Improvement of 238U Inelastic Scattering Cross Section for an Accurate Calculation of Large Commercial Reactors

To meet the target-accuracy required by GEN-3 and GEN-4 designs, 238U(n,n′) uncertainty has to be reduced from ±15% (current standard deviation) to ±5%. The improvement of 238U scattering data has been achieved through the use of targeted integral measurements with a strong sensitivity to 238U(n,n′). From the C/E biases and sensitivity coefficients, obtained from Monte Carlo TRIPOLI4/JEFF-3.1.1 calculations, we have re-estimated the 238U data. A clear trend to reduce 238U(n,n′) cross-section by (−11±3)% in the 2–5 MeV range is obtained, and the analysis using inelastic level sensitivities highlights a required () modification by (−10±2)%.