You already know that Fukushima’s fuel pool number 4 may be the single greatest threat, but that pool number 3 is very dangerous as well.

You’ve heard that unit 3’s fuel pool contains less radioactive material than unit 4 . . . but still a tremendous amount of radiation. Scientific American reported last year:

The pools at each reactor are thought to have contained the following amounts of spent fuel, according to The Mainichi Daily News:

• Reactor No. 1: 50 tons of nuclear fuel
• Reactor No. 2: 81 tons
• Reactor No. 3: 88 tons
• Reactor No. 4: 135 tons
• Reactor No. 5: 142 tons
• Reactor No. 6: 151 tons
• Also, a separate ground-level fuel pool contains 1,097 tons of fuel; and some 70 tons of nuclear materials are kept on the grounds in dry storage.

You’ve learned that unit 3’s reactor was the only one at Fukushima which burned plutonium. As Japan Times notes:

Reactor 3 . . . uses highly dangerous mixed oxide fuel, Tokyo Electric has reported.
***
No. 3 reactor is the only one at the crippled power station that was powered by the plutonium-uranium MOX

You’ve gotten the fact that – if the water drains out for any reason – it will cause a fire in the fuel rods, as the zirconium metal jacket on the outside of the fuel rods could very well catch fire within hours or days after being exposed to air. See this, this, this and this. (And that even a large solar flare could knock out the water-circulation systems for the pools.)

You’ve listened to experts say that – unless the rods are removed from the fuel pools before a major earthquake strikes (using special equipment which keeps the rods submerged in water the whole time) – they will likely catch fire and release huge amounts of radioactivity. See this and this – starting at 4 minutes into the video.

You’ve read that – after reviewing photos from several different angles – the Nuclear Regulatory Commission’s initial impressions were that spent fuel pool number 3 might not be there at all, and that nuclear engineer Arnie Gundersen said a couple of days ago:

Unit 3 is worse [than No. 4]. It’s mechanically, it’s rubble, the pool is rubble. It’s got less fuel in it. It faces the same problem. Structurally the pool has been dramatically weakened. And, god, nobody has even gotten near it yet.

And you may have caught the recent headline that a 35-ton machine fell into Unit Three's spent fuel pool. As Kyodo News reports:

The operator of the crippled Fukushima Daiichi nuclear power plant on Friday found that a 35-ton machine had dropped inside the spent fuel pool of the No. 3 unit, possibly because of a hydrogen explosion that occurred in the early stage of plant’s nuclear accident last year.

Tokyo Electric Power Co., commonly known as TEPCO, reported the finding after placing a camera inside the water-filled pool the same day to prepare for removing, as part of the decommissioning process, the nuclear fuel stored there.

One photo showed part of the machine, originally located above the pool and used to insert and remove fuel, appeared to have dropped onto the nuclear fuel storage racks.

But – until you see pictures – it is hard to get a sense of what all this means.

Here’s a picture just released by Tepco of the giant machine in the fuel pool:

And another new Tepco photo showing other tangled wreckage inside the pool:

The following graphics from Ashai news show how the crane is normally used to move spent fuel rods in and out of the pool. Here’s the crane bringing in a special container to hold the rods:

Loading spent fuel rods into the container:

The crane then lifts the rod-carrying container up:

And then away from the pool:

Keep in mind that the machine which fell into pool number 3 was part of the crane “used to insert and remove fuel”, and so now there is no easy way to remove the fuel from the fuel pool. And the crane at unit 4 is also broken:

Still confused?

Let’s look at some more pictures . . .

Before the Quake

Here is where the fuel pools are located in the Fukushima reactors:

Here are pictures [see http://www.houseoffoust.com/fukushima/fukushima.html] Unit 3’s fuel pool before the earthquake, and the fuel pool crane:

This picture, taken on August 21, 2010, shows a MOX spent fuel storage pool inside TEPCO's Fukushima No.1 plant third reactor building at Okuma town, Futaba district in Fukushima prefecture with the reactor situated behind the pool. AFP PHOTO / JIJI PRESS (Newscom TagID: afplivethree804521) [Photo via Newscom] Copy is from http://josephmiller.typepad.com/battle-to-stabilize-the-f/2011/03/

This image shows workers lowering a spent fuel assembly into a spent fuel storage pool. It is not clear that this is an image of the spent fuel pool at Fukushima Reactor 3. Copy is from http://josephmiller.typepad.com/battle-to-stabilize-the-f/2011/03/

Plutonium-uranium mixed oxide (MOX) fuel rods are placed in a storage pool at the No. 3 reactor of the Fukushima Daiichi nuclear power plant in Fukushima Prefecture, northern Japan, in this picture taken August 21, 2010. Copy is from http://cryptome.org/eyeball/daiichi-npp6/daiichi-photos6.htm

The image below is during repairs at reactor 4 before the earthquake – but gives a sense of scale [See also: 2002 photograph]:

After the Quake

Here is the green fuel pool crane at unit 4 after the earthquake:

12 November 2011

12 November 2011

12 November 2011

The view from above the crane at fuel pool 4:

24 March 2011

16 March 2011

24 March 2011

(“SFP” in these photos refers to the spent fuel pool.)

Former fuel pool nuclear engineer Arnie Gundersen notes that – for at least some period after the earthquake – the fuel pool had insufficient water, and the nuclear rods were sticking out into the air.

New Images Reveal Nuclear Fuel Rack Exposed to Air
from Fairewinds Energy Education on Vimeo.
See also: Text Transcript of Video

Here is water later being poured into fuel pool 4:

22 March 2011

Reactor 3 is a mess:

HouseofOust notes of this picture:

Oval is the reactor well location. Lines on the left side of the image outline the crane that seems to have fallen over or been crushed. Spent fuel pool outlined in the foreground.

And of this picture:

Perspective lines are drawn to show where the deck should be and how much is gone. A circle shows the beam apex to appoximate the reactor well. Spent fuel pool is again seen off to the right and outlined. Marked structure in the foreground is the end of the refueling crane.

Now can you see what’s going on?

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