Via The Guardian: Fukushima two years on: a dirty job with no end in sight. Excerpt:
Carefully, gently, one-by-one. The removal of nuclear fuel rod assemblies from a badly damaged building at the Fukushima Daiichi power plant is finally under way. Months in the planning, the job is risky, complex, and crucial. Here begins the first major step in the toughest decommissioning project ever attempted.
Fukushima is home to six nuclear reactors, three of which were running when the giant tsunami swept across the site on 11 March 2011. The defuelling operation centres on the building for reactor four. Though the reactor was shut down for maintenance when the towering wave struck, all its radioactive fuel, and more from earlier runs, was held in a storage pool on an upper floor of the building.
Under normal conditions, the storage pool above the reactor was a safe haven. But four days into the crisis a hydrogen explosion tore through the structure and blew the walls and roof off. Moving the radioactive fuel from the wrecked building to a more secure site became a high priority.
Some fuel assemblies have already been moved. Workers use a crane to reach down into the pool, lift an assembly from its rack, then lower it into a waiting cask that sits upright on the pool floor. When a cask is full – each can take 22 fuel assemblies – a second crane hoists it from the pool and places it on a trailer. Filled casks are then transported to a more secure storage facility on the site.
The procedure sounds straightforward enough. But there are 1,533 fuel assemblies in the pool at building four. Each is 4m long, and holds up to 80 individual fuel rods. The team of 36 workers that are responsible for the job will work in six shifts around the clock. The job will take until the end of 2014. And that is with no glitches.
But the work at reactor four is only the start. Once the fuel is removed to a safer place, workers will turn their attention to a further 1,573 fuel rod assemblies held in similar pools in the buildings for reactors one, two and three. All were running when the tsunami struck; all suffered meltdowns. The radiation in these buildings is still intense, and access inside is limited.
Though delicate and painstaking, retrieving the fuel rod assemblies from the pools is not the toughest job the workers face. More challenging by far will be digging out the molten cores in the reactors themselves. Some of the fuel burned through its primary containment and is now mixed with cladding, steel and concrete. The mixture will have to be broken up, sealed in steel containers and moved to a nuclear waste storage site. That work will not start until some time after 2020.
To fully decommission Fukushima Daiichi might take 40 years and no one expects a cakewalk. Independent researchers point to the litany of mishaps that has blighted the cleanup. They doubt the plant's operator Tokyo Electric Power (Tepco) is up to the task, and want a global team of experts to take over. Even high-level advisers signed up by Tepco describe the decommissioning project as an "unprecedented" challenge. At stake is Tepco's reputation, the health and livelihoods of local communities, and the future direction of the industry worldwide.