Effects of self-radiation damage in Cm-doped Gd2Ti2O7 and CaZrTi2O7

Crystalline Ceramics: Waste Forms for the Disposal of Weapons Plutonium

“…This is similar to the value obtained by Foltyn et al E471 for synthetic CaPuTi207 at nearly the same a-decay event dose of 1026 a-decay events/m3 after 1,200 days. Although the measured energy release for the natural zirconolites and Pudoped zirconolites of equivalent dose are nearly identical, both of these values are distinctly lower than the value (84 J/g) measured for Pu-doped zirconolite that had experienced a smaller dose (approximately a-decay events/m3) [47] or for Cmdoped zirconolite (126 J/g) and (GdYCm)2Ti207 at doses of 2.0 X a-decay events/m3 [26,48]. Foltyn et al [47] have suggested that the decrease in released energy w i t h increasing dose is due to a continuing damage process than results in a reordering of atoms in the metamict state.…”

“…A full summary of work on pymchlore and zirconolite can be found in references [2,4,22]. The effect of a-decay on the pyrochlore phase Gd2Ti207 containing 244Cm and 240Pu has been extensively investigated by x-ray diffraction analysis and transmission electron microscopy [25,26]. At a dose of 3.1 x 10l8 a-decay events/g, the material became fully amorphous with no evidence of any residual crystallinity.…”

“…244Cm-doped zirconolite has been synthesized and self-damage studies of zirconolite have also been carried out by substituting 244Cm, an a-active isotope with a half-life of 18.1 y, and 240Pu for Zr [26]. Changes in swelling, microstructure, hardness, fracture toughness, leachability, and recrystallization behavior were assessed.…”

“…The dissolution (leaching) characteristics of the Cm-doped zirconolite were determined [26] by testing fully-damaged (amorphized) specimens and a second set of specimens that had been fully recrystallized to the original structure by a 12 h anneal at 1,lOO"C. Testing was performed in distilled, deionized water at 90°C for 14 d. The measured 240Pu release rate was 0.002 g/m2d and increased by a factor of 15 due to amorphization. The high final pH is believed to limit the solubility of the Cm.…”

Interstitial Incorporation of Plutonium into a Low-Dimensional Potassium Borate

“…During the last two decades, significant efforts have been made to better understand the incorporation of early actinide elements (namely Th, U, Np, and Pu) into a variety of mineral phases, such as calcite (7)(8)(9)(10)(11)(12)(13)(14)(15), zircon (4,(16)(17), monazite (4,(17)(18), zirconolite (4,(18)(19)(20)(21)(22), perovskite (4,22), garnet (4), pyrochlore (4,(23)(24)(25), brucite (26), and several other systems (27)(28)(29)(30). Particularly for transuranium elements (Np and Pu), it was determined that these can also be incorporated into a series of uranium-or thorium-based minerals such as brannerite (4), ianthinite (31), schoephite, becquerelite, compreignacite, and boltwoodite (32) or even synthetic phases such as Th 2-x/2 An IV x/2 (PO 4 ) 2 (HPO 4 )·H 2 O (An = U, Np, Pu) (33), ThSiO 4 (34), and Ba 3 (UO 2 ) 2 (HPO 4 ) 2 (PO 4 ) 2 (35).…”