A Monte Carlo study on the impact of indirect action on neutron relative biological effectiveness.

This article focuses on the development and application of an updated Monte Carlo simulation pipeline that incorporates a model for indirect radiation action to study neutron-induced DNA damage and estimate neutron relative biological effectiveness (RBE) in causing clustered DNA lesions. The study validated the indirect action model using proton irradiation data and then applied it to simulate neutron and photon interactions with nuclear DNA, finding that indirect action significantly increases DNA damage yields and amplifies the effects of direct action, especially at lower neutron energies. Although the estimated neutron RBE values correlate qualitatively with existing radiation protection factors and previous studies, they are lower in magnitude, suggesting model limitations and the need to consider additional factors such as DNA damage repair and a broader range of secondary particles. The findings highlight the complex interplay between direct and indirect radiation effects in neutron-induced stochastic biological risks, particularly carcinogenesis linked to complex double-strand break clusters in DNA.