ML20054H610
| ML20054H610 | |
| Person / Time | |
|---|---|
| Site: | Maine Yankee |
| Issue date: | 06/30/1982 |
| From: | Maine Yankee |
| To: | |
| Shared Package | |
| ML20054H604 | List: |
| References | |
| PROC-820630, NUDOCS 8206240259 | |
| Download: ML20054H610 (5) | |
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MAINE YAOSKEE ATOMIC POWER COMPANY A Program to Establish Seismic Safety Margins Using Revised Criteria and Analytical Methods MAINE YANKEE ATOMIC POWER COMPANY June 1982 i
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MAINE YANKEE ATOMIC POWER COMPANY SEISMIC SAFETY MARGINS PROGRAM TABLE OF CONTENTS Introduction 1.
Analysis of Plant Structures, Systems, and Components 2.
Seismic Hazard Determination 3.
Geological and Seismological Studies 4.
Ground Motion Monitoring Capability Upgrade 5.
Assessment 6.
Schedule -
M AINE Y ANKEE ATOMIC POWER COMPANY e
Introduction The Maine Yankee Atomic Power Station was designed and constructed between 1966 and 1972, and licensed for commercial operation in 1972.
The plant was designed and licensed on the basis of the criteria and methods generally applied to nuclear plants at the time.
These criteria and methods have continued to evolve as new data have been obtained and more sophisticated computational techniques have been developed.
This document describes the program to be undertaken by the Maine Yankee Atomic Power Company to evaluate the plant's seismic design bases in accordarce with state of the art techniques and to determine to what extent backfitting would be prudent or necessary to bring the plant's seismic capability in line with other New England plants.
The program described in what follows is comprised of some tasks to be initiated 43ecifically for this effort and some tasks inititated earlier that will be redirected.
The program involves activities in four major areas:
o Modeling and analysis of selected plant structures, systems, and components by current methods and evaluation with respect to criteria appropriate to this type of review.
o Application of several alternative means of determining site seismic haza rd.
Investigations and evaluations of events and data that occurred or O
became available after plant licensirg.
o Upgraded ground motion monitoring capability to aid in interpretation of future events.
These activities will result in identification of plant changes which might be necessary as a result of application of a more severe seismic analysis input.
Followirg completion of activities in these areas, the results and an evaluation of the results, together with additional activities suggested by the evaluation will be presented to the NRC Staff. -
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MAINE YANKEE ATOMIC POWER COMPANY 1.
Analysis of Plant Structures, Systems, and Components This task is intended to provide a demonstration that the structures, systems, and components required for safe hot shutdown remain able to perform their intended shutdown function following severe ground shaking as defined in the seismic hazard determination task. The following subtasks are involved:
o Enumeration of the structures, systems and components or portions thereof required to function to achieve hot shutdown, i.e. retain reactor coolant pressure boundary integrity, provide primary heat removal, and provide primary makeup capability.
o Development of models for analysis of hot shutdown structures, systems, and components.
Application of the results of the subtasks described above to analysis of functionability of hot shutdown systems.
o Definition of functionability related success criteria for hot shutdown conditions.
These criteria will be based upon current regulatory guidance for seismic analysis and application of normal and seismic loads (LOCA loads will be eliminated by demonstrating that an earthquake will not produce a LOCA).
o Definition of plant upgrades required to assure objective is met.
Note: Much of the above will be achieved by redirecting an ongoing program to address piping support adequacy and baseplate flexibility (IE Bulletin 79-02) which will be deferred. When resuming, the
" Robinson Fix" superimposed on the Ldesign spectra will no longer be utilized because amplified response spectra will be available.
2.
Seismic Hazard Determination This task is intended to utilize available geological and seismological data and models in developing estimates of ground shaking appropriate for use in analysis of performance of structures, systems, and components.
The following subtasks are involved:
o Development of suitable site specific ground response spectra along the general lines of 10 CFR100, Appendix A methods.
o Development of suitable ground response spectra, by probabilistic methods representing annual exceedance probability or 10-2, 10-3 and 10 5/yr.
This subtask will utilize state of the art techniques including full treatment of uncertainty and alternative input assumptions, Eastern US ground motion modeling and earthquake catalogs.
Both the zonation (formal probabilistic) and historical analysis methods will be used, and the results will be synthesized to produce a statement of the probabilistic seismic hazard with quantified uncertainty.
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MAINE YANKEC ATOMIC POWER COMPANY o Development of suitable best estimate ground response spectra by probabilistic methods representing an unbiased estimate of the seismic hazard. This is accomplished by deemphasizing demonstratably conservative hypotheses that bias the results upward, o Selection of appropriate irput for use in performance analysis, Task 1.
This task will result in a refinement of the Reg. Guide 1.60 Ground Response Spectrum anchored at 0.2g currently being used for preliminary scoping analyses.
3.
Geological and Seismological Studies This task is intended to update and augment the geologic and seismic data and models which were used in establishing the plant's licensing bases some 10-12 years ago. The following subtasks are involved:
o Review of pertinent literature and records for identification of information developed since plant licensing relating to the geological and seismological basis for earthquake hazard definition.
This subtask includes information obtained i.n a Maine Yankee sponsored study of the so-called Robinhood Fault.
- Studies of the nature and significance of the recent events in New Brunswick, Canada and Franklin, New Hampshire. An extensive scope of work in this area is being considered as a joint undertaking by several New England utilities. The specific scope Maine Yankee becomes involved in, and the work schedule, will depend on mutual agreements arrived at in this area. Further information will be provided when it becomes available (estimated: end of July 1982).
4.
Consideration of Ground Motion Monitoring Capability Upgrade This task is intended to specify what types and location of ground motion monitoring equipment might be suitable for helping determine the significance of future seismic events with respect to the Maine Yankee site.
5.
Assessment Following completion of the activities within the scope of Tasks 1 through 4, the results will be evaluated, and the results will be documented and presented to the NRC staff.
At the same time, any actions suggested by the study results, whether already underway or scheduled for the future, will be described in terms of scope, schedule, and rationale.
6.
Schedule Tasks 1 through 4 are expected to be essentially complete by July 1,1983.
Task 5 is to be essentially complete by the end of 1983.
It is anticipated that periodic states briefings will be desired. These can be arranged as mutually agreed upon.