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Immobilization of Simulant ILW Actinide Wastes Containing Halides: Effect of Process Parameters on Wasteform Properties

Published online by Cambridge University Press:  21 March 2011

Brian L. Metcalfe ,
Shirley K. Fong  and
Ian W. Donald
Brian L. Metcalfe
Affiliation:
Materials Science Research Division, Atomic Weapons Establishment, Aldermaston, Berkshire, RG7 4PR, U.K
Shirley K. Fong
Affiliation:
Materials Science Research Division, Atomic Weapons Establishment, Aldermaston, Berkshire, RG7 4PR, U.K
Ian W. Donald
Affiliation:
Materials Science Research Division, Atomic Weapons Establishment, Aldermaston, Berkshire, RG7 4PR, U.K
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Abstract

The applicability of a process, originally developed to immobilize a chloride-rich intermediate level waste (ILW) arising from the pyrochemical reprocessing of plutonium, to alternative ILW waste-streams containing a large variety of cations, present as oxides together with KCl and CaF2, has been investigated. Non-radioactive studies, using simulated wastes containing hafnium and samarium as surrogates for the actinides, have been performed to establish the optimum processing parameters for the manufacture of wasteforms suitable for long-term storage/disposal. It has been demonstrated that the wastes can be immobilized by calcining with either Ca3(PO4)2 or CaHPO4 as the host. In excess of 97.5 % of the chloride present in calcined wastes, containing up to 3.2 wt% halides as a mixture of F- and Cl-, is immobilized when using this process. Whereas in the original calcined waste, the Cl- (about 12 wt%) was immobilized as chlorapatite, Ca5(PO4)3Cl, and spodiosite, Ca2(PO4)Cl, in these current wastes fluorapatite is the predominant halide containing phase. Conversion of the immobilized waste powder into a monolithic wasteform was achieved by sintering the powder with the addition of a sodium aluminium phosphate based glass. Both the calcined powder and the sintered monolithic wasteforms showed excellent durability in aqueous solution.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 932: Symposium – Scientific Basis for Nuclear Waste Management XXIX , 2006 , 42.1
Copyright
Copyright © Materials Research Society 2006

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References

REFERENCES

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