Regulatory Guide 1.12

Revision1, Instrumentation for Earthquakes

ML003739947
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Issue date:	04/30/1974
From:	Office of Nuclear Regulatory Research
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RG-1.12, Rev 1
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Revision 1 April 1974 U.S. ATOMIC ENERGY COMMISSION

REGULATORY GUIDE

DIRECTORATE OF REGULATORY STANDARDS

REGULATORY GUIDE 1.12 INSTRUMENTATION FOR EARTHQUAKES*

A. INTRODUCTION

appropriate locations to provide data on the seismic input to containment, data on the frequency, amplitude, Paragraph (c) of § 50.36, "Technical and phase relationship of the seismic response of the Specifications," of 10 CFR Part 50, "licensing of containment structure, and data on the seismic input to Production and Utilization Facilities," provides that the other Seismic Category I structures, systems, and technical specifications will include surveillance components. It is desirable that these strong-motion requirements to assure that the necessary quality of accelerographs be located so as to facilitate the systems and components is maintained, that facility engineering analysis of the recorded traces following an operation will be within safety limits, and that the earthquake.

limiting conditions of operation will be met. Appendix A, "Seismic and Geologic Siting Criteria for Nuclear The acceleration value corresponding to zero period Power Plants," to 10 CFR Part 100, "Reactor Site in the containment foundation design response spectra Criteria," requires, in Paragraph VI (aX3), a suitable may be referred to as the "acceleration level" of the program for implementing this requirement with regard input design earthquake motion to the containment to seismic instrumentation needed to determine structure. This acceleration level is an important promptly the seismic response of nuclear power plant features important to safety to permit comparison of parameter because the magnitudes of the design response such response with that used as the design basis. Such a spectra themselves are affected to a large extent by this level, and the plant shutdown requirement as specified in comparison is needed to decide whether the plant can Appendix A to 10 CFR Part 100 is also related to this continue to be operated safely. This guide describes seismic instrumentation acceptable to the AEC level. It is therefore necessary to install a triaxial seismic switch at an appropriate location in the basement Regulatory staff as satisfying the above-stated capable of providing an immediate signal to remotely requirements of Appendix A to 10 CFR Part 100. This indicate if the specified zero-period acceleration has guide does not, however, address the need for been exceeded. This can provide the basis for immediate instrumentation that would automatically scram a administrative procedures if needed.

nuclear power plant or specify the methods to be used in the analysis of recorded data. The Advisory Committee on Reactor Safeguards has been consulted concerning Appendix A to 10 CFR Part 100 requires that all this guide and has concurred in the regulatory position. the structures, systems, or components of a nuclear power plant necessary for continued operation without E

L. DISCUSSION

undue risk to the health and safety of the public be designed to remain functional when subject to the When an earthquake occurs, it may not be known Operating Basis Earthquake (OBE). Since the immediately how severe the effects of the earthquake zero-period acceleration of the containment foundation are on a given nuclear power plant. It is advisable to have design response spectra representing the OBE may not triaxial time-history accelerographs 1 installed at fully describe the seismic event, it is important to have a triaxial response-spectrum recorder installed at an

• This guide is a revision of Safety Guide 12. appropriate location in the basement of the plant capable of providing immediate signals for remote

' See ANSI Standard N18.5, "Earthquake Instrumentation indicating in the control room if any significant portion Criteria for Nuclear Power Plants", for definitions. This standard is available from the American Nuclear Society, 244 East Ogden of the foundation design response spectra has been Avenue, Hinsdale, Illinois 60521. exceeded. This can provide additional basis for USAEC REGULATORY GUIDES Copies of published guides may be obtained by request Indicating the divisions desired to the US. Atomic Energy Commission, Washington, D.C. 20648, Regulatory Guides are Issued to describe and make available to the public Attention: Director of Regulatory Standerds. Comments and suggestions for methods aceptable to the AEC Regulatory staff of implementing specific parts of Improwments in thee guides re encouraged and should be sent to the Secretary the Commission's regulations, to delineate techniques used by the staff in of the Commission, U.S. Atomic Energy Commission, Washington, DC. 20645, evaluating specific problems or postulated accidents, or to provide guidance to Attention- Chief, Public Proceedings Staff.

applicants. Regulatory Guides are not substitutes for regulations and compliance with them is not required. Methods and solutions different from thuoset out in The guides ere issued In the following ten broad divisions:

the guides will be acceptable if they provide a basis for the findings requisite to the issuance or continuance of a permit or license by the Commission. 1. Power Reactors

6. Products

2. Research and Test Reactors

7. Transportation

3. Fuels and Materials Facilities S. occupational Health Published guide wll be revised periodically, as appropriate, to accommodate 4. Environmental and Siting 9. Antitrust Review comments end to reflect new Information or experience. S. Materials and Plant Protection 1

0. General

immediate administrative procedures or decisions Nuclear Power Plants," is acceptable to the Regulatory immediately following an earthquake. staff for satisfying the seismic instrumentation requirements indicated in Paragraph VI (a) (3) of The effects of the seismic motion at a given floor Appendix A to 10 CFR Part 100 for assuring the safety level in a structure can be represented by calculated of nuclear power plants, subject to the following:

floor response spectra. In many of the nuclear power plants, calculated floor response spectra are also used to 1. The instrumentation called for in Section 4.1 of the design Seismic Category I systems and components Standard should be applied to nuclear power plants with supported on these levels. It is therefore important to a Safe Shutdown Earthquake maximum foundation install triaxial response-spectrum recorders at the acceleration of less than 0.3 g as supplemented by the selected support (floor) locations to determine if the following:

calculated floor response spectra have been exceeded.

This information will be needed to determine (1) the a. Instead of the locations specified in Section conservatism in the modeling and design assumptions 4.1.2 of the Standard, one triaxial peak accelerograph made for the structure and design input motion to the should be provided at one location of each of the supported systems and components and (2) the following:

advisability of continuing the operation of the plant (1) A selected location on the reactor without a safety analysis following an earthquake. equipment.

(2) A selected location on the reactor piping.

The magnitude of the response of the systems and (3) The most pertinent location on one of the components supported on the containment structure is following outside of the containment structure:

required in order to verify if the actual response of these (a) Seismic Category I equipment.

parts has exceeded the design basis. This can be (b) Seismic Category I piping.

monitored by installing triaxial peak accelerographs 2 over selected locations on these parts. In addition, peak b. One triaxial response-spectrum recorder 3 response of these parts will be necessary to determine capable of measuring both horizontal motions and the the conservatism in the modeling and design assumptions vertical motion and capable of providing signals for made for these systems and components. immediate control room indication should be provided at the containment foundation.

The severity of response of a given Seismic Category I structure will depend to a large degree on the c. One triaxial response-spectrum recorder capable maximum acceleration of the Safe Shutdown of measuring both horizontal motions and the vertical Earthquake at the foundation of the containment motion should be provided at one location of each of structure. It is therefore reasonable to relate the amount the following:

of instrumentation desirable to the magnitude of the (1) A selected location on the reactor maximum expected foundation acceleration. For this equipment or piping supports.

purpose, Safe Shutdown Earthquakes are divided into (2) The most pertinent location on one of the two categories: (1) earthquakes with maximum following outside of the containment structure:

foundation accelerations of less than 0.3 g, and (a) A seismic Category I equipment

(2) earthquakes with maximum foundation support or appropriate floor location.

accelerations of 0.3 g or greater. The earthquakes in the (b) A Seismic Category I piping support or first category may be termed as ranging from moderate appropriate floor location.

to strong, and the earthquakes in the second category (3) At the foundation of an independent may be called severe. This guide prescribes appropriate Seismic Category I structure where the response is instrumentation for monitoring these categories. different from that of the reactor containment structure.

Working Group ANS-2.2 of Subcommittee ANS-2, 2. Section 4.2 of the Standard should not be used.

Site Evaluation, of the American Nuclear Society Standards Committee, prepared ANSI N18.5, 3. The instrumentation specified in Section 4.3 of the

"Earthquake Instrumentation Criteria for Nuclear Power Standard should be applied to nuclear power plants with Plants," which contains most of the criteria with respect a Safe Shutdown Earthquake maximum foundation to location and number of instruments, instrument acceleration of 0.3 g or greater as supplemented by characteristics, and instrumentation station installations Regulatory Positions 1 and 2 above, and the following:

specified in this guide.

a. Instead of the locations specified in Section

C. REGULATORY POSITION

4.3.2 of the Standard, one triaxial time-history accelerograph should be provided at the most pertinent Earthquake instrumentation specified in ANSI

N 18.5, "Earthquake Instrumentation Criteria for 3 An instrument having the capability when actuated of I ANSI N18.5 for definitions. permanently recording peak responses as a function of frequency.

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location on one of the independent Seismic Category I be provided at a selected location on reactor equipment structures where the response is different from that of supports or piping supports.

the reactor containment structure.

4. The response-spectrum recorders should have the b. Instead of the locations specified in Section following specifications:

4.3.3 of the Standard, one triaxial peak accelerograph should be provided at the most pertinent location on a. Dynamic Range-50:1 zero to peak (such as Seismic Category I equipment or piping in an 0.02 g to 1.0 g).

independent Seismic Category I structure where the response is different from that of the reactor b. Frequency Range-minimum coverage from 1 containment structure. Hz to 30.0 Hz.

c. In addition to the locations specified in c. Damping-not less than nominal 2% nor more Regulatory Positions l.b., l.c.(l), and l.c.(3) above, one than nominal 5% of critical damping, controlled to triaxial response-spectrum recorder should be provided +/-0.15 of nominal. The actual amount of damping is to at one location on both items specified in Regulatory be consistent with the OBE-based design damping for Positions l.c.(2Xa) and l.c.(2Xb) above. the supported structure or equipment.

d. Instead of the locations specified in Section 5. Instead of the dynamic range specified in Section

4.3.4 of the Standard, one triaxial seismic switch should 5.3.5 of the Standard, a range of 100:1 should be used.

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