Appendix S to Part 50 - Earthquake Engineering Criteria for Nuclear Power Plants
10:1.0.1.1.30.0.117.88.39 : Appendix S
Appendix S to Part 50 - Earthquake Engineering Criteria for Nuclear
Power Plants General Information
This appendix applies to applicants for a construction permit or
operating license under part 50, or a design certification,
combined license, design approval, or manufacturing license under
part 52 of this chapter, on or 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. Paragraphs IV.a.1.i, IV.a.1.ii, IV.4.b, and
IV.4.c of this appendix apply to applicants for an early site
permit under part 52.
I. Introduction
(a) Each applicant for a construction permit, operating license,
design certification, combined license, design approval, or
manufacturing license is required by §§ 50.34(a)(12), 50.34(b)(10),
or 10 CFR 52.47, 52.79, 52.137, or 52.157, and General Design
Criterion 2 of appendix A to this part, to design nuclear power
plant structures, systems, and components important to safety to
withstand the effects of natural phenomena, such as earthquakes,
without loss of capability to perform their safety functions. Also,
as specified in § 50.54(ff), nuclear power plants that have
implemented the earthquake engineering criteria described herein
must shut down if the criteria in paragraph IV(a)(3) of this
appendix are exceeded.
(b) These criteria implement General Design Criterion 2 insofar
as it requires structures, systems, and components important to
safety to withstand the effects of earthquakes.
II. Scope
The evaluations described in this appendix are within the scope
of investigations permitted by § 50.10(c)(1).
III. Definitions
As used in these criteria:
Combined license means a combined construction permit and
operating license with conditions for a nuclear power facility
issued under subpart C of part 52 of this chapter.
Design Approval means an NRC staff approval, issued under
subpart E of part 52 of this chapter, of a final standard design
for a nuclear power reactor of the type described in 10 CFR
50.22.
Design Certification means a Commission approval, issued
under subpart B of part 52 of this chapter, of a standard design
for a nuclear power facility.
Manufacturing license means a license, issued under
subpart F of part 52 of this chapter, authorizing the manufacture
of nuclear power reactors but not their installation into
facilities located at the sites on which the facilities are to be
operated.
Operating basis earthquake ground motion (OBE) is the
vibratory ground motion for which those features of the nuclear
power plant necessary for continued operation without undue risk to
the health and safety of the public will remain functional. The
operating basis earthquake ground motion is only associated with
plant shutdown and inspection unless specifically selected by the
applicant as a design input.
Response spectrum is a plot of the maximum responses
(acceleration, velocity, or displacement) of idealized
single-degree-of-freedom oscillators as a function of the natural
frequencies of the oscillators for a given damping value. The
response spectrum is calculated for a specified vibratory motion
input at the oscillators' supports.
Safe-shutdown earthquake ground motion (SSE) is the
vibratory ground motion for which certain structures, systems, and
components must be designed to remain functional.
Structures, systems, and components required to withstand the
effects of the safe-shutdown earthquake ground motion or surface
deformation are those necessary to assure:
(1) The integrity of the reactor coolant pressure boundary;
(2) The capability to shut down the reactor and maintain it in a
safe-shutdown condition; or
(3) The capability to prevent or mitigate the consequences of
accidents that could result in potential offsite exposures
comparable to the guideline exposures of § 50.34(a)(1).
Surface deformation is distortion of geologic strata at
or near the ground surface by the processes of folding or faulting
as a result of various earth forces. Tectonic surface deformation
is associated with earthquake processes.
IV. Application to Engineering Design
The following are pursuant to the seismic and geologic design
basis requirements of § 100.23 of this chapter:
(a) Vibratory Ground Motion. (1) Safe Shutdown
Earthquake Ground Motion. (i) The Safe Shutdown Earthquake
Ground Motion must be characterized by free-field ground motion
response spectra at the free ground surface. In view of the limited
data available on vibratory ground motions of strong earthquakes,
it usually will be appropriate that the design response spectra be
smoothed spectra. The horizontal component of the Safe Shutdown
Earthquake Ground Motion in the free-field at the foundation level
of the structures must be an appropriate response spectrum with a
peak ground acceleration of at least 0.1g.
(ii) The nuclear power plant must be designed so that, if the
Safe Shutdown Earthquake Ground Motion occurs, certain structures,
systems, and components will remain functional and within
applicable stress, strain, and deformation limits. In addition to
seismic loads, applicable concurrent normal operating, functional,
and accident-induced loads must be taken into account in the design
of these safety-related structures, systems, and components. The
design of the nuclear power plant must also take into account the
possible effects of the Safe Shutdown Earthquake Ground Motion on
the facility foundations by ground disruption, such as fissuring,
lateral spreads, differential settlement, liquefaction, and
landsliding, as required in § 100.23 of this chapter.
(iii) The required safety functions of structures, systems, and
components must be assured during and after the vibratory ground
motion associated with the Safe Shutdown Earthquake Ground Motion
through design, testing, or qualification methods.
(iv) The evaluation must take into account soil-structure
interaction effects and the expected duration of vibratory motion.
It is permissible to design for strain limits in excess of yield
strain in some of these safety-related structures, systems, and
components during the Safe Shutdown Earthquake Ground Motion and
under the postulated concurrent loads, provided the necessary
safety functions are maintained.
(2) Operating Basis Earthquake Ground Motion. (i) The
Operating Basis Earthquake Ground Motion must be characterized by
response spectra. The value of the Operating Basis Earthquake
Ground Motion must be set to one of the following choices:
(A) One-third or less of the Safe Shutdown Earthquake Ground
Motion design response spectra. The requirements associated with
this Operating Basis Earthquake Ground Motion in Paragraph
(a)(2)(i)(B)(I) can be satisfied without the applicant
performing explicit response or design analyses, or
(B) A value greater than one-third of the Safe Shutdown
Earthquake Ground Motion design response spectra. Analysis and
design must be performed to demonstrate that the requirements
associated with this Operating Basis Earthquake Ground Motion in
Paragraph (a)(2)(i)(B)(I) are satisfied. The design must
take into account soil-structure interaction effects and the
duration of vibratory ground motion.
(I) When subjected to the effects of the Operating Basis
Earthquake Ground Motion in combination with normal operating
loads, all structures, systems, and components of the nuclear power
plant necessary for continued operation without undue risk to the
health and safety of the public must remain functional and within
applicable stress, strain, and deformation limits.
(3) Required Plant Shutdown. If vibratory ground motion
exceeding that of the Operating Basis Earthquake Ground Motion or
if significant plant damage occurs, the licensee must shut down the
nuclear power plant. If systems, structures, or components
necessary for the safe shutdown of the nuclear power plant are not
available after the occurrence of the Operating Basis Earthquake
Ground Motion, the licensee must consult with the Commission and
must propose a plan for the timely, safe shutdown of the nuclear
power plant. Prior to resuming operations, the licensee must
demonstrate to the Commission that no functional damage has
occurred to those features necessary for continued operation
without undue risk to the health and safety of the public and the
licensing basis is maintained.
(4) Required Seismic Instrumentation. Suitable
instrumentation must be provided so that the seismic response of
nuclear power plant features important to safety can be evaluated
promptly after an earthquake.
(b) Surface Deformation. The potential for surface
deformation must be taken into account in the design of the nuclear
power plant by providing reasonable assurance that in the event of
deformation, certain structures, systems, and components will
remain functional. In addition to surface deformation induced
loads, the design of safety features must take into account seismic
loads and applicable concurrent functional and accident-induced
loads. The design provisions for surface deformation must be based
on its postulated occurrence in any direction and azimuth and under
any part of the nuclear power plant, unless evidence indicates this
assumption is not appropriate, and must take into account the
estimated rate at which the surface deformation may occur.
(c) Seismically Induced Floods and Water Waves and Other
Design Conditions. Seismically induced floods and water waves
from either locally or distantly generated seismic activity and
other design conditions determined pursuant to § 100.23 of this
chapter must be taken into account in the design of the nuclear
power plant so as to prevent undue risk to the health and safety of
the public.
[61 FR 65173, Dec. 11, 1996, as amended at 72 FR 49508, Aug. 28,
2007]