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

  • E.R. Vance (a1), K.P. Hart (a1), M.L. Carter (a1), M.J. Hambley (a1), R.A. Day (a1) and B.D. Begg (a1)...

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.

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References

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1 Vance, E. R., Day, R. A., Carter, M. L. and Jostsons, A. (1996), in Scientific Basis for Nuclear Waste Management XIX, Eds. Murphy, W. M. and Knecht, D. A., Materials Research Society, Pittsburgh, PA, p.289.
2 Vance, E. R., Hart, K. P., Day, R. A., Carter, M. L., Hambley, M., Blackford, M. G. and Begg, B. D. (1997), in Scientific Basis for Nuclear Waste Management XX, Eds. Gray, W. J. and Triay, I. R., Materials Research Society, Pittsburgh, PA, in press.
3 Vance, E. R., Day, R. A., Zhang, Z., Begg, B. D., Ball, C. J. and Blackford, M. G. 9(1996), J. Solid State Chem., 124, 77.
4 Begg, B. D., Vance, E. R., Hanna, J. V. and Hunter, B. A., J. Mater. Res., submitted.
5 Sobolev, I.A., Lifanov, F.A., Dimitriev, S.A., Stefanovsky, S.V. and Kobolev, A.P., in Spectrum '94. Nuclear and Hazardous Waste Management International Topical Meeting (Atlanta, GA, USA, 1994) p.2250
6 Khalil, M. Y. (1984), Ph. D. Thesis, Pennsylvania State University, unpublished.

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

  • E.R. Vance (a1), K.P. Hart (a1), M.L. Carter (a1), M.J. Hambley (a1), R.A. Day (a1) and B.D. Begg (a1)...

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