We present numerical simulations of the temperature-related laser performance of the amplifiers for the Lasers Ultra-Courts et Intenses et Applications (LUCIA) laser, a 100 J, 10 Hz, 10 ns diode-pumping solid-state-laser facility, which uses Yb3+:YAG as the gain medium. The simulations include energy storage and extraction efficiency, cooling of the gain medium, and wavefront distortion. The results show that, with a pumping intensity of 20 kW/cm2 at 10 Hz and a doping concentration of 10 at. % at a thickness of Yb3+:YAG of 1.6 mm, the output laser fluence and optical-to-optical efficiency are expected to be 10 J/cm2 and 25.8%, respectively, at a heat exchange coefficient of 3000 W/m2/K of water. Also, the matching thickness of undoped YAG is optimized to prevent bending deformation of the gain medium, which could be approximately 5 mm.