Radiation Stability of Spark‐Plasma‐Sintered Lead Vanadate Iodoapatite

Abstract

Spark‐plasma‐sintered lead vanadate iodoapatite Pb9.85(VO4)6I1.7, a promising nuclear waste form for the immobilization of I‐129, was irradiated with energetic ions, electrons, and gamma rays, to investigate its radiation stability. In situ TEM observation of the 1 MeV Kr2+ irradiation shows that lead vanadate iodoapatite generally exhibits higher tolerance against ion irradiation‐induced amorphization than lead vanadate fluorapatite, and the spark plasma sintering can further enhance its radiation stability attributed to the enhanced crystallinity, reduced defect concentration, and denser microstructure. The critical amorphization dose and critical temperature for the SPS‐densified iodoapatite at 700°C are determined to be 0.25 dpa at room temperature and 230°C, respectively. No significant phase transformation or microstructural damage occurred under energetic electron and gamma irradiations. Raman spectra of gamma‐ray‐irradiated iodoapatite indicate improved V–O bond order at 500 kGy dose. Generally, the spark‐plasma‐sintered iodoapatite exhibits excellent radiation stability for nuclear waste form applications. The significantly enhanced radiation stability of the SPS‐densified iodoapatite suggests that SPS holds great promise for fabricating iodoapatite waste form with minimum iodine loss and optimized radiation tolerance for effective management of highly volatile I‐129.

The thermal stability and consolidation of perovskite variant Cs2SnCl6 using spark plasma sintering

“…The key benefits of SPS include the rapid consolidation, the reduction in sintering temperature as compared to conventional methods, and enhanced microstructural control of materials. SPS has been applied to the low‐temperature consolidation of a wide‐range of materials including metal alloys, bioceramics, carbon nanotubes composites, and most notably for this work, halogen‐bearing mineral‐analogue ceramics such as lead vanadate iodoapatite …”

Radiation-induced amorphization of Ce-doped Mg2Y8(SiO4)6O2 silicate apatite

“…5(a). The temperature dependence curve were fit by an empirical exponential function [27,39,40] [42], the cationic site with free-oxygen nearby prefers to accommodate cations with high charge or small radius in order to compensate the underbonded valence [43]. Because the ionic radii of Ce 3+ and Y 3+ at AI sites and AII sites are 1.196 and 1.075, 1.07 and 0.96, respectively, the larger Ce 3+ cations are more likely to occupy A I sites rather than A II sites.…”

“…Radiation stability maybe related with factors like chemical composition [20], different energy loss mechanism[1, 21], structural disorder [22], and grain size [23,24]. Therefore, the radiation effects in different apatite compositions are very interesting and efforts have been made to study the radiation stability of different apatite composition as nuclear waste forms, like fully phosphate fluorapatite [25], mono-silicate fluorapatite [26], synthetic britholite [21] and fully silicate apatite [17,27]. Rare-earth silicates with the apatite structure have been observed as actinide host phases in a devitrified borosilicate HLW glass [28], a multiphase ceramic waste form [29], a glass-ceramic waste form [30], and a cement waste form [19].…”

Synthesis and characterization of iodovanadinite using PdI2, an iodine source for the immobilisation of radioiodine

“…[9][10][11] Whereas the direct disposal of AgI and PdI 2 metal salts has been suggested, 1 their immobilisation within a stable tailored glass and/or ceramic waste form has also been proposed. Iodovanadinite, prototypically Pb 10 (VO 4 ) 6 I 2 , is one potential ceramic matrix for immobilisation of radioiodine, [12][13][14][15][16][17][18][19] due to its chemical durability, [20][21][22] radiation tolerance, 23 and its ability to effectively accommodate the sterically demanding iodide anion within the one dimensional tunnels of the apatite crystal structure. 13,17 Whereas a majority of the reported work on Pb 10 (VO 4 ) 6 I 2 has focused on synthesis of this material, [15][16][17][18][19]23 few studies have considered the use of different iodine sources other than PbI 2 .…”