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Impact of Additives and Waste Stream Constituents on the Immobilisation Potential of Cementitious Materials

Objective

The objective of this tri-coordinated research programme is to determine the interactions between waste and cementitious materials, in real waste forms, and also to explain the sorption phenomena of transuranics and relate laboratory data to the performance of realistic cemented waste forms within a repository.
The studies will be used to strengthen the links between empirical studies eg. leaching, and more fundamental aspects. They will also be used to determine the impact of the waste itself, both active and non-active, on the properties and performance of the encapsulating cement.
The objective of this tricoordinated research programme is to determine the interactions, between waste and cementitious materials, in real waste forms and also to explain the sorption phenomena of transuranics and relate laboratory data to the performance of realistic cemented waste forms within a repository. The studies will be used to strengthen the links between empirical studies, eg leaching, and more fundamental aspects. They will also be used to determine the impact of the waste itself, both active and nonactive, on the properties and performance of the encapsulating cement. A literature study on the sorption of radionuclides has been carried out. In addition, a large data base containing stability constants relevant to the present project was set up. 3 methods for the measurement of uranium have been evaluated: liquid scintillation counting, spectrophotometry, and a polarographic method which is currently undergoing assessment.
Work programme:

Various techniques will be used in the measurement of aqueous phase and solid phase compositions of cement and blended cement, using inactive controls as well as formulations containing real wastes. Separation factors will be calculated for various isotopes in the above systems. The sorption processes for certain transuranics will be determined on pure cement phases and the role of certain organic complexing agents determined. The impact of selected inorganic ions on cement performance at longer ages will also be measured. The above experiments will be carried out at three isotherms: ambient ( 22 ), 55 and 80 C.
Preparation of blended cements incorporating radioisotopes and process chemicals.
Trial runs at elevated temperatures on modified pore fluid expression device.
Pore fluid extraction of the samples prepared, and measurement of radioisotope sorption for the various cement blends and ultimately on real wastes.
Synthesis and characterization of phase pure cement hydrates for sorption studies.
Sorption of Eu(III) or Am(III), U(VI), Th(IV), Np(V) and Pu (on a reduced scale) on the above cement hydrates.
Study the specific nuclide interactions (Ni, Cl, I and Cs) with cementitious materials.
Study the impact of chloride, carbonate and sulphate on cement performance.
Verification of mineralogy of phase pure cement hydrates.

Coordinator

University of Aberdeen
Address
Regent Walk
AB9 1FX Aberdeen
United Kingdom

Participants (2)

FREIE UNIVERSITAET BERLIN
Germany
Address
Kaiserswertherstrasse 16-18
Berlin
United Kingdom Atomic Energy Authority (UKAEA)
United Kingdom
Address
Winfrith Technology Centre
DT2 8DH Dorchester