Development of a Phosphate Ceramic as a Host for Halide-Contaminated Plutonium Pyrochemical Reprocessing Wastes

Conference · Sun Jul 01 00:00:00 EDT 2007

OSTI ID:21062397

Metcalfe, Brian; Fong, Shirley; Gerrard, Lee; Donald, Ian ^[1]; Strachan, Denis; Scheele, Randall ^[2]

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1. MSRD, AWE plc, AWE Aldermaston, Reading, RG7 4PR (United Kingdom)
2. PNNL, Richland, WA, 99352 (United States)

The presence of halide anions in four types of wastes arising from the pyrochemical reprocessing of plutonium required an immobilization process to be developed in which not only the actinide cations but also the halide anions were immobilized in a durable, leach resistant form. AWE has developed such a process using Ca{sub 3}(PO{sub 4}){sub 2} as the host material. Successful trials of the process using actinide-doped Type I waste (essentially a chloride-based waste) were carried out at PNNL where the immobilization of the waste in a form resistant to aqueous leaching was confirmed. Normalized mass losses determined using a modified MCC-1 test at 40 deg. C/28 days were 12 x 10{sup -6} g.m{sup -2} and 2.7 x 10{sup -3} g.m{sup -2} for Pu and Cl, respectively. Accelerated radiation-induced damage effects are being determined with specimens containing {sup 238}Pu. No changes in the crystalline lattice have been detected with XRD after the {sup 239}Pu equivalent of 400 years ageing. Confirmation of the process for Type II waste (an oxyhydroxide-based waste) is currently underway at PNNL. Differences in the ionic state of plutonium in the four types of waste have required different surrogates to be used. Samarium chloride was used successfully as a surrogate for both Pu(III) and Am(III) chlorides. Early investigations into the use of HfO{sub 2} as the surrogate for Pu(IV) oxide in Type II waste showed some apparent differences in the phase assemblages of the surrogate and actinide-based products. However XRD examination of the products at higher resolution has demonstrated there is no significant difference and that for this work HfO{sub 2} is a suitable surrogate for PuO{sub 2}. (authors)

• Research Organization: Materials Research Society, 506 Keystone Drive, Warrendale, PA, 15086-7573 (United States)
• OSTI ID: 21062397
• Resource Relation: Conference: Symposium on Scientific Basis for Nuclear Waste Management, Boston - Massachusetts (United States), 27 Nov - 1 Dec 2006; Other Information: Country of input: France; 6 refs; Related Information: In: Proceedings of the symposium on Scientific Basis for Nuclear Waste Management XXX, by Dunn, Darrell [ed. Southwest Research Inst., San Antonio, Texas (United States)]; Poinssot, Christophe [ed. CEA-Saclay, 91191 Gif-sur-Yvette cedex (France)]; Begg, Bruce [ed. Australian Nuclear Science and Technology Organisation, Lucas Heights, NSW (Australia)], v. 985, 663 pages.
• Country of Publication: United States
• Language: English

Related Subjects

12 MANAGEMENT OF RADIOACTIVE WASTES, AND NON-RADIOACTIVE WASTES FROM NUCLEAR FACILITIES
CALCIUM PHOSPHATES
CERAMICS
DOPED MATERIALS
HAFNIUM OXIDES
HIGH-LEVEL RADIOACTIVE WASTES
LEACHING
PLUTONIUM
PLUTONIUM 238
PLUTONIUM 239
PLUTONIUM OXIDES
PYROCHEMICAL REPROCESSING
SAMARIUM CHLORIDES
X-RAY DIFFRACTION