Effective Dose Calculations and Dose Rate Distribution Around Z-Portal Passenger Security Screening

Abstract

Due to the increased concern over terrorist attacks, new technologies have been developed to improve the efficiency of security screening of passengers. The Z – portal is an inspection system designed to scan vehicles and large trucks, buses, and cargo containers. It has been installed in many sites in Egypt. The passenger should be screened before allowing to pass from a land to another. This technology uses ionizing radiation (X-rays). As the hazards related to ionizing radiation include the well-known carcinogenic risk, as well as other health effects, assessment of public exposure to these new types of security screening of a great importance we are presenting an assessment and distribution mapping of dose rate around two portals, then effective dose calculations and statistical analysis was performed. Methods: Two Z-portal systems are used for screening passenger by vehicles and trucks; Measurement of radiation dose rate was performed using dose rate survey meter, exposed with the two units during ten consecutive exposures each the organ effective doses was calculated. Results: Effective radiation doses ranged between 0.41 µSv and 6.66 µSv for one exposure. Thyroid, bone marrow, colon, lung, stomach, breast absorbed the most radiation for both screening systems with p <0.001. Conclusions: Effective doses of organ screened by the transmission system is significantly higher than the backscatter system however both systems are exceeding the dose limit of the general public per scan, as per ANSI standards of 0.1 µSv per scan for individual, cumulative effect is not considered, both systems should be reevaluated based on the general principles of justification, optimization and dose limitation versus new screening technology like passive millimeter – wave with no radiation emission.