Reactor validation is the formal academic process of assessing the accuracy and reliability of computational models, simulations, and theoretical frameworks used to represent the physical behavior and performance of nuclear reactors. This involves systematically comparing model predictions against empirical data obtained from experiments, operational observations, or established benchmarks. It investigates the fidelity and predictive capability of these models across various operating conditions and transient events, aiming to quantify uncertainties and identify limitations. Key characteristics include rigorous data-model comparison, statistical analysis of discrepancies, and iterative model refinement. Its significance lies in establishing the necessary confidence for reactor design, safety analysis, operational optimization, and regulatory approval within nuclear science and engineering.