Japan launched two micro-drones and a “snake robot” on Thursday towards one of the plant’s three nuclear reactors, which was crippled by a tsunami in 2011, the plant’s operator said.

The devices were deployed in preparation for the removal of hundreds of tons of highly radioactive fuel and rubble, a hazardous operation expected to take decades.

A spokesman for Tokyo Electric Power Co (TEPCO) told AFP that in addition to Thursday’s “snake robot”, “we also sent two drones yesterday and two more drones today”.

The small drone is “highly maneuverable and has enhanced photography capabilities” due to its “cramped and dark” interior, the company said.

“The snake robot… is equipped with a wireless communications repeater so that we can properly cover the radio transmission area for small drone operations,” a statement said.

The inside of the reactor building is too radioactive for people to enter, and the purpose of the drone is to inspect the area before robots clear away the fuel and rubble.

TEPCO plans to conduct a small-scale fuel debris removal test in October.

TEPCO has sent underwater robots to inspect parts of the facility that are still submerged, a spokesman said.

“It will take a long time to fully take off these 800 tons (of fuel) because the decommissioning period is expected to be 30 to 40 years,” he said.

Separately, Tokyo Electric Power Co. began discharging the fourth batch of treated wastewater from the Fukushima nuclear power plant into the ocean on Wednesday.

The process has been approved by the United Nations nuclear watchdog, but China and Russia responded by banning seafood imports from Japan.

The 2011 earthquake and tsunami killed approximately 18,000 people. The disaster at the Fukushima nuclear power plant in northeastern Japan was one of the worst atomic accidents in history.