Research of Preventive Measures for Heterogeneous Boron Dilution Accident in Daya Bay NPP

The nuclear power plants are possible to suffer the core uncovering damage due to the heterogeneous boron dilution which is out of the design basis. This paper analyzes the mechanism of criticality accident caused by the heterogeneous boron dilution, and study the measures to prevent the erroneous dilution. The implementation of the improvement measures greatly improves the safety level of the Daya Bay NPP, especially effectively improves the safety level under the reactor shutdown conditions.