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[The_Cow]

OK, been watching this very closely out of all the events so far in Japan over the past few days mainly as I have friends who work in the UK nuclear fuel industry and have had an avid interest since I was a child on the events at Chernobyl, Three Mile Island, etc...

What's troubling me at the moment is that reactor number 3 (of which recently had a hydrogen explosion I believe) has recently switched to MOX fuel (it switched in September 2010 from standard Uranium).

MOX is much more potent as it's a fuel composed of a mixture of plutonium dioxide and uranium dioxide; thus meaning it's much more active and a result of this is that it generates much more residual heat.

A meltdown of a reactor running MOX charged rods (around 80 tonnes or so of the stuff) would be seriously catastrophic; anyone else got any more info/input on this?

[m8internet]

Don't worry about it, the reactors are slowly cooling
Any further radioactive releases are simply the coolant discharges which have become irradiated

If there was going to be a "meltdown" it would have occured in the first 48 hours
Personally, I wish the media would stop using the term "meltdown" and use the more correct term "post-reactive gas explosion"

[The_Cow]

Originally Posted by m8internet

Don't worry about it, the reactors are slowly cooling
Any further radioactive releases are simply the coolant discharges which have become irradiated

If there was going to be a "meltdown" it would have occurred in the first 48 hours
Personally, I wish the media would stop using the term "meltdown" and use the more correct term "post-reactive gas explosion"

Though, the fuel has started to partially melt-down due to them not being able to bring the water levels back up; hence the hydrogen being produced and the build up's we saw which blew the roof's off the two reactor housings.

The rods melt at 2,200 C whereas steel (which contains the reactor) melts at 1,500 C, the water flowing round is however working (though we don't know how well) at stopping a full "meltdown" occurring.

A partial meltdown is however only what occurred at Three Mile Island.

Correct me if I'm wrong, I'm recalling some specifics from I've read off a few sites though mainly from World Nuclear News.

[The_Cow]

Ah, this better explains how the Hydrogen was created:

The core in unit 1 heated up to the extent that some of of the zirconium cladding the fuel oxidized in water, releasing hydrogen gas. The gas was vented into the secondary containment building, where it combined with oxygen to create an explosion, blowing apart part of the secondary containment building.

[NelsonT]

Three reactors there got explosions, and Toyko radiation levels raised. Watching the translation from NHK very closely.

My city is 2500km away from Fukushima Daiichi nuclear plant. There are 3 nuclear plants operating now in the island I lived. The event will change our thinking to nuclear power station.

[x86brandon]

I hate to say it, but to me, this makes me feel better about nuclear power. Think about all the abuse that plant has been taking and it's still ticking, sort of. The odds of that sort of chain of events happening is pretty slim, so to me, it's a testament to the engineering to take a 9.0, then tsunami, followed by record aftershocks, etc.

[viGeek]

The Daiichi plants reached end-of-life recently and was scheduled to be decommissioned in several months, these are GE BWR (Generation II afaik) reactors from the 1960s. So that is probably playing a factor here.

It appears now we are going to be pulling a page from the Chernobyl playbook (not a good sign) using helicopters to drop water/boron to cool the reactor. The majority of the helicopter pilots from the Chernobyl incident died from acute radiation poisoning.

These reactors are designed to have a variety of defenses (defense in depth), the fuel is surrounded by ceramics, which are surrounded by the metal rods, which are surrounded by the reactor vessel, which are surrounded by the containment vessel.

My guess is that at this point, the ceramic is gone, the metal rod is gone, we have confirmation the containment vessel buildings were compromised.

It's going to come down to the reactor vessel itself, whether or not that has been jeopardized is the key question, if it has been significantly ruptured you're looking at wide spread release assuming there is no water surrounding.

I don't think we are looking at anything remotely close to Chernobyl, those reactors were Russian RBMK types which did not have a containment vessel. In addition the reactor itself was blown to pieces.