Metal melting is a technology to reduce the volume of LLW metal waste.  Depending on the waste being processed and the operational conditions of the furnace it is also possible to decontaminate the metal at the same time as reducing its volume.  In some cases decontamination may be sufficient to allow for reuse of the metal.  In addition to volume reduction, melting provides a homogeneous waste form that makes characterization simpler and easier and produces a stabilized final waste package. 

The metal is melted by means of electrical induction heating or by electric arc in the furnace.  When molten, two phases are created.  The first is a metal phase, which is predominantly clean of contamination.  The second is a slag phase that contains the bulk of the contamination and floats on top of the metal phase.  Fluxing agents are sometimes added to improve the separation of the slag from the metal.  After melting, the slag is drawn off from the furnace and the molten metal is poured into a drum or container.  The slag is sampled to determine its radioactive content so as to calculate the amount of radioactive material left in the filled drum or container. 

Some combustible and volatile materials including volatile metals and metal oxides are contained in the slag but the majority leaves as a gas into an off-gas system.  The components of the off-gas system are similar to all thermal treatment processes and depend on the radionuclide inventory of the waste.  Typically it will include a quencher or wet scrubber to cool the off gas before filtering in HEPA filters. 

The treatment of radioactively contaminated steels will depend on whether the contamination lies within the bulk of the steel or on the surface.  In the case of surface contamination, the melting process will distribute the activity within the bulk metal.  Consequently, if melting technologies are used to process steels and the aim is to maximize the reduction of activity, it is important to remove surface contamination before treatment if the reduction/removal of radioactivity is to be achieved.