[en] The Advanced Test Reactor (ATR) is a 250-MW (thermal) water-cooled reactor located at the Idaho National Engineering Laboratory. The reactor is used primarily to test materials in a radiation environment for defense related programs. Operation of this facility includes processing of radioactive waste streams in solid, liquid, and gaseous forms. Since the materials tested in reactor experiment facilities are sometimes destructively tested, the radwaste process capabilities for experimental facilities must be capable of handling a relatively wide range of contamination levels in the waste streams. Modifications to the original plant (designed in 1967) have been concerned with reducing the volume and activity level of liquid waste. Included are modular filtration and ion-exchange units were developed to convert canal cleanup from an open loop flush to a closed loop recirculation system. Another plant improvement involved an ion-exchange treatment system that reduces the level of radiological contamination in the low-level waste water. A system to evaporate the water from high-level waste is presently in development, and is also discussed