Restrictions boundary conditions

1

• The Belgian reference concept

• Introduction
• Restrictions boundary conditions
• The concept anno 2000 (SAFIR 2)
• Open questions
• Future approach

2

• Introduction

• What is meant by concept ?
• Generic concept developed mainly for vitrified
  HLW
• Mainly focused on long term safety
• Technical feasibility (aim of PRACLAY)
• Actual situation RDD
• Open questions solved gt Design phase

3

• Boundary conditions

• Conclusions drawn from Safety Evaluations
• RN concentrations - relevant parameters - host
  rock Thickness, diffusion coefficient,
  retardation factor
• Confinement (retardation) capacity
• Boom Clay gtgt Engineered barriers

4

• Boundary conditions

• Consequences for the concept
• Maximise retardation thickness
• Repository location middle of host rock
• Minimise vertical extension
• Perturbations of host rock (excavation, heat,
  chemical,) should be reduced to a minimum

5

• Boundary conditions

• Thermal impact
• Normal scenario disposal of vitrified waste
  after 50 years of temporary storage
• Effects
• Near field thermal loading of engineered
  barriers
• Far field thermal loading of host rock and of
  water bearing sand layers

6

• Boundary conditions

• Impact of thermal load on disposal system
• Near field
• Tmax 130, actually reduced to 100C
• Function of overpack confinement during warm
  period
• Far field
• Host rock Tmax lt 100C no illitisation
• Groundwater 34C
• Regulatory requirements ?
• Possible effects precipitation of minerals
  micro-organisms,.

7

• Boundary conditions

• Gas production
• Caused mostly by anaerobic corrosion of steel
• Recent studies - vitrified waste gas will be
  transported by diffusion

8

• Boundary conditions

• Radiation
• Impact on Boom Clay limited
• Protection against radiation during
  transportation and exploitation phases
• Packages no contribution
• Transfer machine
• Remote controlled operations
• Plugging of galleries and of disposal tube

9

• Boundary conditions

• Host rock
• Thickness location disposal galleries
• Creep of Boom Clay need for a lining
• Lining calculated for multiple charges
  (lithostatic and swelling pressure, crossing of
  galleries, thermal, ..) during a certain period
  of time (retrievability ?)

10

• Boundary conditions

• Host rock
• Minimisation of EDZ (Excavation Damaged Zone)
• through
• Adequate excavation methods
• Adequate lining
• gt Information from PRACLAY

11

• Boundary conditions

• Other restrictions or requirements
• (Inter-)national legislation on mining activities
• Working conditions (ARAB, ventilation,..)
• Nuclear and conventional safety rules
• Practical feasibility
• Retrievability ?
• Robustness, flexibility and quality assurance

12

• The reference concept

13

• The reference concept

14

• Open questions

• Disposal tube (1 cm stainless steel AISI 316 L
  hMo)
• Behaviour under thermal load and under non
  -homogenous swelling pressure
• Water tightness
• Robustness
• Practical feasibility
• Overpack (3 cm stainless steel AISI 316 L hMo)
• Choice of material, dimensions, production
  process,

15

• Open questions

• Backfill (FoCa Clay prefabricated compacted
  blocs)
• Swelling pressure
• THM behaviour of the backfill - Hydration
  kinetics
• Optimal composition (60 clay 35 sand 5
  graphite) ?
• Installation practical issues - hydration
• Lining (concrete wedge blocs)
• Chemical compatibility
• Durability - retrievability
• Loads

16

• Open questions

• Lay-out of the repository
• Length and diameter of galleries (practical
  difficult.)
• Spacing between disposal galleries (thermal
  loading)
• Practical feasibility
• Remote controlled operations
• Installation of different components of the
  system

17

• Future approach

• Main characteristics
• Systematic, structural, progressive system
  approach
• Technical concept for each waste class
• Phenomenology FEP during different time periods
• Functional requirements - conceptual basis
• Safety
• Feasibility
• Monitoring
• Retrievability
• ..

18

• Future approach

• Finding a systematic and suitable response to
  the following questions
• What ? Description of each component of the
  system
• Why ? Justification of each component of the
  system
• How ? Description of practical realization of
  each component (fabrication, construction,
  installation,)
• When ? Calendar of realization of each component
  for different time periods

19

• Future approach

• Advantages of this approach
• Global approach of a disposal system
• Iterative process continuous improvements
• Definition of conceptual basis
• Traceability description forms information
  system

20

• Future approach

• Future steps
• Based on this conceptual basis
• Re-evaluation of current concept
• ?
• Adaptation of the current concept
• ?
• Decision on a reference concept
• Evaluation of PRACLAY experiment according to
  this reference concept