Explainer-More nuclear challenges await Japan after Fukushima water release

Twelve years after the Fukushima nuclear disaster, Japan has started to release treated radioactive water into the sea, a key step in the process of decommissioning the stricken plant, but much tougher tasks lie ahead, such as molten fuel removal. Here are the challenges facing the government and plant operator Tokyo Electric Power Co (Tepco) as they try to draw a line by the middle of the century under the world's worst nuclear accident since Chornobyl.