Regulatory Guide 1.130

Service Limits & Loading Combinations for Class 1 Plate-And-Shell-Type Component Supports

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Issue date:	10/31/1978
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RG-1.130, Revision 1
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U.S. NUCLEAR REGULATORY COMMISSION

Revision 1 October 1978 REGULATORY GUIDE

OFFICE OF STANDARDS DEVELOPMENT

Regulatory Guide 1.130

SERVICE LIMITS AND LOADING COMBINATIONS

FOR CLASS 1 PLATE-AND-SHELL-TYPE COMPONENT SUPPORTS

• 1

A. INTRODUCTION

General Design Criterion 2, "Design Bases for Protection Against Natural Phenomena," of Appen dix A, "General Design Criteria for Nuclear Power Plants," to 10 CFR Part 50, "Domestic Licensing of Production and Utilization Facilities," requires that the design bases for structures, systems, and compo nents important to safety reflect appropriate combi nations of the effects of normal and accident condi tions with the effects of natural phenomena such as earthquakes. The failure of members designed to support safety-related components could jeopardize the ability of the supported component to perform its safety function.

This guide delineates acceptable levels of service limits and appropriate combinations of loadings as sociated with normal operation, postulated accidents, and specified seismic events for the design of Class 1 plate-and-shell-type component supports as defined in Subsection NF of Section III of the American So ciety of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code. 1 This guide applies to light water-cooled reactors.

The Advisory Committee on Reactor Safeguards has been consulted concerning this guide and has concurred in the regulatory position.

B. DISCUSSION

Load-bearing members classified as component supports are essential to the safety of nuclear power

• Lines indicate substantive changes from previous issue.

American Society of Mechanical Engineers Boiler and Pressure Vessel Codes Section 111, Division 1, 1977 Edition, including the

1977 Winter Addenda thereto. Copies of the Code may be ob tained from the American Society of Mechanical Engineers, United Engineering Center, 345 East 47th Street, New York, N.Y. 10017.

plants because they retain components in place during loadings associated with normal and upset plant con ditions under the stress of specified seismic events, thereby permitting system components to function properly. They also prevent excessive component movement during the loadings associated with emer gency and faulted plant conditions combined with a specified seismic event or other natural phenomena, thereby helping to mitigate system damage. Compo nent supports are deformation-sensitive because large deformations in component supports may signifi cantly change the stress distribution in the support system and its components.

In order to provide a consistent level of safety, the ASME Boiler and Pressure Vessel Code classifica tion for component supports should, as a minimum, be the same as that of the supported components.

This guide delineates levels of service limits and loading combinations, as well as supplementary criteria, for Class 1 plate-and-shell-type component supports as defined by NF-1212 of Section III of the Code. Snubbers are not addressed in this guide.

Subsection NF of Section III permits the use of three methods for the design of Class I plate-and shell-type component supports: (1) linear elastic analysis, (2) load rating, and (3) experimental stress analysis. For each method, the ASME Code de lineates allowable stress or loading limits for various Code service levels, as defined by NF-3113 and NCA-2142.2(b) of Section III, so that these limits can be used in conjunction with the resultant loadings or stresses from the appropriate plant conditions.

Since the Code does not specify loading combina tions, guidance is needed to provide a consistent basis for the design of component supports.

Component supports considered in this guide are located within Seismic Category I structures and are USNRC REGULATORY GUIDES

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therefore assumed to be protected against loadings from natural phenomena or man-made hazards other than the specified seismic events. Thus only the specified seismic events need to be considered in combination with the loadings associated with plant conditions to develop appropriate loading combina tions. When loadings caused by natural phenomena other than seismic events, such as the subsidence of the land surface as a result of large-scale ground water withdrawals exist, they should be specified in the Design Specification, and the loading combina tions reflecting the inclusion of these loadings should be reviewed.

1. Design by Linear Elastic Analysis When the linear-elastic-analysis method is used to design Class I plate-and-shell-type component sup ports, material properties are given by Tables I-I. 1,

1-1.2, and 1-11.1 of Appendix I to Section III and Table I of the latest accepted version 2 of Code Case

1644. These tables list values for the design stress intensity Sm at various temperature

s. Yet level D

service limits are determined by S., Sy, and S.. The load-rating method also requires the use of Su.

The minimum yield strength S, at various temper atures could be found in Tables 1-2.1, 1-2.2, and

1-13.3 of Appendix I to Section III and Table 3 of the latest accepted version 2 of Code Case 1644 for the design of Class 1 plate-and-shell-type component supports, but values for the ultimate tensile strength S. above room temperature are not listed in Section III. The interim methods proposed by this guide should therefore ble used to obtain values of Su at temperature in order to provide a safe design margin.

While NF-3222.3 and F-1323.1(a) of Section III

permit the increase of allowable service limits under various loading conditions, F-1370(c) limits the in crease to two-thirds of the critical buckling strength of the component support at temperature. However, NF 3211 (d) and NB 3220 do not specify the percent age of critical buckling strength for level A service limits. Since buckling prevents "shake-down"

in a load-bearing member, it must be regarded as control ling for the level A service limits, and F-1370(c)

must be regarded as controlling for the level D serv ice limits. Also, buckling is the result of the interac tion of the configuration at the load-bearing member and its material properties (i.e., elastic modulus E

and minimum yield strength S,). Because both of these material properties change with temperature, the critical buckling stresses should be calculated

2 Regulatory Guide 1.85, "Code Case Acceptability-ASME Sec tion III Materials," provides guidance for the acceptability of ASME Section III Code Cases and their revisions, including Code Case 1644. Supplementary provisions for the use of specified code cases and their revisions may also be provided and should be considered when applicable.

with the values of E and S, of the component support material at temperature.

Allowable service limits for bolted connections are derived on a different basis that varies with the size of the bolt. For this reason, the increases permitted by NF-3222.3 and F-1323. 1(a) of Section III are not directly applicable to bolts and bolted connections.

2. Design by Load Rating When load-rating methods are used, Subsection NF

and Appendix F of Section III do not provide a level D load rating. This guide provides an interim method for the determination of the load rating for level D

limits.

3. Design by Experimental Stress Analysis While the collapse load for the experimental stress-analysis method is defined by 11-1430 in Ap pendix II to Section III, the design limits for the experimental-stress-analysis method for various operating condition categories are not delineated.

This deficiency can be remedied by the interim method described in this guide.

4. Large Deformations The design of component supports is an integral part of the design of a system and its components. A

complete and consistent design is possible only when system/component/component-support interaction is properly considered. When all three are evaluated on an elastic basis, the interaction is usually valid be cause individual deformations are small. However, if plastic analysis methods are used in the design proc ess, large deformations that would result in substan tially different stress distributions may occur.

For the evaluation of the level D, service limits, Appendix F to Section III permits the use of plastic analysis methods in certain acceptable combinations for all three elements. These acceptable combinations are selected on the assumption that component sup ports are more deformation-sensitive (i.e., their de formation in general will have a large effect on the stress distribution in the system and its components).

Since large deformations always affect stress dis tribution, care should be exercised even if the plastic analysis method is used in the Appendix-F-approved methodology combination. This is especially impor tant for identifying buckling or instability problems, where the change of geometry should be taken into account to avoid erroneous results.

5. Function of the Supported System In selecting the level of service limits for different loading combinations, the designer must take into ac count the function of the supported system. To ensure that systems whose normal function is to prevent or mitigate consequences of events associated with an emergency or faulted plant condition (e.g., the func

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tion of ECCS during faulted plant conditions) will operate properly regardless of plant condition, the Code level A or B service limits of Subsection NF

(which are identical) or other justifiable limits pro vided by the Code should be used.

6. Deformation Limits Since component supports are deformation sensitive load-bearing elements, satisfying the serv ice limits of Section III will not automatically ensure their proper function. Deformation limits, if specified by the Code Design Specification, may be the con trolling criterion. On the other hand, if the function of a component support is not required for a particu lar plant condition, the stresses or loads resulting from the loading combinations under the particular plant condition do not need to satisfy the design lim its for the plant condition.

7. Definitions Critical Buckling Strength. The strength at which lateral displacements start to develop simultaneously with in-plane or axial deformations.

Design Condition. The loading condition defined by NF-3112 of Section III of the ASME Boiler and Pressure Vessel Code.

Emergency Plant Condition. Those operating con ditions that have a low probability of occurrence.

Faulted Plant Condition. Those operating condi tions associated with postulated events of extremely low probability.

Levels of Service Limits. Four levels (A, B, C, and D) of service limits defined by Section III of the Code for the design of loadings associated with dif ferent plant conditions for components and compo nent supports in nuclear power plants.

Normal Plant Condition. Those operating condi tions in the course of system startup, operation, hot standby, refueling, and shutdown other than upset, emergency, or faulted plant conditions.

Operating Basis Earthquake (OBE). As defined in Appendix A "Seismic and Geologic Siting Criteria for Nuclear Power Plants,"' to 10 CFR Part 100,

"Reactor Site Criteria."

Operating Condition Categories. Categories of de sign limits for component supports as defined by NF-3113 of Section III of the ASME Code.

Plant Conditions. Operating conditions of the plant categorized as normal, upset, emergency, and faulted

,plant conditions.

Safe Shutdown Earthquake (SSE). As defined in Appendix A to 10 CFR Part 100.

Service Limits. Stress limits for the design of com ponent supports as defined by Subsection NF of Sec tion III.

Specified Seismic Events. Operating Basis Earth quake and Safe Shutdown Earthquake.

System Mechanical Loadings. The static and dynamic loadings that are developed by the system operating parameters, including dead weight, pres sure, and other external loadings, but excluding ef fects resulting from constraints of free-end move ments and thermal and peak stresses.

Ultimate Tensile Strength. Material property based on engineering stress-strain relationship.

Upset Plant Condition. Those deviations from the normal plant condition that have a high probability of occurrence.

C. REGULATORY POSITION

ASME Code Class 1 plate-and-shell-type compo nent supports except snubbers, which are not ad dressed in this guide, should be constructed to the rules of Subsection NF of Section III of the Code, as supplemented by the following: 3

1. The classification of component supports should, as a minimum, be the same as that of the supported components.

2. Values of Su at temperature, when they are not listed in Section III, should be estimated by Method 1, Method 2, or Method 3, as described below, on an interim basis until Section III includes such values. Values of S, at temperature listed by Tables 1-2.1, 1-2.2, and 1-13.1 of Appendix I and Table 3 of the latest accepted version1 of Code Case

1644 of Section III may be used for the interim calculation.

a. Method 1. This method applies to component support materials whose values of ultimate tensile strength at temperature have not been tabulated by their manufacturers or are not available.

S,, = u S,,r Syr where S. = ultimate tensile strength at temperature t to be used to determine the design limits Sur = ultimate tensile strength at room tem perature tabulated in Section III, Ap pendix I, or the latest accpeted version'

of Code Case 1644

3 If the function of a component support is not required during a plant condition, the design limits of the support for that plant con dition need not be satisfied, provided excessive deflections or failure of the support will not result in the loss of function of any other safety-related system.

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Sy = minimum yield strength at temperature t tabulated in Section III, Appendix I, or the latest accepted version2 of Code Case 1644 Syr = minimum yield strength at room tem perature, tabulated in Section III, Ap pendix I, or the latest accepted version 2 of Code Case 1644.

b. Method 2. Since the listed values of Sm at temperature in Section III will always be less than one-third of the corresponding values of ultimate strength Su at temperature, S. at temperature may be approximated by the value of

3 Si at the same temperature.

c. Method 3. This method applies to component support materials whose values of ultimate strength Su at temperature are available as tabulated by their manufacturers.

Su Sur Su , but not greater than Sur Stur where Su= ultimate tensile strength at temperature t to be used to determine the design limits Sur = ultimate tensile strength at room tem perature tabulated in Section III, Ap pendix 1, or the latest accepted version2 of Code Case 1644

§u = ultimate tensile strength at temperature t tabulated by manufacturers in their catalogs or other publications Sur = ultimate tensile strength at room tem perature tabulated by manufacturers in the same publications.

3. Service limits for component supports designed by linear elastic analysis should always be limited by the critical buckling strength. The critical buckling strength should be calculated using material at tem perature properties. A design margin of 2 for flat plates and 3 for shells should be maintained for loadings combined according to Regulatory Position

4 of this guide. Service limits related to critical buckling strength should not be increased unless the Code specifically allows such an increase.

4. Component supports subjected to the combined loadings of (a) the vibratory motion of the OBE and (b) system mechanical loadings4 associated with either (a) the Code design condition or (b) normal or

4 System mechanical loadings include all non-self-limiting load ings and do not include effects resulting from constraints of free end displacements and thermal or peak stresses.

5Since component supports are deformation-sensitive in the per formance of their service requirements, satisfying these limits does not ensure the fulfilling of their functional requirements.

Any deformation limits specified by the design specification may be controlling and should be satisfied.

upset plant conditions should be designed as follows. 5-6 a. The service limits of (1) NF-3221.1 and NF

3221.2 for design loadings, (2) NF-3222 for level A

service limits, and (3) Regulatory .Position 3 of this guide should not be exceeded for component supports designed by the linear-elastic-analysis method.

b. The load rating for level A limits or level B

limits of NF-3262.2 of Section III should not be ex ceeded for component supports designed by the load-rating method.

c. The collapse load determined by 11-1400 of Section III divided by 1.7 should not be exceeded for component supports designed by the experimental stress-analysis method.

5. Component supports subjected to the system mechanical loadings4 associated with the emergency plant condition should be designed within the fol lowing design limits except when the normal function of the supported system is to prevent or mitigate the consequences of events associated with the emer gency plant condition (at which time Regulatory Po sition 7 applies):5"'

a. The service limits of NF-3224 of Section III

and Regulatory Position 3 should not be exceeded for component supports designed by the linear-elastic analysis method.

b. The load rating for level C limits of NF

3262.2 of Section III should not be exceeded for component supports designed by the load-rating method.

c. The collapse load determined by 11-1400 of Section III and divided by 1.3 should not be exceeded for component supports designed by the experimental-stress-analysis method.

6. Component supports subjected to the combined loadings of (a) the vibratory motion of SSE and (b)

the system mechanical loadings 4 associated with the normal plant condition and (c) the dynamic system loadings associated with the faulted plant condition should be designed within the following design limits except when the normal function of the supported system is to prevent or mitigate the consequences of events associated with the faulted plant condition (at which time Regulatory Position 7 applies):.5 a. The service limits of F-1323.1(a) and F-1370(c) of Section III should not be exceeded for

6Since the design of component supports is an integral part of the design of the system and the design of the component, the de signer must make sure that methods used for the analysis of the system, component, and component support are compatible (see Table F-1322.2-1 of Appendix F to Section I11). Large deforma tions in the system or components should be considered in the design of component supports.

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component supports designed by the linear-elastic analysis method.

b. The value of T.L. x 0.7 -&- should not be SI'

exceeded, where T.L. and Su are defined according to NF-3262.1 of Section III and S§, is the ultimate tensile strength of the material at service temperature for component supports designed by the load-rating method.

c. The collapse load determined by 11-1400 and divided by 1.1 should not be exceeded for component supports designed by the experimental-stress-analysis method.

d. If plastic methods are used for the design of component supports, the combined loadings of Reg ulatory Position 6 should include all loads such as thermal loads and constraints of free displacements, which contribute to expansion stress intensities, and the service limits of F-1324 and F-1370(c) of Sec tion III should not be exceeded.

7. Component supports in systems whose normal function is to prevent or mitigate the consequences of events associated with an emergency or faulted plant condition should be designed within the limits de scribed in Regulatory Position 4 or other justifiable limits such as the level C or level D service limits provided by the Code. These limits should be defined by the design specification so that the function of the supported system will be maintained when the sup ports are subjected to the loading combinations de scribed in Regulatory Positions 5 and 6.

D. IMPLEMENTATION

The purpose of this section is to provide guidance to applicants and licensees regarding the NRC staff's plans for using this regulatory guide.

Except in those cases in whicih the applicant pro poses an acceptable alternative method for complying with the specified portions of the Commission's reg ulations, the method described herein will be used in the evaluation of submittals for construction permit applications docketed after October 31, 1978. If an applicant wishes to use this regulatory guide in de veloping submittals for construction permit applica tions docketed on or before October 31,

1978, the pertinent portions of the application will be evaluated on the basis of this guide.

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