Differences in reactivity for the MISTRAL-1 core obtained with TRIPOLI-4^®. The solid blue line is the best-fit curve obtained with the JEFF-3.1.1 library alone (see Fig. 5). The solid red line is the best-fit curve obtained when the thermal scattering laws of H₂O and UO₂ are replaced by those of JEFF-4T1. The slope of each line gives the calculation bias on the isothermal reactivity temperature coefficient α_iso. For clarity, the uncertainties are shortly discussed in Section 3 and not reported in the plot.