Work began last night (November 18 Japan time) in the defueling operation at Fukushima unit-4's spent fuel pool. A total of four 'new' (unused) fuel assemblies in the pool at the time of the 2011 disaster were transferred to a transfer cask designed to hold 22 assemblies. In this photo from TEPCO, you can see one assembly being moved into the cask by the new crane in the newly-built defueling 'building' over the original fueling floor pool after removal of dangerous and unstable building structure damaged in the original hydrogen explosion.
As you can see in the photo above, there are a number of human beings involved in the operation, close-up and uncomfortable. TEPCO had advertised that the crane would be operated by remote control from a shielded location, in case any of the fuel in the pool were to fall apart and initiate a fission reaction, but by starting with fuel that has never been irradiated, humans involved in the operation are [hopefully] not in immediate danger.
Here are some excerpts from various media sources about the operation [h/t ENEnews] -
BBC: "Overall, more than 1,500 assemblies must be removed in what correspondents describe as a risky and dangerous operation set to take a year."
WSJ: "The removal process - in which 1,533 assemblies holding spent and fresh fuel will be taken from a storage pool high atop reactor No. 4 and moved to a common pool serving all six of the plant's reactors - is a tricky one that's been the subject of a fair amount of concern globally, as well as some hyperventilation."
AFP: "Each rod contains uranium and a small amount of plutonium. If they are exposed to the air, for example if they are dropped by the grabber, they would start to heat up, a process that, left unchecked, could lead to a self-sustaining nuclear reaction - known as "criticality"."
AP: "TEPCO will remove the unused fuel rods first, and will then move on to the more radioactive spent fuel. At the very end it will remove three sets of rods that are slightly damaged. The storage pools in Units 1-4 contain a total of 80 sets of rods with slight damage, most of which occurred years ago."
[This "slight damage" includes one assembly holding 60-80 fuel rods that is bent at a 90º angle due to mishandling back in the early 1980s.]
NHK: "But bits of debris in the pool of the Number 4 reactor building could obstruct the work. The building was damaged by a hydrogen explosion in March, 2011. Workers may also find undetected damage to the fuel units. [...] The removal work requires extreme caution, as any damage to the units could release high-level radiation."
The Guardian: "The head of Japan's nuclear safety agency, Shunichi Tanaka, recently warned that removing the fuel involved huge risks, particularly if any attempt is made to force fuel assemblies that have become impeded by debris. "The process involves a very large risk potential," he said."
And just for some thought-food, here's what Janette Sherman, M.D. [internal medicine and toxicology, worked for AEC and U.S. Navy Radiation Defense Laboratory) had to say about it in a November 4th interview with Harvey Wasserman [9:00 in]...
Of course it's going to have an impact on our health. It's not just Alaska, it's already been detected off the coast of California [...] All of this is done without informed consent. And so when you go back to John Gofman, we know that this is random murder, because we don't know who's going to be contaminated [...] We have the Northern Hemisphere essentially being subjected to a massive experiment.
I understand that a good many nuclear supporters here and elsewhere consider Harvey to be hyperbolic on the subject of nukes, and I actually agree with that - he indeed can be hyperbolic on occasion. Some are also suspicious of Dr. Sherman, and even John Gofman [died 2007], though their credentials on the subject of radioactivity and its damage to biological tissues are impeccable. This is standard operating procedure for pro-nuclear apologists, as "attacking the messenger" is their only line of defense against a reality they simply cannot afford to acknowledge.
Let us all wish TEPCO well with this year-long operation. It must be done due to the increasing instability of the unit-4 ruins and the constant seismic activity of this region of northeastern Japan. Defueling the other three destroyed reactor plant spent fuel pools probably won't be this 'easy', but the engineers will get some good experience for when the time comes. Those units are far too radioactive for this kind of operation at this time, it may be decades before it can be done. If their pools do not fall in any of the predictable 7.0+ earthquakes predicted to occur in the area within the next half-century.
Good luck to all of us.