The growing terrorism threat based on the use of special nuclear materials (SNMs), which includes highly enriched uranium (HEU), weapons-grade plutonium (WGPu), or high-activity radiological sources has reinforced the need for improved population protection mechanisms. The motivation for the development of a radiation portal monitor is the need for inspecting cargo at various entry points of the country. This inspection process requires scanning many containers for the presence of SNMs such as Uranium, Thorium, and Plutonium. In this study, we have worked on designing a system with eight NaI (Tl) detectors for the detection of any gamma-emitting radioactive source. The multichannel analyzer for collecting the data from the detectors has also been indigenously developed using PXIe-6386 data acquisition system with a sampling rate of 14 MS/s. The system is automated using labview platform. The system is capable of detection as well as identification of the SNMs passing through it in static conditions. The energy spectra of various radionuclides, such as 137Cs, 60Co, and 54Mn, measured using our RPM have been used for the validation of the identification of sources with unknown energy lines.