Public/Introduction to SQUG

The purpose of this web page is to answer the following questions about the Seismic Qualification Utility Group or "SQUG" and how the experience-based methods may be used for seismic qualification of nuclear power plant equipment.

Companies interested in SQUG membership are invited to email askepri@epri.com to discuss membership.

What is SQUG?

SQUG is an EPRI User Group that develops, maintains, supports, and broadens the use of earthquake experience data as a cost-effective method for seismic qualification of equipment.

What is the purpose of experience-based seismic qualification?

The experience-based method was originally developed by SQUG to provide a practical, cost-effective alternative to shake table testing and dynamic analysis to seismically qualify safety-related equipment installed in older U.S. nuclear power plants in response to the USNRC Unresolved Safety Issue (USI) A-46. International utilities also had to address similar requirements from their regulatory bodies to verify the seismic adequacy of equipment installed before more stringent seismic qualification methods were required. The SQUG methodology has been adapted as a cost-effective alternative for qualifying new and replacement equipment in the U.S. and internationally.

What is experience-based seismic qualification?

The method developed by SQUG is based on experience data obtained from the performance of equipment during earthquakes, supplemented by shake table test data. The methodology includes guidelines and criteria to screen out equipment that is similar to the equipment that performed well during earthquakes and shake table tests. The screening evaluations verify that the seismic capacity of the equipment exceeds the seismic demand that could be imposed on that equipment. A check is made to verify that the anchorage is adequate and that the equipment is not subject to adverse seismic interaction from nearby equipment and structures. The method includes guidelines and criteria to screen out from further consideration electrical relays that could be susceptible to “contact chatter" during seismic events. All these methods are documented in the Generic Implementation Procedure (GIP), developed by SQUG. The GIP includes all these guidelines and criteria in a comprehensive set of procedures with checklists.

Those items of equipment that do not pass the GIP screens are defined as “outliers.” Such items will not necessarily fail during a seismic event, but they simply fail to meet the conservative GIP screening criteria but may be shown to be adequate with further evaluations. SQUG has additional documents and methods for further evaluating outliers.

The GIP methodology can be applied to 20 "classes" of electric and mechanical equipment (e.g., pumps, valves, compressors, electrical cabinets, switchgear, and generators). The GIP also includes screening guidelines and criteria for evaluating relays, tanks, heat exchangers, and electrical cable and conduit raceways. In addition to these guidelines and criteria in the GIP, SQUG has recently developed guidelines and criteria for other classes of equipment including piping systems, HVAC systems, and overhead Cranes. Additional classes of equipment may be added in the future.

The SQUG method is also being applied for seismic qualification, design, and procurement of new and replacement equipment (NARE). The NARE Guidelines describe how to adapt the GIP guidelines and criteria including checklists for performing evaluations and developing procurement specifications.

What are the economic benefits of applying the experienced-based method?

For installed equipment, the experience-based method is a practical and cost effective method for seismic qualification, compared to dynamic analysis and testing. The cost savings for each of the 36 U.S. plants that were originally required to address USI A-46 is estimated to be more than U.S. $10 million. One of the principal benefits of using the SQUG methods for NARE is that the seismic evaluations can be completed relatively quickly, compared to performing analyses or shake-table testing, which reduces procurement time. Operability determinations, while nuclear units are on-line, can also be performed using the GIP method, thus avoiding potential shutdowns due to Technical Specification Limiting Condition of Operations (LCOs).

What are the benefits of membership in SQUG?

Each SQUG member has access to the products, tools, training, and engineering/management support for use in implementing the SQUG methodology at their facilities. Engineering contractors hired by a SQUG member may also gain access to these resources and tools to support the SQUG member in applying the experience-based seismic qualification methods. Listed below are some of the benefits of SQUG membership:

• Copies of the current Generic Implementation Procedure (GIP) are available.
• SQUG/EPRI reference reports are available here. These reports provide the background and data covering the earthquake experience database, anchorage evaluations, relay evaluations, in-cabinet amplification, storage tank and heat exchanger evaluation, and electric cable trays evaluation.
• EPRI offers sessions of SQUG training courses throughout the year depending on enrollment. Course availability and enrollment is at EPRI|U. The courses that SQUG has developed include the following:

Walkdown Screening and Seismic Evaluation Training Course (5-days)

Safe Shutdown Equipment Selection Course (2-days -- given in conjunction with the Electrical Relay Evaluation Course)

Electrical Relay Evaluation Course (2-days -- given in conjunction with the Safe Shutdown Equipment Selection Course)

Application of Experience Based Method to Seismic Qualification of New and Replacement Equipment (NARE) Course (2-days)

SQUG/NARE Awareness Training Course (1/2-day)

• SQUG has developed videos on the topics listed below. These may be viewed here.

SQUG Walkdown Course Excerpts – Introduction and Background

Introduction to SQUG Web Site

Questions & Answer Forums on SQUG Web Site

Differences Between NTTF 2.3 Seismic and USI A-46

Seismic Housekeeping

Seismic Verification of HVAC Duct and Damper Systems

Seismic Verification of Piping and Tubing

Seismic Verification of Overhead Cranes

• Access to the SQUG Subject Matter Experts for assistance in answering questions about applying the experience-based seismic qualification methodology.
• Participation by a representative at the annual SQUG meeting with input on actions to be taken by the group.
• Access to the SQUG web site, including access to the private sections of the web site for "SQUG Members only".
• Access to the web site containing the SQUG Earthquake Experience Database . The earthquake experience database on this web site can be used to verify that equipment has the attributes of the equipment that successfully withstood the effects of real earthquakes. This is the data that was used to initially develop the guidelines contained in the GIP.
• Access to other SQUG utility members in the U.S. and internationally using the SQUG List Server (SQUGLIST). SQUG member representatives also have access to and can interface with other members during annual SQUG meetings. Since all of the U.S. members and most of the international members have used the SQUG method extensively at their plants, they have extensive knowledge in how to apply the generic method to plant-specific applications. Interaction with other members can also allow others to implement elements of the SQUG method easier and faster. The collective experience of the membership, in conjunction with use of the SQUG method for USI A-46 and new and replacement equipment, can provide a cost effective way to apply the SQUG method.
• Access to other SQUG experience-based guidelines for evaluation the seismic adequacy of other systems and equipment beyond those covered in the GIP including:

-Overhead Crane Guidelines

-Piping and Tubing Guidelines

-HVAC Duct and Damper System Guidelines

-Benchmarking for Seismic Housekeeping at Nuclear Power Plants – Compilation of Industry Practices

-Portable Equipment Seismic Verification