Critical heat flux for APR1400 lower head vessel during a severe accident

Corium Ablation Stopper Apparatus (CASA) has a downward-facing hemispherical vessel and geometrically asymmetric thermal insulator of the Advanced Power Reactor 1400 MWe (APR1400) scaled linearly down by 1/10, as well as sixty-one in-core instrumentation (ICI) tubes and four shear keys. The heated vessel plays a pivotal role in CASA depending on the configuration of the oxide pool and metal layer to bring about the focusing effect expected of a molten pool in the lower head during a severe accident. The heated vessel was designed through a trial-and-error method and thermal analysis. Thermal analysis was performed using ANSYS V11.0 to investigate the effect of the internal temperature and heat flux on the integral hemispherical copper vessel. The CASA tests were carried out to obtain the critical heat flux (CHF) with saturated and demineralized water at the atmospheric pressure (0.1 MPa). The CHF in the metal layer through the hemispherical channel was found to be lower than that in the ULPU-2400 configuration V data through the streamlined thermal insulator. The experimental CHF was measured and obtained through the CASA hemispherical heated surface accounting for the three-dimensional random flow effect expected in the APR1400 application.

► Studied boiling on downward-facing hemispherical vessel with asymmetric thermal insulator.
► Scaled the APR1400 lower head linearly down by 1/10 including ICI tubes and shear keys.
► Performed thermal analysis using ANSYS V11.0 to determine the internal temperature and heat flux.
► Performed tests to obtain the CHF with saturated demineralized water at atmospheric pressure.
► Measured CHF accounting for 3D random flow effect expected in the APR1400 application.