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Enclosure 2: Addressing Component Fatigue for NuScale DCA, November 20, 2018
	ML18331A160
Person / Time
Site:	NuScale
Issue date:	11/20/2018
From:	; NuScale
To:	; Office of New Reactors
Shared Package
ML18331A220	List: ML18331A159; ML18331A160;
References
	L0-1118-63008 PM-1118-63007-NP, Rev 0
	Download: ML18331A160 (26)
	v • d • e

L0-1118-63008 :

Addressing Component Fatigue for NuScale DCA, November 20, 2018, nonproprietary version NuScale Power, LLC 1100 NE Circle Blvd., Suite 200 Corvallis, Oregon 97330 Office 541.360-0500 Fax 541.207 .3928 www.nuscalepower.com

Introduction

Provide an outline of the ASME Service Level evaluation and fatigue analyses performed.

Address SRP 3.9.3 guidance for ASME Class 1, 2, and 3 components regarding secondary stresses and fatigue:

"Fatigue evaluations are required by the Code for all Class 1 components.

Fatigue evaluations should also be completed for all Code Class 2 and 3 components and component supports, and core support structures that are subject to thermal cyclic effects or dynamic cyclic loads. The scope, methods, and results of fatigue evaluations should be reviewed by the staff. Fatigue analyses of components and supports should be completed if the fatigue evaluations so indicate and these analyses, as well as their results, should be reviewed and compared with the guidance in the Code."

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SRP 3.9.3 Guidance Process

Define transients and ASME Service Levels

Calculate transient pressures and temperatures SRP 3.9.3: The scope,

Operating experience methods, and results of

NuScale unique loading fatigue evaluations should

Limiting /1 T locations be reviewed by the staff.

SRP 3.9.3: Fatigue

Analyses of bounding locations analyses of components based on evaluation ensure and supports should be components meet ASME Code completed if the fatigue evaluations so indicate 3

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Background

American Society of Mechanical Engineers (ASME)

Boiler and Pressure Vessel Code (BPVC) require that service levels be identified for the events that comprise each component's design basis.

- Level A Service Conditions -are associated with events that are planned to occur due to routine operation of the plant. Examples include startup, power maneuvers, hot standby, and shutdown.

- Level B Service Conditions - are associated with transients that occur often enough that the operability of the plant is not affected. These transients will not result in damage requiring repairs.

- Level C Service Conditions - may result in permanent deformation and repairs may be required to correct large deformations in areas of structural discontinuity.

- Level D Service Conditions - may result in gross deformation and dimensional instability. Repair or replacement of components may be necessary to correct mechanical damage.

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ASME Loads and Thermal Evaluations

Single application of a load resulting in gross deformation and/or collapse of the structure. These types of loads are limited by the load carrying capacity of the components. Typical loads in this category are pressure and external mechanical loads (seismic). Other than the maximum pressure and temperature of transients this evaluation does not consider thermal stresses (Design Condition, Level B-D - primary stress analyses).

Continued deformation of structures due to simultaneous application of sustained loads with repetitive loadings (Level A and B). The phenomenon is known as ratcheting and would result in gross deformation of components over time. The components susceptible to this mechanism are characterized with large temperature differences through the thickness of the components that change cyclically along with the application of simultaneous sustained load such as pressure. In absence of a driving force (such as pressure which causes stresses with constant principal directions) this phenomenon will not occur even if large temperature differences exist within the component. Absence of ratcheting or rather cessation of it within a few cycles is called shakedown. Structures that show initial ratcheting before shakedown also exhibit high propensity to fatigue and much reduced service life.

Repetitive application of loadings with varying magnitude can cause crack initiation of components. The source of the loading can be any repetitive or cyclic loading (flow induced vibration, operating basis earthquake, Level A and B thermal transients, etc.) and the effect of those loads is compounded over time.

Fatigue exists even in the absence of any primary stresses and it is also dependent on the environment, surface finish, geometry and other corrosion mechanisms including stress corrosion cracking (SCC). The rate of temperature change has a large influence on fatigue and rapid transients result in very high "skin" surface stresses leading to rapid crack initiation. Depending on the nature of the crack it may be arrested but crack growth is not considered in design.

NRC Regulatory Guide 1.207 (based on NUREG-6909) requires the evaluation of environmental effects on fatigue for components subject to primary coolant environment.

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ASME Stress Categories Service Primary Stress

Secondary Stress Peak Level

General Local

Bending Expansion

Membrane Fatigue

Membrane Membrane (Pb) . (Pe) plus (F)

, (PM) (Pd

Bending (Q)

Design N/A N/A N/A A

B N/A "

N/A " "

N/A C

"" "" "" " N/A N/A N/A N/A N/A N/A D

Test

"" "" N/A N/A N/A 6

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Thermal Transient Development ((

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(( Thermal Transient Definitions w

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Thermal Transient Example ((

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Component Evaluation Process ((

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Reactor Module Outline Model ((

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Reactor Module Outline Model (( w

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Reactor Module Outline Model ((

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Fatigue Evaluations - General Areas ((

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Fatigue Evaluations - General Areas ((

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Fatigue - General Areas ((

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Fatigue - General Areas ((

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Fatigue Evaluations - Process Line Areas ((

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Fatigue Evaluations - Process Line Areas ((------------ --------------- -------

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Fatigue Evaluations - Process Line Areas ((

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Bounding Locations for Stress Analyses ((

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Summary

NuScale has performed fatigue evaluations of the NPM that meet the intent of SRP 3.9.3, specifically:

            - Plant thermal transients have been defined and calculated for all Class 1 and 2 components
            - An evaluation of thermal stresses was performed for all NPM Class 1 and 2 components by

considering operating experience
NuScale unique transients
Overall thermal response of NPM (outline model)
EAF

            - ASME including fatigue analyses were performed for locations for which the evaluation so indicated "SRP 3.9.3: Fatigue analyses of components and supports should be completed if the fatigue evaluations so indicate" 23 PM-1118-63007-NP Revision: 0                                 Copyright 2018 by NuScale Power, LLC.

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Portland Office Richland Office 6650 SW Redwood Lane, 1933 Jadwin Ave., Suite 130 Suite 210 Richland, WA 99354 Portland, OR 97224 541.360.0500 971.371. 1592 Arlington Office Corvallis Office 2300 Clarendon Blvd., Suite 1110 1100 NE Circle Blvd., Suite 200 Arlington, VA 22201 Corvallis, OR 97330 541.360.0500 London Office 1st Floor Portland House Rockville Office Bressenden Place 11333 WoodglenAve., Suite 205 London SW1 E 5BH Rockville, MD 20852 United Kingdom 301. 770. 0472 +44 (0) 2079 321700 Charlotte Office 2815 Coliseum Centre Drive, Suite 230 Charlotte, NC 28217 980.349.4804 http://www.nuscalepower.com

                      - Twitter: @NuScale_Power NUSCALE' Power for all humankind 24 PM-1118-63007-NP Revision: O                                    Copyright 2018 by NuScale Power, LLC.

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L0-1118-63008 : Affidavit of Zackary W. Rad, AF-1118-63009 NuScale Power, LLC 1100 NE Circle Blvd., Suite 200 Corvallis, Oregon 97330 Office 541.360-0500 Fax 541.207.3928 www.nuscalepower.com}}

ML18331A160

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