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The Relative Merits of Oxides of Hafnium, Cerium and Thorium as Surrogates for Plutonium Oxide in Calcium Phosphate Ceramics

Published online by Cambridge University Press:  15 February 2011

B. L. Metcalfe
Affiliation:
MSRD, AWE Aldermaston, Reading, RG7 4PR, UK
S. K. Fong
Affiliation:
MSRD, AWE Aldermaston, Reading, RG7 4PR, UK
L. A. Gerrard
Affiliation:
MSRD, AWE Aldermaston, Reading, RG7 4PR, UK
I. W. Donald
Affiliation:
MSRD, AWE Aldermaston, Reading, RG7 4PR, UK
E. S. Welch
Affiliation:
ISL, Dept. of Engineering Materials, University of Sheffield, S1 3JD, UK
M. C. Stennett
Affiliation:
ISL, Dept. of Engineering Materials, University of Sheffield, S1 3JD, UK
N. C. Hyatt
Affiliation:
ISL, Dept. of Engineering Materials, University of Sheffield, S1 3JD, UK
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Abstract

The choice of surrogate for plutonium oxide for use during the initial stages of research into the immobilization of intermediate level pyrochemical wastes containing plutonium andamericium oxides in a calcium phosphate host has been investigated by powder X-ray diffraction and X-ray absorption spectroscopy. Two non-radioactive surrogates, hafnium oxide and cerium oxide, together with radioactive thorium oxide were compared. Similarities in behaviour were observed for all three surrogates when calcined at the lowest temperature, 750°C but differences became more pronounced as the calcination temperature was increased to 950°C. Although some reaction occurred between all the surrogates and the host to form a substituted whitlockite phase, increasing the temperature led to a significant increase in the cerium reaction and the formation of an additional phase, monazite. Additionally it was observed that the cerium became increasingly trivalent at higher temperatures.

Type
Research Article
Copyright
Copyright © Materials Research Society 2009

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