The source term calculation capability is implemented in the high-fidelity neutronics code. With this high-fidelity tool, the accuracy of the two-step source term calculation method is analyzed in this work, including decay heat, the activation photon source term, and the neutron source term. The accuracy of NECP-X for the source term calculation is demonstrated through the comparison with SCALE6.1 and STREAM for a set of cases, and the results show good consistency between different codes. The analysis of the two-step source term calculation method is conducted by the control-variable method, and the approximations of generating cross-sections with the 2D lattice calculations and the homogenization process are analyzed for a full-core case. The numerical results show that approximations may result in some difference for the decay heat and the photon source results for the small core, and the difference is investigated with the high-fidelity source term calculation capability.

源项计算功能是在高保真中子学代码中实现的。使用此高保真工具，本文分析了两步源项计算方法的准确性，包括衰减热，活化光子源项和中子源项。通过与SCALE6.1和STREAM在一组情况下的比较，证明了NECP-X在源项计算中的准确性，结果表明不同代码之间的一致性很好。通过控制变量法对两步源项计算方法进行了分析，并针对全核情况分析了二维晶格计算和均质化过程生成横截面的近似值。