Material property correlations for uranium mononitride: III. Transport properties

Abstract

The experimental data for the tracer diffusion coefficients of nitrogen ( D N in UN ) and uranium ( D N 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 ( P N , in atm), grain size ( g, in μm), and porosity ( P, as a volume fraction) were developed and are given as: D N in UN(rmcm 2/s) = 2.252 × 10 −5P N 0.4134g −0737+2.179×10 −4T exp{ −19214.7 T } , D N in UN(cm 2/s) = 2.252 × 10 −11P N 0.6414 exp{ −7989.3 T } , ρ(μΩ cm) = 71.49 e 2.14P (T) 0.125 , k( W/ mK) = 1.864 e −2.14 P ( T) 0.361. The nitrogen diffusion coefficient correlation was constructed from experimental data in the range of 0.001 ≤ P N ≤ 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 ≤ P N ≤ 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%.