Background: In the second generation pressurized water reactor

the Control Rod Drive Mechanism (CRDM) is mainly cooled by the blast blower

which consumes more energy and is of lower security. Based on the layout of the CRDM group in the Daya Bay nuclear power plant

the EMC-B type of CRDM is taken as research object. Purpose: The temperature distribution of the CRDM group was simulated to verify the feasiblity of natural circluation cooling of air. Methods: Several Computational Fluid Dynamics (CFD) based programs were employed for this research. Firstly

Pro/ENGINEER was applied to establish the 3D model of the CRDM group; then the geometrical model was meshed with ICEM; finally

the flow field and temperature distribution were solved by using FLUENT. Results: The temperature field of the CRDM can be divided into three regions

and the temperature of the middle CRDM was highest

while the temperature of the region between the middle and outside regions was lowest due to the relative weak convection. The highest coil temperature is 198 °C

below the limit value of 200°C. Conclusion: The CRDM and the coils may be cooled effectively by natural convection of air under given conditions.Cited