History of SQUG
In December 1980,
the U.S. Nuclear Regulatory Commission (NRC) initiated Unresolved Safety
Issue (USI) A-46, "Seismic Qualification of Equipment in Operating
Nuclear Plants," to address the concern that there had been extensive
changes in the requirements for seismic qualification of equipment over the
years. The purpose of the USI A-46 program was to verify the seismic
adequacy of essential equipment in operating plants that had not been
qualified in accordance with more recent criteria.
In 1982, SQUG was formed to develop a practical approach for seismic
qualification of equipment in operating plants. The approach developed by
SQUG was to use experience data from the performance of equipment in power
plants and industrial facilities that had been exposed to actual earthquakes
as the primary basis for evaluating the seismic ruggedness and functionality
of essential equipment in nuclear power plants. Today, SQUG membership
includes U.S. utilities with nuclear power plants that had been subject to USI A-46. In addition, SQUG membership includes international utilities that have found the
experience-based method to be a viable, cost-effective method for seismic
qualification of equipment.
NRC Endorses Use of
In 1983, the NRC issued NUREG 1018, which includes a general endorsement of
the use of experience data for verification of the seismic adequacy of
equipment in nuclear plants.
In early 1987, the NRC issued
Generic Letter (GL) 87-02 [Reference 1] to owners of operating nuclear plants in the United States that were licensed prior to
development of modern seismic qualification standards. The recipients of GL
87-02 are referred to as A-46 plants. Essentially, all owners of A-46 plants
were members of SQUG. GL 87-02 required owners to take action to verify the
seismic adequacy of important equipment in their plants. A number of
International utilities with older nuclear power plant also joined SQUG to
address the same type of concern that the NRC had for older U.S. nuclear power plants.
To address the requirements in GL 87-02, SQUG developed the Generic
Implementation Procedure for Seismic Verification of Nuclear Plant
Equipment. The principal basis for the approach used in the GIP is the
successful performance of equipment in dozens of strong motion earthquakes in
hundreds of power plants and industrial facilities. This basis was
supplemented by results from shake table tests and analyses.
A significant finding of the
research upon which the GIP is based is that the conventional electrical and
mechanical equipment included in the scope of the GIP will withstand
earthquakes that are significantly higher than the design basis earthquakes
for eastern U.S. nuclear plants, provided the criteria outlined in the GIP
are met. The guidelines in the GIP provide a systematic, controlled, and
well-documented method of applying the lessons learned from review of
equipment performance during earthquakes and tests. The GIP screens out
those types of conventional equipment that have been shown to be insensitive
to earthquake motions expected in eastern U.S. plants and focuses on actual
equipment and installation vulnerabilities identified in strong motion
earthquakes and prior qualification tests. This process has been
demonstrated to be cost-effective in identifying risk-significant seismic
issues without reducing seismic design margins for the plants.
In addition to addressing the
issues associated with USI A-46, the GIP also explicitly addresses the issues
associated with methods of analysis for aboveground, flexible, vertical
storage tanks identified in USI A-40, “Seismic Design Criteria” [Reference 2]. Similarly, the GIP explicitly addresses the
seismic adequacy of equipment and structures that are in close proximity to
important-to-safety equipment identified in USI A-17, “Systems Interactions
in Nuclear Power Plants” [Reference 3].
SQUG issued several revision
of the GIP from 1988 to 1992 with new and improved criteria and guidelines.
The version issued on February 14, 1992, (GIP-2) included criteria and
guidelines that resulted from extensive discussions and subsequent agreements
reached with the NRC staff and the Senior Seismic Review and Advisory Panel
(SSRAP). As discussed below, the NRC identified this revision of the GIP as
the definitive version for implementing the USI A-46 program.
SSRAP Supported Use of
The Senior Seismic Review and Advisory Panel (SSRAP) assisted SQUG and the
NRC in reviewing this material and advising how best to apply this experience
data for verifying the seismic adequacy of equipment in the older nuclear
plants that were subjected to USI A-46. SSRAP produced two technical reports
to document their work and recommendations. These reports were later
complied into a single document and republished by Sandia National Laboratories,
SAND92-0140, UC-523, June 1992 [Reference 4]. Part I of this report includes the SSRAP report (originally published by SSRAP on 2/28/91) on “Use of Seismic Experience and Test Data to Show Ruggedness of Equipment in
Nuclear Power Plants” [Reference 5]. Part II of the
Sandia report includes the SSRAP report (originally published by SSRAP on 3/1/91) on “Review Procedure to Assess Seismic Ruggedness of Cantilever Bracket Cable Tray
Supports” [Reference 6].
Trial Plant Reviews
One of the key features of the approach used in the GIP is the use of a plant
walkdown of each item of equipment by experienced, trained seismic
engineers. To demonstrate the effectiveness of this approach, SQUG conducted
two trial plant reviews using an early version of the requirements in the
GIP. The first trial plant review was performed in 1987 on a PWR using experienced contractors as the review engineers. The second trial plant review was
performed in 1988 on a BWR using experienced utilities engineers as the
reviewers. Prior to both trial plant reviews, the walkdown engineers were
given training on use of the criteria and guidelines in a draft version of
the GIP that was available at that time. These trial plant reviews showed
that the criteria and guidelines in the GIP could be used successfully by
experienced, trained engineers to evaluate the seismic adequacy of equipment
and systems covered by the GIP. Both SSRAP and the NRC Staff supported this
NRC Accepts Use of GIP-2
After lengthy discussions between SQUG, SSRAP, and NRC Staff, agreement was
reached on the criteria and guidelines to be used for resolution of USI A-46. These agreements were incorporated into GIP-2
(GIP Revision 2, Corrected 2/14/92). The NRC Staff reviewed the revision of
the GIP and issued Generic Letter 87-02, Supplement 1 including Supplementary
Safety Evaluation Report No. 2 (SSER No. 2) in which GIP-2 was accepted as
the basis for SQUG members’ use in resolving USI A-46. The SQUG approach
embodied in the GIP was explicitly recognized by the NRC as the preferred
method for accomplishing the objectives of the USI A-46 program.
Nevertheless, the NRC identified certain clarifications, interpretations,
positions, and exceptions to the requirements in GIP-2 [Reference
7]. SQUG’s understanding of the clarifications, interpretations,
positions, and exceptions in SSER No. 2 were provided to the NRC in a letter
dated 8/21/92 [Reference 8]. The NRC commented on
SQUG’s understanding in a letter and enclosure dated 10/2/92 [Reference 9]. SQUG members committed to using GIP-2 plus SSER No. 2 as
the basis for resolving USI A-46 at their plants.
In March 1993, SQUG issued Revision 2A of the GIP (GIP-2A) to assist members in applying
GIP-2 in light of the clarifications, interpretations, positions, and
exceptions identified by the NRC in SSER No. 2. This augmented revision of
the GIP combined into a single document the guidance contained in both GIP-2
and SSER No. 2. Use of GIP-2A helped users avoid inadvertent errors that
would result from omitting or misinterpreting the NRC’s clarifications,
interpretations, positions, and exceptions as contained in SSER No. 2. SQUG
forwarded this augmented revision of the GIP to the NRC for review and
approval on 3/26/93 [Reference 10]. The NRC declined to
formally review and approve GIP-2A, stating that GIP-2 plus SSER No. 2 was
adequate for implementation of USI A-46 [Reference 11 ]. Nevertheless, SQUG advised its members that they should use GIP-2A as a
working level document in their day-to-day seismic verification of equipment
to avoid making inadvertent errors and omissions during resolution of USI A-46 [Reference 12].
SQUG Training Program
Since the criteria and guidelines in the GIP included new methods and
approaches, compared to the tradition methods for seismic qualification of
equipment, SQUG developed the following six training courses to help users
properly apply the various guidelines and tools developed by SQUG:
- Safe Shutdown Equipment Selection Training Course
- Relay Screening and Evaluation Training Course
- Walkdown Screening and Seismic Evaluation Training
- Add-On Seismic IPE Training Course
- New Replacement Equipment and Parts (NARE) Training
- SQUG/NARE Awareness Training
More details on these courses
and access to the training material associated for some of them are posted on
SQUG Training section of this web
site for use by members.
In 1995, a sister organization, called SEQUAL, was formed to extend the
use of the SQUG method to the newer nuclear power plants in the U.S. (i.e., the non-A46 plants). In 2003, SQUG and SEQUAL began operating together as a
single organization and are now referred to simply as SQUG.
In May 1997, SQUG issued Revision 3 of the GIP (GIP-3) to incorporate new information that
became available between 1992 and 1995 and to apply lessons learned during
implementation of the USI A- 46 program up to that point in time. This
revision included three additional restrictions beyond those in GIP-2,
namely: (1) use of lower allowable pullout capacities for certain types of
concrete expansion anchors, (2) increase in the cutoff frequency from 11 Hz
to 13 Hz for use of the in-cabinet amplification factor of 4.5 for certain
types of equipment containing essential relays, and (3) correction of an
equation for calculating allowable anchorage capacity for horizontal tanks
and heat exchangers. GIP-3 also included editorial and typographical changes
that clarified the meaning of the guidance in GIP-2. The NRC reviewed and
accepted GIP-3 in Supplementary Safety Evaluation Report No. 3 (SSER No. 3) [Reference 13].
In December 2001, SQUG issued an augmented revision of GIP-3 (i.e., GIP-3A) to assist members in applying
GIP-3 plus the clarifications, interpretations, positions, and exceptions
identified by the NRC Staff in SSER No. 2 and SSER No. 3 [References
7 and 13]. GIP- 3A also includes changes to address
the issues identified by the Staff in their review of the plant-specific
implementation of the USI A-46 program at the SQUG member plants and in their
review of SQUG's guidance on use of the GIP for New and Replacement Equipment
(NARE) [Reference 15] as incorporated into Revision 4 of
the NARE Guidelines [Reference 18].
By using GIP-3A, SQUG members
have a better chance of avoiding inadvertent errors that would result from
omitting or misinterpreting the NRC’s clarifications, interpretations,
positions, exceptions, and issues that are included in the two SSERs and
their letter to SQUG on the NARE Guidelines. SQUG recommended that members
use GIP-3A as a working level document for their day-to-day seismic
qualification of equipment in their plants, including New and Replacement
Equipment (NARE) [Reference 20].
In developing GIP-3A, SQUG
endeavored to incorporate the NRC clarifications, interpretations, positions,
exceptions, and issues in a manner that it believes would be acceptable to
the Staff without adding new, substantive criteria or guidance into the
document. Therefore, even though GIP-3A has not been formally reviewed and
approved by the NRC Staff, SQUG considers this document to be an additional
statement of the accepted criteria and guidance, not a change to the criteria
and guidance provided in the baseline documents that had been reviewed and
approved by the NRC Staff.
In addition to resolving USI A-46, the GIP method may continue to be used at USI A-46 plants for seismic qualification of new and replacement equipment (NARE). To assist
members, SQUG prepared a set of guidelines for applying the GIP for NARE and
sent a summary of the guidelines to the NRC Staff for review and approval (Reference 15). The NRC reviewed this document and provided
comments, including clarifications, on the application of the GIP method for
NARE (Reference 16). SQUG accepted the NRC’s
clarifications, produced Revision 4 of the NARE Guidelines, and sent these
guidelines to SQUG members on 7/25/00 (Reference 18 ). Subsequently, SQUG updated the NARE Guidelines in Revision 5 to reference
GIP-3A and make other improvements (Reference 19 ).
For SQUG members to use the
GIP method for seismic qualification of new and replacement equipment (NARE),
it is advisable, if not necessary, to modify the plant licensing basis to
allow use of the GIP as an alternative (see NRC letter to SQUG dated 6/19/98, Reference 14). To assist members in changing the plant
licensing basis, SQUG prepared Revision 0 of a 50.59 Template (Reference 17). This template is based upon the NEI
guidance available at the time for preparing 50.59 safety evaluations (NEI
96-07, Revision 0). Specifically, Section 3 of the template offers suggested
language to answer the seven questions from NEI 96-07, Revision 0. The
template also reflected the guidance provided by the NRC in their letter to
SQUG (Reference 14) in which the NRC agreed that the
50.59 process is an acceptable method to adopt the GIP, based on their
expectation that a detailed comparison of a plant’s licensing basis with
comparable elements of the GIP will be performed to support the 50.59
evaluation. Appendix A of the template compares typical elements in the
licensing basis for A-46 plants to comparable elements in GIP-3. This
comparison is intended to show that there is no reduction in the plant safety
margin. Appendix B of the template provides suggested language which may be
included in the plant’s USAR for adopting the GIP method as an alternative
seismic qualification method.
Subsequently, SQUG updated the
50.59 Template to Revision 1 (Reference 19) to make it consistent with the amendments made by the NRC to 10 CFR 50.59 that became
effective March 13, 2001, and the NEI guidance for applying this new 50.59
process, as contained in NEI 96-07, Revision 1. The 50.59 Template was also
revised to reference GIP-3A and make other improvements.
As discussed in the Mission Statement, SQUG continues
to maintain the validity of and support and broaden the use of earthquake
experience data as a cost-effective method for seismic qualification.
Various programs and projects continue to be pursued to support this mission.
1. Generic Letter
87-02, “Verification of Seismic Adequacy of Mechanical and Electrical
Equipment in Operating Reactors, Unresolved Safety Issue (USI) A-46,” U.S.
Nuclear Regulatory Commission, Washington, DC, February 19, 1987.
2. USI A-40 “Seismic Design
Criteria Short-Term Program”, USNRC, Washington, D.C.
3. USI A-17 “Systems Interactions in Nuclear Power
Plants” USNRC, Washington, D.C.
4. Sandia National
Laboratories Report SAND92-0140, UC-523, June 1992, containing two
reports originally published by the Senior Seismic Review and Advisory Panel
(SSRAP) on (1) Use of
Seismic Experience and Test Data to Show Ruggedness of Equipment in Nuclear
Power Plants, and (2) Review Procedure to
Assess Seismic Ruggedness of Cantilever Bracket Cable Tray Supports.
5. Part I of Sandia Report
SAND92-0140, UC-523 [Reference 0 above]: SSRAP Report, “Use of Seismic
Experience and Test Data to Show Ruggedness of Equipment in Nuclear Power
Plants,” originally published by SSRAP on 2/28/91.
6. Part II of Sandia Report
SAND92-0140, UC-523 [Reference 0 above]: SSRAP Report, “Review Procedure to
Assess Seismic Ruggedness of Cantilever Bracket Cable Tray Supports,” originally
published by SSRAP on 3/1/91.
7. Generic Letter
87-02, Supplement No. 1, Transmitting Supplemental Safety Evaluation Report
No. 2 (SSER No. 2) on SQUG Generic Implementation Procedure, Revision 2, as
Corrected on February 14, 1992 (GIP-2), U.S. Nuclear Regulatory Commission,
Washington, DC, May 22, 1992.
8. SQUG (N. Smith) letter to
NRC (J. Partlow), dated 8/21/92, describing SQUG’s understanding of SSER No.
9. NRC (J.
Parlow) letter to SQUG (N. Smith), dated 10/2/92, with enclosure containing
NRC Staff comments on SQUG’s 8/21/92 letter.
10. SQUG (N. Smith) letter to NRC (J. Partlow), dated
3/26/93, forwarding Revision 2A of the Generic Implementation Procedure (GIP-2A) along with a description of how
SQUG addressed the NRC comments in SSER No. 2 (Enclosure 2) and an
explanation of the clarifications made in GIP-2A (Enclosure 3).
11. NRC (W. Butler)
letter to SQUG (N. Smith), dated 5/24/93, NRC Response to SQUG Letter Dated
March 26, 1993, on GIP-2A.
12. SQUG (N. Smith)
memorandum to SQUG members, dated 8/4/93, Use of GIP Revision 2A.
13. NRC (J. Stolz)
Letter to SQUG (N. Smith), dated December 4, 1997, forwarding the NRC’s
“Supplemental Safety Evaluation Report No. 3 (SSER No. 3) on the Review of
Revision 3 to the Generic Implementation Procedure for Seismic Verification
of Nuclear Power Plant Equipment, Updated May 16,1997, (GIP-3).”
14. NRC (B. Sheron)
letter to SQUG (N. Smith), dated 6/19/1998, NRC Position of Use of 10 CFR
50.59 Process to Change Plant Licensing Basis to Adopt GIP Methodology.
15. SQUG (N. Smith) letter to
NRC (R. Capra) dated 7/15/1998, forwarding the Report on the Use of the GIP
for New and Replacement Equipment and Parts (NARE).
16. NRC (E. Adensam)
letter to SQUG (N. Smith) dated 6/23/99, forwarding the NRC’s Review of
SQUG’s Report on the Use of the Generic Implementation Procedure for New and
Replacement Equipment and Parts (NARE).
17. SQUG (J. Richards and R.
Kassawara) memorandum to SQUG members, dated 7/24/2000, forwarding the 50.59 Template, Revision 0,
“Template for 50.59 Safety Evaluations to Adopt the GIP as a Licensing Basis
(J. Richards and R. Kassawara) memorandum to SQUG members, dated 7/25/00,
forwarding the NARE
Guidelines, Revision 4, “Implementation Guidelines for Seismic Qualification
of New and Replacement Equipment/Parts (NARE) Using the Generic
Implementation Procedure (GIP).”
19. SQUG (J. Richards and R.
Kassawara) memorandum to SQUG members, dated 10/23/2002, forwarding the updated NARE Guidelines,
Revision 5 and the updated
50.59 Template, Revision 1.
(J. Richards) memorandum to SQUG members dated 6/14/2005, “Use of GIP
Revision 3A,” recommending that SQUG members use GIP-3A for future work,
including NARE applications.