Geotechnical Aspects in Siting and Design of Nuclear Installations - Revision Update

Revision of NS-G-3.6 Geotechnical Aspects in Siting and Design of Nuclear Installations (DS531) Step 11 58thMeeting of the Nuclear Safety Standards Committee (NUSSC) 19-21 November 2024 Neda Stoeva Division of Nuclear Installation Safety External Events Safety Section International Atomic Energy Agency

Background IAEA Safety Guide NS-G-3.6 was published in 2004 and has not yet been revised. DS531 is a full revision of Safety Guide NS-G-3.6 and aims to: Align the recommendations with: GSR Part 2, Leadership and Management for Safety (2016) SSR-1, Site Evaluation for Nuclear Installations (2019) SSR-2/1 (Rev. 1), Safety of Nuclear Power Plants: Design (2016) SSR-3, Safety of Research Reactors (2016) SSR-4, Safety of Nuclear Fuel Cycle Facilities (2017) Expand the scope from Nuclear Power Plants to Nuclear Installations Incorporate lessons learned from significant geotechnical events Reflect current practices related to evaluation approaches, methodologies, and assessment techniques in Member States

Overview of the Document (1/2) TITLE of the Safety Guide NS-G-3.6: Geotechnical Aspects of Site Evaluation and Foundations for Nuclear Power Plants DPP DS531 proposed: Site Geotechnical Aspects for Design Basis of Nuclear Installations Draft DS531: Geotechnical Aspects in Siting and Design of Nuclear Installations Language considerations Draft DS531 language is consistent with IAEA Glossary & current IAEA Safety Standards Geotechnical aspects refer to the aspects of geotechnical site investigation, evaluation, engineering design and safety assessment related to the subsurface materials at nuclear installation sites Expanding text to close gaps Applicability of collected data and geotechnical parameters to evaluations for beyond design basis events & cliff-edge effects considerations Section 2 has been updated to reflect current practices and expectations related to site investigations, geotechnical data collection and other considerations Section 3 now focuses on Geotechnical Hazards (Major update of section on Liquefaction) Section 4 now focuses on Geotechnical considerations for Design and Evaluation Monitoring, graded approach and application of management system (Sections 5, 6 & 7)

Overview of the Document (2/2) This Safety Guide provides recommendations related to the geotechnical engineering aspects that are important to the safety of nuclear installations Site investigation planning Evaluation of geotechnical hazards Considerations for design and analyses Monitoring of geotechnical parameters Application of a graded approach for nuclear installations with limited risk Revision Updates: Consistency with most current Safety Standards Incorporation of latest knowledge and experience Incorporation of Lessons Learned from significant events Expansion of scope from NPPs to Nuclear Installations Restructuring into categories: Investigation, Hazards, Design Other changes: References updated

Status of the Document The DPP of DS531 was prepared in January 2021, approved by NUSSC in June 2021, and approved by CSS in November 2021. The first draft was developed in 3 consultancy meetings (2 virtual and 1 in-person)in 2021 and 2022. The draft document (Step 7) was approved by WASSC and NUSSC in November 2023. The document was posted on the IAEA website for Member States comments on 15 December 2023. Submission to the Committees after resolution of MS comments in August 2024. Comments were received from 1 WASSC Member and 7 NUSSC Members, including international organizations. The table with proposed resolutions was posted on the NUSSC website on 21 October 2024. WASSC approved DS531 for submission to CSS on 30 October 2024. Current step: Request for approval by NUSSC to proceed to CSS review and Step 12.

Member States Comments: Summary MEMBER STATE Comments UK 4 Turkiye 8 Switzerland 72 Spain 3 Total number of MS Comments 330 Russian Federation 36 Pakistan 14 Japan 8 Israel 5 Iran 8 Indonesia 6 India 10 Germany 86 Finland 16 ENISS 11 Egypt 12 Canada 9 Armenia 22 0 10 20 30 40 50 60 70 80 90 100

Member States Comments: Summary Number of MS Comments per Section 140 Section 1 Introduction 120 Section 2 Geotechnical site investigations, geotechnicaldata collection and other considerations 100 No. of Comments Section 3 Geotechnical Hazards 80 Section 4 Geotechnical considerations for Design and Evaluation 60 Section 5 Monitoring 40 Section 6 Graded approach Section 7 Management system 20 0 1 2 3 4 5 6 7 General Section

Member States Comments: Resolution Table Member States Comment Resolutions 330 MS Comments 109 Accepted 107 Accepted with Modification 33% 35% 114 Rejected 32% Accepted Accepted w/ Modification Rejected

SSC Member Comments: Summary and Resolutions WASSC 2 comments from 1 representative 2 Rejected Overview of SSC Comment Resolutions NUSSC 23 comments from 7 representatives 6 Accepted 11 Modified 6 Rejected 24% 32% Number of Comments per Section 44% No. of Comments 10 9 0 3 0 2 0 1 Accepted Modified Rejected Section

SSC Member Comments: High Interest Multiple comments were received by Member States and by SSC Members related to the title and approach presented in Section 6 Section 6 covers the Application of a Graded Approach The current text presents an approach which recommends a categorization of sites for nuclear installations based on radiological consequences of release consistent other Safety Standards As a result of the resolution of the comments the title of Section 6, the subsection on categorization and the title of Table 5 are now: 6. APPLYING A GRADED APPROACH TO GEOTECHNICAL ASPECTS IN SITING AND DESIGN OF NUCLEAR INSTALLATIONS CATEGORIZATION OF SITES FOR NUCLEAR INSTALLATIONS IN ACCORDANCE WITH THE RADIOLOGICAL HAZARD AS RELEVANT TO GEOTECHNICAL ASPECTS TABLE 5. CATEGORIES OF NUCLEAR INSTALLATIONS BASED ON THE POTENTIAL RADIOLOGICAL CONSEQUENCES AS RELEVANT TO GEOTECHNICAL ASPECTS The intent of the approach is to categorize the nuclear installation as a High, Medium, Low or Conventional hazard installation and then to apply the same categorization to the site and the relevant geotechnical aspects

SSC Member Comments: Summary Twenty-five (25) comments from WASSC and NUSSC - The comments were mainly editorial, for clarification, consistent use of terminology, and improved coherency with the other relevant IAEA Safety Standards - A few comments related to expansion of scope and level of detail presented were rejected, but will be noted for future revisions consideration - All comments were addressed and resolutions were provided The updated document and comment resolution tables have been shared, and no objections have been received.

Action Requested Approval by NUSSC to proceed to submission to CSS review and Step 12.

THANK YOU Neda Stoeva n.stoeva@iaea.org