ML25079A272
| ML25079A272 | |
| Person / Time | |
|---|---|
| Issue date: | 03/11/2025 |
| From: | Office of Nuclear Regulatory Research |
| To: | |
| References | |
| Download: ML25079A272 (1) | |
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Supporting International Coordination on Nuclear Technologies and Licensing Activities NRC/NEA Workshop on Seismic Input Motion Development for Analysis and Design of Nuclear Installations Structural, Geotechnical, and Seismic Engineering Branch Division of Engineering, Office of Nuclear Regulatory Research
Workshop on Seismic Input Motion Development (SIMD) for Analysis and Design of Nuclear Installations Location: NRC Headquarters Date: May 2026 (dates to be determined)
==
Introduction:==
The international SIMD workshop will bring together the seismological and the structural engineering communities for a focused discussion of SIMD-related topics and their impact on seismic safety of both advanced reactor designs and large light-water reactors.
The workshop will address recent research findings indicating that power spectral density (PSD) functions are necessary for response spectra (RS) to adequately represent the intended input motions. The workshop will cover three main topics: (1) historical and recent developments and applications of RS and PSD in seismic engineering, (2) near-term considerations for SIMD in seismic analysis and design, and (3) long-term research and development needs for robust measures to address the full spectrum of seismic engineering tasksincluding seismic hazard analysis, seismic load specification, and seismic analysis, design, and risk assessment. The workshop will promote international uniformity and efficiency, particularly in supporting advanced reactor designs for which licenses may be pursued in multiple countries. Many of these designs involve innovative systems such as seismic isolators, graphite fuel pebbles, and water pools and other fluid systems that behave in the nonlinear regime during strong earthquakes.
OECD/NEA Committee on the Safety of Nuclear Installations (CSNI) Activity Proposal Sheet (CAPS)
Working Group on Integrity and Ageing of Components and Structures (WGIAGE)
CAPS WGIAGE(2024)-1
Leading and Supporting Organizations for the SIMD Workshop
A Sample of RS and PSD Development in Modern Seismic Engineering 1925 2025 1950 1975 2000 Newmark (1959)
Newmark-Beta time integration method Fourier Transform (FS) (1807)
PSD (the early to mid-20th century)
Tajimi (1960)
Filtered Gaussian (Kanai-Tajimi PSD)
Moayyad, Mohraz (1982)
Strong motion parts are stationary.
PSDs for soft, medium, and hard ground types.
Support Random Vibration Theory.
Gasparini, Vanmarcke (1976)
SIMQKE Scanlan (1977)
Seismic loading:
FS RS Suyehiro (1926)
Seismic vibration analyzer of 13 pendula (Japan)
Veletsos, Newmark, Jenschke, Clough, Penzien, Fisher, etc.
(1960-1965)
Tripartite spectra pseudo vs true spectra Biot (1932)
Theory for RS Newmark, Hall Blume, Kapur (1969, 1973)
NPP design RS Housner (1941)
RS FS for engineering applications SRP (1975)
Rev. 0 SRP (1981)
Rev. 1 SRP (1989)
Rev. 2 SRP (2007)
Rev. 3 SRP (2014)
Rev. 4 NRC/NEA (2026*)
SIMD WS Recent NRC Research (since 2013)
RS-matching criteria alone are inadequate.
PSD checks are necessary to prevent the underprediction of in-structure RS and other frequency-dependent structural responses.
RS, by itself, cannot adequately serve as the basis for seismic load specification without careful consideration of its relationship to the PSD.
SRP: Standard Review Plan, WS: workshop *2026 is the centennial of the RS concept proposed by Prof. Suyehiro in 1926.
Housner: Starting in the 1950s, the federal regulatory agency required that the design spectrum be used in nuclear power plant [NPP] design. So the nuclear power industry really forced engineers all over the country to be aware of the spectrum and seismic design.
Amplified region ISRS in the amplified region is not guaranteed by the input RS/ISRS ZPA. The same input RS/ISRS ZPA can correspond to vastly different ISRS curves (beyond the expected variation due to phase angle differences),
depending on how the seismic design time histories are generated.
Frequency Spectral Acceleration Technical
Background:
RS-Matching Criteria Alone Are Inadequate ISRS: In-Structure Response Spectra ZPA: Zero Period Acceleration on RS or ISRS RS ISRS The input spectral value at the oscillator frequency is the ZPA on the ISRS of the oscillator response (mathematically, RS ISRS ZPA).
Examples of Very Similar Input RS Leading to Vastly Differing Oscillator ISRS
PSD Checks Can Identify Power Deficiencies Which Cause the Underestimation of ISRS and Other Seismic Demands PSD Check for T1 - 15 Main Frequencies PSD Check for T2 - Broadband PSD Check for T3 - Broadband with 5-15 Hz Cut PSD Check for T4 - Broadband with 1-20 Hz Cut Input RS
Summary
- RS-matching criteria alone are inadequate.
- PSD checks are essential to avoid underestimating ISRS and other frequency-dependent structural responses.
- Underestimated seismic demands can result in unsafe designs.
- RS alone cannot adequately serve as the basis for seismic load specification without carefully considering its relationship to the PSD.
- This limitation also applies to response spectrum analysis, which relies on PSD either implicitly or explicitlyfor correlation coefficient calculations.
NRC/NEA Workshop on Seismic Input Motion Development for Analysis and Design of Nuclear Installations NRC Headquarters, May 2026 Contacts Jinsuo.Nie@nrc.gov Laurel.Bauer@nrc.gov Keiko.Chitose@nea.org