基于 NECP-MCX 的组件均匀化计算及其在HPR1000 中的应用

The assembly code based on the Monte Carlo method can handle problems with complicated geometry and avoid the resonance self-shielding calculation in the deterministic assembly code. However, the Monte Carlo assembly code has certain difficulties when generating diffusion coefficient and assembly discontinuous factors. Therefore, the capability for the generation of assembly-homogenized few-group constants is developed based on the continuous-energy Monte Carlo particle transport code NECP-MCX. The cumulative migration area method, which treats the anisotropy of neutron explicitly, is adopted to generate the diffusion coefficient; the fundamental mode approximation is used to consider the effect of neutron leakage on the neutron spectrum; the approach named as the mesh-surface tally is proposed to calculate the corrected assembly discontinuous factors. The mesh-surface tally approach is verified through VERA 2D assembly problems and the NECP-MCX is adopted to simulate the physics start-up test of the home-developed HPR1000 reactor. The results show that the biases of critical boron concentrations, the isothermal temperature coefficients, and the control rod bank worth values satisfy the limited value when compared to the design report. The NECP-MCX has the ability to generate reliable assembly-homogenized few-group constants of which accuracy satisfies the requirement of engineering calculation, laying a solid foundation for the further application of NECP-MCX in next-generation reactors.