Thermal conductivity of gadolinium added uranium mononitride fuel pellets sintered by spark plasma sintering

Abstract

Thermal conductivity of spark plasma sintered UN/Gd2O3 and UN/GdN composite pellets with various compositions of Gd2O3 (5.0 to 15.0 wt%) and GdN (3.5 to 38.4 wt%) was measured from 25 °C to 1000 °C using laser flash analyzer (LFA). Overall thermal conductivity of both composite pellets decreases with increasing Gd compositions for the entire temperature range measured. The UN/GdN pellets sintered at high temperature (2000 °C) contained solid-solution (U1-x,Gdx)N phase and exhibited 20–65 % higher thermal conductivity than the UN/Gd2O3 pellets. We also confirmed a two-phase structure in low temperature (1800 °C) sintered UN/GdN pellets, which exhibited 14–25 % higher thermal conductivity than solid-solution UN/GdN pellets. This result may indicate that relatively higher thermal conductivity of UN/GdN composite as burnable absorber fuel could be further enhanced with an optimized microstructure.