Seismic Qualification by Testing for Electrical and Active Mechanical Equipment to be Installed in Hard-Rock High Frequency Sites

2009 ◽  
Author(s):  
Pei-Ying Chen ◽  
Ching Hang Ng
Keyword(s):  
Ground Motion ◽  
Seismic Design ◽  
High Frequency ◽  
Power Plants ◽  
Hard Rock ◽  
Response Spectra ◽  
Nuclear Industry ◽  
Mechanical Equipment ◽  
Regulatory Requirements ◽  
Structure Response

All electric and active mechanical equipment important to safety must be seismically qualified by either analysis, testing, or a combination of both. The general requirements for seismic qualification of electric and active mechanical equipment in nuclear power plants are delineated in Appendix S to Title 10, Part 50, of the Code of Federal Regulations (10 CFR Part 50), item 52.47(20) of 10 CFR 52.47, and Appendix A to 10 CFR Part 100. The staff at the US Nuclear Regulatory Commission (NRC) has recognized that the Certified Design Ground Motion may be exceeded by the site-specific ground motion. The exceedances are generally in the high-frequency range for the Central and Eastern US sites. For equipment seismic qualification consideration, the exceedances must be addressed at both the ground level and the floor level where the equipment is located. Thus, the in-structure response spectra at some locations may exceed those in-structure response spectra generated by the certified seismic design response spectra. The U.S. nuclear industry and the NRC have initiated activities to address this issue. Two scenarios that revealed themselves during the review activities of the design certification and combined license applications for new reactors will be expounded upon in the paper. In Case I, equipment seismic qualification has been approved for a certified design and equipment is to be installed at a hard-rock high frequency (HRHF) site with certified seismic design response spectra (CSDRS) exceeded by the Ground Motion Response Spectra (GMRS) of the hard-rock site. In Case II, equipment seismic qualification has not been approved for a design certification and there is an application with GMRS exceeding the not-yet-approved CSDRS. In the paper, the staff will begin the discussion with the regulatory requirements for seismic qualification of electric and mechanical equipment. The focus of the paper is to identify the staff concern and illustrate the resolution between the NRC staff and an applicant on the seismic qualification of equipment by testing, in particular for equipment to be installed in hard-rock high frequency sites, to meet the regulatory requirements.

Generation of In-Structure Response Spectra for Nuclear Power Plants Subjected to High-Frequency Ground Motion

2012 ◽  
Author(s):  
Luis M. Moreschi ◽  
Qin Pan ◽  
Shen Wang ◽  
Sanjeev R. Malushte
Keyword(s):  
Ground Motion ◽  
High Frequency ◽  
Nuclear Power ◽  
Power Plants ◽  
Response Spectra ◽  
Frequency Range ◽  
Modeling And Analysis ◽  
Analysis Techniques ◽  
Structure Response ◽  
Selection Of

The purpose of seismic qualification of Structures, Systems and Components (SSCs) in nuclear power plants is to ensure that their intended safety function will not be compromised during and after a postulated earthquake event. The seismic performance of the equipment is generally evaluated using In-Structure Response Spectra (ISRS) at equipment-support locations as an input motion. Traditionally, these ISRS are generated based on design ground spectra prescribed by either U.S. Nuclear Regulatory Commission Regulatory Guide 1.60 or other design spectral shapes, which normally consider the frequencies content up to 33Hz. However, it has been recently recognized that probabilistic hazard-based site specific ground motion response spectra (GMRS) for Central and Eastern United States (CEUS) hard rock sites contains significant energy in the high frequency range, far beyond 33Hz. Since the motion at equipment support locations is highly affected by the dynamic characteristics of the soil or rock surrounding the building foundations and those of the structure itself, the adequacy of dynamic modeling and analysis techniques for determining the ISRS is critical to seismic qualification of safety-related equipment. This paper provides examples on dynamic modeling and analysis techniques required to accurately capture the structural responses for purposes of calculating ISRS throughout the frequency range of interest, including the high frequency responses typically expected at the CEUS sites. The discussion includes the selection of finite element mesh size, and sensitivity analysis performed to demonstrate that the propagation of these high frequencies through the different levels of the structure is properly captured. Other analytical considerations, such as the selection of time step size, for conducting time-history analysis, are also presented.

The Effects of Discretization Errors on the High Frequency Content of In-Structure Response Spectra

2016 ◽  
Author(s):  
Greg Mertz ◽  
Robert Spears ◽  
Thomas Houston
Keyword(s):  
Ground Motion ◽  
High Frequency ◽  
Time History ◽  
Response Spectra ◽  
Frequency Content ◽  
Time Step ◽  
Structure Response ◽  
Time History Response ◽  
Ground Motion Records ◽  
High Frequency Content

The next generation ground motion prediction equations predict significant high frequency seismic input for rock sites in the Central Eastern United States (CEUS). This high frequency motion is transmitted to basemat supported components and may be transmitted to components supported on elevated slabs. The existing ASCE 4 analysis requirements were initially developed based on seismic motions having lower frequencies, typical of ground motions in the Western United States (WUS). The adequacy of the existing ASCE 4 analysis requirements are examined using high frequency CEUS spectral shapes and the potential error inherent in using the existing approach to computing in structure response spectra is quantified. Modifications to reduce potential error in the existing ASCE 4 criteria are proposed. In structure response spectra are typically generated for a subsystem given the time history response of a building region. The building time history response is based on analyses that use either modal time history superposition, direct integration or complex frequency response analysis of the building and supporting soil. Input to the building analyses consist of either real or synthetic discretized ground motion records. The discretized ground motion records are often based on recorded ground motion seeds and are often limited to a 0.005 second time step. Thus the time step of the seed record often limits the frequency content of the problem. Both the building analyses and in structure response spectra subsystem analysis may interpolate the discretized ground motion records to obtain stable results. This interpolation generates errors that are propagated through the analyses used to calculate in structure response spectra. These errors may result in extraneous high frequency content in the in structure response spectra. Errors are quantified by comparison of time history parameters, Fourier components and in structure response spectra.

Effects of SSI on EPR™ In-Structure Response for a Rock Site: Coherent and Incoherent High Frequency Ground Motion

2010 ◽  
Author(s):  
James J. Johnson ◽  
Oliver Schneider ◽  
Werner Schuetz ◽  
Philippe Monette ◽  
Alejandro P. Asfura
Keyword(s):  
Ground Motion ◽  
High Frequency ◽  
Ground Motions ◽  
Free Field ◽  
Response Spectra ◽  
Frequency Content ◽  
Structure Response ◽  
Standard Design ◽  
Rock Site ◽  
High Frequency Content

Recently, probabilistic seismic hazard assessments (PSHAs) performed for hard sites world-wide have yielded uniform hazard response spectra (UHRS) with significant high frequency content, i.e., frequency content greater than 10 Hz. This high frequency content is frequently due to near-field relatively low magnitude events. It is well known that these high frequency ground motions are not damaging to ductile structures, systems, and components (SSCs). One method of addressing the effect of these high frequency ground motions on structure response is to take into account the incoherency of ground motion. Over the past 25 years, free-field ground motion has been recorded providing an adequate basis for the development of ground motion coherency functions necessary to assess the effect of incoherence on nuclear power plant structures. The subject of this study was the AREVA NP EPR™ (European Power Reactor) nuclear island (NI) standard design. The effect of incoherency of ground motion on in-structure response spectra (ISRS) was assessed for the NI founded on a stiff rock site and subjected to high frequency enhanced input for hard rock sites. The ISRS at numerous locations and directions in the structures were calculated and compared. SSI is shown to be an important phenomenon for structures founded on stiff sites and subjected to high frequency ground motions.

Determination of Design Ground Motion for Potential GEN III and Plus Plants in China: A Regulatory Level Review

2017 ◽  
Author(s):  
Ziduan Shang ◽  
Yugang Sun ◽  
Hongliang Gou ◽  
Lutong Zhang ◽  
Meng Chu ◽  
...  
Keyword(s):  
Ground Motion ◽  
Seismic Design ◽  
Probabilistic Approach ◽  
Time History ◽  
Response Spectra ◽  
Regulatory Requirements ◽  
Site Specific ◽  
Motion Time ◽  
Standard Design

The determination of Design Ground Motion time history (or response spectra) is the primary and critical step to derive correct Seismic Design Inputs for a Nuclear Power Plant (NPP) design. Historically Design Ground Motion (design SSE input) for a NPP was determined by early version procedure provided in RG 1.60. It was based on a theory of deterministic approach; the resulting ground motion is given in acceleration response spectra located at free surface of a site. As a transition point, 1997 was the year where new procedure was developed and recommended in RG 1.165 based on the new theory of SSE ground motion probabilistic approach. RG 1.165 was authorized for application on all new NPPs’ design after 1997. With the advancing of PSHA approach, RG 1.165 was withdrawn and replaced with new RG 1.208 in 2008. RG 1.208 established an effective way through the similar probabilistic approach used in RG 1.165 by improving PSHA method. Both RG1.165 results and RG 1.208 results are focused on addressing site-specific design, its Ground Motion Response Spectra (GMRS) and Ground Motion Time History (converted from GMRS) are used as design inputs to specific Nuclear Island (NI) seismic design. To accomplish a Standard Design Certification, the RG 1.60 DRS is used to develop the Certified Seismic Design Response Spectra (CSDRS) by modifying control points on original RG 1.60 curves to broaden the spectra in higher frequency range. In reality, CSDRS serves as a good approach to define DRS and Design Ground Motion Time History for standard design of new NPPs in current timeframe, hence envelop the site-specific GMRS given in RG 1.208. In this paper, through the comparison of above US NRC regulatory requirements and Chinese regulatory requirements, gives recommendations on the determination of Design Ground Motion Response Spectra (or Time History), which serves as the basis for deriving seismic design inputs at required specific location (e.g. the bottom of NI foundation level) for potential “GEN III & Plus” plants in China.

Revision of Boore (2018) Ground-Motion Predictions for Central and Eastern North America: Path and Offset Adjustments and Extension to 200  m/s≤VS30≤3000  m/s

2020 ◽  
Vol 91 (2A) ◽  
pp. 977-991
Author(s):  
David M. Boore
Keyword(s):  
North America ◽  
Stochastic Model ◽  
Point Source ◽  
Ground Motion ◽  
Hard Rock ◽  
Response Spectra ◽  
Site Amplification ◽  
Eastern North America ◽  
A Value ◽  
Stress Parameters

Abstract The three sets of ground-motion predictions (GMPs) of Boore (2018; hereafter, B18) are compared with a much larger dataset than was used in deriving the predictions. The B18 GMPs work well for response spectra at periods between ∼0.15 and 4.0 s after an adjustment accounting for a path bias at distances beyond 200 km—this was the maximum distance used to derive the stress parameters on which the simulations in B18 are based. An additional offset adjustment is needed in the B18 predictions for short and long periods. The adjustment at short periods may be because the κ0 of 0.006 s stipulated by the Next Generation Attenuation-East (NGA-East) project to be used in deriving the GMPs is inconsistent with the observations on rock sites. The explanation for the offset adjustment at long periods is not clear, but it could be a combination of limitations of the point-source stochastic model for longer period motions, as well as a decreasing number of observations at longer periods available to constrain the simulations on which the predictions are based. The predictions of B18, developed for very-hard-rock sites (VS30 of 2000 and 3000  m/s), have here been extended down to VS30 values as low as 200  m/s. I find, as have others, that for a given VS30, there is generally less site amplification for central and eastern North America (CENA) than for the active crustal region dataset used for the Boore, Stewart, et al. (2014; hereafter, BSSA14) GMP equations. This might have an impact on conclusions of several previous studies of CENA GMPs that used the site amplifications in BSSA14 in comparing data and predictions. An additional finding is that the κ0 implied by recordings on a subset of stations in the Charlevoix region located on rock (data from these stations were not used in the analysis described earlier) is more consistent with a value near 0.014 s than the 0.006 s value used in B18 and the NGA-East project.

Overview of Seismic Issues in Design Certification and Combined License Application Reviews

2009 ◽  
Author(s):  
Jim Xu ◽  
Sujit Samaddar
Keyword(s):  
Seismic Design ◽  
Nuclear Power ◽  
Power Plants ◽  
Nuclear Power Plants ◽  
Response Spectra ◽  
Nuclear Regulatory Commission ◽  
Lessons Learned ◽  
Site Specific ◽  
License Application ◽  
Standard Design

The U.S. Nuclear Regulatory Commission (NRC) established a new process for licensing nuclear power plants under Title 10 of the Code of Federal Regulations (10 CFR) Part 52, “Licenses, Certifications, and Approvals for Nuclear Power Plants,” which provides requirements for early site permits (ESPs), standard design certifications (DCs), and combined license (COL) applications. In this process, an application for a COL may incorporate by reference a DC, an ESP, both, or neither. This approach allows for early resolution of safety and environmental issues. The COL review will not reconsider the safety issues resolved by the DC and ESP processes. However, a COL application that incorporates a DC by reference needs to demonstrate that pertinent site-specific parameters are confined within the safety envelopes established by the DC. This paper provides an overview of site parameters related to seismic designs and associated seismic issues encountered in DC and COL application reviews using the 10 CFR Part 52 process. Since DCs treat the seismic design and analysis of nuclear power plant (NPP) structures, systems, and components (SSC) as bounding to future potential sites, the design ground motions and associated site parameters are often conservatively specified, representing envelopes of site-specific seismic hazards and parameters. For a COL applicant to incorporate a DC by reference, it needs to demonstrate that the site-specific hazard in terms of ground motion response spectra (GMRS) is enveloped by the certified design response spectra of the DC. It also needs to demonstrate that the site-specific seismic parameters, such as foundation-bearing capacities, soil profiles, and the like, are confined within the site parameter envelopes established by the DC. For the noncertified portion of the plant SSCs, the COL applicant should perform the seismic design and analysis with respect to the site-specific GMRS and associated site parameters. This paper discusses the seismic issues encountered in the safety reviews of DC and COL applications. Practical issues dealing with comparing site-specific features to the standard designs and lessons learned are also discussed.

scholarly journals Empirical Estimation of High‐Frequency Ground Motion on Hard Rock

2016 ◽  
Vol 87 (6) ◽  
pp. 1465-1478 ◽  
Author(s):  
Olga‐Joan Ktenidou ◽  
Norman A. Abrahamson
Keyword(s):  
Ground Motion ◽  
High Frequency ◽  
Hard Rock ◽  
Empirical Estimation

Preliminary Research on the Elimination of OBE in the Seismic Design of NPP

2013 ◽  
Author(s):  
Qiang Li ◽  
Jian Zhang
Keyword(s):  
Seismic Design ◽  
Nuclear Power ◽  
Power Plants ◽  
Nuclear Power Plants ◽  
User Requirements ◽  
Regulatory Requirements ◽  
Standard Design ◽  
Explicit Analysis ◽  
Design Analyses ◽  
Requirements Documents

Two levels of seismic, i.e. OBE and SSE, are conventionally considered in the seismic design of nuclear power plants. OBE is formerly set to equal to one half of SSE. In Advanced Light Water Reacter User Requirements Documents (ALWR-URD), US EPRI recommented to decrease OBE to one third of SSE. In the standard design of third generation of nuclear power plants, such as AP1000 of Westinghouse and EPR of AREVA, OBE was eliminated and substituted by lower level earthquake. In AP1000 standard design, OBE was decreased to one third of SSE and explicit analysis on OBE in the seimic design analyses is not required. Literatures and reports related to the regulatory requirements of seismic design are reviewed to study the reasons and means to be taken to address the issue of elimination of OBE from the design analyses of NPP. It will provide guidelines on the issue of elimination of OBE from seimic analysis of NPP design in China.

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