Simulation and validation of the thermalhydraulic behavior of the QUENCH-04 experiment using TLANESY and ASYST/SCDAPSIM 3.5 codes

TLANESY (ThermaLhydrAulic and heat traNsfEr SYstem) is a computational tool under development for simulating thermalhydraulic processes. It employs a discretization approach based on volume elements to perform energy balance calculations. The code solves a four-equation homogeneous two-phase flow model, incorporating Bernoulli's equation, heat transport, and continuity equations for liquid and vapor phases. Additionally, it accounts for heat transfer in solid components using a two-dimensional transient model that considers conduction, convection, and radiation. Validation of TLANESY was conducted through comparisons with experimental data from the QUENCH-04 experiment, which replicates severe accident conditions in a pressurized water reactor (PWR) fuel bundle. Results were further benchmarked against ASYST/SCDAPSIM 3.5, a well-established thermalhydraulic code. Simulations examined key parameters such as rod temperature profiles, hydrogen generation, and oxide layer thickness. While both codes demonstrated acceptable agreement with experimental results, discrepancies in temperature estimation and oxidation modeling were observed, attributed to differences in nodalization, power distribution methods, and oxidation correlations. Overall, TLANESY provides a promising alternative for thermalhydraulic analysis in nuclear safety applications. The code’s ability to accurately predict hydrogen generation suggests its potential for severe accident simulations. Further refinements, particularly in power distribution modeling and feedback mechanisms, could enhance its predictive capabilities.