**4.1 Monte Carlo radiation transport codes**

The Monte Carlo method, which is used to establish transport codes, has proved to be efficient for simulating different types of irradiation for objects of various shapes and geometries [4, 52–55]. **Table 3** provides transport codes for simulating the interaction of particles with the matter as well as energy ranges and materials that can be used in simulation [56].

While the EGSnrc and PENELOPE codes are limited in their application to the objects of simple geometry [5, 6], transport codes MCNPX and GEANT4 are more widely used in the industry as these are more comprehensive instruments for simulating a wider variety of physical processes representing the interactions of electrons, photons, protons, and neutrons [7, 8]. The MCNPX code is used in nuclear medicine, radiation safety, accelerator development, and modeling industrial irradiation of biological objects and materials [52]. GEANT4 is currently the most complete set of tools for simulating the passage of particles through matter [8]. Its fields of application include high energy physics, nuclear and accelerator physics, and medical and space science research. Unlike other codes, GEANT4 simulates any geometry of the objects and the radiation source with any energy spectrum and traces physical processes selected for a particular irradiation method and objects, which makes GEANT4 the most flexible transport code with a wide scope of uses [57].
