Abstract:
During the loss of coolant accident (LOCA) in any Pressurized Water Reactor (PWR) of
nuclear power plant, high temperature steam may release into the containment from
nuclear reactor core and pressurizes the containment. Containment Spray System is used
to condense the steam and depressurization of containment occurs due to condensation
of steam. To analyze the effects of spray on dynamic behavior of steam during these
conditions, Spray simulations have been performed by using ANSYS CFX. Three
dimensional model of containment vessel was created in the ANSYS Design Modeler
for CFX. The flow has been taken as two-phase flow with steam and water droplets in
the containment. The modeling way of the continuous fluid (gas) is established on
Eulerian statement and the dispersed fluid (water droplets) is established on Lagrangian
statement. The flow of two fluids is fully coupled. In the single phase of gas field, water
droplets operate as a source of mass, momentum and thermal energy. In addition, the
temperature of wall is taken high to avoid steam condensation on walls and the droplets
are considered liquid film when they strike on walls. The heat transfer also occurs
between liquid wall film and gas. This research studied the effect of water spray
activation on the average atmosphere temperature of containment and the mixing of gas.
The distribution of droplet diameter has also been analyzed. It studied how the injection
temperature and mass flow rate of water affect the cooling rate, condensation rate and
the equilibrium temperatures of steam. These simulations have same initial and
boundary conditions for spray except mass flow rate which have been varied from 30g/s
to 70g/s and injection temperatures at the injection center which have been varied from
25°C to 60°C.
