Thermal conductivity measurement of uranium–plutonium mixed oxide doped with Nd/Sm as simulated fission products

Abstract

The thermal conductivities of near-stoichiometric (U,Pu,Am)O2 doped with Nd and/or Sm, which are major fission products (FPs) generated during irradiation of uranium–plutonium mixed oxides (MOX) fuels, as simulated fission products are evaluated from 1073 to 1673 K. The thermal conductivities are calculated from the thermal diffusivities that are measured using the laser flash method. To evaluate the thermal conductivity from a homogeneity viewpoint of Nd/Sm cations in MOX, the specimens with different homogeneities are prepared using ball-mill and fusion methods. A homogeneous Nd/Sm distribution decreases the thermal conductivity of MOX with increasing Nd/Sm content, whereas heterogeneous Nd/Sm has no influence. The effect of Nd/Sm on the thermal conductivity is studied using the phonon transport model λ=(A+BT)−1. The dependences of the coefficients A and B on the Nd/Sm content (CNd and CSm, respectively) are evaluated as: A(mK/W)=1.70×10−2+0.93CNd+1.20CSm, B(m/W)=2.39×10−4.