Impact of H in H2O thermal scattering data on criticality calculation: uncertainty and adjustment

In this paper, the impact of the thermal scattering data for H in H20 is estimated on criticality benchmarks, based on the variations of the CAB model parameters. The Total Monte Carlo method for uncertainty propagation is applied for 63 keff criticality cases, sensitive to H in H20. It is found that their impact is of a few tenth of pcm, up to 300 pcm maximum, and showing highly non-linear distributions. In a second step, an adjustment is proposed for these thermal scattering data, leading to a better agreement between calculated and experimental keff values, following an increase of scattering contribution. This work falls into the global approach of combining advanced theoretical modelling of nuclear data, followed by possible adjustment in order to improve the performances of a nuclear data library.