Skip to comments.Fukushima nuclear plant operators prepare for dangerous procedure(spent fuel rods removal)
Posted on 10/27/2013 7:22:09 AM PDT by TigerLikesRooster
Fukushima nuclear plant operators prepare for dangerous procedure
Hundreds of radioactive rods must be removed at Fukushima without exposing them to air
PUBLISHED : Sunday, 27 October, 2013, 6:07am
UPDATED : Sunday, 27 October, 2013, 6:07am
Julian Ryall in Tokyo
The operator of the Fukushima Dai-ichi nuclear plant is making final preparations before starting the most delicate and dangerous procedure attempted at the plant since three reactors were wrecked in the March 2011 earthquake and tsunami.
Engineers from Tokyo Electric Power Co (Tepco) need to remove 1,533 rods of highly irradiated spent fuel from the damaged storage pool alongside the Number 4 reactor without exposing them to the air. The rods must then be carefully transported to a safer location for longer-term storage.
(Excerpt) Read more at scmp.com ...
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I don’t trust them removing one and they’re supposed to remove 1533 safely, snort, snort. Safe storage, snort again. If the Japanese mob is anything like the mob here, they’ll be scrimping on the building structure so just wait until the next quake, tsunami, hurricane, stupid human error, or a squirrel chews through a wire.
There’s the most beautiful dark red cardinal feeding outside my window. There won’t be too many left soon with TEPCO in charge.
What happens if they are exposed to the air?
Spent fuel rods are stored in water containing Boron, to absorb neutrons being emitted by the rods, to moderate any continuing reactions. Removing them from the water would allow reactions to increase, making the rods VERY HOT, and it would expose anything nearby to lethal doses of neutron and gamma radiation.
What would happen if you drilled a hole in the ground say 2000 feet deep and dropped the rods in the hole?
OK, these fuel rods “assemblies” are about 2x2x15 feet in size. They still have roughly 90% of their energy content remaining. Left to themselves, spewing out neutrons, they will want to continue the fission process, getting hotter and hotter. Bombarding other materials with neutrons “activates” them, turning them radioactive for some time (depending upon the material). You really, REALLY want to moderate these reactions with neutron absorbers (like Boron) until the fuel is stable enough for long term storage or re-processing (whenever that becomes legal). Dropping them down a hole not only puts them in an uncontrolled environment, it wastes 90% of the useful U235.
Are we in short supply of U235?
All the spent fuel entered this tank routinely. There are a LOT of spent fuel rods in this tank, of various vintages. Its adventures since the quake are less routine. It lost active cooling during the accident. However, IIRC, there turned out to be enough water to passively cool things by evaporation, without exposing any of the rods, until they were able to add water and jury rig cooling. I don't believe there has been any visible evidence of fuel damaged by over heating. The building was damaged by the hydrogen explosion. I'm not sure whether it was structurally damaged by the earthquake and tsunami earlier. Debris, including the fuel moving machinery fell into the pool. I don't know whether it damaged any of the fuel in falling. They've shorn up the tank, but I wouldn't trust it to last forever. If this spent fuel can make it to someplace structurally sound, that isn't in the middle of a disaster zone, Fukishima's future worst case scenarios look a lot better.
If things are no worse than we're told, physically removing the fuel from the tank should be a solvable engineering problem. Getting it to a new location is a different engineering problem, but at least problems there involve only small subsets of the larger problem each time. My concern is whether some of the spent fuel has spent enough time in the tank to be moved safely. IIRC reactor 4's entire core was put in the tank a few months before the accident. I presume they'll try to move the older stuff first.
I wonder if some of the rods are damaged. Because if not, they are already normally “moved” in a way that “exposes them to air” — they are lifted one at a time from the core, through the air, and over to the pond.
So I believe the issue is that in one of the explosions, or when the water level got too low, some of the rods melted enough that the surrounding casing isn’t intact, and that is why they need to keep them “covered”.
In any case, if they can get these moved, that will be one big headache less for them to worry about going forward. Several more though are big problems — keeping the containment vessels intact and cooled, and keeping the spent water from leaking all over the place.
There are certainly headaches to follow. But if they can’t handle this one it becomes hard to see how they can handle the final goals with the busted reactors. If they can handle this well it would provide some hope. Many could use some.