A disk tubular reverse osmosis (DTRO) membrane system was designed and applied for the treatment of radioactive wastewater produced in a high-temperature gas-cooled reactor (HTGR) in pilot scale. The pretreatment system was simplified using a cartridge filter. A three-stage membrane system was researched and developed. The performance of the DTRO system was examined using surrogate wastewater. The volume reduction factor of the system reached 50, and the decontamination factor reached 5760. The membrane system was designed to operate at high flows. When wastewater was pumped into the membrane system, the high-speed flow of the influent prevented the fouling of the membrane. The operational performance to treat low- and intermediate-level radioactive wastewater was examined. The membrane system can be used to treat the wastewater from HTGR.