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Backfill-Waste Interactions in Repository Simulating Tests

Published online by Cambridge University Press:  15 February 2011

Noriaki Sasaki ,
Sridhar Komarneni ,
Barry E. Scheetz  and
Rustum Roy
Noriaki Sasaki
Affiliation:
Tokai Works, Power Reactor and Nuclear Fuel Development Corporation, Tokai-Mura, Ibaraki-ken, Japan
Sridhar Komarneni
Affiliation:
Materials Research Laboratory, The Pennsylvania State University, University Park, PA 16802
Barry E. Scheetz
Affiliation:
Materials Research Laboratory, The Pennsylvania State University, University Park, PA 16802
Rustum Roy
Affiliation:
Materials Research Laboratory, The Pennsylvania State University, University Park, PA 16802
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Abstract

Candidate backfill materials such as montmorillonite and clinoptilolite with and without the presence of simulated nuclear waste solids such as borosilicate glass, glass ceramic, sintered ceramic and supercalcine ceramic were investigated under repository simulating conditions (=300°C and 30 MPa). Experiments were conducted under semi-wet as well as wet repository conditions.

Montmorillonite and clinoptilolite did not seem to alter under both semi-wet and wet repository conditions as determined by XRD. However, the above backfill materials reacted extensively with wastes under both conditions. They altered to feldspar (oligoclase) in the presence of borosilicate glass and to analcime in the presence of particular ceramics under both semi-wet and wet repository conditions. Alteration of montmorillonite could not be detected either in the presence of the glass ceramic or supercalcine ceramic under both repository conditions. However, clinoptilolite altered to analcime in the presence of glass ceramic or supercalcine ceramic under wet repository conditions. Reactions of backfill materials with simulated wastes immobilized waste elements such as Cs, Mo, etc., by forming new phases such as analcime, oligoclase and powellite. In fact, analyses of product solutions from interaction runs indicated that the presence of backfill materials during the alteration of waste solids served to drastically reduce the concentration of some radionuclides in solutions. These results suggest that properly selected backfills can provide the simplest and most effective chemical (or thermodynamic) engineered barrier in an intelligently designed multibarrier system. Moreover, they indicate that the μ, P, and T in the usual leach tests (e.g. Paige, IAEA, etc.) are such that results of such tests cannot have any value in evaluating waste form behavior under repository conditions.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 6: Symposium D – Scientific Basis for Nuclear Waste Management IV , 1981 , 397
Copyright
Copyright © Materials Research Society 1982

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References

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