OECD/NEA ROSA-2 Project, 7; A Preliminary 3D steam flow analysis for CET behavior simulation during LSTF SBLOCA experiment

Irwanto, D.; Satou, Akira ; Takeda, Takeshi ; Nakamura, Hideo  

3D steam flow of superheated steam within simulated fuel bundle of LSTF (Large Scale Test Facility), a PWR system simulator, has been investigated by CFD (Computational Fluid Dynamics) analysis with ANSYS FLUENT code to clarify influences of the steam flow on CET (Core Exit Temperature) response during core uncovery. A portion of LSTF core was modeled and simulation was carried out at a certain time during SBLOCA (Small Break Loss of Coolant Accident). The CET response in terms of 3D steam flow is discussed through such measured and/or calculated parameters as temperature, velocity and flow behavior in the core. From the calculation, temperature varies between 521 to 714K with average temperature was around 0.2 m/s. It is clear that inner structures of the core such as end box and UCP indeed affect the CET due to heat transfer from hot steam to these cool structures. In addition, 3D flow mixing also may contribute to the final CET values.