Fukushima: now for the tough part

(Reuters) - The operator of Japan's crippled Fukushima nuclear plant will as early as this week begin removing 400 tonnes of highly irradiated spent fuel in a hugely delicate and unprecedented operation fraught with risk.

Carefully plucking more than 1,500 brittle and potentially damaged fuel assemblies from the plant's unstable Reactor No. 4 is expected to take about a year, and will be seen as a test of Tokyo Electric Power Co's ability to move ahead with decommissioning the whole facility - a task likely to take decades and cost tens of billions of dollars.

If the rods - there are 50-70 in each of the assemblies, which weigh around 300 kg (660 pounds) and are 4.5 meters (15 feet) long - are exposed to air or if they break, huge amounts of radioactive gases could be released into the atmosphere.

The hazardous removal operation has been likened by Arnie Gundersen, a veteran U.S. nuclear engineer and director of Fairewinds Energy Education, to trying to pull cigarettes from a crushed pack.

When the time comes, extracting spent fuel from the plant's other reactors, where radiation levels are much higher because of core meltdowns, will be even more challenging. Reactors No. 1 and No. 3 sustained heavier damage than No. 4 as a result of the March 2011 earthquake and tsunami that knocked out power and cooling at the Fukushima station, triggering three meltdowns that sent a plume of radiation into the air and nearby Pacific Ocean.

The urgency to clear Reactor No. 4 of the fuel assemblies is because of the risk in having spent fuel stored at such a height - some 18 meters above ground level - in a building that has buckled and tilted and could collapse if another quake strikes. ...