ML20133F784
| ML20133F784 | |
| Person / Time | |
|---|---|
| Site: | Millstone  |
| Issue date: | 09/30/1985 |
| From: | STONE & WEBSTER ENGINEERING CORP. |
| To: | |
| Shared Package | |
| ML20133F781 | List: |
| References | |
| NUDOCS 8510110227 | |
| Download: ML20133F784 (27) | |
Text
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I SEISMIC INTERACTION REVIEW PROGRAM MILLSTONE III NUCLEAR POWER STATION September 1985 Prepared for:
Northeast Utilities Service Company P.O. Box 260 Hartford, CT 06141-0270 Prepared by:
Stone & Webster Engineering Corporation P.O. Box 2425 Boston, MA 02107 851011 % $ h 423 PM A
PM A
l SWEC JOB NO.12179
TABLE OF CONTENTS Page 1.
I N T R O D U CTION.............................................. I 2.
REGUL ATORY REQUIREMENTS................................. 2 3.
D ESI G N CRITE RIA........................................... 4 4.
SEIS MIC R EVIEW PROG R A M..................................... $
5.
HISTORICAL CONSIDE R ATIONS................................. 9 6.
P I P I N G................................................
11 7.
PROG R A M ORG ANIZ ATION.................................... 12 8.
SEISMIC REVIEW CRITERIA.................................... 14 9.
REVIEW METHODOLOGY...................................... 19 10.
DOC UM E NT ATION..........................................
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- 1. INTRODUCTION The design of-Millstone Unit 3 precludes seismic-induced interactions which would unacceptably affect safety system operability or structural integrity during or following an earthquake.
This is accomplished by designing plant safety features to Seismic Category I standards and by assuring that nonsafety features are installed such that the earthquake will not result in damage which will adversely affect any nuclear safety function. Such damage is avoided by providing adequate physical separation in the plant layout.
This separation adequacy is established by considering the relative seismic-
-induced displacements between adjacent structures and components. Damage from gross catastrophic failure of nonsafety structures, systems, and components is not considered credible because such failures are generally precluded by adherance to existing industry construction practices. This position is strongly supported by data collected at facilities which have experienced earthquakes well in excess of the design requirements for Millstone 3.
This positior, is supplemented by a visual inspection program (walkdown). This program verifles that there are no unusual design features which would produce a credible singular localized failure mechanism which, in turn, would result in structural collapse or any detachment from a secure anchorage. Further, this walkdown verifies the adequacy of the installed separation.
The review considers the constraints on the maximum seismic displacement condition as influenced by inherent component stiffness, equipment terminations, and by rigid - s
structural elements, such as penetrations.
The maximum displacement condition is predicted and compared to the available clearance.
At locations where clearance is inadequate, seismic-induced interactions are judged to occur and a review is made to determine the possibility and degree of safety function impairment. Both the dynamic and environmental consequences of damage resulting from any interaction are reviewed to assure that the safety function of adjacent plant safety features are not reduced to an unacceptable level.
- 2. REGULATORY REQUIREMENTS The design requirement of 10CFR50 Appendix A - Criterion 2 states that " Structures, sys tems, and components important to safety, shall be designed to withstand...
earthquakes... without loss of capability to perform their safety functions."
These structures, systems, and components are those plant features that are necessary to ensure the integrity of the reactor coolant boundary, the capability to shut down the reactor and maintain it in a safe shutdown condition, or the capability to prevent or mitigate the consequences of accidents that could result in potential offsite exposures comparable to the guideline exposures of 10CFR100.
These plant features are listed in USNRC Regulatory Guide 1.29. They are structures, systems, and components, including their foundations and supports for:
1.
The reactor coolant pressure boundary.
2.
The reactor core and internals.
3.
The emergency core cooling systems.
4.
The post-accident containment heat removal system.
e 5.
The post-accident containment atmospheric cleanup system.
- 6. - The reactor shutdown system.
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The residual heat removal system.
8.
The spent fuel pool cooling system.
9.
The portion of the main steam and feedwater system extending between the steam generators and the outermost containment isolation valves.
- 10. Cooling water, component cooling water, and auxiliary feedwater systems required for 3,4,5,7 and 8 above.
- 11. Cooling water and seal water systems required for functioning of the reactor coolant system components such as the reactor coolant pumps.
- 12. Emergency equipment fuel systems.
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- 13. Systems that initiate protective action.
- 14. Systems that monitor safety systems.
- 15. Systems that actuate safety systems.
- 16. Spent fuel pool and storage racks.
- 17. Reactivity control system - Rod drive and boron injection.
- 18. The control room.
- 19. Reactor containment.
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- 20. Class IE electric system including emergency onsite power systems.
. The post-seismic performance requirements for the above plant features is assured by implementing the Seismic Cttegory I design requirements and the pertinent Quality l'
Assurance requirements of 10CFR50 Appendix B.
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Plant features which are not listed above need not be assured to functionally survive an earthquake and consequently need not be designed and constructed to these standards.
Regulatory Guide 1.29 makes provisions for a design basis which provides a reasonable assurance of continued safe plant operation following an earthquake by specifying a conservative design environment for plant features identified as having intrinsic safety functions. No credit may be taken for the functional availability of nonsafety systems under such circumstances. This distinction does not, however, mandate the presumption that nonsafety structures, systems, and components fall. The possibility of such failures is addressed by Regulatory Guide 1.29 as follows:
w portions of structures, systems, or components whose continued tunction is not required but whose failure could reduce the functioning of any plant feature (previously listed above) to an unacceptable safety level or result in incapacitating injury to occupants of the control room should be designed and constructed so that the earthquake would not cause such failure."
- 3. DESIGN CRITERIA The Millstone 3 design addresses the Regulatory seismic design requirement by segregating nonsafety from safety plant features or by providing adequate separation between them using barriers or constraints which prevent interactions severe enough to reduce safety function to an unacceptable level. This is verified by the following Seismic Review Program..-
- 4. SEISMIC REVIEW PROGRAM The adequacy of seismic separation between plant features is determined by a visual inspection of the installation combined with any engineering evaluations necessary to investigate unusual spacial relationships and nonstandard design features. Particular attention is paid to design features which contain elements which historically have been proven to be susceptable either to damage as targets or to gross distortion or anchorage failure induced by carthquakes.
Earthquake survival records demonstrate that structures, systems, and components similar to nuclear plant features survive carthquake effects and maintain structural integrity and operability. Gross structural failures are infrequent and where evidenced have easily identifiable reasons. For example, such data indicate that seismic-induced failures are restricted to cases involving failure of either fragile design elements such as ceramic insulators, or by design features not found in the current design such as inadequately anchored equipment whose sliding or overturning motion damages fluid, structural and electrical connections.
Tanks, electrical cabinets, and skid-mounted assemblies are the components that historically are found to be poorly anchored. Except for cases resulting from large dif ferential anchor motion, there are no recorded inertially-Induced piping failures.
Where separation between plant features is not found adequate to preclude interactions whlch could result in unacceptable reduction in plant safety level, additional engineered barriers or constraints are provided if additional clearance cannot be obtained.
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Also, nonsafety features are upgraded to a Selsmic Category 11 Design standard whenever unusual or nonstandard design features are identified which present a credible threat of gross catastrophic failure. Such failures are therefore precluded given that nonsafety features are designed and constructed to accepted industry practice, and as such, have l
l been shown historically to demonstrate inherent seismic resistance, given proper 1
anchorage. Consequently, the specific treatment of non-standard configuration coupled l
with the historical data base adequately addresses the safety concerns of Category II Interactions with Category I equipment.
It should be noted that Selsmic Category 11 is a Stone and Webster design designation l
which is used to ensure that unusual design features, which could result in gross catastrophic failure, are avolded.
It is principally used to provide a design basis for equipment anchorage and structural adequacy for nonsafety equipment which will be located in or near areas containing safety-related equipment. All equipment designed in i-accordance with this designation is exp!!citly evaluated to assure structural Integrity and is attached to supports and embedments also designed to Category 11 standards. This approach provides maximum flexibility of equipment placement during layout development. It does not ensure nor require operability of the equipment. The Selsmic Category 11 design approach has been used more extensively than the current data base would warrant. This is princ! pally because evidence of seismic survival is a more recent industry development.
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In each case, the design standard is commensurate with the threat to safety and l
susceptability to seismic damage. The following examples Illustrate this point.
Concrete block walls represent a potentially significant seismic threat from gross f ailure unless constructed to withstand selsmic elfccts. Doors which provide a 1
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safety-related function, such as leaktightness, are reviewed to assure that they will not swing or slide into safety equipment, but gross catastrophic failure is not considered credible, nor have such failures been found.
Elevators in the containment structure and auxiliary building, for example, are not explicitly seismically designed, because the ef fects of gross failure will be contained within the shaitway. On the other hand the suspended ceiling in the control room, along with its supporting structure, is seismically designed.
In order to preserve maximum flexibility in layout development during early stages of plant design, non-safety structures, systems and components to be located in safety-related areas have been designated Selsmic Category 11 with following exceptions:
1.
Supports for Individual nonsafety electrical cable and conduit installed in safety-related areas during final stages of plant construction.
Special markings are provided to assist in the identification of these components during the seismic walkdown review. Electrical raceways utilize Seismic Category 11 supports, however.
2.
Nonsafety piping systems located in safety areas will not experience gross catastrophic failure during an carthquake and consequently are not designated Seismic Category 11.
This is substantiated by experience data coupled with Interaction evaluations, as described in this report.
3.
Nonsafety unit heaters located in safety areas are not seismically designed, since there is no historical precedent for seismic-induced structural failure of these components.
The supports for these heaters are designed Seismic Category 11.
4.
Nonsafety instruments which are relatively small and lightweight present insignificant seismic threat and historically have proven to be structurally resistant to carthquakes.
In summary, this program is based on the stipulation that adequate seismic separation, or alternatively the severity of seismic damage can be adequately assessed by trained reviewers conducting plant walkdowns. This review identifies areas of concern for which additional engineering evaluations are required. Influential considerations include:
The safety function of the structure, system, or component.
Permissible damage to safety features, such that safety function is not impared to an unacceptable level.
Displacement limitations imposed by support structures, constraints, and barriers.
The seismic criteria to which the structure, system, and components are explicitly designed.
Adherence to industry quality standards and practice.
The presence of unusual or nontypical design features.
Visualization of credible singular failure mechanisms.
Yerification that the equipment fits within the range of characteristics represented in the selsmic survival data base.
Prediction of maximum seismic displacements including those resulting from credible failure modes.
An assessment of the expected damage to safety features.
The adequacy of redundant load paths provided by adjacent design elements in accommodating seismic-induced distortion of nonsafety components yet precluding gross catastrophic failure. -
- 5. HISTORICAL CONSIDERATIONS REF1: EQE Incorporated. The Application of Experience Data to Seismic Interaction at the Millstone Ill Nuclear Power Plant. EQE, San Francisco, CA, January 1985.
The above report summarizes the type and severity of seismic-induced failures for eight California earthquakes, for strong ground motions, ranging to 0.8 g, and for a variety of facilities containing components which have similar applications in nuclear power stations.
l This datf provides insight into what design features and installations are candidates for l
failure and the reasons for past failures. A persistent pattern of failures can be seen l
resulting from inadequate anchorage of equipment which, in turn, damages piping and electrical connections when overturning or sliding motion occurs. Damage resulting from excessive differential movement of equipment is also evidenced. Also, failures of unusually fragile design elements such as ceramic insulators and suspended ceiling panels and light fixtures are recorded.
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l The remaining failures are isolated cases resulting from adverse juxtapositions of design l
elements or from seismically inadequate design features which are readily identified.
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The record shows that seismic-induced interactions between design elements is a frequent occurrence but significant damage or functional impairment rarely occurs. The retrieval of such data during walkdowns and the nature of observed failures strongly indicates that a visual inspection program can ef fectively identify inadequate component separation.
The walkdown program at Millstone 3 identifies potential adverse seismic interactions by considering the following:
Review the appropriateness of equipment anchorage which has not been Identify components which could dislodge and fall on safety components.
Identify components which can sway, slide, or shake in such a way as to contact and damage safety features.
Predict the direction and magnitude of seismic motions for comparison with existing clearances between safety and nonsafety components.
Examine the design and installation of nonsafety components for unusual or nontypical features which could result in gross failure.
Visually assess failure scenarios for cascading damage.
Assure that past evidence of seismic survival and failure is uniformly applied.
- 6. PIPING It is useful to describe the seismic review process using a specific case. For example, the review of seismic-induced piping interactions considers piping system failures as either a potential threat to adjacent safety systems or as a threatened safety system itself.
Seismic-induced interactions with pipe. and associated in-line components and supports will occur wherever clearances to adjacent components are inadequate to preclude physical contact with the piping system. These interactions are unacceptable only if the. _ _ _.
operability or structural integrity of a safety system is impaired to an unacceptable level.
Functional or structural impairment of nonsafety piping is acceptable if the damage does not cause of unacceptable damage to any other safety-related component.
In order to assess clearance adequacy, the relative seismic motion of the intact piping systems are first compared to the available clearance between them. Usually, clearances between design features are large enough to accommodate s!! ding, swaying, or bouncing motion caused by the earthquake. These clearances are the result of good design and construction practices and very easily recognized by a trained reviewer. The reviewer also inspects the systems for support placement, locations of gapped constraints such as penetrations and rupture restraints, and the effects of stiffness and mass of in-line components such as valves and flexible connections to equipment.
Possible interactions are reviewed for potential functional impairment and cascading events which could effect safety equipment. Valve operability, support damage, flow area reduction, pressure boundary failure, and effects on small branch lines are concerns for targeted piping systems.
Historical data indicates that the piping systems remain intact during the carthquake, and although plastic distortion of components may be evidenced, gross catastrophic failure of anchorage and support st.ucture is not observed, even for piping that is not explicitly seismically designed. This is a direct consequence of the industry standards used for -
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I design and construction and inherently robust designs which are produced by the cumulative influences of conservative design codes and analytical methods.
These 1
standards preclude the kinds of infrequent pipe support damage on record.
Reference I summarizes piping damage resulting from strong ground motion at a number of California carthquake sites.
The piping failures resulted from inadequate or nonexistent anchorage of equipment to which the piping was attached. This condition is l
precluded by the seismic design of embedments in nuclear stations. Some failures were caused by insufficient piping flexibility which was unable to accommodate dif ferential movement between well anchored equipment to which the piping was attached. The in spn is review programgfor this condition.
- 7. PROGRAM ORGANIZATION l
In order to maintain a uniformity of review and to take maximum advantage of the i
seismic survival data, the review program is structured to train reviewers to visualize seismic motion and to identify installations which provide adequate separation. This is done through discussions with reviewers who have walked down facilities which have experienced carthquakes. This establishes a baseline for recognizing designs which have not failed or experienced significant damage and familiarizes reviewers with the photographic records of previous seismic, damage.
Further, an independent review of the review criteria, methodology, documentation adequacy, and conclusions is made utilizing separate independent walkdowns made on a l
1 selected basis by a consultant team, in order to provide a check for thoroughness and l
possible reviewer bias.
The program is administered by Stone and Webster and an Independent review of the program and reviewer training is provided by EQE Incorporated l
t (EQE).
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EQE provides consultant engineering and design services to industry concerning current selsmic design requirements and future standards necessary to evaluate seismic design l
adequacy and provide cost effective seismic designs. Currently, EQE provides consulting services to the Seismic Qualification Utilities Group (SQUG) which in cooperation with the NRC ls studying historical carthquake survival data in order to demonstrate selsmic ruggedness of a number of classes of safe shutdown equipment for operating nuclear power plants.
EQE also provides services to Utilities, Government Agencies, and l
Research Organizations.
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- 8. SEISMIC REVIEW CRITERIA The selsmic review program verifles design adequacy by performing a walkdown to identify potential Interactions and by demonstrating that any potential impairment of safety function, is inconsequential. If the visual inspection identilles unusual or non-l typical design features which could result in gross catastrophic failure of a nonsafety component, then a damage assessment is necessary to determine the acceptability of any l
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Interaction with safety-related components. Such Interactions may occur directly or
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through a cascading interaction with an Interposed nonsafety component. A damage l
assessment is almilarly required if the relative seismic motion between components t
exceeds the available clearance between them. Deformations caused by such interactions f
can be categorized as to the type and degree of safety i
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i function impairment. Impairment of safety function occurs either through loss of active functions (operability) or through loss of passive functions such as electrical continuity, pressure boundary, flow area, or structural integrity.
I whe Su The review program is contingent upon establishinggunctional impairment results from seismic-induced Interactions and thereby determines the adequacy of separation from safety related components. I?unctional impairment is reviewed from the perspective of the susceptibility of the safety function to scismic-induced interactions in the form of loads, distortions, accelerations, and displacements.
Active components for which operability is of additional concern are conservatively assumed (but not expected) to lose function af ter being subjected to scismic Interactions. This is because impact loads and accelerations are difficult to predict accurately and are characteristically different than equipment seismic qualification tests.
Interactions with inotor control centers, switchgear, motor operated valves, and air operated valves are typical of this concern.
Seismic-induced Interactions with active components are prohibited.
l'assive safety functions for which structural integrity is the inaln concern can more readily be judged on the basis of overall Integrity and stability of the structure, system, or component if the limits to localized and overall deformations can be determined by the walkdown program.
In order to assess the inaximurn deformation of the safety target, it is necessary to l
determine the overlap between the extreme positions of the interacting components.
t When compared to the available clearance between the two components, a prediction of the Interaction severity and worst case local and overall distortion of the safety target is possible. The maximum excursion of a cornponent is predicted by examining the
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orientation and stiffness and function of its supports, its inherent structural rigidity, its proximity to adjacent robust structures capable of locally limiting its displacement, and the influence of mass distribution on its seismic response.
l For example, suppose that during the walkdown a nonsafety 8-inch pipe is seen to be located approximately 1 inch away from an electrical cable. This cable is seen leaving a l
l cable tray and terminating at a motor operated valve, mounted on a 4-inch pipe which is l
l the discharge of a safety-related pump. The 8-inch pipe enters the cubicle through an unsealed penetration in the ceiling and runs vertically down, exiting the cubicle through another open penetration in the room. The cubicle is 15 feet high. The 8-inch pipe is I
i unsupported in the cubicle. There is a 2-inch clearance between the 8-inch pipe and the l
i The reviewer is alerted by the unusually small clearance, and lack of pipe supports on the nonsafety line.. Therefore, contact between the cable and the 8-inch pipe is postulated.
The severity of the interaction can be predicted by considering that the maximum displacement of the 8-inch pipe is constrained to 2 inches at the penetrations. Additional bending of the 8-Inch pipe between these points of constralnt will occur but is expected to l
t be minimal given that there are no in-line components which would introduce significant l
r Inertia loads. Overall bending is conservatively assumed to be 1 inch and the extreme position of the 8-Inch pipe in the direction of the safety related electrical cable is 3 I
i inches from its present position.
A scismic-induced interaction will occur since the avallable clearance is only 1 inch. Ilowever, even though contact will occur, the mounting of the electrical cable and the separation between components may still be adequate to l
preclude impairment of safety function to an unacceptable degree.
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Here, the sensitivity of the target to the interaction is the key to the significance of the Interaction. Electrical cable will readily accept applied displacements without loss of electrical continuity given adequately secured terminations and a reasonable amount of j.
slack between support points. If the Installation is accessable to the reviewer, the reviewer may also manually induce movement in the cable to prove adequate slack is avalloble.
l To further illustrate this point, assume in the above example that the electrical cable target is replaced by a 2-inch safety-related pipe. Inherently this pipe has resistance to local deformation, which occurs at the point of contact, and to overall bending. The pattern of deformation is different for different support schemes and is affected by tne l
proximity of other plant features.
Tho severity of this Interaction will be estimated based on the relative pipe sizesand the local compilance of the Category I piping and supports.
If the safety systems cannot accomdate the required movement, while maintaining acceptable performance, then the interaction will be prevented, by design.
- 9. IIEVIEW METilODOLOGY i
All buildings and areas identitled as nuclear safety-related are reviewed.
To assure thoroughness and to assist in locating potential Interactions, the buildings which contain safety-related structures, systems, and components are subdivided into arbitrarily numbered cubicles or areas.
A visual inspection of each area is made by a trained reviewer to identify potential seismic interactions resulting from inadequate clearance between components and to.
examine the installation for unusual design features which could experience gross catastrophic failure due to an earthquake. The interactions are identified and damage evaluated using the review criteria described in the previous section of this report.
In general, nonsafety and safety systems are segregated into separate buildings, or l
l separate areas within buildings.
In situations were systems could not be segregated, attempts were made during plant layout to use separation to avoid interactions.This results in some simplification in the walkdowns given that some areas do not contain a mixture of dif ferent safety classes.
The results of the evaluation fall into one of the following categories:
1.
Adequate clearance - No physical contact occurs between nonsafety and safety-related components.
2.
Inadequate clearance - Physical contact occurs between a nonsafety and safety component.
The next step is to establish the severity of the Interaction and determine if there is adequate separation.
3.
Adequate separation - The Interaction does not cause damage severe enough to reduce safety function to an unacceptable level.
4.
Inadequate separation - Seismic-Induced contact may impair the safety function of the target to an unacceptable level. Corrective action is required.
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Where the walkdown identifies an installation or condition which will result in a seismic-Induced Interaction which could potentially Impair safety function to an unacceptable level, the installation is sketched or photographed and a written description of the concern is attached.
Recommendations for design or analytical solutions are also recorded.
Upon resolution of the concern, evidence is provided to document the adequacy of the final design. This record is retained in a final report and independently reviewed to assure adequate and consistant application of the methodology. Prior to final disposition the report functions as an open item list of outstanding concerns and suggested design changes.
The walkdowns are conducted during the final stages of construction to verify the adequacy of the installed separation between components. The scheduling of cubicles to be walked down is influenced by area accessibility and construction schedule. Buildings which have the highest percentage of completion are reviewed first. This allows the Interaction reviewer to observe the construction status at various stages of completion, identify potential interactions, and resolve any potential interactions which could result in extensive design changes which disrupt building completion schedules.
The reviewer examines the installation in each cubicle and assesses whether or not the existing clearance is adequate to preclude a seismic-induced interaction. Experience and engineering judgment is used to identify potential Interactions by assessing maximum relative seismic displacements. A visual examination determine the type and location of the component supports. Their capability to control movement during a scismic event is thln estimated.
For example, a pipe anchor does not permit significant seismic movement in any direction at
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the support point, whereas a rod hanger pipe support will only resist pipe movement vertically downward. A rod hung pipe can swing horizontally during a seismic event.
The spacing of the support points is also considered. Longer piping span lengths between support points, for example, have the potential for larger seismic displacements.
Similarly, inherent stiffness of each component in question is judged for its effect on seismic motion.
For example, a 4-inch diameter pipe is much stiffer than a 1-inch diameter pipe. Assuming an identical span between supports, a 1-inch diameter pipe will potentially be displaced farther than a 4-inch diameter pipe during a seismic event.
For cases where smaller components are being evaluated, the reviewer may physically shake the component under scrutiny in order to estimate its installed stifiness. This is a practical method for assessing system stiffness and expected displacements.
The influence of system or component mass distribution is considered, particularly when it is not uniform. Again taking the piping exampic, when in-line masses such as air operated or motor operated valves are located on piping, additional pipe displacement due to the mass is expected and included in the assessment of overall movement.
- 10. DOCUMENTATION The lleview Program uses the following documents to record potentially unacceptable seismic-induced interactions and to monitor their resolution. -
1.
Cubicie Maps which identify areas to be reviewed. (Attachment No.1).
2.
An Interaction Summary Listing which is a computerized tracking system for identified -interactions.
Each interaction is assigned an identification number.
The tracking program contains information describing the interaction location, the safety-related target, and the action required. The interaction. reviewer updates the Listing subsequent to each walkdown. This provides.a tracking system.which is used by the reviewer to monitor the progress of the walkdowns and resolution of identified interactions.
When an unacceptable interaction has been identified during the cubicle walkdown, the
- reviewer prepares a~one or two page detailed description of the concern called a Seismic
- Review Worksheet _(Attachment 2). As a minimum, a worksheet contains the following:
1..
The location of the interaction (building and cubicle number)..
2.
An interaction number which allows tracking with the Interaction Summary Listing.
3.
A description of the potentialinteraction.
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A photographic record or sketches of the interaction to help visualize the condition by reviewers.
' 5.
The criteria, assumptions and judgments used in reaching any conclusion or proposed solution.
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The Seismic Review Worksheets are filed sequentially by interaction identification number in. a' job book, kept by the reviewer.
Upon resolution of all concerns, the worksheets provide a permanent record of the evaluation process.
If it has been
. determined that.the interaction must be resolved using corrective measures, a summary of the corrective actions and associated reference documents used will be included in the file.
The following corrective measures (listed in general order of preference) are used to resolve unacceptable seismic-induced interactions.
1.
Use a simplified analysis to resolve the interaction concern resulting from worst-case assumptions about displacement or damage.
2.
Constrain the nonsafety component to prevent excessive seismic displacement.
3.
Install a barrier between the nonsafety component and the safety-related component.
4.
Relocate the nonsafety component so as to eliminate the hazard.
5.
Relocate the safety-related component.
The appropriate remedial measure is determined on a case-by-case basis. Any proposed corrective action is reviewed for its practicability regarding project cost and schedule
-impact.
Any analysis used to resolve interaction concerns will be documented in conformance with accepted engineering assurance procedures, applicable technical procedures, and project procedural requirements controlling such documents.
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1 ATTACHMENTS
- 1. Sample - Cubicle Map.
- 2. Sample -Seismic Review Worksheet..
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ATTACHMENT NO. 2 SEISMIC REVIEW WORKSHEET SEISMIC INTERACTION REVIEW PROGRAM MILLSTONE - UNIT 3 NUCLEAR POWER STATION Building: Intake Structure Interaction No. S-001 Cubicle: 200 & 201 Reviewer: Thomas K. Gillespie Problem Description / Evaluation / Resolution:
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Description:==
All chain-hung lighting units (6 observed) have open "S" hook @
connections.
Evaluation:
Historical seismic data has shown that chain hung lighting fixtures have slipped out of open "S" hook connections during a seismic event thereby resulting in complete loss of anchorage. Lighting units then become gravity missiles, targeting anything beneath them.
Resolution:
E&DCR F-E-38410 provides details / direction for providing positive I
anchorage of "S" hook connections. Subsequently, chain-hung lighting j
units pose no seismic interaction concern.
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