Fabrication of 239/238 Pu-Zirconolite Ceramic Pellets by Natural Sintering
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)DEULFDWLRQRI 3X=LUFRQROLWH&HUDPLF3HOOHWVE\1DWXUDO6LQWHULQJ T. Advocat1, F. Jorion2, T. Marcillat1, G. Leturcq1, X. Deschanels1, J.M. Boubals1, L. Bojat1, P. Nivet1 and S. Peuget1 Commissariat à l’Énergie Atomique, (1DEN/DIEC/SCDV-SESC, 2DEN/DRCP/SE2A), CEAMarcoule, BP 17171, 30207 Bagnols-sur-Cèze Cedex, France $%675$&7
Zirconolite is a potential inorganic matrix that is currently investigated in France, in the framework of the 1991 radioactive waste management law, with a view to provide durable containment of the trivalent and tetravalent minor actinides like neptunium, curium, americium and small quantities of unrecyclable plutonium separated from other nuclear waste. To confirm the actinide loading capacity of the zirconolite calcium site and to study the physical and chemical stability of this type of ceramic when subjected to alpha self-irradiation, zirconolite ceramic pellets were fabricated with 10 wt% plutonium oxide (isotope 239 or 238). The 55 pellets are dense (> 93.3% of the theoretical density on average) and free of cracks. They are characterized by a grain size of between 10 and 20 micrometers. X-ray diffraction analyses confirmed the presence of the zirconolite 2M crystalline structure. ,1752'8&7,21
The minor actinides such as neptunium, curium, americium are highly radiotoxic. Two options are currently investigated in France under the terms of the 1991 radioactive waste management law to reduce the potential long-term impact of nuclear waste [1–3] The reference option is an enhanced chemical separation step during spent fuel reprocessing, followed by transmutation by neutron bombardment in dedicated nuclear facilities. This option reduces the initial radiotoxic inventory. The second option would be the incorporation of the separated actinides in an inorganic matrix ensuring long-term stability. Zirconolite CaZrTi2O7 is one of the potential containment matrices examined [4–6]. The major objective is to demonstrate the feasibility of specific containment for a blend of minor actinides (which may be mixed with lanthanides and small quantities of impurities) with matrix loading factors of about 10 oxide wt%. The development of zirconolite (Ca1–[– 3+ 4+ \An [An \)Zr(Ti2–[–2\Al[+2\)O7 is specifically intended : 1) to finalize a procedure for fabricating the ceramics under radioactive conditions, 2) to understand the chemistry of the solid material when actinide elements An3+/An4+ are inserted at a calcium site, 3) to understand the physical and chemical stability of the solid up to and beyond the critical amorphization dose 'F ≈ 5 × 1018 α/g, 4) to demonstrate the long-term chemical durability. Three complementary approaches are associated to understand and demonstrate the stability of zirconolite under alpha irradiation: • characterization of zirconolite loaded with short-lived actinides (for example 244Cm or 238Pu [6–8]) capable within a few years of integrating a cumulative number of alpha disintegrations at least equivalent to the critical amorphization dose (between 1018 and 1019
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