Background: Nuclear security and safety is becoming one of the most concerned topics around the world after Fukushima nuclear accident. Recent reports of IAEAshow that the potential risks exist internationally and domestically. A good solution of promoting nuclear security and safety is to develop advanced nuclear radiation monitoring technologies including γ-ray imaging. Purpose: In order to improve the sensitivity of a γ-ray imaging system with little increase of system complexity and cost

rotating modulator (RM) imaging technique using non-position-sensitive detectors was first introduced in nuclear monitoring studies. Methods: Modulation pattern of RM system was deduced mathematically and its profile was calculated by a dedicated program written in Matlab. The system sensitivity was analyzed based on the profile. Detector outputs were produced by Monte Carlo simulation. The Noise-Compensating Algebraic Reconstruction (NCAR) algorithm was applied to the image reconstruct from simulated outputs. Results: A RM imaging system has a relative sensitivity of 62% compared with a coded aperture system when detector areas of the two systems are equal. On condition that the detector diameter is 3.8 cm and image distance is 80 cm

an angular resolution of 0.8° is achieved. Conclusion: Based on the simulating results

a RM system design suitable for vehicle and robotic platform is proposed.Cited