The Airflow Analysis for CAP1400 Control Rod Drive Mechanisms Cooling System

The CAP1400 nuclear power plant (NPP) reactor integrated head package (IHP) refers to the assembly of all of the equipment and structures that are either mounted to the reactor closure head or provide services to the reactor head assembly. One of the main functions of the IHP in the reactor is to provide cooling for the control rod drive mechanism (CRDM) magnetic coils. The IHP cooling system is realized by axial fans connected to the vent tubes of the CRDM cooling shroud. Under normal operating conditions, two of four fans are required to be in operation. The IHP cooling system shall meet the requirements of “keeping the coil temperature within the magnetic coil component below 200°C”. This requirement is achieved by ensuring that the average flow velocity around the CRDM coil assembly is above 15 m/s and that the minimum flow velocity at any location on the outer surface of the coil assembly is not less than 9 m/s. The main purpose of this paper is to study the flow characteristics of the IHP cooling system under various operating conditions. The CFD method is used to obtain the flow field and temperature field in the IHP and to support the rationality of IHP design.