Estimation of systematic uncertainty in calculated results by PHITS with nuclear reaction cross section model

Hashimoto, Shintaro  ; Iwamoto, Osamu  ; Sato, Tatsuhiko   ; Niita, Koji*

PHITS has been used for many purposes such as radiation shielding in accelerator facilities. The PHITS result includes not only statistical error related to the number of trials in the Monte Carlo method but also systematic error attributed to uncertainty of nuclear data and nuclear reaction model. In the previous study, we developed a method to estimate the influence of uncertainty of nuclear data for neutrons below 20 MeV on PHITS results. In this study, we evaluated uncertainty of a cross section model to also consider neutrons above 20 MeV. In the method, we change the cross section within the uncertainty, and execute PHITS using each cross section. Because the result depends on the cross section, we regard its variance as the systematic error. We applied the method to estimate the systematic error of 100 MeV neutron flux in neutron shielding calculations. The systematic error of the calculated flux depends on the depth in shielding material due to the number of scattering.