Room: ePoster Forums
Purpose: In order to calculate required shielding thicknesses outside laminated barriers to reduce radiation exposures to acceptable limits, an analytical method was proposed for calculating gamma ray exposure rate for different arrangements of shielding materials for medical accelerator rooms.
Methods: An analytical method taking into account an appropriate exposure buildup factor EBF was developed to calculate the exposure rate outside a laminated barrier. Different shielding materials such as lead, steel and iron adding to the ordinary concrete to the primary barrier were investigated for the ten and fifteen MV photon spectra of Varian high-energy accelerators. The geometric progression and Lin and Jiang formulas were used to calculate gamma ray exposure buildup factor in both single and multilayer shielding materials for a point mono-energetic and point poly-energetic sources.
Results: The obtained results showed a good agreement between the calculated exposure build up factors and those of Monte Carlo EGS for both single and multilayer shield. In addition, the obtained exposure rate values are compared with those obtained using the tenth value layer TVL concept. A general good agreement was obtained. Also, the optimum barrier thickness to minimize radiation exposures to an acceptable level was determined. It was observed that the use of a laminated barrier with leads to a significant reduction of radiation exposures than using concrete shield alone.
Conclusion: The obtained results showed that multilayered barrier presents enough effectiveness to reduce the photon exposure rate outside the radiotherapy bunker compared to the standard single barrier of concrete.
Not Applicable / None Entered.