Select municipalities within a radius

How to realize a selection of municipalities in a radius of 30 km around a reference municipality ?

ie: The municipalities surrounding the city of Chinon in Indre-et-Loire (37).

This map is realized from the 5.6 version of C&D.

Diagram and realization

This diagram is feasible from the files present by default at the end of the installation of C&D.

Click on the diagram to enlarge