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Safety related aspects of cementitious materials for final disposal of radioactive waste

Safety related aspects of cementitious materials for final disposal of radioactive waste. Maarten Van Geet – ONDRAF/NIRAS Eef Weetjens - SCK •CEN. Overview. The origin of the supercontainer design The multifunction of the repository system and the components contributing to safety

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Safety related aspects of cementitious materials for final disposal of radioactive waste

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  1. Safety related aspects of cementitious materials for final disposal of radioactive waste Maarten Van Geet – ONDRAF/NIRAS Eef Weetjens - SCK•CEN

  2. Overview • The origin of the supercontainer design • The multifunction of the repository system and the components contributing to safety • The impact of the new design on safety assessment

  3. Origin of the Supercontainer design • After SAFIR 2, a new step in repository development has lead to the supercontainer design • This was based on several strategic choices • To include operational aspects within the design • To ensure complete containment during the thermal phase • Thermal phase is characterised by many transients and uncertainties • Avoid to have to perform safety assessments including these transients

  4. Multifunction of the repository system

  5. Components contributing to safety EBS

  6. Components contributing to safety EBS Mainly Boom Clay R1: limit release from waste R2: limit water flow R3: retardation of contaminants

  7. Why we rely mainly on Boom Clay for the safety function R « delay and attenuate »?

  8. Components contributing to safety EBS Mainly Boom Clay R1: limit release from waste R2: limit water flow R3: retardation of contaminants Boom Clay and the environment

  9. Boom Clay Impact of the new design on safety assessment - Containment Well constrained boundary conditions for corrosion to better underpin overpack integrity during thermal phase • IF high pH is maintained during thermal phase (presentation Wang & Jacques)

  10. Boom Clay Impact of the new design on safety assessment – limited RN release from waste form • pH/(Eh) conditions? • dissolution rate vitrified HLW? • corrosion rate of SF matrix? • BUT a long life time of the waste needs to be demonstrated before it significantly contributes to the overall safety (at least for vitrified HLW) • (Presentation Lemmens et al.)

  11. Boom Clay Impact of the new design on safety assessment – delay and attenuate releases by solubility limit Near Field: • pH/(Eh) conditions engineered barriers/Boom Clay? • RN speciation/mineral formation? • Concentration limits? Far Field: • No changes compared to other concepts • Extent of disturbed zone (Presentation Wang et al.)

  12. R R R R Boom Clay Impact of the new design on safety assessment – delay and attenuate releases by sorption Near Field • pH conditions engineered barriers/Boom Clay? • RN speciation? • Mineral composition and sorption characteristics of engineered barrier materials? • Extent alkaline plume? (Presentation Jacques et al.) Far Field • No changes compared to other concepts • Extent of disturbed zone (Presentation Wang et al.)

  13. How to deal with the uncertainties? • Large R&D programme on RN release, sorption and solubility data in clay conditions • Need for R&D to study these processes in high pH conditions (+ time evolution) • Need to know extent of the chemical disturbance of the Boom Clay (alkaline plume) • When uncertainties remain too high, fall back on conservatism used before (neglect near field in PA calculations)

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