Regulatory Guide 1.29

Seismic Design Classification

ML003739983
Person / Time
Issue date:	09/30/1978
From:	Office of Nuclear Regulatory Research
To:
References
RG-1.029, Rev 3
Download: ML003739983 (3)

U.S. NUCLEAR REGULATORY COMMISSION

Revision 3 September 1978 REGULATORY GUIDE

OFFICE OF STANDARDS DEVELOPMENT

REGULATORY GUIDE 1.29 SEISMIC DESIGN CLASSIFICATION

A.

INTRODUCTION

General Design Criterion 2, "Design Bases for Protection Against Natural Phenomena," of Appen dix A, "General Design Criteria for Nuclear Power Plants," to 10 CFR Part 50, "Domestic Licensing of Production and Utilization Facilities," requires that nuclear power plant structures, systems, and components important to safety be designed to with stand the effects of earthquakes without loss of capa bility to perform their safety functions.

- Appendix B, "Quality Assurance Criteria for Nu clear Power Plants and Fuel Reprocessing Plants," to

10 CFR Part 50 establishes quality assurance re quirements for the design, construction, and opera tion of nuclear power plant structures, systems, and components that prevent or mitigate the consequences of postulated accidents that could cause undue risk to the health and safety of the publi

c. The pertinent re

• /

quirements of Appendix B apply to all activities af fecting the safety-related functions of those struc tures, systems, and components.

Appendix A, "Seismic and Geologic Siting Criteria for Nuclear Power Plants," to 10 CFR Part

100, "Reactor Site Criteria," requires that all nu clear power plants be designed so that, if the Safe

Shutdown Earthquake (SSE) occurs, certain struc tures, systems, and components remain functional.

These plant features are those necessary to ensure (1)

the integrity of the reactor'coolant pressure boundary,

(2) the capability to shut down the reactor and main tain it in a safe shutdown condition, or (3) the capa bility to prevent or mitigate the consequences of ac cidents that could result in potential offsite exposures comparable to the guideline exposures of 10 CFR

Part 100.

This guide describes a method acceptable to the NRC staff for identifying and classifying those fea- tures of light-water-cooled nuclear power plants that should be designed to withstand the effects of the SSE. The Advisory Committee on Reactor Safeguards has been consulted regarding this guide and has concurred in the regulatory position.

B.

DISCUSSION

After reviewing a number of applications for con struction permits and operating licenses for boiling and pressurized water nuclear power plants, the NRC

staff has developed a seismic design classification system for identifying those plant features that should be designed to withstand the effects of the SSE.

Those structures, systems, and components that should be designed to remain functional if the SSE

occurs have been designated as Seismic Category I.

C.

REGULATORY POSITION

1. The following structures, systems, and compo nents of a nuclear power plant, including their foun dations and supports, are designated as Seismic Cate gory I and should be designed to withstand the effects of the SSE and remain functional. The pertinent qual ity assurance requirements of Appendix B to 10 CFR

Part 50 should be applied to all activities affecting the safety-related functions of these structures, sys tems, and components.

a. The reactor coolant pressure boundary.

b. The reactor core and reactor vessel internals.

c. Systems' or portions of systems that are re quired for (1) emergency core cooling, (2) postacci

• Lines indicate substantive changes from previous issue.

tThe system boundary includes those portions of the system re quired to accomplish the specified safety function and connected piping up to and including the first valve (including a safety or relief valve) that is either normally closed or capable of automatic closure when the safety function is required.

USNRC REGULATORY GUIDES

Comments should be sent to the Secretary of the Commission, U.S. Nuclear Regulatory Commission, Washington, D.C. 20556, Attention: Docketing and Regulatory Guides are issued to describe and make available to the public Service Branch.

methods acceptable to the NRC staff of implementing specific parts of the Commission's regulations, to delineate techniques used by the staff in evalu- The guides are issued in the following ten broad divisions:

ating specific problems or postulated accidents, or to provide guidance to applicants. Regulatory Guides are not substitutes for regulations, and com-

1. Power Reactors

6. Products pllance with them is not required. Methods and solutions different from those

2. Research and Test Reactors

7. Transportation set out in the guides will be acceptable if they provide a basis for the findings

3. Fuels and Materials Facilities

8. Occupational Health requisite to the issuance or continuance of a permit or license by the

4. Environmental and Siting

9. Antitrust and Financial Review Commission.

5. Materials and Plant Protection

10. General Requests for single copies of issued guides lwhich may be reproduced) or for Comments and suggestions for improvements in these guides are encouraged at placement on an automatic distribution list for single copies of future guides all times, and guides will be revised, as appropriate, to accommodate comments in specific divisions should be made in writing to the U.S. Nuclear Regulatory and to reflect new information or experience. This guide was revised as a resultr Commission, Washington, D.C. 20555, Attention:

Director, Division of of substantive comments received from the public and additional staff review.

Technical Information and Document Control.

dent containment heat removal, or (3) postaccident containment atmosphere cleanup (e.g,, hydrogen re moval system);

d, Systems' or portions of systems that are re quired for (1) reactor shutdown, (2) residual heat re moval, or (3) cooling the spent fuel storage pool, e. Those portions of the steam systems of boil ing water reactors extending from the outermost con tainment isolation valve up to but not including the turbine stop valve, and connected piping of 21/2 inches or larger nominal pipe size up to and including the first valve that is either normally closed or capa ble of automatic closure during all modes of normal reactor operation, The turbine stop valve should be designed to withstand the SSE and maintain its integrity.

f. Those portions of the steam and feedwater systems of pressurized water reactors extending from and including the secondary side of steam generators up to and including the outermost containment isola tion valves, and connected piping of 21/2 inches or larger nominal pipe size up to and including the first valve (including a safety or relief valve) that is either normally closed or capable of automatic closure dur ing all modes of normal reactor operation, g. Cooling water, component cooling, and auxiliary feedwater systems ' or portions of these sys tems, including the intake structures, that are re quired for (1) emergency core cooling, (2) postacci dent containment heat removal, (3) postaccident con tainment atmosphere cleanup, (4) residual heat re moval from the reactor, or (5) cooling the spent fuel storage pool.

h. Cooling water and seal water systemsI or portions of these systems that are required for func tioning of reactor coolant system components impor tant to safety, such as reactor coolant pumps.

i. SystemsI or portions of systems that are re quired to supply fuel for emergency equipment.

j. All electric and mechanical devices and cir cuitry between the process and the input terminals of the actuator systems involved in generating signals that initiate protective action, k. SystemsI or portions of systems that are re quired for (1) monitoring of systems important to safety and (2) actuation of systems important to safety.

1. The spent fuel storage pool structure, includ ing the fuel racks.

m. The reactivity control systems, e.g., control rods, control rod drives and boron injection system.

n, The control room, including its associated equipment and all equipment needed to maintain the control room within safe habitability limits for personnel and safe environmental limits for vital equipment, o, Primary and secondary reactor containment.

p. Systems,' Dther than radioactive waste man agement systems, 2 not covered by items I.a through L.o above that contain or may contain radioactive ma terial and whose postulated failure would result in conservatively calculated potential offsite doses (us ing meteorology as recommended in Regulatory Guide 1.3, "Assumptions Used for Evaluating the Potential Radiological Consequences of a Loss of Coolant Accident for Boiling Water Reactors," and Regulatory Guide 1,4, "Assumptions Used for Evaluating the Potential Radiological Consequences of a Loss of Coolant Accident for Pressurized Water Reactors") that are more than 0.5 rem to the whole body or its equivalent to any part of the body.

q. The Class 1E electric systems, including the auxiliary systems for the onsite electric power supplies, that provide the emergency electric power needed for functioning of plant features included in items l.a through 1 ,p above.

2. Those portions of structures, systems, or com ponents whose continued function is not required but whose failure could reduce the functioning of any plant feature included in items I .a through l.q above to an unacceptable safety level or could result in in capacitating injury to occupants of the control room should be designed and constructed so that the SSE

would not cause such failure,3

3, Seismic Category I design requirements should extend to the first seismic restraint beyond the de fined boundaries, Those portions of structures, sys tems, or components that form interfaces between Seismic Category I and non-Seismic Category I fea tures should be designed to Seismic Category I

requirements.

4. The pertinent quality assurance requirements of Appendix B to 10 CFR Part 50 should be applied to all activities affecting the safety-related functions of those portions of structures, systems, and compo nents covered under Regulatory Positions 2 and 3 above,

2 Specific guidance on seismic requirements for radioactive waste management systems is under development.

3Wherever practical, structures and equipment whose failure could possibly cause such injuries should be relocated or sepa rated to the extent required to eliminate thiB possibility.

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0, IMPLEMENTATION

The purpose of this section is to provide informa tion to applicants regarding the NRC staff's plans for using this regulatory guide, This guide reflects current NRC staff practice.

Therefore, except in those cases in which the appli- cant proposes an acceptable alternative method for complying with specified portions of the Commis sion's regulations, the method described herein is being and will continue to be used in the evaluation of submittals for operating license or construction permit applications until this guide is revised as a re sult of suggestions from the public or additional staff review.

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