What could be the most-dangerous part of the clean up effort at the Fukushima Daiichi nuclear disaster site is days away.  Tokyo Electric Power Company (TEPCO) has permission to remove 400 tons of spent fuel rods from the rickety, damaged cooling pool above Unit Four, and it is scheduled to begin on Friday, 9 November.

In a speech in Tokyo last week prior to visiting the contaminated site, US Secretary of Energy Ernesto Moniz said, “the success of the cleanup also has global significance.  So we all have a direct interest in seeing that the next steps are taken well, efficiently and safely.”

Moniz came to Japan with an offer of unspecified US assistance, and TEPCO President Naomi Hirose accepted it. 

According to the Japanese Nuclear Regulation Authority, there are 1,533 spent and unused fuel rod bundles in the cooling pool that contain radiation equivalent to 14,000 times the amount released in the atomic bomb attack on Hiroshima in 1945.

To remove the rods, Tepco has erected a 273-ton mobile crane above the Unit Four building, which was left in a fragile state by hydrogen explosions that happened during the meltdowns two and a half years ago.

The stakes couldn’t be higher.  There are more than a few nuclear engineers worrying about the worst-case scenario: Spent fuel rods must be kept cool at all times.  If they’re exposed to open air, the zirconium alloy cladding will ignite, the rods will burn, and huge quantities of radiation will be emitted.  If the rods touch or fall into a pile on the ground, an open-air nuclear reaction is possible.

That’s the worst-case scenario.  On the other hand, everything might be all right.