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Further Studies of Synroc Immobilization of HLW Sludges and Tc for Hanford Tank Waste Remediation

Published online by Cambridge University Press:  10 February 2011

E.R. Vance ,
K.P. Hart ,
M.L. Carter ,
M.J. Hambley ,
R.A. Day  and
B.D. Begg
E.R. Vance
Affiliation:
Materials Division, ANSTO, Menai, NSW 2234, Australia
K.P. Hart
Affiliation:
Materials Division, ANSTO, Menai, NSW 2234, Australia
M.L. Carter
Affiliation:
Materials Division, ANSTO, Menai, NSW 2234, Australia
M.J. Hambley
Affiliation:
Materials Division, ANSTO, Menai, NSW 2234, Australia
R.A. Day
Affiliation:
Materials Division, ANSTO, Menai, NSW 2234, Australia
B.D. Begg
Affiliation:
Materials Division, ANSTO, Menai, NSW 2234, Australia
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Abstract

Synroc/glass composites were designed for simulated Hanford HLW sludges containing U (the current “All-Blend” formulation). The composite contained ∼ 50 wt% of simulated HLW (oxide equivalent), to which ∼ 6, 10, 10, and 24 wt% of CaO, Al2O3, TiO2 and SiO2 were added, and melted under an argon atmosphere at 1350°C. The phase assemblage consisted of zirconolite, perovskite, spinel, nepheline, whitlockite and glass as major phases. Seven-day PCT tests yielded values of < 0. 1 g/m2 for all elements studied. The PCT results were tolerant to changes of ∼ 20% of the inventories of the additives, and to variations in redox conditions.

Technetium separated out during decontamination of liquid Hanford wastes can be incorporated as metal in hot-pressed Synroc prepared under reducing conditions, and its leach resistance is good (∼ 10∼3 g/m2/day at 70°C), and can be improved by alloying with iron group metals. With a choice of “neutral” (P(O2) ∼ 10−4 atm., near the Ni/NiO buffer) hot-pressing conditions, Tc can also be incorporated as Tc4+, substituting for Ti4+ in the ceramic phases, and in this form, it should be highly leach resistant also.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 506: Symposium – Scientific Basis for Nuclear Waste Management XXI , 1997 , 289
Copyright
Copyright © Materials Research Society 1998

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References

REFERENCES

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