In this study, we discuss the preparations of thin-film composite polyamide (TFCP) membranes in spiral configuration and their potential for concentration of simulated cesium and strontiumbearing effluent solution (only cesium chloride, strontium chloride and sodium chloride) by forward osmosis (FO). The membranes are prepared by in-situ polymerization technique using m-phenylene diamine (MPD) with phenol and trimesoyl chloride (TMC) system over hydrophilic sulfonated polyethersulfone support followed by heat curing in steam (temperature ~90–100°C). Prepared membranes are characterized in terms of separation performance in FO mode (de-ionized water as feed and 1.0 M NaCl solution as draw solution). When phenol additives are added into water phase, the membrane achieved high water flux of 25.6 L m−2 h−1 with a modest salt flux of 6.43 g m−2 h−1. A 2512 spiral element was rolled using indigenously developed TFCP-FO membranes and performance was evaluated in terms of volume reduction and back-diffusion of draw solution salts using simulated feed solution (500-ppm NaCl; 1-ppm SrCl2 and CsCl each) with 2(M) solutions of CaCl2 & (NH4)2CO3 as draw solution. It was found that the volume reduction of the feed solution is 61–65% after 3 h and back diffusion of cesium and strontium from draw solution to feed are found around 0.022–0.029 ppm.