MATERIAL PROPERTY CORRELATIONS FOR URANIUM MONONITRIDE .3. TRANSPORT-PROPERTIES

The experimental data for the tracer diffusion coefficients of nitrogen (DN in UN) and uranium (DN in UN) in uranium mononitride (UN), electrical resistivity (ρ), and thermal conductivity (k) of UN have been collected and reviewed. Empirical correlations for these properties as functions of temperature (T, in K), nitrogen partial pressure (PN, in atm), grain size (g, in μm), and porosity (P, as a volume fraction) were developed and are given as: DN in UN(rmcm2/s) = 2.252 × 10-5PN0.4134g-0737+2.179×10 exp{ -19214.7 T}, DN in UN(cm2/s) = 2.252 × 10-11PN0.6414 exp{ -7989.3 T}, ρ(μΩ cm) = 71.49 e2.14P (T)0.125, k(W/mK) = 1.864 e-2.14P(T)0.361. The nitrogen diffusion coefficient correlation was constructed from experimental data in the range of 0.001 ≤ PN ≤ 2.0 atm, 25 ≤ g ≤ 5000 μm, and 1503 ≤ T ≤ 2273 K; similarly, the uranium diffusion coefficient correlation incorporated an experimental database in the range of 2.6×10-5 ≤ PN ≤ 0.66 atm and 1873 ≤ T ≤ 2133 K. The electrical resistivity and thermal conductivity correlations are applicable for temperatures of 298 ≤ T ≤ 1600 K and 298 ≤T ≤ 1923 K, respectively, and both correlations were developed from data representing porosities of 0-20%. © 1990.