Thermal Hydraulics Analysis Under Natural Circulation Condition of the 4S

Thermal hydraulics analysis under natural circulation condition of the 4S was performed with a 3 D total integrated model which contains the primary equipment in the reactor vessel (R/V), the intermediate equipment, the reactor auxiliary cooling system (RVACS), and the intermediate reactor auxiliary cooling system (IRACS). In the long term after the reactor trip, the primary coolant, the intermediate coolant, the RVACS air flow, and the IRACS air flow were circulated by natural circulation force. As the result, it has been confirmed that the core temperature was passively decreased gradually in a safe manner. The natural circulation force in the R/V is affected by temperature distribution in the R/V. In order to comprehend the effect of radial heat transfer in the R/V, it was shown the parameter analysis changed the radial heat transfer rate. As the result, the natural circulation flow decreases, as the radial heat transfer increase. On the other hand the core mean temperature decreases because the generated heat in the core was released to the core outer region. Regarding to the inner core temperature, it has tendency to increase.Copyright © 2010 by ASME