The melting process is suitable for reducing the volume of low-level radioactive miscellaneous solid wastes before disposal. It is because they give high volume reduction ratio and stable processed wastes. We have developed a new type high frequency induction heating and melting system for the processing of incombustible solid wastes. In our melting system, not only metallic but inorganic wastes, e.g. thermal insulators, glasses, concrete and incinerated ash, could be melted within an alumina based ceramic canister. We applied a heat loss compensation (Active Insulator) to reduce the heat flow through the around surface of canister. The Active Insulator made of electrically conductive material, e.g. graphite. This idea is based on non-radioactive melting tests and detail thermal analyses.