It seems TEPCO are pretty sure that the fuel rods have melted out of the reactor pressure vessel in the Fukushima Reactor #1. It probably happened pretty soon after the march 11 Tsunami. No further information on how far the material escaped as of now…
I always figured the world’s first confirmed core meltdown in a commercial nuclear power plant would get more airplay, but the Fukushima debacle’s been one slowmotion train wreck, so maybe the networks figure it’s yesterdays news?
I didn’t know where to post this - but I’m sure there’s potential for outrage from our Japanese posters.
What does this news change? There have already been zones of exclusion set and changed due to the radiation readings.
That there is a possibility that the readings are due to a possible meltdown that has escaped the vessel rather than a possible meltdown that is contained in the vessel doesn’t really seem to matter. I think we all knew that this is a major disaster either way.
The news that the fuel rods may have disintegrated and dropped to the bottom of the reactor pressure vessel doesn’t change much. The news that the reactor pressure vessel isn’t holding water makes the problem of restoring circulating cooling that much harder, although TEPCO have been proposing to flood the entire reactor no. 1 drywell (the concrete containment that itself contains the reactor pressure vessel) since early May. That will ensure that the core becomes submerged again, and perhaps recirculating cooling will be established into the drywell itself.
The amount of core damage affects how much fission product enters the air/water surrounding the fuel. If the fuel rods remain as rods, with their zirconium claddings intact, iodine and caesium do not escape. If the rods have melted, overheated and split their claddings or whatever, iodine and caesium contaminate the water being continuously injected into the reactor pressure vessel. That water has been ending up in the turbine halls and some of it has leaked into pipe trenches and into the sea. TEPCO are pumping radioactive water into storage and blocking water leaks as they find them, but until recirculating cooling is established at the reactors, contaminated water will continue to be generated.
Whether the fuel rods actually melted, or whether they deformed from overheating and split their claddings, or whether they got so hot that their claddings oxidised and fell apart allowing all the little uranium oxide pellets to spill out, is kind of academic but the press loves the word “meltdown”.
It doesn’t make things any worse really, although it may affect TEPCO’s timeline for bringing everything under control. As more access to the reactor buildings becomes established, the exact detail of the damage will come out bit by bit and the press will have some fun spinning it up.
It is known to be leaking, and you are right…it’s not really news, since they suspected a partial meltdown as far back as March. The temperatures seem to pretty much be under control, the melted fuel rods aren’t eating through the containment vessel on the way to where is the opposite side of the earth from Fukushima, and they know about the leaks and are taking steps. Like Matt said, it might push back the time lines on bringing the situation fully under control (though it might not, too), but it’s really not news, just confirmation, and it doesn’t suddenly change what’s happening there, except in the minds (such as they are) of the anti-nuclear hysterics.
Is that confirmed - that fuel hasn’t escaped the containment vessel, or isn’t about to?
I’m not saying that it’s confirmed that it has either, nor trying to argue the plausibility of “China Syndrome” style nuclear terror.
This is my understanding of what’s being reported:
They are pretty sure the fuel pellets escaped the fuel rods and ended up at the bottom of the pressure vessel.
They strongly suspect the fuel then melted through and escaped the pressure vessel, which is why the temperature in the pressure vessel is not very high any more.
Where the escaped fuel is at the moment is not known. I.e. it being contained by drywell or wetwell may be likely, but they don’t in fact know at the moment.
AFAIK 2) is in fact new information, and was not until now suspected for Fukushima 1, Reactor 1?
I’ve learned previously that there’s really no consensus on exactly what a “nuclear meltdown” is supposed to denote, and neither is there an industry definition of the term, so I guess using it in the OP was a case of poisoning the well. My apologies.
But from a safety perspective, fissile materials reaching criticality and escaping into the environment because the emitted heat damaging the containment structures in place, is one of the worst case scenarios in a nuclear plant isn’t it? I mean, that’s the reason for having drywells and/or wetwells as containment measures?
No one has been inside, if that’s what you are asking. But, going from memory, the temperatures in the containment vessel are only around 100C, including at the bottom…and the bottom is where whatever water is getting into the containment vessel is in the best position to cool. There are leaks, but they aren’t major leaks, and again from what I recall, the leaks are in fittings and connections, not huge gaping holes in the sides or bottom.
There was never a case were there was no coolant in the containment vessel, or that the core was fully exposed for long periods of time…and IIRC they had put the core into shutdown mode (i.e. they had the control rods in). It was the residual heat that was a problem. From what I read what seems to have happened fairly early on is that part of the core became exposed, then sea water was poured on the still hot and now exposed parts of the core, which made it very brittle. Parts of that shattered and fell into the bottom of the containment vessel…which is what it’s designed to have happen.
A ‘China Syndrome’ is when the core has it’s control rods fully removed, runs out of coolants, melts down at extremely hot temperatures, and eventually eats it’s way out of the containment vessel. Temp wouldn’t be hundreds of degrees C but thousands to do that.
The fuel rods became brittle and some of them shattered…the fragments are indeed at the bottom of the containment vessel, yes…at least that’s how I understood this when they were explaining it in March as a possible and likely scenario of what was happening.
No…as far as I know, no one thinks this. The temperatures never got that high. My understanding is that the hydrogen explosions in the secondary containment building might have damaged the pressure vessel and caused leaks in thinks like the fittings (the stuff they use to bring water and other stuff into and out of the containment vessel). If you have a cite from a reputable source saying that the fuel ate it’s way through the containment vessel that would be news to me…and I should think that the leaking would be much worse, and the temperatures much higher. Think about it for a moment…if there is a hole or breach along the sides of the containment vessel then some water is still going to be inside, and the temps are going to be high but under control. If their is a big hold at the bottom of the vessel, then most of the water is going to leak out, and that’s going to expose whatever is left of the core, causing high heat. The last time I was following all of this they were talking temperatures of around 100 degrees C…that’s not very high.
Again, that would be news to me. The only thing I’ve heard of that escaped was contaminated water. I can see how the core could melt through the bottom of the containment vessel and the situation be as described. If the core was eating it’s way out of the containment vessel or had already done so then it would be a much bigger deal than they seem to be making it…and reactor 1 would be completely out of control. A quick look at the news doesn’t seem to back this up, and looking at the IAEA website, they aren’t even bothering to update it since May 5th…so, I’m a bit skeptical that things are so out of control and no one is paying attention.
AFAICT, the ‘new’ information is simply confirmation that the core partially melted down early on in the crisis, and part of the fragmented core and fragmented fuel rods are in the bottom of the containment vessel. But it’s not a major issue, since they are getting water into it, even if some of that water is leaking out…and, of course, that water is contaminated, so they have a mess on their hands and it’s difficult to get people into those areas to work on it because of that.
Paul Gunter is on TV explaining that building 1 had a core meltdown and is exuding through the floor.
Building 4 is leaning badly and may fall. It holds over 100 tons of nuclear waste.
There is 90,000 tons of highly radioactive water they have to deal with. Seaweed 40 miles off the coast is highly radioactive.
I guess there are no problems anymore. http://www.beyondnuclear.org/storage/Paul_Gunter_bio.pdf
Rereading it - and your response xtisme - I think I understated the ambiguity of his statements and conflated what was on the record and what I read between the lines from the statements of Matsumoto somewhat.
Still, statements like this:
“The fuel pellets likely melted and fell, and in the process may have damaged…the pressure vessel itself and created a hole”
To me sounds like a convoluted way of saying that they suspect that the fuel pellets were gathered at the bottom of the pressure vessel and subsequently melted out of the vessel.
Those pressure vessels are pretty massive things, Occam’s tells me it wasnt just falling pebbles that made it crack…
Note that Matsumoto also says it’s “likely” that the fuel rods were at one point completely exposed to air. So that sounded to me basically like conceding that fuel probably escaped the pressure vessel through melting, and that they don’t know for sure where it went as of right now.
That is not what the article said, it said that the melted fuel is on the bottom of the containment vessel, which is still presumably containing the now melted/deformed fuel rods, as it is supposed to. There is water leaking out of it, but that’s not the same thing.
Again, the material has not “escaped” - the fuel may be in a disorganized heap, but it is still presumably within the containment vessel.
Please check your facts - Three Mile Island was the “first confirmed core meltdown in a commercial nuclear power plant”, although it was “only” a partial meltdown and not a complete one.