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 strontium-bearing 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 similar to 90-100 degrees 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)(2)CO3 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.