STRATEGY FOR SAFETY CASE DEVELOPMENT: IMPACT OF A VOLUNTEER APPROACH TO SITING A JAPANESE HLW REPOSITORY

Transcription

1 STRATEGY FOR SAFETY CASE DEVELOPMENT: IMPACT OF A VOLUNTEER APPROACH TO SITING A JAPANESE HLW REPOSITORY K. Kitayama, K. Ishiguro, M. Takeuchi, H. Tsuchi, T. Kato, Y. Sakabe, K. Wakasugi Nuclear Waste Management Organization of Japan (NUMO) SAFETY CASE FOR THE DEEP DISPOSAL OF RADIOACTIVE WASTE: WHERE DO WE STAND? JANUARY

2 Development of the Japanese HLW Disposal Program R&D Start of R&D Program Second Progress Report (H12) (Technical Reliability) First Progress Report (H3) (Technical Feasibility) R&D Program of supporting Organizations 2040 Repository Operation (around 2035) Selection of Disposal Site (around 2025) Commencement of Open Solicitation (Dec. 2002) 1976 "Specified Radioactive Waste Final Disposal Act" (June. 2000) Establishment of NUMO as the Implementing Organization (Oct. 2000) Implementation 2

3 Three Stages of the Site Selection Process PIAs: Preliminary Investigation Areas DIAs: Detailed Investigation Areas PIAs DIAs Repository Site Volunteers Selection of PIAs Investigation areas: Volunteer areas and their surroundings Investigation methods: Literature surveys Selection of DIAs Investigation areas: PIAs Investigation methods: Initial surface exploration; boreholes, geophysics, etc. Selection of repository site Investigation areas: DIAs Investigation methods: Detailed surface exploration plus characterisation in underground facilities 3

4 Practical Constraints ? Solicitation All municipalities LS All volunteers PI Up to 5 PIAs Decision point - for LS, geological stability (EFQ) - for PIA, ease of making basic safety case - for DIA, provisional safety case - for Site, safety case for licensing around 2025 DI 2 DIAs 4

5 Structure of Information Package for Open Solicitation Level 1 Open Solicitation of Candidate Sites for Safe Disposal of High-Level Radioactive Waste Level 2 Instructions for Application Repository Concepts Siting Factors Outreach Scheme Level 3 Development of repository concepts for volunteer siting environments Scientific background and practical application of NUMO s repository siting factors Other Supporting Documents Video Booklet - H12 report - Study on Implementation Techniques for HLW Disposal (by utilities), etc - JSCE reports - Catalogue of Quaternary Volcanoes in Japan - H12 report, etc 5

6 Outline of Literature Survey (LS) Schedule LS stage PI stage Siting Factors for PIAs LS Plan Collection, Summarization and Assessment of Literature Information Assessment for Selection of PIAs Feasibility Study of System Design and Performance Assessment PIA Selection Report RC Development Report Siting Factors for DIAs PI Plan Surface-Based Investigations 6

7 Key Elements for assembling a Safety Case 7

8 Siting Factors for PIAs Selection (LS stage) Evaluation Factors for Qualification (EFQ) Factors to assess compliance with legal requirements for PIAs, which are relevant to: Favourable Factors (FF) Earthquake / fault activity Igneous activity Uplift / erosion Unconsolidated Quaternary deposits Mineral resources Factors to assess characteristics of PIA comprehensively (and comparatively) for areas where compliance to the legal requirements has been confirmed, which are relevant to: Legal requirements of DIA selection and repository site selection Practicality of repository construction and operation 8

9 Requirements for NUMO s Safety Evaluation Deal with a range of repository concepts and a variety of volunteer sites Major extension from H12: - Evaluate pre-closure safety and engineering practicality - Evaluate post-closure safety more realistically and develop relevant tools - Develop tools enable more rigid coupling of siting, design and PA - Develop supporting management tools 9

10 The NSA: Application to RC Development The NUMO Structured Approach (NSA) is a methodology for developing designs which: Tailors repository concepts to sites in a transparent manner Responds to increasing site understanding Allows for developments in science & technology Accepts potential changes to socio-political boundary conditions over the long implementation period Feedback provides identification and prioritisation of Site characterisation goals R&D to support design & PA 10

11 LS Stage Stepwise Development of Safety Case - Data source: literature information for the site, complemented by generic and international experience - The largest uncertainties with the geological environment - EBS or near-field processes provide a robust safety case - Qualitative arguments may provide strategy and guidance for the development of the RC and safety case at later stage. PI Stage - More quantitative evaluations based on surface geological investigations and modelling - Detailed coupling between site investigation, design and PA are critical for repository development. - An emphasis may still be placed on EBS performance in siteswith limited geological information. 11

12 Stepwise Development of Safety Case (continued) DI Stage - Site specific data from investigations in the underground characterization facility available, with additional boreholes and detailed geophysical surveys - Safety case required to be more convincing and complete to justify the construction of a repository at a selected DIA, and to demonstrate compliance with regulations - All relevant interactions between the EBS and natural barriers considered in design optimization - All safety relevant information from diverse sources integrated into the entire safety case Stages after licensing (construction/operation/closure) - Safety case evolves to maintain state-of-the-art, with input from characterization during construction and experience gained during operation, and monitoring. 12

13 Conclusions NUMO`s strategy for safety case development is constrained by staged siting and the volunteering approach. NUMO s safety case is developed iteratively in the framework of the NUMO Structured Approach. At early stages of siting, major components of the safety case will be regularly documented in technical reports. Discussion of later safety case documentation continues. Items important for safety case development include : - Linkages between site investigation, repository design and performance assessment - Emphasis on near-field processes / robust EBS at early stages - Integration of operational phase safety and engineering system practicality into the total safety case 13

14 Further Information on: 14