TOKYO, Aug 18 (Reuters) - Chugoku Electric Power Co said on Friday it has obtained approval from the Kaminoseki town mayor to make a study for the potential construction of an interim storage facility for used nuclear fuel on Nagashima island in southwestern Japan.

Nuclear power is making a gradual return to Japan's energy mix after the suspension of all reactors following the Fukushima disaster in 2011. It is also preparing to start releasing water from the Fukushima plant into the sea, raising concerns among neighbouring countries.

Chugoku Electric said it would proceed with a study for the storage facility on Nagashima island, without giving details on the timeline for any possible construction.

Nine regional power utilities and wholesaler Japan Atomic Power Co now have 33 reactors available for commercial use, with a combined capacity of 33 gigawatts, versus 54 reactors operating before the Fukushima disaster.

The 820-megawatt No.2 reactor at Chugoku Electric's Shimane nuclear power station has been idle since early 2012.

(Reporting by Katya Golubkova; Editing by Simon Cameron-Moore)