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EPRI Public Meeting Slides: Revisiting High Energy Line Break (HELB) Location Methodology
	ML24078A378
Person / Time
Site:	Electric Power Research Institute
Issue date:	03/18/2024
From:	Demetrius Murray; Licensing Processes Branch
To:	;
	Murry, D, NRR/DORL/LLPB
References
	EPRI TR 3002028939, EPRI TR 3002028939, Rev 0, EPRI TR 3002028939, Revision 0, Risk-Informed HELB Methodology, EPID L-2024-TOP-0003
	Download: ML24078A378 (1)
	v • d • e

w w w. e p r i. c o m March 18, 2024 Pre-Meeting for Pre-Application Meeting on RI-HELB Revisiting High Energy Line Break (HELB) Location Methodology

2 Agenda Introductions/Opening Remarks Background/Related Activities Discussion - RI-HELB Methodology Discussion - RI-HELB Topical Report Action Items/Closing Remarks

3

Introductions

EPRI has developed report # 3002028939 Risk-informed High Energy Line Break Evaluation Requirements Final draft available in the EPRI electronic reading room Intent of this pre-application meeting is to continue dialogue with NRC on this topic support submittal of 3002028939 as a Topical Report support future industry use of the methodology contained in 3002028939

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As a result of industry ongoing activities (e.g. power uprates, license renewal, subsequent license renewal), a number of deterministic requirements are being challenged as to their efficiency in maintaining and improving plant safety while providing flexibility in plant operations and resource allocation.

As an example, for a couple of operating sites, attempting a MUR uprate identified the potential for a system to be re-classified from a moderate energy system to a high energy system due to increases in the subject systems operating temperature and pressure after MUR

Having to meet current deterministic HELB requirements would entail significant plant reanalysis and substantial plant modification

Discussions with the New Build fleet have also identified these deterministic HELB requirements contributing to capital cost and engineering difficulties Background on Current Requirements for Identifying HELB Locations

5 GDC4 Environmental and dynamic effects design bases, states that structures, systems, and components important to safety shall be designed to accommodate the effects of postulated accidents. These structures, systems, and components shall be appropriately protected against dynamic effects, including the effects of missiles, pipe whipping, and discharging fluids, that may result from equipment failures.

Chapters 3.6.1 and 3.6.2 of NUREG-0800 (the SRP) provide deterministic requirements for designing against postulated piping failures. Examples of these requirements include differentiating between moderate and high energy system, identifying where to postulate the breaks (e.g., high design stress welds) and identifying the types of breaks (e.g., size and orientation) that need to be postulated as well as what the success state looks like.

For safety related systems, examples of required postulated break locations in high energy systems include:

Terminal ends,

Cumulative Usage Factor (CUF) 0.1

S > 2.25 Sm or S > 1.8Sy For non-safety related systems, required postulated break locations in high energy systems includes essentially everything.

5 Background on Current Requirements for Identifying HELB Locations

6 EPRI TR-112657, Rev B-A Revised Risk-Informed Inservice Inspection Evaluation Procedure, has been approved by USNRC as an acceptable alternative to deterministic ASME Section XI inservice inspection requirements.

EPRI 1006937-A Extension of the EPRI Risk-Informed Inservice Inspection (RI-ISI) Methodology to Break Exclusion Region (BER) Requirements, has been approved by USNRC as an acceptable alternative to deterministic NUREG-0800 BER inservice inspection requirements NRC Public Meetings - Alternative Acceptance Criteria for Postulating Pipe Break Locations

- June 11, 2019

- March 21, 2021

- January 11, 2023 RI-ISI application to RI-HELB

7 BACKGROUND/RELATED ACTIVITIES

8 Evolution of RI-Pressure Boundary Approvals (RI-ISI + RI-BER)

RI-method for a subset of Class 1 welds for a BWR (1998)

RI-method for all safety related (SR) & non safety related (NSR) welds for a PWR (1998)

RI-method for a subset of Class 1 welds for a PWR (1999)

Generic RI-method for SR and NSR welds for all BWR and PWR designs (1999)

Generic RI-method for BER welds for all BWR and PWR designs (2001)

RI-method for repair/replacement (RRA) for SR pressure boundary components (2005)

Streamlined RI-method for piping welds for all BWR and PWR designs (2007)

Updated RI-method for RRA for SR pressure boundary components (PBC) (2009)

RI-method for all SR and NSR piping and non piping components (2012)

Streamlined RI-method for piping and non piping component (2014)

Focused RI-method (i.e. a single item) for RRA for SR PBCs (2021)

Focused RI-method (i.e. a single item) for RRA for SR PBCs (2023)

9 RI-ISI Methodology Overview EPRI TR-112657, Rev B-A is the foundational methodology for risk characterization of the pressure boundary

- Codified in ASME Section XI, Appendix R, Supplement 2

- Endorsed in 10CFR50.55a

- ~ 60 US applications (BWRs and PWRs)

- Applied / adapted for use in seven other countries, including CANDU nuclear and conventional systems

- Applied / adapted to other components and programs including RI-repair/replacement, 10CFR50.69

- Adapted to addressed break exclusion region (BER) NDE requirements

- Streamlined RI-ISI (N716-1 endorsed in RG1.147)

- Conforms to guidance provided in RG 1.174

10 Step 1 - Determine RI-ISI Program Scope Step 2A - Assess Consequences of Pipe Failures Step 2B - Assess Failure Potential FMEA of Pipe Segments Step 3 - Determine and Characterize Risk Segments Step 4 - Select Elements and Inspections Step 5 - Perform Risk Impact Assessment Step 6 - Document RI-ISI Program Performance Monitoring Adjustments to Element Selection RI-ISI Methodology

11 Consequence Category Corresponding CCDP Range Corresponding CLERP Range HIGH CCDP > 1E-4 CLERP > 1E-5 MEDIUM 1E-6 < CCDP < 1E-4 1E-7 < CLERP < 1E-5 LOW CCDP < 1E-6 CLERP < 1E-7 Consequence Evaluation The goal of the consequence evaluation is to assign a consequence rank (High, Medium or Low) to the piping segment under evaluation.

12 Pipe Rupture Potential Expected Leak Conditions Degradation Mechanisms to which the Segment is Susceptible HIGH Large

- Flow Sensitive Flow Accelerated Corrosion MEDIUM Small

- Thermal Fatigue Thermal Stratification, Cycling, Striping Thermal Transients

- Stress Corrosion Cracking Intergranular Stress Corrosion Cracking Transgranular Stress Corrosion Cracking External Chloride Stress Corrosion Cracking Primary Water Stress Corrosion Cracking

- Localized Corrosion Microbiologically-Influenced Corrosion Pitting Crevice Corrosion

- Flow Sensitive Erosion-Cavitation LOW None

- No Degradation Mechanisms Present Failure Potential Assessment The goal of the failure potential assessment is to assign a failure potential rank (High, Medium or Low) to the piping segment under evaluation.

13 NONE MEDIUM HIGH LOW LOW (Cat. 7)

LOW (Cat. 7)

HIGH MEDIUM LOW LOW (Cat. 6)

LOW (Cat. 7)

CONSEQUENCE CATEGORY CCDP and CLERP Potential DEGRADATION CATEGORY Pipe Rupture Potential HIGH (Cat. 3)

HIGH (Cat. 1)

HIGH (Cat. 2)

MEDIUM (Cat. 5)

LOW (Cat. 6)

MEDIUM (Cat. 5)

MEDIUM (Cat. 4)

Consequence Evaluation Failure Potential Assessment (Degradation Mechanism)

RI-ISI Risk Ranking and Inspection Population

14 RI-ISI Risk Ranking and Inspection Population Class 1, 2, 3 and/or NNS systems

- 25 percent of high risk region (CAT1, 2 & 3)

- 10 percent of medium risk region (CAT4 & 5)

- augmented exams may be credited (e.g. IGSCC)

- Class 1 minimum trigger RI-HELB

- Methodology is founded upon and adapted from RI-ISI (TR-112657 Rev B-A)

- Strategies are a function of:

consequence of postulated failure and plant risk impact (e.g. must make plant change to reduce High Consequence to Medium or Low) medium or low risk impact; inspection and performance monitoring may be appropriate

15 Extension of RI-ISI Methodology to RI-BER and RI-HELB

16 Step 1 - Determine RI-ISI Program Scope Step 2A - Assess Consequences of Pipe Failures Step 2B - Assess Failure Potential FMEA of Pipe Segments Step 3 - Determine and Characterize Risk Segments Step 4 - Select Elements and Inspections Step 5 - Perform Risk Impact Assessment Step 6 - Document RI-ISI Program Performance Monitoring Adjustments to Element Selection Step 1 - Determine RI-HELB Program Scope Step 2A - Assess Consequences of Pipe Failures Step 2B - Assess Failure Potential FMEA of Pipe Segments Step 3 - Determine and Characterize Risk Segments Step 4 - Establish HELB Response Strategies Step 5 - Perform Risk Impact Assessment Step 6 - Document RI-HELB Program Performance Monitoring CoF Considerations The consequence evaluation for RI-HELB must consider the dynamic effects of a DEGB using the eight consequence evaluation criteria below consistent with 1006937 for RI-BER.

1 Containment Isolation Valves: valves in the vicinity of the break are assumed to fail unless survival is justified by plant design and/or analysis.

2 Containment Penetrations: assumed to fail if not designed or analyzed for a DEGB load. Design features can be credited to preclude DEGB loads.

3 Unrestrained Whipping Pipe Impact on Equal or Larger Nominal Pipe Size:

no impact except on thinner wall pipe where through wall cracks are assumed unless there is analytical and/or experimental justification.

4 Unrestrained Whipping Pipe Impact on Smaller Nominal Pipe Size: failure is assumed unless it is demonstrated capable by design or analysis. Both circumferential and longitudinal breaks are postulated except where analytical and/or experimental data demonstrate capability.

5 Unrestrained Whipping Pipe Impact on Structures, Systems and Components: plant specific criteria & analyses and/or SRP 3.6.2 are used to evaluate potential physical impacts of pipe whip. Engineering judgments based on plant design and analyses are used along with conservative assumptions to determine impacts.

6 Jet Impingement: plant-specific criteria & analyses and/or SRP 3.6.2 are used to evaluate potential impacts of jets. Engineering judgments based on plant design and analyses are used along with conservative assumptions to determine impacts.

7 Other Spatial Impacts: structures, systems and components in the area of the break are assumed to fail unless design/analyses or appropriate engineering judgments, based on plant design and spatial evaluations, justify otherwise. Equipment qualification for the DEGB environment must be considered as well as flooding and compartment overpressure.

8 Spatial Propagation: when postulating propagation to adjacent areas, both isolation success and failure are considered.

Extension of RI-ISI Methodology to RI-BER and RI-HELB

17 Actions Required for Risk Category 1 (High Risk) - High CoF/High PoF

For locations identified as susceptible to FAC, ensure that the FAC program is addressing the most important locations and monitoring This action reassigns the component to RC2 or RC4 depending on whether there are other DMs besides FAC

Go to RC2 or RC4 requirements as applicable Another DM Applies Actions required for Risk Category 2 (High Risk) - High CoF/Medium PoF

Perform plant modification to reduce the CoF to Medium plus perform 10%

inspections based on DM, or This action reassigns the component to RC5

Perform plant modification to reduce the CoF to Low, or This action reassigns the component to RC6

Follow existing deterministic HELB requirements including modifications if necessary Actions required for Risk Category 3 (High Risk) - Medium CoF/High PoF

For locations identified as susceptible to FAC, ensure that the FAC program is addressing the most important locations and monitoring This action reassigns the component to RC5 or RC6 depending on whether there are other DMs besides FAC

Go to RC5 or RC6 requirements as applicable Actions required for Risk Category 4 (Medium Risk) - High CoF/Low PoF

Perform plant modification to reduce the CoF to Medium, or This action reassigns the component to RC6

Perform plant modification to reduce the CoF to Low, or This action reassigns the component to RC7

Follow existing deterministic HELB requirements including modifications if necessary Another DM Applies Actions Required for Risk Category 5 (Medium Risk) - Medium CoF/Medium PoF

Perform plant modification to reduce the CoF to Low, or This action reassigns the component to RC6

Perform 10% inspections based on DM Actions Required for Risk Category 6 (Low Risk) - Medium CoF/Low PoF

None (Low Risk)

Actions required for Risk Category 5 (Medium Risk) - Low CoF/High PoF

For locations identified as susceptible to FAC, ensure that the FAC program is addressing the most important locations and monitoring This action reassigns the component to RC6 or RC7 depending on whether there are other DMs besides FAC

Go to RC6 or RC7 requirements as applicable Another DM Applies Actions Required for Risk Category 6 (Low Risk) - Low CoF/Medium PoF

None (Low Risk)

Actions Required for Risk Category 7 (Low Risk) - Low CoF/Low PoF

None (Low Risk)

YES NO YES NO YES NO Reassigned from RC4 Reassigned from RC2 Reassigned from RC4 Reassigned from RC2 or RC5 Reassign to RC5 or RC6 Reassign to RC6 or RC7 Reassign to RC6 RI-HELB Response Strategies

18 Summary The overall RI-ISI methodogly remains mostly unchanged Step 4 (Element Selection) becomes HELB Response Strategies Step 6 (Document RI-ISI Program) becomes Document RI-HELB Program Note: implementation protocol may also be different (e.g. 50.55a relief request not applicable)

19 DISCUSSION - RI-HELB METHODOLOGY

20 Overview Pilot Plant Scope Design, FSAR, & PRA Review (RI-ISI)

Consequence of failure (RI-BER)

Failure potential (Degradation Potential)

Risk Ranking & Inspection Element Section Change in Risk Assessment

21 Overview EPRI Report 1006937-A [RI-BER]

Adapted from EPRI TR-112657, Rev B-A [RI-ISI]

RI-BER includes the following additional evaluations Containment Isolation Valves Impact Containment Penetrations Impact Unrestrained Pipe Whip Impacts (Criterion 3 through 5)

Jet Impingement Impact Other Spatial Impacts Spatial Propagation

22 Pilot Plant Scope Non-safety related main steam cross-around piping from the high-pressure turbine to the moisture separators, and from the moisture separators to the low-pressure turbines

23 Design, FSAR & PRA Review Cross-around piping scope is inside turbine pipeway/cavity Main Steam Piping is also located in same area (equalizing header, turbine stop & control valves etc.)

Main Steam pressure and temperature much higher than cross-around Main Steam HELB analysis per 1972 AEC Letter to envelope the cross-around piping scope Based on PRA, a medium consequence (loss of main condenser)

[RI-ISI]

RI-BER Consequence evaluation considered next

24 Consequence Evaluation Plant Walkdown Required to Assess Spatial Impacts Criterion 1 and 2: Cross-around scope far removed from containment isolation valves and penetrations Criterion 3-6 (Pipe Whip and Jet impingement):

At least one pair of turbine stop & control valves assumed to fail because of proximity

Loss of main condenser due to MSIV closure or loss of EHC, etc.

Structural impact bounded by main steam and walkdown confirmation Criterion 7 (other Spatial Impacts): flooding not a concern, but two MCCs outside turbine cavity doors assumed to fail due to door missile or steam impact (Walkdown)

Criterion 8 (Spatial Propagation): steam propagates up to the turbine building ceiling where there is no PRA equipment. There is also blowout panels on the upper floor (Walkdown)

25 Consequence Evaluation Results Several PRA Calculations performed assuming loss of main condenser, failure of a turbine stop & control valve pair (MSIV isolation is required), failure of two MCCs identified during walkdown and other impacts to model both large and small breaks, MSIV isolation etc.

Medium Consequence (CCDP<1E-4 and CLERP<1E-5)

26 Degradation Mechanism Assessment No Degradation Mechanism identified from the evaluation All piping and components are therefore assigned a low failure potential rank

27 Risk Ranking & Inspection Population RI-ISI Perspective Risk Category 6 (Low Risk) based on Medium Consequence and Low failure Potential Rank Risk Category 6 requires no inspections

28 NONE MEDIUM HIGH LOW LOW (Cat. 7)

LOW (Cat. 7)

HIGH MEDIUM LOW LOW (Cat. 6)

LOW (Cat. 7)

CONSEQUENCE CATEGORY CCDP and CLERP Potential DEGRADATION CATEGORY Pipe Rupture Potential HIGH (Cat. 3)

HIGH (Cat. 1)

HIGH (Cat. 2)

MEDIUM (Cat. 5)

LOW (Cat. 6)

MEDIUM (Cat. 5)

MEDIUM (Cat. 4)

Consequence Evaluation Failure Potential Assessment (Degradation Mechanism)

Change in Risk Assessment Based on Methodologies risk impact is not required for risk category 6 because even if welds were being removed from inspection the increase risk would be very low Since no inspections are required and no inspections were being conducted, the change in risk is zero

29 Summary The overall RI-ISI methodogly remains mostly unchanged Step 4 (Element Selection) becomes HELB Response Strategies Step 6 (Document RI-ISI Program) becomes Document RI-HELB Program Note: implementation protocol may also be different (e.g. 50.55a relief request not applicable)

30 DISCUSSION - RI-HELB TOPICAL REPORT

31 Summary of RI-HELB Report

32 Summary of RI-HELB Report

33 Summary of RI-HELB Report

34 Discussion - RI-HELB Topical Report Topical Report Implementation Protocol(s)

Schedule

35 ACTION ITEMS/CLOSING REMARKS

36

w w w. e p r i. c o m TOGETHERSHAPING THE FUTURE OF ENERGY

v t e Letter Sequence Meeting
EPID:L-2024-TOP-0003, (Open)
Initiation Acceptance... Administration Meeting, Meeting, Meeting, Meeting, Meeting, Meeting, Meeting Questions 19 May 2025 19 May 2025 Answers Results Approval, Approval, Approval, Approval, Approval, Approval, Approval Other: ML24214A027, ML24214A034, ML25036A032, ML25036A042, ML25044A001, ML25239B555
MONTHYEAR2024-05-21 [Table View]

ML24078A378

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