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Outline of Japanese Regulatory guides on seismic safety evaluation (geology and ground motions)

Outline of Japanese Regulatory guides on seismic safety evaluation (geology and ground motions). June 8, 2011 Japan Nuclear Energy Safety Organization. Regulatory Guide for Reviewing Nuclear Reactor Site Evaluation and Application Criteria.

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Outline of Japanese Regulatory guides on seismic safety evaluation (geology and ground motions)

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  1. Outline of JapaneseRegulatory guides on seismic safety evaluation(geology and ground motions) June 8, 2011 Japan Nuclear Energy Safety Organization

  2. Regulatory Guide for Reviewing Nuclear Reactor Site Evaluation and Application Criteria NSC Regulatory Guides: Criteria for judging fulfillment of Requirements for Installment License of NPPs Installment License (Attached document No.6) Status on meteorology, geotechnology, hydrology, seismology and social environment at sites planned to install NPR Facilities Regulatory Guide for Reviewing Safety Design of Light Water Nuclear Power Reactor Facilities Regulatory Guide for Reviewing Seismic Design of Nuclear Power Reactor Facilities Back-check for existing NPR Facilities Guidelines for Reviewing Seismic Safety of Nuclear Power Reactor Facilities Regulatory Guide for Reviewing Safety Assessment of Light Water Nuclear Power Reactor Facilities Regulatory Guide for the Annual Dose Target for the Public in the Vicinity of Light Water Nuclear Power Reactor Facilities

  3. Regulatory Guide for Reviewing Nuclear Reactor Site Evaluation and Application Criteria Basic Concept 1.1 Fundamental Siting Conditions (1) No event have occurred and expected to occur liable to induce large accident. Very few events deemed liable to expand disaster. (2) Located at a sufficient distance from the public (3) Appropriate measures for the public can be implemented 1.2 Basic Goal (1) Not to cause radiation damage to the neighboring public, even when assuming a “Major Accident” (2) Prevent significant radiation hazard to the neighboring publicfor “Hypothetical Accident” (3) In case of a Hypothetical Accident, effect on the collective dose shall be sufficiently small 2. Guideline for Site Review 2.1 Within “the range in a specified distance” from the nuclear reactor shall be the non- residential area 2.2 The region within the range in specified distance from the nuclear reactor and outside the non-residential area shall be the low population zone 2.3 The nuclear reactor site shall be separated by specified distance from the dense population zone. 3. Scope of Application Applied for the siting review of nuclear reactors having l0, 000 KW or larger thermal output

  4. Regulatory Guide for Reviewing Seismic Design of Nuclear Power Reactor Facilities Introduction Scope of Appication Basic Policy Classification of Importance in Seismic Design (1) Classification of Functions (2) Facilities of Classes Formulation of Design Basis Earthquake Ground Motion (DBGM) Seismic Design Philosophy (1) Primal Policies (2) Definition of Seismic Forces Load Combination and Allowable Limits (1) Buildings and Structures (2) Components and Piping systems Consideration of the accompanying events of earthquakes Commentaries Basic Policy Formulation of DBGM Ss Design Principles Load Combination and Allowable Limits

  5. Guidelines for Reviewing Seismic Safety of Nuclear Power Reactor Facilities Introduction Definitions of Terms Geology and Geologic Structure Survey around the Site Formulation of Design Basis Earthquake Ground Motion (DBGM) Evaluation of Supportive Nature of Ground for Buildings and Structures Consideration of the accompanying events of earthquakes Reliabilities on Investigations “Residual Risks” • Active Fault Survey around the Site • 1.1 Investigation on existing documents, tectonic landform survey, surficial geology and geophysical survey • 1.2 Investigation Based on Characteristics of Inland and Ocean Area • (Inland Crust /Interplate Earthquakes) • 1.3 Identification of Active Faults to be Considered for Seismic Safety Design • Geologic, geologic Structure Survey and Ground investigation around the Site

  6. Guidelines for Reviewing Seismic Safety of Nuclear Power Reactor Facilities Introduction Definitions of Terms Geology and Geologic Structure Survey around the Site Formulation of Design Basis Earthquake Ground Motion (DBGM) Evaluation of Supportive Nature of Ground for Buildings and Structures Consideration of the accompanying events of earthquakes Reliabilities on Investigations “Residual Risks” • The DBGM Ss for the Earthquake Ground Motions with the Site Specific Epicenter • 1.1 Selection of Investigation Earthquakes (Geometry of Fault, Characteristics of Source Parameter) • 1.2 Ground Motion Evaluation(Response Spectra, Fault Model) • The DBGM Ss for the Earthquake Ground Motions with no Specific Epicenter • Evaluation of DBGM • Input Ground Motion

  7. Some points to be discussed - Active Fault Survey around the Site (3.8)- Geologic, geologic Structure Survey and Ground investigation around the Site (3.9)- The DBGM Ss for the Earthquake Ground Motions with the Site Specific Epicenter (3.12)- The DBGM Ss for the Earthquake Ground Motions with no Specific Epicenter (3.5, 3.12)- Tsunami (3.13)- Extreme load of wind (3.19)

  8. Geologic, geologic Structure Survey and Ground investigation around the Site (1) Investigation around the site(To know underground structure for evaluating seismic propagation characteristics) Conduct following surveys with adequate procedure and combination on considering local characteristics and distance from the site - Investigate existing documents - Gather and analyze existing borehole data - Analyze seismic observation data - Surficial geology survey - Boring survey - 2D and 3D geophysical survey (elastic wave survey, electric survey, logging, micro tremor survey, gravitation survey etc.) - Conduct trench excavation survey (2) Investigation at the place to build facilities (To confirm supportive nature of the ground) Conduct following surveys with adequate procedure and combination considering importance of facilities on seismic design - Test pit survey - Boring survey - 2D and 3D geophysical survey (elastic wave survey, electric survey, logging etc.) - Ground material test (rock test, soil test) - In situ test (sounding, in situ rock test) - Trench excavation survey - (Groundwater survey)

  9. Information on Seismic Source, Propagation and Site Characteristics (1) Study of seismic source for each type of earthquake occurrence Earthquake observation records: necessary for grasping a phenomenon (Evaluation of empirical Green Function and site amplitude characteristics, etc.) → Set a seismometer on the subjected site and conduct an observation. Collect and analyze records on observation points near the site. Characteristics of earthquake source faults: modeling of earthquake fault rupture (Macroscopic fault model, heterogeneous fault model) → Set them empirically from the analysis of fault rupture in the past. ・Study of active faults: detailed study of faults (size, location, shape, interval of activity, etc.), ・Survey of historical earthquakes in the past, ・Damaging earthquakes based on historical materials

  10. Information on Seismic Source, Propagation and Site Characteristics (2) Study of earthquake ground motion propagation and site characteristics Study of the geology and underground structure of a site: necessary for constructing a ground structure model to evaluate site amplification (Tertiary ground structure, surface ground structure, nonlinear response characteristics) → Collect and analyze the results of structural survey surrounding the site. (Set a favorable model by continuing a survey steadily since ground structure undergoes no sudden change.)

  11. Modeling of Ground Structure: Method of Study of Underground Structure Seismic reflection method A method by where the seismic waves (mainly P-waves) which are originated from a artificial seismic source on the ground surface and reflected on the underground geological boundaries are observed with seismometers arranged on the line along roads, and the resultant records are analyzed for the cross section of underground structure. This method is similar to CT scanning. Microtremor array survey A method where microtremors are concurrently measured with seismometers arranged on plural points and underground structure including S-wave velocity is roughly estimated from wave propagation characteristics between seismometers. Gravity prospecting Gravitational acceleration varies according to location depending on underground density structure. In this method, underground structure is estimated from the property that gravitational acceleration is large where hard and heavy bedrock is shallow and small where it is deep. Seismic source Group of seismometers Instrument truck Reflected wave Sedimentary bed Basement Human activity Natural phenomenon Traffic Wind Plant Microtremors Pressure change Wave Depth of foundational ground of the Osaka Basin estimated from gravity anomaly

  12. Modeling of Ground Structure: Study of Deep Ground Structure Distance (km) A layer A layer (1600 - 1700 m/s) B layer Measured value Calculated value C layer B layer (1800 - 1900 m/s) Uemachi fault zone D layer Abut unconformity Bedrock C layer (2000 - 2800 m/s) D layer (>3000 m/s) Bedrock P-wave reflection section, velocity analysis → layer division, P-wave velocity Depth (m) Distance (km) North South Shot-point Figures mean density (p: g/cm3) Depth (km) N-S cross-section Gravitational analysis → Density structure Seismic refraction method → P-wave velocity of foundational ground

  13. Comparison between Results of Detailed Study of Ground and Analytical ModelLogging Information (1,700 m) in Higashinada Ward, Kobe City by Kansai Electric Power Co. and NUPEC (now JNES) The actual ground is complicated and is heterogeneous. As a result of representation of the detailed ground with a simplified four-layer model, the frequency response functions of the two are relatively similar to each other. Frequency response function: Ratio of earthquake ground motion spectra on the ground surface to underground Amplitude Ground surface Period Vs Vp Density 密度 Amplitude Underground Blue: detailed information Red: four-layer model + surface ground Period

  14. Formulation of Earthquake Ground Motion based on the Study of Deep and Shallow Ground Structure Earthquake ground motion on the surface Nonlinear ground response equivalent linear method Shallow ground model (database for boring data) Earthquake ground motion on engineering bedrock Hybrid method Statistical Green Function method + Tertiary difference calculus Fault rupture scenario and deep ground model Topographical and geological information and dynamic seismic source rupture simulation Active Fault research Center Geological Survey of Japan-AIST (2005)

  15. The DBGM Ss for the Earthquake Ground Motions with the Site Specific Epicenter (1) Selection of investigation earthquakes 1) Evaluate geometry of faults of supposed seismic source - Inland earthquake: Set seismic faults based on results of investigation on existing documents, tectonic landform, surficial geology and geophysics considering possibility of simultaneous activity of several faults running parallel. - Inter-plate earthquake: Consider maximum source region adequately which might cause simultaneous activity - Ocean intra-plate earthquake: Set source region considering difference of earthquake types for each regions 2) Set characteristic source parameter - Set source parameter of inland earthquakes (seismic fault, active zone) and inter-plate earthquakes (source region) by results of investigation on existing documents, tectonic landform, surficial geology and geophysics - Consider applicability of empirical formula on scaling relation between fault length, area, displacement etc. - Scale of inter-plate and inside oceanic slab earthquakes should be set by using information of landscape, geology, seismology and geodesy on historical event - Consider most recent findings for estimating scale of earthquakes with very long active faults and isolated short active faults

  16. The DBGM Ss for the Earthquake Ground Motions with the Site Specific Epicenter (2) Ground motion evaluation 1) Evaluate ground motion using response spectra - Evaluation should be conducted adequately considering application condition and range of empirical formula - Horizontal and vertical component of response spectra should be evaluated considering seismic wave propagation characteristics of underground structure around the site - Duration time and form of amplitude envelop of modeling time series should be set considering scale of earthquake and epicentral distance 2) Evaluate ground motion using seismic fault model - Evaluate ground motion by taking Empirical Green Function Method with considering adequacy of element earthquake - If taking Statistical Green Function Method and Hybrid Method (combining Theoretical Calculation and Green Function Method), propagation characteristics of seismic wave for each methods should be evaluated based on results of geology and geological structure investigation 3) Considering uncertainties The way of considering uncertainty for parameters should be specified if evaluating ground motion considering uncertainties

  17. Source Location to be Considered for the Basic Ground Motion Ss The earthquake ground motions with the site specific earthquake source locations Formulation of earthquake ground motion according to the type of occurrence of earthquakes: active faults (earthquakes in inland crusts), inter-plate earthquakes, ocean intraplate earthquakes, ocean intraplate earthquakes (intraslab earthquakes) Active faults to be considered: those which, there is no denying, have been active since late Pleistocene The earthquake ground motions with no specific earthquake source locations Nuclear facilities e. Earthquake near a site that is hard to be associated with active faults Japanese Archipelago c. Ocean intraplate earthquake a. Active faults Earthquakes in inland crusts b. Inter-plate earthquake Continental plate Ocean plate d. Ocean intraplate earthquake (intraslab earthquakes)

  18. Methods by Means of Fault Model and Response Spectrum Mi Xeq Method by Means of Fault Model Method by Means of Response Spectrum ・Detailed evaluation of earthquake ground motion taking the expansion of faults and fracture propagation characteristics (causative faults near sites, among others) Response spectrum attenuation relation Sa = f (M, Xeq , f ) Seismic spectrum Seismic force property Evaluation site = = ( ( ( F F ( ( S S ( ( f f ) ) P P ( ( f f ) ) G G ( ( f f ) ) f f f ) ) ) S S f f ) ) ･ ･ ･ ･ A A A A A A A A A A Hypocentral distance Xeq Size of earthquake （Magnitude, M） Fault plane Evaluation Consideration of uncertainty Earthquake ground motion Causative fault Waveform composite method Fault sliding Site amplification property Dispersion of attenuation relation G G G ( ( ( f f f ) ) A 100 Propagation characteristics P P ( ( f f ) ) SA(cm/s2) A A 10 Dispersion of size, location and parameter of fault Pseudo-velocity response spectrum (cm/s) １ Xeq(km) Consideration of uncertainty Evaluation of response spectrum in the horizontal and vertical motion 0.1 0.01 5 10 1 0.1 Period (s)

  19. Fault Rupture Scenario - Irikura Recipe Recipe for a rational method of setting of a seismic source rupture scenario (also referred to as the characterized seismic source model) Modeling of heterogeneous fault rupture in places where a fault is strong (asperity) and where it is comparatively fragile (background domain) Fault Model Asperity Background domain Potential fault earthquake Surface fault earthquake

  20. Progress in Modeling of Fault Rupture Scenario by Characterized Seismic Source Model (Irikura Recipe) Step 1: Fault rupture area (S=LW) Step 2: Seismic moment (M0) Step 3: Mean stress drop (DSC) Step 4: Total area of asperity (Sa) Step 5: Stress drop of asperity (DSa) Step 6: Number of pieces (N) and location of asperity Step 7: Average slip rate of asperity (Da) Step 8: Effective stress of asperity (Sa) and of background domain (Sb) Step 9: Setting of slip rate function Fault Model

  21. Comparison of Methods Based on Fault Model Grasp the features of the earthquake ground motion evaluation approach and select an approach according to the features of the points and structures. A method with the small earthquake waveform as an element Empirical Green Function method: use of small earthquake observation waveform as an element wave (Green Function) Statistical Green Function method: use of simulation wave as an element wave (Green Function) Theoretical computation of seismic waveform by means of fault rupture (difference calculus, etc.) Advantage: theoretical waveform just as the model set is available. Disadvantage: the scope of application is restricted to long wavelength (long period) due to the limitation of minute models and computational capacity. Hybrid method (Statistical Green Function method + theory) With the advantages of the two approaches, the long-period theoretical waveform and the short-period statistical simulation wave are added together in the time domain via the matching filter. Fault Model

  22. Empirical and Statistical Green Function Methods Fault Model Fault displacement of a small earthquake Observation point A large earthquake is the further growth of the fault area of a small earthquake and the sliding displacement. Rupture of a small earthquake Displacement Small fault Time Synthesize large earthquake ground motion by adding together observation records of small earthquakes according to the temporal and spatial growth of rupture. Fault displacement of a large earthquake Rupture of a large earthquake Small earthquake Displacement Point of occurrence of an earthquake Superposition Large earthquake Time Spatial superposition on a fault plane Temporal superposition of rupture process • Computation method of earthquake ground motion: Add together records on small earthquakes according to progress in fault rupture → Records of large earthquakes can be synthesized. • Requirements of records on small earthquakes → The propagation path characteristics and site amplification characteristics of records on large earthquakes are almost the same. (because the observation accuracy of records on small earthquakes (especially long period) affects the results of syntheses.)

  23. Features of Empirical and Statistical Green Function Methods Fault Model • Empirical Green Function method • Feature: seismic source, propagation path and amplification characteristics are included. Advantage: the observation wave includes many features that cannot be represented by computation. Disadvantage: it is rare that an ideal small earthquake observation waveform can be obtained before the occurrence of an anticipated large earthquake. • Statistical Green Function method • Feature: seismic source characteristics are considered as an element wave, and propagation path and amplitude characteristics are modeled. Advantage: a short-period waveform of statistical nature can be obtained. Disadvantage: too average in the long periodic area which is affected by fault rupture and ground response.

  24. Evaluation of Earthquake Ground Motion by Means of Statistical Green Function MethodExample: 1995 Hyogo-ken Nambu Earthquake Fault Model NS component NS component Acceleration Acceleration Velocity Velocity Displacement Displacement EW component EW component Acceleration Acceleration Velocity Velocity Displacement Displacement Observation waveform Simulation waveform

  25. Approach to Response Spectrum Earthquake ground motion formulated with seismic source specified for each site Evaluate spectra with average seismic source, propagation and site amplification characteristics taken into consideration by means of attenuation relations (relations between distance from seismic source and amplitude according to the size of an earthquake) (computed from observation records) Earthquake ground motion formulated with seismic source unspecified Directly evaluate spectral characteristics from observation records Response Spectrum Attenuated earthquake ground motion Complicatedly amplified earthquake ground motion Strong motion in source areas Crust Sedimentary bed Fault rupture Site amplification characteristics Propagation path characteristics Earthquake ground motion formulated with seismic source specified for each site Seismic source characteristics Observed earthquake ground motion seismic source characteristics propagation path characteristics site amplification characteristics Earthquake ground motion formulated with seismic source unspecified

  26. What Is the Response Spectrum? Characteristics where the maximum value of response of single-degree-of freedom system at natural period Ti against earthquake ground motion is computed with the natural period changed and the relations between the natural period and maximum response value are cited Amplitude A3 A1 A2 A4 Period

  27. Response Spectrum ◆　Improved Response Spectra Method of Japan Electric Association Evaluating response spectra by Magnitude,Equivalent hypocentral distance with new EQ. knowledge Response spectra (cm/s) very near near Magnitude intermediate far M8.5M8.0 Period(s) Characteristic of this Method ・Stiffness of rock is considered. ・Fault plain is evaluated by the Equivalent hypocentral distance. ・Correction Coefficients of Inland EQ. are determined . ・Correction Coefficients of Near Field Directivity Effect are determinedlarger than Period 0.3s. Magnitude Magnitude Hypocentral distance(km) High Quality EQ. Records on the rock

  28. Method of Formulating Earthquake Ground Motion Based on Response Spectrum Preparation method: obtain the time history waveform from the relations between the amplitude and phase of earthquake ground motion and adjust the amplitude in order to minimize the difference between the target and the response spectrum. Response Spectrum Acceleration Time domain (relations between time and amplitude) → conversion into frequency domain Response spectrum Ａk，BkFinite Fourier coefficient Amplitude Phase (Relations between frequency and amplitude/phase)

  29. Method of Formulating Basic Ground Motion SsExample of Evaluation by Response Spectrum Earthquake ground motion that satisfies a target response spectrum used for design. Also referred to as a simulation wave. Besides the spectrum, phase characteristics are necessary. Response Spectrum [Phase characteristics] [Example of target spectrum] Acceleration 1995 Hyogo-ken Nambu earthquake - Kobe Marine Observatory (NS) [Constructed waveform: Simulation wave] Acceleration Specifications for Highway Bridges (with Commentary) Part 5: Seismic Design Level 2, type II class I Ground Simulation waveform conforming to the spectrum of Level 2 (type II, class I Ground), whose phase characteristics are of the simulation wave of the Kobe Marine Observatory NS components.

  30. The DBGM Ss for the Earthquake Ground Motions with no Specific Epicenter (1) The DBGM for the earthquake ground motions with no specific epicenter The DBGM for the earthquake ground motions with no specific epicenter should be set based on observation records of near source event of inland earthquakes those are hard to correlate with active faults. So that adequacy of each observation data in light with recent findings should be checked because of having only small number of observation data could be used for analysis at the present moment

  31. The earthquake ground motions with no specific earthquake source locations(Formulating sample) ■Formulating the ground motion directly from earthquake records with no specific source locations which are not seemed to survey before earthquake events ・The objective events are Inland earthquakes ・Collecting earthquake ground motionrecords near source field ・Considering site condition (soil, earthquake ,etc) ・Referring Probabilistic evaluation if necessary Response spectra (cm/s) ・内陸地殻内地震を対象 ・震源近傍の観測記録を収集 ・敷地の地盤物性を加味 ・確率論的な評価等を必要に応じて参照 Period(s) Red lines: Earthquake records with no specific source locations determined before earthquake events

  32. Earthquake Ground Motions with no Specific Epicenters

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