Towards SFC1 where does the THM research fit in

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Towards SFC1 where does the THM research fit in?

• Maarten Van Geet

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Overview

• Current status of the BC 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

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Current status of the Belgian RDD 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 BC waste
• ? A stepwise process of key decisions proposed by
  NIRAS/ONDRAF

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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

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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

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How to focus RDD 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

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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
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Boundary conditions - international guidance -
Belgian legal and regulatory framework -
ONDRAF working hypotheses - institutional
policy - other stakeholder conditions
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Strategic choices- high-level choices, with an
impact on concept and on 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
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Phases in repository evolution implied by the
strategic choices made for heat-emitting wastes
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Requirements Top Down Approach
Concept Design
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Assess adherence to requirements Bottom Up
Approach
Requirements Top Down Approach
Concept Design
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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 RDD are
• To provide adequate supporting elements for
  turning requirements into claims
• To develop the appropriate tools to support this
  assessment

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From should to does an example for heat-
emitting waste
Require-ments top - down
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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
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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

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Safety statements on chemical perturbations
Delay and attenuate
Transport is diffusion dominated
Self-sealing
Effects of excavation and ventilation known and
do not limit the self sealing capacity

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

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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