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Mass Transfer in Water-Saturated Concretes

Published online by Cambridge University Press:  21 February 2011

Alan Atkinson ,
Peter A. Claisse ,
Andrew W. Harris  and
Allan K. Nickerson
Alan Atkinson
Affiliation:
Materials Development Division, Harwell Laboratory, Oxon OX 1 ORA, UK
Peter A. Claisse
Affiliation:
Materials Development Division, Harwell Laboratory, Oxon OX 1 ORA, UK
Andrew W. Harris
Affiliation:
Materials Development Division, Harwell Laboratory, Oxon OX 1 ORA, UK
Allan K. Nickerson
Affiliation:
Materials Development Division, Harwell Laboratory, Oxon OX 1 ORA, UK
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Abstract

Cements and concretes are often considered as components of barriers for the containment of radioactive waste. The performance of such materials as mainly physical barriers to the transport of dissolved radionuclides depends on the mass transfer characteristics of the material. In particular the diffusion and sorption behaviour of the radionuclides and the water permeability are important. These parameters also influence how the chemistry of the concrete is imposed on the repository. In addition, the transport of gas through concrete controls the way in which gases escape from the repository.

Diffusion and gas transport have been measured in a variety of cementitious materials, covering both structural concretes and cementitious backfills; all possible repository construction materials. Measurements have been made using aqueous iodide, strontium and caesium ions and tritiated water as diffusants. The results show that the diffusion of tritiated water is more rapid than that of other species, whilst the transport of strontium and caesium is hindered by sorption; particularly in materials containing blast furnace slag. The transport of gas in these materials has been found to be very sensitive to the degree of water saturation and is extremely low in fully saturated structural concretes. Cementitious backfills have, nevertheless, been identified that have appreciable gas transport even when almost water saturated.

The consequences of the results for the performance of cementitious barriers are discussed.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 176: Symposium U – Scientific Basis for Nuclear Waste Management XIII , 1989 , 741
Copyright
Copyright © Materials Research Society 1990

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References

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