Thermal and mechanical properties of uranium nitride prepared by SPS technique

Manufacture of fully dense uranium nitride pellets using hydride derived powders with spark plasma sintering

“…While this method is attractive in that it uses more stable oxides as starting material, it leads to relatively large particles, which must be milled in order to achieve high density [3]. In contrast, the method here applied, of first hydriding, then nitriding the pure metal yields a fine powder, for which no milling is required.…”

“…The UN powders were loaded under argon into graphite dies with graphite punches, and transported to the apparatus in an argon-filled container. SPS employs a large electrical DC current pulsed through the material combined with pressure to densify the powder, which allows lower sintering temperature, shorter holding time and higher densification than in conventional sintering [3,9]. During the sintering procedure the chamber was evacuated to a vacuum of around 2 Pa, and two rams provided an uniaxial pressure of 50 MPa.…”

“…A number of independent measurements for the thermal conductivity of UN have been carried out. When correcting for as-manufactured porosity, a variation in the inferred conductivity for fully dense UN of up to 25% results [1][2][3]. These discrepancies cannot clearly be attributed to impurities nor stoichiometry [1].…”

First-principles design of next-generation nuclear fuels

“…Nitrides such as (U,Pu,MA)N and (Pu,MA,Zr)N, where MA is a minor actinide, are now being investigated using DFT as promising advanced nuclear fuel because of their high thermal conductivity and high melting point. 49 In a recent DFT study, point defects in uranium mononitride were investigated, calculating the defect formation energy as well as defect-induced electronic density redistribution. 50 , 51 Uranium monocarbide and ternary alloys, including U-Pu-C, are now considered as possible candidates for next-generation reactor fuels because of the combination of a high melting temperature and high actinide density, 20 , 21 and fi rst-principles calculations have been performed to investigate the thermodynamic properties and phase diagram of these alloys.…”

Densification of zirconium nitride by spark plasma sintering and high voltage electric discharge consolidation: A comparative analysis

“…In particular, mechanical strength of ZrN retained at high temperatures and chemical inertness, with the exception of a limited tendency to oxidize [1,2], render it a suitable material for a variety of applications, such as coatings for thermal barrier layers and tooling setups for material processing. Another application is as a model material for the highly radioactive materials used in nuclear reactors: for fuel pellets (UN) [3,4], as an inert matrix for actinide fuels [5][6][7] or as an additive for PuN pellets, with which it can form a solid solution [8,9]. However, it is difficult to obtain ZrN fully dense bodies due to ZrN high melting temperature (2980˚C), low self-diffusion coefficient (~0.026 m 2 /s at 2400~2600˚C), strong covalent bonding [10], and the existence of an oxide layer (ZrO 2 ) on the surface of the starting powders.…”