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Characteristics of Bitumenized Radioactive Wastes

Objective

The objective of this study is to investigate the leaching behaviour of bitumen encapsulated representative and homogeneous reprocessing sludges or concentrates wastes under geological disposal conditions.
The influence of the bitumen matrix and the type of waste treated will be closely examined in realistic disposal scenarios.

Work programme:

The present study will include comparison of Eurobitum and M80/100, M40/50 and MR90/40 in regards to efficiency confinement of radioactivity.
The tests that should enable the evaluation of encapsulation stability are steady leaching tests in different media conditions such as water (CEA Cadarache and Saclay), cement/clay mixture and clay/clay water mixture (SCK Mol and CEA Saclay) with different size samples ranging from a few cm{3} to the full size bitumen block.
Understanding of water uptake in and release of dissolved materials when bitumenized materials are disposed of under saturated as well as unsaturated conditions and quantification of swelling, swelling pressure and leaching phenomena are improved by RISØ National Laboratory.
The small size samples of bitumenized co-precipitation sludges will be prepared by CEA Cadarache.
Uptake of water into bitumenized waste is important for the understanding of the long-term behaviour of the material.
Diffusion of tritiated water and 134Cs ions is studied using membranes made from pure bitumen, bitumen mixed with crystals of soluble salts such as NaNO3 or with insoluble sludge particles, for example BaSO4. The measurements of the amounts of diffused materials are supplemented by measurement of the electrical conductivity over the membrane to give additional information about the migration mechanisms and the quality of the membranes.
Unrestricted swelling, water uptake and Na-leaching from samples of bitumenized materials containing soluble salts are followed using a weighing technique and chemical analyses of the leachants.
Pressure development due to water uptake in confined samples of similar materials is also investigated using a technique where swelling caused by water penetrating through a cement mortar barrier results in replacement of mercury from a bottom reservoir up in a long capillary tube.
A research model describing the water uptake in bitumenized materials containing soluble salt has been developed. The dynamics of the swelling and the generation of an internal solution-filled pore structure are modelled on the micro scale. Some simplifying assumptions about geometry of the system, etc. are made.

Funding Scheme

CSC - Cost-sharing contracts

Coordinator

Commissariat à l'Energie Atomique (CEA)
Address
Centre D'études De Cadarache Sere-ders
13108 Saint-paul-lez-durance
France

Participants (4)

BELGIAN NUCLEAR RESEARCH CENTRE
Belgium
Address
200,Herrmann Debrouxlaan 40-42
1160 Bruxelles
Commissariat à l'Energie Atomique (CEA)
France
Address

91191 Gif-sur-yvette
NATIONAL AGENCY FOR RADIOACTIVE WASTE AND ENRICHED FISSILE MATERIALS
Belgium
Address
01,Avenue Des Arts 14
1210 Bruxelles
RISOE NATIONAL LABORATORY
Denmark
Address
Frederiksborgvej 399
Roskilde