Dive summary:

• The previous means to store Intermediate Level Waste, the most common of all nuclear waste, was to mix the waste with cement and seal it in steel drums to be buried deep underground, but glass may be the future.
• A new method called "vitrification," is a process of turning the waste into glass, a process previously only used for High Level Waste (HLW), but has been proven to reduce levels of reactivity and the volume of the waste.
• The method was never used for ILW before because the technology was considered to be unsuitable to handle large quantities of waste comprised from a variety of different materials.

From the article:

University of Sheffield researchers have shown, for the first time, that a method of storing nuclear waste normally used only for High Level Waste (HLW), could provide a safer, more efficient, and potentially cheaper, solution for the storage and ultimate disposal of Intermediate Level Waste (ILW). ...