Inside Fukushima – for the most delicate stage of the clean-up yet

It has been dubbed a catastrophe in the making and even the potential trigger for mankind’s most dangerous moment since the Cuban Missile Crisis. But it was hard to reconcile those fears with the banal sight of a murky pool of water at the Fukushima Daiichi nuclear plant.

The storage pool in unit four of the ruined plant has inspired terabytes of sweaty internet hyperbole and a string of dire warnings, including one from Japan’s former ambassador to Switzerland. In letters to the UN, Washington and several Japanese politicians, Mitsuhei Murata says a major incident at unit four could leave much of Japan, including Tokyo – the world’s most populated metropolis – uninhabitable.

This month, nuclear engineers are set to begin removing thousands of highly radioactive spent fuel rods from the pool where they have precariously lain since the plant was pummelled by a huge earthquake and tsunami in March 2011. Experts say removing more than 1,500 fuel assemblies, each containing 80 uranium rods, is the most dangerous stage of the Fukushima clean-up.

Tokyo Electric Power Co, Fukushima’s operator, swatted away such concerns this week, however, during a rare media tour of the plant. “In my view, the potential for another disaster is very close to impossible,” the plant manager, Akira Ono, said. “Removing spent fuel is done at any ordinary nuclear power plant.” Tepco says the operation could begin next week.

Takashi Hara, the head of the operation, said: “We’re confident this task will be done successfully.” Just in case, he said, Tepco had built an alarm system that would warn workers to evacuate if radiation climbed dangerously high.

After its cooling system was disabled by the 2011 earthquake and tsunami, a series of explosions tore apart four of the six reactor buildings.

The site is still a mess of makeshift piping, tangled metal and debris. Overturned cars and cranes rust behind newly erected seawalls. Pipes carry water from the damaged reactors to a hangar-like decontamination facility, where caesium and dozens of other toxins are removed. More than 1,000 storage tanks, holding a combined 350,000 tonnes of contaminated water, crowd the 860-acre site. Hundreds of trees have been removed to make space for more tanks.

Engineers have erected a new building alongside the damaged unit four, and a crane to remove the fuel assemblies, which will be placed in sealed casks and taken to a more stable storage area.

Engineers must remove the fuel assemblies one by one, without incident, and each time deal with the risk of fire or the cooling water boiling dry. The building lists slightly but Tepco says it has been reinforced against the possibility of another strong quake. And there is always the chance that very small pieces of debris left behind “will affect the operation’s smoothness,” admitted Mr Ono.

Outside the plant, thousands of workers continue trying to decontaminate hundreds of square miles of land affected by radiation. Evacuation orders have been lifted on some towns, but most families have stayed away. The government says it will be “difficult for residents to return for a long time” to the 10km zone nearest the plant, a polite euphemism for permanent exile, say critics.