Feasibility analysis of the modified ATHLET code for supercritical water cooled systems

Since the existing thermal-hydraulic computer codes for light water reactors are not applicable to supercritical water cooled reactors (SCWRs) owing to the limitation of physical models and numerical treatments, the development of a reliable thermal-hydraulic computer code is very important to design analysis and safety assessment of SCWRs. Based on earlier modification of ATHLET for SCWR, a general interface is implemented to the code, which serves as the platform for information exchange between ATHLET and the external independent physical modules. A heat transfer package containing five correlations for supercritical water is connected to the ATHLET code through the interface. The correlations are assessed with experimental data. To verify the modified ATHLET code, the Edwards–O’Brian blow-down test is simulated. As first validation at supercritical pressures, a simplified supercritical water cooled loop is modeled and its stability behavior is analyzed. Results are compared with that of the theoretical model and SASC code in the reference and show good agreement. To evaluate its feasibility, the modified ATHLET code is applied to a supercritical water cooled in-pile fuel qualification test loop. Loss of coolant accidents (LOCAs) due to break of coolant supply lines are calculated for the loop. Sensitivity analysis of some safety system parameters is performed to get further knowledge about their influence on the function of the safety system. All the results achieved indicate that the modified ATHLET code has good feasibility in simulation of supercritical water cooled systems.

► Modification of system code ATHLET for supercritical water application.
► Development and assessment of a heat transfer package for supercritical water.
► Validation of the modified code at supercritical pressures with the theoretical point-hydraulics model and the SASC code.
► Application of the modified code to LOCA analysis of a supercritical water cooled in-pile fuel qualification test loop.