Towards SFC1 – where does the THM research fit in?

1. Towards SFC1 – where does the THM research fit in? Maarten Van Geet

2. Overview • Current status of the B&C program and the role of SFC1 • The safety strategy • The derivation of safety statements • The role of THM research • The role of research on chemical perturbations

3. Current status of the Belgian RD&D program on deep disposal • More than 30 years of research on geological disposal • Several state-of-the-art reports (SAFIR and SAFIR 2) with international reviews confirming the good perspectives of the possibilities of Boom Clay as host rock for geological disposal BUT • No institutional and/or political decision confirming geological disposal for long-term management of B&C waste  A stepwise process of key decisions proposed by NIRAS/ONDRAF

4. Key decisions to be taken in the reference repository development scenario • Go for geological disposal (in Boom Clay as reference host rock) • Decision-in-principle confirming geological disposal • Based on the Waste Plan + SEA • Trigger for societal dialogue (global and local) • Waste Plan foreseen around 2010 • Go for siting • Based on the Safety and Feasibility Case 1 – SFC 1 • For a given zone in the Boom Clay (as ref. host rock) • Safety, feasibility, including operational and costs • Requirements derived from the societal dialogue • SFC 1 foreseen around 2013

5. Key decisions to be taken (cont) • Go for licensing • Authorization to launch the detailed studies that will be necessary to build the license application files for a given site • Based on Safety and Feasibility Case 2 – SFC 2 and outcomes of local partnership • SFC 2 foreseen around 2020 • Go for implementation • Based on stepwise license applications and permits • EIA, construction then operation • Per waste group • Historic, dismantling, heat-emitting • License application for the 1st group around 2025 • Disposal operations from 2035 on

6. How to focus RD&D in view of SFC 1, given knowledge base, institutional uncertainties and limited resources? • Safety Strategy = process that • Supports development of any SFC that is to be presented to the authorities at key decision points • Is based on a define set of constraints (“boundary conditions”) • Aims at developing a concept (broad-brush description) and design (detailed specifications) that take due account of boundary conditions and knowledge base at the time of the decision • Aims at evidencing, through assessments and arguments that the proposed disposal system is safe and feasible

7. The safety strategy is an iterative process guiding the stepwise repository development and implementation Boundary conditions Safety strategy (process) Successive license applications SFCi (1 to n) Programme stage i

8. Boundary conditions- international guidance - Belgian legal and regulatory framework - ONDRAF working hypotheses - institutional policy - other stakeholder conditions

9. Strategic choices- high-level choices, with an impact on concept andon design- not a detailed assignment of safety functions for all different components over time- made early in the systematization and formalization process- are not expected to change much

10. Phases in repository evolution implied by the strategic choices made for heat-emitting wastes

11. Requirements: Top – Down Approach Concept Design

12. Requirements: Top – Down Approach Concept Design Assess adherence to requirements: Bottom – Up Approach

13. From “requirements” to “well-substantiated claims” or from top-down to bottom-up approach • SFC as a structured set of statements supported by evidence, arguments and analyses • When starting SFC: the statements take the form of requirements (“should”; top-down) • When all statements have become well-substantiated claims (“does”, “is”; bottom-up), the SFC can be finalised • Objectives of RD&D are • To provide adequate supporting elements for turning requirements into claims • To develop the appropriate tools to support this assessment

14. From “should” to “does”: an example for heat- emitting waste Require-ments top - down

16. Safety statements on THM Delay and attenuate Transport is diffusion dominated Self-sealing THM properties known to understand and model the short and long term behaviour Effects of excavation and ventilation known and do not limit the self sealing capacity Effects of thermal stress known and do not limit the self sealing capacity Chemical changes stemming from the waste emplacement do not limit the self sealing capacity The transport of gas through the host rock is sufficiently understood and will not significantly change the transport properties

17. THM research used in the safety case • Underpinning the necessary safety statements / function • Multiple lines of evidence • Deliver input enabling to derive scenarios • Explain the expected evolution • Indentify the remaining uncertainties • The eventual scenarios / assessment cases do not necessarily take into account the most up to date info from THM research • PA / SA calculations are always based on simplifications • In order to justify these simplifications, stay on the conservative side • HOWEVER: assessment basis should deliver its best knowledge and known remaining uncertainties and during interaction with PA/SA the simplifications and conservatism is chosen

20. Safety statements on chemical perturbations Delay and attenuate Transport is diffusion dominated Effects of excavation and ventilation known and do not limit the self sealing capacity Self-sealing … Host rock has favorable characteristics to retard radionuclides Sufficient chemical buffering against changes stemming from the waste emplacement Chemical disturbances of oxidation resulting from excavation and ventilation are known and the extent of the disturbance does not jeopardise the necessary thickness of the host rock Alkaline plume Temperature increase …

21. Research on chemical perturbations used in the safety case • Underpinning the necessary safety statements / function • Multiple lines of evidence • Deliver input enabling to derive scenarios • Explain the expected evolution • Indentify the remaining uncertainties • The eventual scenarios / assessment cases do not necessarily take into account the most up to date info concerning chemical perturbations • PA / SA calculations are always based on simplifications • In order to justify these simplifications, stay on the conservative side • HOWEVER: assessment basis should deliver its best knowledge and known remaining uncertainties and during interaction with PA/SA the simplifications and conservatism is chosen