Calculation of neutron fluence-to-absorbed-dose conversion coefficients using Monte Carlo simulations and a pair of Chinese adult male and female phantoms.

For purposes of radiation protection and risk assessment involving neutron exposures, conversion coefficients linking external measurable fields to the organ absorbed dose and effective dose are essential dosimetric data for situations such as space exploration. This study utilized the TOPAS (TOol for PArticle Simulation) Monte Carlo code to calculate neutron fluence-to-absorbed-dose conversion coefficients for a pair of Chinese population-averaged University of Science and Technology of China Adult Male and Female Phantoms. Simulations were performed for mono-energetic neutrons ranging from $1\times{10}^{-9}$ MeV to 10 GeV for standard AP, PA, LLAT, RLAT, ROT, and ISO irradiation geometries. To evaluate the impact of anatomical differences between phantoms representing the Chinese and Western populations, results were compared against those calculated for International Commission on Radiological Protection Computational Phantoms. Finally, a neutron source spectrum for the surface of the Moon is used to show how the conversion coefficient can be used for conditions involving the mission to the Moon. The results reveal that for the majority of the organs, the computed neutron fluence-to-absorbed-dose conversion factors are in good agreement. However, profound differences are observed for organs such as the breast, ovaries, and testes. These findings highlight the importance of employing population-specific phantoms for accurate dose estimates in radiation protection and risk management.