To reduce the volume of the low- and intermediate-level radioactive wastes and to improve the radionuclide confinement after disposal of the slag product, a 500kW-grade DC plasma torch melter system was developed by the KHNP-CRI(Korea Hydro & Nuclear Power Co., LTD Central Research Institute). Main equipment of the system consists of a dual mode plasma torch, a water cooling refractory melter, an waste feeder, a slag tapping equipment, etc. Especially, the high-technology of a dual mode operation of plasma torch is realized with the invention of the KHNP-CRI patented power supply system. Among a series of dual mode performance tests, a 24-hour melting test for typical surrogate non-combustible waste is introduced in this paper. Electrical currents and voltages of the system was well confined under the operation limits at the test. And the slag melt was well stabilized without severe abnormal behavior as well. But for safe and long-run operation, the advanced slag tapping equipment and slag level measurement device should be imported to the system.