>The system still has a fallback system in the event of a core meltdown that is designed to cool and manage the core without radiation release.
What do you think is failing and is the entire cause for all of this concern. The fallback system is pumping water into the reactor to keep it cool. Those are the systems that have been failing and have failed (during the explosions/fires) and have caused the (temporary-ish) meltdowns in the last few days.
A full meltdown has the potential to release a significant amount of radiation. A full meltdown increases in possibility as the reactors become harder to control and cool due to explosions and containment failure. It probably doesn't pose a significant risk to CA, but they will receive some radiation if it were actually to experience complete failure.
Meltdown isn't binary. They're experiencing meltdown right now. By definition. That's what the release of radioactive material is. The question is, can they keep it under relative control and prevent further exposure of the still proceeding fuel rods.
They're experiencing meltdown right now. By definition. That's what the release of radioactive material is.
Not really; in this case "meltdown" refers to the actual process of core melting, it is not entirely clear but it does not appear much or any of the cores have melted. Certainly not to the stage I would refer to as a meltdown. They are still in a "struggling to cool it down" stage.
The release of radioactive material is not equatable to a meltdown - all manner of things can lead to such a release, meltdown is just one of them.
If they actually have a full core melt (to the point it drops out of the reactor vessel into the dry well), yes, the risk of release of radioactive material is heightened. But probably not to the level you envision, and it is certainly not a case of "if it melts it's game over".
Explosions within the reactor shell are extremely unlikely, even in the event of a core meltdown, because the system is specifically designed to stop such an event occurring (which is one reason it has not so far happened :)).
Note; containment failure has not occurred, as far as we know, at any stage. The reactors are not being "controlled", the process is stopping by itself. The reactors simply have to be kept cool while that happens.
What do you think is failing and is the entire cause for all of this concern.
There is a different system in such a case (or, rather, a different approach). Essentially they just flood it with water.
With the best will in the world; it is worth reading some of the more technical explanations rather than just the media. They explain the process and the issues much better - even Wikipedia has reasonable material (and is at least a place to start with links)
This is now the second time you've accused me of not knowing what I'm talking about and yet your only difference of opinion is my terminology as to whether it's a meltdown or whether the process of "oh shit, dump water on it" is controlled or not. In fact, most of the information I have on this topic was from spending most of Sunday re-reading Wikipedia on nuclear reactors, but thanks for assuming I watch or read ANY mainstream news.
QUOTE: "A meltdown occurs when a severe failure of a nuclear power plant system prevents proper cooling of the reactor core, to the extent that the nuclear fuel assemblies overheat and melt, either partially or completely"
That has occurred. That's not in dispute, unless I'm just completely 100% off base here. A quick Google search reveals that fuel rods in both reactors were not only uncovered by water at various points, but were also "exposed" which I presume to be through a containment failure, AND there are numerous reports that the parts of the rods have in fact melted.
As I said earlier, this constitutes a meltdown and greatly increases the severity and danger of the problem at hand. It's not a total meltdown, I already "disclaimered" that repeatedly. Those rods melting pose a large risk to containment efforts. If they melt, they can escape much more easily and that means radiation exposure on a much greater level, even if only for workers at the plant.
I don't mean to sound patronising or rude, if that is what came across sorry.
Whilst mostly you're correct, there are some fundamental problems with what you are saying.
It's definitely stretching the definition of a meltdown to refer to this event as such. It's still pretty much unknown if any melting has occurred, and to what extent it has done. Generally a meltdown is as I described it; where the situation is unrecoverable with the standard cooling and you are facing the situation of simple containment.
I suppose technically this could be seen as a partial meltdown; but the truth is that this situation is at the very edge of the margin for such a problem. A meltdown is not a binary thing, but in this case it is not really a meltdown, and that was my main point.
Right now it is absolutely recoverable, and based on the latest data #1 and #3 reactors will be fine from this point on. Certainly if they survive the next couple of days it will all be fine.
but were also "exposed" which I presume to be through a containment failure
No. If this were the case there would be a much serious issue :) It simply means the coolant level dropped so far that they were exposed to the air inside the container.
If they melt, they can escape much more easily and that means radiation exposure on a much greater level, even if only for workers at the plant.
Potentially... but bear in mind that radiation expulsion so far is relatively unrelated to the core; the radiation released so far is included in the steam that is being vented (and then the explosions push it right out). In a proper meltdown situation the risk is that an explosion releases actual core material into the wild, that would be a magnitude worse than the current situation.
At the moment I don't believe the rods are melting, they are being successfully cooled (and for the most part have been).
I don't know, maybe you're right but I continue to see, more and more, evidence that they did melt. I continue to see more and more people placing this between TMI and Chernobyl in severity...
What do you think is failing and is the entire cause for all of this concern. The fallback system is pumping water into the reactor to keep it cool. Those are the systems that have been failing and have failed (during the explosions/fires) and have caused the (temporary-ish) meltdowns in the last few days.
A full meltdown has the potential to release a significant amount of radiation. A full meltdown increases in possibility as the reactors become harder to control and cool due to explosions and containment failure. It probably doesn't pose a significant risk to CA, but they will receive some radiation if it were actually to experience complete failure.
Meltdown isn't binary. They're experiencing meltdown right now. By definition. That's what the release of radioactive material is. The question is, can they keep it under relative control and prevent further exposure of the still proceeding fuel rods.