Evaluations of NRC SeismicStructural Regulations and 

Regulatory Guidance, and 

Simulation-Evaluation Tools 

for Applicability to Small 

Modular Reactors (SMRs)

Office of Nuclear Regulatory Research

NUREG/CR-7193
NRC Reference Material 

As of November 1999, you may electronically access 

NUREG-series publications and other NRC records at 

NRC’s Public Electronic Reading Room at 

http://www.nrc.gov/reading-rm.html. Publicly released 

records include, to name a few, NUREG-series 

publications; Federal Register notices; applicant, 

licensee, and vendor documents and correspondence; 

NRC correspondence and internal memoranda; bulletins 

and information notices; inspection and investigative 

reports; licensee event reports; and Commission papers 

and their attachments. 

NRC publications in the NUREG series, NRC 

regulations, and Title 10, “Energy,” in the Code of

Federal Regulations may also be purchased from one 

of these two sources. 

1. The Superintendent of Documents

 U.S. Government Printing Office

Mail Stop SSOP

Washington, DC 20402–0001

Internet: bookstore.gpo.gov

Telephone: 202-512-1800

Fax: 202-512-2250 

2. The National Technical Information Service 

Springfield, VA 22161–0002

www.ntis.gov

1–800–553–6847 or, locally, 703–605–6000 

A single copy of each NRC draft report for comment is 

available free, to the extent of supply, upon written 

request as follows:

Address: U.S. Nuclear Regulatory Commission

 Office of Administration 

Publications Branch

 Washington, DC 20555-0001

E-mail: DISTRIBUTION.RESOURCE@NRC.GOV

Facsimile: 301–415–2289 

Some publications in the NUREG series that are 

posted at NRC’s Web site address 

http://www.nrc.gov/reading-rm/doc-collections/nuregs 

are updated periodically and may differ from the last 

printed version. Although references to material found on 

a Web site bear the date the material was accessed, the 

material available on the date cited may subsequently be 

removed from the site.

Non-NRC Reference Material 

Documents available from public and special technical 

libraries include all open literature items, such as books, 

journal articles, transactions, Federal Register notices, 

Federal and State legislation, and congressional reports. 

Such documents as theses, dissertations, foreign reports 

and translations, and non-NRC conference proceedings 

may be purchased from their sponsoring organization. 

Copies of industry codes and standards used in a 

substantive manner in the NRC regulatory process are 

maintained at—

The NRC Technical Library

Two White Flint North

11545 Rockville Pike

Rockville, MD 20852–2738 

These standards are available in the library for reference 

use by the public. Codes and standards are usually 

copyrighted and may be purchased from the originating 

organization or, if they are American National Standards, 

from—

American National Standards Institute

11 West 42nd Street

New York, NY 10036–8002

www.ansi.org

212–642–4900 

AVAILABILITY OF REFERENCE MATERIALS

IN NRC PUBLICATIONS

Legally binding regulatory requirements are stated only 

in laws; NRC regulations; licenses, including technical 

specifications; or orders, not in NUREG-series 

publications. The views expressed in contractorprepared publications in this series are not necessarily 

those of the NRC.

The NUREG series comprises (1) technical and 

administrative reports and books prepared by the staff 

(NUREG–XXXX) or agency contractors (NUREG/CR–

XXXX), (2) proceedings of conferences (NUREG/CP–

XXXX), (3) reports resulting from international 

agreements (NUREG/IA–XXXX), (4) brochures 

(NUREG/BR–XXXX), and (5) compilations of legal 

decisions and orders of the Commission and Atomic and 

Safety Licensing Boards and of Directors’ decisions

under Section 2.206 of NRC’s regulations (NUREG–

0750).

DISCLAIMER: This report was prepared as an account 

of work sponsored by an agency of the U.S. 

Government. Neither the U.S. Government nor any 

agency thereof, nor any employee, makes any warranty, 

expressed or implied, or assumes any legal liability or 

responsibility for any third party’s use, or the results of 

such use, of any information, apparatus, product, or 

process disclosed in this publication, or represents that 

its use by such third party would not infringe privately 

owned rights.
Evaluations of NRC SeismicStructural Regulations and 

Regulatory Guidance, and 

Simulation-Evaluation Tools 

for Applicability to Small 

Modular Reactors (SMRs)

Manuscript Completed: February 2013

Date Published: March 2015

Prepared by:

Robert J. Budnitz, Dismitrios Konstantinidis*

Earth Sciences Division

Lawrence Berkeley National Laboratory

University of California, Berkeley, CA 94720

Zhiguang Zhou**

Pacific Earthquake Engineering Research Center

University of California, Berkeley, CA 94720

*Now at Department of Civil Engineering

 McMaster University, Hamilton, Ontario, ON L8S 4L7, Canada

**Now at College of Civil Engineering

 Tongji University, Shanghai, 200092 China

Thomas J. Herrity, NRC Technical Monitor

Office of Nuclear Regulatory Research

NUREG/CR-7193

iii 

ABSTRACT

This report consists of two different evaluations sponsored by the U.S. Nuclear Regulatory 

Commission (NRC) and performed by Lawrence Berkeley National Laboratory. The first 

evaluation covers NRC regulatory guidance in the seismic-structural area. The second 

evaluation covers several seismic-structural simulation tools used in NRC regulatory 

applications. Each evaluation examines the appropriateness of the regulatory guidance 

(provided in regulations, guidance, review plans, etc.), or of the simulation tool for its applicability 

to small modular reactors (SMRs). The objective of each evaluation is to address the following: 

The bulk of NRC’s regulatory work on nuclear power reactor safety has been concentrated for

decades on large light-water reactors (LWRs). While the regulations are technology neutral, 

many of the agency’s positions have evolved with large LWRs as the sole technology of interest. 

Also, the technical analysis tools (computer codes) used in reactor safety guidance, either by the 

NRC itself or by its licensees and applicants, including structural analysis tools as well as those 

used to determine ground motion and to analyze soil structure interaction (SSI) effects, have 

been used to analyze large LWRs. This report examined whether regulatory guidance, or the 

analysis tools currently used in the seismic-structural area, could benefit from modification to 

better address small modular reactors (SMRs). It concluded that most documents reviewed do 

not need any modifications and are acceptable as currently written.

Recommendations for modifications are presented as appropriate. Also, it concluded that the 

software packages reviewed should yield acceptable results when applied to an SMR. The 

report can be used to inform the NRC’s efforts to update regulatory guidance in support of 

licensing reviews of SMR applications. 

v 

FOREWORD

The current U.S. Nuclear Regulatory Commission (NRC) licensing framework for power reactors 

was developed primarily to address the safety of large LWRs (light water reactors.) The vast 

majority of experience over the last 50 years has also been in regulating large LWRs. 

In the last several years, small modular reactors (SMRs) have generated sufficient commercial 

interest to warrant NRC preparations for a review of one or more SMR designs. Therefore, the 

Office of Nuclear Regulatory Research (RES) initiated a review of existing regulatory guidance in 

the seismic-structural area. The NRC staff particularly focused on guidance for seismic 

interactions between smaller modular nuclear units, especially given the multiple configurations 

possible for SMRs. The SMR units could be built sequentially over many years but the units 

could be closely located, resulting in multiple interaction and response scenarios. 

Advances in the state of knowledge and new abilities to model the seismic input and responses 

and to model seismic ground motions and soil-structure-interaction effects provide new 

capabilities to model and analyze the plant. RES wanted to identify whether an SMR design 

would present any unique or unexpected issues to a reviewer using these new tools for soil 

structure interaction (SSI) analysis. 

The review identified some areas of NRC guidance that could be improved for SMRs. In some 

technical areas, the current guidance is not appropriate for SMRs, or changes are appropriate to 

improve clarity or to reduce possible misinterpretations. Also, the review concluded that existing 

analysis tools can—in the hands of an appropriately skilled practitioner—give proper results. 

The report can be used to inform the NRC’s efforts to update regulatory positions and guidance 

in support of licensing reviews of SMR applications. 

TABLE OF CONTENTS 

Section Page 

vii 

ABSTRACT ................................................................................................................................... iii 

FOREWORD ................................................................................................................................. v 

TABLES ...................................................................................................................................... ix 

EXECUTIVE SUMMARY ............................................................................................................. xi 

ACKNOWLEDGMENT ................................................................................................................ xiii 

ABBREVIATIONS AND ACRONNYMS ...................................................................................... xv 

1. EVALUATION OF NRC SEISMIC-STRUCTURAL REGULATORY GUIDANCE FOR 

APPLICABILITY TO SMALL MODULAR REACTORS (SMRs) ......................................... 1 

1.1 Introduction ............................................................................................................ 1 

1.2 The Work—Three Phases ..................................................................................... 2 

1.3 List of Relevant Regulations, Regulatory Guides, ISGs, SRP Sections, and 

Consensus Codes & Standards ............................................................................ 2 

1.3.1 NRC Regulations: General Design Criteria (Parts of 10 CFR 50, 

Appendix A) ............................................................................................... 2 

1.3.2 Specific NRC Regulations ......................................................................... 3 

1.3.3 NRC Regulatory Guides ............................................................................ 3 

1.3.4 NRC Interim Staff Guidance ...................................................................... 4 

1.3.5 NRC Standard Review Plan (SRP) Sections (NUREG-0800) ................... 5 

1.3.6 Consensus Codes and Standards ............................................................. 6 

1.4 Categorization and Preliminary Evaluation ............................................................ 6 

1.4.1 Category One, No Changes Needed ......................................................... 6 

1.4.2 Category Two, Modest Changes May Be Desired ................................... 11 

1.4.3 Category Three, Important Changes May Be Desired ............................. 21 

1.5 Evaluation of Each Regulatory Document (from Table 1-2) for Which Modest

Changes May Be Desired ................................................................................... 26 

1.5.1 Regulatory Guide 1.57, “Design Limits and Loading Combinations for 

Metal Primary Reactor Containment System Components”(Revision 1, 

March 2007)............................................................................................. 26 

1.5.2 Regulatory Guide 1.122, “Development of Floor Design Response 

Spectra for Seismic Design of Floor-Supported Equipment or 

Components” (Revision 1, 1978) ............................................................. 27 

1.5.3 Regulatory Guide 1.132, “Site Investigations for Foundations of 

Nuclear Power Plants” (Revision 2, October 2003) ................................. 28 

1.5.4 Regulatory Guide 1.136, “Design Limits, Loading Combinations, 

Materials, Construction, and Testing of Concrete Containments” 

(Revision 3, March 2007) ......................................................................... 28 

1.5.5 Regulatory Guide 1.138, “Laboratory Investigations of Soils and 

Rocks for Engineering Analysis and Design of Nuclear Power 

Plants”(December 2003 version) ............................................................. 29 

1.5.6 Regulatory Guide 1.142, “Safety-Related Concrete Structures for 

Nuclear Power Plants (Other than Reactor Vessels and 

Containments.)” (Revision 2, November 2001) ....................................... 30 
TABLE OF CONTENTS 

(continued) 

Section Page 

viii 

1.5.7 Regulatory Guide 1.198, “Procedures and Criteria for Assessing 

Seismic Soil Liquefaction at Nuclear Power Plant Sites” 

(November 2003 version) ........................................................................ 30 

1.5.8 DC/COL-ISG-17 “Interim Staff Guidance on Ensuring HazardConsistent Seismic Input for Site Response and Soil Structure 

Interaction Analyses” ............................................................................... 30 

1.5.9 SRP 2.5.2, “Vibratory Ground Motion” (March 2007 version) ................. 31 

1.5.10 SRP 2.5.4, “Stability of Subsurface Material and Foundations”(May 

2010 version) ........................................................................................... 31 

1.5.11 SRP 3.7.1 (“Seismic Design Parameters”), 3.7.2 (“Seismic System 

Analysis”), and 3.7.3 (“Seismic Subsystem Analysis”) (March 2007 

versions). ................................................................................................. 32 

1.5.12 SRP 3.8.3, “Concrete and Steel Internal Structures of Steel or 

Concrete Containments” (March 2007 version) ....................................... 32 

1.5.13 SRP 3.8.4, “Other Seismic Category I Structures” (March 2007 

version) .................................................................................................... 33 

1.5.14 SRP 3.8.5, “Foundations” (March 2007 version ) .................................... 33 

1.5.15 SRP 3.9.1, “Special Topics for Mechanical Components” 

(March 2007 version) ............................................................................... 34 

1.5.16 SRP 3.9.2, “Dynamic Testing and Analysis of Systems, Structures, 

and Components” (March 2007 version) ................................................. 34 

1.5.17 SRP 3.9.3, “ASME Code Class 1, 2, and 3 Components and 

Component Supports, and Core Support Structures” (March 2007 

version) .................................................................................................... 35 

1.5.18 SRP 3.9.4, “Control Rod Drive Systems” (March 2007 version) .............. 35 

1.6 Evaluation of Each Regulatory Document (from Table 1-3) for Which Important 

Changes May Be Needed .................................................................................... 36 

1.6.1 Regulatory Guide 1.29, “Seismic Design Classification” (March 2007 

version) .................................................................................................... 36 

1.6.2 Regulatory Guide 1.61, Damping Values for Design of Nuclear Power 

Plants” (March 2007 version) ................................................................... 36 

1.6.3 SRP 3.2.1, “Seismic Classification” (March 2007 version) ...................... 37 

1.6.4 SRP 3.8.1, “Concrete Containment” (March 2007 version) ..................... 37 

1.6.5 SRP 3.8.2, “Steel Containment” (March 2007 version) ........................... 38 

1.6.6 SRP 3.9.5, “Reactor Pressure Vessel Internals” (March 2007 version) .. 38 

1.7 Consensus Codes and Standards ....................................................................... 38 

1.8 Summary for Section 1 ........................................................................................ 39 

2. EVALUATION OF SEISMIC-STRUCTURAL SIMULATION TOOLS FOR 

APPLICABILITY TO SMALL MODULAR REACTORS .................................................... 41 

2.1 Introduction to Section 2 ...................................................................................... 41 

2.2 The Work – Two Phases ..................................................................................... 41 

2.2.1 The First Phase, Identification .................................................................. 41 
TABLE OF CONTENTS 

(continued) 

Section Page 

ix 

2.2.2 The Second Phase, Evaluation ............................................................... 43 

2.2.3 Broad Conclusion .................................................................................... 44 

2.2.4 Analysis of an SMR Adjacent to One or More Others ............................. 45 

2.2.5 Discussion of Embedment Issues ............................................................ 46 

2.2.6 Code by Code Evaluations ...................................................................... 46 

2.2.6.1 ABAQUS ............................................................................................ 47 

2.2.6.2 ADINA ................................................................................................ 48 

2.2.6.3 ALGOR ............................................................................................... 49 

2.2.6.4 ANSYS ............................................................................................... 49 

2.2.6.5 GT STRUDL ....................................................................................... 50 

2.2.6.6 LS-DYNA ............................................................................................ 52 

2.2.6.7 NASTRAN .......................................................................................... 53 

2.2.6.8 SAP2000 ............................................................................................ 53 

2.2.6.9 SASSI ................................................................................................. 54 

2.2.6.10 SHAKE91 .......................................................................................... 56 

2.2.6.11 SIMQKE-1 ......................................................................................... 56 

2.2.6.12 STARDYNE ...................................................................................... 57 

2.2.7 ESSI ........................................................................................................ 58 

2.3 Summary for Section 2 ........................................................................................ 59 

TABLES

Table Page 

1-1 Category One—Documents for Which No Changes Are Needed ...................................... 7 

1-2 Category Two—Documents for Which Modest Changes May Be Desired ..................... 12 

1-3 Category Three—Documents for Which Important Changes May Be Desired ............... 22 

2-1 List of Simulation Tools Evaluated .................................................................................. 43 

xi 

EXECUTIVE SUMMARY 

The existing NRC reactor-safety guidance on seismic-structural evaluations is based largely on

the regulation of large light water reactor (LWR) designs. As the NRC prepares to review small

modular reactor (SMR) designs of commercial units for the first time, it is important to assess

whether the existing guidance and review tools and standards are appropriate for the SMR

designs. 

Lawrence Berkeley National Laboratory (LBNL) reviewed the NRC guidance documents that 

have been used in previous NRC licensing reviews in seismic (including soil structure 

interaction) and structural areas to determine if the documents could be improved for use during 

review of an SMR application. In addition, LBNL reviewed various software packages to assess 

whether they had any inherent limitations that could adversely affect the results when used to 

evaluate an SMR design. 

This report has been written in two distinct sections. 

In Section 1, fifty-nine (59) documents covering various seismic-structural regulatory-guidance 

positions were reviewed. Of these, twenty-nine (29) are deemed not to need any improvements; 

twenty (20) were deemed to need minor or moderate improvements to clarify the NRC 

position; and ten (10) could benefit from more extensive improvements. 

An example of the type of change that was characterized by ‘minor or moderate’ was that in RG 

1.57, “Design Limits and Loading Combinations for Metal Primary Reactor Containment System 

Components,” the value for the load factor to be applied is specified as 1.10. This guidance 

should be improved to clarify that it is not overly conservative in an SMR design. As another 

example, RG 1.132, “Site Investigations for Foundations of Nuclear Power Plants,” specifies the 

spacing of borings at 30 meters, or an area of 900m2 (square meters). This guidance could be 

modified to specify the resolution needed to ensure appropriate characterization of 

the subsurface conditions, given the small foot print of an SMR. 

An example of a more extensive or important needed revision is for RG 1.29, “Seismic Design 

Classification.” The design classification system is tailored to LWR designs. Some of the 

classifications may not be correct for an SMR with its unique design features. A more intense 

review is required to fully explore this issue. Another example is in RG 1.61, “Damping Values 

for Seismic Design of Nuclear Power Plants.” The damping values listed may not be correct for 

the structure, size and mass of an SMR. 

In Section 2, thirteen (13) software packages were reviewed. All are deemed to yield acceptable 

results when used on an SMR design if it can be assumed that the user is properly trained 

for that package. However, a few specific concerns are identified for two of the software 

packages. 

The Department of Energy (DOE) reported in April 2011 that SASSI software for analyzing soil 

structure interaction effects could produce unrealistic earthquake responses in some analyses. 

The unrealistic results manifest for certain types of deeply embedded structures. This is a 

concern for some proposed SMR designs because they utilize deeply embedded structures. A 

solution is being pursued by a consortium of SASSI experts and practitioners. Any user of the 

SASSI program must address this issue when using the software. 
xii 

The ESSI software is new and uses a different approach than the other packages considered. 

Specifically it uses a time-domain, non-linear approach, instead of the traditional frequency 

domain. The review did not reveal any issues with the software. However, users must be aware 

of this change in modeling philosophy, and build the model accordingly. Given that it is a new 

package with a different approach, some users or design reviewers may not be confident of its 

results. 
xiii 

ACKNOWLEDGMENT

The authors wish to acknowledge the support of Thomas J. Herrity of the U.S. Nuclear

Regulatory Commission’s (NRC’s) Office of Nuclear Regulatory Research who served as the

technical contact on the NRC staff for this project under NRC job code V6013. 

Dr. Dimitrios Konstantinidis principally worked on the Section 1 evaluation, and Dr. Ziguang 

Zhou principally worked on the Section 2 evaluation. Dr. Konstantinidis is now on the civil 

engineering faculty at McMaster University, Hamilton, Ontario, Canada. Dr. Zhou is now at the 

College of Civil Engineering, Tongji University, Shanghai, China. 

This manuscript has been written by authors at the Lawrence Berkeley National Laboratory 

under Contract No. DE-AC02-05CH11231 with the U.S. Department of Energy (DOE). The 

U.S. Government retains, and the publisher, by accepting the article for publication, 

acknowledges, that the U.S. Government retains a non-exclusive, paid-up, irrevocable, 

worldwide license to publish or reproduce the published form of this manuscript, or allow others 

to do so, for U.S. Government purposes. This project was supported by the U.S. Nuclear 

Regulatory Commission under a Federal Interagency Agreement with DOE. While this 

document is believed to contain correct information, neither the U.S. Government nor any 

agency thereof, nor The Regents of the University of California, nor any of their employees, 

makes any warranty, express or implied, or assumes any legal responsibility for the accuracy, 

completeness, or usefulness of any information, apparatus, product, or process disclosed, or 

represents that its use would not infringe privately owned rights. Reference herein to any 

specific commercial product, process, or service by its trade name, trademark, manufacturer, or 

otherwise, does not necessarily constitute or imply its endorsement, recommendation, or 

favoring by the United States Government or any agency thereof, or The Regents of the 

University of California. The views and opinions of authors expressed herein do not necessarily 

state or reflect those of the United States Government or any agency thereof or The Regents of 

the University of California. Lawrence Berkeley National Laboratory is an equal opportunity 

employer. 

xv 

ABBREVIATIONS AND ACRONYMS

ANS American Nuclear Society 

ASCE American Society of Civil Engineers 

ASCII American Standard Code for Information Interchange (a computer format) 

ASME American Society of Mechanical Engineers 

BWR boiling-water reactor 

CFR U.S. Code of Federal Regulations

CQC Complete Quadratic Combination 

CRD control rod drive 

CRDS control rod drive system 

DNFSB U.S. Defense Nuclear Facilities Safety Board 

DOE U.S. Department of Energy 

ESSI Earthquake Soil Structure Interaction (software program) 

FEA finite element analysis 

FEM finite element method 

FNA finite nonlinear analysis 

FSI fluid-structure interaction 

GDC general design criterion 

HVAC heating, ventilation, and air conditioning 

Hz hertz, a unit of frequency (one cycle per second) 

ISG interim staff guidance 

JCNRM ASME-ANS Joint Committee on Nuclear Risk Management 

LBNL Lawrence Berkeley National Laboratory 

LWR light-water reactor 

NPP nuclear power plant 

NRC U.S. Nuclear Regulatory Commission 

NRO NRC Office of New Reactors 

OBE operating-basis earthquake 

PC personal computer 

PDE partial differential equation 

PRA probabilistic risk assessment 

PWR pressurized-water reactor 

RG NRC Regulatory Guide 

SDOF single degree of freedom 

SMR small modular reactor 

SRP NRC Standard Review Plan 

SRSS square root of the sum of the squares 

SSC structure, system, or component 

SSE safe-shutdown earthquake 

SSI soil-structure interaction 

V & V verification and validation 

1 

1. EVALUATION OF NRC SEISMIC-STRUCTURAL 

REGULATORY GUIDANCE FOR APPLICABILITY TO SMALL 

MODULAR REACTORS (SMRs)

1.1 Introduction

Lawrence Berkeley National Laboratory (LBNL) performed a project supported by the U.S. 

Nuclear Regulatory Commission (NRC). The project was entitled, “Soil Structure Interactions for 

Small Modular Reactors on Individual Foundations.” For the first part of the project, covered in 

this Section, LBNL formed a project team to perform two review and evaluation tasks. The 

scope of the review and evaluation was limited to NRC regulations, NRC regulatory guidance, 

and certain consensus codes and standards related to seismic issues. Specifically, the review 

assessed seismic issues related to structural engineering, geotechnical engineering, and other 

related engineering areas. 

Identification of Applicable NRC Regulations, Reg Guides. etc. 

In this Task, the project team identified and reviewed the currently issued NRC regulations, 

Regulatory Guides, Standard Review Plan sections, industry consensus standards, and other 

regulatory guidance that are relevant to the areas of seismic engineering, structural engineering, 

geotechnical engineering, and related topics. Each regulation or document was studied to 

determine how it had been used for large LWRs (light-water reactors) by industry designers and

analysts, and how it had been interpreted by the NRC regulatory staff. In parallel, aspects of 

NRC risk methodology specific to LWRs were identified. The list of regulations and documents 

identified as pertinent was compiled into this report. 

Evaluation of Applicability to Small Modular Reactors 

In this Task, the project team analyzed the regulatory guidance identified in the first Task for 

applicability to SMR (small modular reactor) design concepts. 

In the early stages of this project, the LBNL team (in conjunction with the NRC staff) concluded 

that identifying specific SMR designs was not necessary—that an evaluation could be 

performed that would be generically applicable to many of the different types of SMRs. 

However, this may or may not be true for all SMRs. 
2 

1.2 The Work—Three Phases

The first phase of the work reported here in Section 1 involved compiling a list of the relevant 

NRC regulations and regulatory guides; standard review plan (SRP) sections, etc.; and industry 

standards. The project team started with a list of NRC documents suggested by the NRC staff 

and then added other items to it based on the judgment of the team. 

The second phase of the work involved the examination and study of each document to

determine whether its content, applicability, and application in practice would be different if 

applied in NRC regulatory processes for an SMR rather than for a current-generation large lightwater reactor (LWR). The LBNL team categorized the documents into three categories. For a 

large fraction of the documents, the LBNL team concluded that there would be no difference. 

For this reason, the first category consists of documents for which no modification would be 

needed to accommodate an SMR. For a second category, the LBNL team concluded that the 

document would be fully applicable to an SMR in a technical sense; however, its efficiency and 

effectiveness for SMRs could be improved by a small number of modest changes. A third 

category of documents was identified for which effective use by an SMR would likely require 

important technical changes. This process resulted in three lists of documents for the three 

categories. 

The third phase of the work involved the detailed evaluation of each of the items in the second 

and third categories. 

1.3 List of Relevant Regulations, Regulatory Guides, ISGs, SRP

Sections, and Consensus Codes & Standards

1.3.1 NRC Regulations: General Design Criteria (Parts of 10 CFR 50, Appendix A)

These criteria are from Appendix A, “General Design Criteria for Nuclear Power Plants,” to Part 

50, “Domestic Licensing of Production and Utilization Facilities,” of Title 10, “Energy,” of the 

Code of Federal Regulations (10 CFR 50, Appendix A): 

 GDC 2 (General Design Criterion 2), “Design Bases for Protection Against Natural 

Phenomena” 

 GDC 4 (General Design Criterion 4) “Environmental and Dynamic Effects Design Basis” 

 GDC 5 (General Design Criterion 5), “Sharing of Structures, Systems, and Components” 

 GDC 16 (General Design Criterion 16), “Containment Design” 

 GDC 50 (General Design Criterion 50), “Containment Design Basis” 

 
3 

1.3.2 Specific NRC Regulations

 Appendix S to 10 CFR 50 

“Earthquake Engineering Criteria for Nuclear Power Plants” 

 10 CFR 100.23 

“Geologic and Seismic Siting Criteria” 

 Appendix A to 10 CFR 100 

“Seismic and Geologic Siting Criteria for Nuclear Power Plants” 

1.3.3 NRC Regulatory Guides*

 Regulatory Guide (RG) 1.12 (Rev. 2, Mar. 1997) 

“Nuclear Power Plant Instrumentation for Earthquakes” 

 RG 1.29 (Rev. 4, Mar. 2007) 

“Seismic Design Classification” 

 RG 1.57 (Rev. 1, Mar. 2007) 

“Design Limits and Loading Combinations for Metal Primary Reactor Containment 

System Components” 

 RG 1.60 (Rev. 1, Dec. 1973) 

“Design Response Spectra for Seismic Deign of Nuclear Power Plants” 

 RG 1.61 (Rev. 1, Mar. 2007) 

“Damping Values for Seismic Design of Nuclear Power Plants” 

 RG 1.92 (Rev. 2, July 2006) 

“Combining Modal Responses and Spatial Components in Seismic Response Analysis” 

 RG 1.100 (Rev. 3, Sept. 2009) 

“Seismic Qualification of Electrical and Active Mechanical Equipment and Functional 

Qualification of Active Mechanical Equipment for Nuclear Power Plants” 

 RG 1.122 (Rev. 1, Feb. 1978)

“Development of Floor Design Response Spectra for Seismic Design of Floor-Supported 

Equipment or Components” 

* Some of these NRC Regulatory Guides are not the very latest revisions but these are the versions that were 

current when the project began. 
4 

 RG 1.132 (Rev. 2, Oct. 2003) 

“Site Investigations for Foundations of Nuclear Power Plants” 

 RG 1.136 (Rev. 3, Mar. 2007)

“Design Limits, Loading Combinations, Materials, Construction, and Testing of Concrete 

Containments” 

 RG 1.138 (Rev. 2, Dec. 2003) 

“Laboratory Investigations of Soils and Rocks for Engineering Analysis and 

Design of Nuclear Power Plants” 

 RG 1.142 (Rev. 2, Nov. 2001) 

“Safety-Related Concrete Structures for Nuclear Power Plants (Other Than Reactor 

Vessels and Containments)”

 RG 1.166 (Mar. 1997) 

“Pre-Earthquake Planning and Immediate Nuclear Power Plant Operator PostEarthquake Actions” 

 RG 1.167 (Mar. 1997)

“Restart of a Nuclear Power Plant Shut Down by a Seismic Event” 

 RG 1.198 (Nov. 2003) 

“Procedures and Criteria for Assessing Seismic Soil Liquefaction at Nuclear Power Plant 

Sites” 

 RG 1.200 (Mar. 2009) 

“An Approach for Determining the Technical Adequacy of Probabilistic Risk Assessment

Results for Risk-Informed Activities”

 RG 1.208 (Mar. 2007) 

“A Performance-Based Approach to Define the Site-Specific Earthquake Ground Motion” 

1.3.4 NRC Interim Staff Guidance

 Design Certification (DC)/Combined License (COL)-ISG-1 (May 19, 2008) “Interim 

Staff Guidance on Seismic Issues Associated with High Frequency Ground Motion 

in Design Certification and Combined License Applications” 

 DC/COL-ISG-3 (June 11, 2008) 

“PRA Information to Support Design Certification and Combined License Applications” 

 DC/COL-ISG-17 (March 24, 2010)

“Interim Staff Guidance on Ensuring Hazard-Consistent Seismic Input for Site 

Response and Soil Structure Interaction Analyses” 
5 

 DC/COL-ISG-20 (March 15, 2010) 

“Seismic Margin Analysis for New Reactors Based on Probabilistic Risk Assessment”

1.3.5 NRC Standard Review Plan (SRP) Sections (NUREG-0800)

 SRP 2.5 

– 2.5.1 Basic Geologic and Seismic Information 

– 2.5.2 Vibratory Ground Motion 

– 2.5.3 Surface Faulting 

– 2.5.4 Stability of Subsurface Materials and Foundations 

– 2.5.5 Stability of Slopes

 SRP 3.2.1 

– 3.2.1 Seismic Classification 

 SRP 3.7

– 3.7.1 Seismic Design Parameters 

– 3.7.2 Seismic System Analysis 

– 3.7.3 Seismic Subsystem Analysis 

– 3.7.4 Seismic Instrumentation

 SRP 3.8

– 3.8.1 Concrete Containment 

– 3.8.2 Steel Containment 

– 3.8.3 Concrete and Steel Internal Structures of Steel or Concrete Containments 

– 3.8.4 Other Seismic Category I Structures 

– 3.8.5 Foundations 

 SRP 3.9 

– 3.9.1 Special Topics for Mechanical Components 

– 3.9.2 Dynamic Testing and Analysis of Systems, Structures, and Components 

– 3.9.3 ASME Code Class 1, 2, and 3 Components and Component Supports, and 

Core Support Structures 

– 3.9.4 Control Rod Drive Systems 

– 3.9.5 Reactor Pressure Vessel Internals 

– 3.9.6 Functional Design, Qualification, and Inservice Testing Programs for Pumps, 

Valves, and Dynamic Restraints 

– 3.9.7 Risk-Informed Inservice Testing 

– 3.9.8 Review of Risk-Informed Inservice Inspection of Piping 

 SRP 3.10 

– 3.10 Seismic and Dynamic Qualification of Mechanical and Electrical Equipment 

 SRP 19 

– 19.0 Probabilistic Risk Assessment and Severe Accident Evaluation for New 

Reactors 
6 

1.3.6 Consensus Codes and Standards

Note: These consensus codes and standards were selected for review because they are 

referred to often in various NRC regulatory guidance documents. In each case, this is the 

latest version of the code or standard referred to in the NRC documents. 

 American Society of Civil Engineers (ASCE) 4-98, “Seismic Analysis of

Safety-Related Nuclear Structures” (1998) 

 ASCE 43-05, “Seismic Design Criteria for Structures, Systems, and 

Components in Nuclear Facilities” (2005) 

 American Society of Mechanical Engineers (ASME)/American Nuclear 

Society (ANS) RA-Sa-2009, “Standard for Level 1/Large Early Release 

Frequency Probabilistic Risk Assessment for Nuclear Power Plant 

Applications” 

 ASME Boiler and Pressure Vessel Code (various sections relevant to 

seismic- structural issues) 

1.4 Categorization and Preliminary Evaluation

In this section, the list in Section 1.3 is subdivided into three categories. The three 

categories are “no change needed,” “modest changes may be desired,” and “important 

changes may be desired.” A rationale is provided for each categorization decision. 

1.4.1 Category One, No Changes Needed

The LBNL team’s evaluation concluded that a majority of the documents listed in Section 1.3 

require no changes to be applicable to a small modular reactor (SMR). The list of documents 

in this category is presented here as Table 1-1. Table 1-1 also contains the rationale for each 

item’s having been placed into this category. 

Two rationales that would place a document in Category One are either (i) the regulation or 

regulatory position (although directly related to the issue at hand) is technology-neutral vis-àvis the difference between a large LWR and a small modular reactor or (ii) the regulation or 

regulatory position is only peripherally related to this difference. [An example of the latter 

would be the regulatory positions related to which types of seismic strong-motion instruments 

need to be deployed. The requirements for these instruments are peripherally related to the 

subject and are unaffected by whether the reactor is an LWR or an SMR.] 
Table 1-1 Category One—Documents for Which No Changes Are Needed 

87

Category 

Short 

Descriptor 

Name Rationale for Categorization Observations/Comments/ 

Concerns 

NRC Regulations 

GDC 2 Earthquake Engineering Criteria 

for Nuclear Power Plants 

Technology-neutral 

GDC 4 Environmental and Dynamic 

Effects Design Basis 

Technology-neutral 

GDC 5 Sharing of Structures, Systems, 

and Components 

Technology-neutral 

GDC 16 Containment Design Technology-neutral GDC 50 Containment Design Basis Technology neutral 10 CFR 50, Appendix S 

Earthquake Engineering Criteria for Nuclear Power Plants 

Technology-neutral 

10 CFR 100.23 Geologic and Seismic Siting 

Criteria 

Technology-neutral 

10 CFR 100, Appendix A 

Seismic and Geologic Siting Criteria for Nuclear Power Plants 

Technology-neutral 
Table 1-1 Category One—Documents for Which No Changes Are Needed (continued) 

8

Category Short 

Descriptor 

Name Rationale for Categorization Observations/Comments/ 

Concerns

RegulatoryGuides

RG 1.12 NPP Instrumentation for 

Earthquakes 

Technology-neutral Peripherally related 

RG 1.60 Design Response Spectra for 

Seismic Design of Nuclear Power Plants 

Technology-neutral 

RG 1.92 Combining Modal Responses 

and Spatial Components in Seismic Response Analysis 

Technology-neutral Peripherally related 

The methods for response analysis seem to apply equally to any NPP. 

RG 1.100 Seismic Qualification of 

Electrical and Active Mechanical Equipment and Function Qualification of Active Mechanical Equipment for Nuclear Power Plants 

Technology-neutral Peripherally related 

The approaches for qualification of equipment seem to apply equally to any NPP. 

RG 1.166 Pre-Earthquake Planning and 

Immediate Nuclear Power Plant Operator Post-Earthquake Actions 

Technology-neutral Peripherally related 

RG 1.167 Restart of a Nuclear Power 

Plant Shut Down by a Seismic Event 

Technology-neutral Peripherally related 

RG 1.200 An Approach for Determining 

the Technical Adequacy of Probabilistic Risk Assessment Results for Risk-Informed Activities 

Technology-neutral Peripherally related 

RG 1.208 A Performance-Based Approach 

to Define the Site-Specific Earthquake Ground Motion 

Technology-neutral Peripherally related 
Table 1-1 Category One—Documents for Which No Changes Are Needed (continued) 

109

Category Short 

Descriptor 

Name Rationale for Categorization Rationale for Categorization 

NRO Interim Staff Guidance 

DC/COL-ISG-1 Interim Staff Guidance on 

Seismic Issues Associated with High-Frequency Ground Motion in Design Certification and Combined License Applications 

Technology-neutral 

DC/COL-ISG-3 PRA Information to Support 

Design Certification and Combined License Applications 

Technology-neutral 

DC/COL-ISG-20 Seismic Margin Analysis for 

New Reactors Based on Probabilistic Risk Assessment 

Technology-neutral 

NUREG-0800 Standard Review Plan (SRP) Sections 

SRP 2.5.1 Basic Geologic and Seismic 

Information 

Technology-neutral 

SRP 2.5.3 Surface Faulting Technology-neutral Peripherally related SRP 2.5.5 Stability of Slopes Technology-neutral Peripherally related SRP 3.7.4 Seismic Instrumentation Technology-neutral Peripherally related SRP 3.9.3 ASME Code Class 1, 2, and 3 

Components and Component Supports and Core Support Structures 

Technology-neutral 

SRP 3.9.6 Functional Design, Qualification, 

and Inservice Testing Programs for Pumps, Valves, and Dynamic Restraints 

Technology-neutral Peripherally related 

SRP 3.9.7 Risk-Informed Inservice Testing Technology-neutral Peripherally related SRP 3.9.8 Review of Risk-Informed In 

service Inspection of Piping 

Technology-neutral Peripherally related 
Table 1-1 Category One—Documents for Which No Changes Are Needed (continued) 

1110

Category Short 

Descriptor 

Name Rationale for Categorization Rationale for Categorization

NUREG 0800 Standard Review Plan (SRP) Sections 

SRP 3.10 Seismic and Dynamic 

Qualification of Mechanical and Electrical Equipment 

Technology-neutral Peripherally related 

Continued) SRP 19.0 Probabilistic Risk Assessment 

and Severe Accident Evaluation for New Reactors 

Technology-neutral Peripherally related 
11 

1.4.2 Category Two, Modest Changes May Be Desired

The LBNL team’s evaluation concluded that a small number of the documents may require 

some modest changes so they can be used in the NRC regulatory process for an SMR. The list 

of documents in this category is in Table 1-2. Table 1-2 also contains the rationale for each 

item’s having been placed into this category. 

The entries in Table 1-2 include the following NRC documents: 

RG 1.57 

RG 1.122 

RG 1.132 

RG 1.136 

RG 1.138 

RG 1.142 

RG 1.198 

DC/COL-ISG-17 

SRP 2.5.2 

SRP 2.5.4 

SRP 3.7.1 

SRP 3.7.2 

SRP 3.7.3 

SRP 3.8.3 

SRP 3.8.4 

SRP 3.8.5 

SRP 3.9.1 

SRP 3.9.2 

SRP 3.9.3 

SRP 3.9.4 

NOTE: “RG” is a “Regulatory Guide” and “SRP” is a “Standard Review Plan Section.” 
Table 1-2 Category Two—Documents for Which Modest Changes May Be Desired

12

Category Short 

Descriptor 

Name Rationale for 

Categorization 

Observations/Comments/ Concerns

NRC Regulations 

None Regulatory Guides 

Regulatory Guides 

RG 1.57 (see Section 1.5.1 for additional discussion) 

Design Limits and Loading Combinations for Metal Primary Reactor Containment System Components 

Technology-neutral 

(1) The methods for response analysis seem to apply equally to any NPP. (2) The relevance of these load combinations to any specific SMR needs to be checked by both the designer and the NRC. Also, the relevance of the factor of 1.10 for Pg3 in 1.2.3.(6) needs to be determined for SMRs. 

RG 1.122 (see Section 1.5.2 for additional discussion) 

Development of Floor Design Response Spectra for Seismic Design of Floor-Supported Equipment or Components 

The RG’s guidance on development of floor design response spectra may not be fully applicable to a structure like an SMR with its significantly smaller size and mass. However, any changes in the guidance are likely to be modest. 

The RG asks for the use of the square root of the sum of the squares (SRSS) to combine floor spectral ordinates (B.2). It appears that this provision was written with a specific piece of equipment in mind that behaves like a system with a single degree of freedom. It ignores structure-equipment interaction and is not generic enough to encompass pieces of equipment with more complex dynamic behavior. Moreover, the use of the SRSS combination rule may not be appropriate if the equipment in question exhibits closely spaced modal frequencies. This is probably because the RG was written before more recent (e.g., Complete Quadratic Combination) modal combination rules that incorporate correlation coefficients were developed. 
Table 1-2 Category Two—Documents for Which Modest Changes May Be Desired (continued)

13

Category Short 

Descriptor 

Name Rationale for 

Categorization 

Observations/Comments/ Concerns 

Regulatory Guides (continued) 

RG 1.132(see Section 1.5.3 for additional discussion) 

Site Investigations for Foundations of Nuclear Power Plants 

The issues of spacing between borings, minimum depth of penetration of borings, minimum percentage of borings reaching the needed depth, and the extent of subsurface exploration. 

Appendix D (Spacing and Depth of Subsurface Explorations and Safety-Related Foundations) calls for 30 m (or area of 900 m2) between borings under “larger, heavier structures, such as the containment and auxiliary buildings.” This spacing may be too large for SMRs with a small footprint. A smaller boring spacing may be necessary to characterize the subsurface profile. A second concern involves the requirement in Appendix D for boring to a minimum depth of penetration (33 feet below the foundation.) For an SMR that will be deeply or fully embedded, this boring-depth requirement would need to be reevaluated on a case-by-case basis. Additional concerns are the minimum percentage of borings that would be required to reach the maximum required depth and the extent of subsurface exploration that needs to be accomplished to provide reasonable coverage for understanding subsurface stability and for understanding the three-dimensional distribution of geological features. 

RG 1.136 (see Section 1.5.4 for additional discussion)

Design Limits, Loading Combinations, Materials, Construction, and Testing of Concrete Containments 

The issue of load combinations. 

As in RG 1.57, the relevance of these load combinations to any specific SMR needs to be checked by both the designer and the NRC. Also, in C.5.B(3), the relevance to any specific SMR of the 310-kPa pressure load would need to be checked. 
Table 1-2 Category Two—Documents for Which Modest Changes May Be Desired (continued)

14

Category Short 

Descriptor 

Name Rationale for 

Categorization 

Observations/Comments/ Concerns 

Regulatory Guides (continued)

RG 1.138 (see Section 1.5.5 for additional discussion)

Laboratory Investigations of Soils and Rocks for Engineering Analysis and Design of Nuclear Power Plants 

The text of this RG seems to be quite generic, but its applicability to an SMR design that is deeply embedded may not be as good a fit as it is for a large LWR to be sited near the surface. 

The issue that might require special evaluation is when an SMR design is deeply embedded. This is because the laboratory testing program in RG 1.138 must “work together” with the field sample-taking program usually accomplished under guidance described in other RGs. The sampling program could be different in important ways. 

RG 1.142 (see Section 1.5.6 for additional discussion)

Safety-Related Concrete Structures for Nuclear Power Plants (Other than Reactor Vessels and Containments) 

The issue of applicability of compressive strength test. 

(1) Although the text of this RG refers to certain attributes specific to large LWRs, none of the text is constraining in any way. (2) According to Regulatory Position 5, the frequency for in-process compressive strength tests of concrete is to be 1 test per 100 cu yd. However, the effect of variability in concrete strength may be higher as the size of the structure decreases. Consequently, for an SMR, the testing frequency may need to be higher. 

RG 1.198 (see Section 1.5.7 for additional discussion)

Procedures and Criteria for Assessing Seismic Soil Liquefaction at Nuclear Power Plant Sites 

The text of this RG seems to be quite generic, but its applicability to an SMR design that is deeply embedded may not be as good a fit as it is for a large LWR to be sited near the surface. 

For a deeply embedded SMR, the way liquefaction phenomena might affect the structure could be quite different if the liquefaction layer was close to the bottom of the embedded structure, and all the more so if the layer was located above the bottom of the embedded structure. 
Table 1-2 Category Two—Documents for Which Modest Changes May Be Desired (continued)

15

Category Short 

Descriptor 

Name Rationale for 

Categorization 

Observations/Comments/ Concerns 

NRO Interim Staff Guidance 

DC/COL-ISG-17 (see Section 1.5.8 for additional information) 

Interim Staff Guidance on Ensuring Hazard-Consistent Seismic Input for Site Response and Soil Structure Interaction Analyses 

This ISG seems to be mostly generic and applicable to any site. However, the number of check points called for in ISG-17, and perhaps other aspects of the analysis, may not be applicable to a deeply embedded SMR. 

For a deeply embedded SMR, the way ISG-17 suggests that an applicant do this analysis should ensure the development of a consistent seismic input for response and soil-structure interaction (SSI) analyses. The input motions at the foundation level, when convolved up to through the soil column, must bound the free-field performance-based surface response spectrum (PBRS) at the surface. For deeply embedded structures, the number and location of check points may need to be different than those required for a surface-sited large LWR. In particular, for deeply embedded SMR structures, it may be necessary to develop additional PBRS spectra at intermediate depths. 

NUREG-0800 Standard Review Plan (SRP) Sections 

SRP 2.5.2 (see Section 1.5.9 for additional discussion)

Vibratory Ground Motion 

The issue of inclined shear-wave propagation being more significant for deeply embedded SMRs 

For a deeply embedded SMR, the way an inclined seismic shear wave propagates (the vertical and horizontal components) may be more important for a deeply embedded SMR than for a large LWR at or near the surface, and the analysis method must account for this properly. Specifically, for a deeply embedded SMR, the effect of inclined waves may be more important and the method for determining the GMRS needs to be carefully considered. 
Table 1-2 Category Two—Documents for Which Modest Changes May Be Desired (continued)

16

Category Short 

Descriptor 

Name Rationale for 

Categorization 

Observations/Comments/ Concerns 

NUREG-0800 Standard Review Plan (SRP) Sections (continued) 

SRP 2.5.4 (see Section 1.5.10 for additional discussion)

Stability of Subsurface Material and Foundations 

For a deeply embedded SMR, the following issues need to be addressed: (1) the construction of the deep excavation, (2) the effect of dewatering, and (3) the adequacy of measuring points to monitor settlement. 

For a deeply embedded SMR, the following issues need to be addressed in a way potentially different from how they would be handled for a large LWR at or near the surface: (1) The construction of the deep excavation may affect the surrounding soil properties that are used in the analysis and design of the foundation and plant structures. (2) The effect of dewatering, both during and after construction, considering the higher head and volume of ground water, may be more significant to the structures than its effect for LWRs. (3) Adequate measuring points to monitor settlement throughout the depth of the embedded structure may be needed. 

SRP 3.7.1 SRP 3.7.2 SRP 3.7.3 (see Section 1.5.11 for additional discussion)

Seismic Design Parameters Seismic System Analysis Seismic Subsystem Analysis 

These three SRP sections seem to be mostly generic and applicable to any site. However, some aspects of them may not be applicable to a deeply embedded SMR. 

For a deeply embedded SMR, the guidance in these SRP sections may not be directly applicable. In particular, the development of a consistent seismic input for response and soil structure interaction (SSI) analyses and then for design of a specific structure, system, or component (SSC) can be different than for a large LWR on or near the surface. A number of issues require reevaluation, and the application of these SRP sections without such a reevaluation could lead to a compromise in the design margins. One issue is that the way the soil column interacts with a deeply embedded structure can be quite different, which affects how the seismic energy propagates further into the structure. Design using this type of input, if inappropriate, can then lead to incorrect design solutions. These SRP sections are concerned with design parameters and also with analysis methods. The detailed guidance about analysis methods in SRP sections 3.7.2 and 3.7.3 may also need to be reevaluated for a deeply embedded SMR. 
Table 1-2 Category Two—Documents for Which Modest Changes May Be Desired (continued)

17

Category Short 

Descriptor 

Name Rationale for 

Categorization 

Observations/Comments/ Concerns 

NUREG-0800 Standard Review Plan (SRP) Sections (continued) 

SRP 3.8.3 (see Section 1.5.12 for additional discussion)

Concrete and Steel Internal Structures of Steel or Concrete Containments 

This SRP section specifically calls out certain features of LWR containments that may or may not be relevant to SMRs, which are likely to have internals with significantly smaller size and mass. However, any changes to the SRP section are likely to be modest. 

SRP deals extensively with reactors of different scales and likely different features (pressurized-water reactors [PWRs] and boiling-water reactors [BWRs]). 
Table 1-2 Category Two—Documents for Which Modest Changes May Be Desired (continued)

18

Category Short 

Descriptor 

Name Rationale for 

Categorization 

Observations/Comments/ Concerns 

NUREG-0800 Standard Review Plan (SRP) Sections (continued) 

SRP 3.8.4 (see Section 1.5.13 for additional discussion)

Other Seismic Category I Structures 

This SRP section seems to have broad applicability to SMRs but, without careful review, a judgment cannot be supported. The text has much that is specific to LWRs but also has sections that can apply broadly to “other” structures. Perhaps more specificity for SMRs is needed. However, any changes to the SRP section are likely to be modest. 

Load combinations are given that may have been derived with specific designs in mind. Moreover, the SRP calls for use of damping ratios from tables in RG 1.61 that are not applicable for base-isolated designs (see evaluation of RG 1.61 in Table 3 for more details). 

SRP 3.8.5 (see Section 1.5.14 for additional discussion) 

Foundations The treatment of 

relationships between adjacent structures may not be generic. 

The relevance of certain foundation issues needs to be determined for any specific SMR design. Also, computer codes will need to be assessed. 
Table 1-2 Category Two—Documents for Which Modest Changes May Be Desired (continued)

19

Category Short 

Descriptor 

Name Rationale for 

Categorization 

Observations/Comments/ Concerns 

NUREG-0800 Standard Review Plan (SRP) Sections (continued) 

SRP 3.9.1 (see Section 1.5.15 for additional discussion) 

Special Topics for Mechanical Components 

Peripherally related, mostly technology-neutral 

Some of the discussion of the SRP review of core supports and reactor internals may not be fully technology neutral. See Section 1.5.15 for a further discussion. 

SRP 3.9.2 (see Section 1.5.16 for additional discussion) 

Dynamic Testing and Analysis of Systems, Structures, and Components 

This SRP section seems to have broad applicability to SMRs but, without careful review, a judgment cannot be supported. However, any changes to the SRP section are likely to be modest. 

SRP 3.9.3 (see Section 1.5.17 for additional discussion)

ASME Code Class 1, 2, and 3 Components and Component Supports, and Core Support Structures 

The treatment of core supports may not be generic. 
Table 1-2 Category Two—Documents for Which Modest Changes May Be Desired (continued)

20

Category Short 

Descriptor 

Name Rationale for 

Categorization 

Observations/Comments/ Concerns 

NUREG 0800 Standard Review Plan (SRP) Sections (continued) 

SRP 3.9.4 (see Section 1.5.18 for additional discussion) 

Control Rod Drive Systems 

The treatment of hydraulic vs. electromagnetic CRD systems vs. other possible systems may not be generic. 

Consensus Codes and Standards 

None 
21 

1.4.3 Category Three, Important Changes May Be Desired

The LBNL team’s evaluation concluded that a number of the documents may require some 

important changes in order that they could be used in the NRC regulatory process for an SMR 

(small modular reactor). The list of documents in this category is in Table 1-3. Table 1-3 also 

contains the rationale for each item’s having been placed into this category. 

The entries in Table 1-3 include the following NRC documents: 

RG 1.29 

RG 1.61 

SRP 3.2.1 

SRP 3.8.1 

SRP 3.8.2 

SRP 3.9.5 

NOTE: “RG” is a “Regulatory Guide” and “SRP” is a “Standard Review Plan Section.” 
Table 1-3 Category Three—Documents for Which Important Changes May Be Desired

22

Category Short 

descriptor

Name Rationale for categorization Observations/Comments/

Concerns

NRC Regulations

None

Regulatory Guides

RG 1.29(see Section 1.6.1 for additional discussion)

Seismic Design Classification

The list of SSCs identified in Section C, “Regulatory Position,” of this RG may not be inclusive enough to deal with all of the SSCs in proposed SMRs, with their significantly smaller size and mass and different types of SSCs. Without further study, it is not clear whether the changes would be major or only modest. 

RG appears to be technology-specific and applies primarily to LWRs and structures of similar scale.

RG 1.61 (see Section 1.6.2 for additional discussion)

Damping Values for Design of Nuclear Power Plants

It is not entirely obvious that the guidance on damping values applies to all of the constituent parts of an SMR with its significantly smaller size and mass. Without further study, it is not clear whether the changes would be major or only modest.

For base-isolated structures, the typical equivalent damping ratio could be as high as 30 percent or more. The values listed in Tables 1 and 2 for SSE and operating-basis earthquake are very low in comparison. Such restrictive regulation could likely discourage the use of innovative earthquake-protection technologies that adopt high damping to suppress displacements. 
Table 1-3 Category Three—Documents for Which Important Changes May Be Desired (continued)

23

Category Short 

descriptor

Name Rationale for categorization Observations/Comments/

Concerns

NRO Interim Staff Guidance 

None 

NUREG-0800 Standard Review Plan (SRP) Sections 

SRP 3.2.1 (see Section 1.6.3 for additional discussion)

Seismic Classification 

This SPR section specifically calls out certain features of LWRs that may or may not be relevant to SMRs. It also refers in important places to RG 1.29, which itself may not be fully adequate for SMRs. Without further study, it is not clear whether the changes to this SRP section would be major or only modest. 

Numerous references are made to RG 1.29, which deals primarily with LWRs. 

SRP 3.8.1 (see Section 1.6.4 for additional discussion)

Concrete Containment 

This SRP section specifically calls out certain features of LWR containments that may or may not be relevant to SMRs. Without further study, it is not clear whether the changes to this SRP section would be major or only modest.

The concern is frequent references to RG 1.136 where load combinations with unclear origins are cited. These load combinations may have been derived for LWRs. 

SRP 3.8.2 (see Section 1.6.5 for additional discussion)

Steel Containment This SRP section specifically calls out 

certain features of LWR containments that may or may not be relevant to SMRs. Without further study, it is not clear whether the changes to this SRP section would be major or only modest.

The concern is constant reference to RG 1.57 where load combinations with unclear origins are cited. These load combinations may have been derived for LWRs. 
Table 1-3 Category Three—Documents for Which Important Changes May Be Desired (continued)

24

Category Short 

descriptor

Name Rationale for categorization Observations/Comments/

Concerns

NUREG-0800 Standard Review Plan (SRP) Sections (continued)

SRP 3.9.5 (see Section 1.6.6 for additional discussion) 

Reactor Pressure Vessel Internals 

This SRP section specifically calls out certain features of reactor “internals” that may or may not be relevant to SMRs. Without further study, it is not clear whether the changes to this SRP section would be major or only modest.

Consensus Codes and Standards (see Section 1.7 for additional discussion) 

ASCE 4-98 Seismic Analysis of 

Safety-Related Nuclear Structures 

This standard’s design criteria were developed with large LWRs specifically in mind. It probably applies directly to SMRs, but a careful review would be needed to determine this. 

ASCE 43-05 Seismic Design 

Criteria for Structures, Systems, and Components in Nuclear Facilities 

This standard’s design criteria were developed with large LWRs specifically in mind. It probably applies directly to SMRs, but a careful review would be needed to determine this. 
Table 1-3 Category Three—Documents for Which Important Changes May Be Desired (continued)

25

Category Short 

descriptor

Name Rationale for categorization Observations/Comments/

Concerns

Consensus Codes and Standards (continued)

ASME-ANS RA-Sa 

Standard for Level 1/Large Early Release Frequency Probabilistic Risk Assessment for Nuclear Power Plant Applications 

This probabilistic risk assessment (PRA) methodology standard was written to address large operating LWRs. The ASME-ANS Joint Committee on Nuclear Risk Management (JCNRM), which revises and maintains the PRA standards, is currently considering changes that would address this issue of the applicability of their current PRA standard(s) to SMRs. It is possible that the JCNRM may support some changes in the future along these lines. 

ASME B&PV code 

Boiler and Pressure Vessel Code 

This entire complex set of codes would need to be examined with SMRs in mind. Review of the ASME BPVC was determined to be outside the scope of this project. 
26 

1.5 Evaluation of Each Regulatory Document (from Table 1-2) for

Which Modest Changes May Be Desired

1.5.1 Regulatory Guide 1.57, “Design Limits and Loading Combinations for 

Metal Primary Reactor Containment System Components” (Revision 1, 

March 2007)

Evaluation of the applicability to SMRs on individual foundations 

Positive findings: 

Most of the guidance in Regulatory Guide 1.57 seems broadly applicable to any type or size of 

power reactor. It is mostly technology-neutral. Specifically: 

 The methods for response analysis seem to apply equally to any NPP. 

 The design limits and the supporting rationale seem to apply equally to any NPP. 

 The load-combination requirements seem to be technology-neutral. 

Concerns: 

(1) The RG text itself contains a warning in the first paragraph of the “Background” (Section 

B, page 3), as follows: 

However, the existing industry codes and standards are based on the

current class of light-water reactors and, as such, may not adequately

address design and construction features of the next generation of

advanced reactors. 

One paragraph later, the text says as an additional warning: 

While this regulatory guide is only directly applicable to light-water reactor

metal containments, the principles may be applied to non-light water

reactor containments, subject to review by the NRC. 

Moreover, a few specific provisions do not appear to be technology-neutral or at least will 

require the NRC staff’s further evaluation to determine this. 

(2) A sentence in the eighth paragraph under “Background” (page 4) states: 

The effects of natural phenomena other than earthquakes, such as

tornadoes, hurricanes, and floods, are not considered in this guide,

because a Category I concrete shield building typically protects the steel

containment from the effects of tornadoes, hurricanes, and floods

occurring outside the shield building. 

 
27 

This sentence contains the inference that a steel containment covered by this RG is 

contemplated as “typically” having a surrounding “concrete shield building.” This is clearly 

not technology-neutral, and the entire issue will need to be revisited if an SMR design has a 

different overall containment design. Therefore, the NRC should consider revising this 

section to make it applicable to all potential SMR designs. 

(3) The following load-combination provisions are for loads arising from metal-water 

reactions: 

(a) Concerning gas loads, the provision in section 1.2.3.1(6) is for pressure testing of a

containment with carbon-dioxide inerting. The equation therein contains a factor of1.10 

for the load combination that includes Pg 3 (the pressure from inerting) when pressure 

testing is conducted. Regulatory Guide 1.7 is referred to for Pg 3. For the much smaller 

containment of a typical SMR, it is not clear whether this provision including the factor of 

1.10 should apply or would need to be revisited. 

(b) Concerning the loads arising from a post-accident hydrogen control system, combined 

with normal gas loads, the load-combination provision in section 1.2.3.1(5) that includes 

Pg 3 again would need to be revisited if such a system were to be part of the design of 

an SMR. 

For both of these issues (a) and (b), if review confirms that the issue is important, then the 

issue could be addressed either by revising the section technically or by including wording 

that notes a case-by-case review is appropriate if an SMR design is under review. 

1.5.2 Regulatory Guide 1.122, “Development of Floor Design Response 

Spectra for Seismic Design of Floor-Supported Equipment or 

Components” (Revision 1, 1978)

Evaluation of the applicability to SMRs on individual foundations 

Positive findings: 

The guidance in the RG seems mostly to be broadly applicable to any type or size of power 

reactor. It is mostly technology-neutral. 

Concerns: 

One concern is that it is not entirely obvious that the RG’s guidance on development of floor 

design response spectra applies to a structure like an SMR with its significantly smaller size 

and mass. The NRC should review this technical issue and consider revising the SRP section, 

if appropriate. However, any changes in the guidance are likely to be modest. 

The RG text (Section B.2, page 2) asks for the use of the square root of sum of squares method 

(SRSS method) to combine floor spectral ordinates. It appears that this provision was written 

with a specific piece of equipment in mind that behaves like a single degree of freedom system 

within a much larger structure. It ignores structure-equipment interaction and may not be 

generic enough to encompass pieces of equipment with more complex dynamic behavior. Also, 

the use of the SRSS combination rule may not be appropriate if the equipment in question 

exhibits closely spaced modal frequencies. This is probably because the RG was written 

 
28 

before the development of more recent modal combination rules (e.g., complete quadratic 

combination or CQC) that incorporate correlation coefficients. 

Whether this concern is important for floor spectra calculated for a much smaller SMR structure 

is at least worthy of investigation. The NRC should review this technical issue and consider 

revising the SRP section technically, if appropriate, or by including wording that notes that a 

case-by-case review is appropriate if an SMR design is under review. On balance, any required 

changes to make the SRP text technology-neutral are likely to be modest. 

1.5.3 Regulatory Guide 1.132, “Site Investigations for Foundations of

Nuclear Power Plants” (Revision 2, October 2003)

Evaluation of the applicability to SMRs on individual foundations 

Positive findings: 

Most of the guidance in the regulatory guide seems broadly applicable to any type or size of 

power reactor. It is mostly technology-neutral. 

Concerns: 

One concern involves the spacing between borings called for in the text. Specifically, Appendix 

D (“Spacing and Depth of Subsurface Explorations and Safety-Related Foundations”) calls for 

30 m (or an area of 900 m2

) between borings under “larger, heavier structures, such as the 

containment and auxiliary buildings.” This spacing may be too large for SMRs with a small 

footprint. A smaller boring spacing may be necessary to characterize the subsurface profile, 

especially if the site is heterogeneous. 

Whether this is a concern is not clear, and may require case-by-case evaluation for any specific 

SMR design to determine if the SRP section is applicable without modification. 

A second concern involves the requirement in Appendix D of RG 1.132, “Spacing and Depth of 

Subsurface Explorations for Safety-Related Foundations,” for boring to a minimum depth of 

penetration (33 feet below the foundation). For an SMR that will be deeply or fully embedded, 

this boring-depth requirement would need to be reevaluated on a case-by-case basis. 

Additional concerns are the minimum percentage of borings that would be required to reach the 

maximum required depth, and the extent of subsurface exploration that needs to be 

accomplished, to provide reasonable coverage for understanding subsurface stability and for 

understanding the three-dimensional distribution of geological features. 

1.5.4 Regulatory Guide 1.136, “Design Limits, Loading Combinations,

Materials, Construction, and Testing of Concrete Containments”

(Revision 3, March 2007)

Evaluation of the applicability to SMRs on individual foundations 

Positive findings: 

Most of the guidance in the regulatory guide seems broadly applicable to any type or size of 

power reactor. It is mostly technology-neutral. 
29 

Concerns: 

(1) In section C.5.B(3), the relevance to any specific SMR of the 310 kPa pressure load 

as a potential challenge to the structure would need to be checked. This is especially 

true if the SMR design uses a different coolant (e.g., gas or liquid metal) or a different 

fuel so that zirconium-water reactions as a driver of post-accident internal pressure 

would not be the concern. 

(2) As discussed just above (Section 1.5.1) for RG 1.57, the relevance of some load 

combinations to any specific SMR needs to be checked. The discussion under RG 

1.57 explains the issue. That discussion is repeated here for clarity in italics as 

follows (copied from above): 

There are some load-combination provisions for loads arising from metalwater reactions. 

a) Concerning gas loads, the provision in section 1.2.3.1(6) is for pressure testing 

of a containment with carbon-dioxide inerting. The equation therein contains a 

factor of 1.10 for the load combination that includes Pg3 (the pressure from 

inerting), when pressure testing is conducted. Regulatory Guide 1.7 is referred 

to for Pg3. For the much smaller containment of a typical SMR, whether this 

provision including the factor of 1.10 should apply is not clear and would need to 

be revisited. 

b) Concerning the loads arising from a post-accident hydrogen control system,

combined with normal gas loads, the load-combination provision in section

1.2.3.1(5) that includes Pg3 again would need to be revisited if such a system

were to be part of the design of an SMR. 

1.5.5 Regulatory Guide 1.138, “Laboratory Investigations of Soils and Rocks 

for Engineering Analysis and Design of Nuclear Power Plants” 

(December 2003 version) 

Evaluation of the applicability to SMRs on individual foundations 

Positive findings: 

The text of this regulatory guide seems to be quite generic, involving as it does guidance on 

laboratory testing of soils and rocks retrieved from a field site. 

Concerns: 

The issue that might require special evaluation is when an SMR design is deeply embedded. 

This is because the laboratory testing program in RG 1.138, “Laboratory Investigations of Soils 

and Rocks for Engineering Analysis and Design of Nuclear Power Plants,” must “work together” 

with the field sample-taking program usually accomplished under guidance described in other 

RGs. The sampling program would be different in important ways for a deeply embedded 

structure because the coverage of the required samples could usually be quite different. This 

may mean that blindly following this RG “as if” this were a large LWR near the surface could 

lead to incorrect insights. 

 
30 

1.5.6 Regulatory Guide 1.142, “Safety-Related Concrete Structures for 

Nuclear Power Plants (Other than Reactor Vessels and Containments.)” 

(Revision 2, November 2001)

Evaluation of the applicability to SMRs on individual foundations 

Positive findings: 

Although the text of this regulatory guide refers to certain attributes specific to large LWRs, 

none of the text is constraining in any way. 

Concerns: 

According to Regulatory Position 5, the frequency for in-process compressive strength tests of 

concrete is to be one test per 100 cubic yards. However, the effect of variability in concrete 

strength may be higher for smaller SMR structures than it would be for a large LWR. 

Consequently, for an SMR, the testing frequency may need to be higher on a case-by-case 

basis. The guidance on sampling and testing frequencies in the American Concrete Institute 

standard ACI-349 may be applicable in such cases. 

1.5.7 Regulatory Guide 1.198, “Procedures and Criteria for Assessing

Seismic Soil Liquefaction at Nuclear Power Plant Sites” (November 

2003 version) 

Evaluation of the applicability to SMRs on individual foundations 

Positive findings: 

The regulatory guide is concerned with liquefaction, and most of the guidance (perhaps all of it) 

seems to be generic and applicable to any site. 

Concerns: 

For a deeply-embedded SMR, the way liquefaction phenomena might affect the structure could 

be quite different if the liquefaction layer was close to the bottom of the embedded structure and 

all the more so if the layer was located above the bottom of the embedded structure. This 

means that following the guidance in this regulatory guide might not cover fully all of the issue(s) 

that might affect the structure vis-à-vis liquefaction. 

1.5.8 DC/COL-ISG-17 “Interim Staff Guidance on Ensuring Hazard-Consistent 

Seismic Input for Site Response and Soil Structure Interaction 

Analyses”

Evaluation of the applicability to SMRs on individual foundations 

Positive findings: 

This interim staff guidance (ISG) is concerned with hazard-consistent seismic input, and most of 

the guidance (perhaps all of it) seems to be generic and applicable to any site. 

Concerns: 

For a deeply-embedded SMR, the way ISG-17 suggests that an applicant do this analysis 

should ensure the development of a consistent seismic input for response and soil structure 

interaction (SSI) analyses. The input motions at the foundation level, when convolved up to 

through the soil column, must bound the free-field performance-based surface response 
31 

spectrum (PBRS) at the surface. The surface PBRS at the surface provides a means for 

checking the adequacy of input motions at the foundation as well as the three deterministic soil 

columns. For deeply embedded structures, the number and location of check points may need 

to be different than those required for a surface-sited large LWR. In particular, for deeplyembedded SMR structures, it may be necessary to develop the PBRS at intermediate depths as 

well to have these available to check that the deterministic soil columns used for SSI analyses 

meet the required goal. 

1.5.9 SRP 2.5.2, “Vibratory Ground Motion” (March 2007 version) 

Evaluation of the applicability to SMRs on individual foundations 

Positive findings: 

The SRP section is concerned with developing vibratory ground motions to be used in the 

design and the safety analysis. Most of this SRP section would be applicable directly for an 

SMR. 

Concerns: 

The way an inclined seismic shear wave (both the vertical and horizontal components) 

propagates may be more important for a deeply-embedded SMR than for a large LWR at or 

near the surface, and the analysis method must account for this properly. SRP section 2.5.2.5 

states, in part, “Where vertically propagating shear waves may produce the maximum ground 

motion, a one-dimensional equivalent-linear analysis or nonlinear analysis may be appropriate 

and is reviewed in conjunction with geotechnical and structural engineering. However, site 

characteristics (such as a dipping bedrock surface, topographic effects or other impedance 

boundaries) may require that the analyses are also able to account for inclined waves.” This 

leads to the caveat that for a deeply embedded SMR, the effect of inclined seismic waves may 

be more important, and the method for determining the ground motion response spectrum 

(GMRS) needs to be carefully considered. 

1.5.10 SRP 2.5.4, “Stability of Subsurface Material and Foundations” (May 

2010 version)

Evaluation of the applicability to SMRs on individual foundations 

Positive findings: 

The SRP section is concerned with understanding the stability of material and foundations in 

the subsurface. Most of this SRP section would be applicable directly for an SMR. 

Concerns: 

For a deeply-embedded SMR, the following issues need to be addressed in a way potentially 

different from how they would be handled for a large LWR at or near the surface. The issues 

are: 

(1) The construction of the deep excavation may affect the surrounding soil properties that 

are used in the analysis and design of the foundation and plant structures. (See SRP 

section 2.5.4.5.) 

 
32 

(2) The effect of dewatering, both during and after construction, considering the higher 

head and volume of ground water, may be more significant to the structures than its 

effect for LWRs. (See SRP section 2.5.4.6.) 

(3) Adequate measuring points to monitor settlement throughout the depth of the 

embedded structure may be needed. (See SRP section 2.5.4.10.) 

1.5.11 SRP 3.7.1 (“Seismic Design Parameters”), 3.7.2 (“Seismic System 

Analysis”), and 3.7.3 (“Seismic Subsystem Analysis”) (March 2007 

versions) 

Evaluation of the applicability to SMRs on individual foundations 

Positive findings: 

These SRP sections seem to have broad applicability to SMRs, but some of the guidance may 

not be applicable. 

Concerns: 

For a deeply-embedded SMR, the technical review approaches in these SRP sections may 

need to be re-examined. In particular, the development of a consistent seismic input for 

response and SSI analyses and then for design of a specific SSC can be different than for a 

large LWR on or near the surface. A number of issues require reevaluation, and the application 

of these SRP sections without such a reevaluation could lead to a compromise in the design 

margins. One issue is that the way the soil column interacts with a deeply-embedded structure 

can be quite different, which affects how the seismic energy propagates further into the 

structure. Design using this type of input, if inappropriate, can then lead to incorrect design 

solutions. The staff review, guided by the SRP, needs to identify these if they are present. 

These SRP sections are concerned with design parameters and also with analysis methods. 

The detailed guidance about analysis methods in SRP sections 3.7.2 and 3.7.3 may also need 

to be reevaluated for a deeply-embedded SMR. 

1.5.12 SRP 3.8.3, “Concrete and Steel Internal Structures of Steel or 

Concrete Containments” (March 2007 version) 

Evaluation of the applicability to SMRs on individual foundations 

Positive findings: 

This SRP section deals extensively with reactors and containments of different scales and 

different features (e.g., existing licensed large PWRs and BWRs.) This means that it is likely 

that most if not all of it can be used for SMRs without change. 

Concerns: 

This SRP section’s text (throughout both Section I and Section II) specifically calls out certain 

features of LWR containments that were written with today’s large LWR containments (and their 

typical internal structures) in mind. An SMR is likely not only to have a significantly smaller 

containment but also (by extension) significantly smaller internal structures. 

A section of the SRP on modular walls (in the final paragraph of Section I.1, on page 6) calls for 

case-by-case evaluation. This provision means that SMRs can in principle be accommodated 
33 

without a change to the text, albeit without any specific guidance. 

Overall, the technical requirements of this SRP section are applicable to SMR internal 

structures. However, because the text calls out large LWR features and provisions in several 

places, a reviewer must be cautious to read the intent of the requirements carefully. It would be 

prudent for the NRC to consider revision of this SRP section to address the concerns as 

expressed above so that the section can apply to all potential SMR designs. 

1.5.13 SRP 3.8.4, “Other Seismic Category I Structures” (March 2007 

version) 

Evaluation of the applicability to SMRs on individual foundations 

Positive findings: 

This SRP section seems to have broad applicability to SMRs although a careful review would 

be needed when an evaluation is done for a specific SMR and its several “other” structures. 

Concerns: 

The text has much that is specific to large LWRs along with sections that can apply broadly to 

“other” structures. However, the references to large LWRs seem easily adapted without loss of 

technical validity. 

The only specific concern is for load combinations that may have been derived for specific 

“other structures” for large-LWR-related designs. (See Sections I.3 on page 4 and II.3 on page 

9 of the SRP.) 

It is also important to be cognizant of the recent issuance by ASME (in 2011) of a new section 

of the boiler and pressure vessel code (ASME III Division 5) applicable to high- temperature 

reactors. In preparation for review of an SMR design that may be developed using that code, 

this SRP section may require revision to cite this new code section as a reference, or perhaps it 

may need to be significantly re-written to address the code’s provisions explicitly. 

Overall, perhaps more specificity for SMRs would be needed if a special structure is under 

review for an SMR that is not under the “umbrella” of one of the several specific structures 

mentioned here. The NRC should review this technical issue and consider revising the SRP 

section. However, any changes to the SRP section are likely to be modest. 

1.5.14 SRP 3.8.5, “Foundations” (March 2007 version)

Evaluation of the applicability to SMRs on individual foundations 

Positive findings: 

This SRP section seems to have broad applicability to SMRs. 

Concerns: 

The factors of safety on pages 9-10 may have been derived with large LWRs in mind. If so, 

revisiting them would be required. The NRC should review this technical issue and consider 

revising the SRP section technically, if appropriate, or by including wording that notes that a 

case-by-case review is appropriate if an SMR design is under review. This could be needed 

 
34 

especially for the case of closely spaced individual SMR foundations. However, any changes to 

make the SRP section technology-neutral would likely be minor. 

1.5.15 SRP 3.9.1, “Special Topics for Mechanical Components” (March 2007 

version) 

Evaluation of the applicability to SMRs on individual foundations 

Positive findings: 

This SRP section seems to have broad applicability to SMRs. 

Concerns: 

Part of the discussion of the SRP review of core supports and reactor internals was clearly 

developed with large LWRs in mind. This includes how various transients that could affect 

loads on core supports and internals are to be treated (see Section II, “SRP Acceptance 

Criteria,” bullet 1 on page 4). These may not be generic. The NRC should review this technical 

issue and consider revising the SRP section technically, if appropriate, or by including wording 

that notes that a case-by-case review is appropriate if an SMR design is under review. 

However, any changes to make the SRP section technology-neutral would likely be minor. 

It is also important to be cognizant of the recent issuance by ASME (in 2011) of a new section 

of the boiler and pressure vessel code (ASME III Division 5) applicable to high- temperature 

reactors. In preparation for review of an SMR design that may be developed using that code, 

this SRP section may require revision to cite this new code section as a reference, or perhaps it 

may need to be significantly re-written to address the code’s provisions explicitly. 

1.5.16 SRP 3.9.2, “Dynamic Testing and Analysis of Systems, Structures, 

and Components” (March 2007 version) 

Evaluation of the applicability to SMRs on individual foundations 

Positive findings: 

This SRP section seems to have broad applicability to SMRs. 

Concerns: 

The SRP’s text has some discussion of components that are specific to large LWRs (e.g., see 

Section I.3 on page 4, Section I.4 on page 6 and Section II, “SRP Acceptance Criteria,” 1.B on 

page 10). They are used generally as examples and, to that extent, no problem should exist in 

applying this SRP section to SMRs. Also, some of the SRP text seems to assume that major 

components are outside the primary vessel. This text may not be directly applicable to SMR 

designs in which those same major components are inside the primary vessel (see Section II, 

“SRP Acceptance Criteria” 2.A, on pages 10-11 and Section III.2A on page 26 as possible 

examples.) The NRC should review this technical issue and consider revising the SRP section 

technically, if appropriate, or by including wording that notes that a case-by-case review is 

appropriate if an SMR design is under review. However, if any changes are needed to make 

this SRP section technology-neutral, they would likely be minor. 

 
35 

1.5.17 SRP 3.9.3, “ASME Code Class 1, 2, and 3 Components and 

Component Supports, and Core Support Structures” (March 2007 

version) 

Evaluation of the applicability to SMRs on individual foundations 

Positive findings: 

This SRP section seems to have broad applicability to SMRs. 

Concerns: 

The SRP has several references to specific PWR and/or BWR SSCs (this occurs throughout). 

Although the text is specific in some cases to large LWRs, the SRP section can be used for 

SMRs with minor adaptations (to make it technology-neutral). This should not present a 

problem, and there appears to be no ambiguity. The NRC should consider revising this SRP 

section to accomplish this. 

For core designs that are very different from LWR cores (e.g., for a gas-cooled reactor or a 

liquid-metal reactor), the core support section of this SRP would need to be reviewed for 

applicability and possibly revised. 

It is also important to be cognizant of the recent issuance by ASME (in 2011) of a new section 

of the boiler and pressure vessel code (ASME III Division 5) applicable to high- temperature 

reactors. In preparation for review of an SMR design that may be developed using that code, 

this SRP section may require revision to cite this new code section as a reference or perhaps it 

may need to be significantly re-written to address the code’s provisions explicitly. 

1.5.18 SRP 3.9.4, “Control Rod Drive Systems” (March 2007 version) 

Evaluation of the applicability to SMRs on individual foundations 

Positive findings: 

This SRP section seems to have broad applicability to SMRs. 

Concerns: 

This SRP section is definitely not technology-neutral. It contains several sections specific to 

hydraulic or electromagnetic control rod drive systems (CRDS) that are clearly tailored to a 

review of CRDS for large PWRs or BWRs. However, the text does contain a sentence (page 2) 

that states plainly how other technologies would be treated: 

If other types of CRDS are proposed or if new features that are not specifically 

mentioned here are incorporated in CRDS of current types, the information 

supplied for the new systems or new features should be similar to the information 

described below. 

Given the above, perhaps no modification is needed to the text of this SRP section. 

Alternatively, if a quite different CRDS technology for an SMR is proposed that will come into 

widespread use, then perhaps some specific areas of review for that technology should be 

described in the SRP itself. In that case, the NRC should consider revising this SRP section to 

accomplish this. Such changes should be minor. 
36 

Another possible concern is that this SRP section specifically mentions that “portions of the 

CRDS are part of the reactor coolant pressure boundary” (see Section I in the first paragraph on 

page 1 and then elsewhere in subsequent text). This may or may not be true for the CRDS for 

any specific new SMR design. If review confirms that the issue is important, then it could be 

addressed either by revising the SRP section technically or by including wording that notes that 

a case-by-case review is appropriate if an SMR design is under review. 

1.6 Evaluation of Each Regulatory Document (from Table 1-3) for

Which Important Changes May Be Needed

1.6.1 Regulatory Guide 1.29, “Seismic Design Classification” (March 

2007 version)

Evaluation of the applicability to SMRs on individual foundations 

Positive findings: 

Much of this SRP section seems to have broad applicability to SMRs but with some important 

exceptions. 

Concerns: 

The classification scheme described in this regulatory guide contains many specific features 

that are tailored to large-LWR technology, and some of the entries in Section C probably do not 

apply to SMRs. More importantly, the scope herein is probably not sufficient to cover all of the 

features of a typical SMR with its smaller overall design, different design features, and reduced 

mass and size. It is judged that important changes are probably needed to this RG─mainly 

throughout Section C─but that changes or adaptations may need to be made on an SMRdesign-specific basis. This issue could be addressed either by revising the SRP section 

technically or by including wording that notes that a case-by-case review is appropriate if an 

SMR design is under review. 

1.6.2 Regulatory Guide 1.61, Damping Values for Design of Nuclear 

Power Plants” (March 2007 version) 

Evaluation of the applicability to SMRs on individual foundations 

Positive findings: 

Much of this SRP section seems to have broad applicability to SMRs. 

Concerns: 

This regulatory guide has structural damping values that may not apply to all of the constituent 

parts of an SMR with its significantly smaller size and mass (see Section C, Tables 1 and 2). 

Also, for reactors for which major components (such as large pumps and heat exchangers) are 

totally submerged inside the vessel, the damping values appropriate for large LWRs may not 

apply. Modifications to accommodate these concerns could be significant rather than modest in 

their extent and importance. This issue could be addressed either by revising the SRP section 

technically or by including wording that notes that a case-by-case review is appropriate if an 

SMR design is under review. 
37 

The other damping values in the SRP, other than for structural damping, seem fully applicable 

to an SMR. These include damping values for constituent systems like piping (Table 3), 

electrical systems (Table 4), HVAC (Table 5), and mechanical and electrical components (Table 

6). 

1.6.3 SRP 3.2.1, “Seismic Classification” (March 2007 version) 

Evaluation of the applicability to SMRs on individual foundations 

Positive findings: 

This SRP section seems to have broad applicability to SMRs. 

Concerns: 

This SRP section contains some specific text applicable to large BWRs that is directed 

especially toward that technology (see Sections III.4 and IV.5). If an SMR design was a smaller 

BWR, the applicability of this text to such a design would definitely need reconsideration. 

In addition, this section contains numerous cross-references to Regulatory Guide 1.29, which 

also needs re-evaluation before it can be applied to SMRs (please refer to the discussion of RG 

1.29 just above). 

1.6.4 SRP 3.8.1, “Concrete Containment” (March 2007 version) 

Evaluation of the applicability to SMRs on individual foundations 

Positive findings: 

Some of this SRP section seems to have broad applicability to SMRs 

Concerns:

Some of the text in SRP 3.8.1, “Concrete Containment,” is clearly written with large LWRs in 

mind. For example, the following is on page 2: 

Various geometries have been used for these containments. The geometry 

most commonly encountered is an upright cylinder topped with a dome and 

supported on a flat concrete base mat. Although applicable to any geometry, 

the specific provisions of this SRP section are best suited to the cylindrical-type 

containment topped by a dome. Reviews of containments with other types of 

geometry will make the necessary deviations from this SRP section on a caseby-case basis.

Another possible concern is related to load combinations (see Section II, “SRP Acceptance 

Criteria”, paragraph 3, pages 10-12). For the smaller SMR designs, some of the considerations 

herein may not apply, but this would need to be evaluated on a case-by-case basis to 

determine if the SRP section is applicable without modification. 

Also, some of the loading discussions in the same part of Section II may need to be 

reconsidered for the significantly smaller SMR designs. 

For both of these concerns, the concern could be addressed either by revising the SRP section 

technically or by including wording that notes that a case-by-case review is appropriate if an 
38 

SMR design is under review. Consideration should be given to moving this guidance into a 

Regulatory Guide. 

1.6.5 SRP 3.8.2, “Steel Containment” (March 2007 version) 

Evaluation of the applicability to SMRs on individual foundations 

Positive findings: 

Some of this SRP section seems to have broad applicability to SMRs. 

Concerns: 

Much of the text in SRP 3.8.2, “Steel Containment,” is not generic but rather is specific to large 

LWRs. It is possible that a wholesale revision of many sections of the SRP section will be 

necessary to apply to the steel containment of an SMR, depending on the design. In particular, 

the long section on load combinations (pages 10 to 15) seems to have been written with large 

LWRs specifically in mind. This concern could be addressed either by revising the SRP section 

technically or by including wording that notes a case-by-case review is appropriate if an SMR 

design is under review. 

1.6.6 SRP 3.9.5, “Reactor Pressure Vessel Internals” (March 2007 

version) 

Evaluation of the applicability to SMRs on individual foundations 

Positive findings: 

Some of this SRP section seems to have broad applicability to SMRs. 

Concerns: 

Some of the text in SRP 3.9.5, “Reactor Pressure Vessel Internals,” is not generic but rather is 

specific to large LWRs. Some of the SRP text seems to assume that major components are 

outside the primary vessel; this text may not be directly applicable to some SMR designs in 

which those same major components are inside the primary vessel. A wholesale revision of 

some sections of the SRP section may be necessary to apply to the internals of an SMR, 

depending on the design. In particular, Appendix A (covering potential adverse flow effects) 

was written with large LWRs specifically in mind. How much of this might apply to a specific 

SMR design is not clear, but a lot of it would need to be rewritten. This concern could be 

addressed either by revising the SRP section technically or by including wording that notes a 

case-by-case review is appropriate if an SMR design is under review. 

It is also important to be cognizant of the recent issuance by ASME (in 2011) of a new section 

of the boiler and pressure vessel code (ASME III Division 5) applicable to high-temperature 

reactors. In preparation for review of an SMR design that may be developed using that code, 

this SRP section may require revision to cite this new code section as a reference or perhaps it 

may need to be significantly re-written to address the code’s provisions explicitly. 

1.7 Consensus Codes and Standards

In Section 1.3.6, several industry-wide consensus codes and standards were identified as 

perhaps having been written with large LWRs in mind. This means that their applicability to 
39 

SMRs would require evaluation. Those codes and standards include ASCE 4-98, ASCE 43-05, 

ASME-ANS RA-Sa-2009 (the PRA methodology standard), and certain selected parts of the 

ASME boiler and pressure vessel code. As noted above, ASME has recently issued a new 

division to Section III of the boiler and pressure vessel code to address some non-LWR reactor 

designs. 

Each of these consensus standards is long, complex, and written with large LWRs in mind 

(other than the new division to Section III of the ASME code). An evaluation of where each of 

them applies to SMRs, where it does not, and where an ambiguity exists was not attempted 

here. 

1.8 Summary for Section 1 

The evaluation in Section 1 of this report has presented a categorized list of NRC documents 

and industry codes and standards relevant to the areas of seismic engineering, structural 

engineering, geotechnical engineering, and relating topics. The categorization is based on a 

technical judgment by the Lawrence Berkeley National Laboratory team as to whether or not the 

document would require changes so that it could be used for SMRs, recognizing that in almost 

every case the document has been developed and used based on its applicability to current 

large LWRs. 

The categorization placed the various documents into three categories as noted above in 

Section 1.2. Essentially, the three categories could be described as “no change needed,” 

“modest and non-controversial changes may be needed,” and “important changes may be 

needed.” A rationale is provided for each categorization decision in Section 1.4, and a detailed 

evaluation for the second and third categories is found in Sections 1.5 and 1.6, respectively. 

Where appropriate, a recommendation is made for a modification so that the document could 

be used for the safety review of an SMR. 

41 

2. EVALUATION OF SEISMIC-STRUCTURAL SIMULATION

TOOLS FOR APPLICABILITY TO SMALL MODULAR

REACTORS

2.1 Introduction to Section 2

Section 2 of this report provides the results of one part of “Soil Structure Interactions for Small 

Modular Reactors on Individual Foundations,” a project carried out at the University of 

California’s Lawrence Berkeley National Laboratory (LBNL) and sponsored by the U.S. Nuclear 

Regulatory Commission’s (NRC’s) Office of Nuclear Regulatory Research. 

The evaluation in Section 2 was focused on two tasks: 

Identification of Applicable NRC-approved simulation tools

In this task, the project team compiled a library of widely used analysis tools in the areas of 

structural, geotechnical, and seismic engineering. Each simulation tool was studied to

determine how industry designers and analysts have used it for large LWRs and how the NRC 

regulatory staff has interpreted the results of the simulations. The simulation tools that were 

identified are those used to evaluate seismic issues as used in structural engineering, 

geotechnical engineering, and other related engineering areas. A list of the tools and 

simulations identified has been compiled in this report. 

Evaluation of Applicability to Small Modular Reactors

In this task, the project team analyzed each simulation tool identified above for applicability to 

small modular reactors (SMRs). The areas examined included (a) structural engineering, (b) 

geotechnical engineering, and (c) seismic engineering including soil-structure interaction. The 

hazard being studied was large earthquakes. 

Limitation: The scope covers the relevant analysis tools that are most widely used in the 

industry. Some of these tools have been NRC-endorsed for specific purposes, but others have 

not been endorsed. 

Limitation: The LBNL team and the NRC staff agreed that identifying specific SMR designs was 

not necessary ─ that an evaluation could be performed that would be more generically 

applicable to all of the different types of SMRs. However, this may or may not be true for all 

SMR designs. 

2.2 The Work – Two Phases

The first phase of the work reported here was the identification of a list of simulation tools 

(codes) for evaluation in the second phase. The second phase was the evaluation. 

2.2.1 The First Phase, Identification

The first phase began with a series of contacts with various industry experts, practicing 

engineers, and several NRC staff members who either worked on nuclear power plant (NPP) 

seismic-structural-civil-engineering design and analysis or reviewed designs and analyses done 
42 

by others. The purpose of this phase was to identify those simulation tools that had been used 

most commonly in the design and analysis of large LWRs with the application in mind being a 

submittal for NRC staff regulatory review and approval. In effect, this meant identifying a list of 

those simulation tools that the staff was sufficiently familiar with and aware of in terms of 

strengths, limitations, inputs, and results. In other words, this phase involved a search for 

simulation tools that had been used frequently in industry submittals to the NRC and for which 

dockets exist containing favorable NRC staff reviews of analyses using the simulation tool. 

These favorable reviews would reflect the reputation or “pedigree” (formal or informal) the 

simulation tool enjoys in the community of practitioners. 

The LBNL project team had expected that large variations would exist between the “lists” of the 

various experts (i.e., that little overlap would be evident among the several “lists”). However, this 

was not the case. Specifically, although some simulation tools are not widely used (i.e., limited 

perhaps to a single user or a single company), the suite of simulation tools in widespread use 

turned out to be almost the same list for everyone consulted. 

Table 2-1 presents the final list of simulation tools that has been the subject of this evaluation. 

In addition, the project team added the new analysis tool called “ESSI” (“Earthquake Soil 

Structure Interaction”) to its evaluation list. ESSI is under development by a team led by Boris 

Jeremic at LBNL and the University of California at Davis, and the NRC is supporting its 

development. Unlike the other analysis tools that were evaluated, ESSI is not in widespread use 

in the nuclear industry because it is still being developed. However, because the ESSI code is 

being developed under NRC support as a publicly available code, it is included and therefore 

may be used in the future in evaluating SMRs. Dr. Jeremic separately evaluated the ESSI code 

for use with SMRs, and this is covered in a separate discussion below (see Section 2.2.7). 

The second part of this identification task was to obtain a working version of each simulation 

tool that could be loaded into the project team’s in-house computers along with written material 

(i.e., a “manual”) that would serve to aid the project team as it exercised the simulation tool and 

evaluated it. This task was ultimately successful, but initial versions of some of the simulation 

tools the project team found were only available in “student versions” or “trial versions.” These 

more modest versions were typically sufficient to enable the project team to gain no more than 

superficial familiarity with the code; however, the project team did succeed in obtaining a more 

complete version of each simulation tool (see Table 2-1) and in getting it up and running. Again, 

this applies to all of the analysis tools except the ESSI simulation tool that was evaluated 

separately (see Section 2.2.7). 
43 

Table 2-1 - List of Simulation Tools Evaluated 

ABAQUS 

ADINA 

ALGOR 

ANSYS 

GT STRUDL 

LS-DYNA 

NASTRAN 

SAP 2000 

SASSI 

SHAKE91 

SIMQKE-1 

STARDYNE 

Separate evaluation: ESSI 

2.2.2 The Second Phase, Evaluation

The LBNL project team subjected each of the various simulation tools (codes) to an 

independent review. The team studied the manual, loaded the code up onto one of their 

computers, and performed various reviews of each code’s capabilities (the ESSI was evaluated 

separately; see Section 2.2.7). 

For each of the simulation tools that was examined, the project team asked a fundamental 

question: “Is there something about this code, as it is used for large-LWR design or analysis, 

that “would not work” for an SMR─some feature that would make it wholly or even partially 

unusable for the design or analysis of an SMR?” 

The project team looked for specific features embedded in the code that might have been 

present specifically to enable design or analysis of a large LWR but that “would not work” for an 

SMR. These specific features could include large-LWR-specific or other approximations, scaling 

effects, specific data, assumptions, or some combination. In addition, the team tried to identify 

some way that an SMR user of the code might be led astray or might find that the code simply 

could not be used for a typical SMR design or analysis problem (or could be used only with one 

or more important compromises). 

The approach taken was to search for element types, material models, boundary conditions, or 

analysis procedures of the analysis tool, if any, that would compel the project team to question 

the usefulness of the analysis tool for the design or analysis of an SMR. Initially, this meant 

studying the code manual or descriptive material to understand how the analysis tool had been 

developed, what physical principles or equations are embedded in it, and how the code 

produces its “results” or “outputs.” This is, of course, the sort of examination and critical 

evaluation that any new user of any analysis tool must do before beginning to use that tool. 

The most important part of the project team evaluation involved examining the physical 

principles and the equations on which the code is based. A key aspect of that work, in turn, was 

to understand the approximations embedded in the code itself. Because any analytical tool is 

only an abstraction of reality developed for a specific purpose, approximations will always be 

 
44 

present─sometimes in the “physics,” sometimes in the way the binning is done, sometimes in

how the input data are specified or used, sometimes in the computational algorithm, or others. 

The project team needed to understand these approximations before the SMR evaluation could

be undertaken. 

A crucial aspect of the SMR evaluation was examining the detailed way in which the code

handles scale-dependent features such as dimensional or mass-dependent features. The

project team had the benefit of details about one specific SMR design with actual masses and

dimensions, but it used the information in a stylized way, not as a specific focus and also not by

analysis of that particular SMR per se. The team instead tried to focus on the following broader

question─if an SMR-type structure on its own foundation were the subject of the code’s analysis

instead of a large LWR, would any approximations introduced in the code itself make its

analyses somehow “less valid,” or “less accurate,” or “more approximate?” 

Clearly, for any specific problem, the analyst must generate a finite element method (FEM)

model with the masses, dimensions, configuration(s), and so on. This must be done with great

care because every analyst needs to be mindful of the adage “garbage in, garbage out.” On this 

aspect, the team’s inquiry was limited to exploring whether creating such an FEM model for an 

SMR structure with its different masses, dimensions, and so on was fully feasible and did not

introduce problems within the parameters of the code and its instructions. It should be noted

that this inquiry is different than asking specifically about how the FEM model is to be created (a

question that was not important for the project team’s purposes). 

As the work began, the project team had no idea whether any of these simulation tools might

suffer from one or more of these problems if used with an SMR-type design. Therefore, the team 

was pleasantly surprised when it found no such problems anywhere it looked. 

2.2.3 Broad Conclusion

The LBNL project team’s overall broad conclusion, reached separately for each of the simulation 

tools in Table 2-1, is that nothing in any of the codes would preclude a competent user from 

developing valid results and reaching valid conclusions about an SMR through employing that 

code for SMR design or analysis. 

Of course, there are always caveats and warnings to consider. Any user of any simulation tool

must be generally competent in understanding the underlying physics and engineering that have

gone into the code. A user needs to understand the broad limitations of any code. No code can

ever be a completely accurate way to describe any physical problem or situation. As mentioned

above, any code is inevitably only an abstraction of the underlying reality developed for a specific 

purpose─in this case, a design purpose or an analysis purpose. 

The next sections will present the project team’s evaluations, one code at a time, to support this

overall broad conclusion. Some of the discussions in the individual subsections below may

seem repetitive because many of the issues and features that the team identified are common to 

several of the simulation tools. However, the fundamental feature of a code that makes it

applicable (or not) to both large LWRs and the much smaller SMRs is the issue of how it scales.

That is, the operative question is whether one or more scale-dependent features of the code 

allow the user to produce “valid” results for a large LWR but not allow for a smaller SMR

because of “scaling” issues. The project team did not identify any such features. 

 
45 

There are other reasons why a code that “works” for a large LWR might not “work” for designing 

or analyzing an SMR-sized problem. As mentioned, specific data embedded in a code, or 

assumptions or approximations within it, might be a problem. The project team did not identify

any such problems. 

2.2.4 Analysis of an SMR Adjacent to One or More Others

The general concept behind deploying small modular reactors (SMRs) is that, because they are 

significantly smaller than a large LWR, a typical electric-generating station site would deploy 

more than 1─perhaps as many as 5 or 10─on a single site although not all would likely be built 

at the same time. A common strategy often discussed in the industry is to “stage” the 

construction of a number of these SMR units over several years, perhaps even over a decade 

or more. 

This strategy presents the following analysis problem─specifically, the seismic-structural 

analysis of operating SMR #1 while SMR #2 is under construction nearby. Or perhaps SMRs 

#1, #2, etc. (up to #6) are operating while SMRs #7 and #8 are under construction nearby. 

As background, analysis of the seismic safety of a configuration like this is now done routinely 

for large LWRs. Specifically, both in the United States and abroad, large-LWR sites exist today 

with one or more operating LWRs and a large construction project underway nearby to build a 

new large LWR, or sometimes two. The effect of the new plant on the safety of the existing 

operating unit(s)─both while the construction is underway and later when the new reactor is in 

operation─is a required analysis that must be done to ensure safety. 

The project team’s work here has tried to determine whether there is something about the 

smaller SMRs that would make this analysis problem more difficult or would mean that the 

analysis tools (codes) would be unable to carry out this analysis for a multiple-SMR site even 

though the analysis “works” for a multiple-LWR site. 

The project team examined several analysis codes with this is mind and determined that the 

main technical issue for the analyst is “setting up the problem” correctly. After recognizing that 

this is a challenge for the multiple-LWR analysis problem, the team asked whether it could 

identify something special about the multiple-SMR problem. 

After some deliberation, the project team has concluded that it can’t identify anything like that. 

The codes themselves seem to be as adaptable to the SMR-type multiple unit analysis 

problems as to the analogous multiple-large-LWR problems. The team did not identify anything 

in the analysis tools themselves that would be problematical. In addition, the team did not

identify any issues with the way the codes make approximations that might not apply to the

multiple-SMR problem. Consequently, the team concluded that it need not be concerned about

this issue. 

One of the analysis tools, SASSI, may be different in this regard (see Section 2.2.6.9 below.)

The way soil-structure-interaction (SSI) phenomena occur may be complex enough that the

ordinary SSI tools like SASSI may have greater difficulty with the multi-unit analysis problem

than is the case for the other analysis tools evaluated here. This issue is too complex to 

evaluate easily, and therefore the project team believes that the broad conclusion it has reached

in the paragraph above about the other analysis tools may not apply to SASSI. 

 
46 

2.2.5 Discussion of Embedment Issues

SMR design concepts covering a very broad range of technologies are being discussed by the

various industrial designers and vendors. Some concepts seem to contemplate placing the

SMRs at or near the surface, while others discuss either partial embedment or perhaps even

complete embedment below the surface. This has led the project team to consider whether the

analysis tools being evaluated here would be applicable for analyzing an SMR design with

significant or full embedment. (The modest embedments typical of large LWR construction, if

used for an SMR, are not seen as an issue.) 

No large LWR has ever been fully embedded (i.e., underground) although many of them are 

embedded partially (but almost never to a significant percentage.) The project team tried to 

determine whether something about the smaller SMRs would make this analysis problem 

particularly intractable. Moreover, the team tried to determine whether any specific analysis tool 

would suffer from an important technical problem if the SMR being analyzed were embedded. 

The project team examined the several analysis codes with this in mind. The fact that the 

analysis would be for an SMR did not give rise to any identifiable technical problems. 

The major concern in any analysis of an embedded structure─whether for a large LWR or a 

smaller SMR─is for the analyst to “set up the problem” appropriately, including the boundary 

conditions. Although this can be a challenge, it appears to be no different for an SMR than for a 

large LWR. The codes themselves seem to be as adaptable to an SMR-type embedment

analysis problem as to the analogous large-LWR problem. The project team has not identified

anything in the analysis tools themselves that would be problematical. 

One of the analysis tools, SASSI, may be different in this regard (see Section 2.2.6.9 below).

Soil-structure-interaction (SSI) phenomena may be very complex when soil is in direct contact

around, for example, the vertical walls of a fully embedded cylindrical structure. Ordinary SSI

tools like SASSI may have greater difficulty with a fully embedded structure than is the case for

the other analysis tools evaluated here. This issue is too complex to evaluate easily. 

Consequently, the project team’s broad conclusion may not apply to SASSI. 

2.2.6 Code by Code Evaluations

Opening Note—Finite Element Method (FEM) Codes 

A majority of the simulation tools (codes) that have been evaluated in this review are FEM (finite 

element method) codes. Therefore, it is worthwhile to provide a short general introduction to the 

approach to avoid repeating it under the discussion of each individual simulation tool. 

The finite element method (FEM) (which in practical applications is often known as the “finite 

element analysis” [FEA] method) is a numerical technique for finding approximate solutions of 

partial differential equations (PDE) as well as integral equations under specific boundary 

conditions. The solution approach is based either on eliminating the differential equation 

completely (steady-state problems) or rendering the PDE into an approximate system of 

ordinary differential equations that are then numerically integrated using standard techniques 

such as Euler's method, Runge-Kutta, etc. 

 
47 

In modern engineering design, it is rare to find a project that does not require some type of finite 

element analysis. When not actually required, FEA can usually be used to improve a design. 

The practical advantages of FEA in stress analysis and structural dynamics have made it the

accepted design tool for the last three decades. The greatest advantage of FEA is its ability to

handle truly arbitrary geometry. Probably its next most important features are its abilities to deal

with general boundary conditions and to include nonhomogeneous and anisotropic materials. 

These features alone mean that the engineer can treat systems of arbitrary shape that are made 

up of numerous different material regions. Each material could have constant properties, or 

the properties could vary with spatial location. To these very desirable features can be added a 

large amount of freedom in prescribing the loading conditions and in the post-processing of items 

such as the stresses and strains. For elliptical boundary value problems, the FEA procedures 

offer significant computational and storage efficiencies that further enhance their use. 

These classes of problems include stress analysis, heat conduction, electrical fields, magnetic 

fields, ideal fluid flow, and others. FEA also gives the analyst and designer an important 

solution technique for other problem classes such as the nonlinear Navier-Stokes equations 

for fluid dynamics and for plasticity in nonlinear solids. 

In a structural simulation, FEM helps tremendously in producing stiffness and strength 

visualizations and also in minimizing weight, materials, and costs. FEM allows detailed 

visualization of where structures bend or twist and indicates the distribution of stresses and 

displacements. FEM software provides a wide range of simulation options for controlling the 

complexity of both modeling and analysis of a system. Similarly, the desired level of accuracy 

required and associated computational time requirements can be managed simultaneously to 

address most engineering applications. FEM allows entire designs to be constructed, refined, 

and optimized before the design is manufactured. 

The LBNL project team has concluded that the partial differential equations (PDEs), integral 

equations, or boundary conditions used in performing the structural-civil-seismic analysis of 

SMRs are generally the same as those used for conventional-sized large LWR reactors, 

considering that SMRs have the size of at least several meters and belong to the same scale of 

dimensions as conventional larger reactors. Some other problems, such as earth science 

problems or nano-mechanics problems, may have different scales and even different PDEs or 

integral equations. However, the analysis of an SMR or of a conventional-sized large LWR 

reactor uses the same types of PDEs or integral equations. Therefore, to the extent that a code 

does not contain scale-specific aspects, the broad suite of FEM codes that are used for 

conventional-sized large LWR reactors can also be used for SMRs. 

Opening note─Descriptions below of a few of the several simulation tools (codes) have been

taken almost verbatim, or paraphrased, from the developer’s or distributor’s literature. The

information is included more to provide background information than to support the SMR vs.

large-LWR evaluations herein. 

2.2.6.1 ABAQUS

ABAQUS is one of a family of FEM codes. ABAQUS is a high-performance software package 

developed by Hibbitt, Karlsson & Sorensen, Inc. (now Dassault Systemes) for finite element 

modeling of structural response. It enables the user to do linear or nonlinear and static or 

dynamic types of analysis for a large spectrum of engineering problems. The ABAQUS suite of 

engineering analysis software packages is used throughout the world to simulate the physical 

response of structures and solid bodies to load, temperature, contact, impact, and other 
48 

environmental conditions. The software operates on major computers and operating systems 

from PCs to workstations to supercomputers. 

Analysis Type − Designed as a general-purpose simulation tool, ABAQUS can be used to study 

more than just structural (stress/displacement) problems. It can simulate problems in such 

diverse areas as heat transfer, mass diffusion, thermal management of electrical components 

(coupled thermal-electrical analyses), acoustics, soil mechanics (coupled pore fluid-stress

analyses), piezoelectric analysis, electromagnetic analysis, and fluid dynamics. 

Element Types Used − ABAQUS has an extensive element library to provide a powerful set of

tools for solving many different problems. The user can choose an element type that

characterizes, among other things, the degree-of-freedom set (displacements and/or rotations,

temperatures, etc.); the characteristic shape of the element (line, quadrilateral, brick, etc.);

whether the element lies in 2-D space or 3-D space; the response of your system; and the

accuracy level of interest. 

Material Properties − ABAQUS has an extensive list of material models that can simulate the

behavior of most typical engineering materials including metals, rubber, polymers, composites,

reinforced concrete, crushable and resilient foams, and geotechnical materials such as soils and

rock. 

ABAQUS offers a wide range of capabilities for simulation of linear and nonlinear applications.

Problems with multiple components are modeled by associating the geometry defining each

component with the appropriate material models and specifying component interactions. In a

nonlinear analysis, ABAQUS automatically chooses appropriate load increments and

convergence tolerances and continually adjusts them during the analysis to ensure that an

accurate solution is obtained efficiently. 

2.2.6.2 ADINA

ADINA is one of a family of FEM codes. ADINA comprises a wide variety of solution techniques

for static and transient problems that include the robust nonlinear analysis techniques that give

this finite-element toolkit its name (ADINA = Automatic Dynamic Incremental Nonlinear

Analysis). In addition to its considerable capabilities for structural analysis, ADINA also permits

fully coupled fluid-structure interaction simulations that are useful for tsunami analyses. The

ADINA system includes a wide variety of capabilities such as integration with solids modeling

applications, visual pre- and post-processing tools, and features to support multiphysics

simulations involving coupled solid, fluid, and thermal response. 

ADINA FSI − Fluid-structure interaction (FSI) occurs when fluid flow causes deformation of the

structure. This deformation, in turn, changes the boundary conditions of the fluid flow. 

ADINA offers fluid-structure interaction capabilities in one single program for the solution of

problems where the fluids are fully coupled to general structures that can undergo highly

nonlinear response due to large deformations, inelasticity, contact, and temperature

dependency. A fully coupled fluid-structure interaction means that the response of the solid is

strongly affected by the response of the fluid and vice versa. 

Evaluation: There seems to be nothing in ABAQUS would preclude a competent user from

developing valid results and reaching valid conclusions about an SMR. 
49 

From the fluid point of view, the Navier-Stokes flow can be incompressible, slightly compressible, 

low-speed or high-speed compressible. From the structural point of view, all available element 

types can be used (shell, 2-D and 3-D solid, beam, iso-beam, contact surfaces, etc.) as well as 

all available material models. 

2.2.6.3 ALGOR

ALGOR is one of a family of FEM codes. ALGOR, now known as Autodesk Simulation

Mechanical or Autodesk Simulation Multiphysics software, is a general-purpose multiphysics

finite element analysis software package developed by ALGOR Inc. for use on the Microsoft

Windows and GNU/Linux computer operating systems. It is distributed in a number of different

core packages to cater to specific applications such as mechanical event simulation and

computational fluid dynamics. 

Analysis Type: Multiphysics, Linear, Nonlinear, Thermal, Fluid Flow, Electrostatic, Fatigue

Analysis, Mass Transfer 

Element Types: Beam Elements, Gap Elements, Rigid Elements, Spring Elements, Truss

Elements, 2D Elements, Membrane Elements, Plate Elements, Thick Composite Elements, Thin

Composite Elements, Brick Elements, Tetrahedral Elements, Incompatible Displacement Modes 

Material: Consider actual material behavior for foam, gasket, rubber, plastic, and other nonlinear

materials. Choose from a wide range of nonlinear material models to get more accurate results

when a part’s operation involves twisting, stretching, squashing, or buckling. Learn how a part

will likely fail, especially when large deformation occurs. 

2.2.6.4 ANSYS

ANSYS is a general purpose finite element modeling package for numerically solving a wide

variety of mechanical problems. These problems include static/dynamic structural analysis (both 

linear and nonlinear), heat transfer and fluid problems, and acoustic and electromagnetic

problems. 

The software operates on major computers and operating systems from PCs to workstations to 

supercomputers. ANSYS features file compatibility throughout the family of products and across 

all platforms. The multiphysics nature of ANSYS allows the same model to be used for a variety 

of coupled-field applications such as thermal-structural, magneto-structural, and electricalmagnetic-flow-thermal. 

For both new and experienced users, the program offers a growing list of capabilities including 

advanced structural nonlinearities, electromagnetics, computational fluid dynamics, interactive 

design optimization, general contact surfaces, adaptive meshing, p-method adaptivity, large 

strain/finite rotation capability, and parametric modeling. The Motif-based menu system prompts 

data input and function selections through dialog boxes, pull-down menus, and submenus 

Evaluation: There seems to be nothing in ALGOR that would preclude a competent user from

developing valid results and reaching valid conclusions about an SMR. 

Evaluation: There seems to be nothing in ADINA that would preclude a competent user from

developing valid results and reaching valid conclusions about an SMR. 
50 

helping users navigate through the program. Solid modeling features include NURBS-based 

geometry representation, geometric primitives, and Boolean operations. 

Discipline - Any of five physical (engineering) disciplines may be solved by the ANSYS

program─structural, thermal, electric, magnetic, and fluid. Note that the user can also solve

multi-field problems in ANSYS that consider the effects of the physical phenomena coupled

together such as temperature and displacement in a thermal-stress analysis. 

Analysis Type - Static, modal, harmonic, transient, spectrum, eigenvalue buckling, and

substructuring. Whether the problem is linear or nonlinear will be identified here. 

Element Types Used - Over 100 element types are available in ANSYS. The user chooses an

element type that characterizes, among other things, the degree-of-freedom set (displacements

and/or rotations, temperatures, etc.); the characteristic shape of the element (line, quadrilateral,

brick, etc.); whether the element lies in 2-D space or 3-D space; the response of the user’s

system; and the accuracy level of interest. 

Material Properties - Physical properties of a material such as modulus of elasticity or density

that are independent of geometry. Although they are not necessarily tied to the element type,

the material properties required to solve the element matrices are listed for each element type

for your convenience.

2.2.6.5 GT STRUDL

GT-STRUDL (Georgia Tech STRUctural Design Language) is one of a family of FEM codes. It

was developed in 1975 and is a general purpose finite element analysis program for static and

dynamic analysis of two- and three-dimensional linear and nonlinear structures. The program

continues to be developed by the Georgia Tech Computer-Aided Structural Engineering Center. 

Key features of GT-STRUDL include: 

 Powerful menu driven graphical Windows® NT/98/2000/ME/XP interface. 

 Broad range of nonlinear analysis features, structural definition, and modeling

capabilities. 

 Library of over 100 member and finite element types. 

 Powerful menu-driven mesh generation. 

 Built-in Model Wizard for the fast creation of many common structural models. 

 Generalized automatic data generation for all classes of structural information. 

 Data sheets to define/view/edit/sort information in a spreadsheet format. 

Evaluation: There seems to be nothing in ANSYS that would preclude a competent user from

developing valid results and reaching valid conclusions about an SMR. 
51 

 Efficient static and dynamic (response spectrum, transient, harmonic, and steady 

state) analysis processing. 

 Tools to help locate model instabilities. 

 Sophisticated and highly efficient equation solvers. 

 Comprehensive steel and reinforced concrete structure design according to a variety 

of design code specifications. 

 Offshore platform analysis and design. 

 Design provides for a high level of user control of the result dependent and iterative 

analysis/design/display/evaluation/reanalysis/redesign/decisionmaking process. 

 Problem database inquiry and display features for easy database interaction. 

 User controlled database management facilities including database storage, retrieval, 

and updating features. 

– Static and animated displays of deformed structure, mode shapes, and transient

response, stress contours. 

– Force and moment diagrams and envelopes. 

– Steel code check pass/fail status and interaction values. 

 Display graphical display of results. 

Broad range of member and finite-element types for fame and continuous mechanics 

GT STRUDL contains a large library of member and finite element types consisting of 7 member

types (constant or variable cross-section); over 100 conventional, isoparametric, and hybrid

formulation finite element types; and many special transition elements including: 

 Plane truss/frame/grid and space truss/frame members. 

 Curved plane and space frame member element including internal pressure effects. 

 Plate-bending elements to model thin to moderately thick plates (three, four, and eight 

node triangles and quadrilaterals). 

 3-D solids (6 to 20 node triangular prisms and straight and curved edge bricks). 

 Thin shell elements (three and four node triangles and quadrilaterals with five or six 

degrees-of-freedom per node). 

 Axisymmetric elements (four to eight node quadrilaterals) for modeling solids of 

revolution. 
52 

 Large library of special transition elements for plane stress, plane strain, axisymmetric 

stress (four to eight node quadrilaterals), and 3-D solid (8 to 20 node bricks) problems. 

 Special finite element for modeling shear walls and floor slabs where a rotational 

degree-of-freedom is provided about an axis normal to the element to allow coupling of

member rotational degrees-of-freedom with the element (e.g., beam bending may now

be coupled with a shear wall). 

 Multilevel superelements (i.e., sub-structures defined from user specified collections of

members, finite elements, and other superelements) may be defined for large and

complex linear static analysis problems. 

2.2.6.6 LS-DYNA

LS-DYNA is one of a family of finite element codes. It is a general-purpose finite element

program capable of simulating complex real world problems. The code’s origins lie in highly

nonlinear, transient dynamic finite element analysis using explicit time integration. 

LS-DYNA consists of a single executable file and is entirely command line driven. Therefore, all

that is required to run LS-DYNA is a command shell, the executable, an input file, and enough

free disk space to run the calculation. All input files are in simple ASCII format and thus can be

prepared using any text editor. Input files can also be prepared with the aid of a graphical

preprocessor. 

Capabilities 

LS-DYNA's analysis capabilities include full 2-D & 3-D capabilities; nonlinear dynamics; rigid

body dynamics; quasi-static simulations; normal modes; linear statics; thermal analysis; fluid

analysis (Eulerian capabilities, Arbitrary Lagrangian-Eulerian, Fluid-Structure Interaction, NavierStokes fluids, and compressible fluid solver); FEM-rigid multi-body dynamics coupling

(MADYMO, Cal3D); underwater shock; failure analysis; crack propagation; real-time acoustics;

implicit springback; multi-physics coupling; structural-thermal coupling; adaptive remeshing; SPH 

(Smoothed Particle Hydrodynamics); EFG (Element Free Galerkin); radiation transport; and EM 

(Electromagnetism). 

Material Library 

LS-DYNA's material library includes metals, plastics, glass, foams, fabrics, elastomers,

honeycombs, concrete and soils, viscous fluids, and user-defined materials. 

Element Library 

LS-DYNA's element library includes beams (standard, trusses, discrete, cables, and welds) (with 

over 10 beam element formulations); discrete elements (springs and dampers); lumped inertias; 

lumped masses; accelerometers; sensors; seatbelts; pretensioners; retractors; sliprings; shells 

(3-, 4-, 6-, and 8-node including 3D shells, membranes, 2D plane stress, plane strain, and 

axisymmetric solids with over 25 shell element formulations); solids (4- and 10-node

tetrahedrons, 6-node pentahedrons, and 8-node hexahedrons, with over 20 solid element

formulations); SPH Elements, and thick shells (8-node). 

Evaluation: There seems to be nothing in GT-STRUDL that would preclude a competent user

from developing valid results and reaching valid conclusions about an SMR. 
53 

2.2.6.7 NASTRAN

NASTRAN is a finite element analysis (FEA) program that was originally developed with NASA

funding in the late 1960s for the aerospace industry. The MacNeal-Schwendler Corporation

(MSC) was one of the principal and original developers of the public domain NASTRAN code.

NASTRAN source code is integrated in a number of different software packages, which are

distributed by a range of companies. 

Commercial versions of NASTRAN are currently available from MSC Software, NEi Software

(NEi Nastran), and Siemens PLM Software (NX Nastran). In 2006, Siemens AG purchased the

former UGS Corp. from private equity concerns and with it their rights to the commercial version

of NX NASTRAN. 

MSC Nastran offers a complete set of linear static and dynamic analysis capabilities along with

unparalleled support for superelements enabling users to solve large, complex assemblies more

efficiently. MSC Nastran also offers a complete set of implicit and explicit nonlinear analysis

capabilities, thermal and interior/exterior acoustics, and coupling between various disciplines

such as thermal, structural, and fluid interaction. New modular packaging also exists. 

2.2.6.8 SAP2000

SAP2000 is a general purpose finite element analysis program for static and dynamic analysis of 

two- and three-dimensional linear and nonlinear structures with a particular emphasis on

dynamic loading and earthquake loading. The software is developed by Computers and

Structures, Inc. Integrated design code features can automatically generate wind, wave, bridge,

and seismic loads with comprehensive automatic steel and concrete design code checks per

U.S., Canadian, and international design standards. 

Advanced analytical techniques allow for step-by-step large deformation analysis, Eigen and Ritz 

analyses based on stiffness of nonlinear cases, catenary cable analysis, material nonlinear

analysis with fiber hinges, multi-layered nonlinear shell element, buckling analysis, progressive

collapse analysis, energy methods for drift control, velocity-dependent dampers, base isolators,

support plasticity, and nonlinear segmental construction analysis. Nonlinear analyses can be

static and/or time history with options for FNA nonlinear time history dynamic analysis and direct

integration. 

SAP2000 Features 

Modeling 

Object-Based Graphical Interface; Model Templates with Auto Meshing; Frame, Cable and

Tendon Members; Area (Shell) and Solid Objects with Internal Meshing; Editing with Move,

Merge, Mirror and Replicate; Accurate Dimensioning with Guidelines and Snapping; Auto Edge

Constraints for Mismatched Shell Meshes; Quick Draw Options for Object Creation; Support for 

 

Evaluation: There seems to be nothing in NASTRAN that would preclude a competent user from 

developing valid results and reaching valid conclusions about an SMR. 

Evaluation: There seems to be nothing in LS-DYNA that would preclude a competent user from

developing valid results and reaching valid conclusions about an SMR. 
54 

Multiple Coordinate Systems; Powerful Grouping and Selection Options; Automatic Generation of 

Code Defined Lateral Wind and Seismic Loads; and Transfer of Loads from Area Objects to

Framing Systems.

Analysis 

Static Analysis with Frame and Shell Objects; Multiple Solvers for Analysis Optimization;

Response Spectrum Analysis with Eigen or Ritz Vectors; P-Delta Analysis; Generalized Joint

Constraints including Rigid Bodies and Diaphragms; Applied Force and Displacement Loading;

Gravity, Pressure and Thermal Loading; Post Tensioning in Frame, Area and Solid Objects;

Layered Shell Element; Plane, Asolid and Solid Objects; Dynamic Time History Analysis,

including Multiple Base Excitation; Frequency Domain Analysis-Power Spectral Density; Moving

Loads (requires Bridge Module); Nonlinear Frame Hinges for Axial, Flexural, Shear & Torsional

Behavior; Nonlinear Static Pushover Analysis; Viscous Dampers; Base Isolators; Gap Object for

Structural Pounding; and Nonlinear Time History Analysis with the Wilson FNA or Direct

Integration Methods. 

Design 

Steel Frame Design for Numerous Domestic & International Codes; Concrete Frame Design for

Numerous Codes; Aluminum Frame Design for AA Codes; Cold-Formed Steel Frame Design for

AISI Codes; Design for Static and Dynamic Loads; and Member Selection and Optimization. 

2.2.6.9 SASSI

SASSI, a System for Analysis of Soil-Structure Interaction, consists of a number of interrelated

computer program modules that can be used to solve a wide range of dynamic soil-structure

interaction problems in two or three dimensions. The basic methods of analysis adopted by the

computer program SASSI2000 are called the flexible volume and the recently developed

subtraction methods. These methods are formulated in the frequency domain using the complex 

response method and the finite element technique. 

Complex Response Method: In SASSI, the soil material properties are represented by the

complex shear, G*, and complex constrained moduli, M*, defined by the following equations: 

where G and M are real numbers corresponding to the shear and constrained moduli,

respectively, and βs and βp are the critical damping ratios associated with S-wave and P-waves,

respectively. Currently, only limited data are available on the ratio between βs and βp, and these

quantities are therefore usually chosen to be equal in which case the subscripts are dropped and 

the corresponding Poisson's ratio becomes real number. 

Evaluation: There seems to be nothing in SAP2000 that would preclude a competent user from

developing valid results and reaching valid conclusions about an SMR. 
55 

Using the complex modulus described above, the spatial variation of damping can be included in 

the analysis. This is particularly important for SSI systems in which the material damping in the 

soil and structure is significantly different. 

Capabilities and limitations of SASSI 2000 

Soil and Structure Idealization 

1. The site consists of semi-infinite elastic or viscoelastic horizontal layers on a rigid base 

or a semi-infinite elastic or viscoelastic half space. 

2. The structure(s) are idealized by standard two- or three-dimensional finite elements 

connected at nodal points. 

3. Each nodal point on the structure may have up to six displacement degrees of freedom. 

The user has the option to delete one or more of the degrees of freedom thereby 

reducing the size of the problem accordingly. 

4. The excavated soil zone(s) are idealized by standard plane strain or three-dimensional 

solid elements. The finite element models of the structure and excavated soil have 

common nodes at the boundary. 

5. Depending on the method selected for impedance analysis, the interaction between the 

foundation and the structure occurs at all basement nodes, including those in the 

basement volume, or occurs only at the common boundary nodes. 

6. All the interaction nodes lie on the soil layer interfaces with translational 

7. degree-of-freedom. Rotations from the structure are transferred by translation by 

connecting at several interacting nodes. 

8. The mass matrix is assumed to be 50 percent lumped and 50 percent consistent 

except for the structural beam elements and plate elements where consistent mass 

matrix and lump mass matrix are used, respectively. 

9. Material damping is introduced by the use of complex moduli, which leads to effective 

damping ratios that are frequency-independent and may vary from element to element. 

Discussion of recently discovered validation and verification issues with SASSI 

In the course of using SASSI for analysis of seismic soil-structure interaction for various 

Department of Energy (DOE) nuclear facilities, some technical problems were identified with the 

code, in particular, certain validation and verification (V&V) issues. These are described in a 

U.S. Defense Nuclear Safety Board (DNFSB) letter.* The DNFSB letter cited analysis problems 

for which SASSI supposedly produces unrealistic seismic responses. This discovery has led to 

an extensive program for the verification and validation of SASSI. The two-phase V&V 

* U.S. Defense Nuclear Facilities Safety Board, letter to D. B. Poneman (Deputy Secretary of Energy, 

DOE), April 8, 2011, with an attached “DNFSB Staff Issue Report” entitled “Issues Related to the SASSI 

Computer Software” 

 
56 

program is intended to perform V&V for the SASSI direct method and to provide a technical 

review of aspects of the subtraction method including analysis problems that have been 

identified by practitioners. The program is being performed for DOE and could provide guidance 

to the nuclear power industry as well if the full range of parameters is expanded to encompass 

those of nuclear power plant sites and structure configurations. The program is being executed 

by a single firm but with significant contributions from the combined body of SSI experts and 

SASSI practitioners. The program is continuing at the time of this writing. 

Although these issues have not yet been fully resolved, it is apparent that the problem is 

manifested particularly (or more severely) for the analysis of certain types of embedded 

structures. 

It is still too soon to be able to cite a full “resolution” of this issue for SASSI. Until that occurs, 

there may be a reason to be wary of using SASSI for an embedded structure, whether it be an 

SMR, a large LWR, or any other such facility, without great care. 

2.2.6.10 SHAKE91

SHAKE91, modified based on SHAKE, has been by far the most widely used program for

computing the seismic response of horizontally layered soil deposits. The program computes

the response of a semi-infinite horizontally layered soil deposit overlying a uniform half-space

subjected to vertically propagating shear waves. The algorithm in the program is based on the

continuous solution to the wave equation that was adapted for transient motions using the Fast

Fourier Transform techniques of Cooley and Tukey. The analysis is done in the frequency

domain and, therefore, for any set of properties, it is a linear analysis. An iterative procedure is

used to account for the nonlinear behavior of the soils. 

When performing SHAKE91, users need to define the soil properties for each sub-layer(shearwave velocity, shear modulus, damping, total weight, and thickness) and select the input

motions. In addition, the modulus reduction versus shear strain relationship and damping ratio

versus shear strain relationship must be specified to represent the soil material properties. An

equivalent linear analysis procedure is implemented in SHAKE91 to account for nonlinear

response of soil. The outputs of the program are the time histories requested by users. In

addition, many associated types of data can be outputted, upon users’ request, such as the

maximum shear stress and strain, maximum acceleration, response spectrum, Fourier spectrum, 

and amplification spectrum. 

2.2.6.11 SIMQKE-1

SIMQKE-1 generates statistically independent accelerograms, performs a baseline correlation

on the generated motions to ensure zero final ground velocity, and calculates response spectra.

One of the options in the program generates ground motions whose response spectra “match,”

Evaluation: There seems to be nothing in SHAKE91 that would preclude a competent user from

developing valid results and reaching valid conclusions about an SMR. 

Evaluation: Except for the aforementioned issue of verification and validation for SASSI and

except for using SASSI with embedded structures (which issues await a broader resolution), there 

seems to be nothing in SASSI that would preclude a competent user from developing valid results 

and reaching valid conclusions about an SMR. 
57 

or are compatible with, a set of specified smooth response spectra. The basis for the spectrum

compatible motion generation is the relationship between the response spectrum values for

arbitrary damping and the “expected” Fourier amplitudes of the ground motion. The earthquakes 

are synthesized by superimposing sinusoidal components with pseudo-random phase angles 

and by multiplying the resulting stationary trace by a user specified function representing the 

variation of ground motion intensity with time. The program SIMQKE-1 also has the capability to 

adjust, by iteration, the ordinates of the spectral density function to improve the agreement 

between computed and specified response spectra. Even without the last step, the average 

response spectrum (of a set of simulated motions) will match the smooth target spectrum very 

closely. 

SIMQKE-1 uses target response spectra as input that can be developed for nuclear power plants 

according to NRC’s RG 1.208, “A Performance-Based Approach to Define the Site-Specific 

Earthquake Ground Motion,” or RG 1.60, “Monitoring the Effectiveness of Maintenance at 

Nuclear Power Plants,” and the outputs are artificial earthquake motions. 

2.2.6.12 STARDYNE

STARDYNE, now known as STAAD, is a finite element structural analysis and design computer

program originally developed by Research Engineers International in Yorba Linda, CA. In late

2005, Research Engineer International was bought by Bentley Systems. 

It supports several steel, concrete, and timber design codes. It can make use of various forms of 

analysis from the traditional first order static analysis, second order p-delta analysis, geometric 

nonlinear analysis, or a buckling analysis. It can also make use of various forms of dynamic 

analysis from modal extraction to time history and response spectrum analysis. 

Key Feature List: 

 Flexible modeling is provided by a state-of-the-art graphical environment and the 

design supports over 70 international codes and over 20 U.S. codes in 7 languages. 

 An array of advanced structural analysis and design features are included such as 

nuclear certification for 10 CFR Part 50, 10 CFR 21, ASME NQA-1-2000, time history 

and push over analysis and cable (linear and nonlinear) analysis. 

 Concurrent engineering-based user environment for model development, analysis, 

design, visualization, and verification. 

 Full range of structural analysis including static, P-delta, pushover, response 

spectrum, time history, cable (linear and nonlinear), buckling and steel, concrete and 

timber design. 

 Optional Advanced Analysis engine. A new substantially faster solver that can provide 

solutions of large structures in a fraction of the time currently required by the standard 

STAAD engine. The Advanced Solver generally uses less disk and memory. 

Evaluation: There seems to be nothing in SIMQKE-1 that would preclude a competent user from

developing valid results and reaching valid conclusions about an SMR. 
58 

 Supports truss and beam members, plates, solids, linear and nonlinear cables, and 

curvilinear beams. 

 Advanced automatic load generation facilities for wind, area, floor, and moving loads. 

 Efficiencies are gained through the ability to maintain and streamline current 

workflows with fluent data collaboration. STAAD.Pro integrates with other Bentley 

products such as STAAD.foundation and ProSteel, and OpenSTAAD is provided for 

integration with third party programs. 

2.2.7 ESSI

The NRC ESSI (“Earthquake Soil-Structure Interaction”) Program has been under development

at LBNL and the University of California at Davis, supported by the NRC, and directed by Prof.

Boris Jeremic. It is not yet in widespread use. 

The evaluation of ESSI vis-à-vis SMRs was performed separately by Dr. Jeremic. 

ESSI is a time domain, nonlinear, parallel finite element program for simulating 

earthquake-soil-structure interaction of nuclear power plants (NPPs). The program is developed 

using a number of (open source) libraries that are compiled and linked into an application 

program. The program uses a number of state-of-the-art methods to analyze nonlinear behavior 

of soils, rock, concrete, steel, and other materials used. A number of finite elements are 

available for modeling, namely, solids (8, 20, 20-17, 27 node bricks, etc.) as well as truss, 

beam, and shell elements. Solid finite elements can model behavior of a single-phase (dry) 

material and/or behavior of two-phase (fully saturated) material (soil). Special finite elements are 

available to model gap (opening/closing) and slipping, seismic isolators, etc. Seismic input is 

performed using the Domain Reduction Method, which provides a way to analytically input body 

(primary (P) and secondary (S)) and surface (Rayleigh, Love, etc.) seismic waves and provides 

for analytic radiation damping. The NRC ESSI Program has an extensive ongoing verification 

and validation suite whose goal is to cover all modeling and simulation components. 

The ESSI Program analyzes a finite element model of soil/rock and the NPP using the direct 

method, where all the components are present in the model at all times and are modeled and 

simulated using physics-based methods. There is no difference in modeling if the model of the 

NPP is on the surface, slightly embedded, or fully embedded; all the components are modeled 

at once. They are fully coupled in the sense that they fully interact through their respective 

stiffness, damping, and mass matrices at each time step of the simulations, and all of the 

interactions are fully accounted for at each time step. There is no difference in modeling and 

simulation that depends on whether a large NPP or an SMR in being modeled because there is

no modeling dependence on the dimensions or mass of the structure. 

 

Evaluation: There seems to be nothing in the ESSI analysis program that would preclude a

competent user from developing valid results and reaching valid conclusions about an SMR. 

Evaluation: There seems to be nothing in STARDYNE that would preclude a competent user

from developing valid results and reaching valid conclusions about an SMR. 
59 

2.3 Summary for Section 2 

The evaluation in Section 2 of this report has presented an evaluation of simulation tools that

can analyze seismic issues as used in structural engineering, geotechnical engineering, and

seismic engineering. The evaluation has ascertained whether each simulation tool could be

used for the analysis of a small modular reactor (SMR) for regulatory purposes. The evaluation

has found that, in every case, there seems to be nothing in the simulation tool that would 

preclude a competent user from developing valid results and reaching valid conclusions about an 

SMR. 







NUREG/CR-7193 Evaluations of NRC Seismic-Structural Regulations and Regulatory Guidance, and 

Simulation-Evaluation Tools for Applicability to Small Modular Reactor (SMRS)