Safety is a mandatory issue during the operation of a nuclear power plant. A nuclear reactor can have some atmospheric dispersion due to any errors in the safety system.

The aim of this study is to estimate the cancer risk incidence for different body organs due to accidentally released radionuclides from Bushehr Nuclear Power Plant (BNPP).

The assumed hypothesis was atmospheric dispersion of radionuclide into the environment due to the safety failure of BNPP. Total effective dose equivalent (TEDE) from radionuclide diffusion in the medium was calculated using HOTSPOT code at two different wind speeds. Finally, the risk of cancer incidence for different organs of male and female sex has been estimated by Biologic Effects of Ionizing Radiation (BEIR) VII model.

The results showed that with increasing the exposure age and attained age, the risk of cancer incidence for different organs is decreased. The value of TEDE was increased at lower wind speed. The most probable organ for cancer incidence at different levels of TEDE in male and female sex was colon and bladder, respectively. On the other hand, prostate and uterus had the lowest radiation sensitivity and cancer risk incidence in male and female sex, respectively. Increasing the wind speed reduces the risk of cancer incidence for all of organs understudy.

Based on the obtained results, it can be concluded that the younger persons are more subject to the cancer risk incidence because of both the intrinsically greater radio-sensitivity of their organs and their longer remaining life expectancy during which a cancer may develop. The overall risk of cancer incidence as well as the site specific solid cancer incidence were highly dependent to the sex of exposed person, so that the female sex was more exposed to the cancer risk incidence at all of the irradiation levels understudy.

The effective source to surface distance (SSDeff) for different combinations of energy/applicator size of the electron beam produced by the light intraoperative accelerator, a mobile dedicated intraoperative radiotherapy accelerator, has been calculated in this study.

Both ionometric dosimetry and Monte Carlo (MC) simulation were followed to obtain the SSDeff for different combinations of electron energy/applicator size. Simulations were performed using Monte Carlo Nuclear Particles (MCNP) MC code. Measurements were performed by Advance Markus chamber and inside a polymethyl methacrylate slab phantom. Inverse square law method was employed to determine the SSDeff from acquired dosimetry data.

With increasing the applicator diameter at a given energy, SSDeff is also increased. The same result is obtained with increasing the electron beam energy for a given applicator size. The results of MC-based SSDeff for 10 cm diameter reference applicator at different energies were in a good accordance with those obtained by ionometric dosimetry. The maximum and mean differences between the results were 1·1 and 0·6%, respectively.

The results of this study showed that SSDeff of intraoperative electron beam is highly dependent on the applicator size and is a mild function of electron beam energy. These facts are in accordance with those reported for conventional electron beam. The good agreement between the results of MC simulation and ionometric dosimetry confirms the application of MCNP code in modelling of intraoperative electron beam and obtaining the intended parameters.