RESOLUTION OF EAF TLAA
These recommendations must be taken into account as what they are, that is, only recommendations,
which come from the experience acquired