Impact of new results of the neutron capture cross section measurements for odd gadolinium isotopes on thermal-spectrum systems

Light Water Reactors (LWRs) are frequently equipped with fuel pins in which UO2 is mixed with Gd2O3. Gd odd isotopes have extremely high neutron capture cross sections at very low energies and are currently used as burnable poisons. For this reason, ENEA put forward a research proposal for an improvement of the Gd nuclear data accuracy by means of new experiments to be done in the framework of the n_TOF Collaboration. In 2016, new measurements were performed at the CERN, and subsequently ENEA in collaboration with IRSN, started to re-evaluate the neutron capture cross sections (XSs) of Gd odd isotopes. This paper presents the results of Monte Carlo simulations performed with the new measured data to estimate their impact on the criticality of a thermal-spectrum benchmark for which the value of k(eff) is known. The outcomes demonstrate that the new data can produce a k(eff) which is closer to the experimental one than that obtained using the currently available Gd evaluations.