Analysis of Dose Distribution for the Gamma Cobalt Irradiation Therapy Unit in Normal and Emergency Conditions

The dose distribution inside the Gamma Cobalt irradiation therapy unit at Egyptian Atomic Energy Authority (EAEA) was determined both experimentally and theoretically. MCNP computer code, based on Monte Carlo method, was used to model the unit and calculate the dose distributions in both normal and emergency situation of the unit. The dose distribution inside the unit was also measured during the unit in operation. The maximum gamma dose distribution measured around the gamma device during operation (the source in position ON) using TLD and AD6-6150 was 2.21 and 2.010 mSv/h respectively, while the maximum gamma dose distribution calculated by MCNP computer code at the same point was 1.952 ± 0.026 mSv/h. The results indicate good agreement between the measurements and theoretical model of MCNP computer code. In case of emergency, and at 50 cm distance from the unit head the dose rate increases to 7000 μSv/h at the nearest point to the unit.