Application of Discontinuity Factor in the Process of ThreeDimensional Reactor Core Transient Simulation

In order to guarantee the static and transient accuracy and real-time performance in the process of the three-dimensional core transient calculation, the high order nodal expansion method is used for the calculation of the fine mesh structure. The results such as average neutron flux and the interface current are considered as the heterogeneous solution. In the homogenization process, the homogeneous group parameters and interface discontinuity factors and boundary albedos are calculated using the flux volume weight method. In the process of transient calculation, according to the control rod changes and the thermal hydraulics parameters feedback, real-time correction is carried out by updating the homogeneous parameters and discontinuity factors. Finally using coarse mesh finite difference method with discontinuity factor correction, a three dimensional core static and transient calculation is realized and verified based on the typical LMW benchmark. Simulation results prove that the accuracy is equivalent to the high order nodal expansion method at both space and time scope. The efficiency is higher than that of the nodal expansion method directly applied in the transient simulation. It meets the requirement of the development for the nuclear power plant full scope simulator.