Absorbed Dose Assessment from Alpha and Gamma Rays of Radon Progeny in Trachea Tissue

Radon is a natural radioactive gas that easily enter to respiratory tract and cause considerable biologic damages. The main objective of this study was to determine the dose from the alpha and gamma radiations of radon decay chain products in trachea tissue using Monte Carlo simulation.

At first a trachea-equivalent cylindrical phantom was simulated by MCNPX Monte Carlo code. Then, dose profiles from alpha and gamma-emitter progenies were separately calculated. The daughter radionuclides were considered as suspended particles with uniform distribution inside the trachea inner volume.

The results showed that the received dose by trachea in alpha decay is considerably higher than that of gamma decay. The maximum administered dose by alpha decay was 1.72×10-16 Gy/decay. 218Po was had the highest dose among the studied alpha emitter daughter nuclides. The maximum administered dose by gamma decay was also equal to the 17.55×10-19 Gy/decay, where 214Pb and 214Bi had almost the same contribution in calculated dose.

The daughter radionuclides from radon decay chain, especially alpha emitter products of 218Po and 214Po, can be considered as a serious danger viewpoint to the internal exposure. These daughter nuclides can attach to the inner wall of trachea and remain in the respiratory system for long periods of time which can cause to the continuous exposure of trachea. Reducing the biologic effects of these internal radiation source requires especial schemes in order to avoid entering the radon and its radioactive daughters to human respiratory system, as much as possible.