ORNL Oxygen Broomstick Experiment: MCNP model and evaluation results for SINBAD entry NEA-1517/59

The existing entry NEA-1517/59 (SDT2) of the SINBAD database comprises the results of measurement of the neutron transmission spectra through the liquid oxygen broomstick of the length 60” (152.4 cm). The experiment was performed in 1965 at the Tower Shielding Facility located in Oak Ridge National Laboratory and was designed to measure the neutron total cross sections in the range of 1.9 – 8.6 MeV. The purpose of the present work was to assemble the MCNP input deck for the Monte Carlo code MCNP, perform the sample calculations of the radiation transport and sensitivities with evaluated neutron reaction cross section from ENDF/B-VIII.0 and JEFF-3.3, to show the impact on the (n,tot) and (n,α) cross sections and thus to demonstrate the value of this benchmark for the validation of the modern evaluated data. The impact of validation benchmark on $^{16}O(n,α$_0$) cross section was shown do agree with the thick target neutron yield induced by α-particles with energies up to 5 - 6 MeV in carbon. An attempt was also made to find the missing measured data for other ORNL O-broomsticks of length 24” (60.96 cm), 36” (91.44 cm) and probably 72” (182.88 cm).