EXPERIMENTAL-STUDY ON HEAT REMOVAL CHARACTERISTICS FOR WATER WALL TYPE PASSIVE CONTAINMENT COOLING SYSTEM

To evaluate the heat removal capability of a water wall type cooling s ystem, which is one passive containment cooling system (PCCS), the the rmal hydraulic behavior in the suppression pool (S/P) and the outer po ol (O/P, flat plate water wall) have been investigated experimentally. The following results were obtained. (1) A thermal stratification bou ndary, which separates the pools into the upper high temperature and l ower low temperature regions, was formed just below the vent tube outl et. (2) Convection heat transfer characteristics in the S/P and O/P al ong the primary containment vessel (PCV) wall had no significant diffe rences and were those of natural convection. Correlation of the natura l convection heat transfer up to the Ra number of 2x10(14) was obtaine d. (3) Vertical variations of local condensation heat transfer coeffic ients under a noncondensable gas presence were within +/-10% of the av erage value for the 4.7 m heat transfer length. An experimental correl ation for the average condensation heat transfer coefficients was obta ined as a function of steam and noncondensable gas mass ratio. (4) An analytical model to evaluate the system performance of the water wall type PCCS was verified. (5) A baffle plate concept to mitigate thermal stratification at the vent outlet and to enlarge the high temperature region in the S/P was considered as a means to improve heat release c apability. Thermal hydraulics with a baffle plate were examined, and e ffectiveness of the baffle plate to improve the heat release capabilit y was confirmed.