DS563 - Seismic Design for Nuclear Installations

Status: STEP 3

Revision von SSG-67

Beteiligte IAEO-Komitees: NUSSC, WASSC

Specific Safety Guide

Zurück zur Übersicht "In Entwicklung befindliche Safety Standards"

This Safety Guide, based on general practices in Member States for concepts such as design basis earthquakes, seismic categorization of structures, systems, and components  and guidance on seismic design, analysis, qualification, and seismic instrumentation, includes recommendations for plant layout, required geotechnical parameters, and seismic design rules for civil structures, piping, and equipment, as well as qualification methods including analysis, testing, and earthquake experience.

It is recognized that there are steady advances in technology, scientific knowledge, regulations, and events that prompt the update and revision of IAEA Safety Standards. The following are some of the issues that have emerged since the publication of the current Safety Guide in 2021 and prompt an update:

• the rapid development of small modular reactors (SMRs) and advanced nuclear technologies, including non-water cooled reactors (non-WCRs), has introduced novel structural types and configurations that require updated seismic design recommendations to ensure safety while accommodating innovative reactor designs;
• there is a growing need for clearer recommendations on applying a graded approach to seismic design, tailored to the specific hazards and characteristics of diverse nuclear installations, to optimize safety measures without over-conservatism;
• trends toward risk-informed and performance-based principles and practices in seismic design have evolved, enabling better understanding of seismic risks, more balanced designs, and quantifiable safety goals that align with probabilistic safety assessments;
• advancements in computational techniques and increased computing capacity have enhanced capabilities for complex seismic analyses, such as nonlinear soil-structure interaction and site response modelling, allowing for more accurate and efficient design processes;
• the accumulation of seismic experience from past events, including the Chūetsu offshore earthquake (2007) and the Tohoku earthquake (2011), continues to provide valuable lessons on building responses, sloshing effects in pools, and the effectiveness of good practice design rules, even under motions exceeding design levels.

So, current revision is driven by the need to address evolving nuclear safety practices, technological developments, and feedback from Member States.

Based on the result of this analysis, key drivers for this revision include the following themes, which are elaborated further in the Annex of DPP, are:

1. Development of advanced nuclear technologies such as small modular reactors (SMRs), non-water cooled reactors (non-WCRs), floating nuclear power plants (FNPPs), transportable nuclear power plants (TNPPs), and fuel cycle installations.
2. Emphasis on the application of a graded approach.
3. Evolution of methods for performing beyond design basis evaluations.
4. Experience-based qualification methods.
5. Incorporation of risk-informed performance-based design principles for enhanced risk understanding and balanced design.

Furthermore, this revision will be developed in close coordination with IAEA Safety Standards Series No. SSG-68, “Design of Nuclear Installations Against External Events Excluding Earthquakes.” Owing to the differing modes of impact on structures, systems and components, it is considered necessary that SSG-67 and SSG-68 be revised as separate safety guides. However, close coordination remains essential, in particular with respect to the consistency of design approaches and criteria, as well as the consideration of the combination of external events.