APPLICATION OF THE GIP METHODOLOGY TO DEMONSTRATE SEISMIC ADEQUACY OF NEW AND REPLACEMENT EQUIPMENT AND PARTS IN USI A 46 PLANTS

Transcription

1 ~ r , This material may be protected by Copyright law (Title 17 U.S. Code) PVP-Vol Seismic Engineering - Volume 2 ASME 1994 APPLICATION OF THE GIP METHODOLOGY TO DEMONSTRATE SEISMIC ADEQUACY OF NEW AND REPLACEMENT EQUIPMENT AND PARTS IN USI A 46 PLANTS Patrick J. Butler MPR Associates, Inc. Alexandria, Virginia Stephen J. Eder EQE Engineering Consultants San Francisco, California Robert p, Kassawara Electric Power Research Institute Palo Alto, California ABSTRACT This paper discusses the guidance developed by the Seismic Qualification Utility Group (SQUG) for application of GIP methods to new and replacement equipment and parts. These SQUG guidelines address considerations unique to application of the GIP to new and replacement items including licensing requirements. differences between installed items and items yet to. be procured, differences in demonstration of seismic adequacy of parts versus equipment and equipment vintage issues. The SQUG guidance can be used by USJ A-46 utilities to develop plantspecific procedures for use of GlP methods whicb will satisfy their licensing basis seismic requirements. The resulting methods will be significantly more cost effective than current equipment qualification methods involving testing andlor analysis and will provide safety margins consistent with those demonstrated during resolution of US! A-46. INTRODUCTION The Generic Implementation Procedure (GIP) [1] was developed by SQUG to provide a generic approach for resolution of NRC Unresolved Safety hsue (USJ) A-46. USI A-46 was issued by tbe NRC due to concerns regarding the seismic adequacy of mechanical and electrical eq1!ipment needed for safe shutdown of plants constructed prior to current equipment seismic qualification criteria. Generic Letter [2], whicb fonnally issued USJ A- 46, Supplemental Safety Evaluation No_ 2 (SSER No.2) [3], which documents the NRC review and approval of the GIP, and the GIP include genecal provisions and guidelines for application of GlP methods to new and replacement equipment and parts II\Ided to US! A-46 plants. For the past two years, SQUG bas been developing more detailed licensing and technical guidelines to be included as a chapter in the SQUG Management Guidelines document yet to be published. The SQUG guidelines provide generic guidance for use of the GlP methodology for new and replacement equipment and parts whicb are added to any USJ A-46 plant. Specific requirements for seismic evaluation of new and replacement items vary from plant to plant depending on licensing basis seismic'requirements. In addition, implementation of the guidelines can vary from plant to plant depending upon procurement, design, Quality Assurance, plant design change and configuration control practices. The SQUG guidelines should be used to develop plant-specific guides and procedures for application of the GIP methodology to new and replacement equipment and parts which take into account the above considerations.. SQUG BACKGROUND USI A-46 and SQUG In 1982, SQUG, wbich consists of 34 U.S. utilities and 3 foreign utilities, was formed to develop a generic approa~h for resolution of USl A-46, "Seismic Qualification of Equipment in Operating Plants". Since application of "current criteria" to the installed equipment in these operating plants was not practical, an alternative approach was needed. SQUG, with support from the Electrical Power Research Institute (EPRI), developed an approach involving use of experience data, gatheced for standard industrial equipment types SUbjected to earthquakes, to assess the seismic adequacy of equipment in the operating plants. Development of the SQUG approach for mechanical and electrical equipment involved surveying the effects of real earthquakes on industrial equipment. collecting and documenting the earthquake experience data and demonstrating similarity between the nuclear plant equipment and the conventional power plant equipment that was surveyed. Experience data for equipment subjected to earthquakes with ground motions which 33

2 envelope nuclear plant ground motions was reviewed and characteristics of equipment which remained functional following the earthquake, referred to as inclusion roles. and seismic vulnerabilities which resulted in equipment failure, referred to as caveats. were identified. This process was applied to 20 different generic equipment classes and caveats and inclusion rules for each class were developed. A seismic capacity level. referred to as the "Bounding Spectrum", was generically established based upon the ground motions of the earthquakes surveyed. It applies to equipment which meets the caveats and inclusion rules for the twenty equipment classes. The process of gathering the experience data and developing the Bounding Spectrum is documented in Referen~ 4 and 5. A similar process was used to review seismic performance of equipment subjected to shake-table tests. Separate rules to define equipment to which this shake-table test experience data could be applied were developed. Class-specific seismic capacity levels. referred to as Generic Equipment Ruggedness Spectra (GERS) were established for some equipment classes based on the reviewed shake-table test experience. In general, the caveats and inclusion rules associated with GERS are more restrictive than earthquake experience data. The process of reviewing the test data and developing GERS is documented in Reference 6. SQUG documented the generic approach for use of experience data to evaluate equipment seismic adequacy in the "Generic Implementation Procedure for Seismic Verification of Nuclear Plant Equipment" for use by its members. Specifically, the GIP provides the licensing considerations, technical approach, generic procedures, personnel requirements, format and description of documentation requirements for use of experience data for resolution of US! A46. GIP Screening Criteria For the 20 classes of electrical and mechanical equipment for which SQUG had gathered experience data, Part II, Section 4 of the GIP provides four screening criteria for evaluation of seismic adequacy. These four screening criteria are as follows: Seismic capacity screening, Caveat and inclusion rule screening, Anchorage capacity screening, and Seismic interaction screening. Seismic capacity screening verifies that the seismic capacity of the equipment being evaluated exceeds the seismic demand placed upon it. Seismic capacity screening first involves determining the equipment seismic capacity from earthquake experience (Bounding Spectrum). Shake-table test experience (GERS) or from equipment-specific test data. if available. Equipment demand is determined from the plant-specific Safe Shutdown Earthquake (SSE) ground motion andlor in-structure response spectra approved by the NRC for the USI A46 review. An equipment item meets the seismic capacity screening if the capacity exceeds the equipment demand. Caveat and Inclusion Rule Screening verifies that the equipment being evaluated can be represented by the experience data gathered by SQUG. In order to pass this screening, the equipment must possess the general design attributes which define inclusion within the experience data (inclusion rules) and not possess attributes known or judged to result in seismic vulnerability (caveats). The GIP provides general inclusion rules and caveats for eacb class. The seismic review team personnel are expected to exercise engineering judgement to a significant degree when performing this screening. In addition, personnel must review the equipment and its subcomponents for any design details not addressed by the GIP caveats or uncommon situations which in their judgement could result in seismic vulnerabilities. Anchorage Capacity Screening verifies that the equipment anchorage and load path capacity and stiffness will be adequate to withstand the seismic demand loads. The OIP provides guidelines for field inspection and simple calculations for determining the anchorage capacity and guidelines for determining tbe seismic demand. Meeting this screening criteria requires that: the anchorage capacity exceeds the anchorage demand, anchorage installation inspections assure that the anchorage is free of gross defects, and evaluation of the load path from the anchorage to major SUbcomponents indicates adequate strength and stiffness. Seismic Interaction Screening verifies that the equipment will have no credible and significant spatial interactions with nearby equipment or structures which could compromise its safe shutdown function. Seismic interaction screening involves walkdown of the equipment to assure that there is: no potential for adverse contact with other equipment structures during seismic motion, no potential for failure of overhead structures or adjacent equipment, and adequate slack in attached electrical cable and piping. Relay Review Review of earthquake experience identified potential seismicrelated loss of function (inadvertent change of state) in industrial equipment due to chatter of relays or contactors. As a result, the GlP includes additional requirements for equipment whose safe shutdown function could be compromised due to chatter of relay or contactor devices. Section 6 of the GIP provides a process for verifying the seismic adequacy of these relays or contactors, referred to as "essential relays". This approach involves comparison of the seismic capacity assigned to the essential relay based on test data to the appropriate seismic demand which includes amplification of the earthquake motion by the cabinet structure between the equipment anchorage and relay mounting. In addition, an inspection of the relay installation within the equipment is required to assure structural adequacy of the relay mounting and to help quantify amplification by internal cabinet structures. the responsibilities and qualifications of individuals who implement the GIP screening criteria or perform the relay review. Personnel qualified to implement GIP screening criteria are referred to as "Seismic Capability Engineers" (SCE). SCE's are required to be degreed engineers (or equivalent). complete the SQUG-developed training course on seismic 34

3 adequacy verification of nuclear plant equipment and have at least five years experience in earthquake engineering applicable to nuclear power plants. Personnel qualified to perform relay reviews, tflead Relay Reviewers", are required to be degreed electrical engineers (or equivalent), and complete the SQUGdeveloped training course on the relay screening and evaluation procedure. Due to the high degree of engineering judgement required When applying the GIP screening criteria, completed documentation of evaluations are required to be reviewed and signed by two SCEs, one of which must be a registered professional engineer. PROVISIONS IN GIP AND SSER NO.2 Regulatory Bases The regulatory bases for use of the GIP for new and replacement equipment and parts are provided in Part I, Section 2.3 of the GIP with additional clarification provided in SSER No.2. Key excerpts from these documents are summarized as follows. The OIP methodology is an acceptable evaluation method, for USI A-46 plants, to satisfy equipment seismic requirements of General Design Criterion 2 and the purpose of NRC regulations relevant to seismic adequacy, including 10 C.F.R. Part 100 (see SSER No.2). The GIP methodology can be applied to new and replacement equipment within the scope of USI A-46 (see SSER No.2). USI A-46 plant licensees can change their seismic licensing basis to adopt the GIP methodology for replacement items within the scope of USI A-46 (see GIP and SSER No.2). Under certain conditions, the GlP methodology can be extended beyond the scope of the equipment reviewed under USI A-46, and be applied to all plant electrical and mechanical equipment within the scope of the GIP (See SSER No.2). The above provisions allow USI A-46 licensees to change their licensing bases to adopt the GIP methodology as an acceptable method for demonstrating seismic adequacy of new and replacement equipment and parts. Revision of Plant Licensing Bases The US] A-46 program involves verification of the seismic adequacy of equipment as a tfsnapshot in time". Once the A~46 program is complete, unless a licensee takes some additional action, the GlP no longer applies to seismic verification. New and replacement equipment and parts must conform to the applicable, plant-specific licensing basis requirements. As part of implementing the GIP methodology for new and. replacement equipment and parllo,licensees should perform a thorough review of their licensing basis requirements pertinent to equipment seismic qualification. These requirements can be found in the plant FSAR, Technical specifications and other docketed correspondence with the NRC. If review indicates that use of the GIP methodology for new or replacement equipment conflicts with these requirements, the licensee should revise their licensing basis following appropriate regulatory processes to adopt the GIP as an acceptable method for demonstrating seismic adequacy. If review indicates that use of the GIP does not conflict with the licensing basis, no licensing basis revision is necessary. However, it is recommended that the basis for use of the GIP methodology be clearly documented. Additional Requirements The GIP and SSER No.2 also impose additional requirements which must be met for new and replacement equipment and parts. These requirements address considerations appropriate to new and replacement equipment, which are not addressed in the GIP for USI A 46 resolution. Part I, Section of the GIP specifies that application of the GIP methodology to new or replacement equipment or parts shall be performed in accordance with the licensee's quality assurance and quality control requirements as defmed in applicable plant documents such as the FSAR, Quality Assurance Program Manual, plant procedures and Technical Specifications. As such, plant-specific procedures for application of the GIP methodology to new and replacement equipment and parts should be developed which are consistent with plant Quality Assurance requirements and are integrated with appropriate plant design, procurement, receipt, storage and modification procedures. Part I, Section of the GIP and SSER No.2 specify that when the GIP methodology is applied to new and replacement equipment or parts, evaluations should be performed in a controlled and systematic manner to assure that the particular part or equipment is properly represented in the experience data and that appropriate caveats and inclusion rules are met. In particular, each new or replacement equipment item or part should be evaluated for any design changes which could reduce its capacity from that reflected by the SQUG earthquake or shake table testing experience data and these evaluations should be documented. This requirement is imposed to address concerns that new and replacement items designed in the future may possess design characteristics and failure modes not addressed by existing caveats and inclusion rules and therefore are not represented in current experience data This requirement results' in wbat is referred to as a "design difference evaluation tf to identify these types of design characteristics and failure modes in new vintage equipment. Provisions in the GIP also prohibit use of the GlP methodology for new and replacement tanks and heat exchangers. APPUCATION OF GlP METHODOLOGY TO NEW AND REPLACEMENT EQUIPMENT Application of the GIP methodology to new and replacement equipment involves applying the four GIP screening criteria with the additional requirements as discussed above. Note that the GIP screening criteria are applicable to installed equipment. For new and replacement equipment, the GIP methodology will most likely be applied to equipment not yet installed or procured. Guidance for application of each of the four GIP screening criteria to new and replacement equipment is provided below. Seismic Capacity Screening Seismic capacity screening for new and replacement equipment differs little from seismic capacity screening perfolmed for installed equipment reviewed for USI A-46. The seismic capacity 35

4 level based on either earthquake or shake-table test data should be compared to the seismic demand from the licensing basis SSE ground or in-structure response spectra as appropriate and as described in the GIP. Caveat and Inclusion Rule Screening For new and replacement equipment this screening may include additional requirements. As with equipment screening done under USI A-46, the new or replacement equipment should be reviewed to assure that it meets the defmitions for the experience data equipment class (inclusion rules) and does not possess attributes known to result in seismic vulnerability (caveats). The review of the new or replacement equipment and its subcomponents must also address design differences (in new vintage equipment) which could result in reduced seismic capacity. This design difference evaluation should be documented. Anchorage Capacity Screening For new and replacement equipment this screening differs from that for equipment reviewed under USI A-46 because the equipment is not yet installed. In the case of new and replacement equipment, the GIP anchorage capacity screening requirements should be used to develop design and installation rules to assure anchorage adequacy. Design calculations should be prepared as necessary to assure that the new anchorage capacity is adequate, and installation specifications should be prepared to assure that the new anchorage is correctly installed. Note that if a replacement equipment item retains the bolt pattern of the previous equipment anchorage, then GIP allowable anchor capacities (factors of safety of about 3) can be used. However, if a new anchorage is designed for a new or replacement equipment item the GIP requires that manufacturers' allowable anchor capacities be specified (factors of safety of 4 to 5). Seismic Interaction Screening For new and replacement equipment this screening also differs from that for eqqipment reviewed under US! A-46 because the equipment is not yet installed. Like anchorage capacity screening, seismic interaction screening requirements should be applied as design rules and installation specifications which will preclude seismic interaction concerns for the new equipment. APPliCATION OF GIP MElllODOLOGY TO NEW AND REPLACEMENT PARTS Since the seismic reviews to resolve USI A-46 are performed at the equipment level, the GIP does not provide much specific guidance for explicit evaluation of parts and subcomponents. Section 6 of the GIP provides a method for evaluation relays. However, this method is not well suited for general application to new and replacement parts. General application of this method to new and replacement parts is not practical because it requires shake-table test data to establish part seismic capacity and determination of in-equipment amplification to establish seismic demand. However, for new or replacement relays, the relay review methods in Section 6 of the GIP should be used. Explicit capacity/demand comparisons are not required for parts (except essential relays) within equipment reviewed under USI A- 46. Instead. SeE's are required to examine equipment subcomponents and structural details to determine, using engineering judgement, if any unusual structural details, uncommon subcomponents or other potential seismic vulnerabilities exist. A similar approach is recommended for verifying the seismic adequacy of new and replacement parts (excluding relays). The steps included in the approach are discussed below. Demonstration That The Host Equipment Meets GIP Screening Criteria The first requirement (in the GIP and SSER No.2) is that the host equipment must meet the GIP screening criteria. If the host equipment cannot be demonstrated to meet GIP screening criteria, then GIP methods cannot be used to justify addition of the new or replacement part Evaluation Of Host Equipment Load Path This step assesses the effect of addition of the part on tbe adequacy of the anchorage and load path. For a new or replacement part, a SeE should determine if the load path from the added part to the host equipment anchorage will be adequate. This determination could be entirely based on judgement when small, low weight parts are to be added, or could involve Simple calculations to confrrmjudgements when larger, heavier parts are added. The intent of this evaluation is met if the SeE judges that the new or replacement part: will remain attached to the equipment, will not degrade the structural adequacy of the host equipment, and will not interfere with the required safety func~on and structural integrity of the host equipment and other parts. Functional Evaluation of New or Replacement Part A functional evaluation of the new or replacement part should be completed to determine if the part is required to function or maintain structural integrity to support the safety function of the host equipment (or any other equipment). If the functional evaluation indicates that the new or replacement part is not required to function or maintain structural integrity, then satisfying the above evaluation steps is sufficient to demonstrate that the host equipment continues to meet the GIP screening criteria following addition of the part If the part function or structural integrity is required, then verification of seismic capacity of the part is required. Verification of Seismic Capacity of New or Replacement Part This step verifies that the part will perform its intended function at the applicable level of seismic capacity of the host (or other) equipment as appropriate. This can be accomplished by one of the three following steps: Demonstrate that the new or replacement part is represented in the same experience data base (earthquake or shake table) applicable to the seismic capacity level of the host, Use part-specific qualification data, if available, employing the relay review approach in Section 6 of the GIP, or 36

5 Apply current seismic qualification methods (e.g., IEEE [7] or IEEE [8]) which include test or analysis. Each of these three options is discussed below. Evaluation of part representation in experience data is not explicitly required for each individual part within equipment reviewed under USI A-46. The equipment as a whole is verified to be represented in the equipment class. and. as part of inclusion rule and caveat screening. SeEs are required to inspect the equipment and its subcomponents for any design details not addressed by the GIP caveats or uncommon situations which in their judgement could result in seismic vulnerabilities. During this inspection, uncommon SUbcomponents or mounting configurations are identified. Various SQUG experience data reference documents [4,5,6 and 9] which describe the GIP equipment classes can be researched to determine the common subcomponents within each class. Note that this representation evaluation is required only for subcomponents whose function or structural integrity must be maintained in order to support the safety function of the host or other equipment. In general, these subcomponents can be identified in SQUG experience data reference documents and a determination regarding representation of the part can be made. If the part is demonstrated to be a common subcomponent of the equipment class within the experience data which is the basis for the host equipment seismic capacity, the part is acceptable. Reference 9 provides several example evaiuations demonstrating acceptability of new and replacement parts. When later vintage new or replacement parts are being evaluated, an additional design difference evaluation is required by the GIP and SSER No.2 which is intended identify design differences in later vintage parts which could result in reduced seismic capacity. This design difference evaluation should be documented. Part-specific qualification data can be used following the Relay Review process identified in Section 6 of the GIP and in Reference 10. This approach should be applied to new or replacement essential relays. Part-specific data from a shake-table qualification test can be used to establish the part seismic capacity. Since this part-specific data generally establishes the capacity at the location of the part mounting, the seismic demand to which this capacity is compared should include amplification of motion from the equipment anchorage to the part mounting. Guidelines for estimating in cabinet amplification are provided in the GIP and Reference 10. A new and replacement part is acceptable if the part-specific qualification data demonstrates that the part seismic capacity exceeds its demand. Use of current seismic qualification criteria ~ncluding IEEE or IEEE , is an acceptable option specified in the OIP for determining the seismic capacity of any equipment or part. Specifically. these criteria involve determination of seismic capacity by analysis, testing or a combination of test and analysis. Seismic capacity data for parts determined using Ibis criteria should be compared to the appropriate seismic demand to determine the seismic adequacy of the new or replacement part. DOCUMENTATION Documentation of new and replacement part seismic adequacy evaluations must meet more stringent requirements than the documentation requirements included in Section 9 of the GlP. The requirements in Section 9 of the GIP address the amount and level of detail of information that licensees are required to transmit to the NRC regarding results of their plant-specific USI A-46 reviews. When applied to new and replacement equipment and parts, the GIP methodology is being used to meet tbe.plantspeciflc licensing basis requirements pertinent to seismic qualification. Therefore documentation of these evaluations should meet pertinent plant-specific Quality Assurance program requirements. CONCLUSION The Seismic Qualification Utility Group (SQUG) has issued guidelines for application of the Generic Implementation Procedure (GlP) methodology to new and replacement equipment and parts installed in USI A-46 plants. These guidelines, to be included in a chapter of the SQUG Management Guidelines document, identify technical and licensing considerations which should he addressed when applying the GIP methodology to new and replacement equipment and parts. The guidelines include methods for application of the GIP methodology to new and replacement equipment and parts which address these technical and licensing considerations. These guidelines are also consistent with the regulatory provisions for application of the GlP methodology which are provided in the GIP and the NRC Supplemental Safety Evaluation No.2 (SSER No.2) of the GIP. In Spring and Fall of 1994, SQUG will he offering 3-day training courses covering application of the GlP methodology to new and replacement equipment Additional courses will be offered in 1995 based upon demand. REFERENCES 1. Seismic Qualification Utility Gropp, 2/14/92, "Generic Implementation Procedure (GlP) for Seismic V crification of Nuclear Plant Equipment, Revision 2, Corrected ,", Washington, D.C. 2. U. S. Nuclear Regulatory Commission, February 19, 1987, Generic Letter 87 ~02, "Verification of Seismic Adequacy of Mechanical and Electrical Equipment in Operating Reactors, Uuresolved Safety Issue, (US!) A-46," Washington, D.C. 3. U. S. Nuclear Regulatory Commission, "Supplemental Safety Evaluation Report No. 2 on Seismic Qualification Utility Group's Generic Implementation Procedure, Revision 2, Corrected February 14, 1992 for Implementation of GL (US! A-46), 'Verification of Seismic Adequacy of Equipment in Older Operating Nuclear Plants'," May 22, 1992, Washington, D.C. 4. Senior Seismic Review Advisory Panel (SSRAP), February , "Use of Seismic Experience and Test Data to Show Ruggedness of Equipment in Nuclear Power Plants." Revision Electric Power Researcb Institute, March 1991, Report NP- 7149, "Summary of the Seismic Adequacy of Twenty Classes of Equipment Required for Safe Shutdown of 37

6 Nuclear Plants, "Electric Power Research Institute, Palo Alto, CA, prepared by EQE, Inc. 6. Electric Power Research Institute, August Report NP- 5223, Revision I, "Generic Seismic Ruggedness of Power Plant Equipment in Nuclear Power Plants," Electric Power Research Institute, Palo Alto, CA, prepared by ANCO Engineers, Inc, 7. Institute of Electrical and Electronics Engineers, Inc., 1975, Standard IEEE , "IEEE Recommended Practice for Seismic Qualification for Class IE Equipment for Nuclear Power Generating Stations". 8. Institute of Electrical and Electronics Engineers, Inc., 1987, Standard IEEE "IEEE Recommended Practice for Seismic Qualification for Class IE Equipment for Nuclear Power Generating Stations", 9. EQE International, July Report TR-I "Database System of Power Plant Equipment Seismic Experience". 10. Electric Power Research Institute. December Report NP-7148, "Procedure for Evaluating Nuclear Power Plant Relay Seismic 'Functionality". Electric Power Research Institute. Palo Alto. CA. prepared by MPR Associates. Inc. 38