Structures, systems, and components of a nuclear power plant that are designated as Seismic Category I are designed 1

to withstand the effects of the safe shutdown earthquake (SSE) and remain functional, see Regulatory Guide 1.29,

“Seismic Design Classification.”

Appendix S to 10 CFR Part 50 applies to applicants for a design certification or combined license pursuant to 2

10 CFR Part 52, “Early Site Permits; Standard Design Certifications; and Combined Licenses for Nuclear Power Plants,”

or a construction permit or operating license pursuant to 10 CFR Part 50 after January 10, 1997. However, for either

an operating license applicant or holder whose construction permit was issued before January 10, 1997, the earthquake

engineering criteria in Section VI of Appendix A to 10 CFR Part 100 continue to apply.

The U.S. Nuclear Regulatory Com m ission (NRC) issues regulatory guides to describe and m ake available to the public m ethods that the NRC staff

considers acceptable for use in im plem enting specific parts of the agency’s regulations, techniques that the staff uses in evaluating specific problem s

or postulated accidents, and data that the staff need in reviewing applications for perm its and licenses. Regulatory guides are not substitutes

for regulations, and com pliance with them is not required. Methods and solutions that differ from those set forth in regulatory guides will be deem ed

acceptable if they provide a basis for the findings required for the issuance or continuance of a perm it or license by the Com m ission.

This guide was issued after consideration of com m ents received from the public. The NRC staff encourages and welcomes comm ents and suggestions

in connection with im provem ents to published regulatory guides, as well as item s for inclusion in regulatory guides that are currently being developed. 

The NRC staff will revise existing guides, as appropriate, to accom m odate com m ents and to reflect new inform ation or experience. W ritten com m ents

m ay be submitted to the Rules and Directives Branch, Office of Adm inistration, U.S. Nuclear Regulatory Com m ission, W ashington, DC 20555-0001.

Regulatory guides are issued in 10 broad divisions: 1, Power Reactors; 2, Research and Test Reactors; 3, Fuels and Materials Facilities;

4, Environm ental and Siting; 5, Materials and Plant Protection; 6, Products; 7, Transportation; 8, Occupational Health; 9, Antitrust and Financial Review;

and 10, General.

Requests for single copies of draft or active regulatory guides (which m ay be reproduced) should be made to the U.S. Nuclear Regulatory Com m ission,

W ashington, DC 20555, Attention: Reproduction and Distribution Services Section, or by fax to (301) 415-2289; or by email to Distribution@nrc.gov.

Electronic copies of this guide and other recently issued guides are available through the NRC’s public W eb site under the Regulatory Guides document

collection of the NRC’s Electronic Reading Room at http://www.nrc.gov/reading-rm /doc-collections/ and through the NRC’s Agencywide Docum ents

Access and Managem ent System (ADAMS) at http://www.nrc.gov/reading-rm /adam s.htm l, under Accession No. ML070260029.

U.S. NUCLEAR REGULATORY COMMISSION March 2007

Revision 1

REGULATORY GUIDE

OFFICE OF NUCLEAR REGULATORY RESEARCH

REGULATORY GUIDE 1.61

(Draft was issued as DG-1157, dated October 2006)

DAMPING VALUES FOR SEISMIC DESIGN

OF NUCLEAR POWER PLANTS

A. INTRODUCTION

This regulatory guide is being revised to update the guidance for applicants and licensees

regarding the acceptable damping values that the U.S. Nuclear Regulatory Commission (NRC) staff used

in the seismic response analysis of Seismic Category I nuclear power plant structures, systems, 1

and components (SSCs) in accordance with Title 10, Part 50, of the Code of Federal Regulations

(10 CFR Part 50), “Domestic Licensing of Production and Utilization Facilities” [Ref. 1].

Specifically, General Design Criterion 2, “Design Bases for Protection Against Natural Phenomena,”

of Appendix A, “General Design Criteria for Nuclear Power Plants,” to 10 CFR Part 50 requires that

SSCs important to safety be designed to withstand the effects of natural phenomena such as earthquakes

without losing the ability to perform their safety functions. Such SSCs must also be designed

to accommodate the effects of and be compatible with the environmental conditions associated with

normal operation and postulated accidents. Appendix S, “Earthquake Engineering Criteria for Nuclear

Power Plants,” to 10 CFR Part 50 specifies the requirements for the implementation of General Design

Criterion 2 with respect to earthquakes.2
Rev. 1 of RG 1.61, Page 2

This regulatory guide specifies the damping values that the NRC staff considers acceptable

for complying with the agency’s regulations and guidance for seismic analysis. The specified damping

values are intended for elastic modal dynamic seismic analysis where energy dissipation is accounted for

by viscous damping (i.e., the damping force is proportional to the velocity).

This regulatory guide contains information collections that are covered by the requirements

of 10 CFR Part 50, which the Office of Management and Budget (OMB) approved under OMB control

number 3150-0011. The NRC may neither conduct nor sponsor, and a person is not required to respond to,

an information collection request or requirement unless the requesting document displays a currently

valid OMB control number.

B. DISCUSSION

Background

Damping is a measure of the energy dissipation of a material or structural system as it responds to

dynamic excitation. It is a term used to assist in mathematically modeling and solving dynamic equations

of motion for a vibratory system in which energy is dissipated. When performing an elastic dynamic

seismic analysis, one can account for the energy dissipated by specifying the amount of viscous damping

(i.e., damping force proportional to the velocity) in the analytical model.

Current NRC guidance on damping values to be used in the elastic design of nuclear power plants

is presented in this regulatory guide, which was first issued in October 1973 [Ref. 2]. Like the original

version of this guide, this revision specifies equivalent viscous modal damping values as a percentage

of critical damping for Seismic Category I SSCs. However, the staff based the original damping values

on limited data, expert opinion, and other information available in 1973. Since that time, the NRC

and industry have been involved in various studies, research work, and testing to predict and estimate

damping values of SSCs. In view of the available data, the damping values provided in the original

version of Regulatory Guide 1.61 may not reflect realistic damping values for SSCs. Also, it is recognized

that additional guidance is needed to address issues, such as correlation between damping and structures

stress level, and damping values for materials not included in the original version of Regulatory Guide 1.61

(e.g., electrical distribution systems and reinforced masonry structures).

Over the past three decades, the nuclear industry has proposed damping values and discussed

these values during various meetings and reviews of licensing issues. Nuclear industry groups and licensees

have suggested that the NRC ought to accept more realistic damping values for seismic design and analysis

of SSCs, in place of the damping values provided in the original Regulatory Guide 1.61.

Structural Damping

In 1993, the NRC completed an investigation of the adequacy of original Regulatory Guide 1.61

structure damping values and other recommendations, and reported the results in NUREG/CR-6011 [Ref. 3]. 

Data were analyzed to identify the parameters that significantly influenced structure damping. Based on

that study, the NRC determined that the original Regulatory Guide 1.61 damping values for structure design

were adequate but required one significant revision. Specifically, Regulatory Guide 1.61 should distinguish

between “friction-bolted” and “bearing-bolted” connections for steel structures. Friction-bolted connections

are also referred to as “slip-critical” connections. In these connections, the bolt preload is high enough

to ensure that friction is not overcome, and the bolt does not experience shear loading. Regulatory

Position 1 in Section C of this revised guide provides the updated structural damping values.
Rev. 1 of RG 1.61, Page 3

Piping Damping

In 1986, the American Society of Mechanical Engineers (ASME) established Code Case N-411,

“Alternative Damping Values for Response Spectra Analysis of Class 1, 2, and 3 Piping,” in Section III,

Division 1, of the ASME Boiler and Pressure Vessel Code [Ref. 4]. The NRC staff used Code Case N-411,

with certain limitations specified in Regulatory Guide 1.84 [Ref. 5], to review operating reactor issues

until Code Case N-411 expired in 2000. The staff also approved the use of alternate damping values

for the General Electric Advanced Boiling Water Reactor Design in 1994 [Ref. 6], Combustion Engineering

System 80+ Design in 1992 [Ref. 7], and Westinghouse AP600 Design in 1998 [Ref. 8]. Regulatory

Position 2 in Section C of this revised guide provides the piping damping values that resulted from

the staff’s experience with ASME Code Case N–411 and application reviews of new reactor designs.

Electrical Distribution System Damping

Regulatory Guide 1.61 did not originally provide damping values for cable tray or conduit systems. 

Historically, the nuclear power industry used the damping values for bolted steel structures for seismic

design of cable tray and conduit systems. In the late 1980s, however, the NRC staff reviewed the results

of the cable tray test at the Comanche Peak Steam Electrical Station [Ref. 9]. Regulatory Position 3

in Section C of this revised guide provides the damping values that resulted from the staff’s review

of data from the Comanche Peak test [Ref. 10] and two safety evaluation reports [Refs. 9, 11].

Heating Ventilation and Air Conditioning Duct Damping

The damping values for heating ventilation and air conditioning (HVAC) systems are consistent

with the guidance provided for bolted steel structures. Because no tests of welded duct construction

have been identified, the damping values are the same as for welded steel structures, and Regulatory

Position 4 in Section C of this revised guide provides these same damping values. In addition, the NRC

provides related information on HVAC duct damping in NUREG/CR-6919, “Recommendations

for Revision of Seismic Damping Values in Regulatory Guide 1.61” [Ref. 12].

Mechanical and Electrical Component Damping

NUREG/CR-6919 [Ref. 12] considers guidance in American Society of Civil Engineers (ASCE)

Standard 43-05, “Seismic Design Criteria for Structures, Systems, and Components in Nuclear Facilities”

[Ref. 13], and Non-Mandatory Appendix N, “Dynamic Analysis Methods,” to Section III, Division 1,

of the ASME Boiler & Pressure Vessels Code [Ref. 14]. In addition, NUREG/CR-6919 [Ref. 12]

provides recommendations and commentary on damping values for (1) containment structures,

containment internal structures, and other Seismic Category I structures; (2) piping; (3) electrical

distribution systems (i.e., cable tray or conduit systems); (4) HVAC; and (5) mechanical and electrical

components. Regulatory Position 5 in Section C of this revised guide provides the damping values

that resulted from the staff’s review of this industry guidance.
Rev. 1 of RG 1.61, Page 4

C. REGULATORY POSITION

The following regulatory positions provide acceptable damping values to be used in the elastic

dynamic seismic analysis and design of SSCs, where energy dissipation is approximated by viscous damping

unless otherwise specified. Damping values higher than those provided may be used if documented

test data support the higher values. Damping values associated with soil-structure interaction analysis

are not within the scope of this regulatory guide.

1. Structural Damping

1.1 Acceptable Structural Damping Values for Containment Structures,

Containment Internal Structures, and Other Seismic Category I Structures

1.1.1 Safe-Shutdown Earthquake (SSE)

Table 1 provides acceptable damping values for the SSE analysis.

Table 1. SSE Damping Values

Structural Material Damping (% of Critical Damping)

Reinforced Concrete 7%

Reinforced Masonry 7%

Prestressed Concrete 5%

Welded Steel or Bolted Steel with Friction Connections 4%

Bolted Steel with Bearing Connections 7%

Note: For steel structures with a combination of different connection types, use the lowest specified damping value, or as

an alternative, use a “weighted average” damping value based on the number of each type present in the structure.

1.1.2 Operating-Basis Earthquake (OBE)

If the design-basis OBE ground acceleration is selected to be less than or equal to one-third

of the design-basis SSE ground acceleration, then a separate OBE analysis is not required. However,

if the design-basis OBE ground acceleration is selected to be greater than one-third of the design-basis

SSE ground acceleration, then a separate OBE analysis should be conducted. Table 2 provides acceptable

damping values for the OBE analysis.

Table 2. OBE Damping Values

Structural Material Damping (% of Critical Damping)

Reinforced Concrete 4%

Reinforced Masonry 4%

Prestressed Concrete 3%

Welded Steel or Bolted Steel with Friction Connections 3%

Bolted Steel with Bearing Connections 5%
Rev. 1 of RG 1.61, Page 5

1.2 Special Consideration for In-Structure Response Spectra Generation

The SSE damping values specified in Table 1 for linear dynamic analysis of structures

have been selected based on the expectation that the structural response attributed to load combinations

that include SSE will be close to applicable code stress limits, as defined in Section 3.8 of NUREG-0800

[Ref. 15].

However, there may be cases where the predicted structural response to load combinations

that include SSE is significantly below the applicable code stress limits. Because equivalent viscous

damping ratios have been shown to be dependent on the structural response level, it is necessary

to consider that the SSE damping values specified in Table 1 may be inconsistent with the predicted

structural response level.

For structural evaluation, this is not a concern, because the stresses resulting from the use

of damping-compatible structural response will still be less than the applicable code stress limits,

as defined in Section 3.8 of NUREG-0800 [Ref. 15].

However, for in-structure response spectra generation, it is necessary to use the damping-compatible

structural response. Consequently, the following additional guidance is provided for analyses used

to determine in-structure response spectra:

(1) Use the OBE damping values specified in Table 2, which are acceptable to the staff

without further review.

(2) Submit a plant-specific technical basis for use of damping values higher than the OBE damping

values specified in Table 2, but not greater than the SSE damping values specified in Table 1

(e.g., see NUREG/CR-6919, Section 3.2.3), subject to staff review on a case-by-case basis.

In general, for certified standard plant designs where the design-basis in-structure response spectra

represent the envelope of the in-structure responses obtained from multiple analyses conducted

to consider a range of expected site soil conditions, it is not necessary for combined license applicants

to address this issue. However, if plant-specific seismic analyses are conducted for Category I structures

and/or structures not included as part of the standard plant design, then the applicant is expected

to address this issue accordingly.
Rev. 1 of RG 1.61, Page 6

2. Piping Damping

Table 3 presents the constant damping values specified for SSE and OBE (where required)

analyses of piping systems. These values are applicable to time-history, response spectra,

and equivalent static analysis procedures for structural qualification.

Table 3. Damping Values for Piping Systems

Category

Damping Value

SSE OBE > SSE/3

Piping Systems 4% 3%

As an alternative for response spectrum analyses using an envelope of the SSE or OBE response

spectra at all support points (uniform support motion), frequency-dependent damping values shown

in Figure 1 may be used, subject to the following restrictions:

• Frequency-dependent damping should be used completely and consistently, if at all. 

(Damping values specified in Regulatory Guide 1.61 are to be used for equipment

other than piping.)

• Use of the specified damping values is limited only to response spectral analyses. 

Acceptance of the use of the specified damping values with other types of dynamic analyses

(e.g., time-history analyses or independent support motion method) requires further justification.

• When used for reconciliation or support optimization of existing designs, the effects of increased

motion on existing clearances and online mounted equipment should be checked.

• Frequency-dependent damping is not appropriate for analyzing the dynamic response of piping

systems using supports designed to dissipate energy by yielding.

• Frequency-dependent damping is not applicable to piping in which stress corrosion cracking

has occurred, unless a case-specific evaluation is provided and reviewed and found acceptable

by the NRC staff.
Rev. 1 of RG 1.61, Page 7

3. Electrical Distribution System Damping

Table 4 presents the constant damping values specified for SSE and OBE (where required)

analyses of cable tray and conduit systems. These values are applicable to response spectra

and equivalent static analysis procedures for structural qualification. The damping values specified

in Table 4 are applicable to all types of supports, including welded supports. The use of higher damping

values for cable trays with flexible support systems (e.g., rod-hung trapeze systems, strut-hung trapeze

systems, and strut-type cantilever and braced cantilever support systems) is permissible, subject to

obtaining NRC review for acceptance on a case-by-case basis.

The analysis methodology should consider the flexibility of supports in determining the system

response to seismic excitation.
Rev. 1 of RG 1.61, Page 8

Table 4. Damping Values for Electrical Distribution Systems

Category

Damping Value

SSE OBE > SSE/3

Cable Tray System4

Maximum Cable Loading1

Empty2

Sprayed-on Fire Retardant or other

cable-restraining mechanism3

10%

7%

7%

7%

5%

5%

Conduit Systems4

Maximum Cable fill1

Empty2

7%

5%

5%

3%

Notes:

1. Maximum cable loadings, in accordance with the plant design specification, are to be utilized

in conjunction with these damping values.

2. Spare cable tray and conduit, initially empty, may be analyzed with zero cable load and these damping

values. (Note: Re-analysis is expected when put into service.)

3. Restraint of the free relative movement of the cables inside a tray reduces the system damping.

4. When cable loadings of less-than maximum are specified for design calculations, the applicant

or licensee is expected to justify the selected damping values and obtain NRC review for acceptance

on a case-by-case basis.

4. Heating, Ventilation, and Air Conditioning Duct Damping

Table 5 presents the constant damping values specified for SSE and OBE (when required)

analyses of HVAC duct systems. These values are applicable to response spectra and equivalent

static analysis procedures for structural qualification.

The analysis methodology must consider the flexibility of supports in determining system

response to seismic excitation.

Table 5. Damping Values for HVAC Duct Systems

Type of Duct Construction

Damping Value

SSE OBE > SSE/3

Pocket Lock 10% 7%

Companion Angle 7% 5%

Welded 4% 3%
Rev. 1 of RG 1.61, Page 9

5. Mechanical and Electrical Component Damping

Table 6 presents the damping values for mechanical and electrical components, which are

applicable to passive subcomponents that can be seismically qualified by analysis. Active subcomponents

do not readily lend themselves to seismic qualification by analysis, and require qualification by test,

as described in Section 3.10 of NUREG-0800 [Ref. 15].

Table 6. Damping Values for Mechanical and Electrical Components

Component Type

Damping Value

SSE OBE > SSE/3

Motor, Fan, and Compressor Housings

(protection, structural support)

3% 2%

Pressure Vessels, Heat Exchangers,

and Pump and Valve Bodies 

(pressure boundary)

3% 2%

Welded Instrument Racks

(structural support)

3% 2%

Electrical Cabinets, Panels, and Motor

Control Centers (MCCs)

(protection, structural support)

3% 2%

Metal Atmospheric Storage Tanks

(containment, protection)

 — Impulsive Mode

 — Sloshing Mode

3%

0.5%

2%

0.5%
Rev. 1 of RG 1.61, Page 10

D. IMPLEMENTATION

The purpose of this section is to provide information to applicants and licensees regarding

the NRC staff’s plans for using this regulatory guide. No backfitting is intended or approved in

connection with the issuance of this guide.

Except in those cases in which an applicant or licensee proposes or has previously established

an acceptable alternative method for complying with specified portions of the NRC’s regulations,

the NRC staff will use the methods described in this guide to evaluate (1) submittals in connection with

applications for construction permits, standard plant design certifications, operating licenses,

early site permits, and combined licenses; and (2) submittals from operating reactor licensees

who voluntarily propose to initiate system modifications if there is a clear nexus between the proposed

modifications and the subject for which guidance is provided herein.

REGULATORY ANALYSIS / BACKFIT ANALYSIS

The regulatory analysis and backfit analysis for this regulatory guide are available in

Draft Regulatory Guide DG-1157, “Damping Values for Seismic Design of Nuclear Power Plants”

(Ref. 16). The NRC issued DG-1157 in October 2006 to solicit public comment on the draft of this

Revision 1 of Regulatory Guide 1.61.
All NRC regulations listed herein are available electronically through the Electronic Reading Room on the NRC’s

3

public Web site, at http://www.nrc.gov/reading-rm/doc-collections/cfr/part050. Copies are also available for inspection

or copying for a fee from the NRC’s Public Document Room at 11555 Rockville Pike, Rockville, MD; the PDR’s

mailing address is USNRC PDR, Washington, DC 20555; telephone (301) 415-4737 or (800) 397-4209; fax (301)

415-3548; email PDR@nrc.gov.

All regulatory guides listed herein were published by the U.S. Nuclear Regulatory Commission or its predecessor,

4

the U.S. Atomic Energy Commission. Most are available electronically through the Electronic Reading Room

on the NRC’s public Web site, at http://www.nrc.gov/reading-rm/doc-collections/reg-guides/. Single copies of

regulatory guides may also be obtained free of charge by writing the Reproduction and Distribution Services Section,

ADM, USNRC, Washington, DC 20555-0001, by fax to (301) 415-2289, or by email to DISTRIBUTION@nrc.gov.

Active guides may also be purchased from the National Technical Information Service (NTIS). Details may be

obtained by contacting NTIS at 5285 Port Royal Road, Springfield, Virginia 22161, online at http://www.ntis.gov,

by telephone at (800) 553-NTIS (6847) or (703) 605-6000, or by fax to (703) 605-6900. Copies are also available for

inspection or copying for a fee from the NRC’s Public Document Room (PDR), which is located at 11555 Rockville

Pike, Rockville, Maryland; the PDR’s mailing address is USNRC PDR, Washington, DC 20555-0001. The PDR

can also be reached by telephone at (301) 415-4737 or (800) 397-4209, by fax at (301) 415-3548, and by email

to PDR@nrc.gov.

All NUREG-series reports listed herein were published by the U.S. Nuclear Regulatory Commission. Copies are

5

available for inspection or copying for a fee from the NRC’s Public Document Room at 11555 Rockville Pike,

Rockville, MD; the PDR’s mailing address is USNRC PDR, Washington, DC 20555; telephone (301) 415-4737

or (800) 397-4209; fax (301) 415-3548; email PDR@nrc.gov. Copies are also available at current rates from

the U.S. Government Printing Office, P.O. Box 37082, Washington, DC 20402-9328, telephone (202) 512-1800;

or from the National Technical Information Service (NTIS) at 5285 Port Royal Road, Springfield, Virginia 22161,

online at http://www.ntis.gov, by telephone at (800) 553-NTIS (6847) or (703) 605-6000, or by fax to (703) 605-6900.

NUREG-0800 and NUREG/CR-6919 are also available electronically through the Electronic Reading Room

on the NRC’s public Web site, at http://www.nrc.gov/ reading-rm/doc-collections/nuregs/.

Copies may be obtained from the American Society of Mechanical Engineers, Three Park Avenue, New York, NY 6

10016-5990. Phone (212)591-8500; fax (212)591-8501; www.asme.org.

Rev. 1 of RG 1.61, Page 11

REFERENCES

1. U.S. Code of Federal Regulations, Title 10, Part 50, “Domestic Licensing of Production

and Utilization Facilities,” U.S. Nuclear Regulatory Commission, Washington, DC.3

2. Regulatory Guide 1.61, “Damping Values for Seismic Design of Nuclear Power Plants,”

U.S. Atomic Energy Commission, Washington, DC, October 1973.

4

3. NUREG/CR-6011, “Review of Structure Damping Values for Elastic Seismic Analysis of

Nuclear Power Plants,” U.S. Nuclear Regulatory Commission, Washington, DC, March 1993.5

4. “ASME Boiler and Pressure Vessel Code, Code Case N-411-1, Alternative Damping Values

for Response Spectra Analysis of Class 1, 2 and 3 Piping,” Section III, Division 1,

American Society of Mechanical Engineers, New York, New York, February 20, 1986.6

5. Regulatory Guide 1.84, “Design, Fabrication, and Materials Code Case Acceptability —

ASME Section III,” U.S. Nuclear Regulatory Commission, Washington, DC.3

6. NUREG-1503, “Final Safety Evaluation Report Related to the Certification of the Advanced

Boiling-Water Reactor,” U.S. Nuclear Regulatory Commission, Washington, DC, July 1994.4
Copies are available for inspection or copying for a fee from the NRC’s Public Document Room at 11555 Rockville Pike, 7

Rockville, MD; the PDR’s mailing address is USNRC PDR, Washington, DC 20555 (telephone: 301-415-4737

or 800-397-4209; fax: 301-415-3548; email: PDR@nrc.gov).

Copies may be purchased from the American Society for Civil Engineers (ASCE), 1801 Alexander Bell Drive, 8

Reston, VA 20190 [phone: (800) 548-ASCE (2723)]. Purchase information is available through the ASCE Web site

at http://www.pubs.asce.org.

Draft Regulatory Guide DG-1157 is available electronically under Accession #ML062680189 in the NRC’s 9

Agencywide Documents Access and Management System (ADAMS) at http://www.nrc.gov/reading-rm/adams.html. 

Copies are also available for inspection or copying for a fee from the NRC’s Public Document Room (PDR), which is

located at 11555 Rockville Pike, Rockville Maryland; the PDR’s mailing address is USNRC PDR, Washington, DC

20555-0001. The PDR can also be reached by telephone at (301) 415-4737 or (800) 397-4209 by fax

at (301) 415-3548, and by email to PDR@nrc.gov.

Rev. 1 of RG 1.61, Page 12

7. NUREG-1462, “Draft Safety Evaluation Report related to the Design Certification of the System 80+

Design,” U.S. Nuclear Regulatory Commission, Washington, DC, September 1992.4

8. NUREG-1512, “Final Safety Evaluation Report related to Certification of the AP600 Standard

Design,” U.S. Nuclear Regulatory Commission, Washington, DC, September 1998.4

9. NUREG-0797, “Safety Evaluation Report Related to the Operation of Comanche Peak Steam

Electric Station, Units 1 and 2,” Supplement No. 16, U.S. Nuclear Regulatory Commission,

Washington, DC, July 1988.4

10. Ware, A.G., and C.B. Slaughterbeck, “A Survey of Cable Tray and Conduit Damping Research,”

Idaho National Engineering Laboratory, Report No. EGG-EA-7346, Rev. 1, prepared for

the U.S. Nuclear Regulatory Commission, Washington, DC, August 1986.7

11. NUREG-0847, “Safety Evaluation Report for Watts Bar Nuclear Plant, Units 1 and 2,”

Supplement No. 8, U.S. Nuclear Regulatory Commission, Washington, DC, January 1992.4

12. NUREG/CR-6919, “Recommendations for Revision of Seismic Damping Values for the Seismic

Damping Values in Regulatory Guide 1.61,” U.S. Nuclear Regulatory Commission, Washington,

DC, November 2006.4

13. American Society of Civil Engineers, ASCE Standard 43-05, “Seismic Design Criteria

for Structures, Systems, and Components in Nuclear Facilities,” Reston, VA, 2005.8

14. American Society of Mechanical Engineers, “Boiler and Pressure Vessel Code,” Section III,

Division 1, Non-Mandatory Appendix N, “Dynamic Analysis Methods,” New York, New York,

2004.

5

15. NUREG-0800, “Standard Review Plan for the Review of Safety Analysis Reports for Nuclear

Power Plants,” U.S. Nuclear Regulatory Commission, Washington, DC.4

16. Draft Regulatory Guide DG-1157, “Damping Values for Seismic Design of Nuclear Power

Plants,” U.S. Nuclear Regulatory Commission, Washington, DC.9