Title: Neutronic and Thermal Design of a Spherical Reactor Using Auxiliary Algorithms. Author: Eng. Omran Saleh. Supervisor: Prof. Dr. Ali Oweis. Institution: University of Aleppo - Faculty of Mechanical Engineering - Nuclear Engineering Department. Abstract: This research presents an integrated computational approach for the neutronic and thermal design of a spherical nuclear reactor. The study emphasizes the critical role of neutronic parameters in ensuring reactor safety and operational efficiency, including the determination of minimum critical mass, reactivity excess, and neutron flux distribution across various energy spectra. A key contribution of this work is the implementation of auxiliary algorithms to solve complex reactor physics equations. The methodology utilizes the One-Group Diffusion Theory and the Four-Factor Formula (k_{\infty} = \epsilon \cdot p \cdot f \cdot \eta) to evaluate the criticality of the system. The research provides a detailed mathematical derivation for the "Geometric Buckling" (B_g^2) of the spherical core and calculates the "Material Buckling" (B_m^2) to achieve the critical state (k_{eff} = 1). Furthermore, the study conducts a parametric analysis of the moderation process, specifically calculating the slowing-down power and the moderation ratio for light water (H_2O). Key variables such as the microscopic and macroscopic cross-sections (\sigma, \Sigma), the resonance escape probability (p), and the thermal utilization factor (f) are meticulously computed. The integration of algorithmic assistance allows for high-precision calculations of the reactor's physical dimensions and fuel enrichment requirements, providing a robust framework for optimizing spherical reactor designs in modern nuclear engineering.