[externedguy]

Circles are not grouped in any way, just overlaid.

If you hover on the center of the circle you'll see all of the Chinon blocks (they're 7: A1-3 and B1-4). You can search for "Chinon" to see them on the list or just click the circle that will scroll the list to the section where all the blocks are visible.

Will try to find a more intuitive way to show the reactors that are located in the same place.