Japanese utility Tokyo Electric Power Co said it removed nuclear fuel debris left inside a reactor in a demonstration at its Fukushima power plant, 13 years after a meltdown.

Radioactive debris was removed from unit 2 at Fukushima Dai-ichi Nuclear Power Plant and was placed inside a sealed container for transportation, the power producer said in an emailed statement on Thursday.

The demonstration is part of Tepco’s clean-up plan for the site, after a massive earthquake and tsunami in 2011 overwhelmed the Fukushima facility and led to the worst nuclear disaster since Chernobyl. The whole process is expected to cost around 23 trillion yen ($149 billion) and take decades to complete. About 880 tons of radioactive material, like melted fuel and metal cladding, are said to be stuck at the bottom of the three reactors at the plant.

READ MORE: TEPCO discharges more Fukushima nuke water despite criticisms

Tepco, which is decommissioning the plant alongside the Japanese government, is using a robotic arm that looks like a fishing rod with a claw grip to remove a small sample of the nuclear debris. The company had planned to remove just 3 grams as part of the demonstration.

The removed debris is set to be transported to Japan Atomic Energy Agency’s research facility for analysis, according to Tepco’s website.

READ MORE: Kishida to hold ministerial meeting on Tepco nuclear plant restart

The retrieval process began in September but faced challenges. A camera attached to the robotic arm stopped working, forcing Tepco to suspend the demonstration to replace the camera.