Application of the UMACS process to highly dense U1−xAmxO2±δ MABB fuel fabrication for the DIAMINO irradiation

Melting behaviour of americium-doped uranium dioxide

“…The chemical compositions are presented in table 1 20 mol.%-Am samples were synthesized at Joint Research CentreInstitute for Transuranium Elements (JRC-ITU) using a process based on combination of (sol + gel) and infiltration methods to produce non-contaminant beads used as precursors for sintering [5,28]. The 15 mol.%-Am samples were prepared at Commissariat à ĺEnergie Atomique et aux énergies alternatives (CEA) from UO 2+d and AmO 2Àe starting powders (similar to those described in [7,8]) following the UMACS process based on two successive thermal treatments separated by a grinding step [7]. The sample characteristics are summarized in table 2.…”

“…The radiotoxicity and heat load of ultimate nuclear waste would thus be decreased as well as the ecological footprint of deep geological repositories [2,3]. In this context, several studies have been dedicated to U 1Àx Am x O 2±d compounds, not only to investigate synthesis methods [4][5][6][7][8][9][10][11] and assess their behaviour under irradiation in reactors [4,7,12,13], but also to determine their structural and thermophysical properties, the latter remaining scarcely known [14][15][16][17][18][19][20]. Among them, no data regarding the U 1Àx Am x O 2±d melting behaviour has been reported, despite the importance of such information with respect to safety margins during irradiation, notably in accidental conditions.…”

Comparative XRPD and XAS study of the impact of the synthesis process on the electronic and structural environments of uranium–americium mixed oxides

“…nature of the precursor, milling step, etc. [4][5][6][7][8][9], the sintering steps are often performed in similar reducing conditions at high temperature (ca. 41600°C).…”

“…Despite this similarity of the final heat treatments, different values of O/M ratio have been reported for samples synthesized by solidliquid or solid-state chemistry. In the case of the U 1 À x Am x O 2 7 δ (x ¼0.10, 0.15 and 0.20) compounds fabricated by solid-state synthesis, it was shown that Am is strictly trivalent while U cations exhibit a mixed U þ IV/ þ V valence, whereby the Am þ III and U þ V contents were similar leading to overall O/M values close to 2.00 [6]. In contrast, the samples synthesized by liquid state chemistry (x ¼0.10 and 0.20), exhibited a mixed Am þ III/ þ IV valence and a U þ IV valence [11].…”

α Self-irradiation Effects on Structural Properties of (U,Am)O2±δMaterials

“…It consists in the irradiation Ambearing blankets (AmBB, i.e., U 1-x Am x O 2±δ with x values close to 10-15 at.%) in the periphery of a fast neutron reactor core. In this context, studies are being performed to assess the feasibility and safety of AmBB transmutation, notably focusing on innovative fabrication processes [1][2][3] Am being a strong α emitter (activity of 130 MBq), U 1-x Am x O 2±δ behavior under α self-irradiation is also monitored [6][7][8].…”