The interpretation of the reactivity temperature coefficient measured in the Mistral experiments was performed with the Monte Carlo code TRIPOLI4 from 10°C to 80°C. The nuclear data library JEFF-3.1.1 was used in the calculations. Three different thermal scattering laws of hydrogen in light water were tested in order to evaluate the impact in the Mistral calculations: the thermal scattering laws present in the nuclear data libraries JEFF-3.1.1 and ENDF/B-VII.1, and CAB model. A different approach for creating thermal scattering files, as molecular dynamics simulations (CAB model) was assessed.