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 Boris E. Burakov, Maria A. Yagovkina, Maria V. Zamoryanskaya, Alexander A. Kitsay, Vladimir M. Garbuzov, Evgeniy B. Anderson and Alexey S. Pankov Laboratory of Applied Mineralogy and Radiogeochemistry, the V.G. Khlopin Radium Institute, 28, 2-nd Murinskiy ave., St. Petersburg, 194021, Russia, e-mail: [email protected]  $%675$&7 To investigate the resistance of cubic zirconia to accelerated radiation damage, which simulates effects of long term storage, 238Pu-doped polycrystalline samples of cubic zirconia, (Zr,Gd,Pu)O2, were obtained and studied using X-ray diffraction analysis (XRD), electron probe microanalysis (EPMA), optical and scanning electron microscopy (SEM), and modified MCC-1 static leach test.The ceramic material was characterized by the following chemical composition (from EPMA in wt.% element): Zr = 50.2, Gd = 15.4, Pu = 12.2. This corresponds to the estimated formula, Zr0.79Gd0.14Pu0.07O1.99. The content of 238Pu estimated was approximately 9.9 wt.%. The XRD measurements were carried out after the following cumulative doses (in alpha decay/m3 x 1023): 3, 27, 62, 110, 134, 188, 234, and 277. Even after extremely high selfirradiation, cubic zirconia retained its crystalline structure. All XRD analyses showed no phases other than a cubic fluorite-type structure.The following results of normalized Pu mass loss (1/, in g/m2, without correction for ceramic porosity) were obtained from static leach tests (in deionized water at 90°C for 28 days) for 4 cumulative doses (in alpha decay/m3 x 1023): 1/(Pu) 0.04 0.35 0.37 0.24

Cumulative dose 11 56 81 127

 The results obtained confirm the high resistance of cubic zirconia to self-irradiation. This allows us to consider zirconia-based ceramic as the universal material that is suitable for actinide transmutation and geological disposal. ,1752'8&7,21  Crystalline ceramics based on cubic zirconia have been proposed as a durable host matrix for the immobilization of weapons grade Pu and other actinides [1-14] through: 1) transmutation (burning) followed by geological disposal of irradiated materials or 2) just direct geological disposal of actinide matrices. Also, critical-mass-free ceramics based on gadolinia-stabilized cubic zirconia or hafnia-zirconia solid solutions might be used for safe temporary storage of excess weapons Pu [22]. Zirconia-plutonia solid solution, (Zr,Pu)O2, with Pu4+ substituting for Zr4+ in the zirconia structure, is a prospective ceramic fuel [1], which is competitive with mixed oxide fuel MOX, (UO2+PuO2). It was reported that LWR could provide transmutation of more than 98 % of 239Pu and 85 % of total Pu in the form of ceramic fuel [5]. It was proposed that spent ceramic fuel, unlike spent MOX fuel, could be finally disposed directly into geological formations without reprocessing [8]. A study of cubic zirconia irradiated by Xe2+ and I+ ion

1

implantation confirmed the high resistance of its crystalline structure to radiation damage [7,10,12,13,15]. Solid-state