The aim of this paper was quantifying the uncertainties of dosimetry parameters and systematic factors of an in vivo neutron activation analysis (IVNAA) facility for neutron-irradiated individuals with different lung sizes. A series of statistical phantoms with adjustable lungs were modeled in IVNAA facility using Monte Carlo MCNP code. Obtained results showed that the fluctuation of the organ-absorbed dose and effective dose due to the lung size variation is negligible (less than 3 %). Also, changing the lung size will not significantly affect the systematic parameters of the facility.
