Measurement of the244Cm neutron capture cross section at the n_TOF facility at CERN

Accurate neutron capture cross section data for minor actinides are essential for the safe and efficient management of high level radioactive waste produced during the operation of nuclear reactors. In particular,244Cm, with a half-life of 18.11 years, dominates neutron emission in spent fuel and also contributes significantly to the decay heat and radiotoxicity. Furthermore, neutron capture on244Cm opens the pathway for the formation of heavier isotopes such as Bk, Cf, and other Cm isotopes. Sensitivity studies for present and future nuclear reactors have highlighted the need to reduce the uncertainties in the244Cm capture cross section. Experimental data on the capture cross section of this isotope are scarce due to the challenges associated with its measurements. Prior to the presented measurement and two recent measurements conducted at J-PARC, only one set of data for the244Cm capture cross section existed, obtained in 1969 during an underground nuclear explosion experiment. The capture cross section of244Cm has been measured at the n_TOF facility at CERN with three different experimental setups: one at Experimental Area 1 (EAR1) using the Total Absorption Calorimeter and two measurements at Experimental Area 2 (EAR2) with C6[jls-end-space/]D6 detectors, employing two different samples. The results from these three measurements were found to be compatible and then combined. In total, 17 resonances of244Cm were measured at n_TOF below 300 eV. The radiative kernels obtained in this measurement are in good agreement with JENDL-4.0 for the majority of the resonances. Additionally, they are compatible with the recent JENDL-5 library below 50 eV, while at higher energies, the majority of radiative kernels from this evaluation based on the recent measurement by Kawase et al., are not compatible. Additionally, the244Cm samples also contained240Pu. Resonances of this isotope were analyzed in the energy range between 20 and 180 eV, and the results were found to be consistent with previous measurements and evaluations, that enhances confidence in the244Cm results.