Due to the constant need to improve safety system in nuclear power plants, it is necessary to analyze the thermal, mechanical and physicochemical behavior of the fuel rod cladding during forced colling of the reactor. The QUENCH facility offers a good imitation of a real reactor using the same rod cladding material, zirconium. The complexity of this kind of research facilities is a major obstacle in predicting the behavior of temperatures, oxidation and hydrogen production rate. The RELAP5/SCDAPSIM program,which is a software tool for simulation and analysis of hydraulic and thermal processes based on the input parameters of an already performed experiment, can help us there. In this case, an experiment made for the purpose of research was simulated. Except this kind of simulation, the mentioned program also makes it possible to simulate the process of an actual nuclear reactor. The RELAP5/SCDAPSIM program facilitates the entire process of analyzing and predicting the operation of nuclear facilities, thereby enabling the development of technology in order to prevent serious nuclear accidents. Its use significantly increases the accuracy of safety system improvement studies and contributes to the formation of a more complete picture of core behavior under normal and severe accident conditions.