Implementation ofgeometries relevant forgeological disposal ofintermediate or highlevel radio-active wastein HYDRUS 5.x and HPx
D. Jacques, J. Govaerts, S. Liu

Geological disposal of radioactive waste• Types of waste• Intermediate-level long-lived
waste (ILW)• High-level waste

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Multi-barrier system

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Principle – Contain and Isolate

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ISC: RestrictedChemical perturbation

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ISC: RestrictedImportant Questions• Long term geochemical evolution of the system• Long term durability and performance of engineered (and natural) barriers• Consequences for radionuclide migration
COUPLED REACTIVE TRANSPORTMODEL IS A CRUCIAL TOOLHYDRUS 5.x - HPx

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Different codes are used
MIN3P, Core, HITEC, iCP,…

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Why - What
Scopus search :Hydrus – radioactive : 29
Hydrus – radioactive – waste : 23
Hydrus – radioactive – waste – PHREEQC : 1• High-level waste – vitrified waste• Intermediate-level waste• Containers organic material• Bituminized waste
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Intermediate level waste
Waste package organic waste

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Intermediate level waste
Waste package organic waste• Drum with compacted organic waste• Backfilled with cementitious material (mortar)

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Intermediate level waste
Waste package organic waste• Drum with compacted organic waste• Backfilled with cementitious material (mortar)• Anaerobic degradation of organics
C6H10O5 + H2O  3 CO2 + 3 CH4• First-order degradation kinetics• Assumption – fully saturated conditions• Interaction dissolved CO2 with cement:carbonation
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Intermediate level waste
Simulation domain

Openings 5 cm

Cementitious material
carbonation

Steel (2mm)Waste
cellulose degradation

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Intermediate level waste
Simulation domain

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ISC: RestrictedProfiles 300 ypH

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SI CO2(g)calcite13

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Time series

6102214SCK CEN/53059029

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ISC: RestrictedVitrified high level wasteDisposal concept in (poorly)-indurated clay
France, Cigeo project

BelgiumGuo, X., Gin, S. & Frankel, G.S. Review of corrosion interactions between different materials relevant to disposalof high-level nuclear waste. npj Mater Degrad 4, 34 (2020).

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ISC: RestrictedVitrified high-level waste
1D-radial coupled reactive transport model

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HYDRUSSCK CEN/53059029

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Geochemical model• Model from B. Cochepin (ANDRA, France) (iCP)
Callovo-Oxfordian claystone (Marty et al., 2015)
Calcite, dolomite, siderite
Chlorite, illite, montmorillonite
Pyrite, quartz
Mostly Ca/Mg-exchanger (CEC = 17 meq/100g)
pH = 7, pCO2 = 10-2
Porosity = 18 %, De = 3x10-11 m2/s

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Cement Based Buffer: CEM I (Kosakowski, 2020)
W/C = 0.5, limestone aggregates
Portlandite, CSH 1.6, ettringite, monocarbo,hydrotalcite, calcite
pH = 13.4, Na-K-OH
Porosity = 11.5 %, De = 1x10-11 m2/s

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Portlandite dissolution
0y50 y100 y

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pHSCK CEN/53059029

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Portlandite dissolution front
54.5

Portlandite dissolution front (cm)

43.5
3
2.5

Concrete+Clay
Concrete - Coarse (0.5 cm)

2

Concrete - Fine (0.25 cm)

1.5
1
0.5
0050

100

150200250

300

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ISC: RestrictedVitrified high-level waste
and much more output…

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Intermediate level wasteBituminized waste form

• Drum not completely filled with bitumen• Under disposal condition, gap will befilled with water• Soluble salts (NaNO3, CaSO4) controls Na(several molals), Ca, S in water• Diffuse from drum
• Interaction with cement phases• mononitratealuminate
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Intermediate level waste
Bituminized waste form

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Intermediate level waste
Geometry

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Intermediate level wasteNaSCK CEN/53059029

50 ySimulations with too high D!!

150 y300 y

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Intermediate level waste
300 y

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mononitrate

Simulations with too high D!!

N(5)

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Conclusion• We demonstrate the versatility of HYDRUS 5 and HPx to deal with various
geometries relevant geological disposal• Geochemical evolution of engineered and natural barriers• Kinetic dissolution of waste forms• Interaction with cement• Alteration in host matrix• Showed examples need to be further developed and interpreted
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ISC: RestrictedAcknowledgement• European Joint-Programme EURAD “European Joint Programme on
Radioactive Waste Management” (Grant Agreement No 847593).

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ISC: RestrictedCopyright © SCK CEN
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