BNFL Inc. was contracted by the Department of Energy to design a facility to stabilize liquid radioactive wastes that are stored at the Hanford Site in the state of Washington. Because of its experience with radioactive waste stabilization the Savannah River Technology Center (SRTC) of the Westinghouse Savannah River Company worked with BNFL to help design and test certain parts of the waste treatment facility. One part is the separation of the highly radioactive solids from the liquid wastes by cross-flow filtration. This paper discusses the results of a cross-flow filter in a pilot-scale experimental facility that was designed, built, and run by the Experimental Thermal Fluids Laboratory of SRTC. To test this filter a waste simulant was developed to prototypically represent the chemical and physical characteristics of one radioactive waste stream. The insoluble solids loading of the simulant was varied from 0.5 wt% to 8 wt%, the aqueous solution was high in sodium and free hydroxide with total solids loadings up to 36 wt%, and the particle sizes ranged from 0.5 to 5 microns in diameter. The simulant matched the waste with a pH > 14, and molarities of sodium, nitrates, and nitrites, of approximately 5.5 M, 1.4 M, and 1.2 M respectively. The cross-flow filter unit was made of seven 316L stainless steel sintered-metal tubes in parallel. Each tube was identical, with a porous length of 1.01 meter, 9.5 mm inside diameter, 12.7 mm outside diameter, and a total filter area of 0.211 m2. The manufactured pore-size rating was 0.1 micron.