PURPOSE: To enable the recovery of thermal energy emitted from vitrified solids.

CONSTITUTION: Numerous vitrified solids 1 are housed in a low-temperature fluorocarbon evaporation furnace 2, where liquid fluorocarbons FL is poured so as to let the vitrified solids 1 soak in it. A cycle line 3 equipped with a condenser 4 connects the top and the bottom of the low-temperature fluorocarbon evaporation furnace 2. A turbo generator 5 is installed on the upstream side of the condenser 4 on way of the cycle line 3. By supplying the fluorocarbon steam FG given off by the heat generation of the vitrified solids 1 to the turbo generator 5 through the cycle line 3 to revolve a turbine 5a for the generation of electricity, thus the thermal energy of the vitrified solids 1 is recovered as electricity.