ML19211C047
| ML19211C047 | |
| Person / Time | |
|---|---|
| Issue date: | 09/30/1978 |
| From: | Bagchi G, Shao L NRC OFFICE OF NUCLEAR REGULATORY RESEARCH (RES) |
| To: | |
| Shared Package | |
| ML19211C042 | List: |
| References | |
| REF-GTECI-A-40, REF-GTECI-SC, TASK-A-40, TASK-OR NUDOCS 8001090100 | |
| Download: ML19211C047 (19) | |
Text
.
" PROPOSED REVISION 2" Task A-40 ALTERNATIVE - 2 Rev. No. 1 May, 1978 Task A-40 SEISHIC DESIGN CRITERIA Lead RES Organizations:
Division of Reactor Safety Research (RSR)
Lead Supervisor:
L. C. Shao, Assistant Director for General Reactor Safety Research, RSR Task Manager:
G. Bagchi, Chief Structural Engineering Research Branch, RSR 2
Applicability:
All Reactor Types Projected Completion Date:
September,1979 NRR Cognizant Director:
R. C. DeYoung, Director Division of Site Safety and Environmental Analysis NRR Cognizant Engineers:
D. Allison, D0R H. Rood, DPM 80010000 M l M 1737 187
I I
'f Task A-40 Rev. No. 1 May, 1978 l
1.
PROBLEM DESCRIPTION The seismic design process required by current NRC criteria includes the following sequence of events.
Define the magnitude er intensity of the earthquake which will A.
produce the nazimum vibratory ground motion at the site (the safe shutdown earthquake or SSE).
Determine the free-field ground motion at the site that would B.
result if the SSE occurred.
Determine the motion of site structures by modifying the free-C.
field motion to account for the interaction of the site struc-tures with the underlying foundation soil.
Detemine the motion ~ of the plant equipment supported by the D.
site structures.
Compare the seismic loads, in appropriate combination with E.
other loads, on structures, systems, and components important to safety, with the allowable loads.
While this seismic design sequence includes many conservative factors, certain aspects of the sequence may not be conservative for all At present it is believed that the overall sequence is plant sites.
The objective of this program is to investigate adequately conservative.
selected areas of the seismic design sequence to determine their conser-vatism for all types of sites, to investigate alternate approaches to parts of the design sequence, to quantify the overall conservatism of the design sequence, and to modify the NRC criteria in the Standard In this manner this Review Plan if changes are found to be justified.
program will provide additional assurance that the health and safety of the public is protected, and if possible, reduce costly design conser-vatisms by improving (1) current seismic design requirements, (2) NRR's capability to evaluate the adequacy of seismic design of operating reactors and plants under construction, and (3) NRR's capability to quantitatively assess the overall adequacy of seismic design for nuclear plants in general.
2.
PLAN FOR PROBLEM RESOLUTION The overall program for short-term resolution of the seismic design criteria issue is divided into the tasks and subtasks listed below.
The Lead Division of NRR is given in parentheses for.each task.
1737 188
Task A-40 Rev. No.1 May, 1978 Task 1.0 Quantification of Seismic Conservatisms (DOR) 1.1 Display of Methodology 1.2 Design Ground Motion 1.3 Seismic Analysis and Design 1.4 Structural and Mechanical Resistance 1.5 Overall Quantification Task 2.0 Elasto-Plastic Seismic Analysis (DOR) 2.1 Model Development 2.2 Elasto-Plastic Analysis 2.3 Conventional Analysis 2.4 Conclusions and Recommendations Task 3.0 Site Specific Response Spectra (00R) 2 Task 4.0 Seismic Aftershocks (DOR) 4.1 Assess Data on Aftershocks Quantify Probability of Aftershock Before Plant is safely 4.2 Shut Down 4.3 Recomend Number of Earthquake Cycles 4.4 Recommend Allowable Level of Inelastic Behavior Nonlinear Structural Dynamic Analysis Procedures for Category I Task 5.0 Structures (DSS) 5.1 Survey of Methods of Nonlinear Analysis
'737 189 i
5.2 Selection of Reference Method 5.3 Benchmark Analyses
- This task has been deleted due to sparsity of data o aftershocks.
2 and equipment are limited to low ductility levels.
I Task A-40 Rev. No. 2 May, 1978 Task 6.0 Soil-Structure Interaction (DSS) 6.1 Evaluation of Analytical Limitations 6.2 Evaluation of Regulatory Guide 1.60 6.3 Effect of Horizontally Propagating Surface Wave 6.4 Evaluation of Linear Iterative Procedure 6.5 Evaluation of Plane Strain Model 6.6 Determination of Control Motion Location 6.7 Analyze Rotational Inputs 6.8 Conclusions and Recommendations
- 7.0 Earthquake Sour'ce Modeling (DSE)
- 8.0 Development of Strong Motion Near-Field Data (DSE)
- 9.0 Development of Seismic Energy Attenuation Functionals (DSE)
Task 10.0 - Review and Implementation (DPM) 10.1 Review and Evaluate Results of Other Tasks 10.2 Modify Standard Review Plan A description of each of the above tasks and subtasks is given below:
Task 1.0 Quantification of Seismic Conservatisms The plant seismic design process required by NRC criteria (following identification of the SSE for a site) includes a number of conservative factors and may include some factors which are not conservative. The objective of this task is to identify and quantify each of these factors, and then estimate the overall conservatism of the seismic design process.
This task will consist of five subtasks, as described below.
Subtask 1.1: Display of Methodology
~
Prepare a matrix of the different analytical models showing the different analyses to be performed and the item for which the results will be used.
- These tasks were deleted due to their long-term nature and impact 2
on the schedule.
1737 190
Task A-40 Rev. No. 1 May, 1978 Subtask 1.2:
Design Ground Motion This subtask will evaluate the conservatism of the use of Regulatory Guide 1.60 response spectra, the use of 1/2 the SSE g value for the OBE, and the simultaneous application of seismic input to all points on the foundation of a structure.
Subtask 1.3: Seismic Analysis and Design This subtask will evaluate the conservatism inherent in the analysis and design methods recommended by the Standard Review Plan, including inelastic vs elastic analysis, Regulatory Guide 1.61 damping values, soil-structure interaction, three-component analysis,' absolute sum combination of loads, peak widening of floor response spectra, the use of maximum response spectra for multiple-supported systems, multiple application of damping values, system redundancy, and qualification of electrical and mechanical equipment.
Subtask 1.4:
Structural and Mechanical Resistance This subtask will evaluate the conservatism due to the use of minimum material properties, the use of static rather than dynamic resistance of structures, the use of 28-day concrete strength, the use of " allowable" ductility rather than ducti-lity to failure, energy absorption by non-load carrying structures, and the stringency of nuclear QA programs.
1737 19I
Task A-40 Rev. No.1 May, 1978 Subtask 1.5:
Overall Quantification Having determined the conservatism of each aspect of seismic design, quantify the overall conservatism of several typical structures, systems, and components by determining the overall margin to failure, and performing a probabilistic assessment of the overall risk.
Task 2.0 51asto-Plastic Seismic Analysis Elasto-Plastic behavior of structures tends to absorb a significant portion of the seismic energy, therby reducing the imposed seismic loads from those predicted using an elastic analysis. This task will investigate the extent to which simplified elasto-plastic design methods are applicable for use in the design of Category I and adjacent non-Category I structures. The purpose of this task is twofold:
(1) to compare the degree of conservatism of a typical steel frame for a static, and several vintages of dynamic, analyses to a rigorous elasto plastic analysis technique; and (2) to recom-send a simplified elasto plastic analysis technique with corresponding inelastic analysis parameters; i.e., damping values, response spectra, etc., for possible use in the analysis of non-Category I structures.
This task is divided into five substasks:
Subtask 2.1:
Model Development Develop the dynamic model of a typical two-bay, three-story steel frame, a typical vertical piping system and a typical horizontal piping system.
A typical pump and valve will be assumed to be attached to the piping system to represent equip-ment and its corresponding supports.
Subtask 2.2:
Elasto-Plastic Analysis Perform rigorous elasto plastic time history analyses of the models set up in subtask 2.1 by subjecting them to typical recorded seismic accelerograms representing (a) near field effects and (b) far field effects in order to detemine the threshold "g" values for the structure, system and component.
9 1737 192
=
Task A-40 Rev. No.1 May, 1978 Subtask 2.3:
Conventional Analysis Using the same models perform analyses corresponding to the different vintages of design criteria; i.e.:
static application of "g" value - determine the "g" values (a) for the structures, component, and system assuming elastic
- behavior, dynamic design with Housner type of spectra, corresponding (b) damping values and floor response spectra - determine the "g" values for the structures, component, and system assuming elastic behavior, and dynamic design with current criteria in accordance with (c) sections 3.7 and 3.8 of the Standard Review Plan - deter-eine the "g" values for the structures, component, and system assuming elastic behavior.
Obtain relative conservatism of each item in Subtask 2.3 by comparing the results with those of Subtask 2.2.
Subtask 2.4:
Conclusions and Recommendations Make recommendations on a simplified elasto plastic analysis technique such as the one proposed by N. M. Newmsrk and the corresponding inelastic analysis parameters such as damping values, response spectra, etc.
Task 3.0 Site-Specific Response Spectra The current spectral shape as defined by Regulatory Guide 1.60 is based upon a s?.atistical data base which is strongly biased toward shallow California earthquakes.
It has been concluded that the guidelines provided in Regulatory Guide 1.60 may be overly conserva-tive for many plant sites. This task is intended to assist in defining site-specific spectral shapes that are realistic and not overly conservative. The objective of this task is to develop procedures for the determination of site-specific response spectra to evaluate the seismic input parameters such as maximum ground acceleration, spectral velocity, and spectral displacement for a variety of nuclear power plant sites. This task will be carried out as follows:
1737 193
Task A-40 Rev. No.1 May, 1978 Perform a literature search and make recommendations to the staff regarding the procedures for the determination of site-(a)
For example, (1) the site-specific specific response spectra.
spectra may be based on a uniform probability of exceedence through the frequency range of interest, (2) site-specific spectra may be based on the envelope of the response spectra of actual strong motion time histories applicable to the selected plant site (similar site condition, same intensity earthquake, etc.)
Identify computer codes and automated routines utilized in this (b) project and document any modifications to same.
Recommend methodologies to be used to determine the site-(c) specific response spectra.
Task 4.0 Seismic Aftershocks 2
This task has been deleted Nonlinear Structural Dynamic Analysis Procedures for Task 5.0 Category I Structures _
This task is designed to provide the staff with.a p structures beyond their elastic response range.
The Standard Review Plan and regulatory guides currently provide no The criteria or acceptable methods for nonlinear seismic analysis.
present licensing need, however, requires the development of ac This need is ance criteria and methods of analysis in this area.
principally in existing plants (e.g., Diablo Canyon) where deter tions regarding design adequacy of Category I values.
This task differs from Task 2.0 above, in that Task 2.0 emphasizes the development of simplified, response spectrum methods of ine analysis, whereas Task 5.0 is oriented primarily towards the time-history method of analysis.
This task will consist of three subtasks, as described below:
1737 194 y
Task A-40 Rev. No.1 May, 1978 Subtask 5.1:
Survey of Methods of Nonlinear Analysis Conduct a literature search for both rigorous and simplified methods of dynamic analysis for structures with nonlinear or inelastic behavior for the purpose of identifying specific approaches for implementing the below-defined tasks.
Subtask 5.2:
Selection of Reference Method Based on the results of the literature search and the review group's expertise in the area, the review group will identify and recommend the most pertinent yet simplified and practical dynamic analysis procedure for Category I structures, systems, and components with reliance on nonlinear or inelastic behavior.
The procedure should have the capability of handling nonlinear response of multi-degree-of-freedom systems and structures.
Description of the recommended procedure should include all baric assumptions for the analysis, theoretical background, analytical models, mathematical formulation, methods of solu-tion, verification of reliability and correctness of the method and interpretation of results.
If computer programs are involved, description of the programs, including flow diagram, complete program listing, program verification date, program applica-bility and limitations and sources of sub-routines, should be included.
Subtask 5.3:
Benchmark Analyses Develop a set of benchmark problems and perform comparative studies of the benchmark problems using the rigorous and simpli-fied nonlinear analysis methods and the conventional methods of elastic dynamic analysis to establish relative merits of the two approaches (i.e., nonlinear and linear approaches) and recommend cases where the nonlinear dynamic analysis method shou 11 be used.
Recommend pertinent design criteria and analysis guidelines that should be followed in conducting nonlinear dynamic analyses of Category I structures, systems, and com-ponents using the recommended method of analysis.
1737 195 m
Task A-40 Rev. No.1 May, 1978 Task 6.0 Soil-Structure Interaction The subject of soil-structure interaction analysis has long been a controversial subject because of the various techniques preferred by Recently, it has become a primary issue on different applicants.
several projects being licensed and has been designated an ACRS Generic Item (IIE-1).
In order to provide a confirmatory basis for, or otherwise to revise the current Standard Review Plan positions, an indepth study which will evaluate from an analytical point of view the various techniques, including deconvolution analyses, is urgently needed.
The objective of this investigation is to determine limits and conditions of applicability as well as estimates of conservatism in the definition of seismic input and soil-structure interaction procedures currently used in the seismic analysis of nuclear power Specific attention will be given to the conservatism embodied plants.
in the application of computer programs such as SHAKE and LUSH employed for deconvolution and soil-structure interaction analysis.
Particular c'.t.ention will be given to requirements concerning varia-tion of soil properties, enveloping the response spectra at the foundation level, and fixing a minimum value of the response spectra at the foundation level.
This task will consist of eight subtasks, as described below:
Subtask 6.1:
Evaluation of Analytical Limitations Analyze the assumptions used in modeling soil-structure interac-tion as specified in the computer codes SHAKE and LUSH and determine appropriate liaits and conditions of applicability.
In doing this, specifically consider geological features such as oblique strata and undulating topography and the appro-priateness of postulating a horizontally layered soil with uniform properties at a given depth.
Subtask 6.2:
Evaluation of Regulatory Guide 1.60 Analyze the suitability of using Regulatory Guide 1.60 (Defini-tion of Seismic Input) with SHAKE.
Specifically consider that D
9 1737 196
Task A-40 Rev. No.1 May, 1978 SHAKE requires a site dependent input but that R.G. 1.60 pro-vides a relatively broad band frequency input which might result in unrealistic motions predicted at depth.
Subtask 6.3:
Effect of Horizontally Propagating Surface Wave Determine by analysis the effect of a horizontally propagat'ng surface wave on.;tructures, systems, and components and estimate the conservatism of the SHAKE assumption that earthquake motions will arrive at a site via a vertically propagating body wave.
Subtask 6.4:
Evaluation of Linear Iterative Procedure Analyze the significance and consequences on the analytical results of the SHAKE use of an equivalent linear iterative procedure in light of recent studies that have indicated that a more exact nonlinear procedure may give different results, especially for large nonlinearities.
Subtask 6.5:
Evaluation of Plan Strain Model Analyze the significance and the consequences on the analytical results of SHAKE's use of a plane strain model to perform one deconvolution of an earthquake component at a time when, in actuality, three translational components of the earthquake motion will propagate simultaneously.
Subtask 6.6:
Determination of Control Motion Location Determine the appropriate location (e.g., finished grade, foundation level, first competent rock layer) for specifying the seismic control motion.
Subtask 6.7; Ar 41yze Rotational Inputs Perform analyses to determine the safety significance of rota-tional seismic inputs (e.g., rocking and torsional inputs).
Subtask 6.8:
Conclusions and Recommendations Recommend appropriate methods of p'erforming seismic decon-(a) volution analyses, including estimates of conservatism and 1737 197
.. g
Task A-40 Rev. No.1 May, 1978 limits of applicability.
Recommend analytical procedures for sitas having a shallow soil layer over the first competent rock layer.
(b) Recommend appropriate methods of performing soil-structute interaction analysis, including:
(1) when to use the elastic half space method, and (2) when to use the finite element method.
8 I
e
~
'][37 l98
Task A-40 Rev. No.1 May, 1978 Task 7.0 Earthquake Source Modeling
- 2 Task 8.0 Development of Strong Motion Near-Field Data
- Task 9.0 Development of Seismic Energy Attenuation Functionals
- Task 10.0 Review and Implementation The objective of this task is to provide a technical review o changes in NRC criteria, regulatory guides, regulations, etc., based on these results.
Subtask 10.1 Review and Evaluate Results of Other Tasks This subtask involves the establishment of a seismic review group, with representatives from each of the four NRR divisions and from Research and Standards.
The function of the group would be to periodically review the results of each of the When interim or final results are tasks in this program.
available for a task, the review group would evaluate the results and recommendation to be taken, if warranted, to modify the Standard Review Plan, the Regulatory Guides, or the i
Regulations.
All the tasks in this program have the potential of resulting in modifications to the standard review plan, depending on the In addition, Tasks 1.0 through 4.0 will resu'ts obtained.
rese t in the development of criteria for use in the Systematic Evalution Program for re-review of operating reactors.
Subtask 10.2: Modify Standard Review Plan Under this subtask, recommended changes to the Standard Review Plan in seismic areas will be implemented by NRR.
BASIS FOR CONTINUED PLANT OPERATION AFD LICEN 3.
OF TASK As discussed in Section 1, the objective of this t for all types of sites, to investigate alternate approaches to parts of the design sequence, to quantify the overall conservatism of the design sequences, and to modify the licensing criteria ifThe changes are found to be justified.
applicable to all types of nuclear power plants.
These tasks were deleted.
1737 199
Task A-40 Rev. No.1 May, 1978 We anticipate that the results of this task will provide confirma-tion that current requirements provide an overall conservative approach to seismic design. The general result that is anticipated from this task is the development of better insight into seismic design considerations that will permit establishment of a set of integrated requirements providing for more realistic and effective designs without a loss of overall aargin.
Three general types of results are expected from this task. The first of these is the ability to select seismic design ground motion inputs for each site that are more appropriate for the site and thus will result in a more consistent level of seismic design for all plants.
Second, it is expected that these investigations will demonstrate that the current methods of analysis are conservative in relation to other methods that could-be justified and to provide a quantitative idea of how conservative they are.
Finally, it is expected that this effort will demonstrate that the overall safety margins attained using current methods are considerable.
In the interim, it is believed that continuation of the current licensing requirements will assure an acceptable level of safety in plant seismic design.
If the results of this task action plan are not as anticipated and thecurrentcriteriaprovenottobeadequateT9conservativeinsome way for some sites, then corrective action might be indicated for one or more plants that now meet the current criteria.
Based on our experience in upgrading the seismic design criteria for some plants, the following considerations apply to this unexpected eventuality:
The corrective action probably would consist of performing (1) detailed plant specific analyses to determine what modifica-tions, if any, are needed.
(2) We expect that such modifications, if required, would be practical and could be implemented in a timely and safe manner.
Since we do not expect any need for upgrading from this task (3) action plan, it is likely that any such need that does arise would not be major. Thus we expect that modifications, if required, would not be major.
Based on the. discussion above we conclude that while this task is being performed, continued operation and plant licensing can proceed with reasonable assurance of protection to the health and safety of the public.
1737 200
Task A-40 Rev. No. 1 May, 1978 4.
NRR TECHNICAL ORGANIZATIONS INVOLVED This section delineates the organizational responsibilities and manpower requirements for each task within NRR before the respon-sibility of the management of this task was transferred to RES in 2
September, 1979.
NRR's participation in FY1979 is limited to review and comment. The cognizant NRR Division and cognizant NRR engineers are also listed in this section.
A.
Engineering Branch, Division of Operating Reactors, has lead responsibility for Tasks 1.0, 2.0, 3.0, and 4.0 and secondary responsibility for Tasks 5.0, 6.0 and 10.0.
Manpower Estimate:
1.0 Man years FY 1978.
8.
Structural Engineering Branch, Division of Systems Safety, has lead responsibility for Tasks 5.0 and 6.0 and secondary responsi-bility for Tasks 1.0, 2.0, 3.0 and 10.0.
2 Manpower Estimate: 0.5 Man years FY 1978; C.
Geosciences Branch, Division of Site Safety and Environmental Analysis, has lead responsibility for Tasks 7.0, 8.0, and 9.0 and secondary responsibility for Tasks 1.0, 3.0, 4.0, 6.0 and 10.0.
Manpower Estimate:
0.7 Man years FY 1978; D.
Light Water Reactors, Branches 1 and 2, Division of Project Management, have overall responsibility, as Task Managers, for coordination and management of all tasks, and have lead responsi-bility for Task 10.0.
Manpower Estimate:
0.8 Man years FY 1978; Cognizant NRR Divisions and Cognizant NRR Engineers:
A.
Division of Operating Reactors T. Cheng H. Levin D. Allison B.
Division of Systems Safety S. Chan H. Tolk C.
Division Site Safety and Environmental Evaluation L. Reiter D.
Division of Project Management 1737 201 H. Rood
Task A-40 Rev. No. 1 May, 1978 5.
TECHNICAL ASSISTANCE REQUIREMENTS Amount Lead Task No. Division contractor FY1978 FY1979 FY1980 Task Objective 1.0 DOR LLL 304.000 0
Quantify seismic conservatisms 2.0 D0R LLL 80,000 0
Develop and evaluate elasto-plastic analysis techniques 3.0 D0R LLL 70,000 130,000 Develop methods to determine
~ ite-specific response s
spectra 2
4.(f D0R LLL 5.0 DSS URS/ John 62,000 0
Develop nonlinear Blume seismic analysis methods 6.0 DSS D'Appolonia 142,000 29,000 Evaluate soil-structure interaction analysis 7.0 DSE
- Systems, 0
65,000 101,000 Develop earthquake Science and source modeling methods Software 8.0 & 9.0 DSE LLL 57,000 58,000 Develop methods to determine strong-motion near-field spectra 10.0 RES LLL 60,000 Review results of TOTALS 658,000 341,000 159,000
- project was deleted.
1737 202
'- y
Task A-40 Rev. No.1 May., 1978 6.
INTERACTION WITH OUTSIDE ORGANIZATIONS A.
ACRS The tasks in this program are of interest to the ACRS; speci-fically, the ACRS Seismic Subcommittee.
Further, Task 6.0 of this program directly addresses the issue raised by ACRS Generic Item IIE-1, Soil-Structure Interaction.
Accordingly, this program will be co-ordinated with the Committee as the tasks in the program progress.
B.
U.S. Geological Survey Intermittant interaction with the USGS is expected for the purpose of obtaining seismic data.
7.
ASSISTANCE REQUIREMENTS FROM OTHER NRC OFFICES Office of Standards Development, Division of Site Health and A.
Safeguards Standards Close coordination with OSD is required since this task is closely related to a number of seismic tasks that are planned or are being conducted by OSD. This coordination will be achieved by holding meetings with 050 personnel to exchange information, and by inclusion of one or more 050 members on the seismic review group overseeing A-40 (see Task 10.0).
Office of Nuclear Regulatory Research, Division of Reactor B.
Safety Research Close coordination with RSR is required since this task is closely related to the Seismic Research Program being under-One of the three major objectives of the Seismic taken by RSR.
Research Program is the Quantification of Conservatisms in Present Seismic Methodology.
It is expected that the work currently underway in Task 1.0 of A-40 will provide input to This will be facilitated by the this aspect of the RES effort.
fact that the same contractor (LLL) is undertaking both efforts.
~
1737 203 m
Task A-40 Rev. No.1 May, 1978 Co-ordination of A-40 with RSR seismic efforts will be achieved hy holding meetings with RSR personnel to exchange information, hy inclusion of one or more RSR members on the seismic review group overseeing A-40 (see Task 10.0), and by requesting that RSR include the A-40 Task Manager in the Seismic Research Review Group which reviews RSR seismic efforts.
8.
POTENTIAL PROBLEMS 9
hhhhh{
b "PROPOSEDREVIS10tl2"
" ALTER %TIVE2 "
TAP A f40 SCHEDULE OF RUOR HILESTONES R
R R
R R
5
.O O
k b
d k
k CONTRACTOR FINAL LLL RESOLUTION FINAL REPORT TO CONTRACTOR RECOMEN-0F NRC SRP REVIEW REPORT DATION COMMENTS POSITIONS COMITTEE ON SRP TO RRRC POSITIONS 1737 205