A thermal battery is composed of several pellet types including anode, cathode, heat, and separator. The separator pellet provides an electrolyte bridge between the anode and cathode and, like the other pellets in the battery, becomes molten when the battery is activated. Since the pellet changes state, it is important to understand its deformation and particularly the LiCl-KCl content of the pellet as temperatures increase. Having sufficient structural support within the pellet is crucial to maintaining contact between adjacent pellets during storage and operations. This work presents the development of the numerical framework to characterize the deformation of MgO. This work expands the state-of-the-art by developing a numerical capability to estimate performance over a wide range of particle and operating conditions.