The numerical results from a neutron source, as the important input parameter for the transport calculation, directly affect the accuracy of shielding calculations for reactor. The apparent differences between core sources are related to their geometric model, burnup, and power distribution.

This study aims to improve the calculation accuracy of the core neutron source for nuclear reactor shielding.

Firstly, the geometric weight of each component in the core was generated by analyzing the characteristics of the radial source distribution on the basis of neutron importance, and the fine source mesh calculation was conducted for the peripheral components with high geometric weight and the region with a large power gradient. Then, a layered approach for different axial height positions was employed to reduce the influence of the axial power peak factor to achieve stable transport calculation results, and the source and geometry meshes were mapped according to the volume weight method to ensure the conservation of total source. Finally, the NUREG/CR-6115 core as a benchmark model was used for numerical verification.

Numerical verification results indicate that, compared with the average source calculation, the multi-weight source mesh mapping algorithm reduces the root mean square of the relative error in the fast neutron fluence by 18.46% between the transport calculation results and the reference value.

The multi-weight source mesh mapping algorithm can be employed to obtain an accurate source distribution, improve the accuracy of the shielding calculation, and satisfy the requirements of engineering applications.