Ryota Takakura was working at the Fukushima Daiichi nuclear power plant on March 11 2011, packing low-level radioactive waste into drums when the ground began to shake and then heave like a ship in a storm.
The lights went out, leaving Takakura and his colleagues in pitch darkness, as the largest earthquake in recorded Japanese history rocked the plant and its waste disposal building. But worse was to come 40 minutes later when a tsunami the height of a four-storey building rushed over the shore.
The wave killed more than 15,000 people in north-eastern Japan. It also knocked out the auxiliary diesel generators at Fukushima Daiichi, leading to the meltdown of three reactors at the plant, one of the worst nuclear disasters in history.