Voronoi fracture can generate interior faces, but won’t create uv’s. The Inside Face UVs HDA will generate automatic uv’s for these interior faces.
The only requirement is that 'inside' and 'outside' groups have been defined by the voronoi fracture sop, which is the default behavior.
Amount of uv space to use; 1 will use the 0-1 range, 2 will use 0-2 etc.
UV Flattening Method
How to flatten 3d geometry into uv space, see the 'UV flatten' sop help for details.