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I have been thinking about the low water level in the reactor cores (below the top of the fuel rods), but realised I don't even know if and how any water gets in there. What they flooded with seawater is supposed to be the containment around the pressure vessel (the drywell), isn't it? Does anyone remember details on this?

*Lunatic*, n.
One whose delusions are out of fashion.
by DoDo on Fri Apr 1st, 2011 at 01:43:31 AM EST
In this video presentation a former Fukushima Daiichi No4 engineer explains the data and circumstances that point to a "Loss of Coolant" accident at the No 1 reactors (and perhaps No 2 and 3 as well), which is the worst scenario of meltdown after all the water gone. Around the 52:00 mark he mentions the problem of getting the water into an affected reactor. It seems, there is no solution given leaked pipes.

By the way, here is an an interesting Youtube video about the cleanup of the meltdown Three Miles reactor.

by das monde on Fri Apr 1st, 2011 at 04:30:59 AM EST
[ Parent ]
Trying to answer my own question, I again checked the Mathias Braun/Areva presentation. On slide 17, I found something of relevance: it says that the fuel rods won't yet melt if they are half out of water only, they will do so 2/3 exposed (when cladding temperature reaches up to 900°C), and the temperature for zirconium reaction with steam is reached when 3/4 exposed.

The fuel rods are 4 m high, and currently 1.5 to 2.3 m out of water. (The 2.3 m reading is from No. 3, but the second meter in the same core indicates 1.9 m, so I guess one of these meters is damaged and unreliable, too.)

Regarding seawater injection, slide 25 says it was into the pressure vessels, but Mr. Braun is uncertain about the flooding of the surrounding containment (apart from No. 1), and the drawing shows complete fuel rod coverage, so I guess he didn't have enough info himself.

*Lunatic*, n.
One whose delusions are out of fashion.

by DoDo on Fri Apr 1st, 2011 at 04:37:16 AM EST
[ Parent ]

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