Validation of the $^{238}$U inelastic scattering cross section through the excalibur dedicated experiment

Abstract : EXCALIBUR is an integral transmission experiment based on the fast neutron source produced by the bare highly enriched fast burst reactor CALIBAN, located in CEA/DAM Valduc (France). Two experimental campaigns have been performed, one using a sphere of diameter 17cm and one using two cylinders of 17cm diameter 9cm height, both made of pure $^{238}$. A set of 15 different dosimeters with specific threshold energies have been employed to provide information on the neutron flux attenuation as a function of incident energy. Measurements uncertainties are typically in the range of 0.5-3 % (1$\sigma$). The analysis of these experiments is performed with the TRIPOLI4 continuous energy Monte Carlo code. A calculation benchmark with validated simplifications is defined in order to improve the statistical convergence under 2 per cent. Various $^{238}$U evaluations have been tested: JEFF-3.1.1, ENDF/B-VII.1 and the IB36 evaluation from AIEA. A sensitivity analysis is presented to identify the contribution of each reaction cross section to the integral transmission rate. This feedback may be of interest for the international effort on $^{238}$U, through the CIELO project.