Backfill material retention

DIN 52 459 1981 Testing of building sealants determination of the water absorption of backfill material retentive capacity. 

The effects of chemical interactions on the migration of radionuclides in the backfill material and in the ground can be described by the retention factor Kj, defined as ( )... 

Retention in the Backfill Material. The radionuclide holdup time in the backfill barrier for the KBS-concepts is in the order of thousands of years or less (15). Thus, only a few of the long-lived radionuclides in HLW and SUF ( °Sr, Cs and lAm) will be able to decay within the clay barrier and the more long-lived nuclides will just be delayed in their migration out into the bedrock. In the long-term time span the backfill material is of minor importance, as far as the retaining effect is concerned. 

Another field with a large potential for improvements concerns aluminosilicate minerals, which are of great importance in determining the chemistry of water in many types of rock. In backfill clays, aluminosilicates are responsible for the retention (sorption, incorporation) of trace elements and may affect both oxidation potential (incorporation of Fe(II)/Fe(III)) and pH (hydrolysis of silicate and/or exchange of H+). Related classes of compounds (i.e., calcium silicates and calcium aluminates) form the chemical backbone of cementitious materials. The thermodynamic properties of these substances are still largely unexplored. 

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