Background: The peaceful use of radioactive materials is a huge wealth for humans

but illegal transfer of radioactive materials brings a serious potential safety hazard to the public security. Purpose: This study aims to design a gantry system for ? radiation detection to avoid the illegal transfer of radioactive materials. Methods: MCNP code is used to simulate the system which measured two typical ? sources (137Cs and 60Co) using two plastic scintillator detectors (EJ200) in the size of 200 cm × 40 cm × 6 cm. Nuclides are identified by analyzing the spectrum

and locations are obtained according to the response of NaI(Tl) detector array. Results: Theoretical computation results showed that ?radiation detection limitation of this system was identified to be 370 Bq for both 137Cs and 60Co

characteristic peaks can be identified effectively

and locations of 137Cs are obtained rapidly and accurately. Conclusion: This system satisfies the use of crowd places well

and prevents ? radioactive sources from transferring illegally in the event of a nuclear accident. Abstract