In order to develop a treatment of low-level radioactive miscellaneous solid waste containing combustibles by plasma melting technology, the incineration of polyethylene (PE), the main combustible in the wastes, is examined by using a 100 kW plasma melting system. The overall reaction rate of PE in the plasma furnace is examined by changing the air flow rate, the feeding weight of PE, and the shape of PE. The reaction rate is found to be independent of air flow rate, and the shape of PE. The reaction rate is thus a function solely of weight of PE fed, and can be used to estimate the residence time of PE with a given weight required for complete incineration.