The RESK processing is a new function in NECP-Atlas. Besides, an accurate slowing-down spectrum calculation method is developed based on the RESK, to consider the impact of neutron upscattering on the multi-group cross sections. The performance of these methods is tested on UO₂ fuel Mosteller Doppler-effect benchmarks. Two different WIMS-D format libraries are generated by NECP-Atlas. In the one library, the group-to-group scattering matrix, multi-group cross sections and RI are calculated using the conventional asymptotic scattering kernel; in another library, they are calculated using RESK. The energy group structure is WIMS-D 69 group structure. DRAGON5 code is used to calculate the effective multiplication factors and fuel temperature coefficients (FTC) at 600K(HZP) and 900K(HFP). The FTC is calculated as follows :

The impact of resonance elastic scattering on the FTC is given in Table 1. It can be seen that taking into account the resonance elastic scattering makes the FTC more negative by about 10% for the HFP case. The differences of effective multiplication factor between the two transfer kernels are summarized in Table 2. The results show that the RESK make the values of effective multiplication factor more negative, and the values are reduced about 150pcm for HFP cases with high enrichment. The reason for decrease of FTC and effective multiplication factor is that the neutron upscattering effect makes more neutrons be absorbed by U-238. The above results are comparable with the previous works.

Table 1 Impact of resonance elastic scattering on FTC

Table 2 Difference of keff between asymptotic kernel and RESK (pcm)